Heat Cure Methyl Methacrylate Research Articles

Flexural strength of heat polymerized acrylic resin repaired with different reinforcing materials

Purpose: Heat cure methyl methacrylate has been the denture base material of choice for the fabrication of conventional complete dentures and transitional removable partial dentures. One of the factors that cause fracture is considered to be low resistance to impact, flexural or fatigue. However, dentures repaired with auto-polymerizing acrylic resin alone often experience a re-fracture at the repaired site. This study aimed to evaluate flexural strength of heat polymerized acrylic resin repaired with different reinforcing materials.
 Methods: 48 samples were prepared and divided into four groups. 12 samples were considered as controls, and 36 were divided into 3 experimental groups. The samples were sectioned into two halves from the middle, and were then repaired with rapid repair material, and reinforcing material. Each group was divided into 4 subgroups: unreinforced, reinforced with metal wire, metal mesh, and glass fiber. All specimens were subjected to a 3-point bending test, and the flexural strength was calculated. Results: all the reinforcement groups namely Stainless steel wire, metal mesh and glass fiber improves flexural strength of heat cured acrylic resin samples and glass fiber reinforced samples had the greatest flexural strength when compared with all other groups.

Evaluation of In Vitro Cytotoxicity of Heat-cure Denture Base Resin Processed with a Dual-reactive Cycloaliphatic Monomer

The aim of this study is to evaluate cytotoxicity of tricyclodecane dimethanol diacrylate (TCDDMDA) when added to conventional heat-cure methyl methacrylate (MMA) monomer at 10% and 20% (v/v) concentrations. Twenty seven disk-shaped processed specimens were divided into control group (n = 9; comprises specimens made without substituting TCDDMDA in MMA) and two experimental groups (n = 9 each; specimens prepared by substituting TCDDMDA in MMA at 10% and 20% (v/v) concentration). Eluates were prepared by placing three specimens of each group into 9 mL of culture medium and then incubated at 37ºC for 24 hours. Continuous cells lines of L929 mouse fibroblast cells were used and MTT assay was employed to assess cytotoxicity. One-way analysis of variance (ANOVA) with post hoc Tukey's honestly significant difference (HSD) test was used to compare the mean optical density (OD) values and cell viability among the groups. A statistically significant difference was obtained (p = 0.000) when the mean and standard deviation of OD and cell viability (%) of the groups were compared. Highest OD value and cell viability was obtained with E20 group followed by E10 group. Addition of TCDDMDA in MMA of heat-cure denture base resin has no cytotoxic effect on L929 mouse fibroblasts. Dual-reactive TCDDMDA is a crosslinking monomer which has no cytotoxic effects on mammalian cell cultures. Hence, incorporation of TCDDMDA to MMA can be extrapolated and projected for fabricating dentures without compromising biocompatibility. How to cite this article: Ranganthan A, Karthigeyan S, Murugesan SV, et al. Evaluation of In Vitro Cytotoxicity of Heat-cure Denture Base Resin Processed with a Dual-reactive Cycloaliphatic Monomer. J Contemp Dent Pract 2019;20(11):1279-1285.

Residents' journal review

Residents' journal review

Heat-Cured Methyl Methacrylate Induces Increased Expression of HSP70 and iNOS in the Liver

Introduction: Exposure to methyl methacrylate (MMA), which is a widely used monomer in dental and medical fields, has been shown to be associated with adverse health effects on liver. Aim: This study aims to evaluate the mechanism toxic effect of MMA on liver, via investigating alterations in the expression levels of inducible nitric oxide synthase (iNOS) and heat shock protein70 (HSP70) in the liver, subsequent to the oral administration of MMA in rats. Methods: 20 SpragueDawley female rats were randomly selected and divided into two groups: control group, and experimental group. The experimental group was orally administered 120 mg/kg of MMA daily 5 times per week for four weeks. Changes in the expression of HSP70 and iNOS in the liver tissue was investigated using Immunohistochemistry technique. Results: Exp group had statistcaly higher hepatic expression of iNOS (p > 0.01) in comparison to the control group, by approximately three folds. Similarly, rat hepatocytes in the experimental group showed statistically significant (p > 0.01) increase, by approximately 15 folds, in the expression of HSP70 compared to that in the control group. Conclusion: The presented data suggest that exposure to MMA might cause liver injury as indicated by the prominanat elevation of the oxidative stress biomarker iNOS and the biological stress biomarker HSP70.

The Effect of Fiber Reinforcement on the Dimensional Changes of Poly Methyl Methacrylate Resin after Processing and after Immersion in Water: An in vitro Study

To evaluate and compare the effect of fiber reinforcement on the dimensional changes of heat-cured poly (methyl methacrylate) resin after processing and immersion in water. Three different heat-cure resins were selected for the present study: (1) Nonreinforced heat-cure methyl methacrylate resin, (2) High Impact heat-cured methyl methacrylate resin and (3) Fiberglass reinforced methyl methacrylate resin. Ninety samples were prepared using three different resins and denture bases obtained for the same. The amount of space between the tissue surface and the cast in the anterior, middle and posterior regions is measured after processing and immersion in water for 17 days using a traveling microscope having a least count of 0.001 cm. Mean and standard deviation were calculated for the dimensional changes and were subjected to statistical analysis (Student t-test, unpaired). Among the three groups of resins, fiber reinforced heat-cured methyl methacrylate resin was found to be statistically highly significant in terms of dimensional changes when compared with the nonreinforced and high impact heat-cured resins. Dimensional changes were evident in all the planes in the three groups studied and were in the following decreasing order-fiberglass reinforced heat-cured poly (methyl methacrylate) resin, high impact heat-cured poly (methyl methacrylate) resin and nonreinforced heat-cured poly (methyl methacrylate) resin. The fibers are added in order to increase the strength of acrylic resin. Considering only the strength may in turn affect the dimensional accuracy of the acrylic resin resulting in loss of retention and stability, affecting the fit of the denture.

