Comparison of changes in vertical dimension between compression and injection molded complete dentures

doi:10.1016/0022-3913(89)90599-4

The Journal of Prosthetic Dentistry

Volume 62, Issue 6, December 1989, Pages 716-718

https://doi.org/10.1016/0022-3913(89)90599-4 Get rights and content

Abstract

Complete dentures were made for 30 patients. Fifteen sets were processed by conventional compression molding and 15 sets were processed by using the SR-Ivocap injection system. Changes in vertical dimension between the waxed and processed dentures were measured at the incisal guide pin by using a dial indicator. The difference between the two methods was highly significant on the basis of t-statistics. Whereas the processing changes noted with the conventional pack-and-press method were similar to previous studies, the injection method produced little or no pin opening. The superiority of the injection method before decasting was indisputable, and the results suggest that the laboratory remount procedure may be unnecessary when this system is used.

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Cited by (46)

Influence of postpolymerization time and atmosphere on the mechanical properties, degree of conversion, and cytotoxicity of denture bases produced by digital light processing
2023, Journal of Prosthetic Dentistry
Studies on the effects of postprocessing conditions on the physical properties, degree of conversion (DC), and biocompatibility of denture bases produced by digital light processing are lacking.
The purpose of this in vitro study was to evaluate the effects of the atmosphere during postpolymerization and of postpolymerization time on the flexural strength, Vickers hardness, DC, cytotoxicity, and residual monomer content of denture bases.
Six different groups of bar- and disk-shaped specimens from the denture base resin were produced, considering 2 different atmospheres (air and nitrogen) and 3 different postpolymerization times (5, 10, and 20 minutes). To determine the physical properties, the flexural strength and Vickers hardness were measured. Fourier transform infrared spectrometry was used to calculate DC. Cytotoxicity was assessed from the effect on human gingival fibroblasts. The residual monomer content was determined by using high-performance liquid chromatography. Based on the normality test by the Shapiro-Wilk method, a nonparametric factorial analysis of variances was conducted (α=.05).
A significant interaction was detected between the atmosphere and postpolymerization time for hardness (P<.001) but no interaction for strength, DC, or cytotoxicity (P=.826, P=.786, and P=.563, respectively). Hardness was significantly affected by the postpolymerization time in the groups with the nitrogen atmosphere (P<.001). DC was significantly affected by the atmosphere (P=.012), whereas strength and cytotoxicity were not (P=.500 and P=.299, respectively). Cytotoxicity was significantly affected by the postpolymerization time (P<.001), but strength and DC were not (P=.482 and P=.167, respectively). Residual monomers were not detected after ≥10-minute postpolymerization time.
The atmosphere significantly affected hardness and DC, whereas the postpolymerization time significantly affected hardness, DC, cytotoxicity, and residual monomer content. Denture bases produced in a nitrogen atmosphere and with the 10-minute postpolymerization time showed sufficient hardness, DC, and no cytotoxicity.
Comparison of digital surface displacements of maxillary dentures based on noninvasive anatomic landmarks
2018, Journal of Prosthetic Dentistry
Artificial markers called fiducials are commonly used to orient digitized surfaces for analysis. However, when these markers are tangible and placed in the region of interest, they may alter surface topography and influence data analysis.
The purpose of this in vitro study was to apply a modified digital surface fitting method based on anatomic landmarks to evaluate denture accuracy and to use 2 different denture processing techniques to evaluate the method. The goal was to noninvasively measure and describe any surface differences in denture processing techniques at the intaglio and denture tooth levels.
Twenty standardized maxillary complete dentures were waxed on standardized edentulous casts and processed by using acrylic resin compression (COM, n=10) and injection molding (INJ, n=10) methods. Digital scans were recorded of the anatomic surface of the cast, the intaglio and cameo surfaces of the acrylic resin dentures, and the cameo surface of the wax dentures. Three anatomic fiducials were identified on denture intaglio and cast scans and 4 on the cameo surfaces of waxed and acrylic resin denture scans. These fiducials were then used to digitally align the anatomic with the processed intaglio surfaces and the waxed with the processed cameo surfaces. Surface displacements were compared among processed dentures expressed at specific points (9 tissue landmarks and 8 tooth landmarks). The accuracy of surface displacements was assessed by changes in the number and location of anatomic fiducials. The scanning precision and the intraobserver repeatability in the selection of dental landmarks were also determined. For each landmark, the spatial (x, y, and z) mean differences between the 2 processing techniques were calculated for the intaglio and the cameo surfaces and presented on each orthogonal plane. Statistical nonparametric comparison of these means was analyzed with the Mann-Whitney U test (α=.05). Benjamini-Hochberg corrections for multiple comparisons were used.
