Improvement on properties of experimental resin cements containing an iodonium salt cured under challenging polymerization conditions.

OBJECTIVE: The use of resin cements in clinical practice entails photopolymerization through prosthetic devices, which precludes light penetration. The objective of this study was to modify experimental resin cements (ERCs) with diphenyliodonium hexafluorophosphate (DPI) in an attempt to improve chemical and mechanical properties of materials cured with reduced irradiance and final radiant exposure. METHODS: A co-monomer base containing a 1:1 mass ratio of 2.2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bis-GMA) and triethyleneglycol dimethacrylate (TEGDMA) was prepared, with 1mol% of camphorquinone and 2mol% of ethyl 4-(dimethylamino)benzoate as initiator system. The resin was divided into 4 fractions according to the DPI concentrations (0, 0.5, 1 and 2mol%). The challenging polymerization condition was simulated performing the light activation (12, 23 and 46s) through a ceramic block (3mm thick). The irradiance was assessed with a calibrated spectrometer (1320mW/cm2), resulting in three levels of radiant exposure (0.58, 1.1 and 2.2J/cm2). The polymerization kinetics was evaluated in real-time using a spectrometer (Near-IR). Water sorption and solubility was analyzed and the cohesive strength of resins obtained through the microtensile test. Polymerization stress was assessed by Bioman method. RESULTS: Resins containing DPI had higher degree of conversion and rate of polymerization than the control (without DPI). The use of DPI reduced water sorption and solubility, and led to higher cohesive strength compared to resins without the iodonium salt. However, the stress of polymerization was higher for experimental resins with DPI. SIGNIFICANCE: Even under remarkably reduced irradiance, cements containing a ternary initiating system with an iodonium salt can present an optimal degree of conversion and chemical/mechanical properties.

Positive Synergistic Effect of Adhesives and Resin Cements Containing an Iodonium Salt on Bonding of Fiber Posts.

PURPOSE: To evaluate the push-out bond strength (PBS) of glass-fiber posts (GFP) in different root canal zones (cervical, middle, and apical), bonded with experimental simplified adhesives (ESAs) containing different initiator systems (camphorquinone [CQ] or phenylpropanodione [PPD]) with or without diphenyl iodonium hexafluorophosphate (DPI), in combination with a DPI-containing composite cement. MATERIALS AND METHODS: ESA blends were prepared with bisphenol glycidyl methacrylate (bis-GMA), triethylene glycol dimethacrylate (TEG-DMA), 1,3-glycerol dimethacrylate (GDMA), 2-hydroxyethyl methacrylate (HEMA), and ethanol, then divided into 12 experimental groups (n = 10) according to the initiator systems (CQ, PPD, or CQ + PPD) and the presence or absence of DPI. The roots of 120 extracted bovine incisors were prepared with #5 Largo drills and the GFP were cemented with each ESA and experimental composite cements containing 0.05 mol% of DPI. The push-out bond strength (PBS) test was performed after 24 h of storage. Failure patterns were analyzed under a stereomicroscope. Data were analyzed with split-plot two-way ANOVA and Tukey's test (α = 0.05). RESULTS: PBS was significantly higher for DPI-containing ESAs in all regions evaluated, with the group containing 0.5 CQ + 1 PPD + 0.5 DPI exhibiting the highest PBS. There was no statistically signficant difference among groups without DPI. Most failures were classified as adhesive at the cement-dentin interface. CONCLUSIONS: The combination of an adhesive and a composite cement containing DPI salt can improve GFP bonding to root dentin, even in the apical region.

Effect of alternative solvent evaporation techniques on mechanical properties of primer-adhesive mixtures.

This study evaluated the influence of the mode and time of solvent evaporation on the tensile strength (TS), flexural strength (FS) and elastic modulus (EM) of two adhesive systems: Scotchbond Multipurpose (SBMP) and Clearfil SE (CSEB). For this purpose, rectangular samples (2x1x7 mm) were prepared with 10 µL of primer and the solvents were evaporated with air spray at (23±1) ºC, (40±1) ºC and negative control (without spray). For each temperature, the times of 5, 20, 30, and 60 seconds were investigated. The statistical results showed that evaporation at 40±1ºC resulted in better EM for the two adhesives tested and all the evaporation times evaluated. However, there were no significant differences between the times and modes of evaporation for TS. The results of this study indicate that evaporation at a temperature of (40±1) °C could improve the elastic modulus of both adhesives tested, regardless of the evaporating time.

