The relationship between monomer composition and physical properties of light-cured opaque resin.

Light-cured opaque resins were prepared using four types of monomer liquids and titanium dioxide powder. This study investigated the relationship between the monomer composition and the physical properties of light-cured opaque resin. Depth of cure, KHN, residual monomer eluent, and bond strength between the opaque resin and cobalt-chromium alloy were measured. The physical properties of triethyleneglycol dimethacrylate (TEGDMA)-based compositions were superior to those of methyl methacrylate (MMA)-based compositions. Viscosity of the opaque resin's liquid monomer was enhanced by 1,6-bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimeth ylhexane (UDMA). The TEGDMA-based light-cured opaque resins showed excellent physical properties and may be clinically acceptable in bonding prosthodontic composite to metal frameworks.     

Monomer composition and bond strength of light-cured 4-META opaque resin

A light-cured opaque resin was prepared with 4-(2-methacryloxyethoxycarbonyl) phthalic anhydride (4-META), bifunctional methacrylates, and titanium dioxide (TiO2). The relation between monomer composition and bond strength was examined with seven methacrylate monomers. Methyl methacrylate (MMA) was useful as a solvent of 4-META. However, it was not sufficiently cured by photo-initiator. The bond strength of a triethyleneglycol dimethacrylate (TEGDMA)-based composition was superior to other monomer-based compositions after repeated thermocycles. 1,6-bis(methacryloxy-2-ethoxycarbonyl-amino)-2,4,4-trimethylhex ane (UDMA) effectively provided viscosity to the composition. The prepared opaque resin consisted of 4-META/MMA-TEGDMA primer, TEGDMA-UDMA-based monomer, and titanium dioxide. This opaque resin bonded strongly to alumina-blasted cobalt-chromium alloy. The light-cured 4-META opaque resin may be useful for bonding prosthodontic composite to metal frameworks.     

The relationship between composition and properties of posterior resin composites

The effects of filler concentration and resinous components on the properties of highly filled composites were determined for prediction of the durability of the restorative resins. Resinous components of seven proprietary light-cured posterior resin composites were extracted by chloroform solvent and examined by the Fourier Transform Infrared (FTIR) method. Filler concentration was determined by the thermogravimetric method. Diametral tensile strength, Knoop hardness, and Barcol hardness tests for the composite, as well as extracted resinous matrix, were performed by standard experimental procedures. Toothbrush abrasion test of the resin composites was evaluated by a toothbrushing machine giving the equivalent of five years' toothbrushing and examined with a roughness meter. The degree of conversion of resin composites ranged from 43.5 to 73.8%. The volume fraction of filler varied from 58.2% to 74.2%. The ranges of diametral tensile strength and Knoop and Barcol hardness numbers obtained were 39.8 MPa to 60.0 MPa, 41.8 to 81.9, and 76.3 to 89.2, respectively. Significant correlations (p less than 0.01) were obtained between filler fraction and diametral tensile strength (r = 0.89, S.E. = 3.66) and between filler fraction and Knoop hardness number (r = 0.89, S.E. = 8.39). The increase in strength with increased filler concentration might be related to filler/matrix bonding.     

Evaluation of two matrix materials intended for fiber-reinforced polymers

Two matrix resins for fiber composites that remain in a fluid state during storage and handling before polymerization were evaluated. The resin mixtures, based on methyl methacrylate (MMA), were produced with two different cross-linking agent systems: 1,4-butanediol dimethacrylate and ethylene glycol dimethacrylate or diethylene glycol dimethacrylate. Water sorption, water solubility, water uptake and residual MMA monomer were determined. Thermomechanical analysis was used to determine linear dimensional changes as a function of temperature. Flexural strength and modulus as well as fracture work and the maximum stress intensity factor were determined. The results revealed similar values for both matrix polymers regarding water sorption, water solubility, water uptake, residual MMA monomer (0.5 wt% (+/- 0.03)) and coefficient of linear thermal expansion. Flexural strength for polymer B was 68.7 MPa (+/- 9.8) compared to 56.0 MPa (+/- 13.3) for polymer A when tested dry and 64 MPa (+/- 6.1) compared to (54 MPa (+/- 3.3) when water-saturated. Fracture toughness tests showed higher maximum stress intensity factor values for polymer B (0.75 +/- 0.17) MPa x m1/2 than for polymer A (0.55 +/- 0.12) MPa x m1/2. The resin binders showed an appropriate consistency while remaining in a fluid state during storage and manipulation.     

