Tensile and transverse strength of novel copolymers for denture base

Objectives: Compare tensile and transverse strength of new copolymers for denture base. Materials and methods: The specimens were prepared from heat cured acrylic resin with three types of additives: Acryester B, Ethoxycarbonylethylene, and Propenoic acid at a percentage of 5% and 10%. The tensile and transverse strains were tested, recorded and compared. Results: The analysis of variance display statistically significant difference. The p-value was 0.001 for each of tensile and transverse strain tests. Conclusions: The tensile strength of the novel copolymers increased. The transverse strength of some of the novel copolymers increased.

Evaluation of the Transverse Strength of the Heat Cure PMMA Resin Reinforced with Various Concentrations of Two Different Nanoparticles: An In vitro Study

Purpose: The purpose of the study was to evaluate the effect of titanium dioxide and zirconia nanoparticles on transverse strength of heat cure PMMA resin routinely used for complete denture fabrication.Methods: One hundred samples of PMMA resin were made and divided into five groups (20 samples for each group). The test specimens were divided into five groups depending on the concentration of reinforcing nanoparticles as Group 1,2,3,4 and 5; Group 1: PMMA unreinforced (control group), Group 2: PMMA reinforced with 2.5% nanozirconia, Group 3: PMMA reinforced with 5% nanozirconia, Group 4: PMMA reinforced with 2.5% titanium dioxide nanoparticles, and Original ResearchArticle Group 5: PMMA reinforced with 5% titanium dioxide nanoparticles. Universal testing machine was used to conduct a three-point bending test and evaluate the transverse strength of samples. Comparison of mean transverse strength for various groups was carried out by employing one‑way analysis of variance and Bonferroni post hoc tests.Results:The highest and lowest mean transverse strength were observed in Group 3 and 1, respectively. Bonferroni post hoc test showed increase in transverse strength after reinforcement to be statistically significant between all the groups (P = .05) except between the samples of group G1 and G5 and G2 and G3.Conclusion: Addition of nanoparticles in all concentrations significantly increased transverse strength of heat cure PMMA resin as compared to control group. The best result was obtained after adding 5% of nanozirconia particles to the conventional heat polymerized acrylic resin

Evaluation and comparison of transverse and impact strength of different high strength denture base resins.

Aim: The present study was undertaken to evaluate and compare the impact strength and transverse strength of the high‑impact denture base materials. A conventional heat polymerized acrylic resin was used as a control. Materials and Methods: The entire experiment was divided into four main groups with twenty specimens each according to denture base material selected Trevalon, Trevalon Hi, DPI Tuff and Metrocryl Hi. These groups were further subgrouped into the two parameters selected, impact strength and flexural strength with ten specimens each. These specimens were then subjected to transverse bend tests with the help of Lloyds instrument using a three point bend principle. Impact tests were undertaken using an Izod–Charpy digital impact tester. Results: This study was analyzed with one‑way analysis of variance using Fisher f‑test and Bonferroni t‑test. There was a significant improvement in the impact strength of high‑impact denture base resins as compared to control (Trevalon). However, in terms of transverse bend tests, only DPI Tuff showed higher transverse strength in comparison to control. Trevalon Hi and Metrocryl Hi showed a decrease in transverse strength. Conclusions: Within the limits of this in vitro study, (1) There is a definite increase in impact strength due to the incorporation of butadiene styrene rubber in this high strength denture base materials as compared to Trevalon used as a control. (2) Further investigations are required to prevent the unduly decrease of transverse strength. (3) It was the limitation of the study that the exact composition of the high‑impact resins was not disclosed by the manufacturer that would have helped in better understanding of their behavior.

Evaluation and Comparison of the Transverse Strength of Two Heat Cure Denture Base Resins Repaired with Auto Polymerizing Resin by Wetting with Methyl Methacrylate (MMA) at Different Time Intervals - An In vitro Study.

