Impact of photo-activation methods on resin composite properties

Impact of photo-activation methods on resin composite properties

Objectives: this study investigated the impact of different photo-activation methods on the properties of a model resin composite. Methods: the resin phase of the model material was composed of Bis-GMA (50wt%), TEGDMA (50wt%), camphorquinone (0.4wt%), dimethyl-p-toluidine (0.8wt%) and hydroquinone (0.1wt%); the inorganic phase was composed of silanated strontium glass fillers (75wt%). The following photo-activation methods were tested: high-intensity continuous (HIC=500mW/cm² for 20s), medium-intensity continuous (MIC=250mW/cm² for 40s), low-intensity continuous (LIC=100mW/cm² for 100s), pulse-delay-1min (PD-1min=100mW/cm² for 5s + 1min interval + 500mW/cm² for 19s), pulse-delay-3min (PD-3min=100mW/cm² for 5s + 3min interval + 500mW/cm² for 19s). Irradiance was performed using a halogen curing unit. Degree of conversion (DC) was evaluated using infrared spectroscopy. Flexural strength (FS) and modulus (FM) were obtained in a mini three-point bending test. Cross-link density (CLD) was estimated through weight alteration of cylindrical specimens after immersion in chloroform and calculation of swelling coefficient (a). Data were separately submitted to ANOVA and Student-Newman-Keuls test (5%). Results: Means±SD for all analyzes are shown in the Table (distinct letters indicate significant differences for each property).

Method	DC (%)	FS (MPa)	FM (MPa)	a (g/mL)
HIC	50.6±2.8a	174±29a	918±124a	0.19±0.08c
MIC	49.8±2.7a	144±34ab	748±107b	0.22±0.04bc
LIC	50.1±2.1a	130±35b	716±121b	0.25±0.02b
PD–1min	43.9±4.8b	138±31b	730±108b	0.25±0.01b
PD–3min	51.7±5.2a	111±13b	672±97b	0.30±0.02a

Conclusions: The different methods significantly interfered with the properties of the resin composite. In general, HIC showed the best outcomes for all properties, while MIC and LIC showed similar results to PD-1min and PD-3min. PD-1min and PD-3min showed lower FS, FM and lower CLD than HIC.