Autopolymerizing Polymethyl Methacrylate Resin Research Articles

Konvansiyonel, Eksiltmeli ve Eklemeli İmalat Tekniklerinde Kullanılan Geçici Kron Materyallerinin Yüzey Pürüzlülüğüne Diş Fırçalama ve Yüzey İşlemlerinin Etkisi: İn Vitro Çalışma

Background: This study aimed to compare the effect of the surface treatment and toothbrushing abrasion on the surface roughness of interim crown material specimens manufactured using conventional, subtractive, and additive processing techniques.
 Material and methods: 80 disk-shaped specimens were prepared from 4 different interim crown materials; one auto-polymerized polymethyl methacrylate resin (PMMA);(IM) and one bis-acryl composite resin;(AC) for conventional technique, one computer-aided design/computer-aided manufacturing (CAD-CAM) PMMA block;(TC) for subtractive process, one 3-dimensionally (3D) printed resin;(CB) for additive process. Specimens of each interim crown material were divided into two subgroups according to applied surface treatments; conventional polishing or surface sealant agent coupling (n=10). The surface roughness values of specimens before (Ra0) and after 10,000 cycles of toothbrushing (Ra1) were measured with a profilometer. Data were statistically analyzed.
 Results: The polished groups of all interim crown materials showed significantly higher Ra0 values compared to the sealant groups before toothbrushing (p˂0.05). While the polished IM groups exhibited the highest Ra0 value (0.44±0.08), the sealed TC groups exhibited the lowest Ra0 value (0.23±0.06). The Ra values of all material groups increased after simulated 1-year toothbrushing. While the polished IM group exhibited the highest Ra1 value (0.45±0.14), the sealed CB group had the lowest Ra1 value (0.31±0.09).
 Conclusion: It was observed that toothbrushing caused an increase in the surface roughness of all interim materials. The application of a surface sealant agent to these materials is more effective than polishing to reduce surface roughness. Sealed 3D printed resin for additive process exhibited the lowest mean roughness value after toothbrushing.
 Keywords: Additive Manufactured, Interim Crown Material, Roughness, Subtractive Manufactured, Toothbrushing Abrasion

Effect of Plastic Impression-Transfer Copings on the Dimensional Accuracy of Implant Impressions

Purpose: The purpose of this in vitro study was to evaluate the effect of plastic impression transfer copings on the dimensional accuracy of close tray implant impressions. Methods: A master model was constructed using autopolymerizing acrylic resin. Five parallel holes were drilled for implant analogs. Custom impression trays were made with autopolymerizing polymethyl methacrylate resin. The study consisted of 2 groups (n=5): (group 1) Impression was obtained with using plastic impression transfer coping (group 2) Impression was obtained without using plastic impression transfer coping. Vinylpolysiloxane impression material was used for both groups. After the impression were obtained, casts were made by type IV dental stone. Casts were scanned with the lab-type scanner and transferred to the measurement program. Measurements were made from a specific reference corner for each analog to ensure standardization. Data were saved as millimeters and pairwise comparisons were made with Welch's t-test analysis. Results: The effect of plastic caps was evaluated by applying the t-test to each distance. For all distances, the distortion seen in the measurements taken without the cap is higher than the measurements taken with the cap, but no significant differences were found (p>0.05). Conclusions: In the anterior-posterior distances, the distortions were found compression type, in the right-left distances the distortions were found as expansion-type. There is a dimensional change in the measurements taken without a cap, but no clinically significant differences were found.

Effect of treated zirconium dioxide nanoparticles on the flexural properties of autopolymerized resin for interim fixed restorations: An in vitro study

Statement of problemFractures of interim fixed restorations are a common complication. The autopolymerized polymethyl methacrylate resin materials used for interim fixed restorations have limited mechanical properties, but whether adding treated zirconium dioxide nanoparticles improves mechanical properties is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of treated zirconium dioxide nanoparticles on the flexural strength and elastic modulus of autopolymerized polymethyl methacrylate resin. Material and methodsA split-metal mold (60×10×3.3 mm) was used to fabricate 40 autopolymerized acrylic resin specimens. The specimens were divided into 4 groups (n=10) according to zirconium dioxide nanoparticle concentration: control (unmodified resin) and zirconium dioxide nanoparticle contents of 1, 2.5, and 5 wt%. The specimens were mixed and polymerized according to the manufacturer’s instructions and stored in distilled water for 48 ±2 hours at 37 °C. The flexural strength and elastic modulus were evaluated based on the 3-point bend test where data were analyzed by using 1-way analysis of variance and Tukey post hoc tests (α=.05). ResultsThe flexural strength of the 1-wt% zirconium dioxide nanoparticle specimens was significantly higher than that of the control group (P<.001) but did not significantly increase further with the higher nanoparticle content (P>.05). Elastic modulus significantly decreased with 2.5-wt% zirconium dioxide nanoparticles (P=.019), while no significant changes were found with other test groups (P>.05). ConclusionsThe addition of treated zirconium dioxide nanoparticles at low concentrations increased the flexural strength of autopolymerized polymethyl methacrylate resins used in fixed interim restorations.

