Effectiveness of microscope-assisted root canal treatment in permanent posterior teeth: A retrospective cohort study.

OBJECTIVE: To evaluate the effect of microscope-assisted nonsurgical endodontic treatment on the clinical success rate in posterior teeth and to elucidate the interrelationship among various contributing factors. MATERIALS AND METHODS: This retrospective cohort study included 337 teeth (from 301 patients) that underwent microscope-assisted root canal treatment (RCTx) and 298 teeth (from 256 patients) that underwent nonmicroscopic RCTx. All patients' electronic medical records and periapical radiographs were uniformly recorded. Strict and loose criteria were adopted to assess treatment success. Multiple logistic regression models were utilized to investigate the prognostic factors. RESULTS: Significant differences were observed based on strict criteria regarding number of roots, number of canals, extra canal, swelling, sinus tract, palpation pain, deep and narrow pocket, apical lesion size, root resorption, secondary RCTx (2 degrees RCTx), and periapical diagnosis (p < 0.05). Compared to nonapical lesion cases, the odds ratios of success in cases with preoperative apical lesions below 5 mm and at least 5 mm were 0.16 and 0.06 times, respectively (p < 0.001). The odds ratio of success for 2 degrees RCTx was 0.35 times that of primary RCTx (1 degrees RCTx) (p < 0.001). "Apical lesion size," "treatment type," and "RCTx with aid of microscope" were significantly correlated (p < 0.001) based on strict criteria. "RCTx with aid of microscope" was significantly correlated (p < 0.05) based on loose criteria. CONCLUSION: Compared with traditional RCTx, microscope-assisted RCTx in posterior teeth resulted in a 2.9-fold and 3.2-fold increase in positive outcomes based on strict and loose criteria, respectively. CLINICAL SIGNIFICANCE: Microscope-assisted RCTx may help manage difficult root canal referral cases and provide a better prognosis.