[Studies on dental methyacrylic resins. 3. Composition and physical properties of several poured acrylic resins].
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Acrylic Resins↗
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Flexural properties of acrylic resin polymers reinforced with unidirectional and woven glass fibers.
STATEMENT OF PROBLEM: Fiber-reinforced plastics for dental applications have been under development for some time. A major difficulty in using reinforcing fibers with multiphase acrylic resins, such as powderliquid resins, has been improper impregnation of fibers with the resin. PURPOSE: The aim of this study was to describe and test a novel system to use polymer-preimpregnated reinforcing fibers with commonly used multiphase acrylic resins. MATERIAL AND METHODS: Continuous unidirectional and woven preimpregnated glass fiber reinforcements (Stick and Stick Net) were used to reinforce heat-curing denture base and autopolymerizing denture base polymers. A temporary fixed partial denture polymer was also reinforced with Stick reinforcement material. Five test specimens were fabricated for unreinforced control groups and for Stick- and Stick Net-reinforced groups. A 3-point loading test was used to measure transverse strength and flexural modulus of the materials and ultimate strain at fracture was calculated. Cross-sections of test specimens were examined with a SEM to evaluate degree of impregnation of fibers with polymer matrix. Quantity of fibers in test specimens was determined by combustion analysis. RESULTS: Transverse strength of heat-curing denture base polymer was 76 MPa, Stick reinforcement increased it to 341 MPa, and flexural modulus increased from 2550 to 19086 MPa. Stick Net reinforcement increased transverse strength of heat-curing denture base polymer to 99 MPa and flexural modulus to 3530 MPa. Transverse strength of autopolymerizing denture base polymer was 71 MPa; Stick increased it to 466 MPa; and flexural modulus increased from 2418 to 16749 MPa. Stick Net increased the transverse strength of autopolymerizing denture base polymer to 96 MPa and flexural modulus to 3573 MPa. Transverse strength of temporary fixed partial denture polymer increased from 58 to 241 MPa and flexural modulus from 1711 to 7227 MPa. ANOVA showed that reinforcement type and polymer brand affected transverse strength and modulus (P <.001). Stick Net reinforcement increased the strain at fracture, whereas Stick reinforcement decreased the strain values. SEM examination revealed well-impregnated glass fibers with polymer matrix. Quantity of glass fibers varied from 6 to 28 vol-%, the lowest being with Stick Net reinforcement and the highest with Stick reinforcement. CONCLUSIONS: Novel glass fiber reinforcements may considerably enhance flexural properties of multiphase dental polymers, which is due to proper impregnation of fibers with polymer matrix. By using Stick or Stick Net reinforcement, the strain at fracture of the material can be modified.
Acrylic Resins↗
The effects of various disinfectant solutions on the surface hardness of an acrylic resin denture base material.
There is an increasing awareness of the importance of cross-infection control in dental clinics and laboratories. This study evaluates the effects of various disinfecting solutions on the surface hardness of an acrylic resin denture base material. Hardness was measured as resistance to indentation following the method specified by the British Standards Institute. The results demonstrated that immersion of denture base acrylic resin in disinfecting solution for up to 24 hours resulted in no significant effect on hardness values.
Acrylic Resins↗
Adaptation of acrylic resin dentures as influenced by the activation mode of polymerization.
With the advent of newer methods of activation of the polymerization of denture base resins, there is a need to compare dentures constructed using various modes of activation such as heat, light, and microwave energy. This study compares the dimensional accuracy of a conventional heat-activated acrylic resin poly (methyl methacrylate) with a new pour resin, a visible light-activated resin, and microwave-activated acrylic resin, all polymerized for denture bases. All groups showed a processing contraction; the poorest-fitting group was processed in a brass flask and a water bath at 70-100 C, using a heat-activated resin (Acron); the relatively new light-activated resin (Triad) produced dentures of intermediate accuracy, as did Acupac 20, when either heat- or microwave-activated. The two best-fitting groups were prepared from an autopolymerizing resin (PERform) and the microwave-activated resin (Acron MC).
