The effect of chopped poly(methyl methacrylate) fibers on some properties of acrylic resin denture base material

PURPOSE: The fracture of acrylic resin dentures remains an unresolved problem. Over the years, various approaches to strengthening acrylic resin have been suggested, including modifying or reinforcing the resin. The aim of this study was to investigate the effect of chopped poly(methyl methacrylate) (PMMA) fibers on some properties of acrylic resin denture base material. MATERIALS AND METHODS: PMMA in the form of fibers 0.75 mm in diameter and 5 mm in length was added to acrylic resin denture base material in various percentages to form a composite material. The influence on doughing and manipulation times and transverse strength was examined. The results were subjected to statistical analysis using a one-way analysis of variance and, where appropriate, the Scheffé test. RESULTS: The results showed that the doughing time was decreased by the addition of fibers, with the manipulation and setting times showing inconsistent changes. There was a significant difference between the materials in terms of the transverse strength. When the amount of PMMA fibers in the acrylic resin was increased, there was a decrease in the modulus of rupture and a decrease in the modulus of elasticity. The differences were shown to be statistically significant in some groups. CONCLUSION: The doughing time was decreased by the addition of fibers, while the manipulation and setting times showed inconsistent changes. The incorporation of chopped, randomly oriented PMMA fibers into acrylic resin had no advantage over the unmodified polymer in terms of strength and cannot be recommended as a reinforcing agent for acrylic resin denture base material.     

Use of metal conditioner on reinforcement wires to improve denture repair strengths

The purpose of this study was to evaluate the transverse strength of denture base resin repaired with autopolymerizing resin and metal wire using a metal conditioner, along with the synergistic effect of a surface preparation for denture base resin. It was found that the use of Co-Cr-Ni wires air abraded with 50 microm alumina, followed by treatment with a metal conditioner and dichloromethane for denture base resin, was the most effective method for repairing fractured denture base resin.     

Effect of 180 Days of Water Storage on the Transverse Strength of Acetal Resin Denture Base Material

Purpose: Acetal resin has been used as an alternative denture base and clasp material since 1986. The manufacturers claim that acetal resin has superior physical properties when compared to conventional denture base acrylic resins. Limited information is available about transverse strengths of acetal resin. The purpose of this investigation was to compare transverse strengths of pink and white acetal resins to transverse strengths of conventional heat‐polymerized polymethylmethacrylate (PMMA) resin in increasing durations of water storage. Materials and Methods: A transverse strength test was performed in accordance with International Standards Organization (ISO) specification No 1567. Twenty 65 × 10 × 2.5 mm³ specimens of each resin were prepared; five specimens of each resin group were subjected to three‐point bending test after 50 hours, 30 days, 60 days, and 180 days of water storage in distilled water at 37°C. Experimental groups’ transverse strengths were compared by three‐way ANOVA and Duncan's multiple range tests. Results: Transverse strength of PMMA denture base material was found to be in accordance with the requirements of ISO specification No 1567. Transverse strengths of white and pink acetal resin could not be calculated in this study, as white and pink acetal resin specimens did not break at the maximum applied force in the three‐point bending test. Flexural strength of acetal resin was found to be within the ISO specification limits. As the water storage time increased, the deflection values of PMMA showed no significant difference (p > 0.05). Both the white and pink acetal resin showed significant increase in deflection as the water storage time was increased from 50 hours to 180 days (p < 0.05). Conclusion: The results of this study indicated that transverse strength values of PMMA were within the ISO specification limit. Water storage time (50 hours, 30, 60, and 180 days) had no statistically significant effect on the transverse strength and deflection of PMMA. Acetal resin suffered from permanent deformation, but did not break in the three‐point bending test. Acetal resin showed significant increase in deflection as the water storage time was increased from 50 hours to 180 days. All materials tested demonstrated deflection values in compliance with ISO specification No 1567.     

