Flowable Composites

Flowable Composites

It has become popular to routinely place a flowable composite (e.g., Filtek Flow, Flow-It ALC, Tetric Flow, Revolution Formula 2) on the pulpal floor and axial wall of a Class II preparation prior to restoring the tooth with a packable resin composite (e.g., Pyramid, SureFil, Solitaire 2, Prodigy Condensable).¹ In fact, some manufacturers of packable and flowable composites include recommendations in their instructions to do so. Clinicians usually place a flowable liner because it reduces the bulk of packable composite that has to be placed. This makes it easier and less time consuming to restore the tooth. Others believe it helps reduce leakage at the tooth/resin interface because the liner is flexible and absorbs some of the packable composite's shrinkage as it cures. This, at least theoretically, may result in a better bond between the resin and tooth with little or no gap being formed. There is some evidence supporting this theory.^2,3 Finally, some users place a flowable because it contains fluoride, and they believe that the fluoride release will have a anti-cariogenic effect.

If you routinely place a flowable composite as a liner before restoring a tooth with a resin composite, be it a microhybrid or packable, you should be aware of some precautions to take. First, the flowables are essentially "thinned down" composite resins, which accounts for their appealing characteristic of easy placement. The thinning down process is accomplished, at least in part, by incorporating fewer filler particles into the resin. As a result, physical properties such as strength and resistance to fracture are lower. So we should be mindful of the need to place a flowable in a relatively thin layer. Also, a study published a few years ago found that a number of then currently-available flowable composites lacked a sufficient degree of radiopacity.⁴ This means that on radiograph the flowable would appear as a thin, radiolucent line extending from the margin to the axial wall. Without a well-documented record, a clinician could misinterpret this as caries, possibly secondary to microleakage. Unfortunately, cases have been reported where the otherwise acceptable resin composite restoration has been removed only to find that the radiolucent "line" was a non-radiopaque flowable resin.

Perhaps the best reason for using a flowable resin as a liner beneath a packable composite is to make it easier to pack the composite into the preparation. Packables are thick, and it can be difficult to place them in a preparation (especially one that is irregular with undercuts) without producing voids. By placing a flowable resin liner into areas of the preparation that are difficult to access, the potential for producing voids is reduced.

The bottom line is not that we shouldn't use flowable resins as liners, but that we need to be aware of their limitations, so that we choose the right flowable product and use it sparingly so that its lesser physical properties do not compromise the clinical success of the packable resin restoration.

To Bond Or not to Bond Amalgam

Multiple laboratory studies have found definite advantages for bonded amalgam restorations including increased retention,¹ fracture resistance,^2,3 and marginal seal.⁴ Staninec found that the use of adhesives provided greater retention than grooves or dovetails.¹ Oliveira and others found improved fracture resistance in large MOD preparations when bonding amalgam compared to the use of Copalite alone.² A study by Burgess and others found no difference in the strength of complex amalgam restorations using four TMS pins or bonding, but the combination of the two significantly increased the forces necessary for fracture.³ Studies have also shown increased retention of amalgam when bonding with resins containing filler particles.⁵ The more viscous bonding agent may improve penetration into the amalgam during condensation.⁶ Also, research has shown a reinforcement of remaining tooth structure with bonded amalgam restorations.⁷ However, the ability to maintain this reinforcement over time remains equivocal with some studies showing no increase in fracture resistance after aging and thermocycling.^8,9 The use of an adhesive agent under amalgam has been shown in laboratory studies to decrease microleakage.⁴ Again, the long-term significance of this decrease is unknown.

Most of the clinical studies have found no decrease in post-operative sensitivity^10,11 and no difference in the performance of bonded amalgam restorations compared with traditional mechanically-retained restorations.^6,12 Contrary to popular belief, the preponderance of clinical investigations has demonstrated no difference in sensitivity reported by patients receiving amalgam restorations with or without resin adhesives.^10,11 Summitt and others published a clinical study comparing the performance of bonded versus pin-retained complex amalgam restorations and found no difference after five years between the two techniques. They concluded that bonding with a filled bonding resin (Amalgabond Plus, Parkell Inc., Farmingdale, NY) was a satisfactory method of retaining large amalgam restorations replacing entire cusps.⁶ So, should you place an adhesive agent under all of your amalgam restorations? Given the added cost, time and technique sensitivity of using adhesive liners, there appears to be no clinically-demonstrated benefit in bonding conventional preparations which contain customary retentive features.¹³ However, given the advantages of increased retention, strength and marginal seal found in laboratory studies, the bonding of amalgam may be justified adjunctively with traditional mechanical retention in large restorations replacing a cusp, when tooth structure may need some reinforcement, and for crown foundations.

What are the Benefits of Pre procedural mouth rinsing?

Pre-procedural mouth rinsing is the use of an antimicrobial mouth rinse by the patient before a dental procedure. Its objective is to reduce the number of oral microorganisms that may be released as an aerosol or spatter from a patient's mouth during dental care that subsequently contaminate equipment, operatory surfaces, and dental healthcare personnel.

A visible spray is created during the use of rotary dental and surgical instruments (e.g., handpieces, ultrasonic scalers) and air-water syringes. This spray contains, primarily, large-particle spatter of water, saliva, blood, microorganisms, and other debris. Spatter travels only a short distance and settles out quickly, landing either on the floor, nearby equipment and operatory surfaces, the dental healthcare personnel providing care, or the patient. The spray may also contain some aerosol. Aerosols take considerable energy to generate, consist of particles less than 10 microns in diameter, and are not typically visible to the naked eye. Aerosols can remain airborne for extended periods of time and may be inhaled; they should not be confused with the large-particle spatter that makes up the bulk of the spray from handpieces and ultrasonic scalers. Appropriate use of dental dams, high-velocity air evacuation, and proper patient positioning should minimize the formation of droplets, spatter, and aerosols during patient treatment.

To date, no scientific evidence supports the claim that pre-procedural mouth rinsing actually prevents disease transmission in the dental operatory, but studies have shown that a pre-procedural rinse with a product containing an antimicrobial agent (e.g., chlorhexidine gluconate, essential oils, povidone iodine) can reduce the level of oral microorganisms generated when performing routine dental procedures with rotary instruments. Pre-procedural mouth rinses may be most beneficial before a prophylaxis using a prophylaxis cup or ultrasonic scaler since rubber dams cannot be used to minimize aerosol and spatter generation, and unless the provider has an assistant, high-volume evacuation is not commonly used

What are Giomers

Giomers are a relatively new type of restorative material. The name "giomer" is a hybrid of the words "glass ionomer" and "composite", which pretty well describes what a giomer is claimed to be. Although glass-ionomer restorative materials such as Ketac-Fil (3M ESPE) and Fuji Type II (GC America) have some very important properties, such as fluoride release, fluoride rechargeability, and chemical bonding to tooth structure, they also have well-known shortcomings. Their esthetics, for example, are less than ideal and make them a poor second choice to resin composites for restoring esthetically-demanding areas. Also, they are sensitive to moisture contamination and desiccation, which can present the clinician with challenges during their placement. In the 1990s manufacturers improved these shortcomings by adding resins to glass ionomers to produce resin-modified glass ionomers. These products (e.g., Fuji II LC, GC America; Vitremer, 3M ESPE; Photac-Fil Quick, 3M ESPE) have much better esthetics and handling characteristics than glass ionomers. Importantly, they also retain many of the glass ionomer's beneficial properties, such as long-term fluoride release and the ability to be recharged with topically-applied fluoride. They tend, however, to discolor over time. In another attempt to "better" the glass ionomer restorative materials, compomers were also developed. They were touted as being similar to glass ionomers but having much better esthetics and being easier to place and polish. Unfortunately, some of the manufacturer's claims were not confirmed by published research. Although they handled better than GICs, they released much less fluoride and could not be recharged.

In the continuing quest for improved glass ionomer-like restoratives, manufacturers have developed and introduced a new class of materials called "giomers." As noted earlier, the term implies they are combinations of glass ionomers and composites. Their manufacturers claim they have properties of both glass ionomers (fluoride release, fluoride recharge) and resin composites (excellent esthetics, easy polishability, biocompatibility). Giomers are distinguished by the fact that, while they are resin-based, they contain pre-reacted glass-ionomer (PRG) particles. The particles are made of fluorosilicate glass that has been reacted with polyacrylic acid prior to being incorporated into the resin. The pre-reaction can involve only the surface of the glass particles (called surface pre-reacted glass ionomer or S-PRG) or almost the entire particle (termed fully pre-reacted glass ionomer or F-PRG). Giomers are similar to compomers and resin composites in being light activated and requiring the use of a bonding agent to adhere to tooth structure. Only one giomer is commercially available at the time of this writing, Shofu's Beautiful, (see at right) which uses the S-PRG technology. According to Shofu, Beautiful is indicated for restoring Class I through V lesions as well as for treating cervical erosion lesions and root caries. It is available in 13 shades and is supplied in syringes.

Little published research is available on the properties or performance of giomers. One recently published study compared the fluoride release of a glass ionomer, a resin-modified glass ionomer, a giomer, and a compomer. It found that while the giomer released fluoride, it did not have an initial "burst" type of release like glass ionomers, and its long-term (i.e., 28-day) release was lower than that of the other materials.¹ Another study found that a giomer, after polishing with Sof-Lex disks, had a smoother surface than a glass ionomer, and one that was comparable to that of a compomer and a resin composite.² A three-year clinical study comparing the performance of a giomer with that of a microfill resin composite in Class V erosion/abrasion/abfraction lesions has also been done. After measuring eight performance characteristics, no significant differences between the two materials were found.³

Almost assuredly, many other giomer products will become available in the future.

