Effect of Cast Modification on Linear Dimensional Change of Acrylic Tooth Position Following Maxillary Complete Denture Processing.

PURPOSE: To investigate the effect of different cast modifications on the vertical and horizontal tooth position following maxillary complete denture processing. MATERIALS AND METHODS: A total of 60 maxillary master casts were prepared and arranged in six groups (n = 10). Variation in modifications between study groups 1 through 6 were as follows: no modification, butterfly post palatal seal preparation only, butterfly post palatal seal preparation with 10 mm wide/4 mm deep box, butterfly post palatal seal preparation with 10 mm wide/4 mm deep box and four round holes, butterfly post palatal seal preparation with 20 mm wide/4 mm deep box, butterfly post dam preparation with 20 mm wide/4 mm deep box and four round holes, respectively. The boxes in the respective groups were prepared on the mid-heel area of the cast. The first group was included in the study as control. The initial master cast was indexed to standardize the measurement technique on all specimens before duplication. Maxillary denture tooth set-up was completed and indexed using laboratory putty to ensure a similar set-up on all specimens. Vertical and horizontal tooth positions were measured for the maxillary left central incisor, right and left first molars in waxed complete dentures, and following processing. The measurements were done using a digital vernier caliper with manufacturing accuracy of up to 0.01 mm. The study data were entered in a Microsoft Excel Spreadsheet. Statistical analysis was done using a paired Student t-test, ANOVA, and Tukey post hoc test set at 5% level of significance. RESULTS: The paired t-test (within groups) showed significant change in all linear tooth positions for groups 1 and 2. Groups 3 through 6 had significant change in vertical dimension only. One-way ANOVA indicated that no significant difference was seen in the vertical tooth movements between the groups; however, statistically significant reduction was seen in the horizontal tooth movements at the maxillary left central incisor, right and left first molars for groups 3 through 6 when compared to others without significant difference between them. CONCLUSIONS: Within the limitations of the study, it was concluded that the movement of the teeth horizontally could be reduced with master cast modification (box alone or box and round holes) whereas the vertical movement of the teeth was not affected by the cast modifications made across all groups.