Effect of argon plasma on repair bond strength using nanofilled and microhybrid composites.

OBJECTIVES: To evaluate the effect of atmospheric pressure plasma (PLA), sandblasting (SAN), silanization (SIL) and hydrophobic bonding resin (HBR) on the micro-shear bond strength (MSBS) of fresh nanofilled (NF) or microhybrid (MH) composites to water-aged nanofilled composite. MATERIALS AND METHODS: NF plates were fabricated and stored in distilled water for 4 months. The aged plates were assigned to the groups (n = 6): 1- untreated; 2- SAN + SIL + HBR; 3- HBR; 4- PLA + HBR; 5- SAN + HBR; 6- SAN + PLA + HBR; and 7- PLA. Two fresh composite cylinders were constructed on each plate with NF or MH composites and tested after 24 h or 1 year of water-storage, using the MSBS testing. Data were analyzed by three-way ANOVA and Tukey test (α = 0.05). RESULTS: NF yielded better outcomes than MH at 24 h, which was not observed at 1 year. HBR showed the highest MSBS results, while untreated and PLA groups yielded the lowest one. MSBS reduced for all groups after 1 year. CONCLUSIONS: Only HBR can obtain good MSBS results, while PLA alone was not beneficial. After 1 year, a reduction in repair MSBS was observed and the type of composite did not influence the results. CLINICAL RELEVANCE: The repair technique can be simplified with the use of only an adhesive and macromechanical retentions in the old composite, regardless the type of fresh composite.

Effect of indirect restorative material and thickness on light transmission at different wavelengths.

PURPOSE: The aim of this study was to evaluate the influence of indirect restorative material type and thickness on the transmission of different wavelengths from a broad-banded dental curing light. METHODS: Four dental indirect restorative materials for computer-aided design and computer-aided manufacturing (CAD/CAM) were evaluated: [RC] resin/ceramic hybrid material (Lava Ultimate), [FC] feldspathic ceramic (VitaBlocs), and two zirconia-based ceramics ([ZK] Katana; and [ZL] Lava). Total loss of irradiance (TL) was measured for blue (WB, 425-490nm) and violet (WV, 350-425nm) wavelengths. Specimens of 15×15mm with varying thicknesses (0.5, 1.0, 1.5, and 2.0mm) were fabricated (n=5). A plasma-arc dental light-curing unit was used (Arc Light-II). To assess TL as a function of wavelength, a software (Spectra Suite v5.1) connected to a spectroradiometer (USB2000) and an integrating sphere (CTSM-LSM-60-SF) was used. Data was subjected to statistical analysis (two-way ANOVA and post-hoc Tukey test, α=0.05). RESULTS: A 0.5mm interposition resulted in TL from 50.5 to 67.2%, depending on material. Increased thickness resulted in higher TL for all materials. FC showed less TL compared to ZK. In general, WV showed higher TL than did WB, and WV/WB proportion decreased with increasing thickness. CONCLUSIONS: Indirect materials significantly reduced TL, and this effect is greater with increasing thickness. WV showed lower penetration compared to WB.

Bond strength of composite resin containing biomaterial S-PRG to eroded dentin

To evaluate the bond strength of composite resin containing or not biomaterial (S-PRG) to sound/eroded dentine. Methods: Occlusal dentin of 30 human molars (n=15) had half of its surface kept uneroded, while on the other half an erosive lesion was produced by cycling in citric acid (pH 2.3) and supersaturated solution (pH 7.0). On both eroded (ED) and non-eroded (SD) substrates, two restorative systems (containing or not S-PRG) were tested. Composite resin cylinders were built and, after storage in water (24h), were submitted to bond strength test. The analysis of the fracture pattern was performed under an optical microscope (40x). The obtained values of bond strength (MPa) were submitted to ANOVA (two factors) and Tukey multiple comparisons tests (p<0.05). Results: According to the results, there was difference between substrates (<0.001) and restorative materials (p=0.002) evaluated. For the microtensile bond strength, the values obtained were: SDNB (47.6±12.2 MPa), SDWB (34.1±15.8 MPa), EDNB (31.1±8.3 MPa) and EDWB (15.5±13.6 MPa), revealing a statistically significant difference in the evaluated substrates and restorative materials. Conclusion: Bond strength of eroded substrate is inferior to the sound substrate and the restorative system containing S-PRG biomaterial influences negatively the results of bonding to sound/eroded dentin (AU)

