Oral Health Group
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Self Learning Assessment 2005 (May 01, 2005)

May 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 17

In restorations, which of the following will affect esthetics?

1. Type of preparation edge.

2. Health status of the gingiva.

3. Contour of the restoration.

4. Dental material used.

A. 1, 2, 3D. 4 only

B. 1 and 3E. All of the above

C. 2 and 4

Rationale

The health status of the gingiva, the contour of the tissue, as well as the papillary height interproximally have a major impact on esthetics. It is important to control any present gingivitis before starting preparation of restorations and to avoid soft tissue trauma during work and by any temporary restorations placed. All damage will lead to recession and compromise esthetics.

Supragingival finish lines are advocated for gold crowns and a chamfer edge is favoured. This reduces the exposure of luting cement to a minimum and retention of plaque with resultant gingival irritation is lessened. In the anterior maxilla, with the esthetic demands, subgingival finish lines are required. However, certain biological principles must be satisfied. There must be a minimum 3mm space between the restorative margin and the crestal bone. If this distance is encroached upon, it will initiate marginal gingivitis and bone loss. Overcontoured restorations at the gingival third will also result in marginal gingivitis. Undercontouring denies support of the surrounding gingival tissue, resulting in “black holes” between teeth.

When dental materials are considered, porcelain being non-plaque retentive is best. However, luting cement used in veneers and crowns of porcelain can irritate and retain microbia. Metal-based crowns have esthetic problems because of the dark shadow of the metal through the gingiva, especially when the gingiva is thin. This would contraindicate their use. In anterior composite restorations, it is recently advocated that, after removal of caries and placement of retention, the margins of the preparation be chamfer finished just within the sulcus and interproximal areas. The restoration is then completed using a Belvedere matrix.

REFERENCES

1.Goodlin, R. Gingival aesthetics: a critical factor in smile design. Oral Health. April 10-27, 2003.

2.Turner, W.E. The concealed margin restoration: anterior margin placement for optimum aesthetics. Oral Health. April 77-86, 2003.

QUESTION 18

Only one nerve (inferior alveolar) carries sensation from the mandibular teeth.

Three nerves (anterior, middle, and posterior superior alveolar) always carry sensation from the maxillary teeth.

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

There are numerous studies to support the concept of accessory innervation of the mandibular teeth. Branches of the mylohyoid nerve which enter the mandible through “retromental foramina” of the lingual cortical bone in the vicinity of the second premolar can carry sensation from the premolar, cuspid and incisor teeth and even the first molar. The incidence of this accessory innervation to mandibular teeth is 60 percent. As the mylohyoid nerve may arise five to 23mm above the mandibular foramen, it may not be blocked simultaneously with the inferior alveolar nerve. The mylohyoid branches may be blocked in the region of the retromental foramina. Branches of the mandibular division or of the inferior alveolar can arise high in the infratemporal fossa and travel to the base of the coronoid process to enter the mandible, innervating second and third molars. It is also possible to have branches of the mandibular division or of its inferior alveolar or buccal branches, which enter the mandible in the retromolar fossa area to supply first and/or third molars. These branches may be anaesthetized by infiltrating in the retromolar fossa area.

In the maxilla, it is more common to find three nerves: the anterior superior alveolar which innervates the incisors and the cuspids, the middle superior alveolar which innervates the premolars and the mesiobuccal root of the first molar and the posterior superior alveolar which innervates the remainder of the molars. In patients where the middle superior alveolar nerve is absent, the posterior superior alveolar nerve innervates the premolar region and infiltration in the region of the molar achieves anaesthesia of the premolars.

REFERENCE

Blanton, P.L., Jeske, A.H. Misconceptions involving dental local anaesthesia. Part I: Anatomy. Texas Dental Journal 119:296-314, 2002.

QUESTION 19

When used in endodontics, Mineral Trioxide Aggregate

1. sets in moisture.

2. is biocompatible.

3. seals perforations more effectively than amalgam.

4. seals perforations more effectively than super EBA.

A. 1, 2, 3D. 4 only

B. 1 and 3E. All of the above

C. 2 and 4

Rationale

Mineral Trioxide Aggregate (MTA) is a material which appears to have all of the characteristics of an ideal cement to seal communication between the root canal system and the oral cavity (mechanical and carious pulp exposures) and between the root canal system and the periodontium (iatrogenic perforations, open apices, resorbed apices, root-end preparations). MTA is an endodontic cement that is extremely biocompatible, capable of stimulating healing and osteogenesis. It is hydrophilic and sets in the presence of moisture. MTA is a powder that consists of fine trioxides and other hydrophilic particles. Hydration of the powder results in the formation of a colloidal gel with a pH of 12.5. MTA powder mixes readily with sterile water and has a working time of approximately five minutes and a setting time of four hours. Final restorations should only be completed after setting in order to avoid disturbance of the material. In terms of biocompatibility, it has been shown that there is no cytotoxicity when MTA comes in contact with fibroblasts and osteoblasts. Dentin bridges form when it is used for pulp capping. Studies have shown growth of cementum, periodontal ligament and bone when MTA was used to seal perforations or when used as a retrofilling material. The marginal adaptation and sealing properties of MTA are far superior to amalgam, IRM and Super EBA and because of its hydrophilic properties, its setting is not affected adversely by the presence of moisture or blood.

REFERENCE

Castellucci, A. The use of Mineral Trioxide Aggregate in clinical and surgical endodontics. Dentistry Today. 74-81. March 2003.

QUESTION 20

Which of the following is the least effective in reducing oral malodor?

A. Zinc ions

B. Chlorhexidine

C. Cetylpyridinium chloride

D. All have the same effect.

Rationale

Oral malodor is closely associated with measured levels of volatile sulfur compounds (VSC) in mouth air as measured by gas chromatography. Certain metal ions, e.g., zinc, inhibit the formation of VSC and thereby reduce or inhibit oral malodor. It is believed that zinc ions interact with the sulfur in the substrate or in the precursors of VSC, forming insoluble sulfides. Cationic antibacterial agents such as chlorhexidine and cetylpyridinium chloride also have a certain effect on VSC production, presumably operating through a non-specific antibacterial action.

In a recent controlled study, the effectiveness of different concentrations of these three agents against VSC was observed. Zinc acetate solution (one percent) had an excellent anti-VSC effect throughou
t the three-hour test period, although the metallic taste was somewhat unpleasant. If developed commercially, this taste could be overcome by masking. Chlorhexidine solution (0.2%) was also very effective as an anti-VSC agent. Zinc acetate gave faster relief from malodor than chlorhexidine, but chlorhexidine lasted longer. Cetylpyridinium chloride clearly had the least anti-VSC effect.

REFERENCE

Young, A., Jonski, G., Rlla, G. Inhibition of orally produced volatile sulfur compounds by zinc, chlorhexidine or cetylpyridinium chloride-effect of concentration. Eur J Oral Sci 111400-404, 2003.

Correction

The answer to Question 2 is A. (OH, January, 2005)

Answers to the April 2005 SLSA Questions

13. E

14. D

15. E

16. D


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