In vitro Study Comparing Fracture Resistance of Nanocomposites with and without Fiber Reinforcement with Different Cavity Designs Used for Obliquely Fractured Incisal Edge Restoration

Abstract

Aim:The aim of the study is to evaluate fracture resistance of nanocomposites with and without fiber reinforcement with different cavity designs used for obliquely fractured incisal edge restoration. Materials and methods: In the present study, 60 sound extracted maxillary central incisors were mounted on autopolymerizable acrylic resin up to the cementoenamel junction, out of which, 10 intact teeth were kept as control (group 1) and the remaining 50 samples were reduced incisally in an oblique manner up to 3 mm. All incisally reduced samples were divided into five groups (n = 10) based on the restoration techniques as follows: group 2 (conventional bevel), group 3 (single central palatal slot on the incisal edge), group 4 (single palatal slot with central 2 mm fiber), group 5 (two palatal slots on the incisal edge with a distance of 0.5 mm to 1 mm between them), and group 6 (two slots on the incisal edge with two 2 mm fibers). All samples were built incrementally with nanocomposites followed by finishing and polishing. All samples including control were then stored in distilled water before their fracture resistance was measured using a universal testing machine. Failure modes were visually examined and the results were subjected to statistical analysis. Results: The mean fracture resistance among the experimental groups was observed, group 4 with single fiber in the central position had the highest (832.68 N) followed by group 3 (490.84 N), group 5 (446.175), and group 2 (270.1359), and the least in group 6 (223.443). The mean fracture resistance of group 4 is comparable to intact teeth, i.e., group 1 (1096.40). The mean of all samples was compared using the one-way Anova test, and it was found that there is statistically significant difference in fracture resistance among groups (p < 0.001**). Conclusion: Fibers certainly have the reinforcing effect and the position of fibers determines their reinforcing effects. A single central slot with fiber (Ribbond) showed maximum fracture resistance almost equivalent to natural teeth. Modifying conventional beveled cavity design with an additional slot in the center also increases the fractural strength of restoration. Clinical significance: Nanocomposites reinforced with single fiber in the central palatal slot used for restoring fractured incisors provide strength almost equivalent to natural teeth. In case when the fiber is not available for preparing a single palatal slot also, we can increase the fracture resistance.

Comparative evaluation of impact strength of natural tooth and two different fragment reattachment technique

“…However, in contrast to the common perception, in a study conducted by Gayatri et al, a single ribbond fiber showed more fracture resistance as compared to two fibers. 33 Also Sharafeddin et al 31 discovered that samples with two fibers in two slots had lower fracture resistance than single fiber samples. Because a centrally located fiber is closer to the long axis of the tooth, it appears to distribute forces equally across a wider area of the tooth, however, when it is placed farther from the center, the force is dispersed unevenly to other parts.…”