Este estudo avaliou a influência do modo e do tempo de evaporação do solvente na resistência à tração (RT), resistência à flexão (RF) e módulo de elasticidade (MR) de dois sistemas adesivos: Scotchbond Multipurpose (SBMP) e Clearfil SE (CSEB). Para isso, amostras retangulares (2x1x7 mm) foram preparadas com 10 µL de primer e os solventes foram evaporados com aerossol a (23±1) ºC, (40±1) ºC e controle negativo (sem aerossol). Para cada temperatura, foram avaliados os tempos de 5, 20, 30 e 60 segundos. Os resultados estatísticos mostraram que a evaporação a (40±1) ºC resultou em melhor MR para os dois adesivos testados e todos os tempos de evaporação avaliados. No entanto, não houve diferenças significativas entre os tempos e modos de evaporação na RT. Os resultados deste estudo indicam que a evaporação a uma temperatura de (40±1) °C poderia melhorar o módulo de elasticidade de ambos os adesivos testados, independentemente do tempo de evaporação.

Effect of alternative solvent evaporation techniques on mechanical properties of primer-adhesive mixtures / Efeito de técnicas alternativas utilizando evaporação de solvente nas propriedades mecânicas da mistura primer-adesivo

ABSTRACT This study evaluated the influence of the mode and time of solvent evaporation on the tensile strength (TS), flexural strength (FS) and elastic modulus (EM) of two adhesive systems: Scotchbond Multipurpose (SBMP) and Clearfil SE (CSEB). For this purpose, rectangular samples (2x1x7 mm) were prepared with 10 μL of primer and the solvents were evaporated with air spray at (23±1) ºC, (40±1) ºC and negative control (without spray). For each temperature, the times of 5, 20, 30, and 60 seconds were investigated. The statistical results showed that evaporation at 40±1ºC resulted in better EM for the two adhesives tested and all the evaporation times evaluated. However, there were no significant differences between the times and modes of evaporation for TS. The results of this study indicate that evaporation at a temperature of (40±1) °C could improve the elastic modulus of both adhesives tested, regardless of the evaporating time.

RESUMO Este estudo avaliou a influência do modo e do tempo de evaporação do solvente na resistência à tração (RT), resistência à flexão (RF) e módulo de elasticidade (MR) de dois sistemas adesivos: Scotchbond Multipurpose (SBMP) e Clearfil SE (CSEB). Para isso, amostras retangulares (2x1x7 mm) foram preparadas com 10 μL de primer e os solventes foram evaporados com aerossol a (23±1) ºC, (40±1) ºC e controle negativo (sem aerossol). Para cada temperatura, foram avaliados os tempos de 5, 20, 30 e 60 segundos. Os resultados estatísticos mostraram que a evaporação a (40±1) ºC resultou em melhor MR para os dois adesivos testados e todos os tempos de evaporação avaliados. No entanto, não houve diferenças significativas entre os tempos e modos de evaporação na RT. Os resultados deste estudo indicam que a evaporação a uma temperatura de (40±1) °C poderia melhorar o módulo de elasticidade de ambos os adesivos testados, independentemente do tempo de evaporação.

Effects of cigarette smoke on color, roughness and gloss of high-viscosity bulk-fill resin composites.