Aims: Fracture of dentures is a common clinical finding in daily prosthodontic practice, resulting in great inconvenience to both the patient and the dentist. A satisfactory repair should be costeffective, simple to perform, and quick. This study evaluated and compared the transverse strength of two heat cure denture base resins repaired with auto polymerizing resin by wetting with methyl methacrylate (MMA) at different time intervals. Materials and Methods: Stellon and Trevalon denture base materials were used in the study. A total of 200 heat cure acrylic resin specimens (100 specimens each of Stellon and Trevalon acrylic material) with the dimensions of (65 mm x 10 mm x 3 mm) were prepared. The specimens were divided with 10 specimens for each of the test groups (n =10). The test groups were designated as Group A through J. Repair gap of 2 mm was prepared in the centre of the specimen. The repair surface of the specimens were wetted with MMA at different time intervals (1, 2, 3, 4, 5, 10, 15 and 30 minutes) and repaired by using auto polymerizing resin. The transverse strength of the repaired specimens was tested by a 3 point bending test. All data was statistically analyzed with one-way ANOVA, differences within the groups were analyzed by independent sample t -test. Results: The results showed that the significant difference between the specimens wetted with MMA at different time intervals. A gradual increase was shown in the mean transverse strength of repaired specimens wetted from 1 minute to 5 minutes in Stellon and from 1 minute to 10 minutes in Trevalon. Conclusion: Wetting the repair surfaces with MMA for a period of more than 5 minutes and 10 minutes in case of Stellon and Trevalon respectively increases the incidence of adhesive failure in the repaired specimens.

Mechanical properties of denture base resins: An evaluation.

Background: Acrylic resin dentures are susceptible to fracture after clinical use, which is a problem of concern in prosthodontics. Impact failure outside the mouth and flexure fatigue failure in the mouth are two most important causes of fracture of denture base. Aim: This study evaluated the transverse deflection and transverse strength of four commercial brands of heat cure acrylic resin (Stellon, Acrylin-H, Trevalon and Trevalon-HI). Materials and Methods: An experimental design was adapted. Twenty-four rectangular strip specimens, six for each group, were prepared. Strips were finished on the edges and equally from the both the molded surfaces to make strips of specific dimensions. The tests were conducted mainly in accordance with the American Dental Association Specification no. 12/ISO: 1567-1981 (ISO: 6887-1986) for denture base polymer. The transverse deflection and transverse strength were measured by Instron testing machine. Intergroup differences were assessed using student "t" test. Results: The heat cure denture base material D (Trevalon "HI") had the minimum mean value of transverse deflection under different loads. Trevalon "HI" also had minimum value of mean transverse strength among different brands of acrylic resins. There was no statistically significant variation between Stellon, Acrylin-H and Trevalon, but variation was significantly higher with D (Trevalon "HI") vs. Stellon, Acrylin-H and Trevalon. Conclusion: The heat cure denture base material D (Trevalon "HI") was the strongest and C (Trevalon) was the weakest among all materials used in this study. The study showed that the deflection of various denture base resins (A to D) increases proportionately with the increase in load.

Effects of various silane coupling agents on the strength and the surface roughness of glass fiber-added PMMA resin / 대한치과보철학회지

STATEMENTS OF PROBLEM: The fracture of acrylic resin dentures remains an unsolved problem. Therefore, many investigations have been performed and various approaches to strengthening acrylic resin, for example, the reinforcement of heat-cured acrylic resin using glass fibers, have been suggested over the years. Silane is important for bonding between glass fiber and resin. PURPOSE: The aim of the present study was to investigate the effect of various silane on the strength of PMMA resin and roughness of resin-glass fiber complex after abrasion test. MATERIAL AND METHODS: 3mm glass fiber (Chopped strand, Hankuk fiber Co., Milyang, Korea) was treated with 3 kinds of silane (MPS, EPS, APS) (Sila-ace, Chisso chemical, Tokyo, Japan) and mixed with PMMA resin(Vertex RS, Vertex Dental B.V., Zeist, Netherlands). Transverse strength and Young's modulus was measured using Instron (Instron model 4466, Instron, Massachusetts, USA). After abrasion test (The 858 Mini Bionix II Test System, MTS System Co., Minnesota, USA) surface roughness was evaluated using tester (Form Talysurf plus, Taylor Hopson Ltd., Leicester, England). Examination of scanning electron microscope was also performed RESULTS: Within this study, the following conclusions were drawn. 1. Surface treatment of glass fiber with MPS and APS increased transverse strength of PMMA resin complex, but surface treatment with EPS decreased transverse strength of PMMA resin complex (p0.05).

