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At least 487 records · Page 27Linked to original sources
PubMed2003

Factors contributing to the incompatibility between simplified-step adhesives and chemically-cured or dual-cured composites. Part III. Effect of acidic resin monomers.

PURPOSE: This study examined the polymerization kinetics of acid-contaminated light- and chemically-cured resins with the use of differential scanning calorimetry. MATERIALS AND METHODS: Light-cured and chemically-cured versions of an experimental bis-GMA/TEG-DMA resin at the ratio (w:w) of 62:38 were prepared. Four acidic resin monomers with either carboxylic (DSDM and MAA) or phosphoric functional groups (MP and 2MP) were added at a 10 wt% concentration to these resins to simulate the intermixing of resin composites and unpolymerized acidic monomers along the adhesive-composite interface of simplified-step dentin adhesives. Different concentrations of the most acidic monomer 2MP (10 to 50 wt% for the light-cured resin, and 2 to 4 wt% for the chemically-cured resin) were also added to examine their contribution to reducing the extent and rate of polymerization of these resin mixtures. The effect of sodium benzene sulphinate on the polymerization of the chemically-cured resin that was contaminated with 10 wt% 2MP was also investigated. RESULTS: At 10 wt% concentration, all acidic monomers had a limited effect on the polymerization of the light-cured resin. The rate and extent of polymerization in the chemically-cured resin was substantially reduced by the carboxylic acid monomers DSDM and MAA, while polymerization was completely inhibited in the presence of the organophosphate monomers MP and 2MP. Substantial reductions in the rate and extent of polymerization of the light-cured resin occurred only in the presence of high concentrations (30 to 50 wt%) of 2MP. More acute polymerization inhibition was observed when the chemically-cured resin was contaminated with 2 to 3 wt% 2MP, with polymerization completely inhibited at 4 wt%. Addition of sodium benzene sulphinate to 2MP-contaminated chemically-cured resin revived the previously uncured resins, but their rate and extent of polymerization were still inferior to that of uncontaminated chemically-cured resin. CONCLUSION: When the influence of adhesive permeability was excluded with the use of neat, water-free resins, deactivation of the tertiary amine utilized in the chemically-cured resin by even very low concentrations of acidic resin monomers accounts for the reported incompatibility between simplified-step dentin adhesives and chemically-cured composites. The polymerization of light-cured resin is only affected by much higher concentrations of acidic resin monomers.

Acids↗
PubMed2000

The effect of triphenylbismuth on the radiopacity and performance properties of compression- and injection-molded denture resins.

PURPOSE: Methods of incorporating radiopaque triphenylbismuth into an experimental compression-molded and injection-molded heat-polymerized resins were determined. The transverse flexural properties, radiopacity, and color stability of the resins containing triphenylbismuth were then compared with a commercially available, compression-molded denture resin. MATERIALS AND METHODS: Varying levels of triphenylbismuth were added to both the monomer and polymer in heat-polymerized denture resin systems to determine the level of the additive that was necessary to achieve a radiopacity similar to 0.2 mm of copper with minimum resin porosity. Specimens were then prepared by incorporating 0% or 30% wt/wt triphenylbismuth into resins. The commercially available polymethyl methacrylate resin served as a benchmark for physical property comparison, and no additive was included during its polymerization. At 30% wt/wt triphenylbismuth, resin color stability, transverse deflection, and radiopacity were evaluated using methods described in International Standards Organization Standard 4049 and American Dental Association Specification No. 12. The transverse deflection results among the resin groups were compared with a reference resin using the Kruskal-Wallis method (alpha = 0.05). RESULTS: Incorporation of triphenylbismuth into the monomer of the injection material, resulting in 30% wt/wt in the polymerized resin, produced a level of radiopacity similar to 0.2 mm copper. Although the injection-molded resin with 30% wt/wt triphenylbismuth remained translucent, the compression-molded resin was opaque, indicating excessive air-entrapment porosity. The additive caused a faint yellowing in both types of resins, but color stability was not affected. Transverse deflection of the injection-molded resin (4.5 +/- 0.5 mm) and the injection-molded resin with triphenylbismuth (3.8 +/- 1.7 mm) was greater than that of the experimental resin (3.5 +/- 0.2 mm), which was equal to the commercial resin (3.6 +/- 0.2 mm). Triphenylbismuth at 30% wt/wt significantly reduced transverse deflection for the experimental resin (2.6 +/- 0.5 mm). CONCLUSIONS: Triphenylbismuth at a final concentration of 30% wt/wt can be added to polymethyl methacrylate injection-molded resins to provide a high level of detection on chest or abdominal radiographs without adversely affecting resin color stability and transverse deflection.

