A2 Shade Research Articles

Optical properties of supra-nano spherical filled resin composites compared to nanofilled, nano-hybrid and micro-hybrid composites.

This study aimed to evaluate and compare the optical properties of supra-nano spherical filled resin composites and the nanofilled, nano-hybrid and microhybrid composites using the Kubelka-Munk Theory. Diffuse reflectance of samples (Shade A2) was measured against white and black backgrounds, using a spectroradiometer, using a viewing booth with D65 illuminant and d/0º geometry. S and K coefficients and T were calculated using Kubelka-Munk's equations. The spectral behavior of S, K and T was similar for all dental resin composites analyzed (VAF close to 100%), even though they were, generally, statistically different (p≤0.05). The K-M T values overestimate the real value of Transmittance of the resin composites. Supra-nano spherical filled resin composites show the highest scattering and Transmittance when compared with the others materials, probably due to the shape and size of the filler. Such difference should be taken into consideration in a clinical situation to reproduce natural esthetic restorations.

Color-Matching and Blending-Effect of Universal Shade Bulk-Fill-Resin-Composite in Resin-Composite-Models and Natural Teeth.

Objectives. To assess visually color-matching and blending-effect (BE) of a universal shade bulk-fill-resin-composite placed in resin-composite-models with different shades and cavity sizes and in natural teeth (extracted and patients' teeth). Materials and Methods. Resin-composite-discs (10 mm × 1 mm) were prepared of universal shade composite and resin-composite of shades: A1, A2, A3, A3.5, and A4. Spectrophotometric-color-measurement was performed to calculate color-difference (ΔE) between the universal shade and shaded-resin-composites discs and determine their translucency-parameter (TP). Visual assessment was performed by seven normal-color-vision-observers to determine the color-matching between the universal shade and each shade, under Illuminant D65. Color-matching visual scoring (VS) values were expressed numerically (1–5): 1: mismatch/totally unacceptable, 2: Poor-Match/hardly acceptable, 3: Good-Match/acceptable, 4: Close-Match/small-difference, and 5: Exact-Match/no-color-difference. Occlusal cavities of different sizes were prepared in teeth-like resin-composite-models with shades A1, A2, A3, A3.5, and A4. The cavities were filled by the universal shade composite. The same scale was used to score color-matching between the fillings and composite-models. BE was calculated as difference in mean-visual-scores in models and that of discs. Extracted teeth with two different class I-cavity sizes as well as ten patients' lower posterior molars with occlusal caries were prepared, filled by universal shade composite, and assessed similarly. Results. In models, the universal shade composite showed close matching in the different cavity sizes and surrounding shades (4 ≤ VS < 5) (BE = 0.6–2.9 in small cavities and 0.5–2.8 in large cavities). In extracted teeth, there was good-to-close color-matching (VS = 3.7–4.4 in small cavities, BE = 2.5–3.2) (VS = 3–3.5, BE = 1.8–2.3 in large cavities). In patients' molars, the universal shade composite showed good-matching (VS = 3–3.3, BE = −0.9–2.1). Conclusions. Color-matching of universal shade resin-composite was satisfactory rather than perfect in patients' teeth.

