Adhesion and sealing of different universal adhesive systems associated with bulk-fill resins after using endodontic irrigation solutions: An in vitro study.

This study aimed to evaluate the interface of universal adhesive (UA) with bulk-fill resin (BF) and dentin, after endodontic irrigation. The pulp chamber of 96 molars was irrigated with chlorhexidine 2% (CHX) or sodium hypochlorite 5.25% (NaOCl) and restored according to three restorative protocols. Microtensile bond strength (µTBS) and nanoleakage tests were performed after 24 h of thermocycling. Kruskal Wallis, Mann-Whitney and Wilcoxon were performed (p < 0.05). Comparing restorative systems, a difference was found only when irrigated with CHX after 24 h. CHX provided higher µTBS than NaOCl after 24 h for two restorative protocols; after thermocycling, NaOCl provided the greatest µTBS than CHX for one group. Decreased µTBS was observed for all restorative systems when CHX was used after thermocycling. NaOCl demonstrated the highest nanoleakage. The composition of UA influenced the immediate adhesion and sealing to BF when CHX was used; ageing has a deteriorating effect on adhesion and sealing for all restorative systems.

Direct dentin bleaching: Would it be possible?

This study aims to evaluate in vitro the effect of violet LED when applied directly to dentin tissue pigmented by different substances. We analyzed the chromatic alteration, the bleaching effect and the temperature variation. Hence, 60 bovine dentin tissue discs were divided into five groups: NNatural Pigmentation; T-Black Tea; C-Soluble Coffee; W-Red Wine; B-Equine Blood. Individualized pigmentation protocols were performed and all groups reached the same chromatic change value. Subsequently, we simultaneously performed a bleaching session and measured temperature variation using a K-type thermocouple device. Data on chromatic change (∆E, ∆E00, ∆a, ∆b and ∆L), whitening effect (WID) and temperature variation were subjected to one-way Anova and Tukey's post-test at a 5% significance level. The C group showed the most relevant chromatic change values, similar to the N group, responding positively to the treatment. However, the B group differed from the control group, which showed difficulty to respond to the treatment. Regarding the whitening index, only the W group showed lower results than the others. The B group showed the greatest temperature changes. We conclude that the violet LED offered chromatic change, which generated a bleaching effect. Pigmentations with red wine and blood showed the greatest difficulty to respond to treatment, also promoting a higher temperature rise in teeth pigmented with blood.

Mechanical Properties of Experimental Composites with Different Photoinitiator.

OBJECTIVE: The effect of different photoinitiators on mechanical properties of experimental composites was evaluated. MATERIALS AND METHODS: Resin composites were formulated by using a blend of bisphenol A-glycidyl and triethylene glycol (50/50 wt%) dimethacrylate monomers, and 65 wt% of barium aluminium silicate and silica filler particles. Photoinitiators used were 0.2% camphorquinone (CQ) and 0.8% co-initiator (DMAEMA); 0.2% phenyl-propanedione and 0.8% DMAEMA; 0.1% CQ + 0.1% phenyl propanedione and 0.8% DMAEMA; 0.42% mono(acyl)phosphine oxide (MAPO); and 0.5% bis(acyl)phosphine oxide (BAPO). Specimens (n = 10) were light cured by using a multiple-emission peak light-emitting diode for 20 seconds at 1,200 mW/cm2 of irradiance and Knoop hardness and plasticization, depth of cure, flexural strength, and elastic modulus were evaluated. Data were statiscally analyzed at significance level of α = 5%. RESULTS: Experimental composites containing MAPO and BAPO photoinitiators showed the highest values of flexural strength, elastic modulus, top surface hardness, and lower hardness reduction caused by alcohol compared with CQ. Composites containing CQ and PPD showed similar results, except for depth of cure and hardness of bottom surface. CONCLUSION: BAPO and MAPO showed higher flexural strength, elastic modulus, hardness on top surface, and lower polymer plasticization to CQ.

Influence of thickness and translucency of lithium disilicate ceramic on degree of conversion of resinous materials.

