Compressive Strength of Four Dental Restorative materials: Effect of Time

Objectives: Compressive strength is one of the most important characteristics of a complex restoration in the posterior region. Sustainability of the baseline compressive strength after periods of time will ensure the longevity of the complex restoration in the oral cavity which consequently could prevent early failure and fracture of the restoration due to mastication forces. The aim of this study was to evaluate the effect of time(24hours,1 month,3 months) on compressive strength of four restorative materials, EQUIA glass ionomer,Hardcore composite,GCP compomer and Tetric Evoceram.
Methods: 18 cylindrical specimens of four restorative materials, EQUIA glass ionomer (GC, USA), Hardcore composite (Pulpdent, USA), GCP compomer (Vianen, Switzerland) and Tetric Evoceram (Ivoclar Vivadent, Liechtenstein) with 4mm diameter and 8mm length were prepared and divided into three time groups of 24hours,1 month,3 months. Specimens were stored in an incubator at 37°C and tested for compressive strength at the crosshead speed of 1mm/min in mentioned times. Results were analysed by ANOVA and Post- Hoc TUKEYHSD, with the significance level of 5%.
Results: Tetric Evoceram had the highest compressive strength in all times ( 236.56, 271.47, 278.23 in 24hours, 1 month and 3 months respectively) and it was significantly higher than other groups (P<0.001). Hard core and EQUIA had more compressive strength than GCP compomer in all time periods, but the difference between these groups was not statistically significant (P.0.05). Compressive strength rating in all groups in order of time was as follows:
24 hours:Tetric Evoceram>Hard core>Equia>GCP
1 month: Tetric Evoceram>Equia>Hard core>GCP
3 month: Tetric Evoceram>Hard core>Equia>GCP
Conclusions: According to the results of this study,Tetric Evoceram composite could be a promising composite resin restoration with favorable compressive strength in the posterior region over time compared to the other materials which were tested.