Correlation between degree of conversion, filler concentration and mechanical properties of posterior composite resins

The degree of conversion, filler concentration and mechanical properties of seven proprietary light-cured posterior composite resins were investigated. The degree of conversion of composites ranged from 43.5-73.8%. The weight fraction of filler that was obtained was in the range 66.4-85.2%. The volume fraction varied from 58.2-74.2%. The mean values of the observed compressive and diametral tensile strengths ranged from 242.3-324.7 MPa and from 39.8-62.6 MPa, respectively. The Knoop hardness numbers ranged from 41.8-81.9. Significant correlations were observed between the volume fraction of filler and the diametral tensile strength (r = 0.89), and between the volume fraction of filler and the Knoop hardness number (r = 0.89). No correlation was found between the degree of conversion and any of the mechanical properties of the composite resins tested. Because of the positive correlations between the volume fraction of filler and the diametral tensile strength, and between the volume fraction of filler and the Knoop hardness numbers, it is concluded that the filler concentration plays a prominent role in determining the properties of contemporary posterior composite resins.     

Physical properties of resins for veneer crown. (Part 1) Bending strength of thermosetting methacrylic resins (author's transl)]

The physical properties of thermosetting methacrylic resins contain a kind or more than two kinds of cross linking agents were investigated. Knoop hardness and bending strength after drying, water sorption and thermal cycling were listed in table 4 and 5. Hydrophilic resins absorbed water about 3 times as much as hydrophobic resins. The materials contain a small amount of hydrophobic cross linking agents in MMA indicate comparatively excellent properties after drying, water sorption and thermal cycling. Knoop hardness of resins generally reduced by water sorption, especially in the case of the resin contains a large amount of triethylene glycol dimethacrylate.     

Influence of polymerization initiator for base monomer on microwave curing of composite resin inlays

Microwave polymerization was used to make composite resin inlays and the effect examined of the concentration of polymerization initiator for the base monomer. The monomers used were 2,2-bis [4-(3-methacriloxy-2-hydroxypropoxy) phenyl] propane (Bis-GMA) and triethyleneglycol dimethacrylate (TEGDMA). Bis-GMA and TEGDMA were mixed in a ratio of 6:4 by weight and were separated into five groups. To each group was added benzoyl peroxide (BPO) in the ratios of 0.1, 0.3, 0.5, 0.7 and 0.9 wt% as the polymerization initiator. These were used as the base monomers. The results showed that the degree of conversion of the cured sample increased with increasing concentration of BPO from 0.1 to 0.5 wt%, however there was no significant difference at 0.5, 0.7 and 0.9 wt% (P> 0.01). Compression strength, diametral tensile strength and the Knoop hardness showed a similar tendency as the degree of conversion. No significant difference was recorded in the Knoop hardness between the top and the bottom surfaces (P> 0.01), which suggested a uniform polymerization in the cured sample. Thus, microwave polymerization would be an efficacious method for making resin inlays with the addition of BPO to the base monomer (Bis-GMA:TEGDMA, 6:4). The maximum conversion was found at a concentration of 0.5 wt%.     

