Radiotherapy impairs adhesive bonding in permanent teeth.

OBJECTIVES: To evaluate the in vitro effects of radiotherapy (RT) on the morphological surface of the enamel and dentin and to determine the best adhesive system and most appropriate time to restore teeth in head and neck cancer patients. METHODS: Sixty third molars were cut into 120 enamel fragments and 120 dentin fragments and divided into four groups (n = 30): G1 (control): nonirradiated, only restorative procedure; G2: restorative procedure immediately before RT; G3: restorative procedure immediately after RT; and G4: restorative procedure 6 months after RT. Each group was divided into two subgroups: Adper™ Single Bond 2 (SB) and Clearfill SE Bond (CL) based on the material used. After RT and restorative procedures, the specimens were subjected to confocal microscopy and shear bond strength test. Data were analyzed using a two-way ANOVA followed by Tukey's test at a significance level of 5%. RESULTS: Morphological changes were observed in both substrates after a cumulative dose of 40 Gy, and after 60 Gy, the changes were more evident in both substrates. CL had the highest strength values in both substrates (p < 0.05), and G2 had the lowest strength values for the enamel and dentin (p < 0.05). CONCLUSIONS: Based on the in vitro study results, we can conclude that RT substantially changes the morphological surface of enamel and dentin and impairs the bond strength. The Clearfill system yielded better results than Adper Single Bond 2, and restoring teeth before RT resulted in the worst results in both substrates.

Effect of diode laser irradiation on the bond strength of polymerized non-simplified adhesive systems after 12 months of water storage

Abstract Objectives: The aim of this in vitro study was to evaluate the bonding strength of non-simplified dentin bonding systems (DBS) to dentin irradiated with a diode laser (970 nm) immediately and after 12 months of water storage following either primer or bond application. Material and methods: The experimental design included three different factors: DBS type [AdperTM Scotchbond Multipurpose (MP) and Clearfil™ SE Bond (CSE)], irradiation [without irradiation - control (C), irradiation after primer application (AP), and irradiation after bond application (AB)], and time [initial (I) and after 12 months of water storage (12 m)]. Sixty sound human third molars (n = 10) were obtained, and their flat occlusal dentin areas were prepared and standardized. Laser irradiation was performed in the contact mode perpendicular to the dental surface over an automatically selected scanning area at a pulse energy of 0.8 W, frequency of 10 Hz, and energy density of 66.67 J/cm2. After 7 days of treatment, the specimens were cut, and half of them were subjected to microtensile testing (500 N/0.05 mm/min), whereas the remaining sticks were examined after 12 months of water storage. The obtained data were analyzed by three-way analysis of variance (ANOVA) followed by a Tukey test (p<0.05). The observed fracture modes were investigated using a portable digital microscope with a magnification of 40x. Results: Among the utilized DBS, MP generally exhibited higher bond strengths, but did not always differ from CSE under similar conditions. The irradiation factor was statistically significant only for the MP/AB groups. After 12 months of storage, all groups demonstrated a significant reduction in the bond strength, whereas the results of fracture analysis showed a predominance of the adhesive type. Conclusions: The laser treatment of non-simplified DBS was not able to stabilize their bonding characteristics after 12 months.

Does laser diode irradiation improve the degree of conversion of simplified dentin bonding systems?

Abstract Simplified dentin-bonding systems are clinically employed for most adhesive procedures, and they are prone to hydrolytic degradation. Objective This study aimed to investigate the effect of laser diode irradiation on the degree of conversion (DC), water sorption (WS), and water solubility (WSB) of these bonding systems in an attempt to improve their physico-mechanical resistance. Material and Methods Two bonding agents were tested: a two-step total-etch system [Adper™ Single Bond 2, 3M ESPE (SB)] and a universal system [Adper™ Single Bond Universal, 3M ESPE (SU)]. Square-shaped specimens were prepared and assigned into 4 groups (n=5): SB and SU (control groups - no laser irradiation) and SB-L and SU-L [SB and SU laser (L) - irradiated groups]. DC was assessed using Fourier transform infrared spectroscopy with attenuated total reflectance. Additional uncured resin samples (≈3.0 µL, n=5) of each adhesive were also scanned for final DC calculation. For WS/WSB tests, similar specimens (n=10) were prepared and measured by monitoring the mass changes after dehydration/water storage cycles. For both tests, adhesive fluids were dropped into standardized Teflon molds (6.0×6.0×1.0 mm), irradiated with a 970-nm laser diode, and then polymerized with an LED-curing unit (1 W/cm2). Results Laser irradiation immediately before photopolymerization increased the DC (%) of the tested adhesives: SB-L>SB>SU-L>SU. For WS/WSB (μg/mm3), only the dentin bonding system (DBS) was a significant factor (p<0.05): SB>SU. Conclusion Irradiation with a laser diode improved the degree of conversion of all tested simplified dentin bonding systems, with no impact on water sorption and solubility.