BACKGROUND: In this study was assessed the degree of conversion (DC) of amine-free resin cements light cured through lithium disilicate-reinforced ceramics at different thicknesses and translucency. MATERIAL AND METHODS: Specimens were divided into 21 groups (n = 5) according to luting agent used: Variolink Esthetic LC (Light shade), RelyX Ultimate (A1 shade), and Filtek Z350 XT Flow (A1 shade); the ceramic translucency: low (LT) and high (HT); and the ceramic thickness: no ceramic (control), 0.5 mm, 1 mm, and 2 mm. A Teflon mold with (5 x 5 x 0.5 mm) was used to standardize the cement and over it the ceramic block from each group was placed. Set was cured using a polywave LED light (1200 mW/cm2 - Bluephase G2) for 40 s. FTIR spectra of uncured and cured materials was obtained and DC calculated from the height of the peaks 1610 and 1640 cm-1. Data were submitted to ANOVA followed by Tukey's test (α = 0.05). RESULTS: There was a significant difference for luting agents (p< 0.0001) and translucency (p = 0.025), but not for thickness (p = 0.73). Dual amine-free RelyX Ultimate showed the lowest DC values and higher translucency promoted higher DC. CONCLUSIONS: Dual amine-free cement showed the lowest monomer conversion and higher translucency ceramics promoted a higher DC. Key words:Ceramic, degree of conversion, resin cement, thickness, translucency.

Effect of bleaching agents on hardness, surface roughness and color parameters of dental enamel.

BACKGROUND: In this study was evaluated the effect of carbamide peroxide (CP) and hydrogen peroxide (HP) in different concentrations on hardness, roughness, and color parameters (color change - ΔE, lightness - ΔL, and yellow-blue axis - Δb) of bovine teeth. MATERIAL AND METHODS: Fifty square dental blocks (7 x 7 x 2 mm) were submitted to initial readings of Knoop hardness, surface roughness (Ra), and color parameters. Specimens were divided into 5 groups (n = 10): control group was kept in artificial saliva during the experimental period; CP 20% was bleached for 2 h daily for 14 days, HP 9.5% was bleached for 30 min daily for 14 days, HP 38% the bleaching gel was applied for 15 min, gel was removed and it was reapplied for two more times, the bleaching session was repeated for another 2 times every 7 days, totaling three sessions, and in CP 45% three sessions of 30 min each were performed of 7 in 7 days. All groups after the bleaching procedures had the bleaching gel removed, washed, and kept in artificial saliva. At the end of bleaching treatment, the hardness, roughness, and color parameters (ΔE, ΔL, and Δb) were re-evaluated. Data were analyzed by ANOVA, Tukey, and Dunnett tests (α = 0.05). RESULTS: Bleaching promoted a reduction in hardness, the CP 45% showed the lowest hardness and the CP 20% the highest, the HP 9.5% and HP 38% showed intermediate values of hardness. Bleaching agents did not affect the roughness. CP 20% and HP 38% promoted the highest values of ΔE and higher reduction of yellowish tone of tooth. Lightness increase after bleaching treatment for all groups. CONCLUSIONS: All the bleaching agents tested showed effectiveness, but with reduced hardness. Key words:Carbamide peroxide, hydrogen peroxide, tooth whitening, hardness, roughness.

Effect of Electric Current-assisted Application of Adhesives on their Bond Strength and Quality.

PURPOSE: To assess the effect of the application of different electric currents on dentin bonding and resin infiltration of self-etching and etch-and-rinse adhesives. MATERIALS AND METHODS: Two hundred four sound third molars were selected and divided in groups according to the adhesive (self-etch [CSE, Clearfil SE Bond, Kuraray Noritake], universal [SBU, Single Bond Universal, 3M Oral Care], and etch-and-rinse [SB2, Adper Single Bond 2 (SB2), 3M Oral Care]) and electrical current used (0, 5, 10, 15, 20, 25, 30, and 35 µA). Light curing was performed for 10 s with an LED-curing unit at 1000 mW/cm2. Composite blocks were constructed of nanofilled composite in increments of 2 mm, which were light cured for 20 s. Specimens were sectioned into sticks with a cross-sectional area of ~1 mm2 and stored in distilled water at 37°C for 24 h. Microtensile bond strength (µTBS) testing (n = 8) was performed using a universal testing machine at a crosshead speed of 0.5 mm/min until failure. The bonding quality (n = 2) of adhesives applied with or without 35-µA electric current was evaluated using confocal laser scanning microscopy. Bond strengths were analyzed with two-way ANOVA and Tukey's test (α = 0.05). RESULTS: CSE presented the highest µTBS for all electrical currents tested. For CSE and SBU, electrical currents from 0-20 µA showed the lowest µTBS. Electrical currents from 0-10 and 20-25 µA yielded the lowest µTBS for SB2. CSE and SB2 applied under 35 µA showed a greater number of resin tags in dentin tubules. Fluorescein penetration into the hybrid layer was found for SBU applied without electric current. CONCLUSION: The application of adhesives using 35-µA electric current improved the bond strength and quality of the adhesive interface.

