A 2-Year Randomized Clinical Trial of Three Bonding Techniques in Non-Carious Cervical Lesions.

Background and objective: The aim of this randomized split-mouth study-controlled clinical trial was to compare the 2-year clinical performance of resin composite restorations placed at non-caries cervical lesions (NCCL) with one-step self-etch, total-etch, and selective enamel etch and self-etch adhesive techniques. Materials and methods: Thirty-two patients received three resin composite restorations each at NCCLs (Tetric EvoCeram/Ivoclar/Vivadent), bonded with a total-etch adhesive agent (ExciTE F/Ivoclar/Vivadent) and a self-etch (AdheSE One F/Ivoclar/Vivadent) without and with selective enamel etching. All restorations were evaluated by two examiners at baseline, 6-, 12-, 18-, and 24-months with FDI clinical criteria (post-operation regarding retention, caries occurrence, marginal adaptation, and marginal staining). A logistic regression analysis, a Cohen's kappa statistic, a multifactorial analysis, and X2 were performed with generalized estimating equations. Results: After 2 years, the retention rate was 86.8% for total etch, 92.26% for self-etch, and 93.63% for selective enamel etching and self-etch. No caries was detected on the restorations. Concerning marginal adaptation, the clinically perfect restorations were 26.9% for the total-etch technique, 16% for self-etch, and 25.9% for selective enamel etch and self-etch. The logistic regression model revealed that only time reduced the probability of perfect marginal adaptation. Conclusions: All three adhesive strategies provided restorations with no significant differences in the retention rate or marginal adaptation, whereas the total etch yielded better performance for marginal staining. All restorations were assessed as clinically acceptable after 2 years.

Does Sterilization Affect the Performance of Single-Step Resin Composite Polishers?

(1) Background: Single-step polishers are used extensively for resin-composite polishing. The purpose of this study was to evaluate the effect of sterilization on their performance. (2) Methods: Optrapol Next Generation/Ivoclar-Vivadent, Jazz Supreme/SS White, Optishine Brush/Kerr and Jiffy Polishing Brush/Ultradent were used for polishing a nanohybrid resin composite (IPS Empress Direct/Ivoclar-Vivadent). Polishers (n = 40) were microscopically inspected before use. After polishing, surface roughness (Sa, Sz, Sdr, Sci) and gloss were determined. Polishers were subsequently sterilized and microscopically re-examined. The process was repeated four times on new samples (n = 200). Data were analyzed using the Friedman test and Wilcoxon post hoc test, at α = 0.05. (3) Results: Optrapol's performance improved after the first sterilization for Sa and gloss, whereas it declined after the fourth sterilization for Sa. Jazz's, improved after the second sterilization for Sa and gloss and after the third sterilization for Sdr. An improvement trend was observed for Optishine after the first sterilization, but not statistically significant. Sa, Sz, and gloss declined after the fourth sterilization. Jiffy's performance was inconsistent, with a trend of performance loss after the fourth sterilization. (4) Conclusions: Performance of all polishing systems improved after the initial sterilization, but deteriorated after the fourth sterilization cycle. However, their performance can be considered clinically acceptable for a longer period of use.

Effect of decontamination procedures on marginal and internal adaptation in saliva-contaminated composite resin restorations.

The aim of the present study was to evaluate the effect of natural saliva contamination of dentin on the adaptation of composite resin restorations as well as the efficacy of various decontamination techniques. A total of 120 human molars and premolars were randomly distributed into 6 groups (n = 20). Standardized dentin cavities were prepared and restored with composite resin after 1 of 6 different surface treatments, which included a 2-step etch-and-rinse adhesive: 1, dentin etching, adhesive application following the manufacturer's instructions (control), light curing; 2, dentin etching, saliva contamination, air drying, adhesive application, light curing; 3, dentin etching, saliva contamination, water rinsing, air drying, adhesive application, light curing; 4, dentin etching, adhesive application, light curing, saliva contamination, air drying; 5, dentin etching, adhesive application, light curing, saliva contamination, water rinsing, air drying; or 6, dentin etching, adhesive application, light curing, saliva contamination, water rinsing, air drying, adhesive reapplication. The adaptation was evaluated at the top surface and at depths of 0.5 and 1.0 mm by measuring the length of the debonded margin and calculating its percentage relative to the cavity perimeter (%DM). The internal adaptation was evaluated by measuring the width of the maximum marginal gap (MMG). Inferior adaptation was observed after saliva contamination took place. Group 1 presented the most satisfactory adaptation at the top surface, whereas groups 4 and 5 had the highest %DM and greatest MMG at all surfaces (P < 0.05). The %DM and MMG values in groups 2, 3, and 6 were not significantly different from those of group 1 or each other. Saliva contamination after adhesive application (groups 4 and 5) resulted in deterioration of marginal and internal adaptation. Reapplication of the adhesive restored adaptation, as evidenced by the %DM and MMG values in group 6.

