Evaluation of the Shear Bond Strength of Fractured Permanent Central Incisors of Maxilla Restored with Fragment Reattachment Method Using Palatal Bevel Preparation, Buccal/Palatal Bevel Preparation and Composite Veneer : An In Vitro Study

Abstract

Introduction: Trauma to the anterior teeth is highly prevalent and epidemiological studies have shown that at least 30% of adolescents experience this event. Reattachment of the fractured part to the remaining part of the tooth has numerous advantages compared to other restorative methods. The purpose of this study was to evaluate and compare the shear bond strength of the permanent fractured central maxillary teeth that after bonding of the fractured incisal edge, the teeth have been repaired in different ways. Materials and Methods: This study was performed on 52 maxillary central teeth experimentally that were randomly divided into 3 experimental and one control group. The specimens were transversely fractured 3 mm away from the winning edge. Fifth generation Solobond M (Voco, Cuxhaven, Germany) bonding and Grandio Flow nano-hybrid (Voco, Cuxhaven, Germany) composite were used to paste the broken fragment in all groups. In the first group, which was considered as the control group, without any changes on the fractured teeth, only repair was done by fixing the fracture area using bonding and composite. Then in the second group, after fixing the fractured part, in the palatal part of the fracture area and in the third group in the labial and palatal part of the fracture area, the bevel preparation was done to a depth of half a millimeter and after bonding restoration was done using Polofil Supra micro-hybrid (Voco, Cuxhaven, Germany) composite. In the fourth group, after tooth preparation a half-millimeter composite veneer was applied to the labial surface using Polofil Supra micro-hybrid (Voco, Cuxhaven, Germany) composite. Then the amount of force needed to re-fracture at the palatal surface of the incisal edge was measured using universal testing machine and after calculating shear bond strength in MPa, comparison between groups was performed using SPSS17 software and Kolmogorov-Smirnov, one-way ANOVA, Levene's and Tukey's tests were conducted. Results: Mean and standard deviation of the shear bond strength in control group were 81.48± 8.18. In the group with palatal bevel preparation were 97.74± 11.41, in the group with labial and palatal bevel preparation were 131.56± 9.25 and in the composite veneer group were 104.36± 5.50 MPa. Significant differences were observed between the groups, but there was no significant difference between the groups with palatal bevel preparation and composite veneer. Conclusion: The results of this study showed that reattachment of the fractured part using all three methods used for tooth reconstruction increases shear bond strength. The highest shear bond strength was obtained using the labial and palatal bevel preparation, while there was no significant difference between the shear bond strength of the palatal bevel preparation and the composite veneer.