A Review of Fiber-Reinforced Denture Base Resins

Purpose One method of reinforcing denture base material is to use fiber composite reinforcement. Different types of fibers, such as glass (GF), carbon/graphite, aramid, and ultrahigh-modulus polyethylene (UHMP) fibers have been tested for this purpose. Materials and Methods This article reviews the studies conducted on the fiber-reinforced denture base resin systems. Results The literature has reported that the fiber concentration and its adhesion to polymer matrix influences the transverse strength of the fiber composite. The highest transverse strength value (265 MPa) with polymethyl methacrylate (PMMA) was obtained by incorporating 58 wt% GF into the resin. UHMP fibers incorporated into PMMA resin yielded the highest impact strength value (134 kJm^-2) of the fiber-PMMA composites. Conclusions Despite the improved mechanical properties of fiber-reinforced denture materials, further research is required to show the clinical usefulness of the fiber reinforcement.     

The effect of the addition of poly (methyl methacrylate) fibres on the transverse strength of repaired heat-cured acrylic resin

The aim of the present study was to investigate the effect of addition of an experimental poly (methyl methacrylate) (PMMA) fibre in linear form, 0.75 mm in diameter on the transverse strength of repaired heat-cured poly (methyl methacrylate) denture base material. Specimens of heat-cured PMMA were repaired with an autopolymerizing acrylic resin and an autopolymerizing acrylic resin together with the addition of untreated and surface-treated PMMA fibres in different arrangements. The transverse bend test was carried out using a LIoyd's Instrument Material Testing Machine. From the results, it can be concluded that the box incorporated into the repair joint produced a significant decrease in the moduli of elasticity and rupture which may be due to stress concentration effects. The addition of one layer of untreated PMMA fibres significantly decreased the modulus of rupture. The addition of two layers of untreated fibres produced a slight but statistically non-significant increase in the modulus of rupture. The addition of surface-treated (with butadiene styrene latex emulsion) fibres into the repair complex gave no improvement compared with the addition of untreated fibres in terms of transverse strength. There was an insignificant decrease in the modulus of rupture compared with the untreated fibres.     

Effe1ct of some properties of metal strengtheners on the fracture resistance of acrylic denture base material construction

In this study we investigated the effect of metal wire bonding to acrylic resin on the fracture resistance of an acrylic denture base material construction. Two different bonding methods were tested, and after measuring the resistance, the surface of the wires were examined by a scanning electron microscope. The effect that the placing of metal strengtheners in different positions in the acrylic resin had on the fracture resistance of the denture base material construction was also clarified. When three different positions of the metal wires in the acrylic resin were compared, the results showed that bonding of metal wire to acrylic resin somewhat enhanced the fracture resistance of test specimens, while the different positions of the wires had no effect on the fracture resistance.     

Reinforcement of Denture Base Resin with Glass Fillers

PURPOSE: This study evaluated the effect of short glass fibers on the transverse strength of a heat-polymerized acrylic resin denture base material. MATERIALS AND METHODS: Four groups of specimens (n = 10) were fabricated according to the ISO standard for the transverse strength test. E-glass fibers were triturated to produce short fibers of different lengths. Specimens for Group 1 (control) were made of unfilled polymethylmethacrylate (PMMA). For group 2, the PMMA powder was modified with 0.1 g of dry glass fibers. For group 3, the PMMA powder was modified with 0.1 g of silanized glass fibers. For group 4, the PMMA powder was modified with 0.2 g of silanized glass fibers. A three-point loading test was used to determine the transverse strength of the tested specimens. The fracture surface of each specimen was evaluated using SEM. RESULTS: The addition of untreated glass fibers increased the transverse strength by 11% but produced some porosity in the polymeric matrix. The addition of silane-treated glass fibers increased the transverse strength of PMMA by 28% for group 3 and by 26% for group 4, and produced a dense structure for the polymer-fiber composite. CONCLUSION: The transverse strength of PMMA can be slightly increased by the addition of short glass fibers.     

XPS study on the weakest zone in the adhesion structure between resin containing 4-META and precious metal alloys treated with different surface modification methods.

