ABSTRACT
Objective: Roughening of the aged composite resin core (CRC) surface seems essential for durable adhesion. The aim of this study was to investigate the influence of various surface treatments and different resin cements on microtensile bond strength (μTBS) between two aged core build‑up composites (CBCs) and feldspathic ceramic. Materials and Methods: A total of 16 composite blocks made of two CBCs, Core.it and Build‑it were randomly assigned to four surface treatment groups after water storage and thermocycling (2 weeks and 500 cycles). Experimental groups included surface roughening with air abrasion (AA), hydrofluoric acid, pumice, and laser and then were bonded to computer‑aided design/computer‑aided manufacturing feldspathic ceramic blocks using two resin cements, Panavia F2 (PF), and Duo‑link (DL). The μTBS was tested, and the fracture mode was assessed. The data were analyzed with multiple analysis of variance to estimate the contribution of different surface treatments, resin cements, and two aged CRCs on μTBS. Statistical significance level was set at α < 0.05. Results: Surface treatment and cement type significantly affected bond strength (P < 0.001) but the type of CRC did not (P = 0.468). Between roughening methods, the highest and the lowest values of μTBS were sequentially obtained in AA and Er.YAG laser groups. The highest bond strength was in AA group cemented with PF (31.83 MPa). The most common failure mode was cohesive fracture in the cement. Conclusion: Different surface treatments had different effects on μTBS of aged CRCs to feldspathic ceramics. PF was significantly better than DL.
ABSTRACT
Background: Bleaching products may show some side effects on soft and hard tissues and restorative materials in the oral cavity. This study evaluated the effect of carbamide peroxide gel with and without fluoride ions on the microhardness and surface roughness of tooth-colored restorative materials. Materials and Methods: In this in-vitro study, 76 cubic specimens (4 mm3 × 4 mm3 × 3 mm3) were fabricated from 4 aesthetic A3-shade restorative materials. These materials consisted of two composite resins and two glass ionomers. The specimens made from each material were treated with the following surface treatments: 1. Control group: The specimens were not bleached and were stored in normal saline. Group 2. Fluoridated 20% carbamide peroxide gel, treated 3 h a day for 4 weeks. Group 3. Treated 1 h a day with fluoride-less 22% carbamide peroxide for two weeks. From each group, three other specimens were selected to be evaluated in terms of changes in surface roughness, under scanning electron microscopy (SEM). Results: In this study, fluoridated 20% carbamide peroxide gel increased the microhardness of the four aesthetic restorative materials. The fluoride-free carbamide peroxide 22% reduced the microhardness of the four used materials, which this change was significant for Vitremer and Amelogen. SEM analyses showed changes in surface roughness of glass ionomer specimens. Conclusion: The effect of bleaching on the microhardness of restorative materials is material dependent. Before the application of bleaching systems on the glass ionomer materials, the application of a protective barrier should be considered.