Benchmarking↗
PubMed1990

[A study on disintegration of posterior composite resins caused by long-term water immersion].

The purpose of this study is to clarify a cause of disintegration for posterior composite resins by long-term immersion in distilled water during the 3-year period. Three kinds of posterior composite resins [Bellfirm P (BP), Clearfil Posterior (CP) and Micro Jar (MJ)] and one conventional anterior composite resin [Clearfil FII (FII)] were prepared as to specimens with 20 mm diameter, and 1 mm in thickness. These specimens were immersed in distilled water at 37 +/- 1 degree C for 3 years. These specimens were observed by scanning electron microscope (SEM). The residuces in distilled water were analyzed by X-ray microdiffractometry, infrared (IR) and nuclear magnetic resonance (NMR) spectrometers. One posterior composite resin (microparticle filled resin) was eluted in water more than the other posterior and anterior composite resins with conventional fillers. In SEM observations, many air bubbles were found inside all sections of the four composite resins, because of all mixing type composite resins. The subsurface layer of all four composite resins showed signs of disintegration, but the center layer of the specimens was not disintegrated. Three cured composite resins except MJ had crystalline X-ray diffraction patterns before water immersion, but the cured MJ alone was amorphous. These peaks of crystals showed fillers of these composite resins respectively. X-ray diffraction patterns of the dissolved substances for three composite resins except BP were also crystalline, but the peaks of the crystals except CP were different from the peaks of the fillers respectively. In IR and 1H-NMR spectra of dissolved substances, an unreacted monomer could be detected in one posterior composite resin (BP), but not in the other composite resins. In 1H-NMR spectra of dissolved substances, new signals not found originally were observed in all four composite resins. Therefore, the progress of disintegration was demonstrated clearly. The dissolved substances of all four composite resins were shown as the disintegrated substances between resin matrixes and silane coupling agents. It is suggested that the disintegration of these composite resins by long-term water immersion is derived from hydrolysis.

Composite Resins↗
PubMed2003

Effect of laboratory procedures and thermocycling on the shear bond strength of resin-metal bonding systems.

STATEMENT OF PROBLEM: During fabrication or repair of removable partial dentures, resin-to-metal or resin-to-denture tooth bonds may be stressed by laboratory procedures. PURPOSE: The purpose of this in vitro study was to evaluate the effect of steam cleaning, boiling, ultrasonic cleaning (laboratory procedures), and thermocycling on shear bond strength of resin bonds to metal and denture teeth. MATERIAL AND METHODS: Resin-metal bonding systems and their specific veneer resins (Rocatec, Sinfony; Rocatec, Visio-Gem, HLC-BOND, Zeta LC and Ducera experimental veneer resin) were tested on a Co-Cr alloy (Wirobond C). The veneer resins were bonded to resin denture teeth. The experimental groups (n=7) were subjected to the following conditions: 24-hour storage of the specimens in air (group I, control group), storage in air and treated with simulated laboratory procedures (2 minutes steam cleaning, 15 minutes ultrasonic cleaning at room temperature, 1 hour boiling in water, group II), storage in air with thermocycling (5000 cycles, 5 degrees to 55 degrees C, group III), storage in air with laboratory procedures followed by thermocycling (group IV), and storage in air with thermocycling followed by laboratory procedures (group V). Shear strength tests (MPa) were performed with a universal testing machine until fracture. After shear bond testing, the failure mode of the resin-metal and resin-denture tooth bonds was assessed. Statistical analysis of the results was carried out with one-way analysis of variance and Bonferroni-Dunn's multiple comparisons post hoc analysis for test groups (alpha=0.05). RESULTS: Except for Ducera/denture tooth specimens (groups III to V: 8.7 +/- 3.4-9.1 +/- 1.7; 10.8 +/- 1.9 MPa control group), the Wirobond C and denture tooth specimens (groups III, IV and V: 1.4 +/- 0.9-11.9 +/- 2.3 MPa), showed significantly lower shear bond strengths than the corresponding control groups (7.5 +/- 2.9-21.0 +/- 3.4 MPa, P<.05). The shear bond strengths of group II of Sinfony/Wirobond C (11.6 +/- 3.3 MPa, P<.0001), Visio-Gem/Wirobond C (7.4 +/- 1.9 MPa, P<0.0001), Ducera/Wirobond C (11.8 +/- 2.9 MPa, P<.0001) and of Zeta/denture tooth (3.9 +/- 1.6 MPa, P=.0005) were significantly decreased by steam, boiling, and ultrasonic procedures compared with the corresponding control groups (21.0 +/- 3.4 MPa; 14.7 +/- 4.0 MPa; 19.1 +/- 2.3 MPa; 7.5 +/- 2.9 MPa, respectively). No significant differences were noted among groups III, IV, and V. Co-Cr specimens subjected to the Rocatec system and bonded with Sinfony and HLC BOND/Zeta specimens showed cohesive failure. Adhesive failure was observed for the experimental veneer resin on the Co-Cr specimens and for all veneer resins on the denture teeth. CONCLUSION: Simulation of laboratory procedures and thermocycling caused a significant drop in shear bond strength of metal-resin and denture tooth-resin bonds for most of the tested veneer resins. Thermocycling before shear testing had the same effect on veneer resin bond strength as the simulated laboratory procedures.