PURPOSE: To evaluate the effect of cigarette smoke (CS) on color, roughness and gloss of bulk-fill resin composites. METHODS: Resin discs (10 x 2 mm) were made for resin composites (n= 10) : Filtek Z250XT (control), Filtek One Bulk Fill (FOBF), Tetric N-Ceram Bulk-Fill (TBF) and Aura Bulk-Fill (ABF). The color ( ΔL*, Δa*, Δb*, ΔE and ΔE00), roughness (Ra) and gloss analyses were performed at the baseline and after CS exposure (10 packs of cigarettes - Marlboro Red). The data were analyzed with repeated measures ANOVA and Tukey's test for Ra and gloss; and one-way ANOVA and Tukey's test for ΔL*, Δa*, Δb*, ΔE and ΔE00 ( α= 0.05). RESULTS: For ΔL*, all groups presented reduced luminosity and all bulk-fill resin composites differed statistically from the control (P< 0.05). ABF presented greater variation of ΔL*, differing statistically from all resin composites (P< 0.05). For ΔE and ΔE00, all bulk-fill resin composites showed greater staining, differing statistically from the control, which presented lower values. For Ra, after CS, only ABF presented a decrease, differing statistically from baseline (P< 0.05). After CS smoke, all groups presented gloss increase, statistically different from the baseline (P< 0.05), and when compared among resin composites, no difference was found. CLINICAL SIGNIFICANCE: Bulk-fill resin composites are more prone to staining by cigarette smoke when compared to the conventional microhybrid resin composites.

Utilizing the optical properties of composite resins to improve esthetics: a layering technique for anterior restorations.

A comprehensive knowledge of the optical properties of composite resins is essential to achieving optimal results in direct anterior restorations. This case report describes an anterior composite resin restoration fabricated with a layering technique and explains how to use a simple photographic method to verify that the desired optical effects are reproduced. A Class IV restoration was completed on a maxillary central incisor with the help of a silicone guide. An esthetic result was achieved through careful color examination as well as material selections that were based on knowledge of the translucency, opacity, and fluorescence of the chosen direct composite resins. The approach of combining a composite resin designed for bleached teeth with highly opalescent and translucent resins as well as matching the natural dental anatomy provided excellent esthetic results. The suitable reproduction of optical characteristics was confirmed by increasing the contrast of the final photograph, which highlighted the translucency achieved in the area of the mamelons.

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 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.

Effect of energy density and delay time on the degree of conversion and Knoop microhardness of a dual resin cement.

AIM: In the present study, we evaluated the influence of the photo-curing delay time and energy density on the degree of conversion and the Knoop microhardness of a resin cement. METHODS: Seventy-eight samples were assigned to 13 groups (n = 6), one of which received no light curing (control). The samples were made of a dual-cured resin cement (RelyX ARC) with the aid of a Teflon matrix, submitted to one of the following energy densities (J/cm²): 7, 14, 20, and 28. Delay times were immediate (0), 1 min, or 2 min. After 24 h, the degree of conversion and microhardness were measured at three segments: cervical, medium, and apical. Data were submitted to three-way anova and Tukey's and Dunnett's tests, the latest of which was used to compare the control to the experimental groups. RESULTS: No interaction was observed between delay time and energy density regarding the degree of conversion. The cervical segment showed the highest values, while the apical showed the lowest. Microhardness values concerning the cervical segment in all groups were statistically different from that obtained for the control. CONCLUSION: A high-irradiance light-curing unit allows for a reduced irradiation exposure time with a short delay time, aimed at tooth restorations using a dual-cured resin cement.

Influence of light-activation protocol on methacrylate resin-composite evaluated by dynamic mechanical analysis and degree of conversion.

The aim of this study was to evaluate the degree of conversion (DC) and to identify the viscoelastic properties: storage modulus (E'), loss modulus (E"), tangent delta (tan δ), and glass transition temperature (T g ) of a microhybrid resin-composite light-activated by three different protocols. A Filtek Z250 (3 M ESPE) shade A3 was inserted in a Teflon mold (21 mm × 5 mm × 1 mm for viscoelastic properties; and 5 mm × 1 mm for DC) and light-activated according to the following light-activation protocols: (S) 1,000 mW/cm(2) × 19 s, (HP) 1,400 mW/cm(2) × 14 s, and (PE) 3,200 mW/cm(2) × 6 s, all set up to deliver 19 J/cm(2). Viscoelastic properties was assessed by dynamic mechanical analysis (DMA) (n = 3), performed in single cantilever clamped mode. DC (n = 5) was measured by FTIR on top (T) and bottom (B) surfaces, and the data was submitted to a split-plot one-way ANOVA. For DC, there was a significant effect for surface factor and light-activation protocols factor. Top surface showed higher DC than B in all experimental conditions. Light-activation protocols S and HP resulted in higher DC than PE and were similar between them. Viscoelastic properties (E', E", tan δ, T g ) were not affected by light-activation protocols. It could be concluded that light-activation protocols influenced DC but not influenced the viscoelastic properties.

