Investigation into the marginal integrity of ceramo-metal restorations related to different alloy and coping design
Date
1979
DOI
Authors
Strating, Herman
Version
OA Version
Citation
Abstract
Since conflicting evidence exists in the literature concerning tooth preparation, different ceramo-alloys and different coping designs, this investigation was undertaken to evaluate these parameters in different combinations with the ultimate objective of arriving at an optimum ceramo-metal restoration on a scientific basis. The term "optimum" refers to a restoration which satisfies both cosmetic and periodontal requirements.
A standard hollow ground preparation was selected as the basis to evaluate and compare the marginal integrity of different ceramo-metal restorations. The difference existed in terms of alloy and coping design as follows:- 3 Different alloys viz. predominantly precious, semiprecious and nonprecious were combined with 3 different metal coping designs viz. metal collar, collarless and collarless facial butted. 5 Test samples were fabricated for each alloy and coping design combination, i.e. a total of 45 ceramo-metal test samples. In addition 15 control samples were fabricated where the coping design was standard (metal collar coping without porcelain) and again 5 samples per alloy.
In the fabrication of the test samples provision was made through the investment to compensate for increased casting shrinkage of the nonĀ precious alloy, while no such modification was made for the control castings. The completed copings / crowns were cemented directly on their respective dies, sectioned longitudinally and then analysed microscopically at 50X magnification.
On the basis of the results the following conclusions were drawn concerning marginal integrity:- Firstly the collarless facial butted crown should be rejected outright. Secondly the collarless design produces acceptable marginal fit, but nevertheless the nature of the marginal area renders this restoration periodontally unacceptable. Thirdly the metal collar design produces excellent marginal fit which makes it periodontally acceptable, but at the same time this particular design has cosmetic limitations.
Considering the abovementioned statistically confirmed facts, the optimum ceramo-metal restoration suggested by the author at the present level of biomaterial development, is a nonprecious, inconspicuously narrow metal collar coping design.
During the course of this study valuable information was also compounded as far as technique and variables affecting casting accuracy are concerned. For instance, a formula for casting nonprecious alloys as accurately as precious alloys is suggested and statistically confirmed.
The reader is encouraged to study, accept, reject or dispute the findings, because this can only serve to further the interests of our profession, which lies in scientific research.
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Thesis (M.Sc.D.)--Boston University, Henry M. Goldman School of Graduate Dentistry, 1979 (Prosthodontics)
Bibliography: p. 94-100.
Thesis (M.Sc.D.)--Boston University, Henry M. Goldman School of Graduate Dentistry, 1979 (Prosthodontics)
Bibliography: p. 94-100.
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This work is protected by copyright. Downloading is restricted to the BU community. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.