Evaluation of Color and Spectral Behavior of a Novel Flowable Resin Composite after Water Aging: An In Vitro Study.

BACKGROUND: This study aimed to evaluate the color matching, light transmittance, and reflectance characteristics of the novel flowable resin composite OCF-001 (OCF). METHODS: Fifty-four resin composite molds were made with simulated class I cavities of A2, A3, and A4 shades by filling the rubber mold interspace with Estelite Sigma Quick (ESQ), Gracefil Putty (GP) and Filtek Supremme Ultra (FSU). After applying the adhesive, three different flowable resin composites (n = 6), OCF, Gracefil LoFlo (GLF), and Supreme Ultra Flowable (SUF), were used to fill the cavities. A colorimeter was used to measure the color parameters (CIEDE2000). The color measurements were taken immediately and after 28 days. Data were analyzed using the nonparametric Kruskal-Wallis (α = 0.05) and Wilcoxon tests. The light transmittance and reflection characteristics were measured with a black background using a spectrophotometer under D65 illumination. RESULTS: The ΔE00, and ΔC of OCF was lower than other tested materials in A2 and A3 shades both immediately and after 28 days. OCF showed the highest transmittance characteristic, and a relatively stable reflectance curve in all the wavelengths. CONCLUSIONS: OCF showed better shade matching with the surrounding shades of A2 and A3, a relative uniform reflectance and higher light transmission properties.

Effect of topical fluoride application on enamel after in-office bleaching, as evaluated using a novel hardness tester and a transverse microradiography method.

This study evaluated the effect of topical fluoride application on enamel hardness after in-office bleaching. Twelve human incisors were cut along the long axis, resulting in 24 halves used in four treatment groups (n = 6 in each group): (i) untreated group (C); (ii) in-office bleaching material (B); (iii) treatment with surface reaction-type prereacted glass-ionomer varnish after in-office bleaching (B+PRG); and (iv) treatment with acidulated phosphate fluoride solution after bleaching (B+F). All specimens were subjected to pH-cycling for 4 wk. Knoop hardness was measured using a Cariotester. The decalcification of enamel was assessed quantitatively by measuring the integrated mineral loss (ΔIML). Games-Howell analysis was used to assess statistical significance of between-group differences. The Knoop hardness decreased significantly after bleaching for all groups. In treatment groups B+PRG and B+F, the Knoop hardness returned to the original unbleached values after the first pH cycle and did not change afterwards. In treatment groups C and B there was a gradual decrease in the Knoop hardness until the fourth pH cycle. The integrated mineral loss, ΔIML, was significantly higher in treatment group B+F after 2 wk than in the other treatment groups. After 4 wk, the ΔIML in treatment group B was significantly higher than in treatment group B+PRG. The application of fluoride-containing materials after bleaching results in recuperation of hardness to levels similar to those of unbleached enamel.

Prevention of artificial caries: effect of bonding agent, resin composite and topical fluoride application.

This study investigated the effect of fluoride containing resin composites and bonding agents, as well as the topical fluoride (F) application on the inhibition of artificial caries progression by using a pH-cycling model with alternating demineralizing (pH:4.5) and remineralizing (pH:7.0) solutions. Two bonding systems (F-containing bonding system [Reactmer Bond: RB] and non-F containing bonding system [Clearfil SE Bond: SE]), two resin composites, (F-containing [Reactmer Paste: RP] and non-F containing [Clearfil AP-X: AP]) were used. A combination of each bonding agent and a resin composite, RB+RP, RB+AP, SE+RP and SE+AP, was placed in 2 x 3 x 1.5-mm cavities on root dentin of extracted molars (n=96). Specimens were subjected to pH-cycling for 6 or 12 weeks. Half of all specimens were immersed in 0.05% NaF solution for 1 minute once a day as a topical F application. After the pH cycling period, a microradiograph of each specimen was taken, and the outer lesion depth of the artificial caries was measured by means of image analyzing software. The depths of the outer lesions at different periods were analyzed by one-way ANOVA and Sheffe's test at p=0.05. The combination that received F treatment showed reduced lesion depth compared to the same combination without F application. Except for the F application group of 12 weeks, there was no significant difference in lesion depth among each bonding and composite combination (p>0.05). At week 12 with the F application, RB+RP showed the shallowest lesion compared to the other combinations (p<0.05). The results indicated that the F application reduced the progression of artificial caries. Moreover, the combination of fluoride containing bonding agent and restorative material was the most effective for the inhibition of artificial caries progression based on the 12-week experimental period with topical F application.

Effect of bur-cut dentin on bond strength using two all-in-one and one two-step adhesive systems.