Brushing Right After Drinking Soda(cola, pepsi, mirinda etc) May Harm Teeth

BERLIN (Reuters Health) - If you rush to brush your teeth right after drinking soda (aerated cold drinks), think again. Doing so may actually do more harm than good, and it's better to wait 30 or 60 minutes before brushing, according to new research.

Because carbonated drinks are highly acidic and have the potential to damage a tooth's enamel, dentists at Goettingen University, Germany, conducted a study to determine the best time to brush after drinking such beverages. They found that later -- rather than immediate -- brushing is between three and five times more effective at protecting enamel from the erosive effects of carbonated drinks.

In the study, 11 volunteers wore a sterilized piece of tooth-like material in a removable prosthesis for three weeks. This was removed in the mornings and evenings and soaked for 90 seconds in a liquid similar in acidity to soda.

Afterward, the prosthesis was brushed using an electric toothbrush at different times after the 'drink.' Three weeks later, the researchers measured the thickness of the enamel to see how much damage had been inflicted on the 'tooth.'

Professor Thomas Attin, director of the university's department for tooth protection, preventative dentistry and periodontology, said, "The loss of material was less when the participants waited with cleaning for between 30 and 60 minutes."

Professor Attin presented the research at the annual meeting of the German Association for Tooth Protection, where it was awarded a prize from chewing gum firm Wrigley.

He said tooth enamel appears to suffer less damage when brushing occurs after the tooth has had time to mount its own defence against acidic erosion.

Acidic substances attack tooth enamel, he said, and upper layers of the tooth can even be dissolved in some acidic drinks. However, protective agents in saliva may help repair and rebuild damaged tooth enamel.

Waiting for a while seems to give the teeth a chance to rebuild, the researchers said, while immediate cleaning of such teeth can increase the damage by literally brushing off the affected layers.

Gum disease raises death risk in diabetics: study

NEW YORK (Reuters Health) - Severe gum disease may hasten death in people with diabetes, new study findings suggest.

"Diabetic people with periodontal disease had increased death rates due to cardiovascular disease and renal (kidney) failure, which are two major complications of type 2 diabetes," said study author Dr. William C. Knowler.

The findings underscore the need for good oral hygiene in diabetics, who are particularly prone to periodontitis, or gum disease, Knowler said in an interview with Reuters Health.

Gum disease, characterized by red, swollen gums, is caused by a bacterial infection. And studies have indicated that infections and inflammation can promote blood-vessel damage in the heart and kidneys, said Knowler, chief of the diabetes and arthritis epidemiology section of the National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix.

While gum disease might not be diagnosed until mid-life or later, infection with the bacteria that cause it can occur decades earlier. Combined with years of inadequate oral hygiene, infection can result in gingivitis, an early form of gum disease characterized by inflamed gums that often bleed easily. This form of the disease can usually be reversed with more careful brushing and flossing.

But as the more aggressive periodontitis develops, the gums and bone surrounding the teeth can become seriously damaged, and teeth may loosen or fall out.

The new study involved 549 Pima Indians ages 45 or older with type 2 diabetes, the most common form of the disease. At the beginning of the study, the prevalence of severe gum disease, marked by the loss of bone and often teeth, was roughly 60 percent.

During a follow-up period of about 10 years, 172 participants died of natural causes, according to findings presented at a recent meeting of the American Diabetes Association in New Orleans.

Overall, the rate of death from natural causes was 42 per 1,000 people per year among participants with severe gum disease, compared with 26.6 per 1,000 people per year among those who did not.

The extra deaths among those with severe gum disease were due to heart disease and diabetic nephropathy, and not to other causes such as cancer or liver disease, Knowler and colleagues concluded.

Diabetic nephropathy is a condition in which diabetes damages the kidneys, which then progressively lose their ability to function normally and eventually fail.

After adjusting for factors such as age, sex, duration of diabetes, obesity and cholesterol levels, the researchers found that diabetics with severe gum disease were twice as likely as those without it to die from either heart disease or kidney failure.

Snoring can kill

WASHINGTON (Reuters) -- Dental surgeons said Saturday they have discovered why snoring can kill sometimes: It can actually cause damage to the arteries.

Snoring is usually harmless, if annoying, unless a person has a particular disorder known as sleep apnea.

Sleep apnea is marked by irregular breathing and snorting. Sufferers often stop breathing completely for up to several seconds. It usually affects overweight, middle-aged men and has been linked with stroke and heart disease.

A team at the University of California at Los Angeles School of Dentistry set out to see what the physical mechanism is.

Writing in the Journal of Oral and Maxillofacial Surgery, they said X-rays showed it is more complicated than seems immediately obvious.

"When persons with sleep apnea fall asleep, their tongue falls back into their throat, blocking their airway. As they struggle for breath, their blood pressure soars," Dr. Arthur Friedlander, an oral surgeon who worked on the study, said in a statement.

"We believe that this rise in blood pressure damages the inner walls of the carotid arteries lining the sides of the neck," he added.

"Cholesterol and calcium stick to the injury sites and amass into calcified plaques, which block blood flow to the brain. The result is often a massive stroke."

Two-minute brush helps achieve cleaner teeth: study

NEW YORK (Reuters Health) - Although hard work tends to pay off in other areas of life, forceful toothbrushing appears to be no better at ridding the mouth of plaque than a medium effort.

A group of European researchers discovered that the most efficient means of reducing plaque appears to be brushing for about two minutes at a medium force.

More vigorous teeth cleaning may actually do more harm than good, said Dr. Peter A. Heasman of the University of Newcastle upon Tyne, UK. Research suggests that heavy brushing can damage gums and wear down teeth, both potentially serious oral health problems, he said.

"Although we found that you have to brush your teeth reasonably long and hard to get rid of the harmful plaque which causes dental diseases, our research shows that once you go beyond a certain point you aren't being any more effective," Heasman said in a statement.

"You could actually be harming your gums and possibly your teeth," he added.

Heasman and his colleagues designed the study, published in the Journal of Clinical Periodontology, to determine the most efficient way to brush away plaque. Plaque is a sticky substance that can contain more than 300 species of bacteria, which adhere to tooth surfaces and produce cavity-causing acid. Plaque is a leading cause of gum disease.

During the study, Heasman and his colleagues measured plaque levels in the mouths of 12 people after they brushed their teeth using four different forces and for four periods of time -- 30 seconds, 60 seconds, 120 seconds, and 180 seconds.

The study participants brushed using a power toothbrush, which exerted set forces of between 75 grams and 300 grams. All spent 24 hours without cleaning their teeth before testing how well each technique stripped their mouths of plaque.

Heasman said that a force of 75 grams feels much lighter than one of 300 grams. However, he recommended that people visit their dentist to determine how different brushing forces feel.

"It is very difficult for a lay person to differentiate between brushing forces," Heasman told Reuters Health.

Longer brushing generally appeared better, but the researchers found that 120 seconds of brushing was roughly just as effective at removing plaque as longer brushing. And during those longer sessions, people removed about the same amount of plaque using a force of 150 grams as when they employed forces of 225 and 300 grams.

Although different people may require more or less time to get at all the plaque-ridden nooks and crannies in their mouth, spending around two minutes brushing your teeth seems "about right", Heasman said.

And applying a force beyond 150 grams -- somewhere in between light and forceful brushing -- "offered little benefit to plaque removal," Heasman added.

Furthermore, in toothbrushing, it is possible to have too much of a good thing, the researcher said.

"In the short term, gum changes may become apparent, but in the longer term, tooth wear or toothbrush abrasion is likely with too abrasive a technique, toothpaste, brush or force," Heasman said.

SOURCE: Journal of Clinical Periodontology 2003;30:409-413.

Tooth Loss Linked to Pancreatic Cancer in Smokers

NEW YORK (Reuters Health) - The more teeth a smoker loses, the higher the risk that he will develop pancreatic cancer, according to a new study.

The risk of developing pancreatic cancer was 63 percent higher in smokers who had lost all their teeth, compared with those who had lost fewer than 10 teeth, researchers reported in the American Journal of Clinical Nutrition. Overall, the risk of pancreatic cancer in the group was about 6 in 1000.

The study doesn't show that tooth loss causes pancreatic cancer, the study's lead author Rachel Z. Stolzenberg-Solomon said in an interview with Reuters Health.

Tooth loss could simply be a marker for some other factor that leads to cancer, said Stolzenberg-Solomon, an investigator in the Nutritional Epidemiology Branch at the National Cancer Institute. For example, she said, tooth loss could simply be a marker for an unhealthy lifestyle.

On the other hand, Stolzenberg-Solomon said, smokers who have lost all their teeth may have more bacteria in their mouths. And this higher level of bacteria in the mouth may lead to higher levels of bacteria in the gut.

"There is a hypothesis that connects bacterial load with pancreatic cancer," Stolzenberg-Solomon said. "Bacteria in the stomach convert nitrates and nitrites into nitrosamines. And nitrosamines are carcinogens."

For the new study, Stolzenberg-Solomon and her colleagues examined the medical records of 29,104 male smokers. The men, who were aged 50 to 69 at the start of the study, were followed from 1985 to 1997. They were asked about their dental health at the beginning of the study. By the end of the study, 174 men had developed pancreatic cancer.

After taking age, education, and whether the men lived in a rural or urban environment into account, the researchers found that men were 63 percent more likely to develop pancreatic cancer if they had lost all their teeth.

While the new study doesn't prove that the conditions that promote tooth loss lead to an elevated cancer risk, it does underscore the importance of good dental hygiene, Stolzenberg-Solomon said.

