OBJECTIVE Augmentation of the alveolar ridge before implant placement is frequently performed. The purpose of this study was to compare the amount and quality of bone formation under Micro Titanium Augmentation Mesh (M-TAM) when used alone for guided tissue regeneration or in combination with a porous hydroxyapatite (HA) bone graft substitute. METHODS Nine adult female dogs underwent extraction of premolars and molars and had a knife-edge ridge created. Three months later, the ridges were augmented with either M-TAM alone or M-TAM with a nonresorbable porous HA (Interpore 200; Interpore Cross International, Irvine, CA). Six months after augmentation, the dogs were killed, and the mandibles were harvested and imaged using 3-dimensional computed axial tomography. Statistical analysis was performed from the data obtained from the scans. The mandibles were then fixed, sectioned, and examined by light microscopy. RESULTS Dehiscence occurred in 22 of 32 experimental sites. Seven of these 22 dehisced sites showed increased ridge width. Ridge width increased in both the HA and non-HA groups. The HA group showed a greater increase in ridge width. CONCLUSIONS A high rate of dehiscence was observed in this animal study using M-TAM for guided tissue regeneration. In animals that did not dehisce, increased width was greater when nonresorbable porous HA was used as a bone graft substitute.