ABSTRACT
As resinas acrílicas são amplamente utilizadas na odontologia, especialmente em ortodontia e prótese. Este artigo relata o caso de um paciente de 33 anos de idade, do gênero masculino que relatava desconforto e dores na região de pré-molar superior esquerdo após a colocação de um provisório, com presença de uma lesão eritomatosa. Após biópsia incisional constatouse a processo inflamatório crônico inespecífico. A causa apresentada para tal patologia foi o provisório confeccionado com resina acrílica autopolimerizável à base de metil-metacrilato. (AU)
Acrylic resins are widely used in dentistry, especially in orthodontics and prosthetics. Patients: this article reports the case of a leukodermic 33-year-old male who reported discomfort and pain due to an erythematous lesion in the upper first left premolar (24) after the placement of an acrylic resin temporary restoration. Discussion: The signs and symptoms presented by the patient and his report of visiting the rural countryside generated concern regarding the possible diagnosis, which led to a more invasive biopsy to differentiate allergic inflammation from a paracoccidioidomycosis. Biopsy revealed a chronic inflammatory process. Conclusion: the pathology was caused by contact with methyl methacrylate-based provisional acrylic resin. After cementation of the final crown, the inflammatory signs and symptoms disappeared .(AU)
Subject(s)
Humans , Male , Adult , Acrylic Resins , Hypersensitivity , MethylmethacrylateABSTRACT
The different denture base materials and their processing techniques are developing in the field of removable and fixed prosthodontics. The polymers, especially acrylic resins are entered in this field more than 70 years ago and it is most widely used and material of choice around 80% world wide. Initially acrylic resins were polymerized by heat, later they developed using chemical accelerators for polymerization and termed as selfcure resins. The use of microwave energy to polymerize acrylic denture base in a 400 watt microwave oven for 2.5 minutes was reported in 1968 and properties ware discussed. The present study is designed to compare the residual monomer content in 24,48,72,96 and 120 hours periods of time and water absorption after 10 days in acrylic resin samples processed with conventional heat cure polymerization method and microwave polymerization method.
ABSTRACT
Background : Microwave postpolymerization has been suggested as a method to improve the flexural strength of an autopolymerizing denture reline resin. However, the effect of microwave postpolymerization on the residual monomer content and its influence on flexural strength have not been investigated. Objectives : This study analyzed the effect of microwave postpolymerization on the residual monomer content and its influence on the flexural strength of an autopolymerizing reline resin (Denture Liner). Materials and Methods : A total of 70 specimens (64 Χ 10 Χ 3.3 mm) were polymerized according to the manufacturer's instructions and divided into 7 groups (n = 10). Control group specimens were not subjectedto any further processing. Before testing, the specimens were subjected to postpolymerization in a microwave oven using different power (550 and 650 W) and time (3, 4, and 5 min) settings. Two specimens of each group were then manually ground into fine powder and samples extracted from the specimens using reflux method. The samples were then subjected to gas chromatography for residual monomer determination in area%. Eight specimens were subjected to a three-point bending device with a span of 50 mm and crosshead speed of 5 mm/min, and the flexural strength was determined in MPa. Data analyses included Student's t-test and one-way analysis of variance. Results : For the Denture Liner reline resin, the residual monomer content decreased and the flexural strength increased significantly with the application of microwave irradiation using different time/power combinations. The specimens with the lowest residual monomer content were the similar specimens which presented with the highest flexural strength. Conclusion : Microwave postpolymerization irradiation can be an effective method for increasing the flexural strength of denture liner (at 650 W for 5 min) by reducing the residual monomer content by further polymerization at free radical sites.