Studies have shown that the use of dental floss and toothpaste are linked with lower risk of cancers of the mouth and esophagus, she said.

Source: American Journal of Clinical Nutrition 2003;78:176-181

New cavity-fighting agent shows promise

New cavity-fighting agent shows promise

NEW YORK (Reuters Health) - An experimental cavity-fighting toothpaste may be better at preventing tooth decay and cavities than traditional fluoride toothpaste, according to a study.

The new agent does not contain any fluoride, which has been the cornerstone of cavity prevention for decades.

The product, called CaviStat, contains the amino acid arginine as well as calcium carbonate. The toothpaste may help fight cavities by promoting a higher pH in the mouth, according to Mitchell Goldberg, president of Ortek Therapeutics Inc., the company granted the licensing rights to the product by the Research Foundation of the State University of New York.

After eating food, the bacteria trapped in sticky plaque inside the mouth metabolize sugars and release acid. Over time, this process can eat away at the enamel of the tooth and promote decay.

The study, which is due to be presented at the International Association of Dental Research in Sweden later this week, suggests the calcium carbonate portion of the CaviStat might also remineralize teeth at a higher rate than fluoride, explained Goldberg in an interview.

Dr. Dan Meyer, director of science at the American Dental Association characterized his reaction to the study as "guardedly optimistic." He said he hasn't actually evaluated the product.

"Normally, you like to have several studies that find similar results," he said, adding that the current study "shows promise," but more research is needed to validate the anti-cavity findings.

In the study, Dr. Israel Kleinberg, of Stony Brook University in New York, and colleagues evaluated the efficacy of CaviStat among 726 Venezuelan children who were between 10 and 11 years old.

Half of the youngsters were instructed to brush their teeth three times a day for one minute with CaviStat toothpaste, and the other used traditional fluoride toothpaste.

After one year, CaviStat appeared to reduce the signs of early tooth decay, according to Goldberg.

At the end of two years, kids who used CaviStat had fewer cavities compared to the ones in the fluoride group, said Goldberg.

Although this is the first large clinical trial of the product to be conducted, Goldberg said he is confident that future trials will show similar results.

Recurrent Aphthous Stomatitis

Recurrent aphthous stomatitis (RAS) is a disorder characterized by recurring ulcers in the oral mucosa in patients with no other signs of disease. RAS appears to represent several pathological states with similar clinical manifestations, including immunologic disorders, hematologic deficiencies, and allergic or psychological abnormalities. RAS affects 20% of the general population and is classified according to clinical characteristics as minor ulcers, major ulcers and herpetiform ulcers.

Minor ulcers, which comprise more than 80% of RAS cases, are less than 1 cm in diameter and heal without scars. Major ulcers are over 1 cm in diameter, take longer to heal and often scar on healing. Herpetiform ulcers are considered a distinct clinical entity that manifests as recurrent crops of dozens of small ulcers throughout the oral mucosa.

The primary known etiology for RAS is heredity. Studies indicate that there is an increased susceptibility to RAS among children of RAS-positive parents.¹ Other associated factors include local trauma and nutritional disorders, such as deficiencies in vitamin B12, folic acid and serum iron.² Patients with RAS may have an abnormal immunologic response to their own oral mucosal tissue. It was once assumed that RAS was a form of recurrent herpes simplex virus (HSV) infection; however, studies have shown that HSV cannot be cultured from RAS lesions, and HSV antigens are usually not detectable in these lesions.³ It is also well documented that cessation of smoking increases the frequency and severity of RAS.⁴

The first episode of RAS most frequently begins during the second decade of life, and in individual patients may be precipitated by minor trauma or menstruation. The lesions are confined to the oral mucosa and begin with prodromal burning sensation any time from 2 to 48 hours before an ulcer appears. For minor RAS, ulcerations are well-circumscribed, round, sometimes covered by a yellow-gray pseudomembrane and surrounded by an erythematous halo. Their duration is about one to two weeks. Ulcerations heal without scarring, and are usually confined to non-keratinized oral mucosa.

Major RAS ulcers are greater than 1 cm in diameter, well-circumscribed and round, with indurated margins. The lesions heal slowly, and leave scars that may result in decreased mobility of the uvula and tongue and destruction of portions of the oral mucosa.

The herpetiform is the least common type of RAS and is usually found in clusters of dozens of lesions that heal without scarring.

RAS is the most common cause of recurring oral ulcers. It is essentially diagnosed by exclusion of other diseases. The history should emphasize symptoms of blood dyscrasias, connective tissue disease such as lupus, gastrointestinal complaints, and associated skin, eye, genital or rectal lesions. Laboratory investigation is indicated in patients with major RAS, when RAS is worsening, when RAS begins after age 25, or when there are associated signs and symptoms. Laboratory tests may include a complete blood count, iron/folate/Vitamin B12 levels, and an anti-nuclear antibody titer to screen for systemic illnesses.

Topical Therapy

Medication prescribed to treat RAS should relate to the severity of the disease. In mild cases, with two or three small lesions, use of topical coating agents such as Orabase or Zilactin is appropriate. Pain relief can be obtained with the use of a topical anesthetic agent, such as benzocaine in Orabase.

In more severe cases, the use of a high potency topical steroid preparation, such as fluocinonide, betamethasone or clobetasol, placed directly on the lesion shortens healing time and the size of the ulcer.

Other topical preparations that have been shown to decrease the healing time of minor RAS lesions include amlexanox paste and topical tetracycline.

Systemic Therapy

For patients with major aphthae or severe cases of multiple minor aphthae who do not respond to topical therapy the use of systemic therapy should be considered. Pentoxifylline (PTX) can be used systemically to control ulcers that do not respond to topical medication. PTX is a methylxanthine compound related to caffeine and theophylline. It is used chiefly to treat peripheral vascular disease because it increases the flexibility of red blood cells and enhances blood flow to ischemic limbs. It also increases neutrophil chemotaxis and motility, and decreases the clumping of neutrophils. And it has anti-inflammatory properties by decreasing the production of cytokines and by decreasing the effect of the cytokines on leukocytes. Several reports suggest that PTX is effective in preventing aphthous ulcers.

Wahba-Yahav reported that patients with RAS who did not respond to topical steroid showed significant success with PTX therapy.⁵ Another study demonstrated the efficacy of PTX in treating patients with recurrent ulcers with no significant side effects and supported the use of PTX in refractory cases of major RAS.⁶

Another systemic medication that has been used with success in treating ulcers that are unresponsive to topical medication is colchicine. Colchicine is an anti-inflammatory agent that limits leukocyte activity by binding to tubulin, a cellular microtubular protein, and, therefore, inhibiting protein polymerization.⁷ It also inhibits lysosomal degranulation and increases the level of cyclic AMP, which decreases both the chemotactic and the phagocytic activity of neutrophils.⁸

Colchicine is also shown to inhibit cell-mediated immune responses.⁹ Clinically, colchicine has been used for acute gouty arthritis, psoriasis, dermatitis herpetiformis, leukocytoclastic vasculitis and urticarial vasculitis. There have been published reports that show the benefit of using colchicine in treating major RAS and preventing further recurrences of ulcers.^10,11

Reported adverse effects of colchicine include myopathy, peripheral neuritis and gastrointestinal toxicity, including nausea, vomiting, diarrhea and abdominal pain. It has also been known to induce blood dyscrasias, and is considered a potent teratogen that should be avoided during pregnancy.

Thalidomide has been shown to reduce the incidence and severity of RAS. The drug was first marketed in Europe in the 1950s as a non-addictive sedative agent, but it was withdrawn from the market nearly 40 years ago after the discovery of its teratogenicity.

Thalidomide has returned to the medical arena, with the Food and Drug Administration approving it as a treatment for erythema nodosum leprosum in July 1998. It suppresses monocytic synthesis of TNF-alpha and accelerates TNF-alpha messenger ribonucleic acid transcript degradation.12 Thalidomide also displays anti-inflammatory characteristics as well as antiangiogenic properties. Several reports have been published reporting positive results when treating severe recurrent ulcers with thalidomide.^13,14

Thalidomide has many serious adverse effects, including teratogenicity, peripheral neuropathy, and other minor adverse effects, such as dizziness and somnolence. To minimize the risk of teratogenicity, the System for Thalidomide Education Prescribing Safety (S.T.E.P.S.) program has been instituted to control and monitor the use of thalidomide. Under the program, clinicians are required to provide comprehensive counseling to patients and to complete surveys. Patients who receive thalidomide must also comply with several regulations, including completing consent forms when receiving thalidomide, agreeing to two simultaneous forms of contraception and presenting a negative pregnancy test during each monthly follow-up appointment.

Careful consideration must be given when thalidomide therapy is warranted for patients with major RAS that does not respond to other treatment. The clinician must carefully weigh both the benefits and risks of using thalidomide, reserving it for the most resistant and severe cases of major RAS. Only clinicians knowledgeable in its potential side effects should prescribe thalidomide

Keeping you abreast with the latest in Dentistry!

