Heat-cured Denture Base Resin Research Articles

Effect of Water Storage on the Flexural Strength of Heat-cured Denture Base Resin Reinforced with Stick (s) Glass Fibers.

Background:Flexural strength (FS) of denture base resins (DBRs) had been improved by reinforcing it with different glass fibers. However, a limited data are available on the effect of glass fiber reinforcement with conventional heat-cured resin after prolonged water storage.Aims and ObjectivesThis study aimed to evaluate the reinforcing effect of novel S-glass and nylon fibers on the FS of acrylic DBRs. It also aimed to evaluate the effect of glass fiber reinforcement on the FS of acrylic DBRs after a prolonged storage in water.Materials and Methods:One hundred and sixty identical specimens were fabricated in specially designed molds according to the manufacturer's instructions. The three experimental groups were prepared consisting of conventional (unreinforced) acrylic resin, novel S-glass fiber-reinforced and nylon fiber-reinforced acrylic resin. The specimens were fabricated in a standardized fashion for each experimental group. Each group was further subdivided into two groups on the basis of storage conditions (dry and wet). FS was tested using a three-point universal testing machine at a crosshead speed of 5 mm/min. Glass fiber-reinforced group was further tested after prolonged storage in distilled water. Entered data were statistically analyzed with one-way ANOVA and least significant difference post hoc test.Results:In this study, statistically significant differences were noted in the FS of all the groups. S-glass fiber-reinforced group had highest FS compared to the other two groups (P < 0.001). Nylon fiber-reinforced group had lowest FS. All the groups stored in distilled water revealed a decrease in strength compared to those stored in dry atmosphere. Among wet specimens, those stored for 3 weeks had a significantly higher FS than those stored at one and 2 weeks (P < 0.01).Conclusion:Within the limitations of this investigation, the FS of heat-cured acrylic DBR was improved after reinforcement with glass fibers. It can be recommended to strengthen distal extension partial and complete denture bases. Nylon fibers may not be desirable for strengthening acrylic denture bases.

The effect of ZrN coating for improved esthetics on shear bond strength between Cp titanium and heat-cured denture base resin

Purpose: This study was performed to evaluate the effect of ZrN coating on shear bond strength between commercially pure titanium and denture base resin. Materials and Methods: ZrN was coated on CP titanium by ion plating method after sandblasting with aluminum oxide. Denture base resin (6mm diamete...

Variations in Flexural Strength of Heat-polymerized Acrylic Resin after the Usage of Denture Cleansers.

The objective of this study was to evaluate and compare changes in the flexural strength of heat-cured denture base resins when treated using denture cleansers. A total of 40 specimens with dimension 65 mm length, 10 mm width, and 3 mm thickness were prepared as per ISO 1567 specification. A total of 10 specimens were immersed in distilled water to be used as control. Of the remaining 30 samples, 10 were treated with Clinsodent, 10 with VI-Clean, and 10 with Clanden denture cleansers. Specimens in each group were subjected to three-point flexural load in universal testing machine at a cross-head speed of 5 mm/min. The peak load (N) was recorded and flexural strength was calculated. The findings were analyzed using Kruskal-Wallis analysis of variance and Mann-Whitney test. Heat-cured denture base resin selected for this study showed significant difference in flexural strength after immersion in denture cleansers Clinsodent, VI-Clean, and Clanden solutions, when compared with the control group. Findings of this study showed that denture cleansers altered the flexural strength of heat polymerized acrylic resins that endured soaking cycles which simulated 180 days of use. Hence, denture cleansers should be used with caution, once a day after brushing the dentures. It is advisable for patients to follow the manufacturer's instructions.

Color Stability of Heat-cure Acrylic Resin Subjected to Simulated Short-term Immersion in Fast-acting Denture Cleansers.

