Oral Health Group
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Self Learning Assessment 2007 (July 01, 2007)

July 1, 2007
by Oral Health


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, 2007 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 25

Ideal requirement(s) for a single anterior tooth maxillary implant is/are

1. a length of 12-16mm

2. 2mm interproximal bone on either side of the implant.

3. at least 1mm facial bone thickness.

4. thick gingiva.

A. 1, 2, 3

B. 1 and 3

C. 2 and 4

D. 4 only

E. All of the above

Rationale

There must be sufficient bone and soft tissue volume to allow the implant to be positioned for a predictable esthetic outcome. The periodontal status has to provide optimal health. A thick periodontal tissue biotype with thick, flattened osseous plates gives resistance to recession and is therefore to be preferred to thin gingiva. Coupled with radiographic examination, the osseous contour and gingival thickness should be evaluated under local anaesthesia by measuring to the periosteum with an endodontic probe and a rubber marker. In determining the optimal tooth position for function and esthetics a diagnostic set up with a denture tooth should be made with suitable wax up of hard and soft tissue contours. A vacuum formed matrix of this diagnostic aid will help in surgical placement of the implant. It is important to determine whether the patient can open the mouth 35mm or more to allow the surgeon sufficient drilling access in placing the implant in the anterior maxilla. The single tooth implant requires adequate interproximal bone. A 4mm diameter implant requires 8mm of space, i.e. 2mm of bone either side of the implant. There must also be at least 1mm of facial and lingual cortical bone. Implant length is recommended at 12-16mm. Where bone and or gingival thickness is inadequate bone or gingival grafting must be considered.

REFERENCES

1.Stanford, C.M.: Application of oral implants to the general dental practice. JADA 136: 1092-1100, 2005.

2.Misch, C.E., D’Alessio, R., Misch-Dietsh, F.: Maxillary partial anodontia and implant dentistry. Oral Health, August 45-57, 2005.

QUESTION 26

Posterior crossbite in the primary dentition can

1. be self correcting.

2. have a genetic background.

3. lead to TMJ dysfunction.

4. cause facial deformity.

A. 1, 2, 3

B. 1 and 3

C. 2 and 4

D. 4 only

E. All of the above

Rationale

Posterior crossbites in the primary dentition commonly arise as a result of a narrow maxilla caused by genetics, environmental influences or a combination of both. Significant maxillary constriction is associated with sucking habits continuing beyond 24 months of age. Nasal obstruction causing mouth breathing also leads to posterior crossbite.

Up to 45% of posterior crossbites in the primary dentition are self-correcting and there is no evidence to support routine correction of crossbites at this stage as opposed to treatment in the mixed dentition. However, a crossbite in the primary dentition with a functional displacement of the mandible requires immediate attention since the lack of correction can lead to long-term detrimental consequences. These include TMJ dysfunction and abnormal facial esthetics. Selective grinding of premature contacts of the primary teeth is a clinically proven treatment for posterior crossbite correction, but some treatment may require symmetric expansion of the maxillary arch, removal of occlusal interferences and elimination of the shift. Early diagnosis of unilateral crossbites is essential to achieve the benefits of treatment.

REFERENCES

1.Malandris, M., Mahoney, E .K. : Etiology, diagnosis and treatment of Posterior Crossbite in the primary dentition. Oral Health, January 27-45, 2005.

2.Kennedy, D.B., Osepchook, M.: Unilateral Posterior Crossbite with Mandibular Shift: A Review. J Can Dent Assoc 71:569–573,2005.

QUESTION 27

In endodontic therapy, which of the following has/have a direct impact on outcomes?

1. Underfilling

2. Root canal infection

3. Overfilling

4. Preoperative periradicular lesions

A. 1, 2, 3

B. 1 and 3

C. 2 and 4

D. 4 only

E. All of the above

Rationale

Procedural errors in endodontics are not in themselves a direct cause of treatment failure.

Instead it is the presence of pathogens in the incompletely treated canal system that is to blame. Studies have shown that although factors such as pulpal and periradicular status, underfilling, overfilling, root perforations, and ledge formation affect the prognosis, only two factors-root canal infection and preoperative periradicular lesions have a direct impact on outcomes. Underfilling often occurs as a result of incomplete instrumentation or from the creation of a ledge during the mechanical phase. Incomplete instrumentation will occur because of inaccurate measurement of the working length or from poor irrigation leading to canal blockage by dentin filings. Ledge formation is mainly the result of inadequate straight-line access to the apical portion of the canal, and from poor irrigation and lubrication. It also results from skipping the sequential file sizes and packing of debris into the apical portion of the canal. Studies indicate that teeth with underfillings have a poorer prognosis (68% success) compared to teeth with flush fillings (94% success) and overfillings (70% success).

REFERENCE

1.Lin, L.M., Rosenberg, P.A., Lin, J.: Do procedural errors cause endodontic treatment failure? JADA136:187-193, 2005.

QUESTION 28

Mercury vapour is released daily from an amalgam surface at a level of 0.534 g.

Permissible release of mercury vapour for children and women of childbearing age on a daily basis is up to 300g.

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

It would require 1680 years to release all the combined mercury of a typical amalgam restoration weighing 0.65 g. Only 0.534g of mercury vapour is released per day from an amalgam surface. Guidelines set for young children and women of childbearing age indicate that the maximal permissible level is 300g/day. To reach the maximum exposure limit, an individual would have to have 490 amalgam surfaces in the mouth, which is a practical impossibility.

REFERENCE

1.Jones, D.W.: Putting dental mercury pollution in perspective. Br Dent J 197:175-177,2004.

Answers to the June 2007 SLSA questions:

21. A

22. D

23. D

24. E


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