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Question about when a tooth is drilled



Apr 17, 2006
Why does the dentist use a fast drill first and then switches to a slower one? The slower one really vibrates the head more. Just curious as to what they are doing.
The high speed handpiece is used to remove fillings, shape the enamel and dentin, and basically deal with hard structures. Once the access has been made and the gross caries removed, the slower speed handpiece allows the dentist to carefully clean away any remaining decay more carefully and precisely.

The high speed goes quite fast and as such removes anything in its path rather quickly. The slower speed vibrates more due to it's slower speed, but it gives the dentist better tactile sense while removing cavities especially when they are deeper and closer to the nerve or other areas. Think of the high speed as a big roller brush to paint with while the slow speed is more like a fine tipped brush to refine the details.
I have one more question how does a composite and metal filling adhere to the tooth?
Composite fillings are bonded into the tooth with adhesives, amalgam fillings are occasionally bonded in but usually are held in place by mechanical means, the dentist cuts a groove or dovetail into the tooth to give the mechanical retention. The amalgam also swells a little as it sets and locks itself into place a bit more tightly.
That's exactly the same thing. It's actually surprising how many common elements in carpentry and construction there are with dentistry. Dentists use post and pins to retain fillings, adhesives to "glue" fillings in, etc... :)