Physicochemical properties of dental resins formulated with amine-free photoinitiation systems

ObjectiveTo assess the mechanical properties of two different dimethacrylate resin blends containing the photosensitizer camphorquinone (CQ) alone or in combination with one or more synergists including an amine and/or an iodonium.MethodsTwo co-monomer resin blends were formulated using Bis-GMA/TEGDMA and UDMA/TEGDMA, both at 1:1 mass ratio. Each resin blend was divided into four groups, comprising the following four photoinitiation systems: (1) CQ + 2-(dimethylamino)ethyl methacrylate (DMAEMA); (2) CQ + DMAEMA + bis(4-methyl phenyl)iodonium hexafluorophosphate (BPI); (3) CQ; and (4) CQ + BPI. Materials were evaluated for polymerisation kinetics, water sorption, solubility, flexural strength and modulus.ResultsBisGMA/TEGDMA with CQ showed minimal and insignificant degree of conversion and was not tested for water sorption/solubility and mechanical properties. The ternary system (i.e., CQ + DMAEMA + BPI), promoted the highest degree of conversion for each monomer blend. The resins containing amine had higher mechanical properties than the amine free. However, the UDMA amine free resins exhibited greater flexural strength and modulus than the corresponding amine free BisGMA resins. BisGMA/TEGDMA containing CQ + DMAEMA or CQ + BPI had significantly higher water sorption and solubility than the other groups.SignificanceResins containing amine presented better properties than the amine-free systems. The addition of iodonium salt (BPI) improved the degree of conversion of the resins, even without an amine co-initiator. The amine-free initiator system (CQ + BPI) was more effective when used with UDMA versus BisGMA based-resins respectively.     

Network structure of Bis-GMA- and UDMA-based resin systems

OBJECTIVES: The commonly used dental base monomers 2,2-bis[p-(2'-hydroxy-3'-methacryloxypropoxy)phenylene]propane (Bis-GMA) and 1,6-bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane (UDMA) require the use of a diluent monomer, such as triethylene glycol dimethacrylate (TEGDMA). The aim of this study was to measure double bond conversion of UDMA/TEGDMA and Bis-GMA/TEGDMA polymeric systems, determine the leachable portion, and analyze network formation by evaluating crosslinking and pendant double bonds. METHODS: UDMA or Bis-GMA was combined with TEGDMA in systematic increments and irradiated to form light cured polymers. Fourier transform infrared spectroscopy in the near-infrared region was used to measure double bond conversion. The leachable sol fraction was analyzed by 1H NMR. Resin composites were formulated. Flexural strength was measured by three-point bending and volumetric shrinkage was determined with a mercury dilatometer. RESULTS: The amount of base monomer greatly influenced double bond conversion, sol fraction, and crosslinking. Increasing base monomer concentration decreased double bond conversion, increased the leachable fraction, and decreased crosslinking and network formation. At mole fractions higher than 0.125, the UDMA polymers had significantly higher conversion than the Bis-GMA polymers. Bis-GMA polymers had higher leachable amounts of unreacted monomer, while UDMA mixtures had more crosslinking than the Bis-GMA mixtures. In regards to the physical properties of resin composites, increasing the base monomer improved flexural strength and decreased volumetric shrinkage. SIGNIFICANCE: This systematic study for the evaluation of conversion, leachability, crosslinking, and network structure along with physical properties, like volumetric shrinkage and flexural strength, are required for the optimization of competing desirable properties for the development of durable materials.     

Interchangeability of resin composites and bonding agents based on bis-GMA or UDMA

Recently, dentin bonding systems have been released separately from the resin composites, because the adhesive systems have been quickly improved. Since the merit of each material should be effectively utilized for each clinical case, the bonding systems and resin composites produced by different manufacturers may be combined according to the clinical purpose. The current restorative resins are basically categorized into two groups according to the main resin monomer, bis-GMA or UDMA resins. The purpose of this study was to evaluate the interchangeability between the bonding systems and resin composites, which were made by different manufacturers. Two bonding systems and five resin composites based on bis-GMA or UDMA were used in this study. The evaluation was performed by the tensile bond strength, fracture modes, and SEM observation, using the dentin surface of freshly-extracted bovine teeth. The highest bond strength (19.2 MPa) was shown by the combination of LBII sigma and AP-X. The bond strengths of nine other combinations were not statistically different (p > 0.05). There were many cohesive failures in dentin or resin composite, using all combinations. From the results, it was concluded that the interchangeability of the resin composites and bonding systems should be clinically acceptable.     