THE EFFECT OF RELATIVE ENAMEL/DENTIN SHADE THICKNESS ON THE COLOR OUTCOME OF RESIN COMPOSITE SYSTEMS

This study was conducted to evaluate the effect of relative thickness of different resin com­posite systems using enamel and dentin shades following the natural layering concept on the final color outcome. Ninety resin composite discs were assigned according to resin composite system into three groups of 30 discs each: Ceram X Duo (S1), Filtek™ Z350 XT (S2) and Amaris® (S3). Each group was divided in to 3 subgroups (n=10) according to the relative Enamel (E) : Dentin (D) thickness in to 0.5mm E: 1.5mm D (T1), 1 E: 1 D (T2), 1.5 E:0.5 D (T3) on top of 0.5mm thick basic enamel background as a standardized layer simulating the clinical condition. A Vitapan A2 classical shade tab was used as a reference shade to which the different specimens of the three tested systems were compared. Color difference (ΔE) was measured and calculated using an electronic shade detection device which is VITA Easyshade® Advance 4.0 over a black background. UV-Shimadzu 3101 pc-spectrophotometer was also used in this study to confirm the results obtained by Easyshade Advance 4.0. The results were analyzed by analysis of variance (ANOVA)/Tukey’s post hoc test (p < 0.05) ΔE. All tested composite systems at all thickness showed significant color differ­ence (ΔE) when compared to each other with the increase of the enamel shade thickness. Although the ΔE between S2T1 and A2 shade tab was statistically significant, but clinically not perceptible (ΔE=1.780 ± 0.1814).

SHADE MATCH OF CAD/CAM LITHIUM SILICATE ALL-CERAMIC RESTORATIONS: EFFECT OF CERAMIC THICKNESS AND NON- TOOTH COLORED FOUNDATION

Statement of problem: Assessment of lithium silicate ceramics as regard to its thickness variances need evaluation with regard to color match to shade guide. Purpose: This study aimed to investigate the effect of ceramic thickness and foundation restoration on color production of lithium silicate glass- ceramics. Material and Methods: A total of 60 rectangular plate slices disks of shade A1 were prepared from CAD/ CAM generated all-ceramic materials IPS e.max CAD (EM) and Vita suprinity blocks(ZLS), with different thickness (1mm, 1.5 mm and 2mm). The color of ceramic specimens before and after bonding to foundation blocks were measured using a reflectance spectrophotometer and CIE L*a*b* (Commission Internationale de L’Eclairage) color system were used for calculation of color parameter. The collected data were statistically analyzed using two-way ANOVA and the Tukey HSD test (α=.05). results: The 2-way ANOVA showed that the ceramic material composition (P<.05), ceramic thickness (P<.05) and tooth foundation all significantly affected ΔE values (P<.05). conclusions: Reinforcement of CAD/CAM lithia silicate glass-ceramics by zirconia decreases the color match. Acceptance level between the two tested ceramic materials and thickness varied. At all evaluated thicknesses before bonding to foundation blocks, EM presented higher shade matching compared to ZLS. The effect of non tooth colored foundation can be overcome by increasing the thickness of fabricated restoration to enhance color production.

Color evaluation of low viscosity bulk-fill resin with composite resin capping layer

Purpose: The purpose of this study was to measure the color of low viscosity bulk-fill resin with a capping layer and to compare it with the color of microhybrid composite resin. Materials and Methods: A low viscosity bulk-fill resin (SDR) and microhybrid composite resin of shade A2 (A2) or A3 (A3) were fabricated to 4 mm thickness and light cured for 20 seconds. CIE L*a*b* values of the resin specimens were measured with a colorimeter. Then shade A2 and A3 microhybrid composite resin was capped over low viscosity bulk-fill resins in 2 mm thickness (SA2, SA3). The resin specimens were light cured for 20 seconds and the color was measured and analyzed (n = 10). Color differences (ΔE) between SA2 and A2, SA3 and A3 were also calculated. Results: L* value was highest in SDR followed by SA2 and SA3. L* value of A2 and A3 was the lowest. a* value was lowest in SDR followed by SA2 and SA3, and A2 and A3 was the highest. b* value was lowest in SDR followed by A2 and SA2, and A3 and SA3 was the highest. ΔE between A2 and SA2 (ΔE = 3.4), and that between A3 and SA3 (ΔE = 3.1) was lower than the perceptible color difference threshold of ΔE = 3.7. Conclusion: ΔE between low viscosity bulk-fill resin with a capping layer and microhybrid resin was lower than the perceptible color difference threshold. (J Dent Rehabil Appl Sci 2015;31(4):294-300)

LED and Halogen Light Transmission through a CAD/CAM Lithium Disilicate Glass-Ceramic.

