Lower Right #45 & #47 in D1 Bone

This case shows two implants placed side by side in the lower right posterior mandible — replacing the second premolar (#45) and the second molar (#47). Both sites present dense D1 bone, the most cortical and least trabecular of the Misch bone-quality classifications, and traditionally the most demanding to drill.

D1 bone is challenging for a conventional ascending drilling sequence for two reasons. First, the crestal cortex is thick and rigid, so each successive drill engages a hard interface with limited elastic give. Second, dense bone accumulates frictional heat quickly, and stainless-steel cutting edges lose their sharpness in dense bone faster than in softer tissue — which drives more heat on every subsequent pass.

The Crown Down protocol separates the osteotomy into two mechanically distinct tasks. The cortical drill matched to implant diameter clears the crestal cortex first. A smaller trabecular drill then prepares the deeper cancellous portion. Because tungsten carbide holds a sharp cutting edge under dense-bone load and conducts heat away from the cutting interface rather than accumulating it in the bone, the same 2-drill sequence works predictably in D1 without the long ascending sequence a steel kit would require.