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

Time-dependent Microhardness Gradients of Self-adhesive Resin Cements Under Dual- and Self-curing Modes

CLINICAL RELEVANCE

Acid-functional monomers in self-adhesive resin cements may decrease their self-curing polymerization ability. Light irradiation optimizes polymerization performance.

SUMMARY

Purpose: The aim of this study was to investigate Knoop microhardness of self-adhesive resin cements under dual- and self-curing modes in simulated canals for describing the polymerization behavior.Methods and Materials: Slots in lightproof silicone cylinders with one open end were filled with the following eight materials: a traditional resin cement (Duolink), a core build-up resin material (MultiCore Flow), and six self-adhesive resin cements (RelyX Unicem 2, G-Cem Automix, Maxcem, Biscem, Multilink Speed, and PermaCem 2.0). The resins were exposed to light through the open end and then stored in a lightproof box. The Knoop hardness gradient for each resin was measured after 1 hour and 120 hours. Surface readings were obtained at 1-mm intervals from 1 mm to 10 mm away from the open ends. The data were analyzed by two-way analysis of variance and the Student-Newman-Keuls test (α=0.05).Results: All the resin materials had stable Knoop hardness numbers (KHNs) at a certain depth; their KHNs in the self-curing mode did not change (p>0.05). The region above this certain depth was regarded as having undergone the dual-curing mode, and the KHN decreased gradually with depth (p<0.05). Between 1 and 120 hours postexposure, the ratio of the KHN at a 5-mm depth (self-cured) to that at a 1-mm depth (dual-cured) increased in Duolink and MultiCore Flow. However, the ratios of the six adhesive resin cements varied.Conclusion: Without light, most self-adhesive resin cements differed from traditional dual-cured resin materials in terms of Knoop micro-hardness, and they had a lesser capacity for chemical-induced curing.

Investigation of the chemical profile and cytotoxicity evaluation of organic components eluted from pit and fissure sealants

The aim of this study was to identify organic components eluted from five resin dental sealants using gas chromatography and mass spectrometry (GC/MS) after 1-day and 40-days storage and the effect of sealants on cell survival of cultured fibroblasts. Five resin materials were studied: BeautiSealant (SHOFU), Clinpro (3M/ESPE), Conseal F (SDI), Grandio Seal (VOCO) and Helioseal Clear (Ivoclar/Vivadent). The organic monomers detected were butylated hydroxytoluene (BHT), bis-phenol-A (BPA), camphoroquinone (CQ), diethylenglycoldimethacrylate (DEGDMA), 4N, N-dimethylaminobenzoic acid butylethoxyester (DMABEE), hydroxyethylmethcrylate (HEMA), hydroquinone monomethylether (MEHQ), triethylene glycol dimethacrylate (TEGDMA), tetrabutylammonium tetrafluoroborate (TBATFB), triphenylstibane (TPSb). The main monomer detected was TEGDMA, whereas BHT and DEGDMA were detected at lower concentrations. Higher monomer concentrations were detected after 40 days storage. The eluting chemical profiles of the tested materials differ qualitative and quantitative. For cytotoxicity evaluation, NIH/3T3 cells were exposed to eluates of sealants and cell viability was assessed by a quantitative technique at two observation periods. Decreased cell viability was observed. The cytotoxicity and the release of monomers from dental materials examined depends on the type of material and the observation time point. Resin-based dental materials have raised public concerns regarding possible adverse biological effects, thus it is essential to evaluate possible side effects for human health.

Effect of composition, viscosity and thickness of the opaquer on the adhesion of resin composite to titanium

OBJECTIVES

The objectives of this study were to determine the bond strength of powder-liquid and paste opaquers with different chemical compositions and viscosity to a metal substructure when they were applied in two thicknesses and to evaluate the failure modes after the bond strength test.