Fifth-Generation Bonding Agents

Dentin bonding agents (DBAs) that don't require a separate phosphoric etchant acid are called "self- etching primer" products. They bond to dentin and cut (i.e. prepared) enamel by etching the tooth with an acid that is already in the bonding agent. In other words, no separate phosphoric acid etching is necessary with them. Self-etching primer DBAs come as either two bottles (a self-etching primer, followed by a separate adhesive) or one (etchant, primer, and adhesive all-in-one). Examples of each type are given in the table below
Two-Bottle Products One-Bottle Products
Clearfil SE bond (Kuraray)
Clearfil Liner Bond 2V (Kuraray)

Prompt L-Pop (3M ESPE)
One-Up Bond F (Tokuyama/J. Morita)
Touch & Bond (Parkel)

Perhaps the most recent development in bonding has been the addition of self-etching primers to the fifth- generation bonding agents. Fifth-generation DBAs, also known as "one-bottle" or "one-component" DBAs, have been available since the mid-1990s and include such products as Single Bond (3M ESPE), OptiBond Solo Plus (SDS/Kerr), PQ1 (Ultradent), Excite (Ivoclar Vivadent). Their manufacturers don't want to be left behind now that self-etching primers have become popular, so they have incorporated these into their product lines. Until very recently, the fifth-generation DBAs consisted of a single bottle or syringe that contained both the primer and the adhesive. The tooth structure needed to be treated with phosphoric acid before they were applied. Now, in response to the latest self-etching primer products, the manufacturers of some of the fifth- generation DBAs are selling them with self-etching primers that are used in place of the phosphoric acid. Why do this? Well, the manufacturers claim that using a self-etching primer reduces post-treatment sensitivity and shortens the clinical procedure. In addition, you no longer have to be concerned about how moist the tooth should be at the time of application. Two examples of fifth-generation DBAs now available with self-etching primers are One-Step Plus with Tyrian SPE from Bisco and OptiBond Solo Plus with Self- Etch Primer from SDS/Kerr. If you use One-Step Plus or OptiBond Solo Plus and want to reduce the possibility of post-treatment sensitivity, you may want to consider trying a self-ecthing primer with it. Please note, though, that not all fifth-generation DBAs come with self-etching primers; the only ones currently available are the SDS/Kerr and Bisco products.

Through the technology of self-etching adhesives it is now possible to avoid some of the problems that have been associated with the total-etch technique. Post operative sensitivity can be eliminated using the selfetch technique which is even significantly less technique-sensitive than total-etch.

One-Up Bond F changes colour giving the clinician a clear
indication of when the bonding agent A & B have mixed.
(Material turns from yellow to pink upon mixing, and the pink
colour will disappear upon light curing. The pink colour gives
an easy to read guide to full tooth coverage.



DO ENDODONTICALLY-TREATED TEETH REALLY BENEFIT FROM CROWN PLACEMENT?

Relationship between crown placement and the survival of endodontically treated teeth. Aquilino SA, Caplan DJ. J Prosthet Dent 2002;87:256-263.



Traditionally, it has been accepted that the best treatment for a posterior, endodontically-treated tooth is some form of coronal coverage. This may take the form of a gold, ceramic, resin composite, or amalgam restoration that covers the occlusal aspect of the tooth to prevent it from fracture. The purpose of this retrospective study was to evaluate the hypothesis that crown placement improves the long-term survivability of endodontically-treated teeth. The researchers used a dental school database to identify 280 patients (400 teeth) that had received endodontic during a two-year period. Patient records, radiographs, and a computer database were used to select from this number those who met the inclusion criteria of the study. Kaplan-Meier survival estimates were then generated for those 203 teeth. Results indicated that endodontically- treated teeth that had not received a crown were lost at a rate six times greater than those that had. The authors concluded there was a strong association between placement of a crown and survival of an endodontically-treated teeth.



Quite a number of previously published articles and scientific papers have voiced the opinion that endodontically-treated posterior teeth (as well as anterior teeth with loss of significant coronal tooth structure) should receive crowns to protect them from fracture and extend their longevity. At least one study has shown that crowned endodontically-treated teeth survive longer than those that were not crowned. As the authors of the current study indicated, crowns are not the only viable option to protect teeth following obturation. Cuspal coverage may also be provided by complex amalgams and by gold, ceramic, and resin composite onlays. Unfortunately, although one would expect that these treatments would function for this purpose at least as well as full coronal coverage, no reports exist in the literature to support this contention. Regardless of the specific treatment employed, the evidence does seem to indicate that obturated teeth benefit from restorative coverage of their fracture-prone occlusal surfaces.



TOOTH WHITENING AGENTS: WHAT A PAIN!

Sensitivity and tooth whitening agents. Pohjola RM, Browning WD, Hackman ST, Myers ML, Downey MC. J Esthet Restor Dent 2002;14:85-91.



One of the common side effects of bleaching vital teeth is tooth and gingival sensitivity to changes. Several new bleaching products have been marketed to address this problem. This study evaluated three commercially-available products to identify their incidence of sensitivity (involving teeth and soft tissues) and efficacy of whitening. Eighteen patients were divided into three groups of six each. Each of thegroups was treated for two weeks with one of the following whitening agents: NiteWhite Excel 2Z (Discus Dental), fx (Challenge Products), and Rembrandt Xtra-Comfort (Den-Mat). Patients kept a daily diary to record sensitivity and the first day they noticed a whitening effect. Shade change and tooth sensitivity were evaluated at recall appointments at 1 week, 2 weeks, and 4 weeks. Results indicated that the two products marketed as zero-sensitivity bleaches (NiteWhite Excel 2Z and Rembrandt Xtra-Comfort) produced no teeth sensitivity and were significantly different in this regard from fx. All produced a statistically similar degree of soft tissue sensitivity. All three were found to be effective whiteners, producing an average shade guide change of 8. The authors concluded that of the three products, none was sensitivity free, but NiteWhite Excel 2Z and Rembrandt Xtra-Comfort (the zero sensitivity products) did not produce thermal sensitivity. All produced a similar change in shade tab value.

A very common side effect of vital tooth bleaching is transient sensitivity of the teeth and/or soft tissues. Fortunately, the sensitivity is dose-related and transient. Regardless, it is frustrating for patients and enough of an annoyance to dissuade some from finishing treatment. Recently, manufacturers have added potassium nitrate an/or fluoride in an attempt to reduce sensitivity. This study indicates that these products are at least effective at reducing the incidence of thermally-related tooth sensitivity, while retaining their effectiveness at tooth whitening. Practitioners should note that they do not reduce soft tissue sensitivity, so patients should be advised that they may experience transient gingival, tongue, or throat sensitivity with these products.

HOW ABOUT THOSE CARIES DISCLOSING PRODUCTS?

Effect of caries disclosing agents on bond strengths of total-etch and self-etching primer dentin bonding systems to resin composite. Kazemi RB, Meiers JC, Peppers K. Oper Dent 2002;27:238-242.

This study evaluated the effect of two commercially-available caries detection solutions on the bond strength of three bonding products to resin composite. Extracted human molars were sectioned to produce 108 flat dentin surfaces. Thirty-six surfaces were then either left untreated (control) or treated with one of two caries disclosing solutions (Snoop, Pulpdent or Seek, Ultradent). The 36 specimens of each type of treatment were then treated with one of three bonding agents: Prime & Bond NT (a partially filled, total-etch product from Dentsply/Caulk), Clearfil SE Bond (a self-etching primer product from Kuraray), or Prompt L-Pop (a self-etching primer, all-in- one product from Parkell). Tetric Ceram (Ivoclar Vivadent) resin composite was then bonded to the dentin surfaces. The specimens were stored for 24 hours, thermocycled, and tested for shear bond strength. Results indicated that neither of the two caries disclosing solutions significantly affected the bond strength of the bonding products.

Caries detection solutions have been been used by clinicians to distinguish between affected and infected dentin. Affected dentin is the dentin that is adjacent to a carious lesion and is not contaminated by bacteria. While it may be softer than normal dentin, it should be retained because it has the potential for remineralization. Infected dentin, on the other hand, contains bacteria and should be removed during preparation. Several commercial products are now available for distinguishing between the two, such as Caries Detector, Snoop, Seek, and To Dye For. DIS published a synopsis of these products in DIS 63-07. This study evaluated how these products affect the shear bond strengths of some of the newest types of bonding agents. The results of the study should give clinicians who routinely use caries detection solution some reassurance that, for at least the tested bonding agents, no adverse effects occur. It is important to note, however, that the caries detection solutions and bonding agents in this study were tested using sound, intact dentin and not carious dentin as would be the case intraorally. Results may differ when caries-affected dentin is involved. Interestingly, although the purpose of this study was not to compare the bond strengths of the three dentin bonding products, Prompt L-Pop did not perform as well as CLearfil SE Bond and Prime & Bond NT.



PoGo One Step Diamond Micro-Polishers

PoGo One Step Diamond Micro-Polishers from Dentsply/Caulk are used for polishing resin composite and compomer restorative materials. Each is a diamond-impregnated, urethane dimethacrylate disc mounted on a plastic, latch-type, slow-speed handpiece mandrel. The single-use discs are used with increasing light pressure to purportedly produce a highly polished surface. A PoGo Starter Kit contains 40 discs, written instructions, and a laminated instruction card.



NRG™ LED Curing Light

The NRG™ LED Curing Light uses focused Light Emitting Diode (LED) technology to polymerize visible-light-activated materials having camphoroquinone as their photoinitiator. Dentsply/Caulk claims that the NRG™ Light is capable of polymerizing a 2-mm-thick layer of most of its visible light-cured materials in 10 seconds. This unit, like other first- generation LED curing lights, uses gallium nitride semiconductors to produce a narrow spectral range that is close to the absorption spectrum of camphorquinone (i.e., 450 to 490 nm). Due to the combination of this more specific spectral range and the LED's superior energy conversion rate compared to halogen lamps, the NRG™ LED Curing Light is purported to generate sufficient intensity for polymerization using rechargeable batteries rather than line voltage. This allows the NRG™ LED Curing Light to be portable and lightweight, and it eliminates the need for restrictive cords. A fully-charged battery is reported to typically provide 250 ten-second exposures (i.e., 40 minutes) without recharging. A fully depleted battery requires overnight recharging. The NRG™ LED Curing Light, in contrast to the wand design of most other available LED curing lights, uses the more familiar gun-shaped design of conventional halogen curing lights. The controls are located on the handpiece and consist of an on/off button and an activation button. There is no timer selection; only 10-second exposures are available. Longer exposures are accomplished by depressing the activation button every 10 seconds. The NRG™ LED Curing Light is shipped with a 9-mm-diameter, non- autoclavable light guide containing 7 LEDs. Optional light guides include a 3-mm "tacking probe" for tacking indirect resin restorations, and a 3-mm "transillumination probe." Dentsply/Caulk recommends barrier protection of the light guide or disinfection. The NRG™ LED Curing Light is 9 inches long and 4½ inches deep and weighs 16 ounces. The charging unit is only available in 120V at this time.