Aging studies of light cured dimethacrylate-based dental resins and a resin composite in water or ethanol/water.

OBJECTIVE: To study the aging of neat resins, prepared from bis-GMA, UDMA, D(3)MA or a mixture of bis-GMA/UDMA/D(3)MA (65/20/15 w/w/w), in water or 75% (v/v) ethanol/water 37 degrees C. Also the study of aging of Heliomolar RO, which is a radiopaque, microfilled, light cured composite, the resin matrix of which is the copolymer of bis-GMA/UDMA/D(3)MA (65/20/15 w/w/w). METHODS: Samples of neat resins and Heliomolar RO prepared by light curing were immersed in water or 75% (v/v) ethanol/water 37 degrees C, for 1, 7 or 30 days. Then the flexural and tensile strength were determined. The fractured surface of samples after the flexural tests was observed by scanning electron microscopy. RESULTS: Bis-GMA and copolymer resin did not showed any significant change in mechanical properties after immersion in water or 75% (v/v) ethanol/water 37 degrees C, for 30 days. On the contrary UDMA, D(3)MA and the composite Heliomolar RO showed a significant decrease. SIGNIFICANCE: The results obtained showed that the effect of aging in water or ethanol/water solution on mechanical properties of a light cured dimethacrylate resin depends on the chemical structure of resin. In the case of resin composite this effect depends on the filler-matrix bond strength.     

Aging effect on mechanical properties in fluid resin. (Part 2). Effect of a cross-linking agent, neopentylglycol dimethacrylate (author's transl)]

Brinell hardness and tensile strength were measured, weight decrease of specimens due to evaporation of residual monomer were also checked, and the relationship between amount of residual monomer and the mechanical properties were studied. The addition of neopentylglycol dimethacrylate (NPG) in MMA improved the mechanical properties nearly same as the heat processed resins and was effective to decrease residual monomers. Rate of polymerization must increase and the heat of polymerization raised the temperature of curing mass. Properties of the new NPG fluid resin must be improved by loss residual monomer and cross-linking structure.     

Polymer properties on resins composed of UDMA and methacrylates with the carboxyl group.

The properties of dental matrix resins have been improved by synthesis of new monomers. However, except for improvements in water-resistance, monomers with better mechanical properties than Bis-GMA and UDMA could not being synthesized. Changing the point of emphasis, we tried to improve the mechanical properties controlling the matrix resin higher structure using noncovalent bonds. We prepared a matrix resin structured by UDMA, which is a high viscosity base monomer with imino groups, and by a low viscosity acidic monomer with carboxyl groups, which permits noncovalent bonds such as hydrogen bonds or electrostatic interaction with imino groups. The maximal mechanical strength for matrix resins structured by UDMA and an acidic monomer was obtained with a composition of imino groups and carboxyl groups at a ratio of 1:1. This mechanical strength value was higher than those obtained with UDMA resin or with a Bis-GMA/TEGDMA/UDMA resin with typical composition. The improvement in mechanical properties may be due to the complex based on noncovalent bonds, between the imino groups of UDMA and the carboxyl groups of the acidic monomers.     

Establishment of a composite resin inlay technique. Part 1. The effects of various curing modes on mechanical properties of composite resins

The effects of the curing mode on mechanical properties of composite resins were examined. Four resins as inlay, and three chemically-cured and five visible light-cured restorative resins were employed. The resin specimens were prepared by three kinds of curing modes; regular setting (according to the manufacturer's instruction), subsequently added light and heat curing after regular setting, and subsequently added heat and pressure curing after regular setting. Knoop hardness, flexure strength, compressive strength, and diametral tensile strength were determined. All restorative composites were remarkably increased in knoop hardness number due to the subsequently added curing methods. Both subsequently added curing methods provided higher flexure strength to all restorative resins, and particularly in the chemically-cured resins the flexure strength provided by the subsequently added light and heat curing was higher than those by the subsequently added heat and pressure curing. Compressive strength and diametral tensile strength were slightly increased by the subsequently added curing methods with the restorative resins. No correlation was found between the filler distribution and the mechanical properties provided by the subsequently added curing methods. The subsequently added heat curing seems to be preferable for creating higher mechanical properties of resins. The IC-2 resin, experimentally designed for resin inlay, seems to be the most promising resin for inlay restoration, based on the mechanical properties, and further detailed laboratory and clinical researches are required.     