Suppressive Effect of Auto-Polymerized Surgical Obturator Resin Incorporated with Vanillin on Microbial Biofilm

Surgical obturators are important oral prostheses given to patients after surgical treatment to minimize scar contracture and esthetic disfigurement that may affect patients’ functional appearance and psychological health. Poly-methyl methacrylate (PMMA) resin has been the material generally used for fabrication of surgical obturator. However, wearing of this resin appliance can raise a condition for microbial biofilm accumulation and infection of the patients due to the rough surfaces and internal porosities of the resin. Vanillin-incorporated heat-cured and auto-polymerized PMMA resin have been developed and demonstrated to have antimicrobial activity against several types of microorganisms. This study aimed to examine antimicrobial properties of vanillin-incorporated auto-polymerized surgical obturator resin on the biofilm formation of Streptococcus mutans and Candida glabrata. The auto-polymerized PMMA resin samples (Orthocryl® EQ, Germany) were prepared with vanillin incorporation (0.1% and 0.5% vanillin). All samples were coated with sterile saliva and incubated at 37 °C for 60 min. The suspensions of S. mutans ATCC 25715 and C. glabrata ATCC 15126 (107 colony forming unit/mL) were prepared using McFarland standard No.1. Microbial biofilm formation was done in 96-well plate at 37°C for 24 h. The total vital biofilm formation was evaluated by Cell Counting Kit WST-8 (Dojindo Molecular Technologies, USA) at 450 nm. All tests were done in triplicate on three separate circumstances. One-way ANOVA and Tukey’s test were applied for the statistical analysis. A significant decrease of S. mutans biofilm mass was noticed in 0.5% vanillin incorporated resin group compared with a control, resin without vanillin. The percentage of biofilm reduction was 40.8%. No different effect was observed in 0.1% vanillin group. In the case of C. glabrata, no significant biofilm reduction was examined among all groups. In conclusion, the adding of 0.5% vanillin to surgical obturator resin could significantly inhibit biofilm formation of S. mutans, however, the effect was not demonstrated on 0.1% vanillin. C. glabrata was observed to be resistant to vanillin. Using PMMA resin incorporated with 0.5% vanillin, an obturator with antimicrobial property can be applied to prevent dental caries and other systemic diseases in patients after surgical treatment.

In vitro investigation of the impact of remaining tooth structure on the tensile failure loads of overdenture copings.

BackgroundThe purpose of this in vitro study was to evaluate the impact of the remaining tooth structure on the retention of overdenture cast metal copings.Material and MethodsA freshly extracted intact mandibular human canine (length 25 mm) was selected and endodontically treated. An incisal reduction of 4 mm with no ferrule preparation was performed and a post space of 12 mm was created. By using polyvinyl siloxane duplication material and autopolymerizing polymethylmethacrylate resin, ten resin teeth analogs (control group) were obtained. A second set of ten resin teeth analogs (group 1) was created by preparing on the original natural tooth a 360o ferrule design of 1 mm in height and by using the same procedural technique. The canine was further reduced by an additional 1 mm, resulting in a ferrule of 2 mm in height, measured from the initial incisal reduction, thus a third set of ten resin teeth analogs (group 2) was created. For every tooth analog in all groups a dome-shaped metal coping was cast and luted with a glass ionomer cement. All specimens were subjected to tensile load testing until decementation occurred.ResultsThe specimens in the control group exhibited a mean failure load of 87.21 ± 18.26 N, while the 1 mm ferrule group recorded a higher mean failure load of 125.43 ± 8.79 N and the 2 mm ferrule group recorded the highest mean failure load of 146.12 ± 23.38 N. One-way ANOVA revealed significant differences (F= 28.04, p<0.001) in the tensile failure loads between all of the groups being tested.ConclusionsThe metal copings with a 2 mm ferrule design exhibited the highest retention values, followed by the 1 mm ferrule and the no ferrule design, with the differences among them being statistically significant. Key words:Ferrule effect, In vitro study, Metal copings, Overdenture, Tensile stress.

A comparative study to check fracture strength of provisional fixed partial dentures made of autopolymerizing polymethylmethacrylate resin reinforced with different materials: An in vitro study.