Acrylic Resins↗
PubMed1999

In vitro cytotoxicity of solid epoxy-based dental resins and their components.

OBJECTIVE: The objective of this study was to evaluate the effect of adding a spiroorthocarbonate (SOC) or a polyol on the cytotoxicity of epoxy-based dental resins. METHODS: Resins contained one of the epoxies: diglycidyl ether Bisphenol A (GY-6004); 3,4-epoxycyclohexanemethyl-3,4-epoxycyclohexane carboxylate (UVR-6105); vinyl cyclohexane dioxide (ERL-4206) or the three-epoxy mixture (Epoxy-M). The SOC was t/t-2,3,8,9-di(tetramethylene)-1,5,7,11-tetraoxaspiro[5.5]undecane (SOC). The polyols were polytetrahydrofuran (p-THF-250) and polycaprolactone triol (TONE-301). The photoinitiator (4-octylphenyl)phenyliodonium hexafluoroantimonate and camphorquinone were used for light curing the resins. Four types of resins (epoxy, SOC/epoxy, polyol/epoxy and SOC/polyol/epoxy) were evaluated for cytotoxicity as solids in the agar diffusion assay and as aqueous extracts in the MTT assay using L929 cells. RESULTS: In agar diffusion analysis, ERL-4206 and UVR-6105 resins were severely cytotoxic (+3), but the addition of SOC changed them to non-cytotoxic (-). Addition of 1-3% SOC changed Epoxy-M from mild (+) to non-cytotoxic. Adding SOC changed GY-6004 from moderate (+2) to mild (-) cytotoxicity. Generally, addition of SOC did not change cytotoxicity when added to polyol/epoxy combinations. Either polyol produced resins with reduced cytotoxicity when added to UVR-6105, but the opposite occurred when added to Epoxy-M resins. In MTT analysis, percent cell survival from 100 microliters resin extracts were statistically compared (ANOVA, p < 0.05). Epoxy-M and GY-6004 resin extracts were significantly less cytotoxic than UVR-6105 and ERL-4206 resin extracts were. Overall, the SOC component reduced the cytotoxicity of all SOC/epoxy combinations, except SOC/ERL-4206, which was significantly more cytotoxic than ERL-4206 resin extract. This may be the result of cell fixative effects observed for SOC/ERL-4206 in agar diffusion analysis. Addition of SOC produced significantly less cytotoxic SOC/polyol/Epoxy-M resins when compared to its non-SOC counterpart. The contrary result was obtained with SOC/polyol/UVR-6105 resin combinations. Consistent with agar diffusion results, adding polyol significantly decreased cytotoxicity of UVR-6105 resins. The cytotoxicity of these resins may be related to the 50% cytotoxicity (TC50) of their components as leachates. The TC50 values of the individual components were compared to BISGMA. Polyols, epoxy monomers, SOC monomer and camphorquinone were significantly (p < 0.05) less cytotoxic than BISGMA. SIGNIFICANCE: Addition of SOCs and polyols in the formulation of epoxy-based resins may contribute to development of biocompatible dental composites.

Analysis of Variance↗
PubMed2006

Preparation and in vitro release of dual-drug resinates containing equivalent content dextromethorphan and diphenhydramine.

