operative dentistry doubts

[anajali]

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1.In restoring a class2 cavity,an onlay is indicated when the
a.need for extra retention exists
b.patient has high caries index
c.opposing tooth has full coverage
d.dentinal support of the cusps is questionable
e.all of the above

the answer given is d...
why isnt option 1 correct?

2.Use of a rubber dam is most indicated for which of the following procedures?
a.removal of carious dentinfrom deep lesions
b.pulp capping
c.placement of direct fillign gold
d.removal of old amalgam restoration
e.openign into pul[p chamber to drain an abscess

the answer given is a,b,c
well isnt d also the right option? along with a,b,c?

 

[drangel]

hi anajali,,,

i suppose the ans 1 is not right bcoz if extra retention is needed in class2 then u can give retention locks,coves,pins etc,,,, just for extra retention u can't give an onlay,,,,

 

[anajali]

hi drangel,
yeah i guess u r right...thank u for the reply....
hey do u know the answer for this in pharmacology...

1.the inhalation of amylnitrite may result in...
a.coronary artey dilatation
b.peripheral arteriolar dilatation
c.bradycardia
d.increased motility of small bowel
e.decrease in arteriolar blood pressure....

 

[toothmail]

hi anjali

amyl nitrite is an antianginal drug. but it doesnt act through coronary dilatation. its main action is through peripheral vasodilatation and hence reduces systemic and pulmonary BP and reduces afterload and CO. its not really used much now since nitrates are much safer than nitrites. btw its also a diagnostic for cardiac conditions and also acts as an antidote in cyanide poisoning.

 

[jupp]

1.In restoring a class2 cavity,an onlay is indicated when the
a.need for extra retention exists
b.patient has high caries index
c.opposing tooth has full coverage
d.dentinal support of the cusps is questionable
e.all of the above

This explanation is from one of the decks:
The main advantage of the onlay is that it can permanently restore and reinforce a tooth by a conservative technique. Although conservation of tooth structure is desirable, such action is offset by a lack of retention. It has been shown that the conservative onlays have infferior retention compared to full crowns. This is due to the crown's greater axial surface area.

 

[anajali]

hi toothmail ,jupp and drangel,
hey i am convinced with ur answers...
regarding amylnitrite i didnt know it was used in cyanide poisoning...i thought nitrates were the only ones used...as u said may be nitrites are no longer in use......
i am really happy that i can put across all my doubts here on this site ....
forgive me if u guys think my questions are too primitive.....
thank u
anjali.