Changing the number and the location of anatomic landmarks had a small effect on the precision of the surface fitting. Repeated scans yielded high precision levels. In contrast, intraobserver repeatability had a larger error. In general, injection-molded dentures showed less displacement after polymerization than did the compression-molded ones. These differences were more substantial at the denture tooth level than on the intaglio surfaces.
Anatomic noninvasive fiducials chosen at distinct locations of maxillary edentulous areas seem to be reliable markers for the superposition of corresponding digital surface scans. Maxillary dentures processed with the injection molding technique have minimal deformation. Posterior denture teeth displace in 3 dimensions with the compression molding technique.
Influence of thickness increase of intraoral autopolymerizing hard denture base liners on the temperature rise during the polymerization process
2014, Journal of Prosthetic Dentistry
Increasing the thickness of intraoral autopolymerizing hard denture base liners may result in a temperature rise and a burning sensation for patients.
The purpose of the study was to determine whether increasing the thickness of hard autopolymerizing reline resin increases the temperature of the basal seat area of a denture during the polymerization process.
Four polyethyl methacrylate and 1 polymethyl methacrylate autopolymerizing reline resin products of 3 different thicknesses were tested. A cobalt-chromium edentulous maxillary cast was used to obtain 150 stone casts, 50 for each thickness of 1, 2, and 3 mm (n=10). Polystyrene record bases were filled with the autopolymerizing reline resin mixture and placed on the cobalt-chromium cast, which was mounted on a reline index, to serve as denture substitutes. Two thermal probes were used to monitor the temperature rise, which was recorded at 30-second intervals until no further increase was noted. Collected data were subjected to a 2-way ANOVA and the Tukey honestly significant difference test (α=.05).
The mean temperature increase for the chairside denture reline procedure ranged from 39.45°C for the 1-mm thickness to 46.10°C for the 3-mm thickness. The 2-way ANOVA found significant differences (P<.001) among the different reline resin materials and thicknesses tested. All materials produced an exothermic chemical reaction. An increase in thickness was always accompanied by an increased temperature. The Tukey honestly significant difference test found that the highest temperature increase for all 3 thicknesses occurred in the polymethyl methacrylate resin.
The polymethyl methacrylate autopolymerizing hard denture base liner produced a significantly higher (P<.001) exothermic reaction than the other materials included in this study. One of the polyethyl methacrylate resins presented a higher exothermic reaction than the polymethyl methacrylate product at a 3-mm thickness, but the difference was not statistically significant. The polymethyl methacrylate resin presented the highest mean time to reach the maximum temperature for all 3 thicknesses.
Three-dimensional processing deformation of three denture base materials
2013, Journal of Prosthetic Dentistry
Citation Excerpt :
The results showed that all 4 experimental groups demonstrated an overall tendency to expand rather than contract, which may initially appear to be in contrast to evidence available in the literature. However, existing evidence was based on linear measurement methods between selected points,1,6,8,12 vertical dimension (incisal pin opening) measurements,7,11 or measurements of the posterior palatal border adaptation,9 when contraction was defined as reduced linear distance between 2 points. Based on the widely accepted reasoning that an increase in posterior palatal border opening is attributable to denture base contraction, it was decided to define contraction in 3D terms as an increased distance between the denture base fit surface and the cast surface and expansion as a reduced distance.
Heat-polymerized polymethyl methacrylate denture bases deform during and after polymerization, and this deformation may affect the clinical performance of complete dentures.
The purpose of this study was to investigate the processing deformation of 3 denture base materials on a standardized anatomic model by using a contact scanner and surface matching software.