Mini-interfacial Fracture Toughness of a Multimode Adhesive Bonded to Plasma-treated Dentin.

PURPOSE: To investigate the bonding efficacy of a multimode adhesive to plasma-treated and -untreated (control) dentin using a mini-interfacial fracture toughness (mini-iFT) test. MATERIALS AND METHODS: Twenty human molars were used in a split-tooth design (n = 10). The adhesive Scotchbond Universal (SBU; 3M ESPE) was applied in etch-and-rinse (E&R) and self-etch (SE) modes. Mid-coronal dentin was exposed and covered with a standardized smear layer ground to 320 grit. One half of each dentin surface received 15 s of non-thermal atmospheric plasma (NTAP), while the other half was covered with a metallic barrier and kept untreated. Following the E&R mode, dentin was plasma treated immediately after phosphoric acid etching. SBU and a resin-based composite were applied to dentin following the manufacturer's instructions. Six mini-iFT specimens were prepared per tooth (1.5 x 2.0 x 16 to 18 mm), and a single notch was prepared at the adhesive-dentin interface using a 150-µm diamond blade under water cooling. Half of the mini-iFT specimens were immediately loaded until failure in a 4-point bending test, while the other half were first stored in distilled water for 6 months. After testing, the exact dimensions of the notch were measured with a measuring optical microscope, from which ΚIc was determined. RESULTS: Three-way ANOVA revealed higher mini-iFT for SBU applied in E&R than SE mode for both storage times, irrespective of NTAP treatment. CONCLUSION: Overall, mini-iFT did not decrease for any of the experimental groups upon 6-month aging, while plasma treatment did not show a direct beneficial effect on mini-iFT of SBU applied in either E&R or SE mode.

Efeito do peróxido de hidrogênio na permeabilidade dental / Effects of hydrogen peroxide on dental permeability

Resumo Objetivo: Este trabalho avaliou o efeito de quatro agentes clareadores na permeabilidade dental. Material e Métodos: Dentes bovinos foram divididos em quatro grupos (n = 10). A permeabilidade inicial dos dentes foi determinada previamente ao clareamento, utilizando equipamento de permeabilidade. Em seguida, foram aplicados os géis clareadores e a permeabilidade novamente mensurada. Os resultados foram expressos em porcentagem de aumento da permeabilidade e os dados submetidos à análise estatística (ANOVA e teste Tukey). Resultados: O Whiteness HP Maxx resultou em maior aumento de permeabilidade (145,7±76,3), quando comparado com Whiteness HP Blue (57,5±36,1) e Pola Office Plus (72,7±19,5). Esses produtos não apresentaram diferença estatística com relação ao Opalescence Boost PF (101,4±46,3). Conclusão: Todos os agentes clareadores testados aumentaram a permeabilidade. A intensidade desse aumento foi dependente do produto utilizado.

Objective: This study evaluated the effect of four bleaching agents on the dental permeability. Material and Methods: Bovine teeth were divided into four groups (n=10), and the initial dental permeability was measured before the bleaching treatments, using a dental hydraulic permeability device. Afterwards, teeth were bleached with whitening products, and the final permeability was recorded. The results were expressed in percentage of increasing permeability (%) and data were submitted to ANOVA and Tukey's test. Results: Whiteness HP Maxx produced higher dental permeability (145.7±76.3) than Whiteness HP Blue (57.5±36.1) and Pola Office Plus (72.7±19.5), which did not differ from Opalescence Boost PF (101.4±46.3). Conclusion: All bleaching agents increased the dental permeability. The increasing intensity was product-dependent.

