管理された破断フラグメント再接着：表面処理と面取り技術が破折抵抗に及ぼす影響
Vasfiye Isik1, Soner Sismanoglu2
1Department of Endodontics, Faculty of Dentistry, Istanbul University-Cerrahpaşa, Istanbul, Turkey.
Background/Aim:
Fragment reattachment is a conservative option for anterior crown fractures, yet failure after the initial procedure creates a clinical dilemma. Evidence on effective retreatment strategies is lacking. This study investigated how surface preparation and chamfer design influence fracture resistance and failure patterns in failed fragment reattachments.
Materials And Methods:
Sixty bovine mandibular incisors were sectioned 3 mm below the incisal edge and reattached using a standardized protocol with adhesive and flowable composite. After thermocycling (5000 cycles, 5°C-55°C), baseline fracture resistance was measured. Specimens were stratified by baseline values and randomly assigned to four groups (n = 15): Group A-bur cleaning + simple reattachment, Group B-sandblasting + simple reattachment, Group C-bur cleaning + external chamfer, and Group D-sandblasting + external chamfer. Re-reattachment used the same adhesive protocol; in Groups C and D, a 1 mm external chamfer was prepared and restored with nanohybrid composite. post-treatment fracture resistance was tested with a universal testing machine, and percentage improvement was calculated. The specimens were examined with a stereomicroscope, and failures were categorized as adhesive, cohesive, or mixed. data were analyzed with two-way repeated measures ANOVA, Bonferroni post hoc, and Chi-square tests (p < 0.05).
Results:
All groups showed significant increases in fracture resistance after re-reattachment (p < 0.05). ANOVA revealed significant effects of time, group, and time × group interaction (All p < 0.001). Group D achieved the highest post-treatment resistance, significantly greater than all others (p < 0.01). Group C ranked second, while Groups A and B did not differ (p = 0.111). Failure mode distribution differed significantly (p < 0.001); chamfer groups (C and D) showed more cohesive/mixed failures.
Conclusion:
External chamfer, especially combined with sandblasting, enhanced fracture resistance and shifted failure patterns, indicating a clinically promising strategy for failed fragment reattachments.
