Microhardess and depth of cure of a spectrum of light-cure composite resins: a comparative study

To determine the proportion of composite resin materials that is capable of bulk or large incremental cure.

This study was carried out at the Dental Biomaterials and Biomechanics Laboratory, Dental School, University of Manchester, England. Six randomly selected composite resins and one experimental sample were employed for this study. The technique employed by Watts et al. was employed for the study. Knoop hardness number (KHN) was measured as a function of depth of the material at 0.2 mm intervals. One-Way ANOVA test and linear regression were used for statistical analysis.

Clearfil Majesty Posterior has the highest value for microhardness and depth of cure while Els extra low shrinkage A3 has the lowest value for micro hardness and depth of cure. Estelite 0 and Clearfil Majesty Posterior (28.6%) have depths of cure greater than 3.0 mm and may, therefore, be capable of large incremental cure. Gradia Dentin and Els extra low shrinkage A3 (28.6%) have depths of cure lesser than 2.0 mm while Filtek Silorane (experimental material) has a depth of cure of 2.4 mm. NEUN and Els extra low shrinkage A2 have depths of cure of 2.3 and 2.5 mm respectively.

It appears that Clearfil Majesty Posterior and Estelite 0 (28.6%) can effectively be cured in bulk or large increments. It is imperative to investigate the depth of cure of composite resin materials before using them in bulk or large increments.