Short- and Long-term Evaluation of Dentin-Resin Interfaces Formed by Etch-and-Rinse Adhesives on Plasma-treated Dentin.

PURPOSE: To investigate the influence of atmospheric pressure plasma (APP) treatment on the microtensile dentin bond strength of two etch-and-rinse adhesive systems, after one week and one year of water storage, and additionally to observe the micromorphology of resin/dentin interfaces under scanning electronic microscopy (SEM). MATERIALS AND METHODS: The occlusal enamel was removed from third human molars to expose a flat dentin surface. The teeth were then randomly divided into six groups (n = 7), according to two adhesives (Optibond FL and XP-Bond) and three APP treatments (untreated dentin [control], APP application before or after acid etching). After performing the composite resin buildup on bonded dentin, the teeth were sectioned perpendicularly to the bonded interface to obtain beam-shaped specimens (cross-sectional area of ~0.9 mm2). The specimens were tested in tension until failure after one week and one year of water storage (1.0 mm/min rate). Bond strength data were analyzed by three-way ANOVA and Tukey's post-hoc test (α = 0.05%). Bonded beam specimens from each tooth were also prepared for interfacial SEM investigation. RESULTS: At one week, APP treatment applied after acid etching increased the dentin bond strength for XP Bond, while no effect was observed for Optibond FL. After one year, the bond strength of XP Bond decreased in groups where APP was applied after etching. The evaluation time did not influence the bond strength for Optibond FL. CONCLUSION: One-year evaluation did not show any sign of degradation of interfacial structures in any group. Application of APP to etched dentin combined with a two-step etch-and-rinse adhesive significantly increased bond strength at one week, but the effect was not stable after one year and was adhesive dependent.

Indirect Restoration Thickness and Time after Light-Activation Effects on Degree of Conversion of Resin Cement.

This study evaluated the effects of indirect restorative materials, curing conditions and time on the degree of conversion (DC) of a dual-cured resin cement using infrared spectroscopy. The resin cement (RelyX Unicem 2, 3M ESPE) was applied to the diamond surface of a horizontal attenuated-total-reflectance unit and activated using one of following conditions: self-cure, direct light exposure, light exposure through indirect restorative materials (resin nano-ceramic: Lava Ultimate, 3M ESPE or feldspathic ceramic: Vita Blocks Mark II, Vita Zahnfabrik). Four thicknesses (0.5, 1.0, 1.5 or 2.0 mm) of each indirect material were analyzed, and the light-activation was performed using a blue LED light. Data (n=5) were analyzed by three-way ANOVA, Tukey's post hoc and Dunnett's tests (α=5%). No significant differences in DC were observed between indirect materials of similar thickness. All groups exhibited higher DC after 10 min than after 5 min. At both times points, the self-cure group exhibited significantly lower DC than all the light exposure groups. Only when the overlying indirect restoration had a thickness of 2 mm did DC decrease significantly. The presence of a thick, indirect restoration can decrease the DC of resin cement. DC after 10 min was higher than after 5 min. The self-cure mode yielded lower DC than the light-activating one.

Indirect Restoration Thickness and Time after Light-Activation Effects on Degree of Conversion of Resin Cement

