Dovetail lock, retention and resistance forms?!
Question:
Dovetail lock, retention and resistance forms?
I am a dental student.My question is how to make a dovetail lock in class 2 compound preparation on both deciduous and permanent teeth. I have not the slightest idea clinically. And how do I make the proximal box without overremoving the healthy enamel tissues? (sometimes I almost cut into the gingival tissues (on my frasaco teeth) ...Please helppp...
Answers:
Use the length of the bur's cutting area as reference when cutting the proximal box. A typical #56 straight bur has a cutting area around 3.5mm long depending on the brand, so when you cut the proximal box in a permanent tooth, sink a #56 bur to a depth about 3/4 that of the length of its cutting area. That should bring you to near the optimal depth for a proximal box. It should be somewhat less deep for a deciduous tooth.
If you can no longer see the bur's cutting area after sinking it into the tooth, you know you have gone too deep.
Dovetails are easy. Just make that part of the prep a bit wider than the middle part of the prep to allow an amalgam to "lock in" and not get dislodged in a mesial or distal direction. That's the resistance form-- Resistance to dislodgement.
All this stuff is in your operative dentistry textbook (I think the majority of dental schools use the one by Sturdevant).. You really should crack it open. :-D
Hope this helps, keep practicing, and good luck.