Strength of glass fiber reinforced PMMA resin and surface roughness change after abrasion test / 대한치과보철학회지

STATEMENT OF PROBLEMS: The fracture of acrylic resin dentures remains an unsolved problem. Therefore, many investigations have been performed and various approaches to strengthening acrylic resin, for example, the reinforcement of heat-cured acrylic resin using glass fibers, have been suggested over the years. But problems such as poor workability, rough surface, poor adhesion of glass fiber resin complex are not solved yet. PURPOSE: The aim of the present study was to investigate the effect of short glass fibers on the transverse strength of heat-polymerized denture base acrylic resin and roughness of resin complex after abrasion test. MATERIAL AND METHODS: To avoid fiber bunching and achieve even fiber distribution, glass fiber bundles were mixed with acrylic resin powder in conventional mixer with a non-cutting blade, to produce the glass fiber(10 micrometer diameter, 3 mm length, silane treated) resin composite. Glass fibers were incorporated at 0%, 3%, 6% and 9% by weight. Transverse strength were measured. After abrasion test, surface roughness was evaluated and scanning electron microscope view was taken for clinical application. RESULTS: 1. 6% and 9% incorporation of 3mm glass fibers in the acrylic resin enhanced the transverse strength of the test specimens(p0.05). 3. After abrasion test, incorporation of 0%, 3%, 6% glass fiber in the resin showed same surface roughness value statistically(p>0.05). 4. In SEM, surface roughness increased as the percentage of the fibers increased. 5. In the areas where glass fiber bunchings are formated, a remarkably high roughness was noticed. CONCLUSION: 6% and 9% addition of silane-treated short glass fibers into denture base acrylic resin increased transverse strength significantly. Before and after abrasion test, incorporation of 0%, 3%, 6% glass fiber in the resin showed same surface roughness value statistically.

Efeito de soluções desinfetantes sobre dureza, resistência à flexão e características superficiais de resinas acrílicas termopolimerizáveis / Effects of chemical disinfectants on flexural properties, hardness and surface characteristics of denture base acrylic resins

As próteses quando são enviadas do consultório odontológico para o laboratório de prótese podem estar contaminadas com microrganismos patogênicos. Dessa forma procedimentos efetivos para o controle da infecção cruzada devem ser adotados tanto no consultório quanto no laboratório de prótese. Tem sido recomendado que as próteses devem ser desinfetadas ao serem enviadas ao laboratório e ao retornarem para o consultório. Este procedimento proporciona proteção tanto aos técnicos de laboratório quanto aos pacientes contra microrganismos patogênicos que podem estar presentes sobre as próteses. Dessa forma, o objetivo desta pesquisa foi verificar a influência de soluções desinfetantes (hipoclorito de sódio a 1%, clorexidina a 4% e perborato de sódio) sobre as propriedades mecânicas (resistência à flexão e dureza) e características superficiais de duas resinas acrílicas (QC20 e Lucitone 550). As resinas foram polimerizadas de acordo com as instruções dos fabricantes, polidas e imersas em água a 37º C por 48 horas antes da desinfecção (Grupo I). O procedimento de desinfecção constou das seguintes etapas: (a) imersão em clorexidina a 4% por 1 minuto; (b) imersão em solução desinfetante (Amosan - Grupo II; clorexidina a 4% Grupo III; hipoclorito de sódio a 1% - Grupo IV) e, (c) imersão em água por 3 minutos......

Dental prostheses brought into a dental office for repair or adjustments are contamined with bacteria, viruses, and fungi. To prevent the transmission of disease, all dentists, in-office dental auxiliaries, and dental technicians should exercise effective infection control procedures. A number of authors have recommended that is, every dental prosthesis is cleaned and disinfected as it enters and then again as it leaves the laboratory. This provides protection to laboratory personnel against pathogens that might be present on dental prosthesis that come from patients. It also protects patients from possible cross-contamination from other prosthesis that are part of the laboratory workload. The purpose of this study was to evaluate the effect of disinfection immersion (1% sodium hypoclorite, 4% chlorhexidine and sodium perborate (Amosan)) on the mechanical properties (transverse strength and Vickers hardness) and surface characteristics of two resins polymerized according to the manufacturer's instructions (Lucitone 550 and QC 20). After polymerization, the specimens were polished, and then stored in water at 37º C for 48 hours prior disinfection (group I). Disinfection methods include (a) immersion in 4% chlorhexidine for 1 minute; (b) immersion in chemical disinfectants (Amosan - group II; 4% chlorhexidine - group III; or 1% sodium hypochlorite - group IV) and (c) immersion in water for three minutes..........................