The dual-drug resinate containing equivalent content of dextromethorphan hydrobromide (DTM) and diphenhydramine hydrochloride (DPH) was developed and characterized. To achieve this specific resinate, a procedure of simultaneous dual-drug loading using loading solutions composed of different proportions of DTM and DPH was performed and a dual-drug loading diagram was constructed to determine the equivalent drug loading solution (ELS) and also the estimated equivalent drug content (EQC). The effects of resin crosslinkage, overall drug concentration of the loading solution, and temperature during drug loading on the values of ELS and EQC were assessed. The increased overall drug concentration from 0.25 to 1.0% w/v elevated the EQC values from 18 to 35% w/w for low crosslinked resins (Dowex 50 W x 2 and x 4), and from 18 to 27% w/w for high crosslinked resin (Dowex 50 W x 8). It also changed the values of ELS from 0.50 to 0.48 for the low crosslinked resins, and 0.50 to 0.55 for the high crosslinked resin. For the high crosslinked resin, the applied heat from 35 to 65 degrees C further increased the values of EQC from 27 to 32% w/w, and changed the values of ELS in the reverse direction from 0.55 to 0.48. However, the heat did not exert significant effects on the values of EQC and ELS for the low crosslinked resins. Different batches of dual-drug resinates prepared from the determined ELS provided the resultant resinates with equivalent contents of DTM and DPH which were very close to the estimated EQC. The drug release from the resinates was performed in 0.05, 0.1, 0.2, and 0.4 N of KCl solutions. The increased ionic strength generally accelerated the release of both drugs except for 0.4 N KCl solution in which the drug release from the resinates of high crosslinkage was decreased. The congestion on the outward movement of drugs through the high crosslinked matrix might cause the delay of drug release. In conclusion, the release study demonstrated that the dual-drug resinate using a suitable crosslinked resin could be used for extended delivery of two combined drugs with the equivalent therapeutic dose.

Anti-Allergic Agents↗
PubMed1991

Bonding of plastic teeth to denture base resins.

This study evaluated the bond strengths of some new and traditional resin denture teeth and denture base resins. It included regular monolithic acrylic resin teeth (Bioform), monolithic acrylic resin-IPN teeth (Bioform IPN), and multilithic acrylic resin-composite resin teeth (Vivosit), with relatively new light-activated resin (Triad), conventional heat-cured resin (Lucitone 199), and autopolymerizing resin (Hygenic) denture base materials. The results of four-point flexure testing showed that the traditional materials gave the highest bond strength values. The autopolymerizing resin systems demonstrated interfacial failure with all resin denture teeth, showing that the common practice of treating teeth with the respective autopolymerizing monomer failed to produce adequate bond strength. Combinations of acrylic resin, IPN, and multilithic denture teeth with light-activated resins gave results calling for improvements in basic bonding system design, since interface debonding was prevalent. No failures occurred between the lap-ridge region of the multilithic tooth system and conventional heat-cured denture base resin.

Acrylic Resins↗
PubMed1997

Comparison of bond strengths of denture base resins to nickel-chromium-beryllium removable partial denture alloy.

PURPOSE: In vitro bond strengths of a traditional denture base resin (Lucitone 199) and three adhesive denture base resins (Meta-Dent, Meta-Fast with liner, and Meta-Fast without liner) to treated nickel-chromium-beryllium (Ni-Cr-Be) partial denture alloy were tested with four alloy surface pretreatments (sandblast, Met-etch, Rocatec with silane, and Rocatec without silane), with or without primer (Dentsply). The Lucitone 199 resin bonded to the nonprimed sandblasted group was the control group. The hypothesis was the use of alloy pretreatments and/or primer does not improve the bond strength of denture base resins to sandblasted Ni-Cr-Be partial denture alloy. MATERIAL AND METHODS: Primed and nonprimed bonded specimens were prepared and finished, stored in 37 degrees C distilled water for 24 hours, then debonded in tension on a testing machine. The bond strength was calculated in megapascals (MPa). Five specimens were prepared and tested for each experimental condition, both with and without primer, for a total of 160 specimens. RESULTS: For three-way analysis of variance, the main effects of resins and treatment were statistically significant (p < 0.05), but the main effect of primer was not statistically significantly (p > 0.05). Without primer, the control group had the lowest bond strength (0 MPa). The three adhesive resin groups produced significantly higher bond strengths than the Lucitone resin groups. For the treated groups, nearly all sandblasted groups produced significantly lower bond strength than the other three treated groups. Meta-Dent to Met-etch treated group had the highest bond strength (23.9 MPa). With primer, the bond strengths of the Lucitone resin groups were significantly higher than the nonprimed groups, and the Lucitone resin-primed Rocatec treated group had the highest bond strength (14.8 MPa). For the three adhesive denture base resins, nearly all primed treated groups had significantly lower bond strengths than nonprimed groups. CONCLUSIONS: Without primer, the Lucitone resin-sandblast treated group (control) had the lowest bond strength (0 MPa). The Meta-Dent denture base resin with the Met-etch treated group had the highest bond strength (23.9 MPa). With primer, the Lucitone resin-primed Rocatec-silane treated group had the highest bond strength (14.8 MPa). For the adhesive denture base resins, nearly all bond strengths of the primed treated groups were significantly lower than the values of the nonprimed groups.