The effect of thickness, shade and translucency of CAD/CAM lithium disilicate glass-ceramic on light transmission of light-emitting diode (LED) and quartz-tungsten-halogen units (QTH) were evaluated. Ceramic IPS e.max CAD shades A1, A2, A3, A3.5, high (HT) and low (LT) translucency were cut (1, 2, 3, 4 and 5 mm). Light sources emission spectra were determined. Light intensity incident and transmitted through each ceramic sample was measured to determine light transmission percentage (TP). Statistical analysis used a linear regression model. There was significant interaction between light source and ceramic translucency (p=0.008) and strong negative correlation (R=-0.845, p<0.001) between ceramic thickness and TP. Increasing one unit in thickness led to 3.17 reduction in TP. There was no significant difference in TP (p=0.124) between shades A1 (ß1=0) and A2 (ß1=-0.45) but significant reduction occurred for A3 (ß1=-0.83) and A3.5 (ß1=-2.18). The interaction QTH/HT provided higher TP (ß1=0) than LED/HT (ß1=-2.92), QTH/LT (ß1=-3.75) and LED/LT (ß1=-5.58). Light transmission was more effective using halogen source and high-translucency ceramics, decreased as the ceramic thickness increased and was higher for the lighter shades, A1 and A2. From the regression model (R2=0.85), an equation was obtained to estimate TP value using each variable ß1 found. A maximum TP of 25% for QTH and 20% for LED was found, suggesting that ceramic light attenuation could compromise light cured and dual cure resin cements polymerization.

Influência de diferentes cores na transmissão da luz através de diferentes compósitos

Objective: This study evaluated the influence of different composite resins shades on light transmission through the composite and the difference in percentage of the decrease in Knoop hardness between bottom and top (DKH). Methods: Two restorative composites with shades A1 and A3.5 were used (Esthet X and Filtek Z350). The irradiance of the light curing unit was measured (780 mW/cm2). Twenty-five specimens were made for each shade for both composites. Light transmission test: The irradiance of light that passed through the composite was measured (n=10). Knoop Hardness test: The DKH of the same specimen was calculated (n=10). Scanning Electron Microscopy (SEM): Five specimens from either Filtek Z350 or Esthet-X composites were observed under SEM. Results: The irradiance of light that passed through shade A1 composite was statistically higher than shade A3.5 for both composites (p=0.00001). For Esthet X, the DKH of shade A3.5 was statistically higher than for shade A1; however, there was no statistically significant difference for Filtek Z350 (p=0.03035). Representative areas showing the filler particles were photographed at 1,000x magnification. Conclusion: Different composites influenced both light transmission and DKH. Darker shades allowed lower light transmission, but could not establish a relation between dark shades and DKH.

Color Stability of Two Bulk-Fill Composite Resins

Objective: Bulk-fill composites are a group of composite resins designed for easy and fast filling of large cavities. This study aimed to assess the color stability of bulk-fill composites subjected to xenon radiation and evaluate their color change (ΔE) following polymerization.Methods: In this in vitro experimental study, 30 specimens (4mm in height and 8mm in diameter) were fabricated of x-traFil and Tetric N-Ceram universal color bulk-fill composites and A2 shade of Grandio composite (as control). Bulk-fill composites were placed in the mold in 4mm thickness according to the manufacturers’ instructions. In the control group, composite was applied to the mold in two layers each with 2mm thickness. Tetric and Grandio composites were cured for 20 seconds and x-traFil was cured for 10 seconds with a LED light-curing unit. A total of 15 specimens (five of each composite) were used for each test. For assessment of color change due to polymerization, L*, a* and b* color parameters were measured before and immediately after polymerization and also 30 days after immersion in distilled water in an incubator at 37°C and 70% humidity using a spectroradiometer. For xenon test, the specimens were subjected to color analysis after 48 hours of storage in distilled water. Next, they were subjected to xenon lamp radiation in xenon environment chamber for 122 hours at 22°C and 25% humidity and then the color parameters were measured again. The mean and standard deviation (SD) of all values were calculated. One-way and repeated measures ANOVA were used to compare ΔE and ΔL among the groups. Tukey’s HSD test was used for pairwise comparisons.Results: The value of ΔE immediately after polymerization was the lowest for Grandio (4.91) and the highest for Tetric (9.44). Thirty days after the polymerization, ΔE was the lowest in Grandio (3.07) and the highest in Tetric (9.27); ΔE showed a decreasing trend over time in all specimens. Under xenon light radiation, Grandio showed the lowest (1.50) and Tetric showed the highest ΔE (11.15).Conclusion: Following polymerization and under xenon lamp radiation, ΔE of conventional composite was less than that of bulk-fill composites.