Influence of flowable composite and restorative technique on microleakage of class II restorations.

AIM: The aim of the present study was to evaluate the microleakage in class II cavities restored with dental composite by varying the thickness of two flowable composite resins and the restorative technique. METHODS: A total of 130 cavities were prepared on proximal surfaces of bovine teeth and randomly divided in 13 groups. Twelve experimental groups were performed using flowable composite resin as the liner, and they were divided according to the type of flowable composite resin (Filtek Z350 Flow-Z350F and SureFil SDR Flow-SUR), the thickness of the flowable composite (0.5, 1, or 2 mm), and the restorative technique (flowable composite applied at the cavosurface angle or amelodentinal junction) (n = 10). A control group was performed without using a flowable composite. Following restorative procedures and thermocycling, the samples were immersed in Methylene Blue for 2 h, and prepared for analysis in an absorbance spectrophotometer. All results were statistically analyzed (α = 0.05). RESULTS: There was no significant difference between the flowable composites (P > 0.05). The restorative techniques influenced microleakage and were flowable composite dependent (P ≤ 0.05). The lower thickness of the flowable composite provided less microleakage (P ≤ 0.05). CONCLUSION: The use a lower thickness of a flowable composite resin provided less microleakage, suggesting a better sealing tooth-restoration interface.

Effect of polymerization mode and time of adhesive system on microleakage in composite resin restorations.

AIM: To quantify the microleakage on restorations carried out with a two-step etch-and-rise adhesive system and nanofilled composite resin after thermal and mechanical loading cycling. METHODS: Ninety cavities were prepared on proximal surfaces of incisive teeth, and were randomly divided according to the photoactivation time (10, 20, or 30 s) and light-curing mode (Quartz Tungsten Halogen (QTH) lamps, 450 mW/cm(2); Light Emitting Diode (LED) second generation, 1100 mW/cm(2); or LED third generation, 700 mW/cm(2)) of an adhesive system (n = 10). Following restorative procedures and thermal and mechanical loading cycling, the samples were immersed in Methylene Blue for 2 h. The samples were ground, and the powder was prepared for analysis in an absorbance spectrophotometer. All results were statistically analyzed by anova and Tukey's test at the 5% level of significance. RESULTS: There were no significant statistical difference in microleakage between the light-curing mode (P = 0.1212) and light-curing time (P = 0.2043). CONCLUSION: Different curing modes and increasing the curing time were not factors that influenced the process of microleakage.

Effects of Laser Irradiation on Pulp Cells Exposed to Bleaching Agents.

The aim of this study was to evaluate the effect of low-level laser therapy (LLLT) on odontoblast-like cells exposed to a bleaching agent. Mouse dental papilla cell-23 cells were seeded in wells of 24-well plates. Eight groups were established according to the exposure to the bleaching agent and LLLT (0, 4, 10 and 15 J cm(-2) ). Enamel-dentin disks were adapted to artificial pulp chambers, which were individually placed in wells containing Dulbecco's modified Eagle's medium (DMEM). A bleaching agent (35% hydrogen peroxide [BA35%HP]) was applied on enamel (15 min) to obtain the extracts (DMEM + BA35%HP components diffused through enamel/dentin disks). The extracts were applied (1 h) to the cells, and then subjected to LLLT. Cell viability (Methyl tetrazolium assay), alkaline phosphatase (ALP) activity, as well as gene expression of ALP, fibronectin (FN) and type I collagen, were evaluated. The bleaching procedures reduced the cell viability, ALP activity and gene expression of dentin proteins. Laser irradiation did not modulate the cell response; except for FN, as LLLT decreased the gene expression of this protein by the cells exposed to the BA35%HP. It can be concluded that BA35%HP decreased the activities of odontoblasts that were not recovered by the irradiation of the damaged cells with low-level laser parameters tested.

