Subcrestal vs. Equicrestal Implant Placement in Augmented Posterior Mandibular Sites: A Biomechanical and Histomorphometric Comparative Evaluation of Crestal Bone Stability and Osseointegration Kinetics

Abstract

Crestal bone preservation around dental implants placed in augmented posterior mandibular sites remains a clinically contested objective, with implant positioning depth representing a critical yet insufficiently standardized variable. This prospective comparative study evaluated subcrestal (1.5 mm) versus equicrestal implant placement protocols in 84 patients (168 implants) across a 24-month follow-up period. Primary outcomes included marginal bone level changes assessed by standardized periapical radiography and cone-beam computed tomography, while secondary outcomes encompassed implant stability quotient evolution, histomorphometric bone-to-implant contact ratios, and peri-implant soft tissue health indices. Subcrestal placement demonstrated statistically significant superiority in crestal bone maintenance (mean bone loss: 0.41 ± 0.12 mm vs. 0.89 ± 0.21 mm; p < 0.001) without compromising osseointegration kinetics or increasing peri-implant mucositis incidence. These findings advocate for protocol-specific implant depth selection contingent upon bone graft maturation staging and prosthetic emergence profile requirements.