Could a dentist delay bone shrinkage on 3rd molar area that had a tooth break in pieces?

Is this a concern?: Usually the third molar area is not favored for implants. For third molars, many are removed in pieces and the bone remodels without issue.

Bone graft: A bone graft in a third molar area would delay resorption however is not recommended for that area. The lower jaw ascends upward behind third molars and is a growth center which keeps the bone at a higher level anyway.

Depends: Usually bone grafting only done on 3rd molars in specific situations. Best advice is to see a board certified oral surgeon for exam/recommendations.