Comparison of vertical changes and linear accuracy of complete dentures produced by conventional and injection molding techniques

In complete denture treatment, vertical changes and linear accuracy due to processing error are inevitable in conventional molding technique. The greater the errors, the more time will be consumed to correct the occlusal relationship by selective or corrective grinding. In case of severe vertical errors, the grinding process also requires grinding of the teeth beyond the cusps, thereby destructing anatomical features of the teeth. The purpose of this study was to compare the vertical changes and linear accuracy of complete dentures produced by conventional and injection molding techniques. Twenty two maxillary and mandibular complete edentulous patients at the Department of Prosthodontics, University of Dental Medicine, Mandalay were divided into two groups by blocked randomization methods. Dentures were produced by conventional molding technique for group A and by injection molding technique for group B. The linear dimensions and amount of incisal pin opening were measured with digital slide clipper (accuracy ± 0.03 mm). Data were analyzed by Mann-Whitney U test. There was statistically significant increase in vertical dimension of denture produced by conventional molding technique than injection molding technique (P<0.05) but there was no significant difference in linear accuracy. Within the limitation of this study, the injection molding technique produced more accurate denture especially in vertical dimension when PMMA was used. Further studies are needed to assess dimensional changes of denture in long term use and to evaluate the comfort levels and chewing efficiencies with dentures produced by these techniques.