Purpose: This animal study investigated vertical bone formation (VBF) around implants and used histomorphometric analysis to compare different bone-filling materials associated with a massive titanium dome as a tissue barrier. Materials and Methods: Seven dogs were submitted to surgical procedures with extraoral access to the lower edge of the mandible, and four implants were semi-inserted in each animal. Each implant received one treatment: autogenous bone with clot (AB), control clot (C), synthetic graft (Biogran [BG]), or xenograft (Bio-Oss [BO]). Massive titanium domes were stabilized over the implants. Histologic analysis was performed after 3 months, and quantitative aspects were evaluated in extraosseous and intraosseous threads on Image Pro-Plus software. Results: VBF around implants exhibited significant values in AB compared with other groups. BG and BO presented statistical equivalency to AB and C in the apposition and filling of extraosseous threads. There was no difference between groups for parameters evaluated in intraosseous threads. Conclusion: The experimental model was valid for evaluation of VBF around implants placed in atrophic mandibles. Considering the limitations of this study, histomorphometric analysis evidenced better outcomes for group AB. Even though groups BG and BO presented worse outcomes than AB, they were slightly better compared with the control group. Keywords: animal experiments, biomaterials, bone-implant interactions, bone regeneration, guided tissue regeneration