Background:Regular usage of denture cleansers is recommended in complete denture wearers for effective plaque control, and these cleansers alter the physical properties of acrylic resin over a period of time. Thus, an in vitro study was carried out to assess the effect of denture cleansers on the color stability of heat-cure denture base resin.Aim:The aim of the present study was to evaluate the effect of commercially available fast-acting denture cleansers on the color stability of heat-cure denture base resin at different time intervals.Materials and Methods:Thirty-six heat-cure acrylic resin (Ivoclar Triplex Hot-V) specimens are randomly allocated into four groups – Group A (distilled water as control); Group B (polident – 3 min); Group C (fixodent scope plus); and Group D (stain away plus) comprising of nine samples each. After recording the baseline values, the specimens were immersed in their respective cleansing solutions for a prescribed time interval. This procedure was repeated daily, and the color change (ΔE) was evaluated after 90 and 180 days interval using a colorimeter in a standard “Commission International de l'Eclairage” color system.Statistical Analysis Used:Paired t-test and Dunnett's T3 test.Results:All the groups exhibited a variable color change (ΔE) for an immersion period of 90 days. However, significant color differences (P = 0.001) were noticed among the test groups after 180 days.Conclusion:The color change of denture base resin was greater for Group D followed by Groups B, C, and A respectively after 180 days of immersion. The ΔE values of all test groups increased with time.

Color Stability of Heat-Cured Denture Base Resins

Heat-cured denture base resin is an important component in removable partial dentures and complete dentures, and has been widely used in the clinic. However, during long-term use, its appearance may be affected by varying degrees of color change, affecting the appearance and longevity of the dentures. In this study we examined the color changes and water absorption and solubility of dental base resins to investigate the color stability of four types of resin materials: New Century, Heraeus, Nissin and BASIS-HI. They were soaked in artificial saliva (as control), red wine, cola, coffee and tea separately at 37°C for 1, 4 or 12 weeks. Results are presented on which the color changes of dental base resin materials were associated with different denture base resins, soak solutions and storage times. We found that most of the dental resins became darker at prolonged immersion time. Heraeus resins showed more significant changes after soaking in red wine for 12 weeks, and its water absorption and solubility values were also greater than those of the other three types of resins. The color changes of New Century, Nissin and BASIS-HI soaked in the four solutions were relatively stable. The information obtained here will help optimize maintenance of dentures and also inform choice of denture materials.

Effect of high-pressure polymerization on mechanical properties of PMMA denture base resin

The aim of this study was to assess the effect of high-pressure polymerization on mechanical properties of denture base resin. A heat-curing denture base resin and an experimental PMMA were polymerized under 500MPa of pressure by means of an isostatic pressurization machine at 70°C for 24h to make rectangular specimens whose dimensions were 30mm×2mm×2mm. Each specimen was deflected on a three-point flexural test until either fracture occurred or the sample was loaded up to 8mm in deflection. The molecular weight of the PMMA without filler was analyzed using the high-speed liquid chromatography system. Increased ductility without fracture was shown in the specimens subjected to high pressure, while most of the control specimens (ambient pressure) fractured. The mean toughness of the PMMA specimens polymerized under the high pressure was significantly higher than the same material polymerized under ambient pressure (p<0.01). The high pressure groups of the denture resin and the PMMA revealed a significantly lower mean 0.2% yield stress, flexural strength, and elastic modulus than control groups (p<0.01). There were certain amounts of higher molecular weight polymers in the high pressure specimens than were present in the controls. The increased toughness shown in the PMMA polymerized under the high pressure was presumably attributed to the higher molecular weight produced by the pressure. The result suggests a potential application of the high-pressure polymerization to the development of PMMA-based denture resin with improved fracture resistance.

