The effect of low shrinkage dental composite on th efracture strength of weakened premolar teeth : an in vitro study

الملخص EN

Background : The aim of the study was to evaluate and compare the fracture resistance of weakened maxillary premolar teeth with MOD preparations restored with low shrinkage new Silorane based composite (Filtek p90) in comparison to low shrinkage methacrylate based composite (1-packable Filtek p60, 2- nanohybrid Tetric Evoceram).

Materials and Metods : Fifty human adult maxillary premolar teeth recently extracted for orthodontic purpose were selected.

These teeth received MOD cavity preparations with no proximal boxes.

The teeth were then randomly divided in to five groups (n = 10), according to the material used for restoration : Group A (Teeth were not prepared), Group B (Teeth, with MOD cavity preparation were not restored.) Group C (Teeth, with MOD cavity preparation were restored with Filtek p60 packable composite), Group D (Teeth, with MOD cavity preparation were restored with Tetric Evoceram nanohybrid composite) Group E (Teeth, with MOD cavity preparation were restored with Filtek p90 silorane based composite).

These specimens were then stored in an incubator at 37Ċ for one week, at 100% humidity in deionized water before test.

Cuspal fracture resistance was determined using compressive testing machine.

The fracture specimens in group C, D and E were stained with 1% methylene- blue dye for 24 hours then examined by stereo microscope ×40 to evaluated the mod of failure, the data were statistically analyzed using Analysis of variance test (ANOVA), LSD test and student t-test .

Results : The results showed that there’s a high significant improvement of the fracture resistant of restored teeth using posterior composite as compared to the unrestored ones, but ; ther’s no difference of the type of the posterior composite material used on the fracture resistance of the weakened teeth, while the sound teeth remained the strongest teeth compared with all the other groups.

Examination of the fractured specimens of GC, G D and G E using stereo microscope revealed that for Group C and group D, 70% and 50% cohesive failure respectively while for group E 70% showed adhesive failure.

Conclusion : Posterior composite resin restoration whatever material type used for packing it, showed a great improvement in the resistance to Cuspal fracture, Silorane based composite show little improvement in fracture resistance by means value in comparison to methacrylate based composite although statistically there is no significant difference between them.