Abstract: Objective: Analyzed clinical and rare features of one patient with rare mandibular bilateral second molar distal gingival tissue symmetry eruption of Complex odontoma, and combined with literature to explore the pathogenesis of the disease. Methods: Analyzed clinical data of one patient who was accurate diagnosed with rare mandibular bilateral second molar distal gingival tissue symmetry eruption of Complex odontoma in our hospital and reviewed literature. Results: The patient had no history of trauma ,special infection and genetic disease , The patient with rare mandibular bilateral second molar distal gingival tissue symmetry eruption of Complex odontoma without teeth shape, unsmooth surface, with the presention of solid calcified mass, and matching mandibular bilateral distal to the second molar occlusal surface consistent. Conclusion: We found Adolescent dental odontoma by X-ray examination, non trauma, infection, genetic history of the individual may also occur in peripheral of mixed odontoma, the sprouting output may be by means of molar eruption, symmetry which is relatively rare may be related with gene expression and regulation of the abnormalities in the tooth germ early development.

Key words: Peripheral odontoma, Complex odontoma, Erupted