Manufacturer:

Dentsply/Caulk www.caulk.com

PROs

+ Portable and light weight.

+ Ergonomic, with familiar gun- shaped design.

+ Adequately polymerizes hybrid resin composite in 35 seconds.

+ Very quiet.

CONs

- Did not cure Dentsply/Caulk resin composite in 10 seconds as advertised.

- Required 63 seconds to adequately cure microfill.

- Didn't maintain output as battery discharged.

- Activation button is inconveniently located.

- More expensive than halogen lights.

ADVANTAGES:

+ Offers the conveniences of portability and light weight.

+ Is ergonomic and has a familiar gun-shaped design.

+ Adequately polymerizes hybrid resin composite in 35 seconds.

+ Curing tip swivels 360 degrees to facilitate intraoral access.

+ Instructions are clear and easy to understand.

+ Very quiet.

+ Requires little counter space for storage.

DISADVANTAGES:

- Did not cure Dentsply/Caulk resin composite in 10 seconds as advertised.

- Required 63 seconds to adequately cure microfill resin composite.

- Required more time than the control halogen light unit to adequately polymerize all resin composites tested.

- Activation button is not easy to use because of its inconvenient location.

- Did not maintain initial output throughout battery discharge.

- Not provided with built-in radiometer.

- Rechargeable battery is not replaceable without returning the unit to manufacturer.

- More expensive than most halogen curing lights.

- Curing tip becomes warm with repeated use.

- Handpiece is easy to incorrectly place in charging base.

- Has only one exposure time setting (10 seconds).

- Curing tips are not autoclavable.

- Different types of disinfectants are recommended for curing tip and handpiece.

SUMMARY AND CONCLUSIONS:

The NRG™ LED Curing Light is a lightweight, compact curing light that uses the light emitting diode (LED) technology. Clinical evaluators appreciated its portability, convenience, and gun-shaped design, however the activation button was not placed in the proper position for easy use. The light is advertised by Caulk/Dentsply as being able to polymerize resin composites in 10 seconds. DIS testing could not substantiate this claim even when a Dentsply/Caulk resin composite was used. Using the same resin composites as in past evaluations, the NRG™ LED Curing Light adequately polymerized the hybrid resin composite in a timely manner, but not the microfill resin composite. However, previous DIS testing has found that most standard (i.e., average-intensity) halogen lights also inadequately polymerize microfill resin composites unless used for 60 seconds. Only high- intensity halogen lights (i.e., with an output of >1000 mW/cm2) can predictably polymerize microfills in 40 seconds or less. When using an average-intensity halogen light (i.e., 300 to 600 mW/cm2) to cure a 2-mm-thick resin composite, 40 seconds are required to adequately polymerize a hybrid resin composite and 60 seconds for a microfill. DIS testing found that the NRG™ LED Curing Light required approximately the same amount of time (35 seconds and 63 seconds) to polymerize the same materials. Because the unit's LEDs are at the end of the curing tip, the tip is not autoclavable. Adding to this problem is the fact that two different classes of disinfectants are recommended for the curing tip and plastic handpiece. Despite its numerous disadvantages, the clinical evaluators rated the light as "Good" to "Excellent," primarily because of its portability and light weight. Unfortunately, the advantages of portability and ease of use do not outweigh the inability of the light to meet advertising claims.

Selection of Analgesics

Efficiency in pain control is often taken as a yardstick to assess a medical/ dental practitioner by patients. Effective pain relief can be achieved with oral non-opioids and non-steroidal anti-inflammatory drugs. These drugs are appropriate for many post-traumatic and post surgical pains, especially when patients go home on the day of the operation.

It is disheartening that in the selection of analgesics, tradition and ill informed prejudice sometimes hold sway over evidence and common sense. Analgesic efficiency is expressed as the Number Needed to Treat (NNT) i.e., the number of patients who need to receive the active drug to achieve at least 50% relief of pain in one patient compared with placebo, over a six-hour treatment period.

To calculate NNT

1. Calculate the percentage of people who have the desired outcome in the treatment group. E.g., 80/200 X 100 = 40% (80 got relief in 200 patients)

2. Calculate the percentage of people who have the desired outcome in the placebo or control group. E.g., 40/200 X 100 = 20%

3. Take (2) away from (1) to give the percentage of people helped by the treatment. e.g., 40- 20 =20

4. Divide 100 by this percentage to give the NNT. E.g., 100/20 =5

The most effective drugs have a low NNT of about 2, meaning that for every two patients who receive the drug, one patient will get at least 50% relief because of the treatment (the other patient may obtain relief but it does not reach the 50% level).

For paracetamol 1gm, the NNT is nearly 5. Combinations of paracetamol 650mg with dextropropoxyphene 65mg (e.g., Poxy plus, Novamed) improves the NNT slightly. Ibuprofen is better at 3 and diclofenac (e.g., Oxalgin, Zydus Cadila ) at about 2.5.

These NNT comparisons are against placebo, the best NNT 2 means that while 50 of 100 patients will get at least 50% relief because of the treatment, another 20% will have a placebo response which then gives at least 50% relief, so that with diclofenac 70 out of 100 will have effective pain relief.

If the patients can swallow, it is best to prescribe drugs to be taken orally. Of the oral analgesics, Non Steroidal Anti Inflammatory Drugs (NSAID) perform best, and paracetamol alone or in combination are also effective.

Some of the NSAIDs are Ketoprofen, Aspirin, Naproxen, Indomethacin, Ketorolac, Piroxicam, Celecoxib, Meloxicam, Mefenemic acid, Rofecoxib, Diclofenac and Nimeluside.

Celecoxib (e.g., Zycel, Zydus Cadilla and Colcibra from Ranbaxy ), Rofecoxib (e.g., Toroxx 25 from Torrnet pharma and Rofact from Sun pharma), Meloxicam (e.g., Melogesic, Lupin) and Nimesulide (e.g., Nimbid, Astra-IDL) belong to a new family of NSAIDs. They are referred to as cyclooxygenase-2 (COX-2) inhibitors. Celecoxib has been approved for treatment of rheumatoid arthritis in USA, and rofecoxib is approved for treatment of acute pain.

Adverse effect data on NSAIDs from long term dosing, where gastric bleeding is the main worry, rates ibuprofen the safest. Gastrointestinal ulcers and bleeding are side effects of traditional NSAIDs that block COX-1 and COX-2. Both COX-1 and COX-2contribute to inflammatory response. In the gastrointestinal mucosa, COX-1 plays and important role. Prostaglandins such as prostaglandin E2 (PGE2) that are produced from COX-1 derived PGH2 protect gastrointestinal lining against ulceration.

Because traditional NSAIDs inhibit COX-1 and COX-2, they decrease gastrointestinal synthesis of prostaglandin (predisposing patients to GI ulceration) and production of platelet thromboxane A2 (predisposing patients to bleeding).

Though clinical data on GI toxicity of celecoxib and rofecoxib are limited, they are encouraging and show approximately 1% absolute risk reduction for symptomatic ulcers. Post marketing surveillance should help clarify the actual risk for serious ulcer complications with these new COX-2 inhibitors and reveal other non-gastrointestinal toxic reactions that result from their use.

Mouthwashes

From simple breath fresheners to products that can really influence oral health, a variety of mouth washes are available in the market.

Fluoride containing mouth rinses help to prevent dental decay. They may be recommended for:

1. Children having orthodontic treatment
2. Children with high caries risk A.M.-P.M. Junior (Elder) mouth wash contains 0.03% Triclosan and 0.05% Sodium Fluoride.
3. Patients suffering from dry mouth and
4. Patients who have undergone radiation therapy.

Antiplaque or anti microbial mouth wash is used to inhibit bacterial plaque formation and prevent or resolve chronic gingivitis. They can affect only supra gingival plaque. So they have no role in the treatment of existing periodontal disease, since they cannot either reach the sub gingival environment or penetrate thick layers of established plaque. In these situations, they are used after supra and sub gingival scaling has been done, rendering the tooth surfaces clean, in order to maintain this situation for a short period when the soreness of the gingiva may prevent effective mechanical plaque control.

Indications for Antiplaque mouth washes

1. To replace mechanical tooth brushing when this is not possible in the following situations.
1. In cases of acute oral mucosal and gingival infections
2. After periodontal or oral surgery and during the healing period
3. After cosmetic jaw surgery or intermaxillary fixation used to treat jaw fractures.
4. For mentally and physically handicapped patients.
2. As an adjunct to normal mechanical brushing in situations where this may be compromised by discomfort or inadequacies.

a. After scaling when there is cervical hypersensitivity due to exposed root surfaces, prescribe mouth washes for about 4 weeks. Measures to treat hypersensitivity should also be instituted simultaneously.

b. Following sub gingival scaling and root planning when the gingivae may be sore for a few daysm use of a mouth wash is recommended for about 3 days.