Evaluation of the surface roughness and morphologic features of Y-TZP ceramics after different surface treatments.

OBJECTIVE: This study aimed to investigate the effect of different energy intensities of the Er:YAG laser and of air abrasion with Al(2)O(3) particles on the surface roughness and morphologic characteristics of yttrium-stabilized tetragonal zirconia (Y-TZP) ceramics. BACKGROUND DATA: Surface roughness enhances the micromechanical interlocking of luting agents to ceramic surfaces. However, the most appropriate surface treatment for Y-TZP ceramics has yet to be determined. MATERIALS AND METHODS: Two Y-TZP materials were evaluated: Cercon Smart Ceramics and Procera Zirconia. Thirty plates from each ceramic material were randomly divided into five groups according to the surface treatment received (none [control], air abrasion, or irradiation with the Er:YAG laser at three different energy intensities [200, 400, or 600 mJ]). After the surface treatments, the ceramic plates were gold-coated and their surface roughness (Ra, microm) was measured using confocal microscopy. For each ceramic system, the surface roughness was analyzed through two-way ANOVA/Tukey's test, with a 5% significance level. Changes in the morphological characteristics of the ceramics were examined through light and scanning electron microscopy. RESULTS: For both zirconia-based materials, irradiation with 400 mJ or 600 mJ increased surface roughness and provided significant morphological changes. Air-abraded Cercon surfaces were rougher compared to the ones irradiated with 200 mJ of laser energy, whereas Procera surfaces irradiated with 200 mJ were rougher than the air-abraded ones. CONCLUSIONS: Higher laser power settings (400 and 600 mJ) cause excessive material deterioration, making them unsuitable as surface treatments for zirconia surfaces. Irradiation with 200 mJ provides mild surface alterations, with intermediary features between the effects of air abrasion and higher laser intensities.

24 hours and 3-months bond strength between dual-cured resin cements and simplified adhesive systems.

This study evaluated the bonding compatibility between dual-cured resin cements and simplified adhesive systems (one-step self-etch and two-step etch & rinse), measured after 24 hours and 3 months. The occlusal dentin surfaces of 24 human third molars were exposed and flattened. Teeth were randomly assigned to 3 groups and treated with different combinations of adhesive system and resin cement [G1-Single Bond/Rely X ARC (SB/RX); G2-Excite DSC/Variolink II (EX/VR); G3-Adper Prompt/Rely X ARC (AD/RX)]. Indirect composite restorations were cemented on flattened surfaces, and sectioned to obtain multiple bonded beams for the microtensile bond strength test. The beams from each tooth were tested under tension after 24 hours and 3 months (ANOVA/ Tukey's test, alpha=5%). Failure patterns were evaluated with scanning electron microscopy. After 24h, AD/RX presented the lowest bond strength mean values. AD/RX specimens did not withstand three months storage. SB/RX and EX/VR presented similar bond strengths in both periods tested. The association AD/RX resulted in low bond strength mean values, especially after storage. Cementing indirect restorations using one-step self-etch adhesive systems and dual-cured resin cements would be clinically unreliable.

24 hours and 3-months bond strength between dual-cured resin cements and simplified adhesive systems / Avaliação da resistência de união de cimentos resinosos de dupla polimerização associados a sistemas adesivos simplificados após 24 horas e 3 meses

This study evaluated the bonding compatibility between dualcuredresin cements and simplified adhesive systems (one-step self-etch and two-step etch & rinse), measured after 24 hours and 3 months. The occlusal dentin surfaces of 24 human third molars were exposed and flattened. Teeth were randomly assigned to 3 groups and treated with different combinations ofadhesive system and resin cement [G1 - Single Bond/Rely X ARC (SB/RX); G2 - Excite DSC/Variolink II (EX/VR); G3 -Adper Prompt/Rely X ARC (AD/RX)]. Indirect composite restorations were cemented on flattened surfaces, and sectioned to obtain multiple bonded beams for the microtensile bond strength test. The beams from each tooth were tested under tension after 24 hours and 3 months (ANOVA/ Tukey’s test, α=5%). Failure patterns were evaluated with scanning electron microscopy. After 24h, AD/RX presented the lowest bond strength mean values. AD/RX specimens did not withstandthree months storage. SB/RX and EX/VR presented similar bond strengths in both periods tested. The associationAD/RX resulted in low bond strength mean values, especially after storage. Cementing indirect restorations using one-step self-etch adhesive systems and dual-cured resin cements wouldbe clinically unreliable.