Chemical composition and roughness of enamel and composite after bleaching, acidic beverages and toothbrushing.

BACKGROUND: In this study was assessed the surface roughness and chemical composition of tooth enamel and composite resin after bleaching treatment, immersion in acidic beverages, and simulated toothbrushing. MATERIAL AND METHODS: One hundred and twenty dental blocks (10 x 10 x 3 mm) were randomly assigned (n = 10) according to surface treatment [none (N), bleaching (B), toothbrushing (T), and B+T] and storage medium [saliva (S), whiskey (W), and orange juice (O)]: experimental groups - N+S, N+W, N+O, B+S, B+W, B+O, S+T, W+T, O+T, B+S+T, B+W+T, and B+O+T. Two bleaching sessions were conducted using 38% hydrogen peroxide (3 applications). Surface roughness was measured using a roughness tester and composition was determined by micro energy-dispersive X-ray fluorescence spectrometry (µ-EDXRF) before and after treatments. Calcium/phosphorus (Ca/P) ratio in enamel and silica (Si) content in composite were evaluated. Data were statistically analyzed by ANOVA and Tukey's test (α = 0.05). RESULTS: Overall, increased values of surface roughness for enamel and composite were observed mainly after immersion in orange juice and bleaching/toothbrushing association. Moreover, this association and immersion in whiskey resulted in lower Ca/P ratio and after aging methods, bleached and bleached/toothbrushed groups showed decreased in Ca/P ratio compared to initial values. All groups showed Si content decrease at the end, except the group without surface treatment and immersed in saliva, and bleaching followed by immersion in orange juice and toothbrushing caused the highest Si reduction. CONCLUSIONS: Bleaching and toothbrushing combination strengthened the effects caused by acidic drinks on roughness and chemical composition of enamel and composite. Key words:Tooth bleaching, toothbrushing, physical properties, chemical properties.

Effects of bleaching using 10% carbamide peroxide with calcium or amorphous calcium phosphate on enamel mineral content and hardness / Asociación entre la severidad de Hipomineralización Incisivo-Molar (HIM) y lesiones cavitadas de caries en escolares

ABSTRACT This study evaluated enamel mineral content and surface microhardness before and after bleaching treatment using 10% carbamide peroxide (CP) containing calcium (Ca) or amorphous calcium phosphate (ACP). Thirty-six bovine slabs were randomly allocated into 3 groups (n = 12) according to bleaching treatment: G1 - Opalescence PF 10% (CP), G2 -NiteWhite ACP (CP+ACP), and G3 - Opalescence PF (10%) with calcium (CP+CA). The bleaching agent was applied on enamel surface for 6 h/day over a period of 21 days. Enamel surface was evaluated by Knoop microhardness (KNH) and micro energy-dispersive X-ray fluorescence spectrometry (p-EDXRF) at baseline and at after bleaching treatment. Data were statistically analyzed by repeated measures ANOVA and Tukey's test (a = 0.05). There was a significant decrease in microhardness after bleaching treatments for all study groups, but no difference between bleaching gels. There was no difference in the Ca/P ratio measured by p-EDXRF for all groups at the study times, but the mean value was lower in group CP+CA than in group CP+ACP. Group CP was similar to both CP+ACP and CP+CA. It can be concluded that enamel microhardness decreased after the bleaching process, regardless of the presence of calcium or ACP, but there was no significant change in the Ca/P ratio of enamel after bleaching for each tested gel. This indicates that the bleaching gels have erosive potential, causing softening of enamel without promoting surface loss, regardless of the presence of calcium of ACP ions.