Types of Antiplaque mouth washes

1. Mouth washes containing essential oils. Listerine (Parke Davis), one of the oldest mouth washes available, is an essential oil/phenolic mouth wash. It has been shown to have moderate plaque inhibitory effect and some anti-gingivitis effect. Its lack of profound plaque inhibitory effect is because it has poor oral retention.
2. Oxygenating agents like Hydrogen peroxide, buffered Sodium peroxyborate and Peroxy carbonate in mouth washes have a beneficial effect on acute ulcerative gingivitis, probably by inhibiting anaerobic bacteria
3. Bisguanide antiseptics, like Chlorhexidine, Alexidine and Octenidine possess antiplaque activity.

Bisguanide antiseptics are able to kill a wide range of microorganisms by damaging the cell wall.

Chlorhexidine molecule gets adsorbed onto the oral surfaces and gets released at bactericidal level over prolonged periods. Due to this process, Chlorhexidine has antiplaque properties unsurpassed by other agents.

The antibacterial action of Chlorhexidine is due to and increase in cellular membrane permeability followed by coagulation of the cytoplasmic macromolecules. It is effective in vitro against both Gram +ve and Gram –ve bacteria including aerobes and anaerobes and yeast and fungi.

Substantivity is the ability of drugs to adsorb onto and bind to soft and hard tissues. The substantivity of Chlorhexidine was first described in the 1970s. Due to this property, Chlorhexidine can maintain effective concentration for prolonged periods of time.

Different brands of Chlorhexidine are available in the market, e.g., Rexidin (Warren), Clohex (Group) and A.M.-P.M (Elder).

Side effects

1. It has an unpleasant taste
2. It alters taste sensation
3. Produces brown stains on teeth, which is very difficult to remove. This can also affect the mucous membranes and tongue and may be related to the precipitation of chromogenic dietary factors onto the teeth and mucous membranes, Due to this reason, it is important to advise patients using Chlorhexidine mouth wash to avoid the intake of tea, coffee and red wine during the duration of its use. Remember to severely restrict its use in patients with visible anterior composite and glass ionomer restorations since they also get stained.
4. Chlorhexidine encourages supra gingival calculus formation.
5. Mucosal erosion and parotid swelling are other much rarer side effects.

Since Chlorhexidine is poorly absorbed by the GI tract, it displays very low toxicity.

4. Triclosan, a trichlora-2’-hydroxy diphenyl ether, is a non-ionic antiseptic. It has a moderate antiseptic effect when used as a mouth wash in combination with zinc.

It has been shown to reduce histamine induced dermal inflammation and reduce the severity and healing period of aphthous ulcers.

Colgate Total Plax mouth wsh has Triclosan and Sodium fluoride as its components. Triclosan has little or no substantivity, but is oral retention can be increased by its combination with copolymers of methoxy ethylene and maleic acid.

5. Povidone iodine appears to have no significant plaque inhibitory activity when used as 1% mouth wash and the absorption of significant levels of iodine through the oral mucosal may make this compound for prolonged use in the oral cavity. It could cause problem of iodine sensitivity in sensitized individuals.

Piodin (Glaxo Wellcome), Povidine Gargle (Stadmed) are povidone iodine mouth washes available in the market.

The alcohol content of mouth washes

Most mouth washes contain pharmaceutical grade alcohol, as a preservative and as a semi- active ingredient. Significant amounts of alcohol contained in many mouth washes can lead to certain disadvantages. Care should be taken that they are not accidentally swallowed, especially by children, to avoid toxicity. Small children should not be advised mouth washes, because they are not able to spit out properly. More over, most children have good gingival health.

Because of known links between alcohol consumption plus tobacco smoking and oral and oral and pharyngeal cancer, it has been suggested that the frequent use of alcohol containing mouth washes might increase the incidence of this form of cancer.

Lastly, alcohol containing mouth washes have been shown to reduce the hardness of composite and hybrid resin restorations.

Endoseries 12, Access Cavity Preparation

Gaining access to root canals, wherein the root canal instruments can be slipped easily into the canals to reach the apical portion, is the most important starting point of the root canal treatment. Before you lift that hand piece to start access cavity preparation, stop and think about the following three points.

1. Have you refreshed the knowledge of the morphology and anatomy of the tooth you are going to treat?

2. Have you taken a good look at the tooth in the oral cavity? Its shape, size, tilt and morphology need careful consideration.

3. Have you spent sufficient time studying the radiograph?

Though radiograph is a two dimensional picture of a three dimensional area, it is the only guidance for us to have a knowledge of the internal anatomy of the tooth. You have to combine your knowledge, morphology of the tooth as seen in the oral cavity and the radiographic picture in your mind and create a three dimensional mental picture of the internal anatomy of the tooth. This is a very important step because it will help to avoid many mishaps like inability to locate root canals and perforations.

Some cases of attempted root canal treatment that I have seen, esp., of maxillary incisors where the previous operators couldn’t locate the canals in old patients where narrowing of root canals has occurred, were clear-cut proof that they had not given attention to what is described in the previous paragraph.

Next step, equally important, is to properly orient the bur before starting to cut the tooth. See the relationship of the tooth crown and the bur. If you are going to use indirect vision as in the maxillary teeth, take a few seconds to see the tooth and the bur by direct vision also. After confirming that the bur is positioned in the correct direction, you can start cutting by indirect vision. It is necessary to remove all caries before gaining entry into the pulp chamber.

Access cavities for maxillary incisors

Gain access cavities only through lingual surfaces. Since the pulp chamber is triangular in shape, the access cavity is prepared in a triangular form with rounded corners.

See Fig 1.

If the palatal surface of the incisor is divided into three vertically and horizontally, the initial point of entry is in the central area, just incisal to the cingulam. Hold a fissure bur perpendicular to the palatal surface and make a small depression. Gradually change the direction of the bur, holding it parallel to the long axis if the tooth. When the bur ‘drops’ into the pulp chamber, switch to a No. 4 or 6 round bur for de-roofing. One common mistake is leaving part of the roof in the labial aspect. This will lead to harboring of pulp remnants and bacteria in the niche, preventing thorough cleaning.

Fig 2.

When you have prepared the access cavity correctly and look at the access cavity through a mouth mirror, you will be able to see almost half of the root canal length.

Maxillary Canines

The access cavity should have an ovoid outline.

see Fig 3.

Maxillary Premolars

Though you may come across first premolars with single root canal, usually they have two canals (Fig 4), and

rarely three canals.

The radiograph of a premolar with three canals looks fuzzy. You can see adjacent teeth OK, but this one looks different. As you open into the pulp chamber, the palatal canal is easy, but the buccal is very tight, and in what looks like a slot running bucco-lingually. You will get the mesiobuccal canal labially, distobuccal in the middle and palatal is where you first found it.

In contrast, second premolars (Fig 5) are mostly single rooted, though some of them may have two root canals. When there is a single root canal, it is ribbon shaped i.e., wider bucco-lingually and narrower mesiodistally.

Start the access cavity preparation in the middle of the central groove and extend buccally and palatally, giving it an elongated oval shape.

Mandibular incisors

The access cavity may have a triangular shape with rounded corners or ovoid, depending on the shape and size of the teeth and age of the patient. Fig 6 A and B

Occurrence of two canals is quite common in mandibular incisors. They are difficult to access properly. The second canal usually appears to hide under the cingulam. When you look into the access opening, you should be able to see two canals. If you missed one, it’s usually the lingual. That’s because your access opening is too small from the lingual and doesn’t afford a straight line opening to the lingual canal. So, extend the access cavity into the cingulam and search for the second canal under the cingulam.

If you look into the access opening and see one small oval orifice, slightly wider from buccal to lingual, you probably have one canal. Same is the case when you see a well defined, large open canal in the radiograph.

Your radiographic clues for two canals are:

1. The pulp chamber is visible with canals disappearing apical to the chamber. They seem to disappear at the bifurcation. They are smaller and are superimposed on dense tooth structure.

2. The bilateral tooth shows evidence of two canals. Due to the angle of the radiograph, you may have a better view of this tooth.

3. Very close examination of the radiograph reveals two periodontal ligament spaces on the mesial or distal of the root. This certainly represents either a deep concavity or a second canal. Treat it as though it has two canals.

Mandibular Canines

Make the access cavity ovoid in shape, but widen it labiolingually if there are two canals. Fig 7 A and B

Mandibular Premolars

They are usually single canalled, but may also have two or three canals. The access cavity for first and second premolars should be ovoid in shape. The incidence of two canals is less in second premolars.

Fig 8 and 9.

When there are two canals, extend the access cavirty sufficiently in the buccolingual direction and when there are three canals, widen it in the mesio distal direction. In this case there will be 2 buccal canals and one lingual canal.

For learning more on endodontics CLICK HERE

Ref:

1. Franklin S Weine: Endodontic Therapy 5th ed. Mosby Yearbook Inc. USA 1996

2. Jacob Daniel: Advanced Endodontics for clinicians. J& J Publishers Bangalore 1998

Nanodentistry - The Future

The late Nobel Prize winning Physicist Richard P Feynman in 1959 proposed using machine tools to make smaller machine tools, which in turn, would be used to make still smaller machine tools, and so on, all the way down to the molecular level. Such nanomachines, nanorobots and nanodevices ultimately could be used to develop a wide range of atomically precise microscopic instrumentation and manufacturing tools. Attempts are going on at present to produce molecular computer components using molecular parts at the nanometer (10-9 meter or 1 billionth of a meter) scale.