PURPOSE: To compare the microtensile bond strength (MTBS) of two all-in-one adhesive systems and one experimental two-step self-etching adhesive system to two types of bur-cut dentin. MATERIALS AND METHODS: Using one of the three adhesives, Xeno CF Bond (Xeno), Prompt L-Pop (PL), or the experimental two-step system ABF (ABF), resin composite was bonded to flat buccal and root dentin surfaces of eight extracted human premolars. These surfaces were produced using either regular-grit or superfine-grit diamond burs. After storage overnight in 37 degrees C water, the bonded specimens were sectioned into six or seven slices approximately 0.7 mm thick perpendicular to the bonded surface. They were then subjected to microtensile testing. The surfaces of the fractured specimens were observed microscopically to determine the failure mode. In addition, to observe the effect of conditioning, the two types of bur-cut dentin surfaces were conditioned with the adhesives, rinsed with acetone, and observed with SEM. RESULTS: When Xeno and PL were bonded to dentin cut with a regular-grit diamond bur, MTBS values were lower than to superfine bur-cut dentin, and failures occurred adhesively at the interface, whereas the experimental two-step adhesive showed no significant difference in microtensile bond strength between two differently cut surfaces. CONCLUSION: The all-in-one adhesives tested here improved bond strengths when bonded to superfine bur-cut dentin as a substrate, whereas the experimental two-step adhesive system showed unchanged bonding to both regular and superfine bur-cut dentin surfaces.

Effect of sphered particles on the firing contraction of porcelain inlay processed by cold isostatic pressing.

The effect of the sphered particles on the contraction ratio of porcelain inlay processed by the cold isostatic pressure (CIP) method was investigated. The conventional lathe-cut porcelain powder was crushed to finer particles and the secondary particles with spherical shape by adding binders of acrylic resin, wax, and polyvinyl alcohol, respectively. Porcelain powder was molded as a disc-shaped green body in a refractory model and compressed at 200 MPa by CIP. From this green compact, the sintered porcelain was obtained by only one step of firing. The porcelain discs were then used for the measurements of contraction ratio, scanning microscopic observation, biaxial flexure strength, Vickers hardness, and density. Firing contraction was decreased to about 1% in the sphered particle groups, compared with 7% of the lathe-cut porcelain powder. Although biaxial flexure strength was about 85 MPa, which is lower than the 120 MPa of the control group, and the density was significantly decreased by about 10% from the 2.4 g/cm3 of the control substance, Vickers hardness, which ranged from 531 to 537, showed no significant differences among all of the groups. The CIP method could save labor in the process of making porcelain inlays, and sphered powders could contribute significantly to a decrease in the contraction ratio in the sintering process.

Effect of depth and tubule direction on ultimate tensile strength of human coronal dentin.

The purpose of this study was to evaluate the effect of dentin depth and tubule direction on the ultimate tensile strength (UTS) of human dentin. Dentin slabs of 0.5-mm thickness were trimmed either from the mesial and distal (for specimens with the tubules parallel to the tensile force; parallel group) or from the occlusal and pulpal surfaces (perpendicular group) to reduce the cross-sectional area of the superficial, middle, and deep regions to 0.25 mm2, and subjected to microtensile testing. From SEM photomicrographs of the fractured specimens of the parallel group, the tubule density was investigated. For both parallel and perpendicular groups, superficial dentin showed a significantly higher UTS than deep dentin. The tubule density of superficial dentin was significantly lower than that of middle and deep dentin. When performing the microtensile bond test to deep dentin, it is possible that cohesive failure of dentin can occur at relatively low tensile stresses.

In vivo long-term durability of the bond to dentin using two adhesive systems.

PURPOSE: The objective of this work was to evaluate the in vivo long-term durability of bond strength and morphological appearance of interfaces between dentin and two adhesive systems. MATERIALS AND METHODS: Class V cavities were prepared on the facial surfaces of 6 intact teeth of a monkey, and restored with Unifil Bond/Unifil F and Fuji Bond LC/Clearfil AP-X. One year later, 10 other teeth were restored with the same materials and the monkey was sacrificed after 24 hours. For in vitro examination, 6 more teeth were extracted from the monkey, restored in a similar manner with the two materials, and stored in 37 degrees C water for 1 day. All specimens were subjected to the microtensile bond strength (microTBS) test. The debonded surfaces of specimens were morphologically observed with the FE-SEM. RESULTS: There were no statistically significant differences among the mean microTBS obtained for Unifil Bond/Unifil F under the three conditions (1 day and 1 year in vivo, and 1 day in vitro), and most specimens showed cohesive failure within resin composite (Unifil F). However, FE-SEM observations showed that resinous material within the hybrid layer made by Unifil Bond seemed to increase in porosity after 1 year. For Fuji Bond LC/Clearfil AP-X, pTBS at 1 day in vitro was significantly higher than that at 1 year in vivo, and bond strengths in vivo tended to decrease over time, although a statistically significant difference was not observed. From FE-SEM observations, most specimens showed cohesive failure within the adhesive (Fuji Bond LC). CONCLUSION: Bond strengths of the two adhesive systems tended to decrease for 1 year in vivo.