Comparative Analysis of Buccal and Lingual Bone Thicknesses Following Immediate and Delayed Loading of Posterior Mandibular Implants

Peri-implant bone preservation is a critical determinant of long-term implant survival. Although both immediate and delayed loading protocols have demonstrated favorable clinical outcomes, their influence on longitudinal buccal and lingual bone remodeling remains an area of investigation. This study compared peri-implant bone thickness changes following immediate and delayed loading in posterior mandibular implants using cone-beam computed tomography (CBCT).

A prospective study was conducted on 80 patients who received single posterior mandibular implants. The patients were divided into two groups: immediate loading (n = 40) and delayed loading (n = 40). Buccal bone thickness (BBT) and lingual bone thickness (LBT) were measured at the crestal, middle, and apical levels on standardized CBCT scans obtained immediately after implant placement and before prosthetic loading (T1), at six months (T2), and at 12 months (T3) after implant placement. Two-way mixed repeated-measures analysis of variance (RM-ANOVA), independent-samples t-test, and multiple linear regression analyses were performed, with statistical significance set at p < 0.05.

The baseline demographic characteristics were comparable between the groups. The immediate loading group demonstrated significantly greater insertion torque (43.60 ± 4.83 vs. 33.29 ± 6.05 Ncm, p < 0.001) and implant stability quotient (72.17 ± 4.46 vs. 69.38 ± 4.21, p = 0.005). BBT decreased significantly in both groups during follow-up, with greater crestal bone loss in the immediate loading group (0.57 ± 0.17 mm) than in the delayed loading group (0.27 ± 0.09 mm). LBT also decreased over time but exhibited a smaller magnitude of remodeling than the buccal cortical plate. Two-way mixed RM-ANOVA demonstrated significant group × time interactions for both BBT and LBT (p < 0.001). Multiple linear regression identified immediate loading as the strongest independent predictor of 12-month crestal buccal bone loss (β = 0.660, p < 0.001), whereas increasing age showed a modest protective association (β = -0.212, p = 0.008).

Both loading protocols demonstrated successful peri-implant bone adaptation during the first postoperative year. However, immediate loading was associated with greater peri-implant bone remodeling, particularly in the crestal region, whereas delayed loading resulted in better preservation of BBT and LBT. Careful patient selection and adequate primary implant stability are essential when immediate loading protocols are employed.