Abstract
This study aimed to evaluate the effect of flask types, post-pressing times and base regions on the base adaptation of maxillary and mandibular complete dentures. Denture bases were waxed in stone casts and randomly divided into six groups (n=10), according to conventional and double flasks inclusion, and immediate and 6 hours post-pressing times. Denture bases were polymerized in water bath at 74oC for 9 hours. Stone cast-denture base sets were sectioned in three regions corresponding to: A- distal of canines, B- mesial of first molars, and C- posterior palatal seal (maxillary base) or tubercle region (mandibular base). Stone cast-denture base set adaptation was verified on reference points of maxillary and mandibular denture bases with a comparative linear microscope with 0.0005 mm accuracy. Obtained data were analyzed by the ANOVA and Tukey’s test (α = 0.05).For maxillary and mandibular denture bases at immediate polymerization, all regions showed lower misfit values for the traditional flask with statistical significance when compared to double flask. No statistically significant difference was shown after 6 hour post-pressing time. Except in the region A for the maxillary denture base in the traditional flask, other regions showed significantly different values when the immediate and 6 hour post-pressing times were compared. No statistical significance was observed for the mandibular denture base. Traditional flask and immediate post-pressing time promoted better adaptation than double flask for maxillary and mandibular denture bases. In 6-hour post-pressing time, similar base adaptation was shown for both traditional and double flasks for all regions.
Highlights
A previous study has shown that linear dimensional changes of acrylic resins are an important property for complete denture adaptation, in which the resin pressing procedure and polymerization cycle are factors that exert effects on the denture base distortion (Harman, 1949)
This study aimed to evaluate the effect of flask types, post-pressing times and base regions on the base adaptation of maxillary and mandibular complete dentures
Stone cast-denture base sets were sectioned in three regions corresponding to: A- distal of canines, B- mesial of first molars, and C- posterior palatal seal or tubercle region
Summary
A previous study has shown that linear dimensional changes of acrylic resins are an important property for complete denture adaptation, in which the resin pressing procedure and polymerization cycle are factors that exert effects on the denture base distortion (Harman, 1949). Some studies have proposed alternative techniques to conventional procedures of polymerization, such as microwave energy irradiation (Nishii, 1968), dry-heat (Gay & King, 1979), fast cycling in boiled water (Polyzois et al, 1987) and polymerization by visible light (Takamata & Setcos, 1989). Despite these techniques, the most efficient and accepted cycle for denture processing is the long cycle with hot water bath (Anusavice, 2003). The literature has shown satisfactory results when acrylic resin denture base is polymerized by either microwave irradiation (Wallace et al, 1991) or fast cycle in boiled water bath (Polyzois et al, 1987)
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