Enamel shear bond strength of two orthodontic self-etching bonding systems compared to Transbond™ XT.

OBJECTIVE: The aim of this in vitro study was to compare the shear bond strength (SBS) and Adhesive Remnant Index (ARI) scores of two self-etching no-mix adhesives (Prompt L-Pop™ and Scotchbond™) for orthodontic appliances to the commonly used total etch system Transbond XT™ (in combination with phosphoric acid). MATERIALS AND METHODS: In all, 60 human premolars were randomly divided into three groups of 20 specimens each. In group 1 (control), brackets were bonded with Transbond™ XT primer. Prompt L-Pop™ (group 2) and Scotchbond™ Universal (group 3) were used in the experimental groups. Lower premolar brackets were bonded by light curing the adhesive. After 24 h of storage, the shear bond strength (SBS) was measured using a Zwicki 1120 testing machine. The adhesive remnant index (ARI) was determined under 10× magnification. The Kruskal-Wallis test was used to statistically compare the SBS and the ARI scores. RESULTS: No significant differences in the SBS between any of the experimental groups were detected (group 1: 15.49 ± 3.28 MPa; group 2: 13.89 ± 4.95 MPa; group 3: 14.35 ± 3.56 MPa; p = 0.489), nor were there any significant differences in the ARI scores (p = 0.368). CONCLUSIONS: Using the two self-etching no-mix adhesives (Prompt L-Pop™ and Scotchbond™) for orthodontic appliances does not affect either the SBS or ARI scores in comparison with the commonly used total-etch system Transbond™ XT. In addition, Scotchbond™ Universal supports bonding on all types of surfaces (enamel, metal, composite, and porcelain) with no need for additional primers. It might therefore be helpful for simplifying bonding in orthodontic procedures.

Bond strength of metal brackets bonded to a silica-based ceramic with light-cured adhesive : Influence of various surface treatment methods.

OBJECTIVE: The purpose of this work was to evaluate the effects of several surface treatment methods on the shear bond strengths of metal brackets bonded to a silica-based ceramic with a light-cured adhesive. MATERIALS AND METHODS: Silica-based ceramic (IPS Classic(®)) with glazed surfaces was cut into discs that were used as substrates. A total of 80 specimens were randomly divided into four groups according to the method used: 9.6 % hydrofluoric acid (group 1), 9.6 % hydrofluoric acid (HF) + silane coupling agent (group 2), sandblasting (aluminum trioxide, 50 µm) + silane (group 3), and tribochemical silica coating (CoJet™ sand, 30 µm) + silane (group 4). Brackets were bonded to the treated specimens with a light-cure adhesive (Transbond XT, 3 M Unitek). Shear bond strength was tested after bracket bonding, and the Adhesive Remnant Index (ARI) scores were quantified after debonding. RESULTS: Group 4 showed the highest bond strength (12.3 ± 1.0 MPa), which was not significantly different from that of group 3 (11.6 ± 1.2 MPa, P > 0.05); however, the bond strength of group 4 was substantially higher than that of group 2 (9.4 ± 1.1 MPa, P < 0.05). The shear bond strength of group 1 (3.1 ± 0.6 MPa, P< 0.05) was significantly lower than that of the other groups. CONCLUSION: Shear bond strengths exceeded the optimal range of ideal bond strength for clinical practice, except for the isolated HF group. HF acid etching followed by silane was the best suited method for bonding on IPS Classic(®). Failure modes in the sandblasting and silica-coating groups revealed signs of damaged ceramic surfaces.

Different pulse modes of Er:YAG laser irradiation: effects on bond strength achieved with self-etching primers.

OBJECTIVE: The aim of this study was to compare the effects of different pulse modes of Er:YAG laser on shear bond strength (SBS) of orthodontic brackets bonded with self-etching primers (SEP) and phosphoric acid etching. MATERIALS AND METHODS: A total of 120 human mandibular third molars were randomly assigned to 3 groups of 40 specimens depending on the bonding procedure to be used. The groups were divided into two subgroups according to the pulse mode of the erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiation as medium-short pulse (MSP) mode and quantum-square pulse (QSP) mode at 120 mJ, 10 Hz, 1.2 W. In each subgroup, the mesio- or distobuccal tooth surfaces were randomly assigned as experimental or control sides. After surface preparation with different modes of Er:YAG laser on experimental side, whole buccal tooth surfaces were treated with phosphoric acid etching or two different SEPs. Then metallic brackets were bonded with Transbond XT (3 M Unitek, Monrovia, CA, USA) or Kurasper F (Kuraray, Okayama, Japan). SBS values and the amount of adhesive remaining on the tooth after debonding were assessed. One-way analysis of variance (ANOVA) was used to evaluate the changes in mean SBS between groups resulting from laser etching, followed by post hoc test of Tukey. RESULTS: There were statistically significant differences between the experimental and control sides of all groups (p < 0.05). CONCLUSION: Laser etching with QSP and MSP modes increases the SBS of metallic brackets and Er:YAG laser irradiation with QSP mode increases the SBS of SEPs.

Phototriggered fibril-like environments arbitrate cell escapes and migration from endothelial monolayers.

