Question: In "X-Men Origins Wolverine", Logan undergoes an operation to have Adamantium bonded to his skeleton. 

Why doesn't the Adamantium bond to his teeth?

Answer: 
In humans, teeth make up part of the skeletel system but they are not classified as bones. Teeth are made up of Dentin and Enamel whereas bones are made up of Osseous tissue. 

So I imagine the adamantium only bonded to the Osseous and not the Dentin or Enamel which results in adamantium bones and shiny white teeth.
**the goal of the experiment was to bond the admantium to the bones inside the body forming the skeletal framework only**

When wolverine was 'bonded' with admantium, the experiments carried out were to inject and turn the bones into admanitum so that a skeleton of this 'super-metal' will make the body highly resistant to damage. The admantium was only injected into his bodily bones, and not over his teeth and other appendages. It is the same as asking why admantium was not put over his 'nails'. The experiment was limited only to the bones making part of body skeleton. As such, wolverines claws are automatically coated with the super-metal. 
Unlike other experiments, where external claws and skin were tried to be bonded with admantium, Logan's experiment was limited to his bones.