Three precious metal alloys, Type IV gold alloy, 14 K gold alloy, and silver-based alloy, were treated with different surface modifications including a metal primer (VBATDT) application, a SiOx coating method, high-temperature oxidation, modification method with a liquid Ga-Sn alloy, and tin electroplating. Then thin PMMA films were bonded with a resin containing 4-META. Water durability at the adhesion interface was evaluated after water immersion, followed by thermal cycling used liquid nitrogen. The weakest zone at the interface was investigated using XPS only for the Ag-Pd alloy specimens that had been surface-treated with as-polishing, adhesive primer, and the SiOx coating method, since peeling of the PMMA film on the surface of specimens surface-treated by other methods was not observed. Metal elements were detected from the resin side at the adhesion interface. The chemical states of Cu in the resin before argon ion etching were characterized as metal oxides and/or states of chemical interaction with 4-META, VBATDT, or SiOx.     

Silane effects on luting resin bond to a Ni---Cr alloy

This study investigates the effect of a silane coupling agent on the shear bond strength of four commercially available resin luting systems (two of which rely on mechanical retention and two which have a chemical bond to metal) when bonding a prepared Ni---Cr alloy to etched bovine enamel. Silane application reduced the bond strengths of the two chemically adhesive resins and increased the bond strength of one of the mechanically retained resins. For the other mechanically retained resin, silane application did not significantly increase the bond strength but the plane of fracture changed from resin/metal to resin/enamel: from this an increase in metal resin bond strength can be inferred.     

Shear bond strength of three veneering resins to a Ni-Cr alloy using two bonding procedures

Composite veneering materials are used as alternatives to porcelain in fixed prosthodontics. Mechanical retention of the resin on the metal framework has been associated with the formation of gaps at the resin/alloy interface, and failure of the restoration. Several chemical bonding systems have been introduced to promote resin adhesion. The purpose of the present study was to evaluate the shear bond strength of three photocured composites (Artglass, Solidex & Signum+) to a Ni-Cr alloy.72 wax disks covered with 150-mum diameter beads were cast and divided in two equal groups. In the first group, Metal Photo Primer was applied on the casting surface, while the Siloc system was used in the second. Each group was divided in three subgroups of 12 samples, in which the three composites were photocured. Half of the specimens of each subgroup were subjected to 1000 and 5000 thermal cycles (5 and 55 degrees C) respectively. All specimens were tested in shear in a universal testing machine. The Siloc-Solidex group showed the highest bond strength (17.3 +/- 3.7 MPa). No statistically significant difference was found between specimens treated with Metal Photo Primer or Siloc. Thermocycling did not significantly affect the bond strength values. Solidex showed an adhesive failure mode for both alloy surface treatments, while Artglass and Signum+ exhibited combination failures. Conclusively, the appropriate alloy surface treatment - resin combination can significantly improve the resin-alloy shear bond strength. Specifically, Solidex resin exhibited significantly higher bond values compared with Artglass and Signum+, for both surface treatments and thermocycling procedures.     

Effect of curing environment on mechanical properties and polymerizing behaviour of methyl-methacrylate autopolymerizing resin

Methyl-methacrylate autopolymerizing resin is used for multiple applications. Therefore, the mechanical properties of autopolymerizing resin should be assessed comprehensively including strength, stiffness and hardness. Any methods that effectively improve these mechanical properties are desirable. The objective of this study is to examine the effects of the curing environment: air or water with/without pressure, and air or water temperature during polymerization, on the strength, stiffness and hardness of autopolymerizing resin. In addition, we examined the polymerizing behaviour associated with the mechanical properties. Autopolymerizing methyl-methacrylate resin (Unifast II) was polymerized under the following conditions: in air and water with/without pressure at 10, 23, 30, 40, 60 and 80 degrees C. The resin specimens were subjected to a transverse test (three-point flexural test) and micro-Brinell surface hardness test. Fractured surfaces of the specimens after the transverse test were examined using a scanning electron microscope (SEM). The transverse strength and transverse modulus increased with increasing curing temperature in both wet and dry conditions. Pressured wet conditions increased transverse strength and transverse modulus over non-pressured wet and dry conditions. The resin polymerized in dry conditions showed higher surface hardness than the one polymerized in wet conditions at matching temperature. The SEM images of fractured surfaces cured at lower temperature exhibited porosity within the polymer base and cracks between the base and poly-methyl-methacrylate (PMMA) particulates. Surfaces of the resin polymerized in wet conditions were characterized with PMMA particulates having rougher surfaces suggestive of water incorporation. Raising temperature and pressuring during polymerization increase strength and stiffness of autopolymerizing resin. However, wet condition reduces surface hardness of resin compared with dry condition. These altered mechanical properties are associated with polymerization behaviour of the resin.     

