Evaluation of labial bone thickness of implants placed with or without simultaneous guided bone regeneration using CBCT scanning after at least one year in function

Objectives: To evaluate the labial bone thickness with or without simultaneous guided bone regeneration around single tooth implants after at least one year in function using cone beam computed tomography (CBCT). Furthermore, the influence of timing of implant placement on the labial bone thickness was evaluated. Methods: 46 single tooth implant restorations in the maxillary aesthetic zone (inter-canine) with at least 12 months post-loading follow-up period were evaluated using CBCT scans. Rough hydrophilic (Straumann SLActive) implants placed without guided bone regeneration (non-GBR) were compared to the ones placed with simultaneous guided bone regeneration (sGBR) using deprotinized bovine bone and porcine collagen membrane. Two experienced radiologists measured the labial bone thickness (LBT) on CBCT scans at three different points along the implant length (i) L0 - identified as the shoulder in a bone level (BL) and the SLA junction in a tissue level (TL) implant; (ii) L25 - 25% and; (iii) L50 - 50% of the implant length. The groups were further subdivided based on Type 1, Type 2 and Type 4 placement protocol for comparison of LBT. Results: Mean age of patients was 33y. Mean time from surgery to CBCT was 3.7y (max. 5.6y). The inter-examiner reliability was confirmed (r>0.8). Mean LBT (SD) in Type 1 placement protocol at L0, L25 and L50 for nonGBR were 0, 0.8(0.4), and 1.3(0.8)mm respectively in comparison to 1.1(0.8), 1.8(1), and 2.1(0.9)mm for the sGBR group. The differences for L0 and L25 were statistically significant (p0.05). In Type 2 placement the mean LBT at L0, L25 and L50 were 1.2(0.7), 0.9(0.5), and 0.5(0.4)mm respectively in the non-GBR group and 1.6(1.3), 2.5(0.9), and 2.1(1.3)mm for the sGBR group. The differences for L25 and L50 were statistically significant. In type 4 placement the mean LBT at L0, L25 and L50 were 0.6(0.7), 1.3(0.5) and 1.2(0.7)mm respectively in the non-GBR group and 1.1(1), 2(1.1) and 2.2(0.8) mm for the sGBR group. The differences at L0 and L50 were statistically significant. Type 2 had greater LBT than Type 1 particularly in cases with dehiscence or fenestrations. Conclusions: Within the limitations of this study, sGBR with deprotinized bovine bone and porcine collagen membrane on rough hydrophilic implants seem to be predictable in maintaining LBT up to a mean follow up of 3.7y. In Type 1 implants sGBR appears to preserve some but not increase the LBT. On the contrary, sGBR in Type 2 placement (even with dehiscence or fenestrations) significantly increases the amount of labial peri-implant bone thickness in implants that have been in function for at least one year. Keywords: labial bone thickness, dental implants, immediate implants, early delayed implants