This study evaluated the effects of indirect restorative materials, curing conditions and time on the degree of conversion (DC) of a dual-cured resin cement using infrared spectroscopy. The resin cement (RelyX Unicem 2, 3M ESPE) was applied to the diamond surface of a horizontal attenuated-total-reflectance unit and activated using one of following conditions: self-cure, direct light exposure, light exposure through indirect restorative materials (resin nano-ceramic: Lava Ultimate, 3M ESPE or feldspathic ceramic: Vita Blocks Mark II, Vita Zahnfabrik). Four thicknesses (0.5, 1.0, 1.5 or 2.0 mm) of each indirect material were analyzed, and the light-activation was performed using a blue LED light. Data (n=5) were analyzed by three-way ANOVA, Tukey's post hoc and Dunnett's tests (α=5%). No significant differences in DC were observed between indirect materials of similar thickness. All groups exhibited higher DC after 10 min than after 5 min. At both times points, the self-cure group exhibited significantly lower DC than all the light exposure groups. Only when the overlying indirect restoration had a thickness of 2 mm did DC decrease significantly. The presence of a thick, indirect restoration can decrease the DC of resin cement. DC after 10 min was higher than after 5 min. The self-cure mode yielded lower DC than the light-activating one.

Este estudo avaliou os efeitos do tipo de material restaurador indireto, da condição de ativação e do tempo no grau de conversão de um cimento resinoso de dupla ativação, utilizando espectroscopia de luz infravermelha. O cemento resinoso (RelyX Unicem 2, 3M ESPE) foi aplicado à superfície do diamante da unidade de reflectância atenuada e ativado segundo as seguintes condições: ativação química, exposição direta da luz e aplicação da luz através de dois materiais protéticos: resina nano-cerâmica (Lava Ultimate, 3M ESPE) ou cerâmica feldspática (Vita Blocks Mark II, Vita Zahnfabrik). Quatro espessuras de cada um desses materiais (0,5; 1,0; 1,5 e 2,0 mm) foram analisadas e a ativação realizada com luz LED. Os dados (n=5) foram analisados pela ANOVA três fatores, testes de Tukey e Dunnett (5%). Nenhuma diferença do grau de conversão foi observada entre os materiais. Todos os grupos mostraram maior grau de conversão após 10 min que após 5 min. Em ambos os tempos, o grupo ativado quimicamente teve menor grau de conversão que todos os grupos fotoativados. O grau de conversão foi reduzido somente quando foi utilizada a peça protética de 2 mm. Espessas peças protéticas podem reduzir o grau de conversão do cemento resinoso. A grau de conversão após 10 min é maior que após 5 min da cimentação. A ativação química produz menor grau de conversão que a fotoativação.

Long-term Adhesion Study of Self-etching Systems to Plasma-treated Dentin.

PURPOSE: To determine the influence of atmospheric pressure plasma (APP) treatment on the microtensile dentin bond strength of two self-etching adhesive systems after one year of water storage as well as observe the contact angle changes of dentin treated with plasma and the micromorphology of resin/dentin interfaces using SEM. MATERIALS AND METHODS: For contact angle measurements, 6 human molars were sectioned to remove the occlusal enamel surface, embedded in PMMA resin, and ground to expose a flat dentin surface. Teeth were divided into two groups: 1) argon APP treatment for 30 s, and 2) blown air (control). For the microtensile test, 28 human third molars were used and prepared similarly to contact angle measurements. Teeth were randomly divided into 4 groups (n = 7) according to two self-etching adhesives and APP treatment (with/without). After making the composite resin buildup, teeth were sectioned perpendicular to the bonded interface to obtain beam specimens. The specimens were tested after 24 h and one year of water storage until failure. Bond strength data were analyzed by three-way ANOVA and Tukey's post-hoc test (α = 0.05%). Three beam specimens per group that were not used in the bond strength test were prepared for interfacial SEM analysis. RESULTS: APP application decreased the contact angle, but increased the bond strength only for one adhesive tested. SEM evaluation found signs of degradation within interfacial structures following 1-year aging in water. APP increased the dentin surface energy, but the effects of APP and 1-year water storage on dentin bond strength were product dependent. CONCLUSION: APP increased the dentin surface energy. It also increased the bond strength for Scotchbond Universal, but storage for one year negated the positive effect of APP treatment.

