ABSTRACT
Problem statement: Tooth movement has been shown to occur during and after the processing of complete dentures. An understanding of this phenomenon may permit one to construct functional complete dentures that require less occlusal adjustment in the articulator and in the patient's mouth
Purpose: The purpose of this study was to examine the effects of three different investing methods on tooth movement occurring during the processing of simulated maxillary complete dentures
Material and methods: Forty-five similar maxillary dentures were made using heat-polymerized acrylic resin, and assigned randomly to three experimental groups [n = 15 each] according to investing method: plaster-plaster-plaster [P-P-P], plaster-stone-stone [P-S-S], and plaster-mix [P-M]. Specimens in all experimental groups were compression molded with denture base resin. Transverse interincisor [I-I] and intermolar [M-M] distances, and anteroposterior incisor-molar [LI-LM and RI-RM] distances, were measured with digital calipers at the wax denture stage [pre-polymerization] and after denture decasting [post-polymerization]. Analysis of variance and Tukey's test were used to compare the results
Results: M-M, LI-LM, and RI-RM movement was significantly greater in the P-P-P group than in the P-S-S and P-M groups; no significant difference in I-I movement was observed among groups. Transverse movement along M-M and I-I was significantly greater than anteroposterior movement in the P-P-P group; no significant difference among measurements was observed in the other two groups
Conclusion: The study results indicate that the use of dental stone or a 50:50 mixture of plaster and stone for investing of dentures is an important factor in efforts to control the magnitude of tooth movement
Subject(s)
Tooth Movement Techniques , Dental Pulp Calcification , MaxillaABSTRACT
Despite advances in materials and techniques, complete dentures made of acrylic resin experience an increase in the occlusal vertical dimension [OVD] during processing. Many factors that affect the OVD of complete dentures are known. However, no study has examined the effect of using high-expansion dental stone [type V] as an investing material on the OVD. This study investigated the effects of using a high-expansion dental stone as an investing material on changes in the OVD of complete dentures. Twenty sets of simulated upper and lower dentures were processed by the compression molding technique. Specimens were equally divided into 2 groups. In the dental stone type III [DST III] group, the lower, middle, and upper parts of a flask were filled with DST III. In the dental stone type V [DST V] group, the procedure was the same as in the DST III group, except that the middle layer was made of high-expansion DST V. Changes in the OVD were measured before and after denture processing. Collected data were analyzed with t-test statistics. Differences were considered statistically significant at the 95% confidence level. Both groups showed a small increase in the OVD as a result of processing, but the OVD increase was significantly less in the DST V group compared to the DST III group. High-expansion DST V can be recommended as an investing material to reduce the increase in the OVD that may occur while processing complete dentures