Abstract:

Objective
To compare the flexural strength of the four kinds of room curing denture materials of polymethyl methacrylate(PMMA),and  observe the physical conformation section through confocal laser scanning microscope (CLSM) in order to find the relationship between the macro-bending force and the microstructure. Methods Four room curing PMMA materials  were produced by  Tokuyama(hard-liner type),Nisshin(fiber type),Heraeus(fiber type), and Shanghai dental (simple type). Each of the room curing PMMA was prepared by a group of 10 specimens. According to ISO1567,room temperature 20℃ and vendors powder liquid ratio with the stainless steel molds were performed to prepare samples,flexural strength was measured on the test machine. The cross-section was analyzed with CLSM. Results The  flexural strengths of four kinds of room curing PMMA  were (41.00±12.22),(87.80±14.82),(76.30±7.51), and (81.20±8.93) MPa,respectively;there wre significant differences in the flexural strengths between  Tokuyama and Nisshin,Heraeus(P<0.05), there was significant difference between Shanghai dental and Tokuyama  (P<0.05),but there was no significant difference  between Shanghai dental and Nisshin,Heraeus (P>0.05).In the cross-section image of Nisshin group the complete degree  and the number of micro-cracks  were significantly higher than others,there was no significant difference between Heraeus and Shanghai dental,Tokuyama was the lowest. Conclusion Tokuyama has  the lowest flexural strength,Nisshin maximum,Heraeus similarity with Shanghai dental. When the flexural  strength of the material is stronger,there are more micro-cracks  from the cross-section.

Key words: room curing;polymethyl methacrylate;flexural strength;confocal laser scanning microscope;microstructure