Operative Dentistry, Preparation for NBDE Part II

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

Operative Dentistry

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Question 1

Which of the following statements regarding caries risk assessment is correct?

A
The presence of restorations is a good indicator of current caries activity.
B
The presence of restorations is a good indicator of past caries activity.
C
The presence of dental plaque is a good indicator of current caries activity.
D
The presence of pit-and-fissure sealants is a good indicator of current caries activity.
Question 1 Explanation: 
B. A restored tooth indicates potential past carious activity but not current activity. Plaque presence does not necessarily indicate caries presence and sealants are used for preventive purposes, not caries treatment.
Question 2
All of the following statements about slot- retained complex amalgams are true except _____.
A
Slots should be 1.5 mm in depth.
B
Slots should be 1 mm or more in length.
C
Slots may be segmented or continuous.
D
Slots should be placed at least 0.5 mm inside the DEJ.
Question 2 Explanation: 
A. The longer a slot, the better. They should be inside the DEJ and prepared with an inverted cone bur to a depth of 1 mm.
Question 3
In comparison to amalgam restoration, composite restorations are _____.
A
Stronger.
B
More technique-sensitive.
C
More resistant to occlusal forces.
D
Not indicated for Class II restorations.
Question 3 Explanation: 
B. Composite restorations are more technique- sensitive than amalgam restorations because the bonding process is very specific (requiring exact, correct usage of the various materials and an isolated, noncontaminated field), and the insertion and contouring of composites are more demanding and time-consuming. Composites are not stronger than amalgam and have similar wear resistance compared to amal¬gams. Composites are indicated for Class II restorations.
Question 4
Restoration of an appropriate proximal contact results in all of the following except________ .
A
Reduction/elimination of food impaction at the interdental papilla.
B
Provide appropriate space for the interdental papilla.
C
Provide increased retention form for the restoration.
D
Maintenance of the proper occlusal relationship.
Question 4 Explanation: 
C. Proper proximal contacts reduce the potential for food impaction, thereby preserving the health of the underlying soft tissue. A missing proximal contact may result in tooth movement that will have an adverse effect on the occlusal relationship of the tooth. Having a correct con¬tact does not enhance the retentive properties of the restorative material.
Question 5
Choose the incorrect statement about Class V amalgam restorations.          
A
The outline form is usually kidney- or crescent­shaped.
B
Because the mesial, distal, gingival, and incisal walls of the tooth preparation are perpendicular to the external tooth surface, they usually diverge facially.
C
Using four comer coves instead of two full-length grooves conserves dentin near the pulp and may reduce the possibility of a mechanical pulp exposure.
D
If the outline form approaches an existing proximal restoration, it is better to leave a thin section of tooth structure between the two restorations (< 1 mm) than to join the restorations.
Question 5 Explanation: 
D. Because of the typical shape of a carious lesion in the cervical area, the resulting restoration is kidney- or crescent-shaped and the extensions are to the line angles, resulting in the mesial and distal walls diverging externally. The convexity of the tooth in the gingival one third results in the occlusal and gingival walls diverging externally. There are several retention groove designs that are appropriate, including four corner coves, occlusal and gingival line angle grooves, or cir¬cumferential grooves. However, as with any restoration, if there is only a small amount of tooth structure (< 1 mm) between the new and existing restoration, it is best to join the two restorations together and prevent the possibility of fracture of the small amount of remaining tooth structure.
Question 6

When carving a Clam I amalgam restorationwhich statement is false?

A
Carving may be made easier by waiting 1 or 2 minutes after condensation before it is started.
B
The blade of the discoid carver should move parallel to the margins resting totally on the partially set amalgam.
C
Do not carve deep occlusal anatomy.
D
The carved amalgam outline should coincide with the cavosurface margins.
Question 6 Explanation: 
B. Amalgam carving should result in coincidence with the cavosurface margin and should not result in deep occlusal anatomy because such form may create acute amalgam angles that are subject to fracture. Depending on the condensation rate of the amalgam used, waiting a couple of minutes prior to initiating carving may allow the amalgam to harden enough that the carving will be easier and overcarving will be minimized. When carving the occlusal cavosurface margin, the discoid carver should rest on the adjacent unprepared enamel, which will serve as a guide for proper removal of amalgam back to the margin.
Question 7
In the conventional Class I composite preparation, retention is achieved by which of the following features?
  1. Occlusal convergence
  2. Occlusal bevel
  3. Bonding
  4. Retention grooves
A
2 and 4
B
1 and 3
C
1 and 4
D
2 and 3
Question 7 Explanation: 
B. Typically, the Class I composite preparation has occlusally converging walls that provide primary retention form. The actual bonding also provides retention form. However, an occlusal bevel is not indicated on Class I preparations nor are reten¬tion grooves used.
Question 8

Which one of the following acids is generally recommended for etching tooth structure?

         
A
Maleic acid
B
Polyacrylic acid
C
Phosphoric acid
D
Tartaric acid
E
Ethylenediaminetetraacetic acid (EDTA)
Question 8 Explanation: 
C. Although some of the self-etch bonding systems use milder acid, the primary acid system used for etching tooth structure is phosphoric acid.
Question 9

Which of the following statements about indirect pulp caps is false?