Aim:The purpose of the study was to evaluate the fracture strength of provisional fixed partial dentures made of autopolymerizing polymethylmethacrylate (PMMA) resin using different types of reinforcement materials to determine the best among them.Materials and Methods:Fifty samples were made (10 samples for each group) with autopolymerizing PMMA resin using reinforcement materials (stainless steel wire: looped and unlooped and glass fiber: loose and unidirectional) as 3-unit posterior bridge. The test specimens were divided into five groups depending on the reinforcing material as Group I, II, III, IV, and V; Group I: PMMA unreinforced (control group), Group II: PMMA reinforced with stainless steel wire (straight ends), Group III: PMMA reinforced with stainless steel wire (looped ends), Group IV: PMMA reinforced with unidirectional glass fibers, and Group V: PMMA reinforced with randomly distributed glass fibers. Universal testing machine was used to evaluate and compare the fracture strength of samples. Comparison of mean ultimate force and ultimate stress was done employing one-way analysis of variance and Tukey's post hoc tests.Results:The highest and lowest mean ultimate force and mean ultimate stress were of Group IV and I, respectively. Tukey's post hoc honestly significant difference multiple comparison for mean ultimate force and stress shows the increase in strength to be statistically significant (P < 0.05) except for the samples reinforced with randomly distributed glass fibers (P > 0.05).Conclusion:Unidirectional glass fibers showed the maximum strength, which was comparable to mean values of both stainless steel wire groups. Low cost and easy technique of using stainless steel wire make it the material of choice over the unidirectional glass fiber for reinforcement in nonesthetic areas where high strength is required.

Modified Technique for Making Auto-polymerized Polymethylmethacrylate Resin Custom Tray.

Custom made tray for dental impression is designed to provide a uniform space for the impression material and thereby improve the accuracy of the resultant working cast. Auto-polymerized acrylic resins have been the most commonly used material for the fabrication of these trays. The custom tray produces more accurate and reliable results for inter-abutment distance at the occlusal and gingival level than stock trays. This article describes a modified technique for fabrication of auto-polymerized Polymethylmethacrylate (PMMA) resin trays.

The Effects of Custom Tray Material on the Accuracy of Master Casts

In addition to the impression material, the type of impression tray influences the accurate dimensional transfer of the size and position of the teeth to the master cast. The aim of this study was to determine the accuracy of master casts produced from an alginate impression material using a visible-light-curing resin and autopolymerizing polymethyl methacrylate resin custom tray materials. Two types of custom trays were fabricated from a stainless steel master model with three index studs. Twenty-two irreversible hydrocolloid impressions were made of the master model and then poured with a Type III dental stone. The distances between the reproduced index studs were measured to +/- 0.01 mm with a digital caliper. A one-way analysis of variance (ANOVA) and T-test were used for data analysis. There were no significant differences between the two tray materials for any of the three distances. There were no statistical differences between the master model and the casts made from the two tray materials in the length dimension, but there were significant differences in the vertical dimension. In terms of the width dimension there was a significant difference only between the cold curing group and the master model. Within the limitations of this study, the dimensions of stone casts poured from an impression made using a light-cured tray did not differ significantly from those created from impressions made using autopolymerizing acrylic trays. However, working dies from the light-curing tray impressions were more accurate buccolingually than those from the autopolymerizing acrylic trays. The accuracy of master cast reproduction using visible-light-curing resin or an autopolymerizing polymethyl methacrylate resin custom tray material is acceptable. Although autopolymerizing resin materials require less equipment and are relatively more inexpensive, light-cure tray materials may be the material of choice for custom tray fabrication due to greater accuracy in the buccolingual dimension.

Unpolymerized surface layer of autopolymerizing polymethyl methacrylate resin.

The aim of this study was to determine the thickness of the unpolymerized surface layer of autopolymerizing polymethyl methacrylate (PMMA) resin. Powder: liquid (P/L) ratios of 10:4-10 by weight of the PMMA were tested, and the PMMA resin was polymerized at 55 degrees C either in water or in air under an air pressure of 100 kPa or 300 kPa. Five samples were polymerized for each of the test groups. The thickness of the unpolymerized surface layer, i.e. inhibition depth of PMMA, was measured by a light microscopic technique with polarized light. The inhibition depth of the samples polymerized in air under 100 kPa pressure varied from 39 to 174 microns, and the samples polymerized under 300 kPa pressure had an inhibition depth of 91-391 microns. The P/L ratio and the polymerization pressure had a significant effect on the inhibition depth (P < 0.001). No inhibition layer was observed in the samples polymerized in water. The results suggest that in order to obtain an adequate degree of polymerization on the surface of autopolymerizing PMMA resin, the polymerization process should be carried out in water.

