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. 

Abutment teeth in a fixed partial denture

 # What is the primary reason why dentists splint adjacent abutment teeth in a fixed partial denture?

A. Improve spacing mesiodistally

B. Stabilize abutment teeth

C. Improve embrasure contours

D. Improve the distribution of the occlusal load 

The correct answer is D. Improve the distribution of the occlusal load 

Abutment teeth are included in fixed partial dentures to provide retention and help disperse the occlusal load placed on the restoration.

Abutment teeth provides support and stability to the pontic.

Abutment teeth allows better distribution of the occlusal forces acting on all teeth and pontic in the fixed partial denture.

Packing acrylic resin into the denture flasks

# After packing acrylic resin into the denture flasks, one should wait to cure the resin to:

A. Assure full flow of acrylic into the denture mold

B. Allow the monomer to reach all acrylic polymer

C. Allow for pressure to be equalized between the acrylic and flask

D. Make sure temperature equilibrium exists between the flask and acrylic 

The correct answer is D. Make sure temperature equilibrium exists between the flask and acrylic

Allowing the dental flask packed with acrylic to remain under the bench press until equilibrium in temperature is achieved will give enough time for the acrylic to achieve better monomer-polymer interaction and create stronger chemical bond.

The curing of resin should be uniformly completed to lessen any chances of distortion before and during the time the flask is immersed in a water bath.

 

Packing the acrylic during the rubbery stage

# When fabricating dentures, what would be the most likely outcome if the lab compressed/packed the acrylic during the rubbery stage?

A. Higher porosity than normal

B. A lot of extra resin being attached to the denture that will take a long time to trim

C. Incomplete picking up of anatomical details

D. The denture would have an increased VDO 

The correct answer is C. Incomplete picking up of anatomical details

Packing and compressing acrylic during denture fabrication should be done in its doughy stage.

The doughy stage is the ideal for packing acrylic resin because it is the moment when acrylic is most packable and workable.

The rubbery stage of acrylic denotes the start of the setting when heat is released from the setting acrylic.

Rubbery acrylic also has a tendency to revert back to its original position regardless of the forces applied to it during packing, resulting in incomplete packing.

VDO (Vertical Dimension of Occlusion) is synonymous with OVD (Occlusal Vertical Dimension) and is the relationship of the maxilla and mandible when the teeth are in maximum intercuspation. 

 

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. 

Flabby maxillary anterior ridge

# Which of the following is associated with a flabby maxillary anterior ridge under a complete denture?

A. Retained mandibular anterior teeth

B. A "V" shaped ridge

C. A "U" shaped ridge

D. A patient with Class Il occlusion

E. Osteoporosis 

The correct answer is A. Retained mandibular anterior teeth.

Combination syndrome is a condition that usually occurs when retained mandibular

anterior teeth opposes a maxillary complete denture.

In combination syndrome, the anterior aspect of upper maxillary ridge becomes highly resorbed and flabby due to the biting force against its natural tooth antagonist.

Since the occlusal force of a natural tooth is stronger than the force of a denture supported by an alveolar ridge, the area under pressure will exhibit higher resorption pattern than the rest of the denture.

Pterygomandibular raphe is a tendon between

# Pterygomandibular raphe is a tendon between which of the following muscles?

A. Masseter and medial pterygoid

B. Anterior belly of the digastric and Buccinator

C. Buccinator and Superior constrictor

D. Buccinator and Masseter

The correct answer is C. Buccinator and Superior constrictor.

Pterygomandibular raphe acts as a tendon between the buccinator and superior Constrictor muscle. It is a landmark used often for the identification of the pterygomandibular space for the administration of an inferior alveolar nerve block.

The injecting needle pierces the buccinator muscle to inject the local anesthetic solution in the pterygomandibular space.