Root filled premolar teeth restored with silorane and methacrylate-based resin composite

Abstract
Objectives
To compare fracture characteristics of root-filled teeth with variable cavity design restored with a low shrinkage silorane and methacrylate-based resin composite.

Methods
77 extracted maxillary premolars were divided randomly into seven groups; 1) intact teeth; Group 2, 3 and 4) MOD plus endodontic access with the buccopalatal width of the occlusal isthmus equals one third of the intercuspal width; Group 5, 6 and 7) MOD plus endodontic access with the buccopalatal width of the occlusal isthmus equals one half of the intercuspal width. Group 2 and 5 were left unrestored, group 3 and 6 were restored with a silorane-based resin composite (Filtek P90) and group 4 and 7 with a methacrylate- based resin composite (Z250). Teeth were loaded in a universal testing machine; load and fracture patterns were recorded and compared statistically using 2-way ANOVA and t-test for pairwise comparisons and 1-way ANOVA with Dunnett test for multiple comparisons.

Results
Unrestored teeth became progressively weaker with more extensive preparations, group 5 (Unfilled ½) showed the lowest fracture load among the groups (71 ± 22 N, P < 0.001). Restorations increased the fracture strength of unrestored teeth regardless of cavity size (P < 0.001), but was still significantly weaker than sound teeth, with no significant difference between silorane and methacrylate groups. Failure of restored teeth was mostly adhesive at the tooth restoration interface.

Conclusions
Silorane-based resin composite have no superior strengthening effect over the conventional methacrylate-based resin composite in restoration of root filled teeth. Both materials showed similar fracture patterns.

Clinical significance: Root filled teeth are considerably weakened via restorative and endodontic procedures. A direct adhesive restoration will aid in preserving tooth structure as far as it provides enough strength.