Surface texture and some properties of acrylic resins submitted to chemical polishing K. O. BRAUN*, J. A. N. MELLO † , R. N. RACHED ‡ & A. A. DEL BEL CURY § *Removable Partial Prosthodontic, Santa Maria Dental School, Federal University of Santa Maria (UFSM), Santa Maria, Rio Grande do Sul, Brazil, † Clinical Dentistry, Amazon School of Health Sciences, University of Amazonas (UA), Manaus, Amazonas, Brazil, ‡ Dental Materials, School of Dentistry, Pontifical Catholic University of Parana´ (PUCPR), Curitiba, Parana´, Brazil and § Removable Partial Prosthodontic, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, Sa ˜o Paulo, Brazil SUMMARY The effects of chemical polishing on den- tal acrylic resin properties are not well clarified. This study evaluated the effect of chemical and mechan- ical polishing on the residual monomer release (RM), Knoop hardness (KH), transverse strength (TS) and surface texture (ST) of a heat- and self- cured acrylic resin. Four groups were formed: GI- self-cured resin ⁄ mechanical polishing; GII-self-cured resin ⁄ chemical polishing; GIII-heat-cured resin ⁄ me- chanical polishing; GIV-heat-cured resin ⁄ chemical polishing. Following the polishing procedures, spec- imens were stored in distilled water at 37 °C. The KH and RM measurements were taken after 1, 2, 8 and 32 days of storage, and TS after 2, 8 and 32 days. Surface texture was observed under SEM evalua- tion. Results were compared statistically at a con- fidence level of 95%. The following conclusions were drawn: (1) regardless of the acrylic resin and the period of analysis, chemical polishing increased RM levels, reduced KH, and did not affect TS signifi- cantly; (2) water storage increased the surface hard- ness of GII and GIV; (3) GII and GIV showed a smooth and wavy surface under SEM evaluation. KEYWORDS: chemical polishing, denture, acrylic resin, strength, hardness, monomer release, surface texture, microwave Introduction In an attempt to achieve smooth exposed surfaces that contribute to oral hygiene and low plaque retention, orthodontic and prosthodontic appliances made of acrylic resin must be finished and polished appropri- ately. Normally, polishing procedures for acrylic resin appliances are performed mechanically by using pol- ishing wheels, felt cones, and slurry of pumice and water (Craig, Powers & Wataha, 2000). Soft brushes with chalk powder can also be used (Ulusoy, Ulusoy & Aydin, 1986). Because all mechanical polishing phases should be done step by step without neglecting any step (Ulusoy et al., 1986), it is a time consuming procedure and difficult to carry out. In 1969, Gotusso described a polishing technique called Ôsuperficial chemical polishingÕ, which consists of immersing the denture in heated monomer for 1 min. As stated by the author, the technique has the advant- age of polishing both the intaglio surface and the festooned external surfaces of the denture. Few publications were found regarding the effect of chemical polishing on the properties of the acrylic resins. Araujo, Abreu and Magalha ˜es (1972) found a decrease on surface hardness and an increase on transverse deflection of samples submitted to chemical polishing. Other investigations (Stolf, Consani & Ruhnke, 1985; Mesquita et al., 1996b) showed higher impact strength values of acrylic resins submitted to chemical polishing, than those that were mechanically polished. Because of the increasing popularization of chemical polishing and the lack of studies concerning its side-effects on the acrylic resin properties, this study had the purpose to evaluate and compare the effect of Ó 2003 Blackwell Publishing Ltd 91 Journal of Oral Rehabilitation 2003 30; 91–98