Surface roughness of auto polymerized acrylic resin according to different manipulation and polishing methods: an in situ evaluation.
OBJECTIVE
To test the hypothesis that no differences exists in the in situ level of surface roughness of an auto polymerized acrylic resin irrespective of the method of manipulation and polishing.


METHODS
Forty volunteers received the test specimens. Surface roughness was evaluated using a rugosimeter. Samples of auto polymerized acrylic resin were submitted to two methods of manipulation--mass and addition--as well as to two types of polishing--mechanical and chemical. Four test groups were designated according to manipulation and polishing techniques: mass-mechanical, mass-chemical, addition-mechanical, and addition-chemical. Five measures of surface roughness were taken from each sample and average surface roughness (Ra) was determined before and 20 days after the samples were worn by the volunteers. The data obtained were analyzed by the Student's t-test for paired samples as well as by analysis of variance.


RESULTS
Significant differences in Ra were found between mechanical and chemical polishing. Surface roughness was not influenced by manipulation techniques. Mechanical polishing presented the lowest values of Ra. There was a significant increase in surface roughness after volunteers wore the specimens for 20 days.


CONCLUSIONS
The hypothesis is rejected. There were differences on the surface roughness according to the different methods of manipulation and polishing used, but high values of surface roughness were found for all groups. Mechanical polishing showed the lowest values of surface roughness and thus should be preferred.
Gonçalves
Tatiana Siqueira
TS
Department of Orthodontics, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Brazil. tatianasgoncalves@terra.com.br
Spohr
Ana Maria
AM
de Souza
Rodrigo Matos
RM
Macedo de Menezes
Luciane
L
D000180:Acrylic Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003775:Dental Polishing / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008422:Materials Testing; D020366:Methylmethacrylate / Q000737:chemistry; D008768:Methylmethacrylates / Q000737:chemistry; D009967:Orthodontic Appliances; D011108:Polymers / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors
D000180:Acrylic Resins; D003764:Dental Materials; D008768:Methylmethacrylates; D011108:Polymers; C069716:Jet, dental resin; D020366:Methylmethacrylate