The Effect of Touch-Cure Polymerization on the Conversion and Hardness of Core Build-Up Resin Composites: A Laboratory Study.

To improve the self-curing capacity and interfacial strength with dentine of dual-cured composite materials, touch-cure activators have been introduced. The aim of the study was to evaluate the effect of these activators on the hardness and conversion of dual-cured resin composite core build-up restoratives. The materials tested were Clearfil DC Core Plus (CF) and Gradia Core (GC) with the corresponding adhesives Clearfil S3 Bond Plus (for CF) and G-Premio Bond/G-Premio DCA activator (for GC). Disk-shaped specimens (n = 6/group) were prepared for the following groups: dual-cured, self-cured and self-cured in contact with the adhesive activators at the bottom surface. After a 3-week storage period (dark/dry/37 °C) the Martens hardness (HM) and degree of conversion (DC%) were determined for the previously mentioned groups and the top surfaces of groups in contact with the adhesives. A statistical analysis was performed by a one-way ANOVA and Holm-Sidak test per material and a Pearson's correlation analysis (HM vs. DC%) at an α = 0.05. The self-cured specimens resulted in significantly lower HM and DC% values from the dual-cured group, as expected. However, in the presence of the adhesives with touch-cure activators, the conversion of the self-cured groups showed insignificant differences in HM and DC% from the dual-cured in both composite materials. The improvements on the bottom composite surfaces in contact with the adhesives did not extend to the entire specimen length. Nevertheless, improved interfacial curing may improve interfacial durability.

Efficacy of non-hydrogen peroxide mouthrinses on tooth whitening: An in vitro study.

OBJECTIVES: To evaluate the tooth whitening efficacy of non-hydrogen peroxide containing mouthrinses. METHODS: Forty incisors were randomly assigned into four groups. Four whitening mouthrinses, Oral-B 3D White Luxe/Procter & Gamble (WL), Listerine Advanced White/Johnson & Johnson (AW), Colgate Max White/Colgate (MW), and iWhite Whitening Mouthwash/Sylphar (iW), were used over a four-week period. Color changes of L*, a*, b*, ΔE*ab , and ΔE00 , were recorded by a digital spectrophotometer (Spectroshade Micro/Mht), at baseline and intermediate week-intervals. Data were statistically analyzed using repeated measures ANOVA at α = 0.05. RESULTS: The first-week mean change of L* was 0.76 and significantly different from the baseline for all solutions, without any further changes. Correspondingly, a* decreased by -0.36, while b* increased by 0.48, contributing to a color change of 1.15 ΔE*ab or 0.91 ΔE00 . No differences were found among the solutions in respect to color-parameter changes (p > 0.05). Differences among time intervals were significant (p < 0.05) and mainly observed between the baseline and the following week-measurements. There was no statistically significant time-solution interaction (p > 0.05). CONCLUSIONS: Non-hydrogen peroxide whitening mouthrinses, slightly contribute to tooth whitening, by removing superficial staining, without any further tooth bleaching effect. CLINICAL SIGNIFICANCE: Non-hydrogen peroxide containing whitening mouthrinses, despite having a quick initial action, reach their ceiling relatively soon. Their effectiveness is barely perceptible and definitely inferior to other professional tooth bleaching methods. Thus, they can only be considered as a supplementary way of keeping teeth whiter, mainly by preventing recurrent tooth discoloration.

Viscoelastic stability of resin-composites under static and dynamic loading.

OBJECTIVES: To compare the viscoelastic behavior (creep) of dental resin-composites under both static and cyclic loading in compression. METHODS: Ten cylindrical specimens (4 mm × 6 mm), divided into two subgroups (n = 5) were prepared from each of four commercial resin-composites, using a divisible stainless steel mold. They were thoroughly cured from all sides. Groups 1 and 2 were loaded statically and dynamically respectively after 1d of fabrication and dry storage. Group 1 was loaded with a constant static load of 35 MPa and it was applied for 2 h followed by 2 h of strain recovery to obtain the static creep (%) and permanent set (%) respectively. To Group 2 a cyclic load between 1 MPa and 50 MPa was applied at a frequency of 0.25 Hz for 30 min to obtain the "dynamic" creep strain (%). Regression and correlation analysis (α = 0.05) was performed to examine possible correlations between static and "dynamic" creep. RESULTS: For the resin-composite investigated, a good correlation was found between "dynamic" creep strain (%) and maximum static creep strain (%) (r = 0.92) and a strong correlation was also found between "dynamic" creep strain (%) and permanent set (%) (r = 0.97), SIGNIFICANCE: Maximum static creep was significantly higher than "dynamic" creep. A direct numerical equivalence was not expected between static and "dynamic" creep values, as in the case of "dynamic" creep, loading was cyclic and was applied for a shorter overall period. Nevertheless a strong correlation was found between the static and dynamic creep measurement.