METHODS

Titanium plates (51 mm x 25 mm x 1mm) (n(plates)=25, N=80, n=10 per group) were conditioned with chairside silica coating (CoJet-Sand, 30 microm silica coated Al(2)O(3)) from a distance of approximately 10mm at a pressure of 2.8 bar for 15 s/cm(2) and silanized. Four types of opaquers, namely one powder-liquid (Sinfony, 3M ESPE), and three paste opaquers [(Cimara, Voco), (Monopaque, Ivoclar Vivadent), (Cavex Experimental, Cavex)] were applied either in 0.25 or 0.50 mm thicknesses using standard polyethylene molds and photo-polymerized. Resin composite (Quadrant Posterior Dense, Cavex) was applied incrementally and photo-polymerized. The specimens were thermocycled (5-55 degrees C, 6000 cycles) prior to shear bond strength test (1mm/min). Failure types were analyzed using an optical microscope and scores were given according to the modified Adhesive Remnant Index (ARI) (Score 0=no opaquer on the surface, Score 1=<1/2 covered with opaquer, Score 2=>1/2 covered with opaquer, Score 3=completely covered with opaquer).

RESULTS

While thickness did not significantly affect the bond strength results (p=0.523), type of opaquers had a significant influence on the results (p<0.01) (Univariate ANOVA, Tukey's test). Interaction terms between thickness and opaquer type were significant (p<0.01). Debonded specimens during thermocycling were considered as 0 MPa. At both 0.25 and 0.5mm thicknesses, powder-liquid based opaquer (Sinfony) showed significantly higher results (8.4+/-5.6 and 8.4+/-4.9 MPa, respectively) than those of other opaquers (1.4+/-1 to 4.3+/-3.8 MPa) (p<0.05). Only when Cimara was applied in 0.25 mm (6.9+/-4.2 MPa), there were no significant differences with Sinfony (p>0.05). The lowest results in both thicknesses were obtained from Monopaque (4+/-3.8 to 1.6+/-1 MPa, respectively) and Cavex (1.4+/-1 to 4.2+/-2.9 MPa, respectively) paste opaquers. In all opaquers, the incidence of Score 0 (30) was more frequent followed by Score 1 (27) and Score 2 (20).

SIGNIFICANCE

The use of powder-liquid opaquer in order to mask the metal in repair actions provided higher bond strength than those of the paste opaquers in both thin and thick applications. In all opaquers, the incidence of adhesive failure between the opaquer and the metal was more common implying inadequate adhesion.

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.

Evaluation of residual monomer elimination methods in three different fissure sealants in vitro

The aim of this study was to determine the concentration of residual monomers and to evaluate the effectiveness of elimination methods of residual monomers in three different fissure sealant materials (Helioseal F, Filtek Flow and EXM-510). The sealant materials were divided into four subgroups because of the treatment methods used; one control group and three experimental groups (cotton roll, rubber cup and prophylaxis paste in cup). High performance liquid chromatography was used to determine the concentrations of residual monomers. Results of the study showed that residual Bis-glycidyl dimethacrylate elution was the highest in Helioseal F and the lowest in Filtek Flow with the three methods tested. For triethleneglycol dimethacrylate, EXM-510 eluted the highest residual monomer. It was also found that although the three tested methods were insufficient for removing all of the residual monomers and rubbing with cotton rolls was more effective than other two methods.

Effects of filler composition and surface treatment on the characteristics of opaque resin composites

The effects of filler composition and surface treatment of titanium dioxide (TiO2) on the shear bond strength to noble metal and mechanical properties of opaque dental resin composites were assessed. A series of fillers for resin composites were prepared with untreated TiO2 or treated silica/alumina-coated TiO2 with silane coupling agent; these fillers were replaced with silanized SiO2 in increasing amounts. Each of various powder compositions were mixed with the liquid and applied to the surface of a silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy and light cured. A light-activated resin-veneering composite material was placed on top with the use of a brass ring mold and light cured. Specimens were stored at 37 degrees C in water for a period of 24 h. Additionally some specimens were thermocycled at 4 degrees C and 60 degrees C in water baths for 1 min each for 5000 cycles before shear mode testing was performed. Light-activated opaque resin composites containing filler with specific filler compositions of 50 wt% of untreated TiO2-50 wt% of silanized SiO2 (untreated TiO2(50)) and 40 wt% of untreated TiO2-60 wt% of silanized SiO2 (untreated TiO2(40)) showed higher shear bond strengths to the Ag-Pd-Cu-Au alloy than any other specific compositions when no thermocycling was involved. Surface treatment of TiO2 filler and TiO2(50)- and TiO2(40)-opaque resin composites prepared thereof showed significantly higher shear bond strengths than untreated TiO2(50)- and TiO2(40)-opaque resin composites when subjected to thermocycling. Surface-treated opaque resin composite had significantly higher compressive and flexural strength than untreated opaque resin composite after immersion in water for 1 month. Scanning electron microscopy of the fractured opaque resin composite surface showed an interface failure between TiO2 and the matrix resin for untreated composite, and cohesive failure within the resin for surface-treated composite. Surface-treated TiO2(50) and TiO2(40) may be clinically useful as the filler for light-activated opaque dental resin composites.