RESUMO Este estudo avaliou o conteúdo mineral do esmalte e a microdureza superficial antes e após o tratamento clareador, utilizando peróxido de carbamida 10% (PC) contendo cálcio (Ca) ou fosfato de cálcio amorfo (ACP) em sua composigao. Trinta e seis espécimes de esmalte bovino foram alocados aleatoriamente em 3 grupos (n = 12) de acordo com os tratamentos clareadores: G1 - Opalescence PF 10% (CP), G2 -NiteWhite (CP+ACP); e G3 - Opalescence PF (10%) com cálcio (CP + CA). O agente clareador foi aplicado na superficie do esmalte por 6 h/dia por um periodo de 21 dias. A superficie do esmalte foi avaliada por microdureza Knoop (KNH) e espectrometria de fluorescencia de raios X micro-dispersiva (p-EDXRF) no inicio e após o tratamento clareador. Os dados foram analisados estatisticamente pelo teste ANOVA de medidas repetidas e Tukey (a = 0,05). Houve uma diminuigao significativa da microdureza após os tratamentos clareadores para todos os grupos estudados, mas nao houve diferenga entre os diferentes géis. Nao houve diferenga da relagao Ca/P mensurada por p-EDXRF para todos os grupos nos tempos estudados; no entanto, o grupo CP+CA apresentou menor valor comparado ao grupo CP+ACP. O grupo CP foi similar aos grupos CP+ACP e CP+CA. Portanto, pode-se concluir que houve redugao significativa da microdureza do esmalte após o clareamento, independente da presenga de cálcio ou APC na composigao dos géis, embora nao tenha havido alteragao significando na relagao Ca/P do esmalte após o clareamento. Isto indica um potencial erosivo dos géis clareadores, causando o amolecimento sem perda da estrutura do esmalte, independente da presenga dos íons cálcio e ACP.

Effects of bleaching using 10% carbamide peroxide with calcium or amorphous calcium phosphate on enamel mineral content and hardness.

This study evaluated enamel mineral content and surface microhardness before and after bleaching treatment using 10% carbamide peroxide (CP) containing calcium (Ca) or amorphous calcium phosphate (ACP). Thirtysix bovine slabs were randomly allocated into 3 groups (n = 12) according to bleaching treatment: G1 Opalescence PF 10% (CP), G2 NiteWhite ACP (CP+ACP), and G3 Opalescence PF (10%) with calcium (CP+CA). The bleaching agent was applied on enamel surface for 6 h/day over a period of 21 days. Enamel surface was evaluated by Knoop microhardness (KNH) and micro energydispersive Xray fluorescence spectrometry (µEDXRF) at baseline and at after bleaching treatment. Data were statistically analyzed by repeated measures ANOVA and Tukey's test (α = 0.05). There was a significant decrease in microhardness after bleaching treatments for all study groups, but no difference between bleaching gels. There was no difference in the Ca/P ratio measured by µEDXRF for all groups at the study times, but the mean value was lower in group CP+CA than in group CP+ACP. Group CP was similar to both CP+ACP and CP+CA. It can be concluded that enamel microhardness decreased after the bleaching process, regardless of the presence of calcium or ACP, but there was no significant change in the Ca/P ratio of enamel after bleaching for each tested gel. This indicates that the bleaching gels have erosive potential, causing softening of enamel without promoting surface loss, regardless of the presence of calcium of ACP ions.

Este estudo avaliou o conteúdo mineral do esmalte e a microdureza superficial antes e após o tratamento clareador, utilizando peróxido de carbamida 10% (PC) contendo cálcio (Ca) ou fosfato de cálcio amorfo (ACP) em sua composição. Trinta e seis espécimes de esmalte bovino foram alocados aleatoriamente em 3 grupos (n = 12) de acordo com os tratamentos clareadores: G1 Opalescence PF 10% (CP), G2 NiteWhite (CP+ACP); e G3 Opalescence PF (10%) com cálcio (CP + CA). O agente clareador foi aplicado na superfície do esmalte por 6 h/dia por um período de 21 dias. A superfície do esmalte foi avaliada por microdureza Knoop (KNH) e espectrometria de fluorescência de raios X microdispersiva (µEDXRF) no início e após o tratamento clareador. Os dados foram analisados estatisticamente pelo teste ANOVA de medidas repetidas e Tukey (α = 0,05). Houve uma diminuição significativa da microdureza após os tratamentos clareadores para todos os grupos estudados, mas não houve diferença entre os diferentes géis. Não houve diferença da relação Ca/P mensurada por µEDXRF para todos os grupos nos tempos estudados; no entanto, o grupo CP+CA apresentou menor valor comparado ao grupo CP+ACP. O grupo CP foi similar aos grupos CP+ACP e CP+CA. Portanto, podese concluir que houve redução significativa da microdureza do esmalte após o clareamento, independente da presença de cálcio ou APC na composição dos géis, embora não tenha havido alteração significando na relação Ca / P do esmalte após o clareamento. Isto indica um potencial erosivo dos géis clareadores, causando o amolecimento sem perda da estrutura do esmalte, independente da presença dos íons cálcio e ACP.

