Effect of polymerization cycles on the linear dimensional change, hardness and impact strength of denture base acrylic resins.
OBJECTIVE
This study verified the effect of polymerizing cycles on the linear dimensional change, hardness and impact strength of denture acrylic resins.


METHODS
One hundred and twenty samples (N.=10) each for the Classico and Vipi acrylic resins were made according to the manufacturers' instructions. The polymerization cycles were: 1- water bath at 74 ºC for 9 hr; 2- water bath at 74ºC for 8 hr and temperature increased to 100 ºC for 1 hr; 3- water bath at 74 ºC for 2 hr and temperature increased to 100 ºC for 1 hr; and 4- water bath at 120ºC and 60 pounds pressure for 1 hr. Samples were deflasked after flask cooling and submitted to finishing. Linear distances between referential points in the samples were measured at deflasking and after water storage for 7 and 30 days with a comparator microscope with an accuracy of 0.0005 mm. Knoop hardness test was accomplished in a durometer with a load of 25 gf for 10 sec and an average of three indentations was considered for the sample hardness. Impact strength (kgf/cm²) was measured by the Charpy system with load of 40 kpcm. Data were submitted to ANOVA and Tukey's test (5%).


RESULTS
Dimensional changes in the A-B and A-C distances, hardness values and impact strength for Classico and Vipi resins were differently influenced by the polymerization cycles, when deflasking and water storage for 7 and 30 days were considered.


CONCLUSIONS
Linear dimensional change, hardness and impact strength of denture acrylic resins were differently affected by the polymerization cycles.
Department of Prosthodontics and Periodontics, Piracicaba Dental School, State University of Campinas, Brazil. rconsani@fop.unicamp.br
R L
RL
Xediek Consani
M
M
Lacerda Vieira
M
M
Ferraz Mesquita
M A
MA
Coelho Sinhoreti
R
R
Danil Guiraldo
M A
MA
Arruda Nóbilo
D000180:Acrylic Resins; D000704:Analysis of Variance; D003799:Dental Stress Analysis; D003819:Denture Bases; D006245:Hardness Tests; D008422:Materials Testing; D058105:Polymerization
D000180:Acrylic Resins