Prosthodontics, Preparation for NBDE Part II

  • Category: Prosthodontics, General Dentistry
  • Aim: Revising for NBDE Part II
  • Questions: 25
  • Hint: No
  • Mutiple Opportunites: No
  • Time Limit: No
  • Answer Explaining: Yes

Prosthodontics

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Question 1

A patient is unhappy with the esthetics of an anterior metal-ceramic crown, complaining that it looks too opaque in the incisal third. The reason for this is most likely____.

A
Using the incorrect opaque porcelain shade.
B
Inadequate vacuum during porcelain firing.
C
Not masking the metal well enough with the opaque.
D
The tooth was prepared in a single facial plane.
Question 1 Explanation: 
D. D is the best answer because generally it is the dentist’s fault and not the technician’s, incorrect opaque may influence the resultant shade. Inadequate vacuum will affect the esthetics. If the opaque does not mask well, the metal result is a grey appearance or lower value in the restoration.
Question 2
Metamerism invariably involves ____.
A
A color difference between two objects under one or more illuminant(s)
B
One object having a lower chroma than another
C
One object having a lower lightness than another
D
A significant color change of one object as it moves from one illuminant to another
Question 2 Explanation: 
A. Metamerism is the phenomenon where a color match under a lighting condition appears different under a different lighting condition.
Question 3
The component of an RDP that is spoon-shaped and slightly inclined apically from the marginal ridge of a tooth is the ____.
A
Indirect retainer
B
Minor connector
C
Rest
D
Lingual bar
Question 3 Explanation: 
C. The rest should be spoon-shaped and is slightly inclined apically from the marginal ridge of the abutment tooth. It should restore the occlusal morphology of the tooth and not interfere with the normal existing occlusion.
Question 4
When soldering a fixed partial denture, what is the effect of flux when heated on the area to be soldered?
A
To remove oxides from the metal surface.
B
To displace metal ions from the area.
C
To change the composition of the alloy.
D
To reduce the surface tension of the metal.
Question 4 Explanation: 
A. The soldering flux used with gold alloys is usually borax glass (Na2B407), because of its affinity for copper oxides. Flux is applied to a metal surface to remove or prevent oxide formation. With an oxide-free surface, the solder wets the surface freely and spreads over the metal surface.
Question 5

Which of the following are factors associated with bone loss?

