Abstract: Objective To explore the clinical efficacy of making union crown restoration with adjacent tooth after hemisection to repair and retain molar teeth. Methods 43 patients, a total of 52 molar teeth which have individual root fracture，or individual root with serious periodontal disease or periapical disease were involved in the study, and root canal therapy and periodontal treatment were conducted after hemisection. Three months later, whether to fill the medullary cavity with resin or to make fiber post-core were decided according to the defect case of retained tooth body, and then union crown restoration with adjacent tooth were made. After follow-up for 2-3 years, clinical and radiological examination was carried out. Results 52 teeth which were repaired with union crown restoration with adjacent tooth after hemisection all had good masticatory function, with restorations kept solid, crown edges closed, and periodontal tissue in good health. X-ray showed new bone formation or no progressive bone resorption. The success rate was 100% during the follow-up period. Conclusions Hemisection has important clinical implications on preserving molar tooth which has individual root fracture, or serious periodontal disease and periapical disease. The use of union crown restoration with adjacent tooth can be a good method to restore the teeth morphology and occlusal function as long as the indications were strictly selected.

Key words: molar teeth, hemisection, linked crown