A
Some leathery caries may be left in the preparation.
B
A liner is generally recommended in the excavation.
C
The operator should wait at least 6 to 8 weeks before re-entry (if then).
D
The prognosis of indirect pulp cap treatment is poorer than that of direct pulp caps.
Question 9 Explanation: 
D. When doing an indirect pulp cap some caries may be left, a liner [probably Ca(OH)2] is usually placed over the excavated area, and the area may be assessed 6 to 8 weeks later. Regardless, the indirect pulp cap prognosis is better than the prognosis for direct pulp caps.
Question 10
A casting may fail to seat on the prepared tooth due to all of the following factors except _____.          
A
Temporary cement still on the prepared tooth after the temporary restoration has been removed.
B
Proximal contact(s) of casting too heavy/tight.
C
Undercuts present in prepared tooth.
D
The occlusal of the prepared tooth was under­reduced.
Question 10 Explanation: 
D. Occlusal reduction would not affect the ability to seat a casting. However, temporary cement, heavy proximal contacts, or tooth undercuts could keep the casting from seating completely.
Question 11
Which of the following materials has the highest linear coefficient of expansion?
A
Amalgam
B
Direct gold
C
Tooth structure
D
Composite resin
Question 11 Explanation: 
D. Composite materials exhibit more dimensional change (2.5 times greater than tooth structure) when subjected to extreme changes in tempera¬ture than do the other choices. Direct gold is slightly higher than tooth structure, and amalgam is about twice as high as tooth structure.
Question 12
A cervical lesion should be restored if it is _____.
A
Carious.
B
Very sensitive.
C
Causing gingival inflammation.
D
All of the above.
Question 12 Explanation: 
D. All of these factors indicate that a cervical lesion should be restored. In addition, if the lesion is large and the pulpal or gingival tissues are in jeopardy, it should be considered for restoration.
Question 13
Triturating a dental amalgam will_________
A
Reduce the size of the alloy particles.
B
Coat the alloy particles with mercury.
C
Reduce the crystal sizes as they form.
D
Dissolve the alloy particles in mercury.
Question 13 Explanation: 
B. Triturating (mixing) the amalgam particle with the mercury is intended to result in coating the particles with a surface of mercury and creating the desirable phases in the set amalgam. All of the alloy particle is not dissolved in the mercury, nor is the size significantly reduced.
Question 14

The use of the rubber dam is best indicated for .

A
Adhesive procedures.
B
Quadrant dentistry.
C
Teeth with challenging preparations.
D
Difficult patients.
E
All of the above.
Question 14 Explanation: 
E. The advantages and benefits of rubber dam usage are reflected in all of the items stated. The rubber dam isolation increases access and visi¬bility.
Question 15
Smooth surface caries refers to .
A
Facial and lingual surfaces.
B
Occlusal pits and grooves.
C
Mesial and distal surfaces.
D
A and C.
Question 15 Explanation: 
D. Smooth surface caries occurs on any of the axial (facial, lingual, mesial, and distal) tooth surfaces but not the occlusal.
Question 16
Which of the following statements about an amalgam tooth/cavity preparation is true?
A
The enamel cavosurface margin angle must be 90 degrees.
B
The cavosurface margin should provide for a 90- degree amalgam margin.
C
All prepared walls should converge externally.
D
Retention form for Class Vs can be placed at the DEJ.
Question 16 Explanation: 
B. Although the amalgam margin must be 90 degrees, the enamel margin may not be 90 degrees, especially on the occlusal surface. Most walls converge occlusally, but many Class V amalgam preparations have walls that diverge externally. No retention form should be placed at the DEJ; otherwise, the adjacent enamel will be undermined and subject to fracture.
Question 17
Which of the following statements is true regarding the choice between doing a composite or amalgam restoration?
A
Establishing restored proximal contacts is easier with composite.
B
The amalgam is more difficult and technique- sensitive.
C
The composite generally uses a more conservative tooth/cavity preparation.
D
Amalgam should be used for Class II restorations.
Question 17 Explanation: 
C. The restoration of a proximal contact is easier with amalgam than composite. Amalgam is eas¬ier to use and is less technique-sensitive. Either material can be used for Class II restorations. Because an amalgam restoration requires a tooth preparation that has (1) a specified depth (for strength of the amalgam), (2) cavosurface marginal configurations that result in 90-degree amalgam margins, and (3) undercut form to its walls or secondary retention form features, they require more tooth structure removal than do composite tooth preparations. Composite tooth preparations require (1) removal of the fault, defect, or old material; (2) removal of friable tooth structure; and (3) no specific depths—they are more conservative.
Question 18
Causes of postoperative sensitivity with amalgam restorations include all of the following except ___.        

