RESUMEN
The comparative stability of two removable die systems was evaluated. Under controlled conditions, ten casts, each with two removable dies, were constructed for each system for a total of 20 casts and 40 removable dies. Base-line pre- and postsectioning measurements to within 0.0001 inch in horizontal and vertical planes were recorded and differences calculated. Each die was removed and re-placed 30 times prior to any postsectioning measurement. The results indicated small inconsistent horizontal deviations and consistent vertical deviations for both systems. The Pindex system deviations were slightly less than those of the Di-Lok system, although t test values preclude any conclusion of significance. The results of this investigation indicate the need for dentists and dental laboratory technicians to exercise care in the utilization of any removable die system so as to obtain optimum accuracy and stability in the relationships of the components of that system.
Asunto(s)
Técnica de Colado Dental/instrumentación , Modelos DentalesRESUMEN
A thorough understanding of the basic principles of cavity preparation and knowledge of tooth morphology are necessary for the successful positioning of pin channels in the tooth. Sufficient dentin surrounding the channel is necessary for adequate strength, to avoid external fractures of tooth structure and to protect the pulp. Once the channel location is decided upon, it should be made parallel with the external surface of the tooth rather than its long axis. It is suggested that the operator use only one pin per missing cusp of the tooth and that where possible this pin be placed in the area of the line angles. Optimal length of the pin into the restorative material is 2 mm and in the dentin is 2 to 3 mm for those retained by dentinal elasticity and 3 to 4 mm for those retained by cement. The use of a rubber dam for isolation procedures is encouraged, as well as radiographs and diagnostic casts to aid in the successful placement of retentive pins.