Physicochemical changes in enamel submitted to pH cycling and bleaching treatment.

OBJECTIVE: The purpose of this study was to assess the hardness, mineral content, surface roughness, and micromorphology of sound and slightly demineralized enamels, before and after bleaching procedure using 10% carbamide peroxide. METHODS: Sixty bovine dental blocks were randomly divided into the following two groups: 30 slabs were submitted to three cycles of pH and 30 slabs were noncycled. Hardness (n=10) was measured using the microhardness tester with Knoop indenter under a 50 g load for 5 seconds. The calcium/phosphate (Ca/P) ratio (n=10) was obtained using a micro-energy-dispersive X-ray fluorescence (µ-EDXRF) spectrometer. The measurement of roughness average (n=10) was performed using a surface roughness tester. Specimens were bleached 6 hours/day during 21 days, and then, physicochemical properties were re-evaluated. Two additional specimens were carried out to evaluate surface micromorphology using the scanning electron microscopy. Data were statistically analyzed by ANOVA and Tukey's test (α=0.05). RESULTS: Sound and slightly demineralized enamels showed no difference in Ca/P ratio after dental bleaching according to the µ-EDXRF analysis, but the Ca/P ratio decreased after bleaching for slightly demineralized enamel. Bleaching treatment decreased the hardness and increased the surface roughness, causing micromorphology alterations. CONCLUSION: Therefore, bleaching procedure promoted change in bovine enamel surface and increased the demineralization of slightly demineralized enamel but not affected the mineral content of sound enamel.

Effect of Heavy Metals Contamination from Cigarette Smoke on Sound and Caries-Like Enamel.

In this study, we sought to evaluate the influence of cigarette smoke and pH cycling on the chemical composition and surface/cross-sectional enamel microhardness. A total of 40 dental blocks obtained from bovine incisors were divided into four groups (n=10): no treatment (control); exposure to cigarette smoke (CS); exposure to pH cycling (PC); and exposure to cigarette smoke and pH cycling (CS-PC). The samples were analyzed by synchrotron radiation micro X-ray fluorescence, bench mode X-ray fluorescence, as well as surface microhardness (SMH) and cross-sectional microhardness (CSMH) testing. The SMH results were submitted to analysis of variance (ANOVA) and Tukey's test. The CSMH results were evaluated using split-plot ANOVA and Tukey's test. A high amount of Cd and Pb and traces of Ni and As were observed in enamel and dentin after exposure to cigarette smoke (CS and CS-PC). The SMH and CSMH of CS were statistically higher when compared with the control. The PC and CS-PC showed lower SMH and CSMH. We conclude that exposure to cigarette smoke promoted heavy metal deposition in enamel/dentin. In addition, it increased the enamel microhardness but did not promote a protective effect on the in vitro development of caries. The clinical significance of this work is that there is significant bioaccumulation of heavy metals from cigarette smoke on the surface and in the enamel and dentin.

Mechanical and surface properties analysis of restorative materials submitted to erosive challenges in situ.

OBJECTIVE: This study aims to evaluate the effect of acidic solutions (AS) on surface roughness (Ra) and microhardness of restorative materials (RM). MATERIALS AND METHODS: Eight volunteers wore intraoral palatal devices (IPD) containing samples of RM: Ketac Nano (KN); Ketac Nano + Biscover LV (KN-B); Esthet-X (EX); Esthet-X + Biscover LV (EX-B); Supreme XT (SXT); Supreme XT + Biscover LV (SXT-B); and bovine enamel. The samples were submitted to three phases: (1) immersion in 0.01M hydrochloric acid (HCl) - 10 min, three times/day (14 days); (2) immersion in soft drink (Sprite®) - 10 min, three times/day (14 days); and (3) keeping in saliva (14 days). Changes in Ra/microhardness were measured before/after the three phases. STATISTICAL ANALYSIS: ANOVA (α = 0.05) and Fisher's test. RESULTS: Materials sealed with Biscover LV (B) presented lowest values in all periods. KN glass ionomer cement showed highest Ra values after exposure in AS. Application of B did not reduce the Ra for the composites studied, except for EX after immersion in HCl. AS promoted changes in Ra/microhardness of RM, except for sealed materials. CONCLUSIONS: The acids used were able to change the Ra and microhardness of RM, except of the sealed materials. The resin-modified GIC showed the most significant changes after immersion in AS; and the composites sealed with B, even after immersion in acidic solutions (AS), showed the lowest Ra values and the least degradation in microhardness, especially when subjected to low pH solutions.