Cell detachment and migration from the endothelium occurs during vasculogenesis and also in pathological states. Here, we use a novel approach to trigger single cell release from an endothelial monolayer by in-situ opening of adhesive, fibril-like environment using light-responsive ligands and scanning lasers. Cell escapes from the monolayer were observed on the fibril-like adhesive tracks with 3-15 µm width. The frequency of endothelial cell escapes increased monotonically with the fibril width and with the density of the light-activated adhesive ligand. Interestingly, treatment with VEGF induced cohesiveness within the cell layer, preventing cell leaks. When migrating through the tracks, cells presented body lateral reduction and nuclear deformation imposed by the line width and dependent on myosin contractility. Cell migration mode changed from mesenchymal to amoeboid-like when the adhesive tracks narrowed (≤5 µm). Moreover, cell nucleus was shrunk showing packed DNA on lines narrower than the nuclear dimensions in a mechanisms intimately associated with the stress fibers. This platform allows the detailed study of escapes and migratory transitions of cohesive cells, which are relevant processes in development and during diseases such as organ fibrosis and carcinomas.

Influence of different Er,Cr:YSGG laser parameters on long-term dentin bond strength of self-etch adhesive.

The aim of the present study was to evaluate the effects of erbium, chromium: yattrium-scandium-gallium-garnet (Er,Cr:YSGG) laser frequency on microtensile bond strength (µTBS) of a self-etch adhesive to dentin after 15-month water storage. The Er,Cr:YSGG laser can safely be used on dental hard tissue. However, no study has compared the effects of Er,Cr:YSGG laser parameters and aging by water storage on the bonding effectiveness of self-etch adhesives to dentin. Thirty-five bovine teeth were randomly assigned to the following seven groups (n = 5): group I (diamond bur with high-speed handpiece (control)), group II (Er,Cr:YSGG laser 3 W/50 Hz), group III (Er,Cr:YSGG laser 3 W/35 Hz), group IV (Er,Cr:YSGG laser 3 W/20 Hz), group V (Er,Cr:YSGG laser 6 W/50 Hz), group VI (Er,Cr:YSGG laser 6 W/35 Hz), and group VII (Er,Cr:YSGG laser 6 W/20 Hz). Clearfil SE Bond was applied to the prepared dentin, and the composites were placed and cured. Resin-dentin sticks with an approximate cross-sectional area of 0.8 mm(2) were obtained, and bond strength tests were performed at 24 h and 15 months of water storage after bonding. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests (p < 0.05). Laser irradiation resulted in significantly lower bond strengths when compared to bur treating. Fifteen-month water storage reduced bond strength for all groups. There was no significant difference among the effects of different laser frequencies on bond strength. It can be concluded that Er,Cr:YSGG laser used at the tested parameters may alter the dentin bond durability of self-etch adhesive.

Physicochemical modifications accompanying UV laser induced surface structures on poly(ethylene terephthalate) and their effect on adhesion of mesenchymal cells.

This work reports on the formation of different types of structures on the surface of polymer films upon UV laser irradiation. Poly(ethylene terephthalate) was irradiated with nanosecond UV pulses at 193 and 266 nm. The polarization of the laser beam and the irradiation angle of incidence were varied, giving rise to laser induced surface structures with different shapes and periodicities. The irradiated surfaces were topographically characterized by atomic force microscopy and the chemical modifications induced by laser irradiation were inspected via micro-Raman and fluorescence spectroscopies. Contact angle measurements were performed with different liquids, and the results evaluated in terms of surface free energy components. Finally, in order to test the influence of surface properties for a potential application, the modified surfaces were used for mesenchymal stem cell culture assays and the effect of nanostructure and surface chemistry on cell adhesion was evaluated.

Photocrosslinkable bioadhesive based on dextran and PEG derivatives.

In this study, a hybrid photopolymeric bioadhesive system consisting of urethane methacrylated dextran (Dex-U) and 3, 4-Dihydroxyphenyl-l-alanine (DOPA) modified three-arm poly (ethylene glycol) s (PEG-DOPAs) was designed. The process of photopolymerization was detected by Photo-Differential Scanning Calorimetry (Photo-DSC). The adhesion strength was evaluated by the lap shear tests. The surface tension of the solutions, burst pressures and the cytotoxicity assays were also investigated. The addition of PEG-DOPAs significantly improved the properties of Dex-U especially in the field of adhesion strength and burst pressure. And materials variation could be tailored to match the demands for tissue repair. Compared to the Dex-U systems, the maximum adhesion strength of the copolymeric system increased from 2.7±0.1 MPa to 4.0±0.6 MPa. Owing to its strong adhesion strength, rapid curing rate and good biocompatibility, such photocrosslinkable hydrogelsa could be applied to the areas of bioadhesive.

Evaluation of self-etching adhesive and Er:YAG laser conditioning on the shear bond strength of orthodontic brackets.

