Another excerpt from studies conducted by Dr. Yada Chaiyabutr at the Kois Center...
Q: When the ceramic onlay comes back from the lab, it is already acid-etched and I should silanate it before anything, right? After I try it in, do I need to re-etch and re-silanate?
A: The silane solution should be applied directly on a ceramic restoration for 60 seconds. Then let the ceramic surface dry prior to a try-in process. Studies confirmed that this step is important for acheiving a durable adhesion of the resin cement bonding to the ceramic. Silane, X-(CH2) Si-(OR), creates chemical bonds between organic surfaces (e.g. resin materials and polymers) and inorganic surfaces (e.g. silica-based ceramics). The silanol groups, on one end, react with silica oxide forming a siloxane network (-Si-O-Si-O-) while the monomeric groups, on the other end, react with the methacrylate groups of the resin material. If the ceramic surface is contaminated after the try-in process, retreat it first by cleaning with an appropriate amount of solvent (water or acetone) and then re-etching with phosphoric acid (30-40%) for 60 seconds. Rinse with water and re-apply the silane solution.
Q: Why isn't self-adhesive resin cement used for adhesively retained restorations? How strong is the bonding compared to traditional resin cement?
A: Adhesively retained restorations (e.g. onlays, inlays, and veneers) rely on the bonding interface between the tooth (mainly, enamel) and restorations. The chemical bonding of the self-adhesive resin cement and the enamel is insufficient due to an inadequate etching through the enamel smear layer. Therefore, traditional resin cement is more appropriate to use. Studies showed that the total acid-etching step created deeper micromechanical interlock between the resin cement and the enamel and that resulted in stronger bonding. To avoid unnecessary risks of failure, self-adhesive resin cement is recommended for cohesively retained restorations and traditional resin cement is recommended for adhesively retained restorations.
Q: When the ceramic onlay comes back from the lab, it is already acid-etched and I should silanate it before anything, right? After I try it in, do I need to re-etch and re-silanate?
A: The silane solution should be applied directly on a ceramic restoration for 60 seconds. Then let the ceramic surface dry prior to a try-in process. Studies confirmed that this step is important for acheiving a durable adhesion of the resin cement bonding to the ceramic. Silane, X-(CH2) Si-(OR), creates chemical bonds between organic surfaces (e.g. resin materials and polymers) and inorganic surfaces (e.g. silica-based ceramics). The silanol groups, on one end, react with silica oxide forming a siloxane network (-Si-O-Si-O-) while the monomeric groups, on the other end, react with the methacrylate groups of the resin material. If the ceramic surface is contaminated after the try-in process, retreat it first by cleaning with an appropriate amount of solvent (water or acetone) and then re-etching with phosphoric acid (30-40%) for 60 seconds. Rinse with water and re-apply the silane solution.
Q: Why isn't self-adhesive resin cement used for adhesively retained restorations? How strong is the bonding compared to traditional resin cement?
A: Adhesively retained restorations (e.g. onlays, inlays, and veneers) rely on the bonding interface between the tooth (mainly, enamel) and restorations. The chemical bonding of the self-adhesive resin cement and the enamel is insufficient due to an inadequate etching through the enamel smear layer. Therefore, traditional resin cement is more appropriate to use. Studies showed that the total acid-etching step created deeper micromechanical interlock between the resin cement and the enamel and that resulted in stronger bonding. To avoid unnecessary risks of failure, self-adhesive resin cement is recommended for cohesively retained restorations and traditional resin cement is recommended for adhesively retained restorations.
-Tony L.
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