ABSTRACT
The purpose of this study was to investigate the relationship between glazing treatment and flexural strength of dental lithium disilicate glass ceramics. Three commercial lithium disilicate glass ceramic blocks were cut to size and polished with abrasive papers and diamond pastes. The specimens were prepared in accordance to the manufacturer's instruction for the crystallization process and divided into three groups. The first group was over-glazed with glazing paste and liquid. The second group was self-glazed at a normal over-glazing temperature without glazing paste and liquid. The third group was an untreated control group. The three-point flexural test was carried out using the universal testing machine. The broken specimens were examined by SEM/EDS. The over-glazed group showed lowest flexural strength. There was no statistically significant difference between self-glazed group and untreated group with respect to flexural strength. The bubbles and cracks were found in the glaze layer of over-glazed group. As the tensile stress was concentrated at the bottom of glaze layer during the flexural test, it was evident that the bubbles played a role in initiation and propagation of cracks. A mixed layer formed between glaze layer and glass ceramic during the over-glazing process could have negative effects on the flexural strength of entire specimen.