Shear Bond Strength of Acrylic Teeth to Heat-curing Denture Base Resin under Different Disinfectant Methods

El objetivo de este estudio fue evaluar la resistencia al cizallamiento entre dientes de resina acrilica y bases acrilicas curadas mediante calor, junto al uso de cinco soluciones de desinfectantes diferentes, mediante inmersion simple o bajo ultrasonido. Un total de 144 bases de acrilico fueron confeccionadas con los dos tipos de dientes de resina (Biolux ® y Trilux ®). Los especimenes se dividieron aleatoriamente en subgrupos de acuerdo con el procedimiento de desinfeccion utilizado (inmersion en Listerine ®, Cepacol ®, Periogard ®, Riozyme II ® y Cloro Rio ® 1%, y/o accion de limpieza por ultrasonido). Se evaluo la resistencia al cizallamiento entre los dientes de resina y la base de la protesis utilizando una maquina de ensayo universal; los datos obtenidos se analizaron mediante ANOVA seguido por el test LSD de Fisher de comparaciones multiples. Las dos capas de los dientes presentaron una fuerza de adherencia promedio de 3,43 MPa, mientras que las tres capas tenian un promedio de 3,02 MPa. La asociacion de limpiador ultrasonico y las soluciones desinfectantes estudiados no afectaron negativamente la resistencia de los dientes a la base de la protesis. Las tres capas de acrilico de los dientes tuvieron una resistencia al cizallamiento menor en comparacion con aquellos con doble prensado cuando se sumergen en soluciones desinfectantes, independientemente del uso de limpiador ultrasonico.

Effect of modified zirconium oxide nano-fillers addition on some properties of heat cure acrylic denture base material

Background: Polymer nano composite attracted great attention especially because of their unexpected hybrid properties that are synergistically derived from the two components. The aim of this study was to evaluate the effect of addition of modified nano-zirconium oxide on some properties of heat cured acrylic denture base material. Materials and methods: Zirconium oxide nano fillers modified by a silane coupling agent Tri (methoxysilyl) propyl methacrylate before dispersed and sonicated in monomer (MMA)in different percentage 2%,3%and 5%by weight. Three hundreds and twenty specimens were prepared for these studies were divided into five main groups according to the test used. The tests were abrasive wear, water sorption and solubility, porosity, tensile and fatigue strength test. For each test four sub groups (one control and three for different weight percentage of nano-ZrO2). Scanning electron microscope techniques used to analyze the fracture surface of fatigue test and estimate the dispersion and distribution of the nano-ZrO2 particles. Results: Highly significant increase in abrasive wear resistance with 3wt% and 5wt% of nano fillers with all groups of denture cleansers. highly significant decrease in water sorption and solubility. Significant decrease in porosity in 3wt% and 5wt%. Highly significant increase in both tensile and fatigue strength in all groups but slightly decreased in 5wt% as compared with 3wt% but still high significant as compared with control group. Conclusion: incorporating the modified nano-ZrO2 into acrylic resin results in improvement in abrasive wear resistance, tensile and fatigue strength in addition decrease in water sorption, solubility and porosity of heat cure denture base resin.

Peel bond strength of two silicone soft liners to a heat-cured denture base resin.

This study investigated the peel strength of two different soft liners to a polymethylmethacrylate (PMMA) denture base resin before and after thermocycling. The silicone-based soft liner materials tested were Molloplast B and Permaflex; the denture base material was a heat-cured acrylic resin, Meliodent. A total of 40 specimens was prepared using rectangular molds with dimensions of 100 x 10 x 2 mm for PMMA and 150 x 10 x 2 mm for soft liners, as described in ASTM-D903-93. For each of the liner materials, 10 specimens were packed against a cured PMMA denture base surface as recommended by the manufacturers. The other 10 specimens were packed against PMMA denture base dough and processed together. In each group, 5 of the specimens were tested directly, while the other 5 were thermocycled in a water bath (5°C to 55°C; 3000 cycles) before testing. Peel testing was performed using an Instron testing machine. The results revealed that peel strength values of the Permaflex specimens prepared according to the manufacturer's recommendations were significantly higher than those of Molloplast B (p < 0.05). However, when packing was done against uncured PMMA dough, the difference between the specimens of two liners was not significant. Thermocycling led to significant decreases in the peel strength of both Permaflex liner specimens packed against cured/uncured PMMA resin surfaces (p < 0.05), whereas this process did not affect the strength of Molloplast B specimens. Results indicated that the material Molloplast B was superior to the material Permaflex in terms of peel strength when the specimens were simultaneously polymerized with PMMA and thermocycled.