Acid Etching, Dental↗
PubMed2006

Bond strengths between composite resin and auto cure glass ionomer cement using the co-cure technique.

BACKGROUND: The clinical technique for sandwich restorations prescribes etching initially set auto cure glass ionomer cement (GIC) prior to placing a layer of resin bond to develop a weak mechanical bond between composite resin and GIC. Co-curing a resin modified glass ionomer cement (RMGIC) bond and composite resin to GIC may create a chemical bond and improve the bond strengths between these two materials. METHODS: A total of 48 specimens were prepared, 12 in each of four categories. Capsulated GIC was placed into a mould and allowed to set for four minutes, etched for five seconds followed by placement of a resin bond and photo cured for five seconds over which a composite resin was puddled onto the resin bond and photo cured for 10 seconds. Capsulated GIC was placed into a mould and allowed to set for four minutes after which a sample of RMGIC (Riva LC) was prepared using twice the liquid powder ratio and painted over the surface of the set GIC using a micro brush. An increment of composite resin was added over the RMGIC and both materials were photo co-cured for 10 seconds. Capsulated GIC was placed into a mould and RMGIC (Riva LC) that had been prepared using twice the liquid powder was brushed over the GIC (prior to initial set) followed by the placement of a layer of composite resin and photo co-cured for 10 seconds. Capsulated GIC was placed into a mould and RMGIC (Fuji II LC) that had been prepared using twice the liquid powder was brushed over the GIC (prior to initial set) followed by the placement of a layer of composite resin and photo co-cured for 10 seconds. Shear testing of each of the samples was carried out and specimens were examined to determine the nature of the fracture. Selected samples were prepared for SEM investigation to observe the interfaces between the GIC and composite resin. RESULTS: There were significantly lower bond strengths (P < 0.05) amongst samples that had been etched and bonded (2.42MPa) compared to the other samples that had been co-cure bonded with RMGIC (6.48-7.05MPa). There were no significant differences amongst the bond strengths of the samples co-cure bonded with RMGIC. Specimens prepared by the 'etch and bond' technique failed adhesively and co-cured specimens failed cohesively within the GIC. SEM investigation showed chemical bonds between RMGIC bond and GIC and composite resin. CONCLUSIONS: The co-cured RMGIC bonding system eliminates several placement steps and produces a significantly stronger chemical bond between GIC and composite resin than the 'etch and bond' technique. RMGIC bond and composite resin may be co-cured to GIC either before or after initial set has occurred.

Acrylic Resins↗
PubMed2006

In-vitro investigations on suitability of light-cured resins for interocclusal splints: part I: mechanical properties.

OBJECTIVE: It was the aim of the present study to investigate the material properties of different resins and their suitability for the fabrication of occlusal and intermaxillary splints. MATERIAL AND METHOD: We subjected auto-polymerized resins (Palapress, Orthocryl, Steady-Resin M) and light-polymerized resins (Acrylight, Primosplint, Triad TranSheet Colorless and Pink) to investigation. The Targis Power light oven was used to polymerize the light-cured resins. After the auto-polymerized resins had been mixed by hand and filled into the forms, they were polymerized for 15 minutes in a high-pressure polymerization machine (Palamat) at 2 bar. The parameters examined were flexural strength, water adsorption, and polymerization shrinkage. Tests carried out according to DIN EN ISO 1567 served to determine flexural strength, flexural modulus, and water adsorption. Polymerization shrinkage was determined via the buoyancy test. RESULTS: The resins' flexural strength ranged from 60 to 101 MPa. Flexural moduli lay between 1.3 and 5.3 GPa. The water adsorption noted in light-cured resins amounted to 2.1-4.6 mass percent. Palapress and Steady-Resin displayed the lowest water adsorption with 2.0 mass percent. The light-polymerized resins revealed significantly less shrinkage (p < 0.05) than the autopolymerized resins tested in this study. CONCLUSION: Our results demonstrate that the light-cured resins-with the exception of Acrylight -easily match and even exceed the material properties of the cold-polymerized resins regarding flexural strength, flexural modulus, water adsorption and polymerization shrinkage. The light-cured resins examined thus seem suitable for use as splint material.

Absorption↗