The relationship between leachability of polymerization initiator and degree of conversion of visible light-cured resin

Recently, polymerization-initiator-induced radicals have been identified as a biohazard as well as residual monomers. The present investigation was conducted to clarify the leaching behavior of the polymerization initiator and to measure the relationship between the leached amount of polymerization initiator and the degree of conversion of visible light (VL)-cured resin. Moreover, determining a suitable ratio of polymerization initiator to the base monomer according to the above relationship was carried out. The base monomer (UDMA/TEGDMA) was activated with varying concentrations of polymerization initiator (CQ/DMPT, CQ/DMAEMA) from 0.3-0.9 wt%, respectively, which were exposed to light for 40 s. Gas chromatograph mass spectrometry (GCMS) was carried out to evaluate the leached amount of polymerization initiator. The degree of conversion (DC) of the cured sample was estimated using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. As the result, it was recognized that the leachability of the polymerization initiator (CQ, DMPT, and DMAEMA) depended on the degree of conversion of the VL-cured resin. Therefore, the optimal concentration of polymerization initiator can be determined from the relation between the degree of conversion and the leached amount of polymerization initiator, which is about 0.6 wt% for CQ/DMPT (1:1 in weight) and 0.5 wt% for CQ/DMAEMA (1:1 in weight) relative to the UDMA/TEGDMA (1:1 in weight) monomer.

Properties of opaque resin composite containing coated and silanized titanium dioxide

Titanium dioxide (TiO2) is mainly used as a pigment in opaque resin composites for application to the surface of a metal framework. The hypothesis in this paper is that particles of silica/alumina (SiO2/Al2O3)-coated TiO2 treated with a silane coupling agent could bond effectively with resin monomers of opaque resin composites. Untreated TiO2 was used as the control filler. Compressive and flexural strength specimens were prepared by the heat-curing method, because these bulk specimens could not be made by the typical photo-curing method. The treated composite had significantly higher compressive and flexural strengths than the untreated composite after 6 months' immersion in water. Scanning electron microscopy of the fractured composite surfaces showed an interface failure between TiO2 and resin for the untreated composite and cohesive failure within the resin for the treated composite after 6 months' immersion. The light-activated opaque resin composite containing treated TiO2 exhibited significantly higher bond strength to a noble dental alloy after 5000 thermal cycles than that containing untreated TiO2. Thus, silanized SiO2/Al2O3-coated TiO2 appears to be clinically useful as a filler of opaque resin composites.

Effect of three adhesive primers on the bond strengths of four light-activated opaque resins to noble alloy

The effect of commercial adhesive primers for noble metals on the bond strength of light-activated opaque resin has not been determined. This study evaluated the effect of three adhesive primers on the shear bond strengths of each of the four light-activated opaque resins to silver--palladium--copper--gold (Ag--Pd--Cu--Au) alloy. The adhesive primers Alloy Primer (AP), Metal Primer II (MPII) and Metaltite(MT) were used. Four commercial light-activated opaque resins (Axis (AX), Cesead II (CEII), Dentacolor(DE) and Solidex (SO) were used to bond a light-activated resin-veneered composite to Ag--Pd--Cu--Au alloy. The specimens were stored in water at 37 degrees C for 24 h and then immersed alternatively in water baths at 4 and 60 degrees C for 1 min each for up to 20,000 thermal cycles before shear mode testing at a cross-head speed of 0.5 mm min(-1). All the primers examined improved the shear bond strength between opaque resin and Ag--Pd--Cu--Au alloy compared with non-primed specimens prior to thermal cycling. After 20,000 thermal cycles, the bond strengths of combined use of AP and DE and that of MT and each of AX, CE or DE were significantly greater than any other groups. Significant difference was observed between the bond strengths at thermal cycles 0 and 20,000, with the combined use of MT and DE. With the combination of appropriate adhesive metal primers and light-activated opaque resins, complicated surface preparations of metal frameworks of resin-veneered prostheses that are composed of casting Ag-Pd-Cu-Au alloy may be negligible.

