An in vitro comparison of the root fracture resistance of endodontically treated teeth using five different root canal treatment techniques

The major aim of endodontic therapy is to attain a clean root canal, which allows the three-dimensional obturation of the root canal. The strength of an endodontically treated tooth is directly related to the amount of remaining sound tooth structure. Vertical root fractures are severe complications that are seen in root filled teeth, which often leads to extraction. The purpose of the present study was to compare the fracture resistance of teeth obturated with gutta-percha/AH Plus, Thermafil/AH Plus, Resilon/Epiphany SE, EndoREZ obturation system and gutta-percha/Epiphany SE. Root canals were shaped with K3 NiTi rotary instruments using a crown-down technique and filled with the root canal filling materails in the experimental groups. The apical 4 mm of the specimens were mounted vertically into cast metal rings filled with self-cure acrylic resin exposing 9 mm.of the coronal part. The materials were stored in incubator at 37ºC to allow complete setting of the sealers for 1 week. After 1 week, the acrylic resins were placed on the lower plate of the Universal testing machine. The load at which failure occured was recorded and expressed in Newtons. The data were analyzed using a oneway Anova test for the experimental groups.Significance between the groups was tested with Tukey HDS test. All statistical analysis was performed using the NCSS 2007&PASS 2008 Statistical Software (Utah, USA). The results indicated that there was no statistically difference between the fracture values of the (-) Control, gutta-percha + AH Plus, Thermafil + AH Plus and gutta-percha + Epiphany SE groups (p>0.05). On the other hand, the (-) Control group had significantly higher fracture values than the Resilon + Epiphany SE and EndoREZ groups (p<0.05).The fracture resistance values of the (+) Control group was statistically lower than the (-) Control, gutta-percha + AH Plus, Thermafil + AH Plus(p<0.01), and gutta-percha + Epiphany SE groups (p<0.05). Also, the difference between the (+) Control, Resilon + Epiphany SE and EndoREZ groups was not significant. According to these results; instrumentation of the root canals decreases the fracture resistance of the teeth. The fracture resistances of teeth obturated with gutta-percha + AH Plus, Thermafil + AH Plus and gutta-percha + Epiphany SE are similar to sound teeth. This result implies the reinforcing effect of these filling materials. On the other hand, the fracture resistances of teeth obturated with Resilon + Epiphany SE and EndoREZ are not significantly different than instrumented but unfilled group, indicating that these filling materials do not increase the fracture resistance of endodontically treated teeth.