Surface treatment of RMGIC to composite resin using different photosensitizers and lasers: A bond assessment of closed Sandwich restoration.

AIM: The aim of present study was to assess and compare different conditioning methods (laser, PDT and conventional) on shear bond strength (SBS) of resin modified glass ionomer cement (RMGIC) bonded to composite (sandwich technique). MATERIAL AND METHODS: Fifty specimens were prepared from RMGIC and were packed in a teflon mould placed on glass slab. Through each of the glass slab the cement was light cured for 20 s. Now samples were randomly allocated into five groups (n = 10) according to pre-treatment protocols. In group 1 RMGIC were conditioned with MBP using PDT, Samples in group 2 treated with Er,Cr:YSGG (ECYL), group 3 pre-treated with Nd:YAG laser (NYL), samples in group 4 surface conditioned with air abrasion (AA) and group 5 conditioned with 37 % phosphoric acid (PA). Specimens after conditioning were rinsed with distilled water. Adhesive Adper Single Bond 2 was applied on treated surface of RMGIC and cured. Teflon mold was utilized to hold the composite Filtek Z250 in an incremental technique. For SBS testing all specimens were placed under shear knife edge at 1 K N at a speed of 0.5mm(2) until bond failure. Optical microscope was used to evaluate failure pattern at 10x magnification. The data of SBS in Megapascal were subjected to statistical test. Analysis of variance was followed by Post hoc test with level of significance at 5 %. RESULT: The maximum SBS was found in group 5 RMGIC conditioned with 37 % PA (16.45 +/- 0.32 MPa). Whereas, group 1 (MBP, PDT) demonstrated significantly lower bond integrity (9.82 +/- 1.08 MPa) compared to all experimental groups. Bond integrity of RMGIC surface treated with MBP, PDT (9.82 +/- 1.08 MPa), group 3 lased with NYL (11.47 +/- 0.53 MPa) and samples in group 4 conditioned with AA (11.23 +/- 0.47 MPa) were comparable (p > 0.05). CONCLUSION: ECYL has a potential to be used for conditioning of RMGIC prior to composite restoration (sandwich technique). MBP at 100 mg/L deteriorates SBS of composite to RMGIC.