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Abstract
Statement of problem
A casting connection technique is widely used for repair, correction and addition to base metal framework. However, a casting connection technique may increase the risk of failure in clinical situations when high stresses exist.
Purpose
The purpose of this study was to investigate the mechanical retentive groove design comparatively to increase the joint strength by using the three-dimensional finite element analysis model of a 3-unit fixed partial denture.
Material and methods
Ten finite element models were constructed. (Model A: One retentive groove, Model B: Two retentive grooves, Model C: Three retentive grooves, Model D: Four retentive grooves, Model E: One horizontal groove and two vertical grooves, Model F: Two horizontal grooves and one vertical groove, Model G: One groove with the enlarged dimension, Model H: Two grooves with the enlarged dimension, Model I: One groove with the increased height, Model J: One groove with the increased width of base). The vertical force was applied to the mesial and the distal fossa to the casting connection of mandibular first molar.
Results
The main factors, affecting joint strength of casting connection were both the retention between the primary cast and the secondary cast and the thickness of the primary cast remaining after preparing retentive groove. The increase of retentive force, according to the numbers and the dimension of retentive groove had an effect on distributing stress. However, in some cases, the increase of retentive force resulted in the increase of stress by reducing thickness of the primary cast in the connection area.
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Fig. 5.
Experiment 3: Retentive grooves with the enlarged dimension in comparison with model A and B of experiment 1.
Fig. 6.
Experiment 4: Retentive grooves with the increased height (model I) or width of base (model J) in comparison with model G of experiment 3.
Fig. 8.
Distribution of von Mises stresses of the primary (left) and the secondary (right) cast of each model from experiment 1 to experiment 4.
Table I.
Experimental condition of the casting connection
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