title: Effect of processing variables (different compression packing processes and investment material types) and time on the dimensional accuracy of polymethyl methacrylate denture bases.
abstract: In this study we determined the effect of different compression packing processes, investment materials (a hemihydrate and dental stone) and time on the dimensional accuracy of polymethyl metacrylate denture bases. Square stainless steel plates (15 mm x 15 mm x 5 mm) were prepared to make an acrylic resin specimen. The linear dimensional changes of acrylic resin were determined by measuring the distances of fix points. Measurements were made at 24 hours, 48 hours, 12 days and 30 days after setting with a digital compass. Dimensional changes of test specimens that were obtained with three different flasks and two press techniques were compared by univariate analysis. Measurements of the linear dimensions of specimens cured by different compression packing techniques suggested that differences existed. The time interval differences were not significant. According to the results; flask and investment material types affect the dimensional accuracy of test specimens (p < 0.05). The least dimensional change observed in the specimens was obtained with Type 1 flask-dental stone-manual press combinations.
authors.affiliation: Prosthodontics Department, School of Dentistry, Ataturk University, Erzurum, Turkey.
authors.forename: Seyfettin
authors.initials: S
authors.lastname: Baydas
authors.forename: Funda
authors.initials: F
authors.lastname: Bayindir
authors.forename: M Samil
authors.initials: MS
authors.lastname: Akyil
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000704:Analysis of Variance; D002133:Calcium Sulfate / Q000737:chemistry; D003735:Dental Casting Technique / Q000295:instrumentation; D003764:Dental Materials / Q000737:chemistry; D003819:Denture Bases; D006801:Humans; D008422:Materials Testing; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D011312:Pressure; D013193:Stainless Steel / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; D003764:Dental Materials; D013193:Stainless Steel; D019904:Polymethyl Methacrylate; D002133:Calcium Sulfate