Physical Properties of Heat Cure Denture Base Resin after Incorporation of Methacrylic Acid

Effects of adding functionalized graphene oxide nanosheets on physical, mechanical, and anti-biofilm properties of acrylic resin: In vitro- experimental study

Background

Polymethyl methacrylate resin is widely used in orthodontic treatments. Graphene oxide (GO) has reactive functional groups on its surface that facilitate binding to various materials such as polymers, biomolecules, DNA, and proteins. This study aimed to investigate the impact of adding functionalized GO nanosheets on the physical, mechanical, cytotoxicity, and anti-biofilm properties of acrylic resin.

Materials and Methods

In this experimental study, fifty samples (for each test) were divided into groups of 10, in the form of acrylic resin discs with concentrations of 0, 0.25, 0.5, 1, and 2 weight percentage (wt%) of functionalized GO nanosheets and also the control group. Samples were evaluated in terms of physical properties (surface hardness, surface roughness, compressive strength, fracture toughness, and flexural strength), anti-biofilm properties (On four groups of micro-organisms, including Streptococcus mutans, Streptococcus sanguis, Staphylococcus aureus, and Candida albicans), and cytotoxicity. Data were analyzed using SPSS software version 22, descriptive statistics, one-way analysis of variance test, and Tukey post hoc test. The significance level was considered P < 0.05.

Results

No significant difference was observed between the different groups with weight percentages of 0.25, 0.5, 1, and 2% nano GO (nGO) and the control group (without nGO) in terms of surface roughness and toughness. However, compressive strength, three-point flexural strength, and surface hardness showed significant differences between the groups. Furthermore, the degree of cytotoxicity increased by increasing the weight percentage of nano-GO.

Conclusion

The addition of functionalized nGO in appropriate concentrations to polymethyl methacrylate can improve the anti-bacterial and anti-fungal biofilm properties without changing or increasing their physical and mechanical properties.

Incorporation of Treated Woven Carbon Fiber to Methacrylate Resin for Heat-Cured Acrylic Denture Composite

This research has studied the addition effect of woven carbon fiber treated with NaOH and coated by β- TCP to the conventional polymethyl methacrylate (PMMA). Two stages are involved in the preparation of heat-cured acrylic denture composite. The first chemical treatment of woven carbon fiber (WCF) surface by different concentrations of NaOH (0.10, 0.15, and 0.20 M) and coating carbon fiber with β-TCP by various weight fractions (0.08, 0.10, and 0.12 wi) were carried out. The second stage includes the reinforcement of denture base material by treated and coated WCF. The functional groups of the WCF surface before and after alkali treatment were studied by FTIR. The morphology of the WCF surface before and after alkali treatment was observed by FESEM, the diameter of pores on the untreated and treated fibers, and the adhesion of β-TCP powder to the fiber was also observed. Mechanical tests include: impact strength (I.S.) and flexural strength (F.S) were calculated using a three-point bending test with a universal test machine and a Charpy impact test machine, respectively. From the result, reinforcing PMMA with treated and coated WCF improves the mechanical properties (impact and flexural strength).

Monomer Modifications of Denture Base Acrylic Resin: A Systematic Review and Meta-analysis

BACKGROUND

Methyl methacrylate monomer of denture base resins was modified with several monomers to achieve better physico-mechanical properties without compromising the biocompatibility. However, there are no consensuses on the best strategy to achieve best modified monomer.

PURPOSE

To identify and evaluate the differences in the properties between conventional and modified monomers and to verify the influence of several variables on the properties of denture base acrylic resin.

MATERIALS AND METHODS

This study was executed by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. In-vitro studies that investigated the properties of conventional and modified monomers were selected. Searches were carried out in the Ebscohost, PubMed, Semantic scholar and J-stage databases. The search commenced from the year 1995 and the last search was done till November 2018. A comparison was performed between modified and unmodified monomers. The analyses were carried out using fixed-effect models.

RESULTS

The meta-analysis results showed high heterogeneity in all aspects, and higher flexural strength for monomers modified with 20% methacrylic acid.

CONCLUSION

Although the articles included in this meta-analysis showed high heterogeneity and high risk of bias, the in-vitro literature seems to suggest that use of modified monomers could improve the properties of denture base resins. Other variants of monomer modifications and their tested parameters were discussed in this systematic review as well. Dimensional accuracy is an unexplored variable to be evaluated extensively in the future researches.