Nanotechnology will have future medical applications leading to the emergence of nanomedicine and nanodentistry. Nanodentistry will make it possible to maintain a near perfect oral health through the use of nanomaterials, biotechnology, including tissue engineering and nanorobotics. The nanorobotic functions may be controlled by an onboard nanocomputer that executes preprogrammed instructions in response to local sensor stimuli.

Local anaesthesia: In the era of nanodentistry, to induce local anaesthesia, dental professional will instill a colloidal suspension containing millions of active analgesic micrometer sized dental nanorobot particles on the patient’s gingivae. After contacting the surface of the crown or mucosa, the ambulating nanorobots reach the dentin by migrating into the gingival sulcus and passing painlessly through the lamina propria or the 1-3 micrometer thick layer of loose tissue at the cemento dentinal junction.

On reaching the dentin, the nanorobots enter dentinal tubule holes that are 1-4 micrometers in diameter and proceed toward the pulp, guided by a combination of chemical gradients, temperature differentials and even positional navigation, all under the control of the onboard nanocomputer, as directed by the dentist.

Orthodontic treatment: Orthodontic nanorobots could directly manipulate the periodontal tissues (gingiva, periodontal ligament, cementum and alveolar bone), allowing rapid and painless tooth straightening, rotating and vertical repositioning within minutes to hours.

Natural tooth maintenance: The appearance and durability of tooth may be improved by replacing upper enamel layers with covalently bonded artificial materials such as sapphire or diamond, which have 20 to 100 times the hardness and strength of natural enamel.

A subocclusal dwelling nanorobotic dentifrice delivered by mouthwash or toothpaste could patrol all supragingival and sub gingival surfaces at least once a day, metabolizing trapped organic matter into harmless and odorless vapors and performing continuous calculus debridement.

Dentirobots could identify and destroy pathogenic bacteria residing in the plaque and elsewhere, while allowing the 500 or so species of harmless oral micro flora to be maintained in a healthy ecosystem. With this kind of daily dental care available from an early age, conventional tooth decay and gingival disease will disappear.

New Millenium Bonding

Dr. Michael Buonocore, by identifying phosphoric acid solution as an effective surface treatment for enamel, had made a milestone contribution to dentistry. Adhesive dentistry was launched when he discovered that enamel etching created microscopic surface irregularities into which resin material could flow and interlock with, to allow a strong mechanical bond. Enamel bonding systems of earlier years consisted of phosphoric acid for etching and a resin-bonding agent.

The area of the tooth receiving a restoration consists of dentin as well as enamel. The fact that a strong bond to dentin is also mandatory for the long-term prognosis of a restoration was identified and researches followed. Dentin consisting of collagen fibers and dentinal tubules filled with fluid was a challenge to obtain adhesion. The primer was introduced to ensure optimal wetting and bonding to the hydrated dentin surface.

Attempts continued to achieve chemical adhesion to tooth structure, apart from the mechanical interlocking, In 1978, Kuraray launched Clearfil bond system F, the first dental bonding system that offered mechanical and chemical adhesion to both enamel and dentin. Kuraray also introduced the Total etching (simultaneous etching of both enamel and dentin with phosphoric acid) developed by Dr. Takao Fusayama.

In 1981, Kuraray developed a new phosphate monomer (MDP-10 Methacryloyloxydecyl Dihydrogen Phosphate), which improved adhesion to dentin. Since MDP not only improved enamel and dentin adhesion, but also produced excellent adhesion to dental metals, it led to the development of Panavia dental adhesive cement. Those of us who have used Panavia for cementing crowns and bridges know what an excellent and reliable adhesion it provides.

The ‘total etch’ concept was accepted in America only in 1990, when Bisco introduced All Bond and total etch instruction. John Kanca played a key role in the Bisco project. The All Bond procedure, derived from Kanca’s concept was,

E + nxP + B i.e., Etch, Prime (n coats) and finally, Bond.

Subsequently there was the simplification,

E + nxPB These ‘one bottle’ systems were to facilitate clinical use. They combined the primer and adhesive into one solution to be applied after total etch. ‘Prime and Bond’ from Dentsply incorporated this concept.

The shortcomings of ‘one bottle’ bonds include the potential for excessive dentin decalcification and their reliance on very careful moisture control to achieve good bonding and sealing results.

Soon there was a paradigm shift

EP + B This one was from Kuraray in the ‘Liner Bond 2’, a self-etching primer. The advantages include gentler etching, elimination of water rinsing, and dentin sealing that virtually eliminates postoperative sensitivity. Also, there is no need to worry about preventing collagen collapse.

The next simplification has also arrived in the market,

nxEPB , which is Espe’s Prompt L- Pop, which is a water based self etching adhesive that once activated in the "blister pack", has a pH value of approximately 1.0. It produces the known surface porosity used for micromechanical retention in enamel, with the dentin surface also being conditioned in a similar manner.

Prompt L- Pop is a unit dose system, with etchant, primer, adhesive and microbrush sealed in a triple lollipop- shaped aluminium foil package. It is used for direct application with all standard composites (eg. Pertac II, Tetric Ceram, Z 100, Z 250, Spectrum TPH, Herculite XRV), compomers (eg. Dyract AP, Compoglass, F 2000 and Hytac) and Ormocers (these are organically modified ceramics eg. Definite from Degussa).

Meanwhile, Tokuyama has launched ‘One-Up Bond’ that will be the first EPB to contain color change polymerization indicators. When light cured completely, it shifts from pink to tooth color.

Ref:

1. J Clinical Orthodontics. Oct 200
2. J of Dentistry for children May-June 2000
3. Internet source

Placement of Gingival Restorative Margins

The most significant factor in the long term prognosis of a restored tooth is the preservation of a healthy periodontal attachment.

The best restorative margin is placed coronal to soft tissue. It is cleansable and can be maintained more easily.

The term "biologic width" denotes the combined connective tissue- epithelial attachment from the crest of the alveolar bone to the base of the gingival sulcus. This includes the width of supra-alveolar connective tissue fibres (average 1.07) and the junctional epithelium (average 0.97), which totals an average of 2.04 mm.

During placement of restorative margins, an additional 1-2 mm of sound structure coronal to the epithelial attachment is needed, hence the minimum distance between the alveolar crest and the restorative margin should be 3-4 mm (to allow a gingival sulcus of approx. 1 mm) This can be determined radio graphically.

Impinging on this width by a restoration will trigger loss of bone and epithelial attachment. An interproximal encroachment leads to osseous crater that will be unmanageable from oral hygiene standpoint.

The width of keratinized gingiva needed to maintain periodontal health and unaltered attachment levels is a controversial topic. The keratinized gingiva provides a protective fibre barrier against inflammation and attachment loss.

There is increasing evidence that periodontal health can be maintained in areas with minimal zones of keratinized gingiva as long as the patient can maintain the area and there are no restorations in the area of the gingival margin. When restorative procedures enter the gingival crevice, a minimum of 5 mm of keratinized tissue is required (2 mm of free gingiva and 3 mm of attached gingiva).

There are situations where we are forced to take the restorative margins sub-gingivally. When such conditions as fracture and caries force us to violate biologic width, periodontal surgery or crown lengthening procedures should be performed. Orthodontic extrusion or forced eruption is useful in the premolar and anterior region, where gingival width is important. When indicated, this procedure is to be completed before the restoration.

To conclude, the points to remember are:-

· To preserve biologic width and prevent attachment loss, restorative margins should be at least 3-4 mm from crestal bone.

· Sub gingival restorative margins should be properly contoured

· An adequate band of keratinized tissue is mandatory.

· Plan the treatment carefully and consider the benefits that periodontal surgery and orthodontic extrusion can provide.

Source: Internet

Preparation of Root Canal

Aim: Elimination of microorganisms and their products from the root canal system and to shape it to receive an inert filling material.

Microorganisms are found to a variable degree up to the apical foramen in three modes:

1. as a suspension in the root canal

2. colonizing the canal walls and

3. colonizing the dentinal tubules.

It is impossible to completely sterilize the root canal system due to its complex structure. Luckily for us, removal of the bulk of the microorganisms and their products brings about periradicular healing due to an altered or less pathogenic residual flora.

The aim of canal preparation in vital teeth is to remove pulp tissue, which may become necrotic and infected.

A combined action of mechanical and chemical cleansing is effective in root canal preparation.

Working length determination

From the preoperative radiograph, estimate the average length of the tooth. Select a reproducible coronal reference point. It should not be part of a portion of tooth or restorative material that is likely to break off. Choose a file that is large enough to be visible on the radiograph (at least size 10).

Insert a file into the root canal, 1-2 mm short of the estimated length and take a parallel view radiograph. An average distance of 1 mm short of the radiographic apex is widely accepted as a reasonable estimate of the terminal portion of the canal. Remember, at times, this may be inaccurate by up to 3 mm.(see fig 1)

Relationship between apical foramen, root tip and apical constrication. A=Root apex B= Apical constriction

C= Root canal D=Cementum E=Dentin F=Apical foramen

In cases of narrow root tips, and when there is apical root resorption, working length should be shortened more than 1 mm. In the former, it is because perforation may occur when the root is prepared to a wider diameter(See Fig2) and in the latter, the canal exit may be ‘blunderbuss’ shaped that can allow extrusion of endodontic materials.

If the tip of the file is short of the radiographic apex by 1 mm, accept it as the working length. If the file is longer than the radiographic apex, measure the distance between the file tip and a point 1 mm short of the radiographic apex. Subtract this figure from the length of the diagnostic file to get the working length.

If the distance between the file tip and the radiographic apex is greater than 1 mm, subtract 1 mm from this distance and add it to the length of the diagnostic file to get the working length.