Efeito da irradiação com laser de diodo sobre adesivos dentinários: estudo in vitro / Effect of diode laser irradiation on dentin-bonding agents

A irradiação de sistemas adesivos com laser tem obtido resultados promissores, no entanto, seu mecanismo de ação, bem como a longevidade da camada híbrida obtida após a irradiação com laser ainda não estão bem estabelecidos na literatura. A presente tese teve como objetivo: avaliar a absorvância do laser de Diodo por diferentes sistemas adesivos por meio de espectroscopia no infravermelho próximo; avaliar a evaporação de água e solventes proporcionada pelo laser por meio da variação da massa analisada em balança de precisão; avaliar a resistência de união por meio de teste de microtração após envelhecimento de 12 meses. Os dados obtidos foram analisados por modelos de ANOVA, seguidos de teste Tukey (p<0,05) e os resultados demonstraram que: a irradiação no infravermelho próximo, área do espectro eletromagnético que compreende o laser de Diodo, não apresenta interação com os sistemas adesivos testados; o laser de Diodo é capaz de proporcionar maior alteração de massa, mesmo após contínua evaporação dos solventes com jatos de ar por 60s; sistemas adesivos simplificados apresentaram valores de resistência de união imediato semelhantes aos valores obtidos após 12 meses de envelhecimento. Os dados obtidos neste estudo sugerem que a irradiação com laser de Diodo pode contribuir favoravelmente para a adesão em dentina com sistemas adesivos simplificados após 1 ano.(AU)

The laser irradiation of adhesive systems has obtained promising results, however, its mechanism of action, as well as the longevity of the hybrid layer obtained after laser irradiation are still not yet well established in the literature. This thesis aimed to: assess the diode laser interaction with different adhesive systems by means of near infrared spectroscopy; evaluate the evaporation of solvents and water provided by the laser through the mass variation analyzed at a precision balance; evaluate the bond strength through microtensile bond strength test after 12 months of aging. The data was analyzed through ANOVA models, followed by Tukey test (p<0.05), and the results demonstrated that: in the near-infrared irradiation area, the electromagnetic spectrum comprising the diode laser, shows no interaction with the adhesive systems tested; the diode laser was able to provide greater mass variation, even after continual evaporation of solvents with air jets for 60s; simplified adhesive systems presented immediate bond strength values similar to the ones verified after 12 months of aging. The data obtained in this study suggest that the Diode laser irradiation can contribute favorably for the adhesion between dentin and simplified adhesive systems after 1 year.(AU)

Temperature changes in the pulpal chamber and the sealing performance of various methods of direct pulp capping of primary teeth.

AIM: To compare changes in pulpal chamber temperature during the visible-light curing of direct pulp capping compounds and various modes of diode laser irradiation without prior placement of a pulp capping compound and the resultant seals. MATERIALS AND METHODS: Pulp exposure holes were made in 100 extracted human primary first molars, which were randomly assigned to ten equal groups. The holes were sealed by (a= Group 1, 2, 3, 4, 5, 6 and 7) different pulp capping compounds which were cured using various types of visible-light curing units or (b=Group 8, 9 and 10) diode laser irradiation without prior application of a pulp capping compound. Pulpal chamber temperatures were recorded during the procedure, and the resultant seals were examined under a scanning electron microscope. RESULTS: Visible-light curing of the pulp capping compounds and diode laser irradiation at a 0.7 W output power can cause non-injurious temperature rises in the pulpal chamber. At higher output powers of the diode laser, the temperature rises are sufficient to cause thermal injury. The seals were complete when pulp capping compounds were used for direct pulp capping, but were incomplete when laser irradiation without prior placement of a pulp capping compound was used for the identical purpose. CONCLUSION: The visible-light curing of pulp capping compounds is not harmful to vital pulp, and provides an effective seal of the pulp exposure hole. Laser irradiation is not an effective sealant, and can cause thermal injury to vital pulp at high output powers.

