PubMed · 7037470
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F A Colaizzi, J W Farah. 1981. Simplified border molding using silicone material.. https://pubmed.ncbi.nlm.nih.gov/7037470/
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OBJECTIVES: This investigation sought to develop a mapping apparatus for use in the assessment of both tooth and restoration wear. METHODS: A computer controlled mapping device, capable of scanning a suitably prepared electroconductive tooth replica by means of an electrical feedback mechanism, was constructed and its accuracy assessed by measuring the thicknesses of four engineers' slip gauges 12 times each. The reproducibility of three potential methods of rendering a die stone replica electroconductive was also investigated. Finally, tooth replicas were surface profiled and compared empirically with the originals using a commercial surface mapping program. RESULTS: The overall mean accuracy of the mean thicknesses of the slip gauges was 4.4 (2.8) microns. Surface deposition of either nickel spray or gold leaf, upon a ready formed replica, did not give a reproducible thickness. Precoating silicone impressions with nickel spray prior to replica production overcame this problem. On an empirical basis the instrument yielded accurate digital terrain models of tooth replicas. CONCLUSIONS: A surface mapping device has been developed which is both accurate and reproducible. A satisfactory electroconductive surface may be produced upon a tooth replica by precoating a silicone impression with nickel spray before casting the replica. The technique should prove invaluable for monitoring both tooth and restoration wear but further work is necessary to examine how such an approach will perform clinically.
STATEMENT OF PROBLEM: Some studies have demonstrated that short-term immersion disinfection does not affect the accuracy of polyether or addition silicone materials. Impressions are often disinfected for longer than recommended time periods. PURPOSE: This study evaluated these materials after simulating overnight disinfection. MATERIAL AND METHODS: Impressions were made of a master model with Extrude Extra material with Extrude Wash addition silicone and Impregum F material in combination with Permadyne Garant polyether material. Nondisinfected impressions served as controls, whereas the disinfected samples were immersed for 18 hours in a full strength 2% acid glutaraldehyde solution. Anteroposterior and cross arch dimensions of the working cast and occlusogingival, mesiodistal, and buccolingual dimensions of working die were assessed. The data were analyzed with one-way analysis of variance at "alpha" = 0.05. RESULTS: No significant differences were observed for anteroposterior and cross arch dimension when compared with the master model. However, significant differences were found for occlusogingival dimension at 18 hours of disinfection for both materials. The addition silicone 18-hour disinfection group was significantly less accurate in the mesiodistal dimension. CONCLUSION: Accuracy of both impression materials was adversely affected with 18 hours of immersion disinfection. Long-term (18 hours) immersion disinfection will affect the fit of fixed partial prostheses.
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