Effect of Different In Vitro Aging Methods on Color Stability of a Dental Resin-Based Composite Using CIELAB and CIEDE2000 Color-Difference Formulas.

PURPOSE: To evaluate the effect of different in vitro aging methods on color change (CC) of an experimental dental resin-based composite using CIELAB (ΔEab ) and CIEDE2000 (ΔE00 ) color-difference formulas. MATERIALS AND METHODS: The CC was evaluated with a spectrophotometer (CM700d, Konica Minolta, Tokyo, Japan) according to the CIE chromatic space. Disk-shaped specimens (Φ = 5 × 1 mm thick) (N = 10) were submitted to different in vitro aging methods: 30 days of water aging (WA); 120 hours of ultraviolet light aging (UVA); or 300 hours of an accelerated artificial aging (AAA) method with cycles of 4 hours of UV-B light exposure and 4 hours of moisture condensation to induce CC. The temperature was standardized at 37°C for all aging methods. CC was evaluated with ΔEab and ΔE00 formulas. Differences in individual Lab coordinates were also calculated. Data for the individual color parameters were submitted to one-way analysis of variance and Tukey's test for multiple comparisons (α = 0.05). RESULTS: All in vitro aging methods tested induced CC, in the following order: WA: ΔEab = 0.83 (0.1); ΔE00 = 1.15 (0.1) < AAA: ΔEab = 5.64 (0.2); ΔE00 = 5.01 (0.1) < UVA: ΔEab = 6.74 (0.2); ΔE00 = 6.03 (0.4). No changes in L* or a* coordinates were ≥1; the methods with UV aging showed a yellowing effect due a large positive change in b*. CONCLUSIONS: All in vitro aging methods tested induced a CC, but to different extents. Changes in color followed similar trends, but with different absolute values when calculated with the CIELAB and the CIEDE2000 formulas. CLINICAL SIGNIFICANCE: Establishing the efficacy of different artificial aging methods and differences between color change using CIELAB and CIEDE2000 formulas are important to standardize color stability evaluations and facilitate the comparison of outcomes from different studies in the literature.

Effect of peroxide bleaching on the biaxial flexural strength and modulus of bovine dentin.

OBJECTIVE: This study evaluated the effects of carbamide peroxide and hydrogen peroxide on the biaxial flexural strength and flexural modulus of bovine dentin. MATERIALS AND METHODS: Thirty coronal dentin disks (0.5 mm thick × 6.0 mm diameter) were prepared from bovine teeth. The disks were randomly divided into three groups (n=10): A control group (unbleached), a group bleached with 10% carbamide peroxide (8 h at 37°C), and a group bleached with 38% hydrogen peroxide (three 10 min applications at 37°C). The specimens were tested in a biaxial flexural apparatus held in a universal testing machine at 1.27 mm/min until failure occurred, and the biaxial mechanical properties were calculated. For each test parameter, the data were statistically analyzed by Fisher's PLSD test (predetermined α = 0.05). RESULTS: The group bleached with 38% hydrogen peroxide demonstrated significantly lower flexural strength than the unbleached control group. Hydrogen peroxide treatment resulted in a significantly lower flexural modulus compared with the control group and with carbamide peroxide bleaching. CONCLUSION: Exposure of dentin to hydrogen peroxide significantly reduced both the flexural strength and the flexural modulus compared with the no-treatment control, whereas exposure to carbamide peroxide did not significantly affect either parameter.

Self-etch adhesive systems: a literature review.

This paper presents the state of the art of self-etch adhesive systems. Four topics are shown in this review and included: the historic of this category of bonding agents, bonding mechanism, characteristics/properties and the formation of acid-base resistant zone at enamel/dentin-adhesive interfaces. Also, advantages regarding etch-and-rinse systems and classifications of self-etch adhesive systems according to the number of steps and acidity are addressed. Finally, issues like the potential durability and clinical importance are discussed. Self-etch adhesive systems are promising materials because they are easy to use, bond chemically to tooth structure and maintain the dentin hydroxyapatite, which is important for the durability of the bonding.