Maxillary reproductions of a definitive cast were digitized by using a contact scanner. The casts were allocated to 4 groups, depending on the denture base material: compression molded (heat polymerized, polymethyl methacrylate based); injection molded (heat polymerized, polymethyl methacrylate based); manually adapted and light-polymerized (urethane dimethacrylate based); and manually adapted, compression molded, and light-polymerized (urethane dimethacrylate-based). The intaglio surfaces of denture bases fabricated on each replicate cast also were digitized by using the contact scanner. Surface-matching software was used to measure dimensional changes between each cast and its corresponding denture base. The Kruskal-Wallis analysis of variance based on ranks was used to assess differences in contraction, expansion, and overall change among groups. The Mann-Whitney U test was performed to determine differences among individual groups. Statistical significance was inferred when P<.01 to compensate for multiple group comparisons.
Statistically significant differences in processing deformations were observed among polymethyl methacrylate-based resins and urethane dimethacrylate-based resin. No differences were observed between compression molding and injection molding or between manual adaptation alone and the combination of manual adaptation and compression molding.
Urethane dimethacrylate-based resin showed greater processing deformation compared with polymethyl methacrylate-based resins. Compression molding and injection molding techniques produced similar results for the polymethyl methacrylate-based resins. The methodology used showed patterns of deformation that were too complex to be accurately analyzed by linear measurements.
Linear and volumetric dimensional changes of injection-molded PMMA denture base resins
2013, Dental Materials
The aim of this study was to evaluate the linear and volumetric dimensional changes of six denture base resins processed by their corresponding injection-molding systems at 3 time intervals of water storage.
Two heat-curing (SR Ivocap Hi Impact and Lucitone 199) and four auto-curing (IvoBase Hybrid, IvoBase Hi Impact, PalaXpress, and Futura Gen) acrylic resins were used with their specific injection-molding technique to fabricate 6 specimens of each material. Linear and volumetric dimensional changes were determined by means of a digital caliper and an electronic hydrostatic balance, respectively, after water storage of 1, 30, or 90 days. Means and standard deviations of linear and volumetric dimensional changes were calculated in percentage (%). Statistical analysis was done using Student's and Welch's t tests with Bonferroni–Holm correction for multiple comparisons (α = 0.05).
Statistically significant differences in linear dimensional changes between resins were demonstrated at all three time intervals of water immersion (p ≤ 0.05), with exception of the following comparisons which showed no significant difference: IvoBase Hi Impact/SR Ivocap Hi Impact and PalaXpress/Lucitone 199 after 1 day, Futura Gen/PalaXpress and PalaXpress/Lucitone 199 after 30 days, and IvoBase Hybrid/IvoBase Hi Impact after 90 days. Also, statistically significant differences in volumetric dimensional changes between resins were found at all three time intervals of water immersion (p ≤ 0.05), with exception of the comparison between PalaXpress and Futura Gen.
Denture base resins (IvoBase Hybrid and IvoBase Hi Impact) processed by the new injection-molding system (IvoBase), revealed superior dimensional precision.
Influence of high expansion dental stone used as investing medium on the changes in occlusal vertical dimension of complete dentures
2013, Saudi Dental Journal
Citation Excerpt :
A comparison of the changes in the OVD is an important method for estimating new denture base materials and processing techniques (Barbosa et al., 2002). Several studies have reported that the incisal pin can rise from the incisal table after dentures are processed by using dental stone investing medium and the compression molding technique (Kharat and Fakiha, 1999; Nogueira et al., 1999; Dukes et al., 1983; Dukes et al., 1985; Strohaver, 1989; Nelson et al., 1991). However, studies by Mosharraf et al. (2008); Barbosa et al. (2002), Keenan et al. (2003), and Swords et al. (2000) reported an increase of the OVD of a single denture, rather than the overall pin opening on both the maxillary and mandibular complete dentures.
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.

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^☆: Presented in part before the Carl O. Boucher Prosthodontic Conference, Columbus, Ohio

^∗: Associate Professor, Department of Prosthodontics.

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Comparison of changes in vertical dimension between compression and injection molded complete dentures☆

Abstract

J Prosthet Dent

J Prosthet Dent

J Prosthet Dent

J Prosthet Dent

J Am Dent Assoc

Processing changes in complete dentures: posterior tooth contacts and pin opening

J Prosthet Dent