تاثير محيط هاي نگهداري مختلف بر استحكام اتصال برشي قطعات شكسته شده دندان هاي قدامي بازسازي شده با روش اتصال مجدد

The effect of different preservation environments on shear bond strength of fractured parts before re-attachment

Introduction: This laboratory study deals with the effect of various environments in which the fractured part is kept before being bond to the remaining tooth on the required force to fracture the restored teeth by a re-attachment method.Materials & Methods: Seventy two mandibular incisor teeth divided into six groups of 12. The samples in 5 groups were fractured on middle one third\ and the apical part of the remainders of teeth was dipped in normal saline. The environments where the fractured parts was kept in first to fifth group were, normal saline, water, milk, saliva and dry environment respectively. Sixth group was regarded as positive control group. After 24 hours all parts were bonded to the apical parts of the related groups by a bonding agent (Single Bond) and a flowable composite resin. The required force for the fracture was measured by a universal testing machine, and was analyzed by using Anova and Tukey statistical tests.Results: The required force to fracture the teeth in first to sixth group were 239.4, 231.2, 347.2, 328.6, 205.4, 693.3 Newton respectively. Statistical analyses indicated significant difference among the various groups (p value < 0.001). The required forces for the fracture in third and forth group were significantly higher than first, second and fifth groups.Conclusion: The required force to fracture the restored teeth is affected by placing the fractured parts in various environments before bonding.