All Ceramic Restorations

 # Which of the following is the BEST way to avoid porcelain failure in all-ceramic restorations?

A. Rounded angles of the preparation

B. Minimal occlusal forces

C. Porcelain is 3.5mm thick

D. Porcelain is not more than 0.5mm thick 

The correct answer is A. Rounded angles of the preparation.

All ceramic restorations should include rounded angles in the tooth preparation in order to reduce stress concentration along these areas. Sharp angles within tooth preparations are areas where stress is concentrated, and may cause fracturing.

Porcelain thickness is also an important factor in its fracture toughness. All porcelain crowns should have a minimum thickness of 1mm circumferentially and about 1.5mm along the occlusal/ incisal to

achieve strength (Not including the framework of the restoration).

Proper case selection and occlusal load analysis is also an important factor in preventing failure of an all ceramic restoration. 

Excess height of the posterior palatal seal

 # Excess height of the posterior palatal seal of a complete maxillary denture will usually result in which of the following?

A. Gagging

B. Increased retention

C. A tingling or tickling sensation

D. Unseating of the denture

The correct answer is D. Unseating of the denture.

Over contouring or excessive beading of the posterior palatal seal causes too much pressure to be exerted on the palatal tissues resulting in the unseating of upper dentures.

The posterior palatal seal is typically placed approximately on the vibrating line between the hard and soft palate and provides a physiologically acceptable tissue pressure within the compressible portion of the soft palate to attain retention and peripheral seal.

Over extending the coverage of seal will cause gaggling and painful swallowing for the part of the patient. 

MCQs on Removable Partial Dentures : Introduction and Classification

# Class IV Kennedy classification is:
A. Bilateral edentulous area located posterior to the remaining natural teeth
B. Unilateral edentulous area located posterior to the remaining natural teeth
C. Unilateral edentulous area with natural teeth remaining both anterior and posterior to it
D. A single but bilateral (crossing the midline) edentulous area located anterior to the remaining natural teeth

# A distal extension partial denture receives its support :
A. From terminal abutments
B. Equally from abutments and the residual ridges
C. Mostly from residual ridge
D. Exclusively from residual ridge