Effect of sodium metabisulfite gel on the bond strength of dentin of bleached teeth.

OBJECTIVE: This study aimed to evaluate the effect of the application of sodium metabisulfite (SMB) on the bond strength of bleached teeth. MATERIALS AND METHODS: The study was divided into two parts. The first part evaluated the application of various concentrations of SMB for 1 h prior to the completion of bonding procedures. Fifty blocks were divided into five groups (n = 10): control; bleaching with 35% hydrogen peroxide (HP); HP + 5% SMB; HP + 12.5% SMB; and HP + 25% SMB. The second part evaluated the application of 25% gel SMB to either enamel or dentin, including the application time. Sixty blocks were divided into six groups (n = 10): control; bleaching with 35% HP; HP + 25% SMB for 1 h in enamel; HP + 25% SMB for 1 h in dentin; HP + 25% SMB for 10 min in enamel; and HP + 25% SMB for 10 min in dentin. STATISTICAL ANALYSIS: Following the completion of microshear bond testing, data were analyzed using one-way analysis of variance as well as Tukey's and Dunnett's tests. RESULTS: In part 1, data analysis revealed statistical differences (P < 0.0001) between HP and HP + 5% SMB. No statistical differences were found between the control and both HP + 12.5% SMB and HP + 25% SMB. Part 2 revealed a statistical difference (P = 0.001359) only between the bleached group and others. CONCLUSIONS: The use of 25% SMB gel immediately after bleaching was able to reverse the deleterious effect of bleaching on the bond strength of dental composites to dentin.

Influence of pre-heating and ceramic thickness on physical properties of luting agents.

PURPOSE: The objective of this in vitro study was to evaluate the influence of ceramic thickness and pre-heating of luting agents on their physical properties. MATERIALS AND METHODS: The materials RelyX Arc, RelyX Ultimate, RelyX Veneer, and Filtek Z350 Flow were handled at different temperatures (23°C or 54°C), inserted into matrix, and photoactivated through ceramic disks (0.75 mm or 1.5 mm). The following tests were performed ( n=8): degree of conversion, Knoop Hardness, cross-link density, water sorption, solubility, and ultimate tensile strength. Data were analyzed using three-way analysis of variance and Tukey's test (α=0.05). RESULTS: Regarding ceramic thickness, the thinnest ceramic resulted in higher values of Knoop Hardness ( p=0.027). The lowest temperature (23°C) resulted in a higher solubility ( p=0.0257), and water sorption ( p=0.0229) values. There was also statistical difference among the materials: RelyX Arc showed a higher degree of conversion and ultimate tensile strength, followed by RelyX Veneer, RelyX Ultimate, and Filtek Z350 Flow. For Knoop Hardness and cross-link density tests, RelyX Ultimate showed the highest values, followed by RelyX Arc, RelyX Veneer, and Filtek Z350 Flow. For water sorption and solubility, RelyX Veneer showed the highest values, followed by RelyX Arc, RelyX Ultimate, and Filtek Z350 Flow. CONCLUSION: Pre-heating interfered with water sorption and solubility, whereas ceramic thickness only affected Knoop Hardness; the physical properties of the materials are dependent on their composition.

Effect of preheating and light-curing unit on physicochemical properties of a bulk fill composite.

