The aim of this study was to evaluate the amount of bone formation beneath a defect area after treatment with titanium mesh membranes with different thicknesses and pore sizes alone or in combination with bone graft to induce bone formation during the early stage of healing time. The mandibular premolars were extracted bilaterally from three adult beagle dogs, and 8-mm-diameter bone defects were created on the buccal site of the premolar regions. Hydroxyapatite bone graft substitute was applied in the defect site unilaterally, and other site was left empty. Then, a novel micro-porous mesh (50 μm in pore diameter) or commercially available macro-porous titanium mesh (1700 μm in pore diameter) was placed on the defect and secured with screws. After 4 weeks, the mandibles were harvested, imaged using micro-computed tomography, and prepared for histological and morphometric evaluation. Higher new bone volumes (mm3), percentage of new bone volumes in the total defect volumes (bone ratio: %), and new bone area (mm2) through morphometric evaluation were found on the novel membranes with 50-μm-diameter pores compared to the commercial titanium mesh. Moreover, experiment sites without bone graft were observed with higher new bone volume and bone ratio compared with sites with bone graft. However, bone mineral density of novel mesh was observed to be lower compared with other experimental sites. Under the experimental condition, the result of this study suggests that titanium meshes with 50-μm-diameter pores were effective for guided bone regeneration in the early stage of healing.