Effects Of Different Surface Treatments On The Bond Strengths Of Glass Ionomer Cements To Enamel

Objectives:The aim of this study evaluated the effect of different surface treatments on bovine enamel bond strengths of conventional and resin-modified glass ionomer cements and analyzed the enamel-cement interfaces.Methods:Fifty-four non-carious bovine incisors were prepared into rectangular blocks. After all labial enamel surfaces had been serially wet-ground with SiC abrasive paper, ending with 4000-grit SiC paper,24 incisors were randomly assigned into four groups according to four cements (two conventional glass ionomer cements (GIC):Fuji I (GC, Japan), Ketac Cem Easymix (3M ESPE, Germany), and two resin-modified glass ionomer cements (RMGIC):Fuji Plus (GC, Japan), RelyX Luting (3M ESPE, Germany)). Forty-eight polished enamel surfaces were acid-etched for 15 s, or conditioned with polyalkenoic acid for 15 s; or they were no further treatment (control). Subsequently, they had been water-sprayed for 30 s, and gently air-dried, before two pretreated enamel surfaces were glued together with one of the four cements under finger pressure for 5 min. After the specimens at enamel-cement interfaces had been covered by Vaseline, and stored in water for 24 h, halves of them were perpendicularly sectioned through the enamel-cement interfaces, preparing into beams about 1x1x9 mm forμTBS tests with micro-tensile tester (Bisco Co. USA). The others were perpendicularly sectioned through the enamel-cement interfaces to expose enamel-cement interfaces. They were prepared into three 1-mm thick pieces per specimen. And those specimens were respectively immersed for 5 s,10 s, or 30 s in 0.1 mol/1 HC1. Another 6 enamel surfaces were pretreated as above-mentioned. All the specimens to be observed by scanning electron microscope (SEM) were dehydrated in ascending concentrations of ethanol and gold sputter-coated. The micro-morphologies of the cement-enamel interfaces and the pre-treated enamel surfaces were analyzed by SEM (ULTRA 55; ZEISS, Germany). The data were analyzed with factorial design ANOVA, and Post Hoc LSD for multiple comparisons.Results:Compared with control, phosphoric acid significantly increased enamel pTBS of GIC (Fuji I, Ketac Cem Easymix) and RMGIC (RelyX Luting, Fuji Plus) (p<0.01). Regardless of etching, RMGIC (RelyX Luting, Fuji Plus)yielded stronger enamelμTBS than GIC (Fuji I, Ketac Cem Easymix) (p<0.01). Moreover, among of all, Fuji Plus possessed the strongest enamel bond strength when enamel was etched by 37% phosphoric acid. Polyalkenoic acid conditioning produced less enamelμTBS (Ketac Cem Easymix and Fuji Plus) (p<0.05), or no stronger enamelμTBS (Fuji I and RelyX Luting) than control (p>0.05). SEM revealed a visible hybrid layer at etched enamel-cement interfaces, except Ketac Cem Easymix and indistinct hybrid layer at unetched enamel-cement interfaces. The enamel etched by phosphoric acid and conditioned by polyalkenoic acid (Fuji I, Ketac Cem Easymix) revealed a distinct etching pattern, and the enamel conditioned by polyalkenoic acid (RelyX Luting, Fuji Plus) revealed indistinct etching pattern.Conclusions:Phosphoric acid etching could significantly increase enamelμTBS of GIC/RMGIC. Polyalkenoic acid conditioning could significantly reduce enamelμTBS of Ketac Cem Easymix and Fuji Plus, or not increase enamel uTBS of Fuji I and RelyX Luting. RMGIC produced significantly stronger enamelμTBS than GIC. A visible hybrid layer was found at etched enamel-cement interfaces, except Ketac Cem Easymix.