If you have reasonable number of endodontic cases, it is worth investing in an electronic apex locator. Many reliable brands are available in the market. I have been using J Morita’s Root ZX to my fullest satisfaction. Endoseries 5 had covered electronic apex locators.

Once you have determined the working length, it is of utmost importance to restrict instrumentation to this length. Avoid displacement of the stops.

The width of the taper to which the canal should be prepared should be based on personal preference and individual clinical experience. If they allow adequate cleaning and obturation, narrowly tapered preparations are more desirable, as they do not compromise root strength and avoid strip perforations.

Mechanical preparation refers to controlled removal of dentin by manipulating root canal instruments. Factors influencing the amount and pattern of dentin removal are,

-design and sharpness of the cutting edge

-the manner in which it is manipulated

-the force applied and

-the operator’s skill.

Operator’s skill is influenced by the ability to discriminate tactile feedback from the instrument and the ability to manipulate the instruments in a controlled way according to the mental image of a three dimensional shape of the root canal system.

You can either rotate the root canal instruments (clockwise and withdraw) or used in a push- pull filing motion to remove dentin. Or you can combine the two (ream and file) by 45-90 degree clockwise movements to engage the dentin and straight pull withdrawal to cut the engaged dentin.

Due to uncontrolled dentin removal, errors in canal preparation viz., ledging, zipping and transportation of apical foramen may result. A reliable method to reduce uncontrolled forces is to use flexible files such as Flex-R, Flexo-file, Nickel-Titanium etc.,

To avoid procedural errors resulting in loss of working length, use smaller instruments (No. 20 or smaller) for sufficient time until the larger sizes pass in the canal without force. You can even create intermediate files as suggested by Weine, by trimming 1 m from the tip of the file and rounding off sharp edges on a diamond nail file. This way you can convert #10, 15& 20 files to # 12,17 and 22

Ref:

1. Christopher J R Stock, Gulabivala K, Walker T, Goodman JR: Endodontics, 2nd Ed. NewYork, Mosby- Wolfe p 97-144, 1995.

2. Weine FS: Endodontic Therapy 3rd Ed. Mosby, 1982

Emergency In A Dental Clinic

Ideally the following equipments and drugs should be present in a dental clinic:

• Pulse Oximeter

• Portable defibrillator (incorporating ECG print-out

• Portable oxygen delivery system

• Ambu bag (self-inflating with valve and mask)

• Oro-pharyngeal airways (sizes 1, 2 and 3)

• Cricothyroid puncture needles

• High volume aspiration with suction catheters and Yankauer sucker

• Disposable syringes (2, 5, 10 and 20 ml sizes)

• Needles (19, 21 and 23 gauge) and butterflies

• Tourniquet, sphygmomanometer and stethoscope

• Venous access cannulae (‘venflons’ 16 and 22 gauge)

• IV infusion sets/ Microdrip sets

• ‘BM sticks’ (for rapid assessment of blood sugar levels)

EMERGENCY DRUGS

• Oxygen

• Adrenaline injection (1:1000 or lmg/1 ml)

• Hydrocortisone injection

• Anti-histamine injection (e.g. chlorpheniramine tablets 4 mg, injection 10 mg/ml) Avil 2 ml

• Diazepam ( 5 mg/ml)

• Glucose (10% solution) for injection, and powder for oral use

• Glucagon injection (ideally) 1 mg

• Atropine injection (100 fig/mi)

• Aminophylline amp

• Deriphylline inj

• Colloid solution for infusion (e.g. Haemaccel 500 ml).

• Gelfoam, Hemolock

• Tab sorbitrate 20 Mg for sublingual use

• Tab. Nifedipine (sublingual)

• Ringer's Lactate- 5% Dextrose- Normal saline

FAINTING

Dentistry predisposes to fainting (syncope or vaso-vagal episode) due to fear, pain, unusual sights and smells, anxiety, fatigue and fasting. It is the commonest cause of loss of consciousness in dental practice. It is common in young men. Treat patients supine whenever possible.

Symptoms and signs

• Light-headed feeling (often with nausea) • warm, sweaty

feeling • Pallor * skin cool and moist to touch • bradycardia (with a thready, low volume pulse) • loss of consciousness and collapse with resultant rapid, full pulse.

Differential diagnosis

• Hypoglycaemia • steroid insufficiency • drug reaction • Cerebrovascular accident • myocardial infarction • heart block or other causes of bradycardia • early epileptic seizure.

Management

• Place patient in a semi recumbent postion

• Increase ventilation (ask pt. to take deep breaths)

• Determine bradycardia by taking pulse at major vessel.

• Loosen clothing and open windows.

• Establish verbal encouragement of patient and administer glucose orally.

• If patient continues to go to drowsy state make him smell/inhale aromatic salt (spirit of Ammonia)

• Delay dental treatment unless urgent.

If recovery is slow or delayed — reconsider diagnosis.

• Check blood sugar and, if low, administer IV glucose.

• If bradycardia persists, give atropine IV incremental

doses of 100 micro mili|g.

Maintain airway and administer oxygen. If hypotensive, consider steroid insufficiency administer IV hydrocortisone. Seek urgent medical attention.

dentalabfraction

Dealing with hypersensitivity of teeth with non-carious cervical lesions is a difficult task। These were thought to be erosion- abrasion lesions. It was Grippo, who originated the term ‘abfraction’, in 1991 to describe the pathologic loss of tooth enamel and dentin caused by biomechanical loading of forces.


Up until now, research into the causes of abfractions seems to be divided into two camps- those who argue for tooth brushes and other artificial forces as the cause and those researchers who point to internal physiological sources as the culprit. The latter argument, though not providing a complete explanation, does offer a significant clue to the real cause of this troubling phenomenon.

The earliest review in English, of the erosion –abrasion issue as it relates to tooth brushing and dentifrices seem to be the original works of WD Miller in the late 1880s and early 1900s. He believed that erosion was caused by weak acids or gritty tooth powders, or by both, assisted by the toothbrush.

In 1950, SC Miller suggested that traumatic and lateral forces by the tongue, lips and cheeks were contributors to gingival recession. Glickman, in 1965 proposed that susceptibility to recession was influenced by many factors such as the position of teeth in the arch, the angle of the root in the bone, and the mesio-distal curvature of the tooth surfaces.

Yettram et al found that abfraction could occur even gingival to the margin of crowns and that the amount of load placed on the teeth was the key factor. Finally, in 1984, Lee and Eakle described lateral forces as the cause of the tooth structure breakdown. Grippo had stated that the forces could be static, such as those produced by swallowing and clenching, or cyclic, as in those generated during chewing action.

The abfractive lesions are caused by flexure and ultimate material fatigue of susceptible teeth at locations away from the point of loading. The breakdown is dependent on the magnitude, duration, frequency and location of the forces.

Clinical Implications

A dentist who restores an abfraction lesion to relieve hypersensitivity of the patient’s tooth should be aware that to prevent this restoration from falling out, one needs to treat the cause of the abfraction before restoring it.

If a tooth has an abfraction, the occlusal loading on the tooth can be tested in centric occlusion and in excursive movements with occlusal marking paper. There is a good chance that the tooth with abfraction will have a heavy marking on one of the inclines of a cusp. This damaging lateral force produces stress lines in the tooth and results in tooth break down.

If the patient does not have heavy markings on the inclines, then he may have abnormal activity of the tongue. A ‘normal swallow’ is a swallow that is initiated with the tip of the tongue starting in the area of the maxillary anterior papilla, that continues with a peristaltic like action, pressing up against the roof of the maxilla, forcing the bolus posteriorly and finally down the throat. The tip of the tongue remains in the area of the anterior papilla during the entire swallow. Any other swallow is considered to be the result of abnormal tongue activity. The tongue should not press with any force into, against or between any teeth during the swallow.

Examine the area of abfraction with the patient’s teeth together and lips slightly parted. Check whether the tongue is pushing into the tooth, or if salivary bubbles are visible coming between the interproximal spaces. Tongue thrusting can be the result of large tongues or obstructed airways.

When lateral tongue forces traumatize the teeth or if the key requirements of occlusion are not met, a series of deleterious events can occur

-Abfractions

-Sensitive teeth

-Loosening of teeth

-Excessive wear of teeth

-Change in alignment of teeth

-Bone breakdown and bone loss

-Broken or destroyed restorations

-Non-bacterial, non- plaque related gingival recession

-Opening of contacts.

If during lateral excursions there is cuspid rise, the loading forces of the excursive movement will be directed into the cuspid. Abfractions are frequently found in cases where malaligned cuspids cause initial lateral guidance forces to be exerted on the lingual incline of the buccal cusp of the maxillary bicuspid. Abfractions are also found in patients with slight anterior open bites. Here also, the guidance is coming from the bicuspids, rather than the cuspid.

The common clinical occurrence of class V restoration failure is often blamed on inadequate moisture control. Study by Rees J S and PH Jacobson shows that the presence of a class I restoration, especially an amalgam restoration on the same tooth can influence the prognosis of a class V restoration, They found that the presence of an occlusal restoration increased cuspal movements, which in turn increased the shear forces around the buccal class V cavity.

Lastly, it is important to remember that your cavity preparation and restoration of a class I cavity may cause an abfraction. It is well established that cavity preparation weakens a tooth, resulting in more cuspal movement under occlusal load. In a study by Rees J, under an eccentric 100 N occlusal load, a premolar with an occlusal amalgam restoration showed peak tensile and shear stresses in the buccal cervical region that were in excess of the known failure stress for enamel. Increases in the cavity depth of the occlusal amalgam restorations were found to increase cervical stress more than increases in cavity width.

Here is the last word, the weakening effect of an occlusal cavity preparation may contribute to the development of non carious cervical tooth loss.