Chemical Phenomena↗
Color stability of denture base acrylic resins in three food colorants.
STATEMENT OF PROBLEM: Three commonly used artificial dyes in food technology are erythrosine, tartrazine, and sunset yellow. PURPOSE: The color stability of 5 commercially available denture base acrylic resins (QC-20, Meliodent, Trevalon, Trevalon High, and Lucitone) was studied in vitro. METHODS: The specimens were exposed to 3% erythrosine, tartrazine, and sunset yellow solutions at 23 degrees C +/- 1 degrees C. Color changes were determined with a computer-controlled spectrophotometer. Five specimens from each material were processed, and initial color measurements were made after 1, 3, and 6 months of exposure to the staining solutions. Finally, the color stability was quantitatively measured again, and color differences (DeltaE) were calculated. RESULTS: For the observations made in 1, 3, and 6 months intervals, the specimens that exhibited the least color change were in the sunset yellow solution. The greatest color changes observed according to the National Bureau of Standards unit system were Lucitone (2.71) in erythrosine solution, Lucitone (2.54), QC-20 (1.71) in tartrazine solution, and QC-20 (1.66) in sunset yellow solution. The changes in the other acrylic resins in the 3 solutions were slight and at trace level. CONCLUSIONS: All materials tested were acceptable from the standpoint of color stability for long-term exposure to these food colorants.
Acrylic Resins↗
[Experimental study of acrylic resin coated gentamicin tablets for local antibiotic therapy].
Gentamicin tablets were prepared and evaluated for local antibiotic therapy. Two types of tablet were used. One, a slow release tablet, was coated with acrylic resin (Eudragit R.S.) and another was non-coated. The release of gentamicin from the coated tablets can be controlled by changing the thickness of the film coating. The thickness of the film coating was adjusted to release gentamicin within three weeks when placed in Ringer's solution. Coated tablets were inserted into the bone marrow of rabbits. Thereafter, daily excretion of gentamicin was measured in the urine for three weeks. Constant excretion of gentamicin was seen for ten to fourteen days, which suggests the release of gentamicin from the bone marrow. Plasma concentrations were very low, thus precluding side effects. Non-coated tablets were inserted to the bone marrow by the same method as above. Plasma concentrations of gentamicin peaked in one hour and then rapidly decreased. This pattern is similar to that seen with intramuscular administration. As acrylic resin was non-absorbable material in vivo, the tissue reactions around coated tablets were examined. Histological findings at three weeks, six weeks and six months after insertion, respectively, did not show any severe tissue reactions. The possible use of local therapy by coated antibiotic tablets for bone infections is discussed.
Acrylic Resins↗
Factors that affect the rheologic properties of acrylic resin denture base materials.
The rheologic characteristics of different formulations of acrylic resin denture base materials are presented in this study. This is of practical significance in selecting resins with optimum rheologic properties for denture base construction. The materials are characterized in respect to their constituents, mean powder particle size and distribution, molecular weight averages and distributions, and glass transition temperature. A comparison of the polymers indicates that smaller particles saturate with monomer more readily, and this results in a higher viscosity. A higher viscosity for higher molecular weight and lower viscosity for lower molecular weight have been observed. Increasing the percentage of copolymerization increases the viscosity. No correlation has been found between the rheologic properties of denture base polymers and the powder glass transition temperature.
Acrylic Resins↗
A technique for fabrication of polydimethylsiloxane-acrylic resin obturators.
A flexible silicone obturator is an alternative to the acrylic resin obturator. It can be useful for patients with severe trismus who cannot insert a large prosthesis, as the flexibility of the hollow silicone section allows easy placement and removal (Fig. 9). Other patients cannot tolerate an unyielding substance against sensitive nasal tissues. Silicone can provide the necessary comfort without compromising retention. Silicone obturator sections can often be modified when further surgery is needed and result in a savings of time and expense (Fig. 10). For patients who can be reevaluated only twice a year, several silicone obturator sections can be made initially. One can be used while another is being cleaned or duplicated.
