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Self Learning Assessment 2005 (September 01, 2005)

September 1, 2005
by Oral Health


The SLSA program is based on current, referenced literature and consists of 40 questions, answers, rationales and references. Answers appear at the end of each quiz.

Dentists who complete the 15 question quiz in the November, 2005 issue of Oral Health may be eligible to receive continuing education points. The names and license numbers of all who complete the quiz will be forwarded to their respective provincial licensing authorities.

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QUESTION 33

The bleaching of teeth with carbamide peroxide

1. causes hydrogen peroxide to become ionized.

2. is enhanced by exposure to UV light.

3. works by conversion of carbon rings to chains in the interprismatic substance of the enamel.

4. is faster the higher the concentration.

A. 1, 2, 3

B. 1 and 3

C. 2 and 4

D. 4 only

E. All of the above

Rationale

Tooth bleaching is an efficient, safe and effective method for removal of most intrinsic and extrinsic stains. In the presence of saliva, 10% carbamide peroxide releases 3% hydrogen peroxide and 7% urea. Hydrogen peroxide becomes ionized and free radicals diffuse through the interprismatic substance of the enamel to convert pigmented carbon rings to chains, which are lighter in colour. If higher concentrations of carbamide peroxide are used, the whitening process speeds up. However, the acidic property of the bleaching agents causes changes in the mineral content of the enamel and the higher the concentration the greater the change. With the 10% carbamide peroxide, an initial decrease in enamel microhardness is recorded, followed by an increase due to remineralization from saliva. It has been shown that light will augment the effect of the peroxide agent. Although pulpal sensitivity of teeth can occur, the problem can be offset by use of a 5% solution of potassium nitrate applied to the teeth prior to the whitening process.

A further study on tooth whitening has shown that ultraviolet light, halogen light or laser will augment the effect of the peroxide agent, increasing the speed of the bleaching process.

REFERENCES

1.Basting, R.T., Rodriguez, A.L., Serra, M.C. The effects of seven carbamide peroxide bleaching agents on enamel microhardness over time. JADA 134:1355-1342, 2003.

2.Tavares, M., Stultz, J., Newman, M., et al. Light augments tooth whitening with peroxide. JADA 134:167-175, 2003.

QUESTION 34

In endodontics, flushing of the canal apex with an end-venting needle and sodium hypochlorite (NaOCI) results in

1. removal of organic debris.

2. disinfection.

3. edema of the apical tissues.

4. deep penetration of the dentinal tubules.

A. 1, 2, 3

B. 1 and 3

C. 2 and 4

D. 4 only

E. All of the above

Rationale

End venting irrigation needles have a reputation for injecting solutions under pressure, resulting in pain, edema and haematoma following extrusion of NaOCI into the soft tissues. It is further shown that deeper penetration of the canal system results from use of side venting irrigation needles with diameters as small as 0.032 inch.

Hydrogen peroxide as an irrigant has been long out of favour. It does not deal with organic debris in the manner of NaOCI, which removes pulpal remnants, organic debris and predentin. Furthermore, chlorine derivatives disinfect and are bactericidal against Gram-negative bacteria.

Although 2% chlorhexidine will remove debris and disinfect as well as 1.25% NaOCI, recent work shows that 5.25% NaOCI is best, especially when heated to 60-70C prior to use, as this enhances the chemical activity.

REFERENCES

1.Serota, K.S., Nahmias, Y., Barnett, F., et al. Predictable endodontic success: the apical control zone. Oral Health. Oct:75-89, 2003.

2.Wolcott, J. Single visit vs. Multiple visit endodontics. Which is best? Compendium 23:232-234, 2002.

QUESTION 35

Prodromal symptoms of Herpes Simplex Labialis are countered with Acyclovir 200mg two times daily.

Recurrent Herpes Simplex Labialis results from infection in the neural ganglia.

A. The first statement is true, the second is false.

B. The first statement is false, the second is true.

C. Both statements are true.

D. Both statements are false.

Rationale

Recurrences of herpetic simplex labialis (HSL), manifesting as cold sores, can continue throughout life. After primary infection with herpes simplex virus 1, the virus ascends the sensory nerve axons and establishes chronic latent infection in various neural ganglia (trigeminal, facial and vagus), as well as in tissues such as the epithelium of the lips. The dormant virus awaits a “trigger” to reactivate it. Triggers may include exposure to sun, psychological stress, onset of menses, illness and trauma, e.g., dental treatment. Some patients experience prodromal symptoms, such as burning, tingling, itching at the site where the lesion later occurs, whereas in others the lesion occurs immediately after the trigger. Currently available therapies have not been particularly effective in reducing symptoms or promoting healing once the lesion has formed.

For adults with established lesions, systemic or topical agents are recommended. Acyclovir 400mg twice daily, or Famciclovir 500mg three times daily can be prescribed. Topical agents such as 5% Acyclovir cream five times daily or 1% Penciclovir cream every two hours may be used alone or in conjunction with the systemic agent. Where dental treatment is the trigger, you should prescribe, 24 hours before treatment, Acyclovir 400mg twice daily, or Famciclovir 500mg twice daily.

REFERENCES

1.Spruance, S.L., Nett, R., Marbury, T., et al. Acyclovir cream for the treatment of herpes simplex labialis: results of two randomized, double-blind, vehicle-controlled, multicenter clinical trials. Antimicrob Agents Chemother; 46(7) 2238-43, 2002.

2.Raborn, G.W., Grace, M.G.A. Recurrent herpes simplex labialis: selected therapeutic options. J Can Dent Assoc. 69:498-503, 2003.

QUESTION 36

Compared to conventional resin-based composites, packable composites are

A. less fracture-resistant.

B. harder.

C. stronger.

D. have greater polymerization shrinkage.

E. none of the above.

Rationale

Packable or high-density resin-based composites have been developed to give the clinician some of the properties of amalgam for restorations in posterior teeth of the Class II type. Although argument is made that faster placement and tighter interproximal contacts can be made in restorations with the packable material, a twelve-month study did not support this. Physical properties of wear resistance, hardness, fracture resistance and general strength, as well as polymerisation shrinkage, were equivalent to conventional resin-based composites.

REFERENCES

1.Perdigo, J. Geraldeli, S., Hodges, J.S. Total-etch versus self-etch adhesive: effect on post-operative sensitivity. JADA 134:1621-1629, 2003.

2.Yip, K. H.-K., Poon, B.K.M., Chu, F.C.S., et al. Clinical evaluation of packable and conventional hybrid resin-based composites for posterior restorations in permanent teeth. JADA. 134:1581-1589, 2003.

Answers to the August 2005 SLSA Questions

29. B

30. E

31. A

32. E


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