Rubber dams and cavity designs

Question 1

Explain the principles of cavity design

Answer 1

· Access:
Must be conservative

· Outline form:
The area of hole is based primarily on the extent of caries. Remove all unsupported enamel, but also focus on maintaining tooth structure

· Resistance form:
Ensure that fracture of restoration is prevented even when masticatory stresses are present. To do this, the depth needs to be good, the floor must be at a right angle to the line of stress, and internal walls/line angles straight. Weak cusps should be removed and restored.

• Retention form:
  Cavity should stay in place.

· Convenience form
Cavity is a suitable size and shape for restoration

· Removal of remaining affected caries:
…

· Completion of cavo-surface angle:
Should be a right angle, with no bevels.

· Cavity debridement:
Remove any remaining debris from cavity prep

Question 2

Why are rubber dams used?

Answer 2

• Protects the patient from accidentally inhaling or swallowing debris 
• Protects the tooth from contamination 
• Provides the moisture control needed 
• Improves access 
* Provides better visibility

Question 3

What are contraindications of rubber dams?

Answer 3

• Patient objection
• Partially erupted teeth
• Malpositioned teeth
• Mouth breathers
• Allergy

Question 4

What’s the role of the dental frame?

Answer 4

• Stabilizes and stretches the dam so it fits tightly around the teeth
• Aids in retracting soft tissues through keeping the dam taut

Question 5

List punching sizes for rubber dams

Answer 5

1: lower incisors
2: upper incisors
3: canines, premolars, primary first molars
4: upper molars, primary second molars
5: lower molars

Question 6

How do you select clamps?

Answer 6

The clamp should provide a four-point contact with the tooth surfaces. This provides stability, or resistance to rotation or dislodgment for the clamp

Question 7

List steps of applying clamp

Answer 7

1. Always apply LA onto gingiva
2. Apply floss ligature onto the holes next to jaws of clamps. Ensure the ligatures are away from the side of the hole near the jaws of the clamps
3. Bow of clamp should be positioned on distal part of the tooth being clamped
4. It can be difficult to apply clamp then rubber dam in areas such as the back of the mouth, so keep this in mind when choosing which order to place the clamp