The purpose of this study was to investigate the change in flexural strength and fracture toughness of light-cured glass ionomer cements after long-term immersion in water, and to investigate the effect of surface coatings on their properties. 2 resin-modified and 1 conventional glass ionomer cements were employed. For the flexural strength, a 25 x 2 x 2 mm stainless steel mold was used. For the fracture toughness (KtC), single edge notch specimens with dimensions 25 x 2.5 x 5 mm and a 0.5 mm notch (a/W = 0.5) were prepared in a stainless steel mold. Specimens were subjected to the 3 point bending at 0.5 mm/min after storage in 37 degrees C water for the periods of 1 h, 24 h, 1 wk, 1 month, and 6 months. The glass ionomer cements tended to exhibit an increase in mechanical properties over the 24-h period and then to maintain a constant strength. The surface protection of the resin-modified glass ionomer cement has some effect on the mechanical properties during early setting reactions, and it is desirable that the cement should be protected from direct water contact for at least 1 h after cement mixing.

Analysis of Variance↗

PubMedDate not supplied

Durability of enamel bond strength of simplified bonding systems.

The purpose of this study was to investigate the influence of thermal cycling on enamel bond strength of 2-step bonding systems. The systems used were self-etching primer systems; Imperva Fluoro Bond, Clearfil Liner Bond II, and Mac Bond II; and self-priming adhesive systems; One Step, OptiBond Solo, Prime & Bond 2.0, and Single Bond. Bovine mandibular incisors were mounted in self-curing resin and the facial surfaces were wet ground with #600 SiC paper. Enamel surfaces were treated following each manufacturer's instructions. Adhesives were applied and composites were condensed into a Teflon mold (phi 4 x 2 mm) and light cured. Bonded specimens were divided into four groups; stored in 37 degrees C water for 24 hours, followed by thermal cycling between 5 degrees C and 60 degrees C for 3,000, 10,000, and 30,000 cycles. Ten samples per test group were tested in shear mode at a crosshead speed of 1.0 mm/min. One-way ANOVAs followed by Duncan's multiple range test (p < 0.05) were done. For self-etching primer systems, a significant decrease in bond strength was observed for the thermal cycling groups. For the self-priming adhesive systems, a small decrease in bond strength was observed but no significant differences were found for thermal cycling groups. The changes in bond strength after thermal cycling were different between the bonding systems.

Acid Etching, Dental↗

PubMedDate not supplied

Adhesion of single application bonding systems to bovine enamel and dentin.

Single application bonding systems have recently been developed in an effort to simplify and shorten bonding procedures. This study compared their bonding ability to enamel and dentin. Four commercial single application systems, Reactmer Bond (Shofu Inc), One-Up Bond F (Tokuyama Co), AQ Bond (Sun Medical Co, Japan) and Prompt L-Pop (ESPE, Germany) were used. F2000 compomer (3M Dental Products, St Paul, MN 55144, USA) was used as a control material. Bovine mandibular incisors were mounted in self-curing resin and the facial surfaces were ground to expose either enamel or dentin. Restoratives were bonded after adhesive application to tooth surface according to the manufacturer's instructions. Fifteen samples per test group were stored in 37degrees C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/minute. Statistical analysis was accomplished with a one-way ANOVA followed by the Duncan test (p<0.05) were done. The enamel bond strengths of the newly developed one step bonding systems were not significantly different from the compomer except for Prompt L-Pop, which showed the highest value. The dentin bond strengths of single application bonding systems did not differ from the compomer. The results of this study suggest that the adhesive properties of the newly developed single application bonding systems were comparable to a compomer restorative.

Adhesiveness↗

PubMedDate not supplied

Factors influencing bond strengths between unetched glass ionomers and resins.

The use of glass-ionomer cements as a base beneath composite resins has become a popular restorative procedure often referred to as the "sandwich technique." Originally etching of the glass-ionomer surface was recommended to help create the necessary bond between glass-ionomer cement and composite resin. This study investigated the bond strength of various composite resins and their bond agents to unetched glass ionomer. The pH of the bond agents was measured and related as bond strength. The influence of time elapsed between mixing the glass-ionomer cement and placement of the bond agent was also studied. Bond strengths varied from 65.5 kg/cm2 for G-C Dentin Cement with Pyrofil Light Bond A to 3.2 kg/cm2 for G-C Dentin Cement with Bis-Fil-M. The pH range was from 2.28 for Pyrofil Light Bond to 7.62 for Durafill Bond. Low correlation coefficients between bond strength values and pH indicated only limited relationship between the two. The bond strength decreased as the time lapse between the end of the mix and application of the bond agent increased.

Composite Resins↗

PubMedDate not supplied

Effect of die material hue and value on polymerization of indirect resin inlays.

This study investigated the effects of hue and value of mold materials on the polymerization of resin composite inlays fabricated by an indirect process. Three colors of molds were used, and 10 specimens each of three resin composite materials were light polymerized on each of the die materials for each test. The specimens were postirradiation heat polymerized. Compressive strength, flexural strength, Knoop hardness, and bond strength to enamel and dentin were measured. Although differences in properties between specimens polymerized on different die materials were not always significant, the values obtained from the white mold were highest in all tests followed by those obtained on the gray and then the black molds. Correlations (r2) between lightness or value and compressive and flexural strength, hardness, and bond to enamel and dentin values were greater than 0.90. Die color and value appear to be important factors influencing the properties of indirect resin composite inlays even though they are heat polymerized after light activation.

Analysis of Variance↗

PubMedDate not supplied

Influence of irradiation sequence on dentin bond of resin inlays.

