Effect of double flasking and investing methods on artificial teeth movement in complete dentures processing

Abstract

Effect of double flasking and investing methods on artificial teeth movement in complete dentures processingPurpose: The aim of this study was to evaluate linear dimensional alterations of artificial teeth for complete dentures when using different investment and flasking techniques. Background: Dimensional changes in the vertical dimension may occur owing to changes in artificial teeth positioning caused by different investing and flasking techniques. Materials and methods: Thirty pairs of the complete dentures were manufactured and randomly divided into three groups (n = 10): (1) invested with type III stone in monomaxillary PVC flask; (2) invested with type III stone in bimaxillary PVC flask; and (3) invested with laboratory silicone in bimaxillary PVC flask. Dentures were polymerised by microwave, and 12 linear distances were measured before and after denture processing. Data were analysed by one-way ANOVA, considering manufacturing technique as the study factor. Tukey's HSD was used as post hoc ANOVA (p = 0.05). Results: Most of the linear distances were comparable for all groups. All transversal maxillary and mandibular distances were higher for group 1 compared with groups 2 and 3 (p < 0.05), except the distance 3-6 for mandibular arch, in which no difference was found between groups (p < 0.05). Both maxillary diagonal distances were higher in group 1 (p < 0.05), and no differences were found among all groups for mandibular measurements. Conclusions: Double flasking technique independent on the investment material is shown to be the most effective method to reduce changes in artificial teeth positioning.

The influence of double flask investing on tooth displacement in dentures processed by microwave irradiation

“…Based on the results of intergroup analysis, there was no significant difference for the mean value of the angles a, b, a¢ and b¢ among the groups I, II, III and IV, before and after denture processing. These results are in contrast to previous studies where dentures processed in the BMF exhibit a reduction in vertical dimensional changes 11 and linear movement of the artificial teeth 12 . We suppose that these differences are related to the methodology applied to measure tooth displacement in the present study, which was based on tooth inclination angles, instead of linear measurements.…”

“…The same behaviour was observed for a¢ ( Table 2) in groups I, III and IV; for b (Table 3) in groups III and IV; and for b¢ ( Table 4) in groups I, II and III. As the values of the angles for the BMF were more uniform, these results of the intragroup analysis suggest that the BMF may affect tooth position in a lower degree than the MMF as previously shown 11,12 .…”

“…The polyvinyl‐chloride BMF used in this study allows simultaneous polymerisation of maxillary and mandibular dentures with teeth in occlusion by microwave irradiation. This may result in minimising tooth displacement 12 , saving time, and improving harmony of occlusion and vertical dimension 10,11 . The advantage of microwave irradiation is that it reduces polymerisation time and dough‐forming time, provides more homogeneous dough, and results in improved adaptation of the denture base 16 .…”

“…Maxillary and mandibular dentures are polymerised at the same time with teeth in occlusion, which may result in minimising tooth displacement, saving time and improving harmony of the occlusal vertical dimension 9,10 . Previous investigations have shown that dentures processed in the BMF exhibit a reduction in vertical dimensional changes 11 and linear movement of the artificial teeth 12 when compared with those processed in monomaxillary flask (MMF). Laboratorial analysis revealed that the BMF does not promote changes in resin properties such as surface roughness, hardness, and superficial porosity 13 .…”

Comparative laboratory evaluation of dimensional accuracy for 3D-printed complete maxillary denture

“…Regarding the processing technique, the movement of the teeth and the opening of the incisal pin can occur with a subsequent increase in the vertical dimension of occlusion . 17 Various researches were conducted to recognize surpassing materials and processing techniques to minimize occlusion changes. Dental laboratories are progressively turned towards integrating digital formats and procedures, including 3D scanner, CAD, and various technologies for additive manufacture.…”