ABSTRACT
BACKGROUND/AIMS: Radiotherapy makes teeth prone to tooth fractures. However, the relationship between radiotherapy and maximum load to fracture teeth that suffered a crown fracture is not fully understood. The aim of this study was to evaluate the influence of fracture type, radiation dose, fracture time, and their interactions on maximum load to fracture irradiated teeth. MATERIAL AND METHODS: A total of 140 permanent incisors were divided into two fracture type groups (uncomplicated and complicated) each of which included seven radiation dose subgroups (0, 10, 20, 30, 40, 50, and 60). The test groups were exposed to high-energy X-ray at 2 Gy/day, 5 days/week for a total dose of 10-60 Gy. Control groups were not irradiated. The load where the specimen started to break was obtained two different times. The 1st fracture was performed after radiation therapy, and the 2nd fracture was performed after the restoration of these samples. RESULTS: Fracture type had no effect on the maximum load to fracture. In contrast, the maximum load to fracture teeth decreased with increasing radiation doses. Maximum load to fracture the restored teeth was lower than the 1st fracture results. The general linear model procedure revealed a significant interaction between radiation dose and fracture time. Similarly, there was a significant interaction between the fracture type, radiotherapy dose, and fracture time. Maximum load values of teeth with complicated crown fractures restored with fiber posts and composite were not affected by radiation. CONCLUSION: Teeth that have been subjected to radiotherapy have an increased risk of fracture during dental trauma. However, restoration of the irradiated teeth with fiber posts and composite resin did not affect the maximum load required to fracture them.