The Effect of Surface Treatments on Tensile Bond Strength between a Silicone Soft Liner and a Heat-Cured Denture Base Resin

This study evaluated tensile bond strength of a denture soft lining material to a poly (methylmethacrylate) (PMMA) denture base resin subjected to different surface treatment modalities and thermocycling. The materials tested were a silicone-based liner, Molloplast B®, and a heat-cured denture base resin, MeliodentTM. The denture soft lining material was packed against cured PMMA base resin, which was smoothed; sandblasted with 250-μm Al2O3 particles; or lased with a KTP laser; or against uncured PMMA dough (n = 10). In each group, five specimens were thermocycled in a water bath (5–55°C; 3000 cycles) before testing, whereas the other five were directly tested after 24 h. A tensile test was performed using a universal testing machine. Data showed that different treatment modalities of resin surfaces affected adhesion between these two materials and the highest bond values were recorded for cured/smoothed samples under each condition tested. Thermocycling of specimens had no significant reducing effect on measured bond strength values.

Bond of acrylic teeth to different denture base resins after various surface-conditioning methods

The study examined the bond between different denture base resins and highly cross-linked acrylic denture teeth with different base surface-conditioning methods. One hundred fifty highly cross-linked resin denture teeth (SR-Antaris, No. 11, Ivoclar-Vivadent, FL) were divided into five groups with different surface-conditioning methods of the base surfaces of the teeth (C = control, no surface conditioning, MM = application of methyl methacrylate monomer, SB = sand blasting, SBB = sand blasting + bonding agent, TSS = tribochemical silica coating + silanization). Teeth were bonded to either a cold-cured denture base resin (ProBase Cold, Ivoclar-Vivadent, FL) or heat-cured denture base resins (SR Ivocap Plus, Ivoclar-Vivadent, FL and Lucitone 199, Dentsply, USA). After 24 h of storage in distilled water, compressive load was applied at 90° on the palatal surface of each tooth until fracture. Median failure load ranged between 103 and 257 N for Probase Cold groups, 91 to 261 N for Lucitone 199, and 149 to 320 N for SR Ivocap Plus. For Probase Cold, significant highest failure loads resulted when teeth were treated with SB, SBB, or TSS. For Lucitone 199, significant highest failure loads has been found with MM and TSS treatment. For SR Ivocap Plus, highest failure loads resulted using SBB and TSS. Conditioning of the base surfaces of the teeth prior to denture base processing is highly recommended. Tooth bond is significantly affected by the surface-conditioning method and applied denture base resin. Tribochemical silica coating + silanization method can be recommended for pre-treatment of teeth applying either heat-cured or cold-cured denture base resin.

The Effect of Esthetic Fibers on Impact Resistance of a Conventional Heat-cured Denture Base Resin

This study was conducted to observe the changes in impact resistance of a denture base resin reinforced with five types of fiber. E-glass, polyester, rayon, nylon 6, and nylon 6/6 fibers were cut into 2, 4, and 6 mm lengths and added into the resin at a concentration of 3% by weight. Five test specimens for each formulation, as well as control specimens without fiber, were prepared using a mold including a V-shaped notch with 55 x 10 x10 mm dimensions. Impact tests were carried out using a Charpy-type tester. Additionally, surfaces of the impact sections were observed under a scanning electron microscope (SEM). Results indicated that impact energy tended to increase with fiber length, and that the highest value was recorded for rayon fiber-reinforced specimens of 6 mm length. E-glass fiber reinforcement produced relatively stable, high values for each length, whereby good interfacial strength between polymer matrix and glass fibers was confirmed by SEM analysis.

