title: Surface roughness of auto polymerized acrylic resin according to different manipulation and polishing methods: an in situ evaluation.
abstract: 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.
authors.affiliation: Department of Orthodontics, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Brazil. tatianasgoncalves@terra.com.br
authors.forename: Tatiana Siqueira
authors.initials: TS
authors.lastname: Gonçalves
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Spohr
authors.forename: Rodrigo Matos
authors.initials: RM
authors.lastname: de Souza
authors.forename: Luciane
authors.initials: L
authors.lastname: Macedo de Menezes
mesh_terms: 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
chemical_list: D000180:Acrylic Resins; D003764:Dental Materials; D008768:Methylmethacrylates; D011108:Polymers; C069716:Jet, dental resin; D020366:Methylmethacrylate