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Evaluation of varying amounts of thermal cycling on bond strength and permanent deformation of two resilient denture liners.
Pinto, José Renato Ribeiro; Mesquita, Marcelo Ferraz; Nóbilo, Mauro Antônio de Arruda; Henriques, Guilherme Elias Pessanha.
Afiliação
  • Pinto JR; School of Dentistry, Paulista University, Sao Paulo, Brazil.
J Prosthet Dent ; 92(3): 288-93, 2004 Sep.
Article em En | MEDLINE | ID: mdl-15343166
STATEMENT OF PROBLEM: Two problems found in prostheses with resilient liners are bond failure to the acrylic resin base and increased permanent deformation due to material aging. PURPOSE: This in vitro study evaluated the effect of varying amounts of thermal cycling on bond strength and permanent deformation of 2 resilient denture liners bonded to an acrylic resin base. MATERIAL AND METHODS: Plasticized acrylic resin (PermaSoft) or silicone (Softliner) resilient lining materials were processed to a heat-polymerized acrylic resin (QC-20). One hundred rectangular specimens (10 x 10-mm 2 cross-sectional area) and 100 cylindrically-shaped specimens (12.7-mm diameter x 19.0-mm height) for each liner/resin combination were used for the tensile and deformation tests, respectively. Specimen shape and liner thickness were standardized. Specimens were divided into 9 test groups (n=10) and were thermal cycled for 200, 500, 1000, 1500, 2000, 2500, 3000, 3500, and 4000 cycles. Control specimens (n=10) were stored for 24 hours in water at 37 degrees C. Mean bond strength, expressed as stress at failure (MPa), was determined with a tensile test using a universal testing machine at a crosshead speed of 5 mm/min. Analysis of failure mode, expressed as a percent (%), was recorded as either cohesive, adhesive, or both, after observation. Permanent deformation, expressed as a percent (%), was determined using ADA specification no. 18. Data from both tests were examined with a 2-way analysis of variance and a Tukey test (alpha=.05). RESULTS: For the tensile test, Softliner specimens submitted to different thermal cycling regimens demonstrated no significantly different bond strength values from the control; however, there was a significant difference between the PermaSoft control group (0.47 +/- 0.09 MPa [mean +/- SD]) and the 500 cycle group (0.46 +/- 0.07 MPa) compared to the 4000 cycle group (0.70 +/- 0.20 MPa) ( P <.05). With regard to failure type, the Softliner groups presented adhesive failure (100%) regardless of specimen treatment. PermaSoft groups presented adhesive (53%), cohesive (12%), or a combined mode of failure (35%). For the deformation test, there was no significant difference among the Softliner specimens. However, a significant difference was observed between control and PermaSoft specimens after 1500 or more cycles (1.88% +/- 0.24%) ( P <.05). CONCLUSIONS: This in vitro study indicated that bond strength and permanent deformation of the 2 resilient denture liners tested varied according to their chemical composition.
Assuntos
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Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Resinas Acrílicas / Colagem Dentária / Reembasadores de Dentadura Limite: Humans Idioma: En Revista: J Prosthet Dent Ano de publicação: 2004 Tipo de documento: Article País de afiliação: Brasil País de publicação: Estados Unidos
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Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Resinas Acrílicas / Colagem Dentária / Reembasadores de Dentadura Limite: Humans Idioma: En Revista: J Prosthet Dent Ano de publicação: 2004 Tipo de documento: Article País de afiliação: Brasil País de publicação: Estados Unidos