Detection of microscopic cracks in dental ceramic materials by fluorescent penetrant method

Ceramic materials are used as implants and prostheses because of their excellent biocompatibility and in the dental field beyond that, because of esthetic advantages and the little plaque accumulation. A disadvantage is their sensitivity to microscopic cracks because of their brittleness. Strength-deteriorating microscopic cracks can be introduced into the ceramic surface by the manufacturing process. The objective of this study was to evaluate three methods on their efficiency to detect microscopic surface cracks of clinical relevance in dental ceramic materials. These methods were light-optical microscopy, fluorescent microscopy after penetration with a fluorescent liquid, and scanning electron microscopy (SEM). It was found that microscopic cracks of critical sizes can be detected using the fluorescent penetrant method, which was not to be proven by light-optical microscopy and even not by SEM. We conclude from our study that the fluorescent penetrant method could help to decrease clinical failures of dental ceramic components that are caused by surface microscopic cracks from the manufacturing process, if this method was routinely performed before the clinical use of the ceramic components.