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.

Hardness and fracture toughness of four commercial visible light-cured composite resin veneering materials

Four commercial visible light (VL)-cured composite resin veneering materials with a dentine shade were examined for their Knoop hardness and fracture toughness. Composite specimens were classified into three groups. The first group was cured by VL only, the second group was cured by VL and post-cured by VL and the third group was cured by VL and post-cured by heat. It became evident that one composite containing four-functional urethane monomer had both hardness and fracture toughness greater than those of the other three composites containing two-functional urethane monomer. The filler content (vol%) in the composite tended to be linearly proportional to both hardness and fracture toughness. Post-curing by VL and heat were proven to effectively increase both hardness and fracture toughness of once light-cured composites. These results suggest that the clinical performance (e.g. wear resistance and colour stability) of VL-cured composite resin veneering materials might be improved with the aid of post-curing.

Shear bond strength of four commercial bonding systems to cp Ti

OBJECTIVES

The purpose of this study was to evaluate the bond strength of veneering composite to commercially pure titanium (cp Ti) using several different bonding systems and a post-cure heat treatment.

METHODS

Four commercial bonding systems (Cesead, Kuraray; New Metacolor, Sun Medical; Silicaoater MD, Kulzer; Termoresin LC II, GC) were evaluated. Bonding was attempted with the opaque resin provided by each bonding system as well as with the New Metacolor opaque resin. New Metacolor resin composite was used for the veneering composite. Half of the specimens were subjected to a post-cure heat treatment at 100 degrees C for 30 min. The shear bond strengths were tested after aging the specimens in water at 37 degrees C for 1 d and also after thermocycling for 16.5 d (20,000 cycles).

RESULTS

Strong bonds, exceeding 20 MPa, were achieved with all of the bonding systems with the exception of Thermoresin LC II, which is designed for noble metals. Bond strengths were only increased by the post-cure heat treatment for the New Metacolor system. Thermocycling caused a significant reduction in bond strength for the New Metacolor adn the Thermoresin LC II systems. The use of the New Metacolor opaque resin produced increased bonding for the Silicoater MD and the opaque resin produced increased bonding for the Silicoater MD and the Cesead systems, but the effect was eliminated after thermocycling.

SIGNIFICANCE

Strong, durable bonds can be achieved between composite and sandblasted cp Ti, thus enhancing the usefulness of this metal for esthetic resin-veneered crowns and other fixed prosthetics.

Effects of coupling agents on mechanical properties of metal oxide-polymethacrylate composites

The effects of several coupling agents on the mechanical properties of metal oxide-polymethacrylate composites reinforced with titanium dioxide (TiO2), aluminium oxide (Al2O3), silica (SiO2) and zirconium dioxide (ZrO2), as fillers for opaque resins were assessed. The prepared composites consist of 24.75 wt% triethyleneglycol dimethacrylate (TEGDMA), 24.75 wt% 1,6-bis(methacryloxy-2- ethoxycarbonylamino)-2,4,4-trimethylhexane (UDMA), 0.5 wt% benzoyl peroxide (BPO) and 50 wt% metal oxide filler. Three methacrylate coupling agents--methoxydiethyleneglycol trimethacryloyl titanate, 3-trimethoxysilylpropyl methacrylate and 2,2-di(allyloxymethyl)butyl trimethacryloyl zirconate--were used for surface treatment of TiO2, SiO2 and ZrO2, respectively, while Al2O3 was treated with 4-methacryloxyethyl trimellitate anhydride (4-META). 4-META was also adopted as a coupler for TiO2, SiO2 and ZrO2 powders. Compressive and transverse strength specimens were prepared with the use of coupled or untreated filler and heat cured at 110 degrees C and 0.5 MPa for 30 min. All coupled metal oxide composites had significantly higher compressive and transverse strengths than did untreated composites after 1 month's immersion in 37 degrees C water. Scanning electron microscopy (SEM) of fractured TiO2 composite surfaces after storage in water for 1 month showed an interface failure between TiO2 filler and matrix resin for untreated TiO2 composite and cohesive failures within the resin for treated specimen. Similar results were observed with silanated SiO2 composite. However, cohesive and interface failures were seen in zirconated ZrO2- and 4-META-coupled Al2O3 composites. Thus, titanated TiO2-polymethacrylate composite may be useful as a composite pigment for opaque resin materials.