Endodontic microsurgery is a highly predictable treatment option in most cases when conventional endodontic treatment is not feasible. Nevertheless, mandibular molars are still considered by clinicians to be the most difficult type of teeth, with the lowest success rate. In recent years, endodontic microsurgery has been attempted more frequently with the emergence of modern cutting-edge technologies such as dental operating microscopes, various microsurgical instruments, and biocompatible materials, and the success rate is increasing. This review describes the current state of the art in endodontic microsurgical techniques and concepts for mandibular molars. Notably, this review highlights contemporary equipment, technology, and materials.

The aim of this study was to evaluate the rat periodontal ligament cell viability under 0 o C/2 MPa condition up to one week using in vivo 3-(4,5-dimethylthiazol-2-y1)-2,5-diphenyltetrazolium bromide (MTT) assay.Materials and Methods: As soon as 110 upper molar teeth of rats were extracted, they were stored in Hartman's solution under 0 o C/2 MPa condition for 1, 2, 3, 4, and 7 days each. All specimens were treated with in vivo MTT assay and the value of optical density was measured by ELISA reader. These values were statistically analyzed by one-way ANOVA.Result: There was no statistical difference on MTT value between immediate and 1 day storage group. There were statistically significant differences between 1 day and 2 days storage, 2 and 3 days storage groups, respectively. Teeth of 3, 4, and 7 days storage groups showed significantly lower MTT values compared with shorter period storage groups. Conclusion:When the MTT values were substituted in standard curve, 1 day storage group at 0 o C/2 MPa condition showed 68% cell viability when compared with immediate group. It dropped to 13% at 2 days, and to less than 5% at 3 days or more.