Effect of Light Activation on Resin-modified Glass Ionomer Shear Bond Strength

Abstract

SUMMARY Objective Recent studies confirmed that resin-modified glass ionomers (RMGIs) set on the basis of two competing mechanisms, an acid-base reaction and a light-activated resin polymerization. This study evaluated the effect of the setting mechanism on bond strength by measuring the shear bond strength of three RMGIs to dentin with and without light activation. Methods Sixty human molars were ground to midcoronal dentin and randomly divided into six even groups: 1) Ketac Nano (KN), 2) KN without light cure (woLC), 3) Fuji Filling LC (FF), 4) FF woLC, 5) Fuji II LC (FII), and 6) FII woLC. The dentin surfaces of the specimens were conditioned/primed according to the manufacturers' instructions. A 1.54-mm diameter plastic tube was filled with RMGI material and affixed to the dentin surface. Groups 1, 3, and 5 were light cured for 20 seconds, and groups 2, 4, and 6 were immediately placed in a damp dark box with no light curing at 37°C for 24 hours. Shear bond strength testing was performed in an Instron device at 1 mm/min. Data were analyzed with a one-way analysis of variance (ANOVA) and Tukey/Kramer test (α=0.05). Results Mean ± standard deviation shear bond strength values (MPa) are: 7.1 ± 4.2 (KN), 11.7 ± 3.9 (FF), 10.2 ± 3.2 (FF woLC), 12.5 ± 5.1 (FII), and 0.3 ± 0.4 (FII woLC). Two KN, all KN woLC, and seven FII woLC specimens debonded before testing. Tukey/Kramer analysis revealed no significant differences in bond strength between the three light-cured RMGIs. KN and FII showed significantly lower bond strength without light cure, but no significant difference was observed between FF and FF woLC. Conclusions The results of this study strongly suggest that light activation is necessary to obtain optimal bond strength between RMGI and dentin. FF may contain components that chemically activate resin polymerization. Clinically, KN and FII need to be light cured after placement of these RMGIs.

Advances in Resin-Based Dental Composite Materials

“…Lowson et al prepared a kind of resin modified glass ionomer cements (RMGICs), which were composed of polyelectrolyte solution, hydroxyethyl acrylate (HEMA)/water mixture, and a small amount of photoinitiator for polymerization of HEMA [12]. When this RMGIC is exposed to ultraviolet radiation, it quickly hardens.…”

Assessment of influence of LED curing units used on microhardness of resin-modified glass ionomer sealants

“…As this is a hybrid material, the setting reaction of RMGI sealant is initiated by light activation of the resin component, followed by the acid-base reaction of the ionomer component 1 . Although it has been suggested that the latter reaction can compensate the light attenuation that occurs in deeper areas to increase the depth of cure of RMGI 9 , the main mechanism responsible for the curing process of this type of material is light activation 8,10 . Therefore, their physical and mechanical properties can be greatly affected by factors related to the curing process 11,12 .…”