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Learning Assessment (October 01, 2000)

October 1, 2000
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, 2000 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 37

Which of the following drugs will potentiate anticoagulation in a patient taking Coumadin?

1. Acetylsalicylic acid

2. Ketoconazole

3. Ibuprofen

4. Phenobarbital

A. 1, 2, 3

B. 1 and 3

C. 2 and 4

D. 4 only

E. All of the above

Rationale:

A number of drugs interact with Coumadin. Metronidazole, erythromycin, fluconozale and ketoconazole potentiate the effect of Coumadin by the inhibition of hepatic microsomal enzymes. Salicylates and other non-steroidal anti-inflammatory drugs should be avoided in patients on anticoagulant therapy, since they affect platelet function as well as coagulation and therefore increase the risk of spontaneous bleeding. Barbiturates, on the other hand, reduce the effect of Coumadin due to induction of hepatic microsomal enzymes. A decrease in the level of anticoagulation increases the risk of thromboembolism.

REFERENCE:

Herman, W.W., Konzelman, J.L., Sutley, S.M. Current perspectives on dental patients receiving coumarin anticoagulant therapy. JADA 128:327-335, 1997.

QUESTION 38

In the use of electronic dental anaesthesia (EDA), non-noxious electrical stimuli are applied to the skin, and pain perception is suppressed because

1. small afferent nerve fibres are excited.

2. large afferent nerve fibres are excited.

3. they cause release of B-endorphin.

4. large nerve fibres carry the major stimuli and block the pain stimulus.

A. 1, 2, 3

B. 1 and 3

C. 2 and 4

D. 4 only

E. All of the above

Rationale:

Pain messages are initiated in the body by nociceptors (nerve endings which respond to noxious stimuli).

Methionine, a naturally occurring analgesic substance, is an enkephalin first isolated from the pituitary. However, the analgesic effect is transient as it is very easily inactivated by peptidases in the brain. B-endorphin, another naturally occurring analgesic substance, is more potent with a longer duration of action.

Responses of the trigeminal brain stem neurons to noxious stimuli can be suppressed by a non-noxious electrical stimulus that excites large afferent nerve fibres. Such action is explained by the Gate Control theory of pain. Large fibres carry input such as pressure, whereas smaller fibres give input of specific or diffuse pain. When a non-noxious electrical stimulus is applied, large fibres are excited to the suppression of the smaller pain carrying fibres. Electronic anaesthesia and TENS (transcutaneous electrical nerve stimulation) are examples of this modality of pain control.

REFERENCES:

1. Joseph, C.E. and Malamed, S. Pain modulation. California D.A.J. June 1987:19-20.

3. Pain – Clinical updates International Association for the Study of Pain, Vol. 1, Issue 3, September 1993.

QUESTION 39

Plaque associated with the margin of a restoration will cause bone to resorb if the location of the plaque from the bone is

A. 2.7 mm

B. 3.3 mm

C. 3.9 mm

D. 4.5 mm

Rationale:

It has been demonstrated that, if the plaque front is within 2.7 mm of bone, the bone will resorb. Therefore, the biologic width (epithelial and connective tissue attachment) must not be violated. Only in those cases where esthetics is of prime importance should a margin be placed subgingivally.

A recent review supports the use of supragingival finish lines for fixed prosthodontic restorations. Three configurations were studied, viz. shoulder bevelled, shoulder, and chamfer. The finish line of a bevelled shoulder showed the least amount of marginal opening after seating the restoration. This, in turn, presented the smallest exposure of luting cement. Since the luting cement roughness acts as a base for microbial growth and the microbes in turn exude exotoxins, endotoxins, and metabolic byproducts, the superficial periodontal tissues and particularly the gingiva become irritated and inflamed.

In addition to margin design, impression procedures and temporary provisional resin materials can also contribute to an acute inflammatory reaction in the superficial tissues which can result in tissue shrinkage with an unpredictable free gingival margin location. The inflammation could resolve or continue as a chronic condition postoperatively and lead to loss of periodontal attachment and alveolar bone.

REFERENCE:

Bowley, J.F., Payne, J.B., Stockhill, J.W. Management of the gingival sulcus in fixed prosthodontics: A literature review and treatment protocol. Compendium 19:154-162, 1998.

QUESTION 40

Chlorhexidine chips used in the treatment of adult periodontitis will

1. reduce pocket depth.

2. reduce bleeding on probing.

3. assist in determining the periodontal status of the patient.

4. induce drug resistant bacteria.

A. 1, 2, 3

B. 1 and 3

C. 2 and 4

D. 4 only

E. All of the above

Rationale:

A recent review compared the advantages and disadvantages of local drug therapy with scaling and root planing in the treatment of adult periodontitis. The drugs investigated were tetracycline fibres, metronidazole dental gels, chlorhexidine chips, minocycline dental gel, and doxycycline polymer. Drug therapy using dental gels and chips is easier to perform technically than root planing, is quicker, and does not remove cementum, which can result in root sensitivity.

A similar reduction in pocket depth as well as a similar reduction in redness and bleeding on probing was reported for both modalities. Arguments can be made against local drug therapy in favour of scaling and root planing, since the latter avoid the induction of drug resistant bacteria, especially where local antibiotics are involved. However, where antiseptic chips and gels are used, this is not a factor.

Root planing will disrupt and remove biofilms of bacteria, as well as calculus and cementum, all of which may be impervious to local drugs.

Argument is made for local drug therapy to be adjunctive to conventional therapy, and for local drug treatment to be reserved for non-responding sites, or in locations where instrumentation is difficult.

There is a suggestion in the review that the use of local antiseptic agents will be beneficial to the general dentist in determining the periodontal status of the patient prior to or instead of referring to a specialist.

REFERENCES:

1. Greenstein, G., Polson, A., The role of local drug delivery in the management of periodontal diseases: a comprehensive review. J Periodontol 69:507-20, 1998.

2. Magnusson, I., Local delivery of antimicrobial agents for the tratment of periodontitis. Compendium 19:953-64, 1998.

Answers to the September 2000 SLSA questions:

33. D 34. B 35. E 36. C

Answers to the October 2000 SLSA questions:

37. A 38. C 39. A 40. A


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