Influence of Polishing of Denture Base Resin and Metal Surfaces on Wettability with Water and Saliva

The purpose of this study was to investigate the influence of the surface roughness of denture base resin and metal on wettability with water and saliva. Solid specimens were produced using heat-curing denture base resin and Co-Cr alloy. After polymerizing or casting these materials, specimens with four different types of surface roughness were produced by a progressive polishing process using polishing papers (#240, #400, and #1,000) and cotton buffs. Surface roughness decreased significantly as the polishing process progressed (p<0.0001). Contact angle increased as surface roughness in metal specimens decreased, but decreased as surface roughness in resin specimens decreased (p<0.0001). Furthermore, differences in contact angle between tap water and saliva were larger in metal specimens (p<0.0001). These results suggested that with regard to the tissue surface of a denture base, the influence of its roughness on adhesive force differed according to the type of denture base material.

Flexural Strengths of Denture Base Resin Repaired with Autopolymerizing Resin and Reinforcements After Thermocycle Stressing

Fracture of an acrylic denture base is a common problem in prosthodontic practice. Although various reinforcement methods have been used, when a fractured denture base is repaired with autopolymerizing resin recurrent fractures frequently occur at the repairing interface or adjacent areas. The purpose of this study was to evaluate the maximum flexural load of denture base resin repaired with autopolymerizing resin and several reinforcement systems after thermocycle stressing. Rectangular (10 x 70 x 3 mm) flexural specimens were fabricated by repairing a pair of heat-cured denture base resin specimens using autopolymerizing resin and a series of reinforcement materials. The materials included 4 metal wires and a woven glass fiber. Each reinforcement was embedded in the center of the specimens. Flexural specimens repaired without reinforcement were prepared as controls. Specimens were subjected to 50,000 thermocycles (4 approximately 60 degrees C, 1-minute dwell time). A 3-point flexural test was carried out by loading the center of the repaired site at 5 mm/minute crosshead speed with 50 mm span jig supports. The load necessary to cause fracture was recorded for each specimen. All data were statistically analyzed using ANOVA and the Bonferroni/Dunn test (alpha < 0.05). The average load to fracture of specimens repaired with nonreinforced autopolymerizing resin was 68.4 N after 50,000 thermocycles. Specimens reinforced with 1.2 mm diameter stainless steel wire exhibited the highest value (89.8 N). The value for specimens reinforced with 1.2 mm diameter Co-Cr-Ni wire was 86.6 N. These fracture loads were significantly higher than those for specimens without reinforcement (p < 0.05). Low elasticity reinforcement, such as pure titanium wires, woven metal wire, and woven glass fiber were not effective in increasing the load to fracture values of flexural specimens. Specimens reinforced with 1.2 mm diameter stainless steel wires or Co-Cr-Ni wires resulted in significantly higher loads to fracture as compared to specimens without reinforcement. The use of pure titanium wire, woven metal wire, and woven glass fiber did not improve the fracture loads.

Effect of bench cooling on the dimensional accuracy of heat-cured acrylic denture base material

In order to obtain an insight on the internal stress caused by both polymerization and thermal shrinkage during the fabrication process of heat-cured denture resin, the effect of bench cooling on the dimensional accuracy of a heat-cured denture base resin was examined. A dimensional change of a dumbbell-shaped specimen during the fabrication process was measured directly by using the strain gauge method. After polymerization, the specimens were treated in one of the following two processing methods: (1) rapid cooling: the specimen was removed from a stone mold within a container of boiling water at 100 degrees C and then left to cool in a thermo-stabilized room of 20+/-1 degrees C; (2) bench cooling: the flask was left to cool in a thermo-stabilized room of 20+/-1 degrees C for 140min, after which, the specimen was removed from the stone mold. The strain from deflasking was derived from the difference in the strain, before and after the removal of the specimen from the stone mold. The strain differential, before and after cooling, was determined as the total strain. The bench cooling for the heat-cured denture base resin reduced the strain caused by thermal shrinkage during the fabrication process. The observed reduction in the strain was 26% for the C(L) (direction of center's length), 11% for the E(L) (direction of left-edge's length), and 12% for the E(W) (direction of left-edge's width), when compared with the results obtained from the rapid-cooling method. The flask should be slowly cooled to room temperature, since the internal stress developed by thermal shrinkage will be relaxed during the cooling process.

