Fracture Behaviour of Reattached Incisor Fragments with Mini FRC Anchors
Objectives: To assess the influence of mini fibre reinforced composite (FRC) anchors on the in-vitro fracture behaviour of reattached coronal fragments of incisors. Methods: Forty-five extracted sound central upper incisors were selected. The specimens were cut horizontally with a diamond blade of 0.25mm, 4 mm below the incisal edge to simulate fracture. Three restoration procedures to replace the fragment were tested with 15 randomly selected incisors for each group. In Groups A and B coronal fragments were reattached by bonding the fragment to the tooth (Panavia F, Kuraray). In Group B two mini FRC anchors (length 3mm; diameter 0,95mm) with approximately 100 glass fibres per anchor were adhesively placed in the tooth and corresponding holes were prepared in the coronal fragment, before bonding of the fragment. In Group C resin composite coronal build-ups (AP-X, Kuraray) were made. After restoration, all specimens were statically loaded under a loading angle of 45°. For each specimen fracture load was registered. Failure modes were characterised as adhesive or cohesive in the remaining tooth (or a combination). Results: Mean fracture loads were 255N (SD=108) for Group A, 599N (SD=465) for Group B and 786N (SD=197) for Group C. The differences between all groups were statistically significant (Kruskal-Wallis, p<0.05; post-hoc Mann-Whitney, p<0.05). In Group A only adhesive fractures were seen, while Groups B and C showed 73% and 53% cohesive fractures respectively (Chi-square, p<0.05). Conclusion: The results of this study suggest that application of mini FRC anchors increases the in-vitro fracture resistance of reattached coronal fragments in incisors. However, fracture of these reattached fragments seems to affect the remaining tooth more than those without FRC anchors.