A
Initial implant instability.
B
Excessive occlusal force.
C
Inadequate hygiene.
D
Inadequate prosthesis fit.
E
All of the above.
Question 5 Explanation: 
E. Bone resorption around dental implants can be caused by inadequate oral hygiene, premature loading, and repeated overloading. If an implant- supported framework does not fit passively, the implant is placed under constant force. If signifi¬cant compressive forces are placed on the inter¬facial bone, these can lead to implant failure.
Question 6
Which may be a consequence of occlusal trauma on implants?
A
Widening of the periodontal ligament.
B
Soft-tissue sore area around the tooth.
C
Bone loss.
D
All of the above.
Question 6 Explanation: 
C. Bone loss is usually seen on the most coronal aspect of the implant in the form of a wedge. There is no periodontal ligament on Implants, so there is no feeling of soreness.
Question 7
Which is the purpose of adjusting the occlusion in dentures?
A
To obtain balanced occlusion.
B
To stabilize dentures.
C
To obtain even occlusal contacts.
D
All of the above.
Question 7 Explanation: 
D. Occlusal adjustment of dentures should be done with the premise of obtaining even occlusal contacts with balanced occlusion in order to stabilize the dentures during function.
Question 8
An endodontically treated tooth was restored with a cast post-and-core and a metal-ceramic crown. Three months later, the patient complains of pain, especially on biting. Radiographic findings and tooth mobility tests are normal. The most probable cause of pain is ____.
A
A loose crown
B
Psychosomatic
C
A vertical root fracture
D
A premature eccentric contact
Question 8 Explanation: 
C. Usually, vertical fractures will refer pain when biting. In this case, the patient had recent endodontic treatment and there is no periapical lesion to indicate that is due to inadequate root canal therapy. There is no sign that the crown is loose, no premature contact, and no mobility.
Question 9
In a Kennedy Class I arch in which all molars and the first premolar are missing and the rest of the teeth have good periodontal supportthe preferred choice of treatment is ____.
A
A removable partial denture replacing all missing teeth
B
A fixed dental prosthesis replacing the missing premolar and a removable partial denture replacing the molars
C
Implant supported crowns replacing the first premolars and a removable partial denture replacing the molars
D
A and B are preferred choice of treatment over C.
E
B and C are preferred choice of treatment over A.
Question 9 Explanation: 
E. A fixed dental prosthesis replacing the first bicuspids improves the prognosis of the second bicuspids when placing a removable dental prosthesis, implants would also improve the prognosis by not leaving the second bicuspid standing alone and acting as a cantilever when in function with the removable prosthesis.
Question 10
The minor connector for a mandibular distal extension base should extend posteriorly about ____.
A
Two-thirds the length of the edentulous ridge
B
Half the length of the edentulous ridge
C
One-third the length of the edentulous ridge
D
As long as possible
Question 10 Explanation: 
A. The minor connector for the mandibular distal extension base should extend posteriorly about two thirds the length of the edentulous ridge; this adds strength to the denture base.
Question 11
Excessive monomer added to acrylic resin will result in ____.
A
Increased expansion
B
Increased heat generation
C
Increased shrinkage
D
Increased strength
Question 11 Explanation: 
C. Using more monomer than needed will cause increased shrinkage. The more monomer used, the less expansion, less heat, and reduced strength will be produced.
Question 12
A radiolucency near the apex of tooth #28 is seen radiographically. The tooth is asymptomatic and does not have caries or periodontal problems. Which is most likely the cause of the radiolucency?
A
Submandibular fossa.
B
Periapical granuloma.
C
Complex compound odontoma.
D
Mental foramen.
Question 12 Explanation: 
D. The tooth does not exhibit any pathology to indicate that the radiolucency is derived from the tooth. The mental foramen can appear on the apex, depending on the direction of the x-ray beam.
Question 13
Which are characteristics of a major connector that contribute to health and well-being?
A
It is rigid and provides unification of the arch stability.
B
It does not substantially alter the natural contour of the lingual surface of the mandibular alveolar ridge or the palatal vault.
C
It contributes to the support of the prosthesis.
D
All of the above.
E
Only A and B.
Question 13 Explanation: 
D. Rigidity is provided by cross-arch stability through the principle of broad distribution of stress. The major connector should not alter dramatically the contours of the supporting structures, and it should contribute to the support of the prosthesis.
Question 14
When does a fixed dental prosthesis (FDP), which was cast in one piece, need to be sectioned?
A
When a cantilever pontic is used.
B
When the fit cannot be achieved or verified with a one-piece cast.
C
When single crowns are adjacent to the FDP.
D
Always, in order to achieve a good fit.
Question 14 Explanation: 
B. Common reasons for a FDP not to fit in one piece are lack of parallelism between the abutments and distortion of the wax pattern during removal from the dies. In any of these cases, the frame¬work may not fit in the prepared abutment teeth and must be sectioned between one of the connectors between the pontic and retainer to fit the two pieces individually, and a solder record must be made to solder the pieces.
Question 15

The impression material that is mainly composed of sodium or potassium salts of alginic acid is ____.

A
Polyether
B
Irreversible hydrocolloid
C
Polyvinyl siloxane
D
Polysulfide
Question 15 Explanation: 
B. Irreversible hydrocolloid (IH) or alginate is the material of choice to produce diagnostic casts. Its composition is mainly sodium or potassium salts of alginic acid. They react chemically with calcium sulfate to produce insoluble calcium alginate.
Question 16
Which of the following is tree of an occlusal rest for a removable partial denture?
  1. One-third facial lingual width of the tooth
  2. 1.5 mm deep for base metal
  3. 2.0 mm lafoiolingual width of the tooth
  4. Floor inclines apically toward the center of the tooth

A
All of the above
B
1,3, and 4
C
1, 2, and 4
D
3 and 4
Question 16 Explanation: 
C. Rests are critical for the health of the soft tissues underlying the denture resin basis and the minor and major connectors. It should prevent tilting action and should direct forces through the long axis of the abutment tooth. In order to function as specified, an occlusal rest should have a rounded (semicircular) outline form, be one-third the facial lingual width of the tooth, one-half the width between cusps, and at least 1.5 mm deep for base metal. The rest floor inclines apically toward the center of the tooth and the angle formed with the vertical minor connector should be less than 90 degrees.
Question 17

Which of the following statements is(are) true concerning the evaluation of the occlusion on a cast restoration?

