Purpose: The aim of this animal study was to evaluate new bone formation in human dentin block grafted on rabbit calvaria according to a comparison of histologic analysis. Materials and Methods: Human teeth were prepared according to four different types of dentin blocks: group 1, demineralized and microperforated dentin block; group 2, demineralized dentin block; group 3, undemineralized and microperforated dentin block; group 4, undemineralized dentin block. These four different dentin blocks were grafted on nine rabbit calvaria, and animals were sacrificed at 2, 4, and 8 weeks after the surgical procedure for histologic evaluation. Results: In group 1, histologically, new bone formation was initiated at the interface between demineralized and microperforated dentin block and host bone and microholes at 2 weeks, and mature bone was observed at 8 weeks. In group 3, new bone formation was observed at 8 weeks in the undemineralized and microperforated dentin block bottom and microholes. The bone formation ratio of group 1 was significantly higher at 2, 4, and 8 weeks compared with groups 2, 3, and 4 (P .05). The bone formation ratio in microholes at 2 and 8 weeks in group 1 was significantly greater than in group 3 (P .05). Conclusion: New bone formation of the demineralized dentin block began more rapidly than the undemineralized dentin block, and perforated dentin block was more effective in bone formation than dentin block without microholes. Keywords: demineralization, dentin block, new bone formation, ridge augmentation, tooth block bone