Bone Loss Patterns Following Over-Preparation of Implant Osteotomies: A Prospective Split-Mouth Study

Objective: To evaluate the effect of over-preparation of implant osteotomies on marginal bone loss and radiographic bone-loss patterns around implants placed bilaterally in the posterior mandible. Methodology: A prospective bilateral clinical study was conducted in 30 partially edentulous adults (16 men, 14 women). Each patient received at least two implants per side in the posterior mandible. A total of 62 bone-level implants (4.0 × 10.0 millimetres; Neobiotech, Seoul, Korea) were placed: 31 with the manufacturer’s standard osteotomy (final drill 3.5 millimetres) and 31 with an over-prepared osteotomy (final drill 4.0 millimetres). Cases and osteotomy type were allocated pragmatically, not randomly. Insertion torque and implant stability quotient (Osstell Beacon) were recorded at placement. The same operator performed all radiographs and prosthetic treatment. Standardised periapical radiographs were taken at prosthesis delivery, six months and twelve months. Marginal bone loss was measured from implant shoulder to first bone implant contact. Bone-loss patterns were classified as horizontal, vertical crater-like, circumferential, or combined vertical-buccal defects. Paired and mixed-effects analyses were applied to this dataset. Results: Example values showed lower primary stability in over-prepared sites (insertion torque approximately 21 ± 6 newton centimetres; implant stability quotient 61 ± 5) than in standard sites (38 ± 7 newton centimetres; 72 ± 4). Mean marginal bone loss at six and twelve months was greater at over-prepared osteotomy sites (about 1.28 and 1.70 millimetres) than at standard sites (about 0.72 and 0.95 millimetres). Over-prepared sites presented more vertical and circumferential bone-loss patterns, while standard sites predominantly showed horizontal remodelling. Conclusions: Within the limitations of this non-randomised bilateral study model, over-preparation of osteotomies appears associated with reduced primary stability and increased, more vertical marginal bone loss at six and twelve months. Over-preparation should be avoided when possible, and alternative strategies considered when primary stability is at risk.