Impact of adhesive and photoactivation method on sealant integrity and polymer network formation

We evaluated the influence of photoactivation method and hydrophobic resin (HR) application on the marginal and internal adaptation, hardness (KHN), and crosslink density (CLD) of a resin-based fissure sealant. Model fissures were created in bovine enamel fragments (n = 10) and sealed using one of the following protocols: no adhesive system + photoactivation of the sealant using continuous light (CL), no adhesive system + photoactivation of the sealant using the soft-start method (SS), HR + CL, or HR + SS. Marginal and internal gaps and KHN were assessed after storage in water for 24 h. The CLD was indirectly assessed by repeating the KHN measurement after 24 h of immersion in 100% ethanol. There was no difference among the samples with regard to marginal or internal adaptation. The KHN and CLD were similar for samples cured using either photoactivation method. Use of a hydrophobic resin prior to placement of fissure sealants and curing the sealant using the soft-start method may not provide any positive influence on integrity or crosslink density.

Effects of ArF excimer laser irradiation of dentin on the tensile bonding strength to composite resin.

OBJECTIVE: The purpose of the study was to evaluate the effects of argon fluoride (ArF) excimer laser irradiation on the tensile bonding strength (TBS) of dentin to composite resin. BACKGROUND DATA: Dental lasers use a photothermal process, which potentially entails risk of tissue damage caused by heat affecting the bond strength of resins. The ArF excimer laser functions by a photochemical process in which the energy of photons directly cuts covalent bonds in molecules without generating heat. METHODS: Twenty extracted human molars were sectioned perpendicularly to the tooth axis to expose a flat dentin surface. The surfaces were treated with various combinations of ArF excimer laser irradiation, primer treatment, and bonding treatment. After composite resin was built up on the treated dentin surface, specimens with a 1×1 mm bonding interface were prepared and subjected to TBS tests. Treated dentin surfaces were also observed using transmission electron microscopy (TEM). RESULTS: Specimens that underwent laser irradiation followed by bonding treatment had a TBS that did not differ significantly from that of specimens that received conventional treatment, with or without priming. TEM observations showed sectioned and dispersed collagen matrix in the hybrid layer after laser irradiation, priming, and bonding, but no hybrid layer after laser irradiation and bonding at the treated dentin surface. CONCLUSIONS: The TBS of conditioning with ArF excimer laser irradiation was identical to that with conventional treatment when bonding was used. The bonding mechanism with the ArF irradiation differed from that of conventional bonding depending upon dentin hybridization.

Bond strength of dental adhesive systems irradiated with ionizing radiation.

PURPOSE: The aim of the present paper was to determine the effect of different types of ionizing radiation on the bond strength of three different dentin adhesive systems. MATERIALS AND METHODS: One hundred twenty specimens of 60 human teeth (protocol number: 032/2007) sectioned mesiodistally were divided into 3 groups according to the adhesives systems used: SB (Adper Single Bond Plus), CB (Clearfil SE Bond) and AP (Adper Prompt Self-Etch). The adhesives were applied on dentin and photo-activated using LED (Lec 1000, MMoptics, 1000 mW/cm2). Customized elastomer molds (0.5 mm thickness) with three orifices of 1.2 mm diameter were placed onto the bonding areas and filled with composite resin (Filtek Z-250), which was photo-activated for 20 s. Each group was subdivided into 4 subgroups for application of the different types of ionizing radiation: ultraviolet radiation (UV), diagnostic x-ray radiation (DX), therapeutic x-ray radiation (TX) and without irradiation (control group, CG). Microshear tests were carried out (Instron, model 4411), and afterwards the modes of failure were evaluated by optical and scanning electron microscope and classified using 5 scores: adhesive failure, mixed failures with 3 significance levels, and cohesive failure. The results of the shear bond strength test were submitted to ANOVA with Tukey's test and Dunnett's test, and the data from the failure pattern evaluation were analyzed with the Mann Whitney test (p = 0.05). RESULTS: No change in bond strength of CB and AP was observed after application of the different radiation types, only SB showed increase in bond strength after UV (p = 0.0267) irradiation. The UV also changed the failure patterns of SB (p = 0.0001). CONCLUSION: The radio-induced changes did not cause degradation of the restorations, which means that they can be exposed to these types of ionizing radiation without weakening the bond strength.