Self-Etch Adhesive Systems: A Literature Review

This paper presents the state of the art of self-etch adhesive systems. Four topics are shown in this review and included: the historic of this category of bonding agents, bonding mechanism, characteristics/properties and the formation of acid-base resistant zone at enamel/dentin-adhesive interfaces. Also, advantages regarding etch-and-rinse systems and classifications of self-etch adhesive systems according to the number of steps and acidity are addressed. Finally, issues like the potential durability and clinical importance are discussed. Self-etch adhesive systems are promising materials because they are easy to use, bond chemically to tooth structure and maintain the dentin hydroxyapatite, which is important for the durability of the bonding.

Este artigo apresenta o estado da arte de sistemas adesivos autocondicionantes. Quatro temas são apresentados nesta revisão: o histórico desta categoria de agentes de união, o mecanismo de adesão, as características/propriedades, e a formação da zona ácido-base resistente nas interfaces esmalte/dentina-adesivo. Além disso, as vantagens relativas aos sistemas de condicionamento total ( etch-and-rinse ) e as classificações dos sistemas adesivos autocondicionantes de acordo com o número de passos e acidez são abordados. Por fim, são discutidas questões como a durabilidade potencial e a importância clínica. Sistemas adesivos autocondicionantes são materiais promissores porque são fáceis de usar, unem-se quimicamente à estrutura do dente e preservam a hidroxiapatita dentinária, o que é importante para a durabilidade da ligação.

Bond strength of self-adhesive resin cements to dry and moist dentin.

This study evaluated the effects of humidity conditions and evaluation times on the dentin bond strength (DBS) of two self-adhesive resin cements (RC). The RC used were: RelyX Unicem (3M ESPE) and Clearfil SA Cement (Kuraray Med.). One hundred and twenty coronal portions of bovine incisors (n = 10) were used. Buccal surfaces were abraded in order to expose a flat dentinal surface (180-grit SiC) and to standardize the smear layer formation (600-grit SiC). The humidity conditions tested were: dry (air-dried for 10 s), slightly moist (water application with disposable applicator on dried dentin and water excess removed with absorbent paper), and moist (same application without water removal). The RC were used according to the manufacturers' recommendations and were applied to prepolymerized resin discs (2 mm thick; Sinfony, 3M ESPE), which were subsequently bonded to the dentin surfaces. After 24 h, half of the teeth were prepared for the microtensile bond strength test, while the other half were stored in water for 6 months and tested in tension (0.5 mm/min) until failure. A 3-way analysis of variance and the Tukey test were performed (preset alpha of 0.05). No RC showed any reduction of DBS after 6 months, and no significant difference was observed between them. The moist dentin increased the bond strength of Clearfil SA Cement for both periods of time. Humidity conditions can change the DBS; however, the study's results were product-dependent.

Bond strength of self-adhesive resin cements to dry and moist dentin

This study evaluated the effects of humidity conditions and evaluation times on the dentin bond strength (DBS) of two self-adhesive resin cements (RC). The RC used were: RelyX Unicem (3M ESPE) and Clearfil SA Cement (Kuraray Med.). One hundred and twenty coronal portions of bovine incisors (n = 10) were used. Buccal surfaces were abraded in order to expose a flat dentinal surface (180-grit SiC) and to standardize the smear layer formation (600-grit SiC). The humidity conditions tested were: dry (air-dried for 10 s), slightly moist (water application with disposable applicator on dried dentin and water excess removed with absorbent paper), and moist (same application without water removal). The RC were used according to the manufacturers' recommendations and were applied to prepolymerized resin discs (2 mm thick; Sinfony, 3M ESPE), which were subsequently bonded to the dentin surfaces. After 24 h, half of the teeth were prepared for the microtensile bond strength test, while the other half were stored in water for 6 months and tested in tension (0.5 mm/min) until failure. A 3-way analysis of variance and the Tukey test were performed (preset alpha of 0.05). No RC showed any reduction of DBS after 6 months, and no significant difference was observed between them. The moist dentin increased the bond strength of Clearfil SA Cement for both periods of time. Humidity conditions can change the DBS; however, the study's results were product-dependent.

