Fazal Ghani, Rafique Moosa.
Effect of Curing Methods and Temperature on Porosity in Acrylic Resin Denture Bases.
J Pak Dent Assoc Jan ;21(3):127-35.

OBJECTIVE: To investigate the influence of the curing method and curing temperature as variables of porosity in poly-methyl-methacrylate (PMMA) denture bases. METHODOLOGY Two hundred standardized square-shaped acrylic specimens (2cm2) with thickness of 1 mm were fabricated by using the fabrication techniques of wax pattern, investing, de-waxing, packing and curing. Forty specimens of these (GroupA)were fabricated in self-curing resin.The remaining specimens in GroupB,C,D, and E with 40 specimens in each group were cured by using thermostatically and time controlled water-curing equipment. Specimens in Group B were cured by subjecting them to a curing cycle involving immersion in water at room temperature and raising the temperature to reach boiling and thenmaintaining it for 45 minutes. Specimens in Group C were cured with 70 C & 7 hours curing regimen, Specimens in Group D were processed by the 70 C and 9 hours cycle. Specimens in Group Ewere cured by immersing them in room temperature water and raising the temperature slowly to reach 100 Candmaintaining it for another one hour.After finishing and polishing the specimens, porosity was assessed using scanning electronmicroscopy.The data collected were analyzed using SPSS version 14.0. RESULTS: Specimens in all the four groups displayed varying porosity percentages with both the within and between group variations. The range of the mean percent porosity in the water-cured specimens was 2 to 7 as compared to specimens in Group A (self-curing resin specimens ) exhibiting significantly higher mean porosity percentage of 63.Themean porosity percentwas lowest (2%) in the specimens cured by the 70 Cand 9 hours cycle. CONCLUSIONS Use of lower curing temperature and prolonged curing time had a beneficial effect on reducing the occurrence of porosity in the acrylic denture bases.

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