Effect of light-activation on the antibacterial activity of dentin bonding agents

Aim: This study evaluated the effect of light-activation on the antibacterial activity of dentin bonding systems. Methods: Inocula of Streptococcus mutans and Lactobacillus casei cultures were spread on the surface of BHI agar and the materials were applied and subjected or not to light-activation. Zones of bacterial growth inhibition around the discs were measured. Results: Excite, Single Bond and the bond of Clearfil SE Bond (SE) and Clearfil Protect Bond (CP) did not show any antibacterial activity. The strongest inhibitory activity was observed for the primers of CP and Prompt (PR) against S. mutans and the primers of SE andPB against L. casei. Conclusion: Light-activation significantly reduced or suppressed the antibacterial activity of the initially active uncured dentin bonding systems.

Effect of X-ray radiation dose on the bond strength of different adhesive systems to dentin.

PURPOSE: To investigate the influence of different x-ray radiation doses on the bond strength of adhesive restorations to dentin using different bonding strategies. MATERIALS AND METHODS: Flat dentin surfaces on human molars were obtained and cylinder-shaped specimens for the microshear bond test were built up with a composite (Z250, 3M ESPE), using three adhesive systems: a two-step etch-and-rinse (Single Bond 2--SB2, 3M ESPE), a two-step self-etching (Clearfil SE Bond--CSE, Kuraray), or a single-step self-etching (Adper Prompt--ADP, 3M ESPE). The specimens were assigned to 4 groups (n = 10), according to the x-ray dose: 0 (control), 5, 35, or 70 Gy. Radiation was directed to the surface of the resin cylinders. Microshear testing was conducted after 24 h, and the failure modes classified under magnification (200X). Data were submitted to two-way ANOVA and Holm-Sidak's test (p < or = 0.05). A nonlinear regression analysis was carried out with bond strength as dependent variable. RESULTS: Bond strength results were dose and material dependent. SB2: control > 5 = 35 > 70; CSE: control = 5 > 35 = 70; ADP: control = 5 = 35 = 70. Generally, SB2 > CSE > ADP. The nonlinear regression plots showed that in general, an increase in radiation dose may predict a decrease in bond strength (R2 > or = 0.905). Failure modes were dependent on the bonding system, generally with no significant influence of radiation. CONCLUSION: X-ray radiation might present a dose-dependent detrimental effect on the bond strength of resin composite restorations to dentin.

Effect of radiotherapy on the microleakage of adhesive systems.

PURPOSE: The aim of this in vitro study was to evaluate the effect of radiotherapy on the microleakage of three adhesive systems: a one-step self-etching, a two-step self-etching, and an etch-and-rinse system. MATERIALS AND METHODS: Box-shaped Class V cavity preparations were prepared on the buccal surfaces of 84 extracted human molars. The molars were randomly assigned into 6 groups (n = 14) according to the irradiation and adhesive system as follows: G1, Clearfil S3 Bond (irradiated); G2, Clearfil SE Bond (irradiated); G3, Prime & Bond NT (irradiated); G4, Clearfil S3 Bond (nonirradiated); G5, Clearfil SE Bond (nonirradiated); and G6, Prime & Bond NT (nonirradiated). The cavities were restored with composite resin (Filtek Z 250). After restoration of the samples, a total dose of 60 Gy was delivered in 2 Gy/d fractions for 5 days per week for 6 weeks for the related groups. All specimens were thermocycled for 200 cycles between 5 degrees C and 55 degrees C using a dwell time of 60 s in each bath and then placed in 0.5% basic fuchsin solution for 24 h at room temperature. Specimens were then rinsed and sectioned; the dye penetration at the enamel and dentin margins was examined using a stereomicroscope, and a score of 0 to 3 was assigned. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U-tests. RESULTS: No statistically significant difference existed between the irradiated and nonirradiated groups (p > 0.05). Significant differences in microleakage were observed between enamel and dentin (p < 0.01). The microleakage at the dentin margins was greater than at the enamel margins. Prime & Bond NT revealed statistically significantly (p < 0.05) higher leakage scores in dentin than did ClearfilS3 Bond and Clearfil SE Bond. CONCLUSION: Within the limitations of this study, irradiation application did not affect the microleakage of dental adhesive systems.

An in vitro evaluation of effect of ionizing radiotherapy on push-out strength of fiber posts under cyclic loading.