A
The restoration is in proper occlusion if it holds shim stock.
B
The restoration is in proper occlusion if the adjacent teeth hold shim stock.
C
The restoration is in proper occlusion when articulating paper marks multiple points of contact on the restoration.
D
A, B, and C.
E
None of the above.
Question 17 Explanation: 
D. When checking the occlusion of a cast restoration, mylar paper or shim stock is a very accu¬rate method for testing occlusal contacts. The procedure is to check with the mylar paper before placing the restoration in the teeth adja¬cent to the tooth to be restored and the oppos¬ing side. Place the restoration and check whether the same occlusal contacts are main¬tained on the tested teeth. When all teeth, including the one being restored, hold the mylar paper upon occluding and even, articulating markings are present, then occlusion contacts are correct.
Question 18
A dentist is preparing all maxillary anterior teeth for metal-ceramic crowns. Which of the following procedures is necessary in order to preserve and restore anterior guidance?
A
Protrusive record.
B
Template for provisional restorations.
C
Custom incisal guide table.
D
Interocclusal record in centric relation.
Question 18 Explanation: 
C. Anterior guidance must be preserved by means of construction of a custom incisal guide table, espe¬cially when restorative procedures change the surfaces of anterior teeth that guide the mandible in excursive (lateral, protrusive) movements.
Question 19
For optimum esthetics when setting maxillary denture teeth, the incisal edges of the maxillary incisors should follow the ____.
A
Lower lips during smiling
B
Upper lips during smiling
C
Lower lips when relaxed
D
Upper lips when relaxed
Question 19 Explanation: 
A. Maxillary teeth should contact the wet dry lip line when fricative sounds f, u, and ph are made. These sounds help to determine the position of the incisal edges of the maxillary anterior teeth.
Question 20
A complete denture patient presents with angular cheilitis. A review of recent medical examination revealed that vitamin deficiency is not a factor. A possible predisposing factor is ____.
A
Excessive vertical dimension of occlusion
B
A closed or insufficient vertical dimension of occlusion
C
Improper balance of the occlusion
D
Poor contour of the denture base
Question 20 Explanation: 
B. A closed or Insufficient vertical dimension of occlusion is thought to be one predisposing con¬dition for angular cheilitis, which usually Is asso¬ciated with Candida albicans. Improperly balanced occlusion or poor contour of the den¬ture base are not predisposing conditions for angular cheilitis.
Question 21
For an occlusal appliance used for muscle relaxation to be effective, the condyles must be located in their most stable position from a musculoskeletal perspective. This is ____.
A
Centric occlusion
B
At the vertical dimension of rest
C
Centric relation
D
Maximum intercuspal position
Question 21 Explanation: 
C. The condyles should be in centric relation, which is defined as “the maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the condyle-disk complex in the anterior-superior position against the shapes of the articular emi¬nences.” (Glossary of Prosthodontic Terms, JProsthetic Dent 94(l):21-22, 2005.)
Question 22
A diagnostic wax-up is indicated when ____.
A
Re-establishing anterior guidance
B
A provisional fixed prosthesis is to be fabricated
C
Uncertainty exists regarding esthetics
D
All of the above
Question 22 Explanation: 
D. It is recommended that any time there is a question regarding the treatment outcome involving a prosthetic device, or the need to produce tem¬plates for provisional restorations that reproduce a desired form of teeth, a diagnostic wax~up should be generated.
Question 23
Which of the following is (are) uses for the surveyor?
A
To aid in the placement of an intracoronal retainer.
B
To block out a master cast.
C
To measure a specific depth of an undercut.
D
All of the above.
E
Only A and B are correct.
Question 23 Explanation: 
D. The surveyor is used for surveying a diagnostic cast and to measure a specific depth of undercut. It also helps to determine the most desirable path of placement for a removable partial denture. It identifies bony areas that may need to be surgi¬cally removed because they interfere during insertion of the RDP. It is also used to survey crowns, place intracoronal retainers, machine or mill cast restorations, and survey and block out a master cast before constructing an RDP.
Question 24
Each of the following is a feature of papillary hyperplasia except one. Which one is not true?
A
It is a proliferative bone disease
B
It can be caused by wearing the dentures at night
C
It can be caused by poor oral hygiene
D
It can be caused by an ill-fitting denture
Question 24 Explanation: 
A. Paget’s disease of bone is a bone disease characterized by bone resorption followed by attempts at bone repair involving proliferation leading to bone deformities, its etiology Is unknown and It occasionally involves the maxilla and mandible. Papillary hyperplasia is character¬ized by multiple papillary projections of the epithelium caused by local irritation, poor-fitting denture, poor oral hygiene, and leaving dentures In all day and night.
Question 25

Which of the following is the single most important predictor of clinical success of a cast post and core?

A
Amount of remaining coronal tooth structure.
B
Post length.
C
Post diameter.
D
Positive horizontal stop.
Question 25 Explanation: 
A. The length, canal enlargement, and a finish line for the post are unimportant if there is no sound remaining coronal tooth structure to get a ferrule of the final restoration.
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