Bone Density

Bone density describes the hardness and structural quality of the jawbone. It is one of the most important factors affecting how quickly and reliably an implant integrates, and whether immediate loading (same-day teeth) is possible.

Classification

Bone is classified into four types (Lekholm and Zarb classification):

• D1: Dense cortical bone — very hard, found in the lower front jaw. Excellent stability but generates more heat during drilling.
• D2: Thick cortical bone with coarse cancellous core — ideal for implants. Common in the lower jaw.
• D3: Thin cortical shell with fine cancellous core — adequate but requires careful technique. Common in the upper jaw.
• D4: Very thin cortical bone, almost entirely fine cancellous — challenging. Found in the upper back jaw (posterior maxilla). Higher failure risk.

Assessment

Bone density is assessed clinically during surgery and can be estimated from a CBCT scan beforehand. In low-density bone, modifications to the surgical technique (such as undersizing the preparation) can improve primary stability.