Subject(s)
Acrylic Resins/chemistry , Acrylic Resins/radiation effects , Analysis of Variance , Dental Materials/chemistry , Dental Materials/radiation effects , Denture Liners , Denture Rebasing , Methacrylates/chemistry , Methacrylates/radiation effects , Microwaves , Pliability/radiation effects , Statistics, NonparametricABSTRACT
Este trabalho avaliou o desempenho de quatro ciclos de polimerização de resinas acrílicas ativadas termicamente utilizadas para a confecção de base para prótese total: ciclo I (65 oC por 30min; 50 oC por 23h30min e 100 oC por 1h); ciclo II (50 oC por 24h; 65 oC por 1h; 30min para elevar a 100 oC e 1h a 100 oC); ciclo III (72 oC por 9h); e ciclo IV (65 oC por 1h; 30min para elevar a 100oC e 1h a 100 oC). O desempenho dos ciclos foi avaliado pela quantidade de monômero residual superficial e presença de porosidade. O teste estatístico baseou-se na análise de variância (Anova) e no teste de Tukey a5 por cento de significância. Em relação ao monômero residual superficial, os resultados apontaram diferenças estatisticamente significativas entre o ciclo III e os demais ciclos. A presença de porosidade não foi verificada nos ciclos I e II, foi em grau mínimo no ciclo III e em quantidade apreciável no ciclo IV. Concluiu-se que o ciclo curto determinou a presença marcante de porosidades e que, para os ciclos longos, a elevação da temperatura ao final do ciclo foi importante para a diminuição do monômero residual
Subject(s)
Acrylic Resins , Dental Materials , Denture, Complete , PorosityABSTRACT
Purpose: To evaluate residual monomer release from resilient denture lining materials polymerized by different methods. Methods: Two materials were assessed: Ever-Soft polymerized by hot water bath or microwave energy, and Light Liner polymerized by chemical reaction and visible light (dual polymerization). Residual monomer release was measured in 12 specimens (40x10x0.3mm) made of each material and polymerization method. The specimens were stored in distilled water for 168 hours at 37ºC, and analyzed daily by ultraviolet spectrometry (Light Liner: 204nm, Ever-Soft: 206nm). Data were analyzed by one-way ANOVA and Bonferroni test (α=0.05). The residual monomer released as a function of time was determined by polynomial regression analysis. Results: Residual monomer amount released at 168 hours from specimens polymerized by hot water bath (0.27±0.01μg/cm²) was significantly greater (P < 0.05) than from those processed by microwave energy (0.25±0.02μg/cm²). Ever-Soft showed decrease in monomer release over time, tending to stabilize at 96 hours. Light Liner continued to release monomer over time. Conclusion: Ever-Soft may be polymerized by microwave energy. Residual monomer release values were low, and the monomer levels decreased over time.
Objetivo: Avaliar o monômero residual liberado de materiais resilientes para reembasamento polimerizados por diferentes métodos. Metodologia: Dois materiais foram testados: Ever-Soft polymerizado por banho quente de água ou por energia de microondas, e Light Liner polimerizado quimicamente e por luz visível (polimerização dual). O monômero residual liberado foi mensurado em 12 espécimes (40x10x0,3mm) fabricados com cada material e método de polimerização. Os espécimes foram armazenados em água destilada por 168 horas a 37ºC, e analisados diariamente por espectrometria ultravioleta (Light Liner: 204nm, Ever-Soft: 206nm). Os dados foram analisados por ANOVA de fator único e teste de Bonferroni (α=0,05). O monômero residual liberado em relação ao tempo foi determinado por análise de regressão polinomial. Resultados: O monômero residual liberado em 168 horas do teste (μg/cm²) em espécimes polimerizados por banho de água quente (0,27±0,01μg/cm²) foi significativamente maior (P < 0,05) que em espécimes processados por energia de microondas (0,25±0,02μg/cm²). Ever-Soft mostrou uma redução na liberação de monomer residual com o tempo, tendendo a se estabilizar em 96 horas. Light Liner continuou a liberar monômero com o tempo. Conclusão: Ever-Soft pode ser polimerizado por energia de microondas. Os valores de monômero residual liberado foram baixos, e os níveis de monômero diminuíram com o tempo.
Subject(s)
Microwaves , In Vitro Techniques , Denture Liners , Dental MaterialsABSTRACT
STATEMENT OF PROBLEM: The residual monomer of denture base materials causes hypersensitivity on oral mucosa and intereferes with the mechanical properties of the cured resin. The amount of residual monomer is influenced by materials, curing cycle, processing method, and etc. PURPOSE: The aim of this study was to investigate the residual methyl methacrylate(MMA) content of injection molded denture base polymer, and to compare this with the self-cured resin and the conventional compression molded heat-cured resin. MATERIALS AND METHODS: Disc shaped test specimens (50mm in diameter and 3mm thick) were prepared in a conventional flasking technique with gypsum molding. One autopolymerized denture base resins (Vertex SC. Dentimex. Netherlands) and two heat-cured denture base resins (Vertex RS. Dentimex. Netherlands, Ivocap. Ivoclar Vivadent, USA) were used. The three types of specimens were processed according to the manufacturer's instruction. After polymerization, all specimens were stored in the dark at room emperature for 7 days. There were 10 specimens in each of the test groups. 3-mm twist drills were used to obtain the resin samples and 650mg of the drilled sample were collected for each estimation. Gas chromatography (Agillent 6890 Plus Gas Chromatograph, Agillent Co, USA) was used to determine the residual MMA content of 10 test specimens of each three types of polymer. RESULTS: The residual monomer content of injection molded denture base resins was 1.057+/- 0.141%. The residual monomer content of injection molded denture base resins was higher than that of compression molded heat cured resin (0.867+/-0.169%). However, there was no statistical significant difference between two groups (p > 0.01). The level of residual monomer in self cured resin(3.675+/-0.791) was higher than those of injection molded and compression molded heat cured resins (p<0.01). CONCLUSION: With respect to ISO specification pass/fail test (2.2% mass fraction) of residual monomer, injection molding technique(1.057+/-0.141%) is a clinicaly useful and safe technique in terms of residual monomer.