Oxygen inhibition of autopolymerization of polymethylmethacrylate-glass fibre composite.

The aim of this study was to determine the thickness of the unpolymerized surface layer of autopolymerizing polymethylmethacrylate (PMMA) and PMMA-glass fibre (GF) composite. Powder-to-liquid (P/L) ratios of 10 : 8, 10 : 9 and 10 : 10 by weight of the commercial PMMA was tested and the E-glass fibre weave was used as filler in the PMMA-GF composite. The resin was polymerized between two glass plates at 55 degrees C in air under an air pressure of 300 kPa. Five samples were polymerized for each test group. The inhibition depth was measured by a light microscopic technique with polarized light. The inhibition depth was affected by the P/L ratio of the PMMA: the mean inhibition depth of the unfilled PMMA with the P/L ratio of 10 : 10 was 248.6 microm, while it was 175.4 microm in PMMA with the P/L ratio of 10 : 8 (p=0.044). The inhibition depths were higher in the PMMA-GF composite than in the plain PMMA, which was explained by an inadequate impregnation of the GF weave with the PMMA resin. The results suggest that improper impregnation of the fibre product with autopolymerizing PMMA resin can cause oxygen inhibition of the polymerization reaction which should be taken into account when fibre products are clinically used.

Custom impression trays: Part I—Mechanical properties

Dimensional stability of custom impression trays is an important factor in determining the degree of accuracy achieved in forming a master cast. Such trays must remain stable over time and must not exhibit permanent deformation when a completed impression is removed from the oral cavity. Measurement of the mechanical properties allows comparison between various tray materials and is useful in interpreting data on stresses incurred during removal of the completed impression. In Part I of this three-part series, the various mechanical properties of five tray resins: one autopolymerizing polymethyl methacrylate, one light-polymerizing, and three brands of thermoplastic resins were recorded and compared. The thermoplastic resins studied in this investigation exhibited lower measured values for the strength and elastic modulus properties than the light-polymerizing resin and the autopolymerizing polymethyl methacrylate resin studied.

Effect of impression tray design and impression technique upon the accuracy of stone casts produced from a putty-wash polyvinyl siloxane impression material

This study examined the accuracy of stone casts produced from impressions taken in stock polycarbonate trays, some of which had been strengthened with autopolymerizing polymethyl methacrylate resin. Three techniques were used to make the impression of an acrylic master model of the mandibular arch on which two extracoronal preparations for bridgework and one intracoronal inlay preparation had been carried out. Each preparation had been indented with a reference point for later measurement. The impression material was a putty-wash polyvinyl siloxane material. Five impressions were taken for each type of tray for each impression technique and these were cast in die-stone after 24 h. The distances between the points were measured with a reflex microscope and the means determined for each design of tray. The mean difference between casts produced from the various tray designs and the acrylic master model were determined for each of the distances between the three measuring points for the various impression techniques. Statistical analysis showed that, with the polycarbonate stock trays, there were significant differences between some of the modifications and between them and the acrylic model, for the three distances ( P < 0.05). These differences were limited to one measurement for one design of tray for each of the two-stage impression methods. With the one-stage technique the unreinforced tray and those reinforced with acrylic, over the heels and anteriorly, and the barred design were statistically significantly different from the acrylic model for measurement A-B. It would appear from this study that the design of tray, or the impression technique employed, has little effect on the accuracy of impressions made with the polyvinyl siloxane material tested when used as a putty-wash and a two-stage technique, but that the accuracy of the impression material within the bulk of the material (A-B) was affected adversely using a one-stage technique.

Physical properties of acrylic resin polymerized by four different techniques

A utopolymerizing acrylic resin is used frequently in fixed prosthodontics to make provisional restorations, many of which are expected to remain in service for extended periods of time (Fig. 1). Physical properties of strength, density, and hardness may predict the longevity of such restorations. Provisiona restorations may be made intraorally or by an indirect technique. The indirect technique has significant advantages, including improved marginal integrity and prevention of pulpal injury caused by exothermic polymerization of the acrylic resin.lm3 Several techniques for polymerizing acrylic resin have been advocated, including processing under pressure in water to improve the physical properties.4,5 Scant scientific documentation exists to justify a particular technique.6 The purpose of this study was to determine the transverse strength, porosity, and hardness of an autopolymerizing polymethyl methacrylate resin processed under the following conditions: (1) polymerization in air, (2) polymerization under water, (3) polymerization under air pressure, and (4) polymerization under water under air pressure. Fig. 1. Provisional fixed partial denture processed in pressure pot functioned successfully for several months.