OBJECTIVE: The aim of this study is to evaluate the effect of composite preheating and polymerization mode on degree of conversion (DC), microhardness (KHN), plasticization (P), and depth of polymerization (DP) of a bulk fill composite. METHODS: Forty disc-shaped samples (n = 5) of a bulk fill composite were prepared (5 × 4 mm thick) and randomly divided into 4 groups according to light-curing unit (quartz-tungsten-halogen [QTH] or light-emitting diode [LED]) and preheating temperature (23 or 54 °C). A control group was prepared with a flowable composite at room temperature. DC was determined using a Fourier transform infrared spectrometer, KHN was measured with a Knoop indenter, P was evaluated by percentage reduction of hardness after 24 h of ethanol storage, and DP was obtained by bottom/top ratio. Data were statistically analyzed by analysis of variance and Tukey's test (α = 0.05). RESULTS: Regardless of light-curing, the highest preheating temperature increased DC compared to room temperature on bottom surface. LED showed a higher DC compared to QTH. Overall, DC was higher on top surface than bottom. KHN, P, and DP were not affected by curing mode and temperature, and flowable composite showed similar KHN, and lower DC and P, compared to bulk fill. CONCLUSION: Composite preheating increased the polymerization degree of 4-mm-increment bulk fill, but it led to a higher plasticization compared to the conventional flowable composite evaluated.

Influence of surface sealing on color stability and roughness of composite submitted to ultraviolet-accelerated aging.

AIM: In the present study, we evaluated the influence of surface sealing on color stability and surface roughness of a composite resin after accelerated artificial aging. METHODS: Thirty-two specimens of a composite were prepared. After 24 h, the specimens were polished and divided into four groups (n = 8), according to the surface sealant used, including the control, which had no sealant application. Baseline color was measured according to the CIELab system using a reflection spectrophotometer. Surface roughness was determined using a profilometer with a cut-off of 0.25 mm. After these tests, specimens were aged for 252 h in an ultraviolet (UV)-accelerated aging chamber. Color stability was determined by difference between coordinates obtained before and after the aging procedure. Data of color change and roughness were evaluated by anova and Fisher's exact test (α = 0.05). RESULTS: The results showed that the unsealed group had the highest color change compared to other groups (P = 0.0289), and there was no significant difference between groups sealed with surface sealant (P > 0.05). The artificial aging caused an increase in roughness values independent of the experimental group studied (P = 0.0015). CONCLUSION: The sealed composites showed lower color change after UV aging, but all groups showed clinically-acceptable color change, and only liquid polish decreased roughness.

Influence of Enamel Thickness on Bleaching Efficacy: An In-Depth Color Analysis.

This study evaluated the influence of different enamel thicknesses and bleaching agents on treatment efficacy in-depth by spectrophotometry color analysis. Eighty bovine dental fragments were previously stained in black tea solution and randomly assigned into eight groups (n=10), 1.75mm dentin thickness and different enamel thicknesses as follows: 0.5mm, 1.0mm planned, 1.0mm unplanned (aprismatic enamel), and absence of enamel. The 10% carbamide peroxide (CP) and 35% hydrogen peroxide (HP) bleaching gels were applied on the enamel surface following the manufacturer's recommendations. Color of underlying dentin was evaluated at four times: after staining with tea (baseline) and after each one of the three weeks of bleaching treatment, by CIE L*a*b* system using reflectance spectrophotometer (CM 700d, Konica Minolta). The ΔE, ΔL, Δa, and Δb values were recorded and subjected to repeated measures ANOVA and Tukey's test (α=0.05). The results showed an increase on lightness (L*), with decreased redness (a*) and yellowness (b*). At first and second week, bleaching with CP showed higher whitening effectiveness compared to bleaching with HP and the presence of aprismatic enamel significantly reduced ΔE for bleaching with CP. After three weeks of bleaching, few differences were observed between CP and HP groups, and outer enamel layer caused no influence on bleaching effectiveness. Overall, both at-home and in-office bleaching treatments were effective and the presence of aprismatic enamel did not interfere on the whitening efficacy.

Efficacy of a bioactive material and nanostructured desensitizing on dentin hypersensitivity treatment / Eficácia de um material bioativo e dessensibilizante nanoestruturado no tratamento da hipersensibilidade dentinária