The relationship between the order in which a dual-cured resin cement is light activated and the bond strength of resin inlay materials to dentin was examined. Also evaluated was the setting time with various irradiation sequences. Lite-Fil CR/Imperva Bond (Shofu) and Clearfil CR/CR Cement (Kuraray) were employed. Ten specimens, 4 mm in diameter by 4 mm deep, were made with each material for each condition and bonded to bovine dentin with the respective bonding agent and cement. Order of light activation was: 1) no light activation; 2) premix activation of only the liquid prior to mix, 3 seconds for Lite-Fil and 25 seconds for Clearfil; 3) postplacement activation, 30 seconds for Lite-Fil and 40 seconds for Clearfil; and 4) premix and postplacement activation, 3 seconds and 30 seconds for Lite-Fil and 25 seconds and 40 seconds for Clearfil. Samples were stored in water for 24 hours and shear strength tested. The setting time with no activation and premix activation was measured according to the ISO #7489 standards. Bond strengths (MPa) were 1) 4.41, 2) 13.07, 3) 6.34, and 4) 14.81 for Lite-Fil, and 1) 0.37, 2) 2.44, 3) 0.52, and 4) 2.51 for Clearfil. No light activation or only postplacement activation resulted in lower bond strengths with a 4.0 mm-thick specimen. The setting time of the cement mix with premix activation was shorter than with no activation. Light activation of these dual-cure cements is essential. Premix activation of only the liquid resulted in bond strengths similar to those obtained with combined pre- and postplacement activating.

Analysis of Variance↗

PubMedDate not supplied

Influence of dentin primer application methods on dentin bond strength.

This study was carried out to determine the influence of dentin primer application methods on bond strength to human dentin. Two dentin bonding restorative systems, Imperva Bond/Lite-Fil II A (Shofu) and Scotchbond Multi-Purpose/Z-100 (3M) were employed. Human molars were mounted in self-cured resin and the buccal surfaces were prepared with #600-grit SiC paper. These surfaces were then conditioned according to each manufacturer's instructions. Two experiments were designed: (1) effect of the primer application procedures (inactive and active application), and (2) effect of the air drying time (0, 1, 5, 10, 20, and 30 seconds). The adhesives were applied and resin composites were bonded to the teeth. Ten samples per test group were stored in 37 degrees C deionized water for 24 hours, and shear tested with a circular knife edge at a crosshead speed of 1.0 mm/minute. A one-way ANOVA followed by the Newman-Keuls multiple comparison at P < 0.05 was done. For both restorative systems, the bond strengths for active application were higher than those for inactive application, but there was no significant difference between the two mean values. According to the air drying time, there appeared to be an optimal range of drying times, longer for Imperva Bond (10-30 seconds) than for Scotchbond MP (1-5 seconds). The data suggest that the bond strengths of employed dentin bonding systems were greatly influenced by the methods of the dentin primer application.

Air↗

PubMedDate not supplied

Evaluation of curing units used in private dental offices.

It is well known that numerous factors influence the light output of curing units, but many dentists are unaware that the output of their curing lights are inadequate. This study was conducted to evaluate the light intensity of visible-light curing units in private dental offices and to assess their curing efficiency by measuring compressive strength of a light-cured resin. Also, in order to determine the maximum light intensity of the curing units, lamps, filters, and fiber optic bundles were replaced by new ones and curing efficiency remeasured. Light intensity was measured by employing a Quantum Radiometer LI-189 at a wavelength of 470 +/- 40 nm using a bandpass filter. Compressive strength of a light-cured resin using the light units was measured employing an Instron Testing Machine at a crosshead speed of 1.0 mm/min. From the evaluation of 105 light units, the light intensity ranged from 28 to 1368 W/m2 (0 approximately 500 W/m2; 41.9%, 500 approximately 1000 W/ m2; 45.7%, 1000 approximately 1500 W/m2; 12.4%). Light intensity of the light unit in private offices decreased 15.9 approximately 82.1% compared to brand-new units. Reduction of light intensity impaired compressive strength of the light-cured resin to varying degrees (148.3 approximately 279.9 MPa) compared with the highest value (317 MPa) obtained from brand-new light units. The replacement of the parts increased the light intensity, with maximum increases of 36.0% for lamps, 157.7% for filters, 46.2% for fiber optics, and 322.7% for all three parts. The results of this study indicated that the light intensities of the curing units used in private practice were lower than expected.

Composite Resins↗

PubMedDate not supplied

Resin-modified glass ionomers: dentin bond strength versus time.

Most dentin bond strength tests of resin-modified glass-ionomer cements have been conducted after at least 24 hours' storage in water. In a clinical situation, debonding might occur soon after the restoration was placed if subjected to stress. The purpose of this study was to investigate the rate of development of shear bond strength of resin-modified glass-ionomer cements, two Type IIs of which, Fuji II LC and Vitremer, were used. A conventional glass-ionomer cement, Fuji II, and a resin composite, Herculite XRV/OptiBond system, were also employed as controls. Bovine incisors were mounted in self-curing resin, and the facial surfaces wet ground with 600-grit SiC paper to expose dentin. Materials were condensed into a vinyl mold and bonded following the manufacturers' instructions. The shear bond strengths of 10 specimens per group were measured at a crosshead speed of 1.0 mm/minute after 1, 5, 10, 30, and 60 minutes' and 2, 5, and 24 hours' storage in water at 37 degrees C. One-way ANOVAs followed by the Dunnet test (P < 0.05) were used to test for significant differences between the mean bond strength at 1 minute and each of the other test periods. The test period when there was a significant increase in bond strength was defined as the "initial increasing time." The dentin bond strengths of all the materials tested increased with prolonged storage time. The initial increasing times were 10 minutes for Fuji II LC and OptiBond, 20 minutes for Fuji II, and 60 minutes for Vitremer. The differences in the initial increasing time might have clinical implications if the restoration is subjected to significant stress immediately after placement.

Analysis of Variance↗