Clinical and experimental study of heart-cured methyl methacrylate for cranioplasty (author's transl)

We report our experience and technique of prefabrication method for cranioplasty, using heat-cured methyl methacrylate (MMA). Recently, an autopolymerizing MMA has been a very popular material for cranioplasty. But an autopolymerizing MMA is so irritable to vital tissue that subgaleal effusion has been frequently noted after cranioplasty. And for a large cranial defect, it is difficult to get a good cosmetic result from the one-stage autopolymerizing MMA method. So, we have used a heat-cured MMA as a material of cranioplasty, and a prosthesis was formed preoperatively using an impression technique. In this method, the subgaleal effusion was markedly decreased and excellent cosmetic result was obtained even to a large cranial defect in a shortened operative time. The histological reactions to the autopolymerizing MMA and the heat-cured MMA were evaluated experimentally embedding each piece of the two materials in the subcutaneous tissue of the rat. The inflammatory reactions including appearance of foreign body giant cells were far less observed in the subcutaneous tissue around the heatcured MMA. This experimental result emphasized the advantage of heat-cured MMA method over autopolymerizing MMA.

The current status of pour resins

A technique for using a pour or fluid autopolymerizing (cold-curing) resin in a modified duplicating ring with hydrocolloid as the investing medium for the fabrication of complete denture bases was described in 1961 by Mirza.l After constructing 33 clinical dentures of a heat-cured methyl methacrylate and 31 clinical dentures of a cold-cured acrylic resin, Mirza concluded that, “. . . the clinical fit of autopolymerized dentures was equally as good as that of heat-cured dentures.” In the intervening years, independent research by a number of investigators resulted in improvements in the formulation of pour resins and the techniques for their use in the fabrication of both complete and partial dentures bases.“? 3A variety of colors of the resins were introduced, and ultraviolet absorbers and stabilizers were added to the existing products. Flasks were designed specifically for the use with pour-type cold-curing resins and colloidal investing materials. As a result of this research and the advantages the pour resins possess over heat-cured resins, manufacturers of these materials have reported a constant increase in their production and sale to the profession.? Seven major American dental manufacturing companies offer pour resins to the profession (Table I). Each of the companies has also designed its own flask. Shepard3 reported on a two-year period of evaluation of pour resins at the United States Army Regional Dental Activity at Walter Reed Army Medical Center. After the construction of more than 14,000 dentures of all types, he concluded that the pour technique, “. . . resulted in a denture that not only fit the cast more accurately than did compression molded dentures, but had fewer processing changes in its occlusal relationships.” Civjan and his associates4 reported that, “. . . laboratory data indicates that satisfactory dentures could be processed by the ‘fluid’ resin method at a considerable saving of processing time.” Weaver and Ryge6 concluded that, “. . . when the procedures are performed

Internal Porosity in Heat-Cured Methyl Methacrylate Resin for Dental Use

Internal Porosity in Heat-Cured Methyl Methacrylate Resin for Dental Use

Potential oncogenic properties of high polymers in mice.

This experiment was designed to determine the oncogenic potential of a polymerized epoxy resin and an autopolymerizing methylmethacrylate. Two hundred, 6-week-old Harlan stock albino Swiss mice were used. One of the following 4 resins was subcutaneously implanted into the lateral abdominal wall of 50 animals: (1) epoxy resin (Epon 828 diethylenetriamine), (2) autopolymerizing methylmethacrylate (Caulk, NuWeld, Batch #8666), embedded 1 hour after processing, (3) heat-cured methylmethacrylate (Luxene), and (4) cellophane (5½ H. S. Visking sausage casing). The animals were observed daily until the incisions had healed, and then weekly for the presence of subcutaneous tumors. Under the conditions of this experiment no tumors were produced with any of the agents tested.

Some comparisons of self-curing and heat-curing denture resins

D URING the past year or more there has been a continued and growing interest in the self-curing resins for denture base applications. The general adoption of the heat-cured methyl methacrylate type of denture base resin by the profession and patient gives a standard by which comparisons in properties of other types of resins can be made. To this time, only limited reports of studies are available for making these comparisons, and further studies should contribute much to the understanding of these cold-cured materials. The cold-cured or self-cured type of resins lend themselves well to comparison with properties of the heat-cured type by giving consideration to the chemical nature of the two types of materials. It is now common knowledge that chemically the chief difference between the two is the method of initiation or activation of the polymerization process. One is accomplished by the presence of a small amount of an appropriate chemical, while th’e other is brought about by the application of heat to the plastic mass. Fundamentally the two types are therefore quite similar in basic composition except. for minute differences in essential ingredients. It is to be reasoned, therefore, that the self-cured resins for dentures may have physical and mechanical properties as good as, but generally no better than, the heat-cured resins. As is often true, however, with two substances that are very similar in nature, one may lend itself better to certain adaptations or techniques than another. This may be a most favorable feature of the self-curing resins for denture bases.