Taurodontism is a morphologic feature of generally multi-rooted teeth with large pulp chambers and shortened roots. A case of endodontic treatment in a 24-year-old male with the chief complaint of swelling and pain in the right mandibular region is described. Periapical lesion was present in the radiographic examination of hypertaurodont second mandibular molar.Four root canals were detected with an endodontic microscope. The canals were prepared and obturated with lateral condensation technique in the second appointment. The patient was asymptomatic in the 18-month follow-up.

Objective: This study aimed to assess the cytotoxicity and genotoxicity of triple antibiotic paste, double antibiotic paste and calcium hydroxide medicaments on human stem cells of the apical papilla. Methods: In this experimental study, stem cells were isolated from the apical papilla and cultured. They are treated with different concentrations 0.1, 0.5, 1, 10 and 100 mg/ml of medicaments for 24, 48 and 72 hours. The cytotoxicity and genotoxicity of the medicaments were determined using methyl thiazolyl tetrazolium assay and Comet test, respectively. Results: Results showed all tested concentrations of the calcium hydroxide had no significant effect on stem cells at any time point. Triple antibiotic paste showed cytotoxicity in 10 and 100 mg/mL concentrations at all-time points and in 1, 10 and 100 mg/ml concentrations at 72 hours. In addition, its genotoxicity was significantly higher than that of other groups (P<0.05). Double antibiotic paste showed cytotoxic effects only in 100 mg/ml concentration at 24 hours and 10 and 100 mg/ml concentrations at 48 and 72 hours. And also, its genotoxicity in these concentrations was significantly higher than that of control and calcium hydroxide groups (P<0.05). Conclusion: In contrast to calcium hydroxide, triple antibiotic paste and double antibiotic paste, especially in their higher concentrations, induced cytotoxicity and genotoxicity on human stem cells of the apical papilla.