Effect of nanofillers' size on surface properties after toothbrush abrasion.

PURPOSE: To investigate the effect of filler-particle size of experimental and commercial resin composites, undergoing toothbrush abrasion, on three surface properties: surface roughness (SR), surface gloss (G) and color stability (CS). METHODS: Four model (Ivoclar/Vivadent) and one commercial resin composite (Tokuyama) with varying filler-size from 100-1000 nm were examined. Six discs (10 mm x 2 mm) from each product were prepared and mechanically polished. The samples were then submitted to 20,000 brushing strokes in a toothbrush abrasion machine. SR parameters (Ra, Rt and RSm), G, and CS were measured before and after toothbrush abrasion. Changes in SR and G were analyzed by 2-way ANOVA, with Bonferroni post hoc test. CS values were submitted to one-way ANOVA and Bonferroni post hoc test (alpha=0.05). RESULTS: Initial G values ranged between 73-87 gloss units (GU) and were reduced after toothbrush abrasion to a range of 8-64 GU. Toothbrush abrasion resulted in significant modifications in SR and G amongst the materials tested, attributed to filler sizes. There was statistically significant difference in color (delta E* ranged from 0.38-0.88). Filler size did not affect color stability. Toothbrush abrasion resulted in rougher and matte surfaces for all materials tested. Although the individual differences in surface roughness among filler sizes were not always significant, the correlation showed a trend that larger filler sizes resulted in higher surface roughness after abrasion for the SR parameters Ra and Rt (r = 0.95; r = 0.93, respectively). RSm showed an increase after toothbrush abrasion for all resin composites, however no significant correlation was detected (r = 0.21).There was a significant correlation between G and Ra ratios (r = - 0.95).

Effect of filler size and shape on local nanoindentation modulus of resin-composites.

The aim of this study was to determine the Young's moduli (E) of a series of model dental resin-composites using nanoindentation, and to examine how E was influenced by differences in filler-size and shape. Materials with different filler-sizes and shapes but constant filler volume-fraction were investigated. Disc specimens, mounted in polystyrene resin were mechanically polished and tested with a nanoindenter. One-way ANOVA and Bonferroni test were used for the statistical analysis. Regression analysis was used to investigate the correlation between E and filler-size. E ranged from 9.31 to 12.54 GPa for spherical fillers and from 14.09 to 17.03 GPa for irregular fillers. Statistically significant differences were found among the groups. Strong quadratic correlations were observed between E and filler-size for unimodal materials with spherical and irregular fillers, but were not statistically significant. Filler-size and shape seemed to be fine-tuning factors for E.

Correlation of filler content and elastic properties of resin-composites.

OBJECTIVES: The aim was to determine the Young's modulus (E), bulk modulus (B), shear modulus (G) and Poisson's ratio (nu) of a series of composite restorative materials and to correlate them with their filler volume-fractions. METHODS: Twelve model resin-composite formulations, with systematically varied volume-fraction (Tokuyama), a flowable resin-composite (Point 4 flowable, Kerr) and two hybrid resin-composites (Filtek Supreme XT, 3M-Espe & X-tra Fil, Voco) were investigated. Twelve cylindrical specimens (5 mm x 6 mm) were prepared from each material. Six were free to expand radially under axial compressive loading, and were used to calculate the Young's modulus (E). The other six were radially constricted in a rigid stainless steel ring during loading, from which the bulk modulus (B) was calculated. Compression loading was performed at 1mm/min. The Young's and bulk moduli were determined using equations of elasticity. Poisson's ratio from nu=0.5-(E/6B) and shear modulus from G=E/2(1+nu). RESULTS: Young's moduli ranged from 2.19 to 7.15GPa, bulk moduli from 12.79 to 22.43GPa and shear moduli from 0.74 to 2.47GPa. Poisson's ratio ranged from 0.45 for the stiffer to 0.47 for the more compliant composites. Statistically significant differences (ANOVA and Bonferroni at p=0.05) were found depending on filler volume-fraction. SIGNIFICANCE: Elastic moduli varied significantly and a positive correlation existed between elastic moduli and filler volume-fraction (r2: 0.905-0.992 and 0.940-1.000 for Young's and bulk moduli, respectively).