Acrylic Resins↗
Construction of accurate acrylic resin provisional restorations.
A technique has been described for making accurate fitting acrylic resin provisional restorations with attention to marginal adaptation and ease of fabrication.
Acrylic Resins↗
Bond strength to primed Ti-6Al-7Nb alloy of two acrylic resin adhesives.
This study aimed to evaluate the bonding behavior of two acrylic resin adhesives joined to titanium-aluminum-niobium (Ti-6Al-7Nb) alloy primed with two metal conditioners. Cast Ti-6Al-7Nb alloy disks were air-abraded with alumina and bonded with six combinations of two resin adhesives (Super-Bond C&B and Multi Bond) and three surface conditions (Alloy Primer, M.L. Primer, and unprimed control). Shear bond strengths were determined both before and after 20,000 thermal cycles. The tri-n-butylborane initiated Super-Bond C and B resin exhibited greater bond strength than the BPO-amine initiated Multi-Bond resin. Both the Alloy Primer with a hydrophobic phosphate and the M.L. Primer with a phosphonoacetate effectively improved the 24-hour bond strength of Multi-Bond resin as well as the post-thermocycling bond strength of Super-Bond C and B resin.
Acid Etching, Dental↗
Effect of denture cleansers on the surface roughness and hardness of a microwave-cured acrylic resin and dental alloys.
PURPOSE: This study evaluated the effect of denture cleansers on the surface hardness of a denture base resin, and on the surface roughness of the resin and Co-Cr and Ti-6Al-4V alloys. MATERIALS AND METHODS: Forty-eight disc-shaped specimens were fabricated of a microwave-cured acrylic resin, each having one of the alloys attached to its surface. The specimens were randomly divided into 6 groups, each consisting of 8 samples. Specimens were exposed to one of the three cleansing treatments (polident, manipulation pharmacy cleanser, and water) as follows. Group I: Co-Cr + polident; Group II: Co-Cr + manipulation; Group III: Co-Cr + water; Group IV: Ti-6Al-4V + polident; Group V: Ti-6Al-4V + manipulation; and Group VI: Ti-6Al-4V + water. Three exposures lasting 5 minutes each were conducted daily, and repeated after storage periods of 1, 14, and 29 days in artificial saliva at 37 degrees C. Hardness and roughness measurements were undertaken immediately after specimen preparation (T0) and on the 1st (T1), 15th (T15), and 30th (T30) day following the beginning of storage. Three roughness and hardness evaluations were carried out for each sample and testing time, and mean values were calculated. Results were analyzed using ANOVA and linear regression. RESULTS: The Knoop hardness test demonstrated differences (p < 0.05) between Groups I and IV at T1 and T30 (14.30 +/- 2.78; 14.06 +/- 1.76) and between Groups II and V at T15 (16.99 +/- 2.24). Significant differences (p < 0.05) in resin roughness (in microm) were observed between Groups I and IV at T15 and T30 (0.14 +/- 0.06; 0.21 +/- 0.38). With regard to Co-Cr, roughness data showed differences (p < 0.05) for all groups at T30 (Group I: 0.15 +/- 0.07; Group II: 2.43 +/- 0.66; Group III: 4.05 +/- 1.03), for Group II at T1 (0.10 +/- 0.03), and for Group I at T15 (0.15 +/- 0.02). There were significant differences (p < 0.05) in titanium roughness for Group IV at T15 (0.12 +/- 0.01) and T30 (0.11 +/- 0.04). CONCLUSIONS: Manipulated cleanser containing sodium perborate increased surface roughness and hardness, probably due to its incapacity to remove the pellicle formed on the acrylic resin and dental alloys.