Bond Strength of Resin Cements to Co‐Cr and Ni‐Cr Metal Alloys Using Adhesive Primers

Purpose: The aim of this study was to evaluate the effectiveness of adhesive primers (APs) applied to Co‐Cr and Ni‐Cr metal alloys on the bond strength of resin cements to alloys. Materials and Methods: Eight cementing systems were evaluated, consisting of four resin cements (Bistite II DC, LinkMax, Panavia F 2.0, RelyX Unicem) with or without their respective APs (Metaltite, Metal Primer II, Alloy Primer, Ceramic Primer). The two types of dental alloys (Co‐Cr, Ni‐Cr) were cast in plate specimens (10 × 5 × 1 mm³) from resin patterns. After casting, the plates were sandblasted with aluminum oxide (100 μm) and randomly divided into eight groups (n = 6). Each surface to be bonded was treated with one of eight cementing systems. Three resin cement cylinders (0.5 mm high, 0.75 mm diameter) were built on each bonded metal alloy surface, using a Tygon tubing mold. After water storage for 24 hours, specimens were subjected to micro‐shear testing. Data were statistically analyzed by two‐way ANOVA and Tukey's studentized range test. Results: The application of Metal Primer II resulted in a significantly higher bond strength for LinkMax resin cement when applied in both metal alloys. In general, the cementing systems had higher bond strengths in Co‐Cr alloy than in Ni‐Cr. Conclusions: The use of AP between alloy metal surfaces and resin cements did not increase the bond strength for most cementing systems evaluated.     

Some variables influencing the bond strength between PMMA and a silicone denture lining material

PURPOSE: The purpose of the present study was to investigate the effect of roughening the denture base surface on the tensile and shear bond strengths of a poly(dimethylsiloxane) resilient lining material (Molloplast-B) bonded to a heat-cured acrylic resin denture base material. These measured bond strengths were compared to those obtained by packing the soft lining material against poly(methyl methacrylate) (PMMA) denture base acrylic resin dough. MATERIALS AND METHODS: Three groups of 10 specimens each were constructed for both tensile and shear tests. In the first group, Molloplast-B was packed against cured PMMA denture base surface. In the second group, Molloplast-B was packed against cured PMMA denture base whose surface had been roughened with an acrylic bur. In a third group, Molloplast-B was packed against PMMA denture base acrylic resin dough. RESULTS: Molloplast-B exhibited significantly higher tensile and shear bond strengths when packed against acrylic resin dough. Roughening the denture base surface prior to the application of Molloplast-B had a statistically significant weakening effect on tensile bond strength compared with the smooth surface and the acrylic resin dough. For the shear bond strength, roughening the surface produced a nonsignificant increase compared with the smooth surface, but the bond was weaker than when packed against acrylic resin dough. CONCLUSION: Significant differences in tensile and shear bond strength were recorded between the three methods used to bond Molloplast-B to denture base material.     

