Abstract
BACKGROUND: Preparation of the mesio-occluso-distal (MOD) cavity in maxillary premolars reduces their stiffness and fracture resistance. The maximum preservation of dental tissue is essential in minimally invasive dentistry (MID). The present study compared the fracture resistance of maxillary premolars with MOD cavities restored with composite resin, fiber-reinforced composite resin, and composite restorations with cusp coverage. METHODS: Forty-eight sound, extracted maxillary premolars were divided into four groups: group 1: intact teeth; in the other groups, MOD cavities were prepared (buccolingual: 3 mm, occlusal depth: 4 mm, gingival floor: 1 mm above the cementoenamel junction (CEJ), and axial depth: 1.5 mm); group 2: cavities restored using the incremental method with composite resin; group 3: after placing polyethylene fiber buccolingually in the pulp floor and extending it up to 2 mm of the buccal and lingual walls, restoration was performed; group 4: buccal and palatal cusps were reduced by 2 mm, and restoration was performed similar to group 2. After 24 hours of storage and thermocycling, the specimens were load-cycled. The fracture types were classified as favorable and unfavorable. Data were analyzed using analysis of variance, post hoc Tukey tests, and the Kruskal-Wallis test. RESULTS: The fracture resistance in groups 3 and 4 was similar to that of intact teeth. In group 2, the fracture resistance was significantly lower than in the other groups. The fracture type in the Ribbond group and intact teeth was similar (more favorable). CONCLUSION: Using Ribbond fiber and cusp coverage improved the fracture resistance of MOD restorations. Ribbond fiber resulted in a fracture type similar to that of intact teeth.