Following are the examples of indirect retainers EXCEPT:

 # Following are the examples of indirect retainers except:

A. Occlusal rest

B. Auxillary occlusal rest

C. Canine rest

D. Continuous bar retainers and linguoplates

The correct answer is A. Occlusal rest.

Continuous clasp: “A metal bar usually resting on the lingual surface of teeth to aid in their

stabilization and to act as an indirect retainer”-GPT.

Canine rest

• If the mesial marginal ridge of the first premolar is close to the fulcrum line, canine rest is used.

• This design can be modified by placing the minor connector anterior to the canine. The minor connector hooks back into the cingular rest seat. This increases the efficacy of the indirect retainer (due to increase in distance from the fulcrum line).

Types of Indirect Retainers

The most commonly used type of indirect retainer is a rest connected to a minor connector. In some cases indirect retention is obtained without a rest.

Types:

1. Auxiliary occlusal rest

2. Canine extension from the occlusal rest

3. Canine rest

4. Continuous bar retainers and linguoplates

5. Modification areas

6. Rugae support

7. Direct indirect retention

8. Indirect retention from major connectors

Reference: Nallaswamy, 2nd Edition, Page 375

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Main advantage of the palatal plate major connector is:

 # Main advantage of the palatal plate major connector is:

A. Thick metal plate

B. Thin metal plate

C. Surface irregularity of plate

D. Corrugated plate

The correct answer is D>B. 

Advantages:

• Intimate contact with the palatal tissues over a large area provides good retention due to the presence of interfacial surface tension.

• Provides good vertical support.

• Numerous surface corrugations due to very thin metal provide a very natural feel.

Reference: Nallaswamy, 2nd Edition, Page No 331

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Class IV Kennedy classification is:

 # Class IV Kennedy classification is:

A. A single edentulous area located anterior to remaining natural teeth

B. A single edentulous area present anterior to the canine

C. A single edentulous area present bilaterally on both halves of the jaw

D. A single edentulous area crossing the midline located anterior to the remaining natural teeth

The correct answer is D. A single edentulous area crossing the midline located anterior to the remaining natural teeth

Class IV: Single, bilateral edentulous area located anterior to the remaining natural teeth. This is a single edentulous area, which crosses the midline of the arch, with remaining teeth present only posterior to it. 

Reference: Nallaswamy, 2nd edition, Page no: 272

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Main purpose of tilting the cast in surveying is to:

 # The main purpose of tilting the cast in surveying is to:

A. Locate the undercuts

B. Locate the line of contour

C. Provide the most desirable path of placement

D. Aid in designing

The correct answer is C. Provide the most desirable path of placement.

Tilting the Cast and Altering the Path of Insertion

Some areas of the tooth may form an undercut only when viewed in a different angle. In such cases, the cast can be tilted on a surveyor so that the path of insertion of the denture is altered and the undercuts are present in relation to the new path of insertion.

The cast can be tilted only to a maximum of 10°, beyond which it is not advisable because the patient will require excessive mouth opening for insertion and removal. Generally, tilting the cast to obtain a retentive undercut is the least sorted procedure and is not advisable in the presence of other alternatives.

Ref: Nallaswamy, 2nd Edition Page No: 402

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Most common reason for midline fracture of the maxillary denture

 # The most common reason for midline fracture of the maxillary denture is due to: 

A. Alignment of posterior teeth too far buccally

B. Lack of strength of the material itself

C. Thin palatal portion of the denture

D. Internal porosity which is common in palatal portion

The correct answer is A. Alignment of posterior teeth too far buccally.

Denture base resins are subjected to a variety of stresses during function:

• Midline fractures of dentures during function are considered a flexural fatigue failure due to cyclical deformation of the base during function. This is usually more evident in ill fitting or poorly designed dentures.

• Impact fracture may result from patients accidentally dropping the dentures.

Ref: Boucher's Prosthodontics, 13th Edition Page 137 

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Zero degree cusp teeth are preferred over anatomic teeth:

 # Zero degree cusp teeth are preferred over anatomic teeth:

A. When muscles of mastication is very powerful

B. Diabetic patients

C. Patients with well developed residual ridge

D. Patients with very less retention and stability

The correct answer is D. Patients with very less retention and stability.

Zero degree teeth are defined as, “Artificial posterior teeth having no cusp angles in relation to the horizontal occlusal surfaces” - GPT.

Advantages

• In patients with bruxism non-anatomic teeth decrease the forces acting on the basal tissues.

• Greater range of movements is possible.

• In patients with neuromuscular disorders where accurate jaw relation cannot be recorded, cuspless teeth are preferred.

• In cases with highly resorbed ridge, cuspless teeth are preferred as they do not get locked and displace the denture during lateral movements.

Disadvantages

• Flat occlusal surfaces and artificial contours give an unaesthetic appearance.

• Masticatory efficiency is less.

• Balanced occlusion cannot be obtained.

• Occlusion is in two dimensions, whereas the mandibular movement is in three dimensions.

• Any attempt to correct these teeth by occlusal grinding will decrease their efficiency.

Reference: Nallaswamy, 2nd Edition, Page No 9

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Metal margin is preferred over ceramic margin in metal ceramic restoration:

 # Metal margin is preferred over ceramic margin in metal ceramic restoration:

A. Margins are easy to prepare for metal during tooth preparation

B. Tooth preparation is going to be more conservative

C. Only when margin is subgingival

D. Marginal adaptation is better in metal margin rather than ceramic margin

The correct answer is C. Only when margin is subgingival.

Metal ceramics: These materials require extensive tooth reduction. The junction between the metal

and the ceramic is very unaesthetic. For aesthetic reasons the margins of the restoration is placed

subgingivally which frequently leads to periodontal problems. 

Reference: Nallaswamy, 2nd Edition, Page 495

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