The SLSA program is based on current, referenced literature and consists of 40 questions, answers, rationales and references. Answers appear in the following issue at the end of each quiz.
Dentists who complete the 15 question quiz in the November, 2009 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.
QUESTION 29
Which of the following provides for the best improvement in the papillary bleeding index (PBI)
A. Tooth brushing and rinsing with 0.06% chlorhexidine and 0.025% fluoride.
B. Tooth brushing and rinsing with 0.1% cetylpyridinium chloride and 0.025% fluoride.
C. Tooth brushing and flossing.
D. Tooth brushing only.
E. None of the above.
Rationale
A study was conducted to evaluate the efficacy of two mouthrinses in reducing interdental plaque and gingivitis compared to dental floss. Inclusion criteria were such that no subjects with good oral hygiene under normal conditions were included in the study. Subjects were randomly assigned to four groups: 1) brushing and rinsing (0.06% chlorhexidine and 0.025% fluoride); 2) brushing and rinsing (0.1% cetylpyridinium chloride and 0.025% fluoride; 3) tooth brushing and flossing; 4) toothbrushing only. At baseline, the modified proximal plaque index (MPPI) and papillary bleeding index (PBI) were recorded. Thereafter, subjects had to brush with a silica based toothpaste in the usual manner learning, over an eight week period. Additionally, test groups had to rinse once a day or floss once daily. After four and eight weeks, indices were recorded again and improvements calculated. Reductions for all indices were found in all groups. However, with respect to the MPPI, mouthrinse groups performed better than the control and floss groups which was statistically significant. The PBI showed no difference between the groups.
REFERENCE
1. Zimmer, S., Kolbe, C., Kaiser, G. et al. Clinical efficacy of flossing versus use of antimicrobial rinses. J Periodontol 77 : 1380 -1385, 2006.
QUESTION 30
Pacemakers correct bradycardia.
Defibrillators correct cardiac arrhythmias.
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
Pacemakers correct bradycardia or abnormal heart rate by stimulating (pacing) the heart. Defibrillators function to correct cardiac arrhythmias and many of these have incorporated pacing functions that allow them to treat patients with both bradycardias and tachycardias.
REFERENCE
1. Wilson, B. L., Broberg, C., Baumgartner, JC et al. Safety of electronic apex locators and pulp testers in patients with implanted cardiac pacemakers or caridioverter/defibrillators. JOE 32 : 847 -852, 2006.
QUESTION 31
For an inferior alveolar nerve block slow injection of anaesthetic is more effective than fast.
Molar teeth are shown to have deeper pulp anaesthe- sia than premolars after a slow inferior dental nerve block injection.
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
Many factors can influence the success of an inferior alveolar nerve block. A randomized double blind crossover design study was carried out to compare the efficacy of slow and rapid nerve block in securing pulpal anaesthesia in the mandibular teeth. After negative aspiration 2 ml of 2% lidocaine with 1 : 80,000 epinephrine was given, either slowly over 60 seconds or rapidly over 15 seconds. To blind the patient to the procedure, the needle remained in place for 45 seconds before depositing the solution in the case of rapid injection. Pulp sensitivity was determined with an electric pulp tester using the first molar, first or second premolar and lateral incisor. Pulp testing was then repeated every two minutes for the first 10 minutes and then at five minute intervals for 45 minutes post injection. Comfort of injection, onset of pulpal anaesthesia and depth of anaesthesia were assessed. Results showed that there was less discomfort associated with a slow injection which was statistically significant. Slow injection produced more episodes of no pulp response than rapid injection in first molars, premolars and lateral incisors. The onset of pulpal anaesthesia was faster in molars and premolars compared to lateral incisors although no difference was found between molars and premolars. Dentists should be aware that slow injection results in less tissue damage, faster onset of anaesthesia, deeper anaesthesia and is more comfortable for the patient.
REFERENCE
1. Kanaa, M. D., Meechan, J. G., Corbett, I. P. et al. Speed of injection influences efficacy of inferior alveolar nerve blocks: a double-blind randomized control trial in volunteers. JOE 32 : 919 -922, 2006.
QUESTION 32
The “hybrid layer” is a mesh of dentine collagen created by acid decalcification.
2% chlorhexidine digluconate reduces the speed of degradation of the “hybrid layer”.
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
Adhesion to dentine by hydrophilic resins occurs through infiltration and polymerization of the resin within the “collagen mesh” exposed by acid decalcification. This forms the so called “hybrid layer”. Such adhesion degrades over time. The degradation is initiated by metalloproteinase enzymes (MPP) found in the saliva and dentine. Chlorhexidine acts as an inhibitor of MPP activity. A recent study has also shown that 2% chlorhexidine digluconate (Bisco cavity cleanser) applied after acid etching reduces the rate of degradation of the hybrid layer.
REFERENCE
1. Brackett, W. W., Tay, F. R., Brackett, M. G. et al. The effect of chlorhexidine on dentin hybrid layers in VIVO. Operative Dentistry 32, 107-111, 2007.
Answers to the July 2009 SLSA questions:
25. E
26. A
27. C
28. C