Resin strengthening of dental ceramics—The impact of surface texture and silane

Objectives To examine the effect of porcelain surface texture achieved utilising three clinically relevant surface preparation methods prior to silane and unfilled resin application on the flexure strength of a low fusing feldspathic porcelain. Materials and methods Five hundred and forty dentine disc-shaped specimens (15.0 mm diameter and 0.9 mm thickness) were condensed, fired and allocated to 18 groups. Six groups were stored as-fired, six were alumina abraded and six were acid-etched. Samples were coated with silane, unfilled resin or both prior to bi-axial flexure testing. Group means were compared utilising a three factor design general linear model and post hoc all paired Tukey tests at P < 0.05. Weibull analysis was employed to examine the reliability of the strength data. Profilometry was used to characterise the surface texture of the specimen surfaces. Results Alumina abraded and acid-etched specimens had significantly lower flexure strengths than the as-fired specimens. A significant difference between the degree of strengthening observed following unfilled resin application on the three surface texture investigated was observed (P < 0.001). Silane application prior to resin coating resulted in no further significant increases in the mean bi-axial flexure strengths of the three surface textures. The as-fired surfaces had a low frequency of irregular amplitude defects, alumina abraded surfaces had an increased frequency of regular amplitude defects whilst the acid-etched surface consisted of an increased frequency of irregular amplitude defects. Conclusion The strengthening mechanism whilst dependent on surface texture was independent of defect severity. No significant strengthening occurred following silane priming suggesting that, for the unfilled resin utilised, the strengthening mechanism was not enhanced by improved resin-ceramic adhesion.