Bending Strengths of Metal Framework Structures for Implant-stabilized Overdentures

Purpose : This study evaluated the bending strengths of five types of framework structures for implant-stabilized overdentures.Materials and Methods : Five types of framework structures for implant-stabilized removable prostheses were cast using a Co-Cr alloy : conventional housing (Type A), housing with short skeleton (Type B), long skeleton only (Type C), housing with long skeleton (Type D), and Type D plus a metal backing connected by columns (Type E ; hereinafter referred to as the “double structure”). All castings were embedded in a heat-cured denture base resin. As controls, the same size resin blocks without frameworks were prepared. A bending test was used to test each specimen as it acted as a fulcrum on the implant. Breaking load, maximum stiffness, and strain were measured.Results : The breaking load and maximum stiffness of the double structure were significantly greater (p<0.05), i.e., 1.5-4.5 times and 2-6 times greater, respectively, than for the conventional frameworks.Conclusion : When the double structure framework was used for implant-stabilized prostheses, the bending strengths were greater than for the conventional housing design.

Environmental Stress Cracking of Heat-cured Denture Base Resin : Effect of Environmental Solutions on Lower Limit of Stress Intensity Factor

Environmental Stress Cracking of Heat-cured Denture Base Resin : Effect of Environmental Solutions on Lower Limit of Stress Intensity Factor

Environmental Stress Cracking of Heat-cured Denture Base Resin : Effect of Environmental Solutions and Their Concentrations

Environmental Stress Cracking of Heat-cured Denture Base Resin : Effect of Environmental Solutions and Their Concentrations

抗菌性床用レジンに関する研究 機械的性質および抗菌性について

Many reports have pointed out that Candida albicans (C. albicans) is one of the main causative factors of denture stomatitis. Test denture polymers containing an antibacterial (A-B) agent were developed for the prevention of denture stomatitis. Bacteriostatic activity of A-B agents against C. albicans and the effects of A-B agents on mechanical properties were investigated in this study. A-B agent was contaminated and immersed in the conventional heat-cured denture base resin polymer as 1, 3, 5, and 7 wt% respectively. The flexural strength test, knoop hardness test, linear shrinkage measurement, and water absorption measurement were performed. The colonies of C. albicans were counted on the Glucose peptone agar with Lecithin & Polysorbate 80 agar preparations on the thermal test pieces.The results were as follows: All mechanical properties were hardly influenced when any percentage of AB agents (p>0.05) was contained. Bacteriostasis was clearly observed in the test polymers containing over 3% A-B agent. The minimum percentage of A-B agent that does not degrade the denture polymers was considered to be 3%.

低刺激性直接リライニング材で裏装した加熱重合型床用レジンの比例限における曲げ強さ

This study was conducted to investigate the transverse strength at the proportional limit of a heat-cured denture base resin relined with low stimulative direct denture reline materials. The relined specimens with three low stimulative and a conventional self-cured direct denture reline materials were tested with a three-point loading test after 1 day of water immersion. Direction of load on the specimens also was tested. As a result, all relined specimens had significantly lower transverse strength than bulk of a heat-cured denture base material. The transverse strength of specimens relined with low stimulative direct denture reline materials was significantly low as compared with specimens relined with a conventional self-cured type direct denture reline material. There was no significant difference among three low stimulative direct denture reline materials. The direction of load on the specimens did not have an effect on the transverse strength at the proportional limit.