Acrylic Resins↗
Comparison of the in vitro fatigue resistance of an acrylic resin removable partial denture reinforced with continuous glass fibers or metal wires.
PURPOSE: The fatigue resistance of heat-polymerized acrylic resin test specimens reinforced with continuous glass fibers or metal wire was investigated. MATERIALS AND METHODS: Test specimens in the shape of maxillary removable partial dentures were reinforced with one of the following: (1) circular steel wire (cross-sectional diameter, 1.0 mm); (2) semicircular steel wire (cross-sectional diameter, 1.0 x 2.0 mm); or (3) continuous unidirectional E-glass fibers. Ten specimens were fabricated for each test group. The specimens were tested by a constant force flexural fatigue test at a force of 180 N while immersed in 37 degrees C water. The number of loading cycles required to generate a fatigue fracture and the position of the fracture were measured. RESULTS: Results showed that the test specimens, which were either unreinforced or reinforced with metal wires, fractured after 13,197 to 39,237 loading cycles. For the glass fiber-reinforced test specimens, the fracture did not coincide with the region of the strengthener but with the opposite side of the test specimen after 1,239,298 loading cycles. The position of the fracture showed a statistically significant variation between the test groups (P < .001). CONCLUSIONS: This study suggests that the fatigue resistance of acrylic resin removable partial dentures reinforced with glass fibers are superior to those removable partial dentures reinforced with conventional metal wire.
Analysis of Variance↗
Effect of disinfectants on the hardness and roughness of reline acrylic resins.
PURPOSE: Potential effects on hardness and roughness of a necessary and effective disinfecting regimen (1% sodium hypocholorite and 4% chlorhexidine) were investigated for two hard chairside reline resins versus a heat-polymerizing denture base acrylic resin. MATERIALS AND METHODS: Two standard hard chairside reliners (Kooliner and Duraliner II), one heat-treated chairside reliner (Duraliner II +10 minutes in water at 55 degrees C), and one standard denture base material (Lucitone 550) were exposed to two disinfecting solutions (1% sodium hypochlorite; 4% chlorhexidine gluconate), and tested for two surface properties [Vickers hardness number (VHN, kg/mm(2)); Roughness (Ra, microm)] for different times and conditions (1 hour after production, after 48 hours at 37 +/- 2 degrees C in water, after two disinfection cycles, after 7 days in disinfection solutions, after 7 days in water only). For each experimental condition, eight specimens were made from each material. Data were analyzed by analysis of variance followed by Tukey's test, and Student's t-test (p= 0.05). RESULTS: For Kooliner (from 6.2 +/- 0.3 to 6.5 +/- 0.5 VHN) and Lucitone 550 (from 16.5 +/- 0.4 to 18.4 +/- 1.7 VHN), no significant changes in hardness were observed either after the disinfection or after 7 days of immersion, regardless of the disinfectant solution used. For Duraliner II (from 4.0 +/- 0.1 to 4.2 +/- 0.1 VHN), with and without heat treatment, a small but significant increase in hardness was observed for the specimens immersed in the disinfectant solutions for 7 days (from 4.3 +/- 0.2 to 4.8 +/- 0.5 VHN). All materials showed no significant change in roughness (Kooliner: from 0.13 +/- 0.05 to 0.48 +/- 0.24 microm; Duraliner II, with and without heat treatment: from 0.15 +/- 0.04 to 0.29 +/- 0.07 microm; Lucitone 550: from 0.44 +/- 0.19 to 0.49 +/- 0.15 microm) after disinfection and after storage in water for 7 days. CONCLUSIONS: The disinfectant solutions, 1% sodium hypochlorite and 4% chlorhexidine gluconate, caused no apparent damage on hardness and roughness of the materials evaluated.
Acrylic Resins↗
Prefabricated acrylic resin bars for splinting implant transfer copings.
Splinting of implant transfer copings with acrylic resin during impression procedures is performed to accurately transfer the spatial relationships of implants to the master cast. However, distortion may occur during the splinting procedure because of resin polymerization shrinkage. This article describes a simple technique for minimizing this effect by fabrication of resin bars.