Resin bonding to enamel and dentin with one–component UDMA/HEMA adhesives

The aim of this study was to investigate the potential of UDMA/HEMA mixtures as priming and sealing components of dental adhesives. The monomers were mixed in weight ratios 100/0, 80/20, 60740, 50/50, 40/60, 20/80, 10/90, and 0/100, light activated, and dissolved in acetone at equal parts. The 60/40 UDMA/HEMA mixture served as a reference which was modified with 5, 10, 20, and 30 parts 4-MET relative to the mass of the basic monomer mixture. Shear bond strengths (24 h) of resin composite cylinders, bonded with the adhesive monomers on human enamel and dentin, were determined following a total etch technique with phosphoric acid and application of the adhesives in 2 coats on moist tooth surfaces. Average bond strength to enamel was 32 MPa with no difference between the adhesives. On dentin, significantly different bond strengths were found between UDMA (12.9 MPA) and HEMA (19.4 MPa), whereas all binary mixtures bond strengths were not significantly different (mean 16.2 MPa). Addition of 5 to 20 wt% 4-MET resulted in a significantly increased mean shear bond strength of 22.3 MPa on dentin. At 10%, a maximum mean strength of 25.4 MPa was recorded. It is concluded that mixtures of commonly used polymerizable monomers, characterized by hydrophilic moieties and dissolved in acetone, are promising candidates for effective resin bonding to enamel and dentin, provided application by the moist bonding technique.     

Application of 4-META on adhesive opaque resin. (Part 1) Adhesive strength and the stability (author's transl)]

Mechanical devices, which has been conventionally used for retaining thermo-setting acrylic resin veneers possesses disadvantage of poor marginal sealing and requires rather complicated procedure applying on the metal casting. An application of adhesive resins to overcome these disadvantages was studied. Adhesive opaque resin consisted of MMA, epoxy acrylate, TiO2 and adhesive monomer 4-META was prepared and the adhesive bonding strength between the opaque resin and Ni-Cr alloy which is for crown and bridge works, was measured. As the results, the opaque resin applied on the metal casting with proper surface treatment showed an excellent adhesive bonding strength of 260 kg/cm2. This value did not decreased even after subjected to 300 time thermal cyclings (4 degrees C and 60 degrees C). After a three months immersion in water at 37 degrees C, adhesive bonding strength decreased slightly to 190 kg/cm2.     

CC—4型BA复合树脂研究

由树脂液体、用于充填的A粉以及用于粘结的B粉组成CC—4型复合树脂。该复合树脂含有二甲基丙烯酸酯单体和二异氰酸酯改性EAM新型基质树脂(UDMA)。不含MMA;其物理机械性能优于临床常用的粉液型复合树脂;并具有良好的粘接性和储存稳定性。     

Synthesis of organic-inorganic hybrid fillers at the molecular level and their application to composite resin

