PubMed · 394506
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V Vrbic. 1977. [Enamel etching before composite application].. https://pubmed.ncbi.nlm.nih.gov/394506/
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This study evaluated the effectiveness of air abrasion (sandblasting), hydrofluoric acid (HF) etching, and acidulated phosphate fluoride (APF) for composite repair. Five different composites (three hybrids, one small-particle, and one microfill) were used to test the effects of different compositions and particle sizes. A phosphonate resin bonding agent was used for all repair procedures. In general, air abrasion provided the strongest repairs, approximately 60% of cohesive strength. The effect of HF varied with different composites, either improving or reducing the repair strength. APF gave the lowest interfacial bond strengths for all composites except the microfill.
The influence of porcelain surface condition and the application of silane agents on the adhesion between resin and dental porcelain were investigated. The experimental variables included three porcelain surface preparations, as polished, etched with phosphoric acid, or etched with hydrofluoric acid and three kinds of commercially available silane coupling agents. The shear bond strength between the light-cured composite and the dental porcelain was measured after one-day immersion in 37 degrees C water. Samples without the silane agent application were also tested as controls. Without the silane agent, hydrofluoric acid-etched specimens had a higher bond strength than polished or phosphoric acid-etched specimens. The combination of hydrofluoric acid-etching and an application of Cosmotech Porcelain Primer increased the bond strengths more than that of phosphoric acid-etching. With the application of Laminabond Porcelain Primer or Optec Silane Coupling Agent, high bond strengths were obtained regardless of the porcelain surface condition. Therefore, it seems the chemical reactions between the porcelain surface and silane agents were responsible for the high shear bond strengths.
The load dependency of hardness measurements was investigated on sound and demineralized enamel samples. For all samples investigated, the Knoop hardness number (KHN) varied as a function of the applied load. Higher loads enhanced indenter penetration into the test surface. The variation in KHN values observed in demineralized enamel, both surface-softened and surface-etched, was explained by a decrease in porosity as a function of depth. The reading error for indentations made on surface enamel etched with 37% phosphoric acid gel for 30 s was found to be slightly elevated compared to indentations made on a polished sound enamel surface. It was concluded that the surface microhardness technique can be used for the longitudinal investigation of etched surface enamel.