Ionizing radiotherapy has a deleterious effect on all vital cells and thus might affect the collagen fibril network of dentin and formation of hybrid layer of composite resins. The present study evaluated the effect of ionizing x-ray radiotherapy on push-out bond strength of fiber posts. Sixty mandibular premolar roots were divided into 4 groups: group I, control group with no irradiation, restored with a quartz fiber post system with cyclic loading; group II, samples were exposed to 60 Gy radiation dosage and than restored; group III, samples were restored and then irradiated; and group IV, samples were restored during irradiation. A push-out bond strength test was done. Radiotherapy significantly reduced the push-out bond strength of fiber posts. Patients undergoing ionizing radiotherapy might have a less than ideal prognosis of fiber posts luted with dual cure resin cement with total etch bonding system, if restorations are done after radiotherapy.

Effect of gamma irradiation on fluoride release and antibacterial activity of resin dental materials

This study evaluated the effect of gamma irradiation on fluoride release and antibacterial activity of FluroShield (FS) and Clearfil Protect Bond (CPB). Four groups were formed: G1-FS + gamma; G2-FS without gamma; G3-CPB + gamma; G4-CPB without gamma. For fluoride release analysis, 12 disks of each material were prepared and covered with nail polish, except for one side (50.4 mm² area). G1 and G3 were sterilized with a 14.5 KGy dose at 27ºC for 24 h, while G2 and G4 (controls) were not sterilized and were maintained under the same time and temperature conditions. Fluoride release measurements were made in duplicate (n=6) by an ion specific electrode. The antibacterial activity of the CPB and FS against Streptococcus mutans after gamma sterilization was evaluated by the agar-disc diffusion method. The diameter of the zones of microbial growth inhibition was recorded after 48 h. Data were analyzed statistically by ANOVA and Tukey's test (α=5 percent). Gamma sterilization decreased the fluoride release of FS by approximately 50 percent, while CPB was not affected. There was no statistically significant difference (p>0.05) in the antibacterial effect of CPB between gamma and non-gamma sterilization groups. FS presented no antibacterial activity. Gamma irradiation decreased the fluoride release of FS, but did not affect the antibacterial activity of the studied materials.

Este estudo avaliou o efeito da esterilização com raios-gama na liberação de flúor e atividade antibacteriana de materiais resinosos, Fluroshield (FS) e Clearfil Protect Bond (CPB). Quatro grupos foram formados: G1-FS e gama; G2-FS sem gama; G3-CPB e gama; G4-CPB sem gama. Doze discos de cada material foram preparados para análise de liberação de flúor, os quais foram cobertos com esmalte de unha, exceto em um lado com 50,4 mm² de área. G1 e G3 foram esterilizados com dose de 14,5 KGy por 24 h/27ºC, enquanto G2 e G4 (controles) não foram esterilizados e foram mantidos sob as mesmas condições de tempo e temperatura. As leituras de liberação de flúor foram feitas em duplicata (n=6) por um eletrodo específico. A atividade antibacteriana foi avaliada pelo teste de difusão em agar. Os halos de inibição foram medidos após 48 h. Os dados foram analisados pelos testes ANOVA e Tukey (α=5 por cento). A esterilização gama diminuiu a liberação de flúor de FS em cerca de 50 por cento, enquanto CPB não foi afetado. Não houve diferença estatisticamente significante entre os grupos esterilizados e controle no efeito antibacteriano do CPB. FS não apresentou atividade antibacteriana. A esterilização gama diminuiu a liberação de flúor de FS, mas não afetou a atividade antibacteriana dos materiais estudados.

Polymerization shrinkage stress of composites photoactivated by different light sources

The purpose of this study was to compare the polymerization shrinkage stress of composite resins (microfilled, microhybrid and hybrid) photoactivated by quartz-tungsten halogen light (QTH) and light-emitting diode (LED). Glass rods (5.0 mm x 5.0 cm) were fabricated and had one of the surfaces air-abraded with aluminum oxide and coated with a layer of an adhesive system, which was photoactivated with the QTH unit. The glass rods were vertically assembled, in pairs, to a universal testing machine and the composites were applied to the lower rod. The upper rod was placed closer, at 2 mm, and an extensometer was attached to the rods. The 20 composites were polymerized by either QTH (n=10) or LED (n=10) curing units. Polymerization was carried out using 2 devices positioned in opposite sides, which were simultaneously activated for 40 s. Shrinkage stress was analyzed twice: shortly after polymerization (t40s) and 10 min later (t10min). Data were analyzed statistically by 2-way ANOVA and Tukey's test (a=5 percent). The shrinkage stress for all composites was higher at t10min than at t40s, regardless of the activation source. Microfilled composite resins showed lower shrinkage stress values compared to the other composite resins. For the hybrid and microhybrid composite resins, the light source had no influence on the shrinkage stress, except for microfilled composite at t10min. It may be concluded that the composition of composite resins is the factor with the strongest influence on shrinkage stress.

