In Vitro Study Of The Sealing Ability Of Root Canal Obturation By System B With Obtura Ⅱ

Objective The aim of this study was to draw a comparison on the apical microleakage by using dye penetration technique following endodontic therapy of teeth obturated by System B with ObturaⅡthermoplasticized gutta-percha injection and lateral condensation of cold gutta-percha in combination with different root canal sealers. And the coronal sealing ability of root canal obturation was assessed by using three different restorative materials. This vitro study was to provide the experimental basis for the choice of perfect restorative materials and filling technique in clinic.Methods Experiment one: the root canals of 40 extracted single-root teeth were prepared with crown-down technique, and randomly divided into four experimental groups, positive and negative controls. The teeth of four experimental groups were filled with two obturation techniques: System B with ObturaⅡthermoplasticized gutta -percha injection (Group A) and lateral condensation of cold gutta-percha (Group B). The root canal sealer was used with AH-Plus (Group A1, Group B1) and ZOE paste(Group A2, Group B2), and the specimens of positive and negative controls in each group were filled without any paste. The depth of dyeing lines were visualized and measured by using dye (methylthionine chloride) penetration and clearing technique. The data were analyzed by SPSS13.0 software to have a comparison on the apical microleakage among different groups of teeth. Then, the apical sealing ability of different filling technique was evaluated. Experiment two: the root canals of 40 extracted single-root teeth were prepared with crown-down technique, obturated by System B with obturaⅡthermoplasticized gutta -percha injection in combination with the AH-Plus paste. Then, the coronal surface were all prepared as standardized cavity with the depth of 2mm and flat walls. According to different restorative materials, the experimental teeth were randomly divided into four groups, which were named as group A(composite resin, CR), group B(glass ionomer ), group C (amalgam), positive and negative controls. The positive and negative controls were unfilled and filled with adhesive wax, respectively. The depth of dyeing lines were visualized and measured by using dye(methylthionine chloride) penetration and clearing technique. The data were analyzed by SPSS13.0 software to have a comparison on the coronal microleakage among different groups of teeth. Then, the effects of three restorative materials on coronal sealing ability were investigated.Results Experiment one: In warm gutta-percha obturation groups, dyeing lines of AH-Plus group had an average length of(1.84±0.14 ) mm, which was shortest in all groups. Dyeing lines of ZOE group had an average length of(1. 96±0.17) mm. There were no significant differences between AH-Plus group and ZOE group. In cold lateral condensation groups, dyeing lines of AH-Plus group had an average length of (2.16±0. 23) mm, which was significantly shorter than that of ZOE group (2.89±0.15) mm. However, the different results were observed in warm vertical condensation groups. Dyeing lines of each group showed similar length [(1.84±0. 14 ) mm to (1. 96±0.17) mm, P > 0. 05 ] , which were significantly shorter than that of cold lateral condensation groups ( P < 0. 05). Experiment two: The mean dyeing line lengths for experimental groups(A, B, C) were(3. 34±0.16)(3. 22±0.21)(3. 16±0.25)mm, respectively. The order of the microleakage for light serious level to serious level in three groups was: group C(amalgam)﹤group B (glass ionomer)﹤group A (CR). Composite resin(3. 34±0.16)mm had the longest penetration depth. Depth of amalgam(3. 16±0.25)mm was shorter than that of the former two groups, but there were no significant differences among them(P < 0. 05). No dyeing lines were observed in the negative controls, whereas the dyeing lines were nearly filled with all the teeth in the positive controls unfilled.Conclusions1, In vitro study, the injection-thermoplasticized gutta-percha technique had more excellent adaptation to canal wall and better quality of the root fillings compared with lateral condensation;2,When the root canals were filled by using cold lateral condensation technique, AH-Plus showed a better apical sealing ability than ZOE as the root canal sealer with less periapical microleakage. In addition, warm vertical condensation technique could dramatically eliminate periapical microleakage of root canals, irrespective of the sealers used;3,Amalgam had the best peripheral density and exhibited less microleakage than the other restoration materials tested (composite resin, glass ionomer), however, no significant statistic difference existed.