A
Lack of adequate condensation, especially lateral condensation in the proximal boxes.
B
Voids.
C
Extension onto the root surface.
D
Lack of dentinal sealing.
Question 18 Explanation: 
C. The primary causes of postoperative sensitivity for amalgam restorations are voids (especially at the margins), poor condensation (that may result in a void), or inadequate dentinal sealing. Extension onto the root surface does not neces¬sarily result in increased sensitivity.
Question 19
The setting reaction of dental amalgam proceeds primarily by _____.
A
Dissolution of the entire alloy particle into mercury.
B
Dissolution of the Cu from the particles into mercury.
C
Precipitation of Sn-Hg crystals.
D
Mercury reaction with Ag on or in the alloy particle.
Question 19 Explanation: 
D. The trituration process mixes the amalgam com¬ ponents and the reaction results in the alloy particle being coated by mercury and a product being formed.
Question 20
All of the following reasons are likely to indicate the need for restoration of a cervical notch except ____.
A
Patient age.
B
Esthetic concern.
C
Tooth is symptomatic.
D
Deeply notched axially.
Question 20 Explanation: 
A. If a patient has a notched cervical area that is very sensitive or very esthetically objectionable, restoration is usually indicated. If the notched area is very deep, adverse pulpal or gingival responses may occur. Although more notched areas are encountered in older patients, a patient’s age is not a factor in the need for restoration.
Question 21

Many factors affect tooth/cavity preparation. Which of the following would be the least important factor?

A
Extent of the defect.
B
Size of the tooth.
C
Fracture lines.
D
Extent of the old material.
Question 21 Explanation: 
B. Obviously, a tooth preparation is dictated by the extent of the carious lesion or old restorative material, the creation of appropriate convenience form for access and vision, and the anticipated extensions necessary to provide an appropriate proximal contact relationship. Fracture lines present should normally be included in the restoration. However, it is rare that the size of the tooth will affect the design of the tooth preparation.
Question 22
A major difference between total-etch and self­-etching primer dentin bonding systems include all of the following except ____.
A
The time necessary to apply the material(s).
B
The amount of smear layer removed.
C
The bond strengths to enamel.
D
The need for wet bonding.
Question 22 Explanation: 
A. Self-etch dentin bonding systems differ from total-etch dentin bonding systems by removing less of the smear layer (they use a less potent acid), creating a weaker bond to enamel (espe¬cially nonprepared enamel), and not requiring wet bonding that may be necessary for some of the total-etch systems. Even though fewer actual materials may be needed with some of the self-etch systems, they need to be applied in multiple coats and thus the time necessary to apply the materials is similar for both systems.
Question 23

For a dental hand instrument with a formula of 10-8.5-8-14, the number 10 refers to .

A
The width of the blade in tenths of a millimeter.
B
The primary cutting edge angle in centigrades.
C
The blade length in millimeters.
D
The blade angle in centigrades.
Question 23 Explanation: 
A. The first number is the width of the blade or pri¬mary cutting edge in tenths of a millimeter (0.1 mm). The second number of a four-number code indicates the primary cutting edge angle, measured from a line parallel to the long axis of the instrument handle in clockwise centigrades.The angle is expressed as a percent of 360 degrees. The instrument is positioned so that this number always exceeds 50. If the edge is locally perpendicular to the blade, then this number is normally omitted, resulting in a three-number code. The third number (second number of a three-number code) Indicates the blade length in millimeters. The fourth number (third number of a three-number code) indicates the blade angle, relative to the long axis of the handle in clock¬wise centigrades.
Question 24
The one constant contraindication for a composite restoration is _____.        
A
Occlusal factors.
B
Inability to isolate the operating area.
C
Extension onto the root surface.
D
Class I restoration with a high C-factor.
Question 24 Explanation: 
B. The constant contraindication for using a com¬ posite restoration is the inability to properly iso¬late the operating area. Occlusal wear of composite is similar to that of amalgam. Extension onto the root surface may result in gap formation with composite but also results in initial leakage with amalgam, indicating that there is no ideal material for root-surface extended restorations. A high C-factor (Class I) can be largely overcome by using (1) a liner under the composite, (2) a filled adhesive, and (3) incremental insertion of the composite.
Question 25

When placement of proximal retention locks in Class II amalgam preparations is necessary, which of the following is incorrect?

A
One should not undermine the proximal enamel.
B
One should not prepare locks entirely in axial wall.
C
Even if deeper than ideal, one should use the axial wall as a guide for proximal lock placement.
D
One should place locks 0.2 mm inside the DEJ to ensure that the proximal enamel is not undermined.
Question 25 Explanation: 
C. Retention locks, when needed in Class II amal¬gam preparations, should be placed entirely in dentin, thereby not undermining the adjacent enamel. They are placed 0.2 mm internal to the DEJ, are deeper gingivally (0.4 mm) than occlusally (i.e., they fade out as they extend occlusally, and translate parallel to the DEJ). If the axial wall is deeper than normal, the reten¬tion lock is not placed at the axiofacial or axiolin- gual line angles but, rather, is positioned 0.2 mm internal to the DEJ. If placed at the deeper loca¬tion, it may result in pulp exposure, depending on the location of the axial wall depth.
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