In Vitro Fracture Resistance of Permanent Molars with Undermined Walls Restored With Different Materials and Techniques

Restoration of freshly erupted permanent first molars with extensive caries is a challenge in pediatric dentistry. This study aimed to compare the fracture resistance of permanent molars with undermined walls restored with amalgam and composite resin along with cusp reduction, reinforcement of the walls with glass ionomer (GI) or no further intervention. This experimental in-vitro study evaluated 72 freshly extracted sound human third molars with almost equal dimensions. After cavity preparation, the teeth were then randomly divided into three groups. In group 1, the undermined area was reinforced with light-cure GI. Group 2 received a 2 mm cuspal cap, and group 3 received no intervention. Half of the teeth in each group were restored with composite resin and the other half with amalgam. The teeth then underwent thermocycling and their fracture resistance was measured by a universal testing machine. Data were analyzed using two-way ANOVA. No significant difference was noted in fracture resistance among three procedures in teeth restored with composite (P=0.589). However, this difference was significant in teeth restored with amalgam (P=0.001). The current results indicated when esthetics is not a priority, applying amalgam restorations with GI-reinforced undermined walls might be suitable for restoration of freshly erupted permanent first molars with extensive caries.