Este estudo avaliou a compatibilidade de união entre cimentos resinosos de dupla polimerização e sistemas adesivos simplificados (adesivo autocondicionante - 1 passo- e adesivo total-each - 2 passos), após 24h e 3 meses. A superfície oclusal de 24 terceiros molares humanos foi exposta e planificada. Os dentes foram aleatoriamente divididos em 3 grupos usados de acordo a seguinte combinação entre sistema adesivo/cimento resinoso [G1 - Single Bond/Rely X ARC (SB/RX); G2 - Excite DSC/Variolink II (EX/VR); G3-Adper Prompt/Rely X ARC (AD/RX)]. Restaurações indiretas em resina composta foram cimentadas na superfície dentinária, e seccionados em múltiplos palitos para a realização do teste de resistência de união através do ensaio de microtração. Os palitos obtidos por dente foram submetidos ao teste após 24 horas e 3 meses (ANOVA/ Tukey test, α=5%). O padrão de fraturafoi observado no microscópio eletrônico de varredura. Após 24 horas, AD/RX apresentou menor valor médio de resistência de união. Os corpos-de-prova do grupo AD/RX não resistiram aoarmazenamento de 3 meses. SB/RX e EX/VR demonstraram similarresistência de união em ambos os períodos avaliados. A associação AD/RX resultou em menores valores médios deresistência de união, especialmente após o armazenamento. A cimentação de restaurações indiretas utilizando sistemas autocondicionantes (1 passo) e cimentos resinosos de dupla polimerização não foi considerada clinicamente confiável.

24 hours and 3-months bond strength between dual-cured resin cements and simplified adhesive systems / AvaliaþÒo da resistÛncia de uniÒo de cimentos resinosos de dupla polimerizaþÒo associados a sistemas adesivos simplificados após 24 horas e 3 meses

This study evaluated the bonding compatibility between dualcuredresin cements and simplified adhesive systems (one-step self-etch and two-step etch & rinse), measured after 24 hours and 3 months. The occlusal dentin surfaces of 24 human third molars were exposed and flattened. Teeth were randomly assigned to 3 groups and treated with different combinations ofadhesive system and resin cement [G1 - Single Bond/Rely X ARC (SB/RX); G2 - Excite DSC/Variolink II (EX/VR); G3 -Adper Prompt/Rely X ARC (AD/RX)]. Indirect composite restorations were cemented on flattened surfaces, and sectioned to obtain multiple bonded beams for the microtensile bond strength test. The beams from each tooth were tested under tension after 24 hours and 3 months (ANOVA/ Tukeys test, α=5%). Failure patterns were evaluated with scanning electron microscopy. After 24h, AD/RX presented the lowest bond strength mean values. AD/RX specimens did not withstandthree months storage. SB/RX and EX/VR presented similar bond strengths in both periods tested. The associationAD/RX resulted in low bond strength mean values, especially after storage. Cementing indirect restorations using one-step self-etch adhesive systems and dual-cured resin cements wouldbe clinically unreliable.(AU)