An investigation into the effects of metal primer and surface topography on the tensile bond strength between cobalt chromium alloy and composite resin

This study examined the influence of surface preparation and metal primer on the tensile bond strength between cobalt chromium alloy and composite resin. The bond strength between 168 cobalt chromium alloy dumb-bells with one of three test surfaces (beaded, machined or sandblasted) to composite resin were tested. Half of each group were treated with metal primer. The weakest bond strength was produced by the unprimed machined surface, many specimens failing before testing. The metal primer increased the bond strengths of all groups tested. The greatest bond strengths were achieved with the primed beaded and sandblasted surfaces. Within the limits of the study it has been shown that the surface preparation of the cobalt-chromium alloy did influence tensile bond strengths with composite resin and Metal Primer II increased the tensile bond strengths for all groups tested. The sandblasted surface treated with Metal Primer II is recommended for the bonding of composite resin to cobalt chromium alloy.     

Enhancing wire-composite bond strength of bonded retainers with wire surface treatment

Bonded orthodontic retainers with wires embedded in composite resin are commonly used for orthodontic retention. The purpose of this study was to test, in vitro, various wire surface treatments to determine the optimal method of enhancing the wire-composite bond strength. Coaxial wires and stainless steel wires with different surface treatments were bonded to bovine enamel and then pulled along their long axes with an Instron universal testing machine. Wire surface treatments included placing a right-angle bend in the wire, microetching the wire, and treating the wire with adhesion promoters; combinations of treatments were also examined. The results demonstrated a 24-fold increase in the wire-composite bond strength of wire that was microetched (sandblasted), compared with that of untreated straight wire. The difference between the amount of force required to break the bond produced by microetching alone (246.1 +/- 46.0 MPa) and that required for the bonds produced by the retentive bend (87.8 +/- 16.3 MPa), the adhesion promoters (silane, 11.0 +/- 3.1 MPa; Metal Primer, 28.5 +/- 15.8 MPa), or for any combination of surface treatments, was statistically significant. Microetching a stainless steel wire produced a higher wire-composite bond strength than that obtained from a coaxial wire (113.5 +/- 27.5 MPa). The results of this study indicate that microetching or sandblasting a stainless steel wire significantly increases the strength of the wire-composite bond.     

The effect of length parameter on the repair strength of acrylic resin using fibers or metal wires

Fractures of acrylic resin dentures occur quite often in prosthodontic practice. Autopolymerized acrylic resin is the most popular material for denture repair; however, it is significantly weaker than the intact heat-polymerized resin. Metal strengtheners or fibers have been used to reinforce the resin. This study investigated the fracture force, deflection, and toughness of a heat-polymerized denture resin that had been repaired either with autopolymerized resin alone or with autopolymerized resin that had been reinforced with metal wire or woven glass fibers. This study also investigated how these qualities were affected when the length of the strengthener was reduced. Sixty specimens were divided into six groups of ten (depending on the repair method), together with a control group of intact heat-polymerized resin specimens. The group repaired with autopolymerized resin alone reported significantly lower (p < 0.05) fracture force, deflection at fracture, and toughness when compared to the control. When metal wire or glass fiber at full or half-length was used for reinforcement, only the original fracture force was restored; deflection and toughness remained significantly lower (p < 0.05). Based on this study, it appears that the group reinforced with full lengths of metal wire offered the best potential for reinforcement.     

不同金属处理剂对钴铬合金与基托树脂粘结强度的影响

目的:研究三种金属处理剂对钴铬合金与基托树脂粘接强度的影响。方法:制备40个钴铬合金试件随机分为4组,采用喷砂和激光对各个试件表面进行处理后,除对照组外,其它组试件分别采用Metal Primer II,Estenia Opaque Primer,Metal Base M三种金属处理剂对试件表面进行处理,后将基托树脂与金属试件进行粘接。经37℃恒温水浴24h后,测定金属试件与基托树脂间的剪切粘接强度,并进行统计分析。结果:三种金属处理剂组所获得的钴铬合金与基托树脂间的剪切粘接强度均显著高于对照组(P<0.05)。Metal Primer II组与Estenia Opaque Primer组所获得的钴铬合金与基托树脂间的剪切粘接强度显著高于Metal Base M组(P<0.05),Metal Primer II组与Estenia Opaque Primer组间差异无统计学意义(P>0.05)。结论:三种金属处理剂均能提高钴铬合金与基托树脂间的剪切粘接强度,Metal Primer II和Estenia OpaquePrimer提高钴铬合金与基托树脂间剪切强度的效果优于Metal BaseM。     