The Effect of Luting Cement and Titanium Base on the Final Color of Zirconium Oxide Core Material.

To evaluate the effects of different types of luting cements and different colors of zirconium cores on the final color of the restoration that simulates implant-supported fixed partial dentures (FPDs) by using a titanium base on the bottom. One hundred and twenty zirconium oxide core plates (Zr-Zahn; 10 mm in width, 5 mm in length, 0.5 mm in height) were prepared in different shades (n = 20; noncolored, A2, A3, B1, C2, D2). The specimens were subdivided into two subgroups for the two types of luting cements (n = 10). The initial color measurements were made on zirconium oxide core plates using a spectrometer. To create the cement thicknesses, stretch strips with holes in the middle (5 mm in diameter, 70 μm in height) were used. The second measurement was done on the zirconium oxide core plates after the application of the resin cement (U-200, A2 Shade) or polycarboxylate cement (Lumicon). The final measurement was done after placing the titanium discs (5 mm in diameter, 3 mm in height) in the bottom. The data were analyzed with two-way ANOVA and Tukey's honestly significant differences (HSD) tests (α = 0.05). The ∆E*ab value was higher in the resin cement-applied group than in the polycarboxylate cement-applied group (p < 0.001). The highest ∆E*ab value was recorded for the zirconium oxide core-resin cement-titanium base, and the lowest was recorded for the polycarboxylate cement-zirconium oxide core (p < 0.001). The luting cement, the presence of titanium, and the color of zirconium are all important factors that determine the final shade of zirconia cores in implant-supported FPDs.

Resin–resin microtensile bond strength after different surface treatments to clean blood contamination

ObjectivesThe aim of this in vitro study was to evaluate the effect of different surface treatments on the resin–resin bond strength of a composite resin previously contaminated with blood. MethodsSixty bar-shaped specimens were fabricated. Two 2-mm-thick layers of an A3.5 shade composite (TPH3) were inserted on a silicon matrix, photoactivated and subjected to different surface treatments (n=12): (1) no contamination, control; (2) blood contamination and air drying; (3) blood contamination, rinsing with water, and air drying; (4) blood contamination, rinsing with water, air drying, and application of the bonding agent of an adhesive system (Adper Scotchbond Multi-Purpose Adhesive); and (5) blood contamination, rinsing with water, air drying, phosphoric acid etching, and application of the bonding agent of an adhesive system. Then, two 2-mm-thick layers of an A1 shade composite (TPH3) were inserted and photoactivated. After storing in water for 24h, the samples were subjected to a microtensile bond strength test in a universal testing machine. Failure modes were evaluated in a stereomicroscope. Data were analyzed using one-way ANOVA and the Tukey test (p<0.05). ResultsThere were statistically significant differences between the treatments. Blood contamination and air drying provided the lowest bond strength values; only blood contamination, rinsing with water, air drying, phosphoric acid etching, and application of the bonding agent of an adhesive system provided bond strength similar to the control. ConclusionsThe use of a full adhesive protocol involving phosphoric acid etching and the application of the bonding agent of an adhesive system provided adequate resin–resin bond strength of the composite tested.

In Vitro Evaluation and Comparison of the Translucency of Two Different All-Ceramic Systems.

