RESUMEN
In order to improve the aesthetics and functional quality of restorations, the combined amalgam-composite restorations have been introduced. The aim of this study was to compare different reinforcement methods, in weakened buccal walls of premolar teeth. In this in vitro study, 70 similar and intact premolar teeth were used. The specimens were divided into seven groups of ten. In six groups, the three reinforcing materials composite [A], Compoglass F [B] and glass ionomer [C] with two methods: I: buccal and distal wall reinforcement. II: buccal, distal and pulpal floor reinforcement was used. In the seventh group [D], the Scotchbond M.P.P adhesive as a control group was applied. Then specimens were restored conventionally with amalgam and submitted to 500 thermal cycles [5°C-55°C]. The specimens were loaded through Instron testing machine at a crosshead speed of 1 mm/min with angle of 45 degree. Statistical analyzes of ANOVA, Duncan and chi- square tests were used to analyse fracture strength, location and type of fracture. The highest strength was detected in group with composite reinforcement on buccal and distal walls and pulpal floor. The highest failure mode was adhesion type and observed in composite reinforcement and control group. The highest cohesive and mixed failure mode was respectively observed in Compoglass and glass ionomer groups. This study showed that composite resin was the best material for reinforcement of weakened walls with favourable aesthetic property