BACKGROUND:Interproximal contact loss is a complication of posterior crown/bridge restorations with a higher incidence, and it is induced by a variety of factors, such as age, tooth position, occlusal contact, tooth loss time, whether there is a repair on the free end.OBJECTIVE:To study and analyze the loss of interproximal contact between posterior crown/bridge restorations and adjacent teeth.METHODS: This was a single-center, prospective, observational clinical trial which has been completed at the Stomatology Hospital Affiliated to Southwest Medical University, China. Totaly 82 patients who had underwent posterior crown/bridge restorations from June 2015 to June 2016 in the Stomatology Hospital Affiliated to Southwest Medical University were selected. The time of denture wearing was 1-40 months, and the interproximal contact loss was defined by a 30 μm adjacent contact check or a flossing that can pass through the detection area with no resistance. Single-factor analysis and multiple correlation analysis were performed to analyze the interproximal contact loss at 1, 3, 6 months after posterior crown/bridge restorations. The study protocol was approved by the Ethics Committee of the Stomatology Hospital Affiliated to Southwest Medical University of China with an approval number of 2016024. All protocols were in accordance with Declaration of Helsinki, formulated by the World Medical Association. All patients and their relatives were informed of study protocols and provided a written informed consent prior to the beginning of the trial.RESULTS AND CONCLUSION:Of the 82 patients enroled, there were 41 adjacent contact zones with the emergency of interproximal contact loss, including 20 maxillary and 21 mandibular. It indicated that the interproximal contact loss had no association with the upper and lower jaw. Single-factor analysis showed that the time of denture wearing, tooth loss time and repair of the free end were confirmed as independent influencing factors for the complications (P < 0.05). Multiple correlation analysis found that free end repair and short-term tooth loss were independent factors of the interproximal contact loss. To conclude, free end repair and tooth loss time should be considered in the posterior crown/bridge restorations in order to minimize the occurrence of interproximal contact loss.