negar

1.     The crown-rot ratio

A.   Can easily be decreased in periodontal involved posterior teeth.

B.   Should never be decreased in periodontally involved anterior teeth.

C.   None of the above

C. the crown root can be decreased in periodontally involved anterior teeth to reduce the mobility factor and diminish the load on the anterior teeth . reducing the crown root in periodontally involved posterior  teeth can be result

2.      of the  following the greatest disadvantage of  precision intracoronal attachment when they are used in partial denture construction is that they:                                                                                                                       

A.   Present esthetic problems.

B.   Are unstable

C.   Are costly

D.   Require extensive preparation of the abutment teeth                                                                                                                         

D. to allow the insertion of a female attachment more tooth structure should be removed from the abutment teeth, to accommodate the attachment. It is desirable that the attachment be entirely intracoronal in order to preserve normal  contours.

3.     Resistant to proximal displacement of a two surface inlay depends on which of the following:

A. Mechanical  retention of cement with the casting.

B.  Occlusal dovetail

C.  Cement  adhesion

D. Proximal contact

      B. the occlusal dovetail acts as a lock preventing  the proximal displacement of an inlays.

      

4. Pulpal sedation and protection is most  frequently attained by using:

          A. Calcium hydroxide

          B. Cyanoacrylate

          C. Zinc oxide eugenol

          D. Zinc phosphate cement

         

C. zinc oxide eugenol is an anodyne dressing with both antiseptic and anesthetic properties; therefore it has the capability of sedating the pulpal tissues.

5.     Cavity varnish is a useful material in restoring teeth with amalgam because it:

a.     Reduces marginal leakage

b.     Eliminates sensitivity

c.      Eliminates galvanic shock

d.     Reduces plaque formation

  A. the initial set of alloy restoration is marked by expansion; the cavity varnish seals marginal openings and reduce marginal leakages.

6.     The convergence of the proximal axial walls of a crown preparation

a.     Is determined by the pulp

b.     Should be no more than 2 to 5 degrees from vertical

c.      Should be 8 to 12 degrees from vertical.

d.     Is determined by the position of the soft tissue.

  C. Eight to twelve degrees from the vertical provides the maximum retention for the crown preparation. Anything in excess diminishes the retentiveness of a crown proportionately.

7.     A wide labial or buccal shoulder for full crown preparations

a.     Is desirable in lateral incisors

b.     Should only be used on molars

c.      Is obtainable only with burs

d.     May jeopardize the pulp

 D. an excessively wide labial or buccal shoulder for full crown veneer preparation will generally jeopardize the pulp because of the axial penetration through the enamel and the dentin. If this penetration is excessive, it will encroach on the pulpal tissue.

8.     In specific instances, there are advantages in using nonvital teeth, for full coverage preparations. Which of the following is such an advantage

a.     Usually limits the design of the preparation.

b.     Offers a better crown-roof ratio

c.      Enhances mechanical and esthetic factors.

d.     Weakens remaining tooth structure.

 C. using a nonvital tooth as an abutment can improve esthetic factors because one is able to prepare a larger shoulder and therefore provide enough roof for the esthetic materials. In addition, mechanical factors such as tooth reduction for parallelism, occlusal reduction for the extruded teeth, and access problems can be improved because there is no concern for encroaching on the pulpal tissues.

9.     In restoring periodontally involved teeth it is desirable to use:

a.     Full coverage wherever possible.

b.     A splint on all remaining teeth.

c.      Partial coverage wherever necessary and possible.

d.     Porcelain fused in gold.

 C. whenever it is possible, partial coverage is the treatment of choice for periodontally involved teeth because using this type of treatment approach can prevent additional tissue problems. If the restoring materials can be kept away from the tissue it will allow the patient easier maintenance.

10.                        Electrosurgery can be used safely in connection with:

a.     Nitrous oxide and oxygen analgesia

b.     Ether anesthesia

c.      Pacemaker

d.     Ethyl chloride.

 A. a spark can occur when using electro surgery; therefore flammable or explosive mixtures of anesthetics should be avoided. In addition the electrosurgical devices can interfere with the pacemaker impulse.

11.                        Use of electro surgery for recon touring gingival tissues results in:

a.     A god firm scar tissue.

b.     A clear field with minimal bleeding

c.      Delayed healing

 B. the nature of the incision is controlled heat production which seals the capillaries and result in minimal bleeding.

12.                        Most cutting procedures with electro surgery in the oral cavity are best accomplished with:

a.     Fully fettered, fully rectified current

b.     Coagulation current

c.      Fully rectified current

d.     Partially rectified current

 C. fully rectified currents produce good cutting and adequate hemostasis.

13.                        In the use of electro surgery in the oral cavity, profound anesthesia is:

a.     Usually needed

b.     Never needed

c.      Almost always needed

d.     Not needed for endodontically involved teeth.

 C. profound anesthesia is needed because of the vital tissue which contains nerve endings. In addition, the electrode tip will stimulate the pulp much like a pulp-testing device.

14.                        Electro surgery is:

a.     The same as electrocautery

b.     Accomplished with a cold electrode and an electronic arc

c.      Performed by a heated electrode

d.     Accomplished with a hot electrode and an electronic arc

 B. heat is produced by the impedence of the tissue and not in electrode farcing occurs in the tissue at point of electrode contact.

15.                        A factor determining the setting for the cutting current is:

a.     Rom temperature

b.     Amount of anesthesia

c.      Size of the machine being used

d.     Tissue thickness

 D. the setting for the cutting current is directly proportional to the thickness of the tissue. The thicker the tissue, the greater is the resistance to the passage of current. The nature, type, dentistry and the amount of hydration all affect the resistance of tissue.

16.                        Electrosurgical preparation of the sulcus for impression taking:

a.     Requires healthy gingival tissue

b.     Requires the use of coagulation current

c.      Eliminates the need for retraction cord

d.     Requires the need of retraction cord.

  A. healthy gingival tissue is a prerequisite for any impression taking procedure, whether preceded by electrosurgical techniques or the use of gingival retraction impregnated cord. The level of healing is unpredictable in unhealthy tissues.

17.                        A too low setting of the control dial for cutting results in:

a.     Fulguration

b.     Desiccation

c.      More damage to tissue

d.     Less damage to tissue

  C. Too low a setting for cutting purposes with electrosurgical equipment results in reduces the impedence and the progress of electrode through this tissue will be too slow. Greater heat will be produced on either side of the incision, which may result in necrosis.

18.                        Tissue adhering to the electrode

a.     Impedes the progress of the electrode through the tissue

b.     Is of little importance

c.      Requires the use of lower current settings.

d.     Usually volatilizes before it becomes a problem.

 A. tissue adhering to the electrode will impede the progress of the electrode through the tissue because the retained tissue tags will reduce impedence. This will result in heat build-up lateral to the incision which may cause necrosis.

19.                        The indifferent plate is used:

a.     Primarily for fulguration

b.     Because it permits the use of higher currents

c.      Primarily for electrodessication

d.     Because it allows the use of lower currents

  D. although high frequency radio waves do not require a circuit, the use of an indifferent plate allows more efficient return of energy to the source, thereby allowing the use of lower current settings which are less damaging.

20.                        The foot control should be:

a.     Activated before cutting the tissue

b.     Activated upon touching the tissue for cutting

c.      Activated intermittently while cutting the tissue

d.     Activated only for fulguration.

        A. the foot control should be activated prior to cutting the tissue because of the initial surge of energy that is generated at the tip which will cause tissue damage and coagulation.