Microdureza, porosidade e rugosidade em resina acrílica termopolimerizada por um novo equipamento experimental

RESUMO

Objetivo: avaliar a rugosidade, microdureza Knoop e porosidade de uma resina acrílica termopolimerizável convencional polimerizada por um equipamento experimental. Material e métodos: dois grupos de corpos-de- -provas foram confeccionados (n=14), totalizando 28 espécimes, a partir de três matrizes de 30 mm de diâmetro por 3 mm de espessura em aço inoxidável, que foram incluídas em mufl a metálica. A resina acrílica convencional (Artigos Odontológicos Clássico) foi manipulada conforme orientação do fabricante – três partes de polímero para uma parte de monômero – e inserida na mufl a, mantida na prensa hidráulica sob 1,25 t por 12 horas. Os corpos-de-prova do grupo-controle (C) passaram por polimerização em polimerizadora (Protécni Equipamentos) sob a temperatura de 74ºC durante oito horas, seguido por uma temperatura de 100ºC durante uma hora. Os corpos-de-prova do grupo-teste (T) foram submetidos ao ciclo na polimerizadora experimental (Speed, Fenix Indústria e Comércio) durante 20 minutos, com as resistências do equipamento permanecendo em 130ºC durante todo o ciclo. Após remoção dos corpos-de-prova das mufl as, foram executados acabamento e polimento na politriz (Aropol 2V, Arotec) em ambos os lados com lixas de granulações 320, 400, 600, 1.200 e 2.000 (Saint-Gobain do Brasil Prod.Ind.), e submetidos ao testes de microdureza Knoop (HVS 1000, PanTec), rugosidade (SurfTest SJ-210, Mitutoyo) e porosidade. Os dados foram submetidos ao teste t de Student para amostras independentes, adotando-se o nível de signifi cância de 5%. Resultados: não houve diferença estatisticamente signifi cativa na rugosidade de superfície (p=0,725) e na microdureza Knoop (p=0,204) entre os grupos, porém, em relação à porosidade, constatou-se um número de poros signifi cativamente menor no grupo-teste (p=0,013). Conclusão: o experimento produziu uma resina acrílica com menos porosidade, entretanto com semelhante microdureza e rugosidade.

Palavras-chave – Resinas acrílicas; Polimerização; Bases de dentadura.

ABSTRACT

Objective: to evaluate roughness, Knoop microhardness and porosity of a conventional thermopolymerizable acrylic resin polymerized by experimental equipment. Material and methods: two groups of specimens were prepared (n=14), totaling 28 specimens from three stainless steel matrices measuring 30 mm in diameter and 3 mm thick, which were included in a metal fl ask. The conventional acrylic resin (Artigos Odontológicas Clássico) was manipulated according to the manufacturer’s instructions, 3 parts of polymer to 1 part of monomer, and inserted into the fl ask and kept in the hydraulic press under 1.25 t for 12 hours. The specimens from the control group (C) was polymerized in an electric polymerizer by water bath technique (Protécni Equipamentos) at a temperature of 74ºC for 8 hours, followed by a temperature of 100ºC for 1 hour. The specimens from the test group (T) were cycled in an experimental polymerizer (Speed, Fenix Indústria e Comércio) for 20 minutes, with the equipment resistance remaining at 130ºC throughout the cycle. After removing the fl ask, fi nishing and polishing were carried out using a polishing machine (Aropol 2V, Arotec) on both sides with 320, 400, 600, 1.200 and 2.000 grit sandpaper (Saint-Gobain do Brasil Prod. Ind.) and submitted to Knoop microhardness tests (HVS 1000, PanTec), roughness (SurfTest SJ-210, Mitutoyo) and porosity. The data were subjected to Student’s t test for independent samples, adopting a signifi cance level of 5%. Results: there was no statistically signifi cant diff erence in surface roughness (p=0.725) and Knoop microhardness (p=0.204) between the groups, however, porosity, a signifi cantly lower number of pores was found in the test group (p=0.013). Conclusion: the experimental equipment produced an acrylic resin with less porosity, however with similar microhardness and roughness.

Key words – Acrylic resins; Polymerization; Denture bases.

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