Evaluation of the Viability of Rat Periodontal Ligament Cells after Storing at 0℃/2 MPa Condition up to One Week: In Vivo MTT Method

PURPOSE: The aim of this study was to evaluate the rat periodontal ligament cell viability under 0℃/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℃/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 tsorage, 2 and 3 days storage groups, respectively. Teeth of 3,4, and 7 days storage groups showed significantly lower MTT valuesc ompared with shorter period storage groups. CONCLUSION: When the MTT values were substituted in standard curve, 1 day storage group at 0℃/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.

Does apical root resection in endodontic microsurgery jeopardize the prosthodontic prognosis?

Apical surgery cuts off the apical root and the crown-to-root ratio becomes unfavorable. Crown-to-root ratio has been applied to periodontally compromised teeth. Apical root resection is a different matter from periodontal bone loss. The purpose of this paper is to review the validity of crown-to-root ratio in the apically resected teeth. Most roots have conical shape and the root surface area of coronal part is wider than apical part of the same length. Therefore loss of alveolar bone support from apical resection is much less than its linear length.The maximum stress from mastication concentrates on the cervical area and the minimum stress was found on the apical 1/3 area. Therefore apical root resection is not so harmful as periodontal bone loss. Osteotomy for apical resection reduces longitudinal width of the buccal bone and increases the risk of endo-perio communication which leads to failure. Endodontic microsurgery is able to realize 0 degree or shallow bevel and precise length of root resection, and minimize the longitudinal width of osteotomy. The crown-to-root ratio is not valid in evaluating the prosthodontic prognosis of the apically resected teeth. Accurate execution of endodontic microsurgery to preserve the buccal bone is essential to avoid endo-perio communication.