Abstract
Interface integrity can be maintained by setting the composite in a layering technique and using liners. Objective The aim of this in vitro study was to verify the effect of resin-modified glass-ionomer cement (RMGIC) lining and composite layering technique on the bond strength of the dentin/resin adhesive interface of lateral walls of occlusal restorations.Material and Methods Occlusal cavities were prepared in 52 extracted sound human molars, randomly assigned into 4 groups: Group 2H (control) – no lining + two horizontal layers; Group 4O: no lining + four oblique layers; Group V-2H: RMGIC lining (Vitrebond) + two horizontal layers; and Group V-4O: RMGIC lining (Vitrebond) + four oblique layers. Resin composite (Filtek Z250, 3M ESPE) was placed after application of an adhesive system (Adper™ Single Bond 2, 3M ESPE) dyed with a fluorescent reagent (Rhodamine B) to allow confocal microscopy analysis. The teeth were stored in deionized water at 37oC for 24 hours before being sectioned into 0.8 mm slices. One slice of each tooth was randomly selected for Confocal Laser Scanning Microscopy (CLSM) analysis. The other slices were sectioned into 0.8 mm x 0.8 mm sticks to microtensile bond strength test (MPa). Data were analyzed by two-way ANOVA and Fisher’s test.Results There was no statistical difference on bond strength among groups (p>0.05). CLSM analysis showed no significant statistical difference regarding the presence of gap at the interface dentin/resin among groups.Conclusions RMGIC lining and composite layering techniques showed no effect on the microtensile bond strength and gap formation at the adhesive interface of lateral walls of high C-factor occlusal restorations.
Highlights
Resin-based restorative materials have been widely used in contemporary restorative dentistry[3], the polymerization shrinkage, inherent characteristic of dental composites, induces stress during the curing of the resin composites, and this is still a great drawback[5,17,33].It is widely accepted that volumetric contraction and solidification during the polymerization process of restorative composites in combination with bonding to the hard tissue results in stress transfer and inward deformation of the cavity walls of the restored tooth[21]
The shrinkage stress is transferred to the surrounding tooth structure, since it restricts the volumetric changes[18,26]
There was no difference in microtensile bond strength to dentin between groups with or without resinmodified glass-ionomer cement lining (p=0.063) and between the different composite layering technique (p=0.272)
Summary
Resin-based restorative materials have been widely used in contemporary restorative dentistry[3], the polymerization shrinkage, inherent characteristic of dental composites, induces stress during the curing of the resin composites, and this is still a great drawback[5,17,33]. It is widely accepted that volumetric contraction and solidification during the polymerization process of restorative composites in combination with bonding to the hard tissue results in stress transfer and inward deformation of the cavity walls of the restored tooth[21]. When shrinkage stress overcomes the bond strength to the cavity walls, the marginal seal of adhesive composite restorations is lost, resulting in gap failures at the tooth-composite interface. Once the bond between restoration and tooth fails, microleakage of oral fluids, bacteria, molecules, and ions occurs at the tooth-composite interface[7,8,12,19] resulting in marginal leakage, postoperative sensitivity, marginal discoloration, recurrent caries and consequent pulp pathology[4,13,15,19].
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