The aim of this study was to evaluate and compare the translucency of two different all-ceramic systems using Vita Easyshade digital shade matching device in an in vitro model. Translucency of lithium disilicate glass-ceramic (IPS e.max Press) and zirconia all-ceramic system (Ceramill ZI) were evaluated and compared. A total of 5 square-shaped specimens with 0.5 mm thickness were fabricated from each ceramic system in A1 shade according to Vitapan Classical shade tab. Specimens were then veneered and glazed with corresponding veneer ceramics recommended by each system manufacturer and the total thickness was set to 1.5 mm. Translucency was evaluated using VITA Easyshade in two stages: before and after veneering and glazing on black and white background. Translucency parameter (TP) was calculated. A one-way ANOVA and Bonferonni tests were used when appropriate (α=0.05). Lithium disilicate glass-ceramic was significantly more translucent than the zirconia system in both stages (P<0.05). Translucency of all specimens was significantly decreased after veneering and glazing in both all-ceramic systems (P<0.05). The translucency of two different dental ceramics was significantly influenced by both material and stages of preparation. Within the limitations of the experiment, these results can be valuable and help the clinician to make appropriate esthetic decisions.

Degree of conversion of a flowable composite light-activated through ceramics of different shades and thicknesses

The cementation of thin ceramic veneers employing fluid light-activated resin-based materials is a common procedure in the dental practice. Aim: To evaluate the influence of ceramic thickness and shade on the degree of conversion (DC) of a flowable light-activated material. Methods: flowable resin composite (Tetric N-Flow - shade A1) was light-activated through ceramic discs of two shades (IPS Classic - A1 and A3) in three thicknesses (0.5, 0.7 and 1.0 mm). For control, the resin composite was light-activated without ceramic interposition. DC was evaluated by FTIR (n=5). Data were analyzed by one-way ANOVA and Dunnett's T3 test (α=0.05). Results: Statistically significant differences between groups were observed (p<0.001). Control group (without the interposition of ceramic) showed the highest mean for DC (71.9± 1.7). Considering the interposed ceramic disc groups, the highest DC values were obtained when 0.5 and 0.7 mm A1 ceramics were used (64.6±1.2 and 64.4 5.0, respectively) and the lowest DC values were obtained for 0.7 and 1 mm A3 ceramics (61.74±0.9 and 62.0±1.9, respectively). Conclusions: No flowable resin composite group with interposing ceramics reached a DC similar to the control group.

Evaluation of Discoloration Removal by Polishing Resin Composites Submitted to Staining in Different Drink Solutions

The aim of this study was to evaluate the discoloration effects of water, cola-based soft drink, coffee, and wine on resin composites used in restorative dentistry and the possibility of removing the stain with chair side manual polishing. The A2 shade of three materials was tested. Disc specimens were prepared. A spectrophotometer was used to measure the baseline CIE-Lab color parameters of each material (n=10) 24 hours after sample preparation. Samples were then immersed in a cola-based soft drink, coffee, or wine for 1 hour every day, for 30 days. For the remaining hours, the specimens were stored in distilled water. In the control group, the specimens were immersed in water for the whole period. The color differences (ΔE) were calculated after 7 and 30 days of storage, and after polishing with coarse Sof-Lex discs, and analyzed by two-way ANOVA with repeated measures and Tukey's HSD test (α=0.05). Luna presented higher ΔE values (3.41)a followed by Durafill (2.82)b and Herculite (2.24)c. For the drink solutions, ΔE values were higher for wine (4.40)a followed by coffee (2.59)b and for cola-based soft drink (2.23)c and water (2.13)c which were statistically similar. For time, ΔE values were higher for 30 days (3.97)a and then for 7 days (2.48)b and after polishing (2.04)c. The results indicate that color stability is material dependent. The types of drinks that patients consume also influence the color stability of restorative materials.

Effect of High Irradiance on Depth of Cure of a Conventional and a Bulk Fill Resin-based Composite.

