PubMed · 802013
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1975. [Avoiding failures in casting].. https://pubmed.ncbi.nlm.nih.gov/802013/
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This article describes a procedure for making an indicator to be used in fitting a casting to a die. It also describes how to use the indicator in the laboratory. The materials for making the indicator are inexpensive, present no health hazard, and are readily available at any arts and crafts store.
The self-glazing technique provides an esthetic and hygienic surface for crowns and fixed partial dentures that use porcelain veneers. A study of the biaxial flexure strengths of polished vs. glazed specimens is needed to verify that current laboratory methods are appropriate for planned fatigue studies. Four groups of 50 porcelain disk specimens each were subjected to the following polishing and firing procedures: group one was fired, glazed-no hold, and polished; group two was fired, polished, and glazed-no hold; group three was fired, polished and glazed-1 min. hold; group four was fired, polished, and not glazed. The piston-on-three-ball method was used for testing biaxial flexure strengths. Significantly lower differences in biaxial flexure strengths were noted when group two values were compared with values from groups one, three and four. The results show that the Weibull distribution is an appropriate model for our studies. Differences in glaze thickness among the groups were noted in SEM examination; however, bulk (interior) microcrack density differences were absent. The specimens that were fired, polished to a 1 micron surface finish, and not glazed (group four) were significantly higher in flexure strength than groups one and three at the p less than 0.001 level. The hypothesis that glazing of porcelain surfaces improves the biaxial flexure strength of test specimens was rejected.
A new system has been developed for measuring the surface morphology of the occlusal material. The main characteristic of the system is utilizing a flat laser beam to produce high accuracy measuring and to enable measuring 200 points at the same time on a line of 30 mm in length. It takes 8 to 10 minutes to digitize the whole morphology of a dental cast. The system has a central processing unit that assembles a series of digitized points into a data file of the dental morphology. It is also able to recognize the graphical image of the numerically reconstructed morphology on the CRT. Application of this measuring system enables the approach to the qualitative and quantitative evaluation of the spatial relationship between the opposing teeth at near the occlusal contact.