Water sorption by maxillary acrylic resin denture base and consequent changes in vertical dimension.
ABSTRACT Many kinds of materials have been tried in the Laboratory and to some extent clinically prior to introduction of acrylic resin. With the introduction of acrylic resin as denture base material, continuous attempts have been made to evaluate its physical properties. To observe the changes in vertical measurements of acrylic resin dentures due to water sorption and to assess variations of vertical movements of individual teeth within dentures due to water sorption; present study was carried out on 25 maxillary acrylic dentures. From results, the maximum water sorption appears to take place within 24 hours and after 28 day of water sorption; there is no change in vertical dimension if the denture is placed for further more time. With the introduction of acrylic resin as denture base material continued attempts have been made to evaluate physical properties so as to determine its suitability as an ideal nonmetalic denture base materials. Several investigations have been carried out on physical properties of this material such as compressive strength, tensile strength, solubility and colour stability. These have proved their superiority over other nonmetalic denture base materials used so far. Also several studies have been carried out to assess dimensional changes that occur in acrylic resin during processing, but very few studies have been carried out about the water sorption changes in the acrylic resin and still few about the vertical dimensional changes in acrylic resin due to water sorption. While fabricating the denture base from the acrylic resin, it comes in contact with water during polishing as well as cleaning, consequently during the use of denture it is constantly wetted by oral fluids. It is the hypothesis that water sorption by denture base acrylic may effect the retention and stability of the denture. It has been shown that water molecules act according to the laws of diffusion. The diffusion presumably occurs between the macromolecules which are forced slightly apart. This separation renders the molecules mobile and the inherent stresses created during heat curing of the acrylic resin can be relieved with consequent intermolecular relaxation and possible changes in the shape of the denture. Exposure time also plays a significant role in water sorption. The present investigation was therefore, carried out by keeping the following objectives: (1) The primary objective was to observe the changes in vertical measurements of acrylic resin dentures due to water sorption. (2) To assess the variations of vertical movement of individual teeth within the dentures due to water sorption.
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ABSTRACT: Correct occlusal relationships are part of the successful prosthetic treatment of edentulous patients. Occlusal checking should be performed via a remount procedure because denture base materials and fabrication procedures cannot provide dimensionally accurate complete dentures. Occlusal errors caused by the adjustment of denture bases to the denture foundation after a certain period of wearing can also be corrected by means of remounting. The following remount procedures for complete dentures are described: fabrication of transfer casts, transfer of a maxillary denture with a facebow, centric relation record, and mounting of dentures with transfer casts in an articulator with a dental stone. Deflective occlusal contacts of denture teeth in centric occlusion can be eliminated by selective grinding and by tooth-guided excursive movements. In complete denture treatment, priority is given to anterior/canine-guided occlusion.The International journal of periodontics & restorative dentistry 05/2007; 27(2):181-92. · 1.08 Impact Factor
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ABSTRACT: The purpose of this study was to investigate the effect of water storage at 37 degrees C (1 week, 1 month and 3 months) on tooth displacement in maxillary complete dentures. Ten maxillary dentures were constructed with Clássico acrylic resin using the conventional method of packing in metallic flasks. Metallic reference pins were placed in the incisal border of the central incisors (I), labial cusp of the first premolars (PM), and mesiolabial cusp of the second molars (M). Twelve hours after final flask closure, the acrylic resin was cured in water at 74 degrees C for 9 h. The flasks were removed from the thermo-polymerizing unit after water-cooling and the dentures were deflasked, finished and stored in water at a temperature of 37 degrees C for 1 week, 1 month and 3 months. At deflasking and at the water storage intervals, the I-I (incisor to incisor), PM-PM (pre-molar to pre-molar), and M-M (molar to molar) transversal distances, and LI-LM (left incisor to left molar) and RI-RM (right incisor to right molar) anteroposterior distances were measured using an optical microscope with 0.0005 mm accuracy. Data were submitted to ANOVA and Tukey's test (5%). Comparing the evaluation periods for each individual transversal and anteroposterior reference point, no statistically significant differences were observed among deflasking and the water storage intervals for I-I, PM-PM, M-M and RI-RM distances (p>0.05). For LI-LM, however, deflasking values were statistically different from those of 1-week, 1-month and 3-month water storage intervals (p<0.05), which, in turn, did not differ statistically to each other (p>0.05). These results confirm the complexity of tooth displacement in complete dentures. From a clinical standpoint, the difference observed in LI-LM distance after water storage would not be detected by the patients during clinical use.Brazilian Dental Journal 01/2006; 17(1):53-7.
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ABSTRACT: The method of porosity analysis by water absorption has been carried out by the storage of the specimens in pure water, but it does not exclude the potential plasticising effect of the water generating unreal values of porosity. The present study evaluated the reliability of this method of porosity analysis in polymethylmethacrylate denture base resins by the determination of the most satisfactory solution for storage (S), where the plasticising effect was excluded. Two specimen shapes (rectangular and maxillary denture base) and two denture base resins, water bath-polymerised (Classico) and microwave-polymerised (Acron MC) were used. Saturated anhydrous calcium chloride solutions (25%, 50%, 75%) and distilled water were used for specimen storage. Sorption isotherms were used to determine S. Porosity factor (PF) and diffusion coefficient (D) were calculated within S and for the groups stored in distilled water. anova and Tukey tests were performed to identify significant differences in PF results and Kruskal-Wallis test and Dunn multiple comparison post hoc test, for D results (α=0.05). For Acron MC denture base shape, FP results were 0.24% (S 50%) and 1.37% (distilled water); for rectangular shape FP was 0.35% (S 75%) and 0.19% (distilled water). For Classico denture base shape, FP results were 0.54% (S 75%) and 1.21% (distilled water); for rectangular shape FP was 0.7% (S 50%) and 1.32% (distilled water). FP results were similar in S and distilled water only for Acron MC rectangular shape (p>0.05). D results in distilled water were statistically higher than S for all groups. The results of the study suggest that an adequate solution for storing specimens must be used to measure porosity by water absorption, based on excluding the plasticising effect.Gerodontology 12/2009; 28(2):127-33. · 1.83 Impact Factor