This study evaluated the effect of using three commercial light curing units (LCUs) delivering a range of irradiance values, but delivering similar radiant exposures on the depth of cure of two different resin-based composites (RBCs). A conventional hybrid RBC (Z100 shade A2, 3M ESPE) or a bulk fill RBC (Tetric EvoCeram Bulk Fill shade IVA, Ivoclar Vivadent) was packed into a 10-mm deep semicircular metal mold with a 2-mm internal radius. The RBC was exposed to light from a plasma-arc-curing (PAC) light (Sapphire Plus, DenMat) for five seconds, a quartz-tungsten-halogen (QTH) light (Optilux 501, Kerr) for 40 seconds, or a light-emitting-diode (LED) light (S10, 3M ESPE) for 20 seconds and 40 seconds (control). The Knoop microhardness was then measured as soon as possible at the top surface and at three points every 0.5 mm down from the surface. For each RBC, a repeated measures analysis of variance (ANOVA) model was used to predict the Knoop hardness in a manner analogous to a standard regression model. This predicted value was used to determine at what depth the RBC reached 80% of the mean hardness achieved at the top surface with any light. The PAC light delivered an irradiance and radiant exposure of 7328 mW/cm(2) and 36.6 J/cm(2), respectively, to the RBCs; the QTH light delivered 936 mW/cm(2) and 37.4 J/cm(2) and in 20 seconds the LED light delivered 1825 mW/cm(2) and 36.5 J/cm(2). In 40 seconds, the control LED light delivered a radiant exposure of 73.0 J/cm(2). For Z100, using 80% of the maximum hardness at the top surface as the criteria for adequate curing, all light exposure conditions achieved the 2.0-mm depth of cure claimed by the manufacturer. The LED light used for 40 seconds achieved the greatest depth of cure (5.0 mm), and the PAC light used for five seconds, the least (2.5 mm). Tetric EvoCeram Bulk Fill achieved a 3.5-mm depth of cure when the broad-spectrum QTH light was used for 40 seconds delivering 37.4 J/cm(2). It required a 40-second exposure time with the narrow-spectrum LED, delivering approximately 73 J/cm(2) to reach a depth of cure of 4 mm. When delivering a similar radiant exposure of 37 J/cm(2), the QTH (40 seconds) and LED (20 seconds) units achieved a greater depth of cure than the PAC (five seconds) light. For both resins, the greatest depth of cure was achieved when the LED light was used for 40 seconds delivering 73 J/cm(2) (p<0.05).

Effect of two fluoride varnishes on the color stability of three resin-based restorative materials: an invitro study.

The aim of the present study was to evaluate the effect of two fluoride varnishes on color stability of three resin-based restorative materials. Fifty-four discs (14.5×1.7mm) were fabricated from A2 and A3 shades of a compomer (F2000), a flowable composite (Z350), and a hybrid composite (Z250), and incubated at 37°C for 48h. Dura Shield (colored) and Fluor Protector (colorless) fluoride varnishes were applied onto the discs. The coating was cleaned using a low-speed handpiece and nylon bristle brush after 24h of storage in distilled water. A second coating was then applied. A control group with no coating was immersed in distilled water and used. The CIE L*a*b* color scale was measured before the treatments and following each cleaning utilizing a spectrophotometer. The colored fluoride varnish exhibited the highest overall color change (∆E) after the first and the second cleaning procedures in all the materials. Among these, the greatest color change was observed in the A3 shade of F2000, followed by the A3 shade of Z-250. The ∆E was less than 3.3 in all groups, and was therefore clinically acceptable. Color changes following the application of fluoride varnishes were found to be clinically acceptable in all groups.

