Effect of different acid treatments on a porcelain surface.

The objective of this study was to determine the effect of selected surface treatments on the surface texture of a feldspathic porcelain. The three different etchant treatments were, acidulated phosphate fluoride (APF) applied for 10 min and hydrofluoric acid (HF) applied for 1 and 4 min. After acid treatment, half of the specimens from each group were cleansed with water and others were subjected to ultrasonic cleaning and then dried. Half of the specimens cleansed with two different methods were treated with silane. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the effects of such treatments. Etching with APF displays shallow patterns. Etching for 1 min with HF displays deep channels, pores and precipitates on the surface and as the etching time increased these channels were replaced by larger channels. EDS analyses show that the crystalline precipitates on the etched surfaces, which were not readily soluble in water, were the reaction products of Na, K, Ca, Al, etc. HF displayed a more roughened surface than the APF gel. However, the precipitates remain on the surface after acid application, they can only be removed by ultrasonic cleaning and cannot be removed by rinsing.