Acrylic Resins↗
The effect of time lapse on the accuracy of two acrylic resins used to assemble an implant framework for soldering.
STATEMENT OF PROBLEM: There are insufficient data on the accuracy of resin indexing materials for the assembly of implant prostheses in vivo. MATERIAL AND METHODS: This in vitro study assessed the fit of an implant framework with the use of 2 common acrylic resins. PURPOSE: A standardized type IV gold alloy cast framework with 3 stainless steel implant replicas secured to 3 premachined gold cylinders placed 200 mm apart using a parallelometer was fabricated on a flat type IV stone model. Wax was placed around the center of each bar section, and a silicone matrix was fabricated to enable the same quantity of material to be used for each assembly. Each bar was sectioned at the center of the matrix, and indices (n=20) were fabricated from Duralay and GC Pattern acrylic resins. The materials were allowed to polymerize for 15 minutes before the assemblies were removed from the model. Frameworks were visually assessed for fit after an additional 15 minutes, after 2 hours, and after 24 hours, using the Sheffield 1-screw test. Observational outcomes are presented indicating visually perceived fit relative to the type of indexing resin. RESULTS: Both indexing materials were judged to be visually accurate at the 15-minute time interval only. CONCLUSION: Within the limitations of this in vitro study, both resin-indexed implant assemblies were judged visually accurate for fit 15 minutes after polymerization but not at subsequent test intervals.
Acrylic Resins↗
Bonding orthodontic acrylic resin to enamel.
Bonded acrylic orthodontic appliances are a recent alternative to banded methods. However, the physical properties demonstrated by bonding adhesives at the acrylic-enamel interphase have not been well documented. The purpose of this study was to use a laboratory testing model to evaluate the ultimate shear and tensile strengths and fracture sites of five bonding adhesives: unfilled (Bracketbond and Genie); filled (Unite, Excel, and Concise). One hundred bovine mandibular incisors were embedded in dental stone, labial surfaces ground flat for uniform acrylic-enamel adaptation, and stored in modified Fusyama's artificial saliva. Twenty 7-mm diameter acrylic cylinders were bonded in each group. Ten samples from each group were tested for shear strength and ten for tensile strength with an Instron testing machine. Bonding adhesive retained on the cylinder was measured by means of a Bioquant digitizer. Scanning electron microscopy was used to analyze fracture sites. The results showed that the percentage of bonding adhesive that remains on the acrylic surface after fracture is decreased by the addition of inorganic fillers to the adhesive and the use of separate liquid resin sealants, and is increased by the use of plastic bracket primers and bonding adhesives that are chemically similar to methylmethacrylate. Few significant differences in shear and tensile strengths were found among the bonding adhesives. Unfilled bonding adhesives cause less enamel damage and are indicated for clinical bonding of acrylic orthodontic appliances to enamel.
Acrylic Resins↗
Processing the gingival and mucosal acrylic resin component of implant-supported prostheses.
A procedure for processing the acrylic resin portion of implant prostheses is presented whereby denture tooth displacement is avoided, abutment cylinders are protected, prosthesis screw access holes are provided, and laboratory guide pins are recovered for future use.
Acrylic Resins↗
[Stress analysis with a laser microscope analyzer for acrylic base resin]
Acrylic resin are applied widely as a denture resin,its residual stress is closely related with aging and mechanical properties of denture resin.The authors tested the stress level of the base resin with a laser microscope stress analyzer in the study.The results indicated that there was not statistical differences between two curing methods is in water bath or under pressure.The residual stress in base resin can be concentrated at the area near to clasp wire which was embedded in base resin for reinforcing strength of denture base.The vibration caused by grind with stone wheel or impact in disc lasting with a hammer may increase the stress level in base.The authors pointed out some methods for reducing residual stress resin.
Journal Article↗