Este estudo comparou a contração de polimerização de resinas compostas fotoativadas por luz halógena (QTH) e diodo emissor de luz (LED). Foram confeccionados bastões de vidro (5,0 mm x 5,0 cm), e uma de suas extremidades sofreu jateamento com óxido de alumínio, sobre a qual foi aplicado um adesivo e fotoativado com luz halógena. Os bastões de vidro foram acoplados verticalmente, em pares, em uma máquina universal de ensaios (EMIC DL-2000) e as resinas compostas aplicadas no bastão inferior. A distância entre os bastões foi padronizada em 2 mm e um extensômetro foi acoplado a eles. As resinas foram fotoativadas (n=20), sendo 10 por QTH e 10 por LED utilizando dois aparelhos posicionados em lados opostos, acionados simultaneamente por 40 s. A tensão de contração foi analisada em dois momentos: logo após a polimerização (t40s) e 10 min após (t10min). A tensão de contração apresentada por todas as resinas foi maior em t10min do que em t40s, independente da fonte ativadora. A resina de micropartículas apresentou menores valores de tensão de contração com valores estatisticamente significantes em relação às demais resinas. Para as resinas híbrida e microhíbrida não houve influência da unidade ativadora sobre a tensão de contração, com exceção para a resina de micropartículas em t10min. Concluiu-se que a composição da resina composta foi o fator que mais interferiu na tensão de contração da resina composta.

Effect of different modes of light modulation on the bond strength and knoop hardness of a dental composite

This study evaluated the bond strength and Knoop hardness of Z250 composite resin, light activated with XL2500 curing unit, using different protocols: continuous mode - high intensity (CH) (700 mW/cm²) for 20 s; continuous mode - low intensity (CL) (150 mW/cm²) for 20 s; and pulse-delay with 150 mW/cm² for 2(P2), 3(P3), 5(P5), 10(P10) or 15 s (P15), with a 1-min delay, followed by 700 mW/cm² for 20 s. For the push-out test (n=10), the bond strength values were obtained using a universal test machine at a crosshead speed of 0.5 mm/min. For Knoop hardness (n=5), the specimens were made using the same light-activation protocols. The hardness measurements were made with a hardness tester at six depths (top, 1, 2, 3, 4, and 5 mm). The data were subjected to ANOVA and Tukey's test at 5 percent significance level. For bond strength, CL and P5 presented significantly higher mean values (p<0.05) than the other groups. There was no statistically significant difference (p>0.05) between P2, P3, P10, P15 and CH. For Knoop hardness, CH and P15 presented the highest mean values from top surface up to 4 mm depth , while CL presented the lowest hardness mean values (p<0.05). From the depth of 3 mm to 5 mm, the mean values of all groups were significantly lower (p<0.05) than those recorded on top surface. In conclusion, for the pulse-delay method, the initial exposure time can influence bond strength and Knoop hardness of composites.

Este estudo verificou a resistência de união e a dureza Knoop do compósito Z250 (3M/ESPE), fotoativado com luz de lâmpada halógena (XL2500, 3M/ESPE), utilizando diferentes protocolos: modo contínuo alta intensidade (CH) (700mW/cm²) por 20s; modo contínuo baixa intensidade (CL) (150mW/cm²) por 20s; pulse-delay com 150mW/cm² por 2(P2), 3(P3), 5(P5), 10(P10) ou 15(P15) segundos, com 1 min de espera, seguido por 700mW/cm² por 20s. Para o teste de união push-out (n=10), os valores de resistência de união foram obtidos em máquina de ensaio universal Instron. Para o ensaio de dureza Knoop (n=5) os espécimes foram fotoativados pelos mesmos protocolos utilizados no ensaio de resistência de união. As medidas de dureza foram realizadas em um microdurômetro (Shimadzu) em 6 profundidades (topo, 1, 2, 3, 4 e 5 mm). Os dados foram submetidos à Análise de Variância e ao teste de Tukey com nível de significância de 5 por cento. Os resultados mostraram que P5 e CL apresentaram resistência de união estatisticamente superior a todos os grupos. Não houve diferença entre os grupos P2, P3, P10, P15 e CH. Para dureza Knoop, CH apresentou os maiores valores, estatisticamente superiores a P2 e CL até 4 mm. A partir de 3 mm, a dureza de todos os grupos foi inferior a dureza do topo. O tempo de exposição inicial para o modo pulse-delay pode influenciar a resistência de união e a dureza Knoop.

