Managing Failed Fragment Reattachment: Influence of Surface Preparation and Chamfer Technique on Fracture Resistance

Fragment reattachment is a preferred, conservative treatment for anterior crown fractures. However, when these reattachments fail, clinicians lack evidence-based protocols for successful retreatment. This study investigated whether specific surface preparation methods (bur cleaning vs. sandblasting) and retention designs (simple reattachment vs. external chamfer) could improve the fracture resistance of failed fragment reattachments.

Researchers used 60 bovine mandibular incisors, creating standardized crown fractures and performing an initial reattachment. After thermocycling to simulate aging, the specimens were divided into four groups to test different retreatment strategies: simple reattachment with bur cleaning, simple reattachment with sandblasting, external chamfer with bur cleaning, and external chamfer with sandblasting. The researchers then measured the fracture resistance of these re-reattached specimens using a universal testing machine and analyzed the failure modes (adhesive, cohesive, or mixed) using a stereomicroscope.

All tested protocols resulted in increased fracture resistance compared to baseline. The combination of sandblasting and an external chamfer (Group D) yielded the highest fracture resistance, significantly outperforming all other groups. Sandblasting alone (Group B) was the second most effective strategy. Furthermore, the use of an external chamfer shifted failure patterns from predominantly adhesive (separation at the interface) to more cohesive and mixed failures, suggesting a stronger, more durable bond that effectively redistributes stress away from the adhesive interface.

This study provides a practical, evidence-based strategy for managing the common clinical dilemma of failed fragment reattachments. By demonstrating that a combination of sandblasting and a shallow external chamfer can refresh the compromised bonding surface, the findings offer a reliable, minimally invasive way to restore fractured teeth without resorting to more extensive prosthetic interventions.