Influence of different surface treatments on microshear bond strength of repair resin composite to two CAD/CAM esthetic restorative materials

ObjectiveThe aim of this in vitro study was to evaluate which surface treatment and adhesive type might provide the most predictable microshear bond strength results of repair resin composite to lithium disilicate ceramic and a newly introduced resin nanoceramic (RNC). MethodsA total of thirty six slices were prepared out of resin nanoceramic (Lava Ultimate) and lithium disilicate (IPS e.max CAD ceramic blocks) with dimensions of 14 × 12 × 3 mm (n = 18 for each material). The slices were divided into three main groups according to surface treatment: Control group (CN) received no treatment, group (DB) roughened with diamond bur and group (CJ) silica coated with Cojet system. Each group was subdivided into two subgroups according to the type of adhesive system used for repair: Subgroup (MH): Treated with Monobond plus and Heliobond adhesive system and subgroup (SBU): treated with Single bond universal adhesive system. The adhesives were applied according to the manufacturers' instructions. Five transparent microtubules were adjusted on each substrate slice and then repair resin composite (Tetric Evoceram, shade A3) was applied and light cured (n = 15 for each subgroup). After 24 h storage in distilled water, microshear bond strength (μSBS) was measured for each specimen of tested groups. ResultsLava Ultimate RNC showed statistically significant higher μSBS compared to IPS e.max lithium disilicate ceramic. The use of diamond bur in conjunction with Monobond plus and Heliobond adhesive system showed higher μSBS compared to all tested groups. ConclusionsThe effect of different surface treatments on the μSBS to the repair resin composite is material dependent. Combination of the abrasive action of diamond bur and adhesive with separate silane treatment modalities had a synergistic influence on μSBS of the repair resin composite under the current circumstances.

The effect of pre-curing waiting time of different bonding resins on micro-tensile bond strength to dentin

ObjectiveTo evaluate the effect of 30 s waiting time of different bonding resins on their micro-tensile bond strength (μTBS) to dentin. MethodThe occlusal enamel of freshly extracted human third molars was removed to expose the middle dentin. The specimens were randomly assigned into four groups namely, Group I, two-steps-total-etch bonding system (Adper Single Bond 2/Filtek Supreme XT, ASB2/FSXT), Group II, two-steps-self-etch bonding system (Silorane System Adhesive/Filtek Silorane, SSA/FS), Group III, two-steps-self-etch bonding system (Adper SE Plus/Filtek Supreme XT, ASEP/FSXT) and Group IV, one-step-self-etch bonding system (Adper Easy One/Filtek Supreme XT, AEO/FSXT). Each group was further divided into two sub-groups according to the application time of the bonding resin (following manufacturer recommendation and 30s more than manufacturer recommendation). The corresponding resin composite (shade A3) was applied in 4 increments of 0.5–1 mm thickness each to build resin composite stump of 3–4 mm height. Each increment was light polymerized for 20 s using LED at intensity 1000 mW/cm2. The specimens were stored in deionized water at 37 °C for 24 hrs. The specimens were cut into bars according to the non-trimming technique (n = 20/group) with surface area of 0.81 mm2. The μTBS of the bars was tested using a micro-tensile device on a Universal testing machine at a crosshead speed of 1 mm/min. ResultTwo-way ANOVA revealed a statistical significant difference in the two main effects, the types of bonding systems (P = 0.0024) and the application times of bonding resins (P = 0.0005). There was no statistical significant interaction between the two main effects (P = 0.9257). The methacrylate-based two-steps-total-etch bonding system and two-steps-self-etch bonding system showed significant higher values than that of the one-step-self-etch bonding system. Conclusioni. Thirty-seconds pre-curing waiting time for bonding resins has a role in achieving higher μTBS to dentin. ii. One-step-self-etching bonding system ranked as the lowest bonding system.

Effectiveness of and tooth sensitivity with at-home bleaching in smokers: A multicenter clinical trial