Effect of two light-emitting diode (LED) and one halogen curing light on the microleakage of Class V flowable composite restorations.

AIM: The disadvantages of light cured composite resin materials with respect to microleakage are predominantly a result of polymerization shrinkage upon curing. It has been shown curing methods play a significant role in polymerization shrinkage of light-cured composite resins. The purpose of this study was to investigate the effect of light-emitting diode (LED) light curing units (LCUs) compared with a halogen LCU on microleakage of three different flowable composites using self-etch adhesives. METHODS AND MATERIALS: A total of 63 extracted human premolars were prepared with standardized Class V cavity preparations on the buccal and lingual surfaces of each tooth. The occlusal margin of the cavities was located on the enamel and the gingival margin was on dentin. Teeth were randomly assigned to three groups of 21 teeth each as follows: Group 1: Adper Prompt L-Pop + Filtek Flow (3M ESPE); Group 2: AdheSE + Tetric Flow (Ivoclar, Vivadent); and Group 3: Clearfil Protect Bond + Clearfil Protect Liner F (Kuraray Medical Inc.). All the groups were subdivided into three groups according to the curing lights used (n=7). Two LED LCUs, Elipar FreeLight and Elipar FreeLight 2 (3M ESPE), and one halogen-based LCU, Hilux Expert (Benlioglu ), were used. All teeth were then immersed in 0.5% basic fuchsin dye solution for 24 hours after thermocycling (500 cycles; between 5 degrees C to 55 degrees C). The teeth then were longitudinally sectioned and observed under a stereomicroscope (40X magnification) by two examiners. The degree of dye penetration was recorded separately for enamel and dentin. Data were analyzed with the Kruskal-Wallis and Mann-Whitney tests with the Bonferroni correction. RESULTS: No statistically significant differences in microleakage were observed between groups either on enamel or dentin (p>0.05). CONCLUSION: With the limitation of this in vitro study, the differences in microleakage between LCUs used were not statistically significantly different. Elipar Free Light 2 reduces curing time which can be considered as an advantage.

Influence of radiation on bond strength.

PURPOSE: The aim of this in vitro study was to evaluate the shear bond strength of two adhesive systems--Prime & Bond NT (PBNT) and Clearfil SE Bond (CSEB)--to dentin irradiated before or after adhesive application. MATERIALS AND METHODS: Thirty extracted molars were sectioned mesiodistally with a diamond bur. The inner surface of each tooth's dentin was ground flat with SiC abrasive papers. The roots of the sectioned teeth were mounted in a cylindrical mold using chemically cured acrylic resin. In groups A1 and B1, a radiation dose of 60 Gy (R) was applied to the dentin surfaces at this point. In all groups, adhesives were applied according to the respective manufacturer's instructions. Cylindrical composite resin restorations (CRR; internal diameter 3 mm, height 4 mm) were then placed on the center of the flattened dentin surfaces. At this point, groups A2 and B2 received 60 Gy of radiation, and groups C1 and C2 remained as nonirradiated controls. Thus, the test groups were: A1: R + PBNT (Primed Bond NT) + CRR; A2: PBNT + CRR + R; B1: R + CSEB (Clearfil SE Bond) + CRR; B2: CSEB + CRR + R; C1: PBNT+ CRR; C2: CSEB+ CRR. Specimens were mounted in a universal testing machine and shear load was applied at a crosshead speed of 1 mm/min until failure. Bond strength values were calculated as MPa and the results were evaluated statistically using repeated measures of two-way ANOVA, with significance set at p < 0.05. RESULTS: Irradiation significantly affected adhesion of composite to dentin in groups A1 and A2 (p = 0.002). Group A1 showed statistically lower bond strength than group A2 (p < 0.05). No statistically significant differences were found among the other groups (p = 0.49). CONCLUSION: The time point of irradiation can have an adverse effect on bond strength, depending on the type of adhesive material.

Nd:YAG laser influence on microtensile bond strength of different adhesive systems for human dentin.