超强聚乙烯纤维增强树脂基托性能的实验研究

目的：评价在义齿基托树脂中加入超强聚乙烯纤维后的挠曲性能。方法：在义齿基托树脂中加入不同质量分数的超强聚乙烯纤维，测试其挠曲强度，与未加入纤维的基托树脂对比；同时在扫描电镜下观察其断面情况。结果：加入超强聚乙烯纤维的基托树脂的挠曲强度要高于对照组，在3．5wt％时达最大值，电镜结果显示纤维在基质中均匀分布。结论：超强聚乙烯纤维能提高义齿基托的挠曲强度。     

Effect of MMA-PMMA resin polymerization initiators on the bond strengths of adhesive primers for noble metal.

OBJECTIVES: This study was conducted to investigate the effect of MMA-PMMA resin polymerization initiators on the bond strengths of two adhesive metal primers by evaluating the shear bond strengths of resins of silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy. METHODS: Three types of MMA-PMMA resins for which the polymerization initiators were TBB, BPO-amine and CQ-amine, and two adhesive primers, Metal PrimerII and V-Primer, were used. A brass ring placed over the nonprimed or primed casting alloy disk surface was filled with each resin. The half specimens were stored in water at 37 degrees C for 24 h. In addition, another half specimens were then immersed alternately in water baths at 4 degrees C and 60 degrees C for 1 min each for 20,000 thermal cycles before shear mode testing at a crosshead speed of 0.5 mm/min. RESULTS: There were no significant differences (p > 0.05) in bond strength between the three types of resins with or without thermal cycling when Metal PrimerII was used. However, when Ag-Pd-Cu-Au alloy was primed with V-Primer, the bond strength of CQ-amine resin was significantly weaker than that of TBB resin. Metal PrimerII was more effective for enhancing the bond strength and the bond strength was not affected by thermal cycling, in contrast to V-Primer. SIGNIFICANCE: The effectiveness of Metal PrimerII to enhance the bond strength is not influenced by polymerization mode of MMA-PMMA resin, in contrast to V-Primer when the resin is bonded to Ag-Pd-Cu-Au alloy.     

Assessing the performance of a methyl methacrylate-based resin cement with self-etching primer for bonding orthodontic brackets

Questions over the usefulness of a self-etching primer with resin adhesive in the bonding of orthodontic brackets remain unsolved. The purpose of this study was to determine the effects of using Multibond, a new methyl methacrylate (MMA)-based resin cement with self-etching primer, on the shear bond strength of orthodontic brackets compared with Superbond C&B, which is a well-known MMA-based resin cement containing phosphoric acid etching. Metal or plastic brackets were bonded to etched or self-etching primed bovine teeth using Superbond C&B or Multibond. The shear bond strengths were measured after immersion in water at 37 degrees C for 24 hours. Data were analyzed by two-way analysis of variance and Scheffe's test. The surface appearances of the teeth after phosphoric acid etching or self-etching priming were observed by field-emission scanning electron microscopy (FE-SEM). Metal brackets bonded with Multibond had a significantly lower shear bond strength than metal brackets bonded with Superbond C&B. No significant differences in shear bond strength were observed between Multibond and Superbond C&B when plastic brackets were bonded to the enamel. The shear bond strength of metal brackets bonded with Multibond was comparable with that of plastic brackets bonded with Superbond C&B. Adhesive remnant index score showed a tendency of more residual resin cement remaining on the teeth when metal brackets were bonded with Multibond. FE-SEM observation revealed less dissolution of the enamel surface resulting from treatment with Multibond self-etching primer as compared with phosphoric acid. Thus, the Multibond system may be a candidate for bonding orthodontic brackets with the advantage of minimizing enamel loss.