[SEM study of machinable vita cerec mark II porcelain surface morphology after HF acid etching].

After HF acid etching under 5 different HF concentrations and 6 exposing times, the surface morphology of machinable porcelain was examined by scanning electron microscope, and the porsosity percentage and ething depth were determined. The results showed that the etching depth increased with the rising of HF concentration and disposing time until 5%-7.5 min. The porosity percentage of ething surface was positively interrelated with HF concentration and disposing time. It was the first time to classify the etching patterns of machinable porcelain into four groups.