Horizontal ridge augmentation in the anterior maxilla with in situ onlay bone grafting: a retrospective cohort study

Objectives This study aimed to introduce a digitally guided in situ autogenous onlay grafting technique and compare its effectiveness with the conventional (ex situ) onlay technique in augmenting horizontal bone defects of the anterior maxilla. Materials and methods This retrospective cohort study included 24 patients who had received autogenous onlay bone grafts combined with guided bone regeneration (GBR) in the anterior maxilla. Fourteen patients were recruited into the in situ onlay grafting group (EG), and 10 were recruited into the ex situ onlay group (CG), defined by the donor sites. The clinical parameters, radiographic changes, micro-CT, and histological processes were evaluated after a mean follow-up period of 1.7 years. Results The horizontal bone width reflected significant bone modeling over time (p < 0.001) in the first 6 months. Multivariable analysis showed that the treatment modality (grouping) was a critical factor positively associated with vertical bone height alteration. However, neither the alteration rate of horizontal bone width nor the bone volume was associated with the treatment modality. The number of periosteal screws per graft positively affected horizontal contour maintenance (p < 0.05). No significant differences were observed between the groups in the clinical parameters (complications, success rate, and peri-implant parameters). The micro-CT and histological outcomes were similar between the groups. Conclusion Despite the limitations of this study, in situ onlay grafting combined with GBR was an effective and reliable approach for horizontal bone augmentation in the anterior maxilla and appeared to demonstrate better stability in vertical bone remodeling.