Introduction: Dentin hypersensitivity is a frequent occurrence in dental practice. It is clinically characterized by acute, short, and temporary pain in response to mechanical, chemical, thermal, or osmotic stimuli resulting from dentin exposure. Objective: To compare in vivo the effect of an experimental crystalline bioactive material and nanostructured desensitizing on the pain assessment among patients with cervical dentin hypersensitivity. Material and method: Thirty patients were selected for this study, who were randomly assigned to two groups (n=15) in a split-mouth design. Each patient received two treatments: group 1 (fluoride gel and bioactive material) and group 2 (fluoride gel and nanostructured desensitizing). Pain analyses were performed using a visual analogue scale, ranging 0-10. Baseline pain measurement was performed prior to initial treatment (T0) and new measurements were carried out weekly for 3 weeks (T1, T2, and T3) before materials were reapplied. Final pain analysis was performed 3 months after initial treatment (T4). Degree of pain reduction was calculated using the formula T0 - Tperiod after treatment. The data of the pain measurements were analyzed using 2-way repeated measure ANOVA and Tukey’s test (α=0.05). Result: Regardless of evaluation period, there was no statistical difference on pain reduction between the treatments (p>0.05). The degree of pain was reduced significantly in each evaluated period for all tested treatments (p<0.05), by approximately three degrees after 3 months. Conclusion: The tested desensitizing materials were effective on dentin hypersensitivity reduction.

Introdução: A hipersensibilidade dentinária é uma ocorrência frequente na prática clínica; clinicamente caracterizada por dor aguda, curta e temporária, em resposta ao estímulo mecânico, químico, térmico ou osmótico causada pela exposição dentinária. Objetivo: Comparar in vivo o efeito de um material bioativo cristalino experimental e um dessensibilizante nanoestruturado na avaliação da dor de pacientes com hipersensibilidade dentinária cervical. Material e método: Trinta pacientes foram selecionados para este estudo, que foram randomicamente divididos em dois grupos (n=15) em um desenho experimental de boca dividida. Cada paciente recebeu dois tratamentos: grupo 1 (flúor gel e material bioativo) e grupo 2 (flúor gel e dessensibilizante nanoestruturado). As análises de dor foram realizadas usando uma escala visual analógica, variando de 0-10. A mensuração da dor inicial foi realizada previamente ao tratamento inicial (T0) e novas análises foram realizadas semanalmente durante 3 semanas (T1, T2 e T3) antes da reaplicação dos materiais. A análise final da dor foi realizada 3 meses após o início do tratamento (T4). O grau de redução de dor foi mensurado pela fórmula: T0 - Tperíodo após tratamento. Os dados das mensurações de dor foram analisados pela ANOVA para medidas repetidas 2 critérios e teste de Tukey (α=0,05). Resultado: Independente do período de avaliação, não houve diferença estatística entre todos os tratamentos na redução da dor (p>0,05). O grau de dor reduziu significativamente em cada período avaliado para todos os tratamentos testados (p<0,05), aproximadamente três graus após 3 meses. Conclusão: Os materiais dessensibilizantes testados foram efetivos na redução da hipersensibilidade dentinária.

Effect of 7.5% hydrogen peroxide containing remineralizing agents on hardness, color change, roughness and micromorphology of human enamel.

PURPOSE: To determine the microhardness, color change, surface roughness, and micromorphology of tooth enamel submitted to bleaching treatment with 7.5% hydrogen peroxide (HP) with added calcium, amorphous calcium phosphate, sodium fluoride (NaF), and hydroxyapatite (HA). METHODS: 80 enamel slabs were used (n = 10). Three commercial agents [Pola Day 7.5%, Day White ACP 7.5% (DW-ACP), and White Class Calcium 7.5% (WC-Calcium)], three experimental (7.5% HP+NaF, 7.5% HP+HA, and 7.5% PH+NaF+HA), a positive control (with HP), and a negative control (without HP) groups were assessed. The commercial products were applied according to manufacturers' recommendations and the experimental ones were applied for 1.5 hours daily. During and after treatment, specimens were stored in artificial saliva. Tests were performed at baseline, 7, 14, 21, 28, and 35 days. Data were analyzed by ANOVA and Tukey's test (α = 0.05). RESULTS: DW-ACP presented lower microhardness and HP+HA presents the highest values (P < 0.05); only the experimental group presented color change similar to the commercial agents (P > 0.05). Overall, roughness increased with time (P < 0.05) and porosities, and deposition of crystalline structures in groups HP+HA and HP+NaF+HA were noted. The HP+HA agent was capable of reducing the loss of enamel microhardness due to bleaching and also present color change similar to the commercial products.

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

PURPOSE: 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. METHODS AND MATERIALS: 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). RESULTS: 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. CONCLUSION: The fluorescence of composite restorations is dependent of the layering technique and is affected by the diet. CLINICAL SIGNIFICANCE: 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.