Influence of microwave polymerization method and thickness on porosity of acrylic resin.
OBJECTIVE
This study evaluated the influence of polymerization cycle and thickness of maxillary complete denture bases on the porosity of acrylic resin.


METHODS
Two heat-activated denture base resins--one conventional (Clássico) and one designed for microwave polymerization (Onda-Cryl)--were used. Four groups were established, according to polymerization cycles: A (Onda-Cryl, short microwave cycle), B (Onda-Cryl, long microwave cycle), C (Onda-Cryl, manufacturing microwave cycle), and T (Clássico, water bath). Porosity was evaluated for different thicknesses (2.0, 3.5, and 5.0 mm; thicknesses I, II, and III, respectively) by measurement of the specimen volume before and after its immersion in water. The percent porosity data were submitted to Kruskal-Wallis for comparison among the groups.


RESULTS
The Kruskal-Wallis test detected that the combinations of the different cycles and thicknesses showed significant differences, and the mean ranks of percent porosity showed differences only in the thinnest (2.0 mm) microwave-polymerized specimens (A = 53.55, B = 40.80, and C = 90.70). Thickness did not affect the results for cycle T (I = 96.15, II = 70.20, and III = 82.70), because porosity values were similar in the three thicknesses.


CONCLUSIONS
Microwave polymerization cycles and the specimen thickness of acrylic resin influenced porosity. Porosity differences were not observed in the polymerized resin bases in the water bath cycle for any thickness.
Pero
Ana Carolina
AC
Graduate Student, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, BrazilAssistant Professor, Department of Dental Materials and Prosthodontics, Araçatuba Dental School, São Paulo State University, Araçatuba, São Paulo, BrazilAssociate Professor, Department of Chemistry, São Carlos Federal University, São Carlos, BrazilAssociate Professor, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, Brazil.
Barbosa
Débora Barros
DB
Graduate Student, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, BrazilAssistant Professor, Department of Dental Materials and Prosthodontics, Araçatuba Dental School, São Paulo State University, Araçatuba, São Paulo, BrazilAssociate Professor, Department of Chemistry, São Carlos Federal University, São Carlos, BrazilAssociate Professor, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, Brazil.
Marra
Juliê
J
Graduate Student, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, BrazilAssistant Professor, Department of Dental Materials and Prosthodontics, Araçatuba Dental School, São Paulo State University, Araçatuba, São Paulo, BrazilAssociate Professor, Department of Chemistry, São Carlos Federal University, São Carlos, BrazilAssociate Professor, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, Brazil.
Ruvolo-Filho
Adhemar Colla
AC
Graduate Student, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, BrazilAssistant Professor, Department of Dental Materials and Prosthodontics, Araçatuba Dental School, São Paulo State University, Araçatuba, São Paulo, BrazilAssociate Professor, Department of Chemistry, São Carlos Federal University, São Carlos, BrazilAssociate Professor, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, Brazil.
Compagnoni
Marco Antonio
MA
Graduate Student, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, BrazilAssistant Professor, Department of Dental Materials and Prosthodontics, Araçatuba Dental School, São Paulo State University, Araçatuba, São Paulo, BrazilAssociate Professor, Department of Chemistry, São Carlos Federal University, São Carlos, BrazilAssociate Professor, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, Brazil.
D000042:Absorption; D000180:Acrylic Resins / Q000737:chemistry* / Q000528:radiation effects; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D003819:Denture Bases; D003827:Denture, Complete, Upper; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D008872:Microwaves; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D019904:Polymethyl Methacrylate / Q000737:chemistry / Q000528:radiation effects; D016062:Porosity; D011312:Pressure; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
D000180:Acrylic Resins; D003764:Dental Materials; D011108:Polymers; D014867:Water; D019904:Polymethyl Methacrylate