Laminados cerâmicos: estética e naturalidade / Ceramic veneers: natural lifelike esthetic appearance

O uso de laminados cerâmicos para a restauração de dentes anteriores é cada vez mais atual na Odontologia. Em função das propriedades ópticas semelhantes à estrutura dentária, tem-se conseguido resultados naturais, realizando o mínimo ou nenhum desgaste dental. Dessa forma, este relato de caso clínico teve por objetivo descrever a resolução estética do sorriso através de laminados cerâmicos, discutindo indicações e características, assim como as técnicas empregadas para o resultado estético final

Avaliação da microdureza do esmalte dental bovino após técnicas de clareamento caseiro, de consultório e a associação das técnicas com agentes de baixa e alta concentração de peróxidos / Microhardness evaluation of bovine enamel after take-home, in-office tooth whitening techniques, and the association techniques using low and high concentration of peroxides

O objetivo deste estudo foi avaliar os efeitos das técnicas de clareamento caseiro com peróxido de carbamida a 16% (PC), de consultório com peróxido de hidrogênio a 35 ou 37,5% (PH) ou da associação das técnicas de clareamento com PH e PC na microdureza de superfície do esmalte de dentes bovinos. Superfícies vestibulares de 70 incisivos foram preparadas para leitura de microdureza de superfície inicial e divididas em 6 grupos experimentais e um controle sem clareamento (n = 10). Os PC foram aplicados por 8 horas/dia (durante 14 dias) e os PH foram utilizados em 3 sessões com intervalo de 4 dias entre cada sessão, com 3 aplicações do produto por sessão (12 minutos para cada aplicação). Nos grupos com associação dos peróxidos, os protocolos de clareamento foram: 1 sessão de PH + 14 dias PC a 16%. Após o término dos tratamentos, as amostras foram submetidas a uma nova leitura da microdureza de superfície. Os dados obtidos foram submetidos à ANOVA 2 fatores e teste de Tukey (5%). O tratamento clareador com PC 16% Whitegold Home e a associação com o PH Whitegold Office (PH 35%) resultaram na redução da microdureza do esmalte. O uso dos produtos Pola Night (PC 16%), Pola Office (37,5%) e a associação desses não alteraram a microdureza do esmalte. A redução da microdureza do esmalte pelo uso de agentes clareadores, assim como pela associação dos peróxidos de baixa e alta concentração, foi material dependente.

The objective of this study was to evaluate the effects of take-home bleaching using 16% carbamide peroxide (CP), in-office tooth whitening using 35 or 37.5% hydrogen peroxide (HP), or the association take-home and inoffice bleaching techniques on superficial microhardness of bovine enamel. The buccal surfaces of 70 bovine incisors were prepared for initial microhardness measurements and divided in 6 experimental and 1 unbleached control group (n = 10). The CPs were applied for 8 hours/daily during 14 days. The HPs were used in three appointments with 4-day intervals among sessions and this process was repeated 3 times (12 minutes each application). For the groups with the association of techniques, the bleaching protocol was: one session with HP plus 14 days of takehome bleaching. At the end of bleaching, the samples were submitted to the final hardness measurements. The data were analyzed by 2 ANOVA and Tukey test (5%). The take-home bleaching with 16% CP (Whitegold Home) and its association with Whitegold Office (HP 35%) reduced the enamel microhardness. The use of Pola Night (16% PC), Pola Office (37.5% HP) and their association did not alter the microhardness values. The reduction in enamel microhardness promoted by bleaching agents, as well as the association of techniques was product-dependent.