Microscopic Inspection of the Adhesive Interface of Composite Onlays after Cementation on Low Loading: An In Vitro Study

Abstract

Purpose: This study aimed to assess the layer thickness and microstructure of traditional resin-matrix cements and flowable resin-matrix composites at dentin and enamel to composite onlay interfaces after cementation on low loading magnitude. Materials and Methods: Twenty teeth were prepared and conditioned with an adhesive system for restoration with resin-matrix composite onlays manufactured by CAD-CAM. On cementation, tooth-to-onlay assemblies were distributed into four groups, including two traditional resin-matrix cements (groups M and B), one flowable resin-matrix composite (group G), and one thermally induced flowable composite (group V). After the cementation procedure, assemblies were cross-sectioned for inspection by optical microscopy at different magnification up to ×1000. Results: The layer thickness of resin-matrix cementation showed the highest mean values at around 405 µm for a traditional resin-matrix cement (group B). The thermally induced flowable resin-matrix composites showed the lowest layer thickness values. The resin-matrix layer thickness revealed statistical differences between traditional resin cement (groups M and B) and flowable resin-matrix composites (groups V and G) (p < 0.05). However, the groups of flowable resin-matrix composites did not reveal statistical differences (p < 0.05). The thickness of the adhesive system layer at around 7 µm and 12 µm was lower at the interfaces with flowable resin-matrix composites when compared to the adhesive layer at resin-matrix cements, which ranged from 12 µm up to 40 µm. Conclusions: The flowable resin-matrix composites showed adequate flowing even though the loading on cementation was performed at low magnitude. Nevertheless, significant variation in thickness of the cementation layer was noticed for flowable resin-matrix composites and traditional resin-matrix cements that can occur in chair-side procedures due to the clinical sensitivity and differences in rheological properties of the materials.

Surface modification of zirconia or lithium disilicate-reinforced glass ceramic by laser texturing to increase the adhesion of prosthetic surfaces to resin cements: an integrative review

“…In the same way, surfaces of lithium disilicate-reinforced glass ceramics can also be modified by acid etching with (5-10%) HF acid providing a standard rough surface for adhesion to adhesive systems and resin-matrix cements. Thus, the roughness of enamel, dentin, glass ceramics, and titanium surfaces can be increased by acid etching that increase the adhesion area for mechanical interlocking to adhesives and resin-matrix cements [1][2][3][4]. However, acid etching with HF or H 3 PO 4 acids cannot alter surfaces of polycrystalline ceramics such as zirconia considering a highly chemical stability of the ceramic [5,6].…”