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Learning Assessment (May 01, 2001)

May 1, 2001
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, 2001 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 17

Since biofilms in dental unit waterlines can harbour potential pathogenic organisms, disinfection of the lines becomes an essential, particularly when treating a patient who is immunocompromised. Which of the following disinfectants is/are effective in preventing pathogen transmission from biofilm?

1.Sodium hypochlorite (bleach)

2.Gluteraldehyde

3.Isopropanol

4.Iodophors

A.1, 2, 3D.4 only

B.1 and 3E.All of the above

C.2 and 4

Rationale:

Although recommendations to flush all waterlines for two minutes or more at the start of a clinic day and before each patient visit will reduce numbers of bacteria from the waterlines by 96-98%, this nevertheless, does not dislodge biofilm which is a perfect medium for bacterial colonization. Flushing merely washes off bacteria, which reside on the surface of the biofilm.

A recent investigation with disinfectant compounds such as the above has found that disinfection of waterlines will inhibit bacterial growth in the biofilm and effluent for up to 15 days. Common microbes rapidly recolonize because of the presence of the biofilm matrix. Daily treatment of waterlines with the disinfectants mentioned will be effective in keeping bacteria within the lines below cultivable levels, but the disinfectants will not disrupt the biofilm matrix and rapid recolonization occurs when disinfectant treatment is discontinued. However, the disinfectants mentioned will prevent pathogen transmission from the biofilm, and it is the pathogenic bacteria, which are of concern in crossinfection.

A build-up of the disinfectant chemicals in the waterlines may cause toxic reaction in some patients.

Another important point to note relates to the effects of waterline antimicrobials on the bond strength of adhesive restorations. A recent study (2000) has shown that all the antimicrobials tested caused a reduction of bond strength to dentine. Therefore, clinicians are warned to follow manufacturers’ instructions carefully when using antimicrobial solutions and dentine bonding agents.

REFERENCES:

1.Meiller, T.F., DePaola, L.G., Kelley, J.I., et al. Dental unit waterlines: biofilms, disinfection and recurrence. JADA 130:65-72, 1999.

2.Roberts, H.W., Karpay, R.I., and Mills, S.E. Dental unit waterline antimicrobial agents’ effect on dentine bond strength. JADA 131:179-183, 2000.

3. Barbeau, J., Gauthier, C., Payment P. Biofilms, infectious agents, and dental unit waterlines: a review. Can J Microbiol 44:1019-28, 1998.

QUESTION 18

In the placement of adhesive restorations, dessication of the dentine results in postoperative sensitivity.

In primer application, the minerals removed from dentine by acid conditioning are replaced by “plastic.”

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:

Dessication of dentine causes postoperative sensitivity. The successful outcome of adhesive restorations is dependent upon the application technique and this in turn relies on the understanding of the solvent used in the primer. Three types of solvents are identified to dissolve the primer hydrophilic monomers: water, alcohol, and acetone. The purpose of the primer is to saturate with hydrophilic monomers the demineralized zone of dentine caused by acid etching. In addition, the primer plugs the dentinal tubules with the monomers. If not completely saturated, postoperative sensitivity is likely to result and therefore underpriming must be avoided. The primer should replace the mineral removed from the dentine by acid conditioning and cause a layer of “plastic” to form, i.e., hybridization.

To apply a primer correctly, the clinician must select an application method which best suits the primer’s solvent. Water-based primers by reducing the possibilities of dentine dehydration, are the least technique-sensitive. Alcohol-based primers are next, and acetone-based primers have the highest risk of overdrying the dentine.

To avoid postoperative sensitivity due to dehydration, after the matrix is placed for a restoration, you should

confine the acid etchant to and within the cavo surface margins

wash off the acid

withdraw excess moisture with high volume suction — do not blow air into the cavity

apply primer and inspect for a surface sheen which indicates that the tubules have been plugged by plastic (hybridized).

reapply primer if surface sheen is not apparent.

REFERENCE

Jackson, R., Soll, J. The importance of technique in eliminating postoperative sensitivity. Oral Health, July 71-75, 1999.

QUESTION 19

When planning the placement of a metal ceramic crown in the anterior maxilla, which of the following is/are essential to provide a predictable aesthetic result with no gingival recession?

1. Healthy gingivae

2. No gingival damage during tooth preparation

3. Use of a well adapted and contoured provisional restoration

4. Firm placement of retraction cord to control the bleeding

A.1, 2, 3D.4 only

B.1 and 3E.All of the above

C.2 and 4

Rationale:

Donovan (1998) states that, at the time of margin placement and impression taking, one of the most important factors in predictability of result is to ensure that the gingival tissues are free of any inflammation. It is essential that, in tooth preparation, as little damage as possible to the gingival tissue occurs. Gentle pre-packing of the gingival sulcus with retraction cord prior to margin cutting will prevent such injury.

Magne (1999) supported this technique with retraction cord using minimal pressure and trauma to respect the biological width of the periodontium. Well-adapted and contoured provisional restorations between visits are further demanded in the soft tissue care.

The concept of aesthetic width is introduced whilst accepting that the biologic width describes location and dimension of the connective tissue attachment. The aesthetic width is accommodated in the design of the prosthetic framework. New concepts in metal ceramics have introduced better aesthetic results through reduced metal framework and extended porcelain shoulders. The resultant restorations through such extended shoulders permit interaction of light with other anterior teeth and their support tissues.

REFERENCES

1. Donovan, T.E., Cho, G.C. Soft tissue management with metal-ceramic and all ceramic restorations. J Calif Dent Assoc 26(2): 107-112. 1998.

2. Magne, P., Magne, M., Belser, U. The esthetic width in fixed prosthodontics. Oral Health, Nov. 25-38. 1999.

QUESTION 20

An adult patient has a controlled periodontal condition and excellent oral hygiene. Which of the following procedures would give further benefit to the periodontal status?

1. Extrusive movement of a molar with a furcation involvement

2. Extrusive movement of a tooth with one- or two-wall bony pockets

3. Intrusive movement to provide new attachment gain

4. Lingual movement of a labially inclined incisor with dehiscence.

A.1, 2, 3D.4 only

B.1 and 3E.All of the above

C.2 and 4

Rationale:

A recent review (1999) confirms that, in a patient as described above, extrusive movement of a tooth with one- or two-wall bony pockets will lead to favourable coronal positioning of an intact connective tissue attachment and shallowing of the bony defect. Such movement and benefits are seen in uprighting tipped molars. When a furcation involvement is present, such extrusive orthodontic movement tends to increase the periodontal problem.

No evidence is given that, with intrusive movement of a tooth, new attachment gain is predictable, unless the intrusion is supplemented by a barrier membrane procedure.

Where a dehiscence is present in a labially inclined incisor, lingual movement of the tooth can result in new bone formation as well as increased gingival thickness of the affected labial tissue. Thus, not only is tooth position contributing to improved aesthetics but also to a more acceptable gingival contour.

REFERENCE

Saunders, N.L. Evidence-based care in orthodontics and periodontics: a review of the literature. JADA. 130: 521-527, 1999.

Answers for April 2001 SLSA questions:

13. A 14. A 15. E 16. D

Funding for the SLSA program has been provided by:


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