BackgroundThe authors conducted a 2-center controlled clinical study to show the equivalence of at-home bleaching in smokers and nonsmokers at 1 week and 1 month and evaluate tooth sensitivity (TS). MethodsThe authors selected 60 smokers and 60 nonsmokers with central incisors of shade A2 or darker. The participants performed bleaching with 10% carbamide peroxide for 3 hours daily for 3 weeks. The authors evaluated the color by using a shade guide and a spectrophotometer before, during, and after bleaching (1 week and 1 month). Patients recorded TS by using a 0-4 scale and a visual analog scale. The authors used multivariable regression analysis to test factors associated with color change and TS (α = .05). ResultsSmokers and nonsmokers showed significant color change statistically equivalent to within ± 2.0 units at 1 week after bleaching. Overall, color shade improved by 4.1 shade guide units (95% confidence interval [CI], 3.7-4.5) and 7.8 units of color change measured with the spectrophotometer (95% CI, 7.1-8.5) at 1 month. None of the factors affected the TS risk. TS absolute risk and intensity were similar between groups (P > .05), with an overall estimate of 47% (95% CI, 38-56%). ConclusionsThe immediate effectiveness of whitening- and bleaching-related TS were not affected by smoking. Practical ImplicationsSmoking did not affect the immediate color change (1 week). Effective whitening was achieved regardless of whether the patient was a smoker. However, this equivalence was not apparent 1 month after bleaching, with smokers having slightly darker teeth.

Colour parameters and shade correspondence of CAD–CAM ceramic systems

ObjectivesTo evaluate colour differences between (1) CAD–CAM ceramic systems considering shades A1, A2 and A3 and the corresponding nominal shade of VC (Vita Classical shade guide) and (2) shades A1–A2, A2–A3 and A1, A2 and A3 within the same ceramic system. MethodsSamples of shades A1, A2 and A3 were fabricated (n=5) from CAD–CAM ceramic blocks (IPS e.max® CAD LT and HT, IPS Empress® CAD LT and HT, Paradigm™ C, and VITABLOCS® Mark II) and polished to 1.0±0.01mm in thickness. Spectral reflectance and colour coordinates were measured using a spectroradiometer inside a viewing booth using the CIE D65 illuminant and the d/0° geometry. Spectral reflectance curves were compared using VAF coefficient and were statistically analyzed using Kruskal–Wallis and the Mann–Whitney U test (α=0.05). Colour coordinates were statistically analyzed using one-way ANOVA, Tukey's test with Bonferroni correction (α=0.001). All colour differences (ΔEab* and ΔE00) were analyzed through comparisons with the PT – perceptibility and AT – acceptability thresholds for dental ceramics. ResultsΔE between ceramic systems and its corresponding shade ranged from 6.32 to 13.42 (ΔEab*) and 4.48 to 9.30 (ΔE00). ΔE between shades A1–A2, A2–A3 and A1, A2 and A3 ranged, respectively, 1.93–4.82, 1.22–5.59 and 3.63–8.84 (ΔEab*); 1.54–3.87, 1.03–3.90 and 2.95–6.51 (ΔE00). ConclusionsConsidering the corresponding nominal shade from VC, none of the ceramic systems showed colour differences below the AT. In addition, some ceramic systems showed colour differences below AT (shades A1–A2 and A2–A3) and below PT (shades A2–A3). Clinical significanceCareful adjustments should be made to the final shade of CAD–CAM ceramic restorations to reach a clinically acceptable shade match.

Fluorescence intensity of composite layering combined with surface sealant submitted to staining solutions.

The aim of this study was to evaluate the fluorescence intensity of a composite in different layering techniques combined to a surface sealant submitted to staining solutions. One surface sealant and one composite resin (shades A2-0, A2, and YE) were tested. Specimens were carried out using layering with different shades of composite, and dental blocks (dentin/enamel) were obtained of human molars. Fluorescence intensity measurement performed using a spectrofluorophotometer, before and after storage in cola, orange juice, red wine, and distilled water. Data were subjected to analysis of variance and Fisher's test (α = 0.05). Initially, only A2-O + A2 layering showed fluorescence intensity statistically similar to the natural tooth. Overall, groups sealed showed the highest fluorescence intensity compared with unsealed groups. The aging decreased the fluorescence intensity compared with initial values. Red wine showed the highest decrease on the fluorescence intensity. The fluorescence of composite restorations is dependent of the layering technique and is affected by the diet. The staining solutions decreased the fluorescence intensity, even when the composite resins were sealed. Different shades of the same composite showed distinct fluorescence values, so there should be greater standardization of this property for tooth reconstruction success by the layering technique with large tissue loss.