The objective of this study was to synthesize a hybrid type filler composed of an organic component with inorganic component at the molecular level and to examine the properties of the filler. The composite resin was prepared by mixing synthesized filler with monomer and its physical properties were also examined. An organic-inorganic hybrid filler was synthesized by using 3-methacryloxypropyltrimethoxysilane (3-MPTS), methyltriethyoxysilane (MTES) and methanol silica sol. Firstly, poly3-methacryloxypropyltrimethoxysilane (poly3-MPTS) was synthesized by polymerization of 3-MPTS. A gelation product was obtained by graft-polymerization of poly3-MPTS with condensed organopolysiloxane after the hydrolysis of 3-MPTS, MTES and methanol silica sol. The gelation product was dried and ground to a filler. From the results of thermogravimetry-differential thermal analysis (TG-DTA), the organic-inorganic hybrid filler was found to be composed of 16.5 wt% organic component, 83.1 wt% inorganic component and 0.4 wt% residual water. A trial composite resin was prepared by mixing 55 wt% dimethacryloxyethyl 2,2,4-trimethylhexamethylene diurethane (UDMA), 15 wt% triethyleneglycol dimethacrylate (TEGDMA), 30 wt% 1-fluoro-1,3,3,5,5-penta (methacryloxyethyleneoxy) cyclotriphosphazene [P3N3(F)1 (EMA)5] as a base monomer and then 32.0 wt% of this monomer was mixed with 68.0 wt % of synthesized filler and a photo initiator, comphorquinone (CQ), was added. Compressive strength of the trial visible-light cured composite resin showed 397.0 MPa, and flexural strength and elastic modulus showed 142.5 MPa and 11.5 GPa, respectively. From the results, it was demonstrated that the present organic-inorganic hybrid filler at the molecular level can be used as a composite resin filler.     

Effects of monomer compositions on the bond strength of experimental light-cured 3-MBA resins to tooth substrates

An adhesion promoting monomer of 3-methacryloyloxybenzoic acid (3-MBA) was utilized as an ingredient of experimental dental photocurable bonding resins. Effects of the monomer compositions of the resins on the bond strength to tooth substrates were examined. The bond strength of the light-cured resin was enhanced by the addition of 3-MBA. When 3-MBA was incorporated with Bis-MPEPP2.6E, TEGDMA or their binary comonomers, the bond strengths obtained were ca. 130 kgf/cm2 for the enamel treated with an aqueous solution of 10% citric acid and 3% FeCl3 and ca. 50 kgf/cm2 for the dentin. SEM examination revealed that the acid resistant dentin layer was formed by the infiltration and polymerization in situ of the monomer of the 3-MBA bonding resin. However, bond strengths of less than 50 kgf/cm2 obtained on treated dentin could be explained by the extent of the tag formation in dentinal tubules.     

A novel reactive polymer bonding composite resin to ground tooth substrates

Methyl methacrylate (MMA)-p-styrene sulfonic acid copolymer (MS) was prepared and its adhesion to ground tooth substrates was evaluated. MS is crosslinked with Ca2+ supplied by hydroxyapatite in the smeared layer on the ground enamel and dentin, and sticks to their surface. The adhesion mechanism of MS is quite different from that of interpenetration and polymerization of monomers. The bonding strength of MMA-TBB resin to the tooth treated with an aqueous solution of MS was 11-12 MPa but that of MMA-BPO.DMPT resin was only 2.5 M Pa. Free sulfonic acids remaining in the immobilized MS disturbed the initiation of polymerization in MMA-BPO.DMPT resin. A photocurable liner, triethylene glycol dimethacrylate (TEGDMA) activated by d,l-comphorquinone (CQ), N-phenylglycine (NPG), which was polymerized in an acidic condition by irradiation, was chosen to obtain a high bond strength to the cross-linked MS on the tooth. The bond strength of TEGDMA-CQ.NPG on the tooth treated with an aqueous mixture of 10 wt% MS 7 (MMA: 70 mol%, p-styrene sulfonic acid: 30 mol%) and FeCl3 ([Fe3+]/[SO3-] = 0.28) was 10-11 MPa. The observation of the fractured surface after the tensile test and interface between precipitated MS and tooth indicated that the liner did not interpenetrate into the dentin through the immobilized MS on the tooth. These results indicated that the polymer reaction of MS with Ca2+ was important in the adhesion. In conclusion, MS is a reactive polyelectrolyte which adheres well to tooth substrates and prevents pulp irritation by hindering the penetration of the monomer.