OBJECTIVE: The purpose of this study was to investigate the influence of Nd:YAG on microtensile bond strength (microTBS) of different adhesive systems for human dentin. BACKGROUND DATA: Lasers have been widely used in dentistry. New adhesive systems with different chemical compositions are introduced every year, and it is important to investigate the bonding of new adhesive systems to dentin irradiated with laser. METHODS: The occlusal surfaces of third molars were removed to obtain flat dentin surfaces. The teeth were randomly divided into six groups. Each adhesive system was applied, according to manufacturers' instructions, to surface dentine with and without Nd:YAG laser irradiation (0.9 W, 15 Hz, 60 mJ per pulse). A block of composite resin was built over the adhesive layer. The specimens were sectioned to obtain 0.70 x 0.70 mm of transversal section. Twenty test specimens were selected for each group, and were then submitted to microTBS on a universal testing machine. RESULTS: According to Student's t-test, for Single Bond, there was no statistically significant difference without (49.32 MPa) and with (47.34 MPa) laser application (p = 0.60). For the Tyrian SPE/One Step Plus, microTBS value with laser (27.09 MPa) was statistically higher than without laser (19.13 MPa), as well as for Adper Prompt L-Pop (22.85 and 13.78 Mpa; p < or = 0.01). CONCLUSION: The application of Nd:YAG laser to dentin provided an increase in the bond strength values for the Tyrian SPE/One Step Plus and Adper Prompt L-Pop adhesive systems, but did not influence the bond strength values of the Single Bond adhesive system.

Microtensile bond strength analysis of different adhesive systems and dentin prepared with high-speed and Er:YAG laser: a comparative study.

OBJECTIVE: The aim of this study was to evaluate the bond strength of two adhesive systems (Single Bond and Clearfil SE Bond) subjected or not to a thermocycling procedure and applied to cavities prepared either with high-speed diamond bur or Er:YAG laser. BACKGROUND DATA: One of the possible applications of dental lasers includes increasing the quality of bond strength. METHODS: This in vitro study was carried out using a microtensile test on 16 bovine teeth, divided into eight groups. Cavities were prepared on superficial dentin of the medium portion of the buccal surface. After application of adhesive systems, composite restorations were performed at 5-mm height. After 24 h, four groups of teeth were immersed in water, and the other four were thermocycled. Bonded specimens were sectioned into serial 1x1-mm beams, which were subjected to a microtensile test. Final values of bond strength were measured, expressed in MPa, and statistically analyzed. RESULTS: Results were as follows: G1 (26.281 +/- 5.454 MPa); G2 (10.965 +/- 3.714 MPa); G3 (18.549 +/- 6.113 MPa); G4 (14.295 +/- 3.806 MPa); G5 (18.225 +/- 5.701 MPa); G6 (5.588 +/- 2.211 MPa); G7 (18.256 +/- 3.819 MPa); and G8 (15.423 +/- 4.714 MPa). CONCLUSIONS: Self-etching adhesive system (SE) produced more stable bond strength results than the system that indicates total etching (SB). For dentin prepared at high speed, the total etching adhesive system was more indicated, whereas Er:YAG laser-preparation dentin was not influenced by the adhesive system. The thermocycling procedure could negatively affect microtensile bond strength of both adhesive systems, being more deleterious to SB than to SE.

Composite resin's adhesive resistance to dentin: influence of Er:YAG laser focal distance variation.

The aim of this study was to analyze in vitro the influence of Er:YAG laser focal distance variation on tensile bond strength of a composite resin to dentin. Although there are several studies using the Er:YAG laser for dentin treatment, there is a lack of available literature related to the Er:YAG laser focal distance variation. Sixty vestibular and lingual dentin surfaces from extracted human third molars, kept in a 0.4% azide sodium solution, were ground and assigned to six groups. The control group was conditioned with 35% phosphoric acid (CA). In the lased groups, the dentin surface treatment was performed by irradiation with Er:YAG laser (80 mJ/2 Hz), varying the focal distance (11, 12, 14, 16, and 17 mm), followed by acid etching. The Single Bond/Filtek Z250 (3M) resinous system was used for the specimen manufacture. The tensile bond strength tests were performed in a Universal Testing Machine with 50 kgf load cell and 0.5 mm/min cross head speed. The averages in MPa were: CA: 18.03 (+/-2.09); 11 mm; 9.92 (+/-3.34); 12 mm: 9.49 (+/-2.29); 14 mm: 10.99 (+/-3.45); 16 mm: 10.56 (+/-1.93); and 17 mm: 17.05 (+/-2.31). It was concluded that the application of Er:YAG laser in a defocused mode (17 mm) associated with acid etching was similar to the treatment of acid solely. Er:YAG laser irradiation in a focused (12 mm) and a defocused (11, 14, and 16 mm) mode coupled with acid conditioning produced the lowest values of adhesion.