Este estudo avaliou a compatibilidade de uniÒo entre cimentos resinosos de dupla polimerizaþÒo e sistemas adesivos simplificados (adesivo autocondicionante - 1 passo- e adesivo total-each - 2 passos), após 24h e 3 meses. A superfície oclusal de 24 terceiros molares humanos foi exposta e planificada. Os dentes foram aleatoriamente divididos em 3 grupos usados de acordo a seguinte combinaþÒo entre sistema adesivo/cimento resinoso [G1 - Single Bond/Rely X ARC (SB/RX); G2 - Excite DSC/Variolink II (EX/VR); G3-Adper Prompt/Rely X ARC (AD/RX)]. Restauraþ§es indiretas em resina composta foram cimentadas na superfície dentinária, e seccionados em múltiplos palitos para a realizaþÒo do teste de resistÛncia de uniÒo através do ensaio de microtraþÒo. Os palitos obtidos por dente foram submetidos ao teste após 24 horas e 3 meses (ANOVA/ Tukey test, α=5%). O padrÒo de fraturafoi observado no microscópio eletr¶nico de varredura. Após 24 horas, AD/RX apresentou menor valor médio de resistÛncia de uniÒo. Os corpos-de-prova do grupo AD/RX nÒo resistiram aoarmazenamento de 3 meses. SB/RX e EX/VR demonstraram similarresistÛncia de uniÒo em ambos os períodos avaliados. A associaþÒo AD/RX resultou em menores valores médios deresistÛncia de uniÒo, especialmente após o armazenamento. A cimentaþÒo de restauraþ§es indiretas utilizando sistemas autocondicionantes (1 passo) e cimentos resinosos de dupla polimerizaþÒo nÒo foi considerada clinicamente confiável.(AU)

Adhesive systems and secondary caries formation: Assessment of dentin bond strength, caries lesions depth and fluoride release.

OBJECTIVES: The present study evaluated the microtensile bond strength and caries formation on adhesive/dentin interfaces before and after dynamic chemical formation of secondary caries. METHODS: Restorations were prepared on the dentin surface of 80 bovine incisors using four adhesive systems: two fluoride-free (Single Bond and Clearfil SE Bond) and two fluoride containing (Optibond Solo Plus and Clearfil Protect Bond). The restored teeth were then sectioned into multiple slabs that were further trimmed at the bonded interface to a cross-sectional area of 1 mm2. Half of the slabs were subjected to secondary caries formation using a pH cycling model (treated groups); while the other half was used as the control group (no pH cycling). The specimens designated for bond strength evaluation were subjected to microtensile bond strength test (muTBS). Caries lesions formation was assesses by polarized light microscopy at different depths from the adhesive-dentin bonded interface. The fluoride ion concentration was evaluated using the de/remineralization solutions (De/Re). RESULTS: No differences in muTBS were observed among the adhesive systems in both the control and treated conditions. Secondary caries significantly reduced the values of muTBS for all adhesives (p<0.05). Optibond Solo Plus presented the lowest caries formation at 5 microm depth. Fluoride concentrations present in the De/Re were less than 0.03 ppm, regardless of the adhesive system tested. SIGNIFICANCE: Bond strength values significantly decreased after in vitro secondary caries formation. Fluoride present in adhesive systems is not capable of inhibiting secondary caries or maintaining bond strength values following caries formation.

Microhardness evaluation of in situ vital bleaching on human dental enamel using a novel study design.

OBJECTIVES: The aim of this 'in situ' study was to evaluate the microhardness of dental enamel following treatment with an in-office and an at-home vital bleaching agent through a novel approach using samples temporarily bonded 'in vivo'. METHODS: Human dental enamel slabs (n=88) were subjected to sequential polishing and initial Knoop microhardness tests were performed. The slabs were fixed to the facial surfaces of the maxillary first molars of 44 human volunteers. They were divided into four groups (n=11) according to the treatment group: G1- in-office-CP37+ at-home-CP10; G2- in-office-CP37+ at-home-PLA; G3- in-office-PLA and at-home-CP10; G4- in-office and at-home-PLA. After 3 weeks of treatment, final microhardness measurements were performed. RESULTS AND SIGNIFICANCE: ANOVA and Tukey's HSD hoc analysis (alpha=0.05) revealed no differences among initial or final microhardness values (p>0.05); however, significant differences occurred between initial and final values for each group (p<0.01), The evaluation of microhardness revealed a reduction of 6.8% for G1, 4.1% for G2, 3.4% for G3 and 3.5% for G4. In-office bleaching with 37% carbamide peroxide, an at-home bleaching with 10% carbamide peroxide, and a combination of both resulted in lower enamel microhardness when measured immediately post-treatment. However, long-term effects of these treatments are not known, and are believed to be clinically insignificant due to the relatively small reductions observed in enamel microhardness. Interestingly, the carrier, Cabopol 934P, also resulted in similar reduction in enamel microhardness even when administrated alone as a placebo.