The purpose of this study was to evaluate the shear bond strength, the adhesive remnant index scores, and etch surface of teeth prepared for orthodontic bracket bonding with self-etching primer and Er:YAG laser conditioning. One hundred and twenty bovine incisors were randomly divided into four groups. In Group I (Control), the teeth were conditioned with 35% phosphoric acid for 15 seconds. In Group II the teeth were conditioned with Transbond Plus SEP (5 sec); III and IV were irradiated with the Er:YAG 150 mJ (11.0 J/cm²), 150 mJ (19.1 J/cm²), respectively, at 7-12 Hz with water spray. After surface preparation, upper central incisor stainless steel brackets were bonded with Transbond Plus Color Change Adhesive. The teeth were stored in water at 37°C for 24 hours and shear bond strengths were measured, and adhesive remnant index (ARI) was determined. The conditioned surface was observed under a scanning electron microscope. One-way ANOVA and chi-square test were used. Group I showed the significantly highest values of bond strength with a mean value of 8.2 megapascals (MPa). The lesser amount of adhesive remnant was found in Group III. The results of this study suggest that Er:YAG laser irradiation could not be an option for enamel conditioning.

Hybrid nanocomposite films for laser-activated tissue bonding.

We report new advancements in the biomedical exploitation of plasmonic nanoparticles as an effective platform for the photothermal repair of biological tissue. Chitosan films are loaded with gold nanorods with intense optical absorption in the "therapeutic window" of deepest light penetration through the body, and then activated by near infrared laser excitation to give adhesion with adjacent connective tissues. The adhesion consists of 0.07 mm(2) welds of ~20 kPa tensile strength at the film/tissue interface, which are obtained by administration of pulses with duration in the hundreds of millisecond timescale from a diode laser at ~130 J cm(-2). We investigate the adhesive effect as a function of pulse power and duration and identify an optimal operative window to achieve effective and reproducible welds with minimal detrimental superheating. These results may prove valuable to standardize laser bonding techniques and meet current needs for new knowledge which is urged by the penetration of nanotechnology into biomedical optics.

Effects of functional monomers and photo-initiators on the degree of conversion of a dental adhesive.

Besides functional and cross-linking monomers, dental adhesives contain a photo-initiator system for polymerization, thereby providing physico-mechanical strength to the adhesive-tooth interface. Few studies have investigated the effect of the functional monomer and polymerization-initiation system on the polymerization efficiency of the adhesive. Here, we tested the effect of two different functional monomers (MAC-10 vs. SR) and two photo-initiator systems, camphorquinone-amine (CQ) vs. borate (BO), on the degree of conversion (DC) of different adhesive formulations. The DC of the CQ-cured adhesive formulations was significantly affected by the MAC-10 monomer. This should be ascribed to the known inactivation of the amine co-initiator through acid-base reaction. However, the SR monomer did not decrease the DC, which could be attributed to a "gel effect" or the so-called "Trommsdorff-Norrish" phenomenon of enhanced DC with more viscous resins, and to the more favorable availability of CC double bonds. In contrast, the DC of the BO-cured adhesive formulations was not affected by any acidic monomer. It is concluded that the degree of conversion of an adhesive can be affected by the functional monomer, but this depends on the kind of photo-initiator system used. As bond durability depends, among other factors, on the strength and thus degree of conversion of the adhesive, potential interaction between adhesive ingredients and the photo-initiator system definitely needs to be studied further.

Effect of ultrasonic excitation on the microtensile bond strength of glass ionomer cements to dentin after different water storage times.

The application of ultrasound waves on glass ionomer cement (GIC) surface can accelerate the early setting reaction and improve the mechanical properties of the material, resulting in higher resistance to masticatory forces within a short period of time and thus increasing the clinical longevity of the GIC restoration. In this study, the microtensile bond strength (µTBS) of two high-viscosity GICs (Fuji IX GP and Ketac Molar Easymix) and one resin-modified GIC (RMGIC-Vitremer) to dentin was tested after ultrasonic excitation and water storage. GIC blocks were built up on coronal dentin either receiving or not receiving a 30-s ultrasound application during the material initial setting. After storage in water for either 24 h or 30 d, beam-shaped specimens with a cross-sectional area of approximately 1.0 mm(2) were cut perpendicular to GIC/dentin interface and tested to failure. At 24 h, the ultrasonically set Ketac Molar had significantly higher (p < 0.05) µTBS than the cement set conventionally. Chemically set Ketac Molar presented significantly higher µTBS after the longer water storage (p < 0.05). The RMGIC presented the highest µTBS regardless of ultrasonic excitation and storage period. In conclusion, ultrasound application to Ketac Molar improved its adhesion to dentin, particularly within the first 24 h after setting. Clinically, it seems that ultrasonic excitation can contribute to prevent retention loss of restoration at early stages of GIC setting reaction.

Bond strength determination of hydroxyapatite coatings on Ti-6Al-4V substrates using the LAser Shock Adhesion Test (LASAT).

An adhesion test procedure applied to plasma-sprayed hydroxyapatite (HA) coatings to measure the "LASAT threshold" (LAser Shock Adhesion test) is described. The good repeatability and minimal discrepancy of the laser-driven adhesion test data were ascertained for conventional plasma sprayed HA coatings. As a further demonstration, the procedure was applied to HA coatings with diverse characteristics on the ceramic/metal interface. Different preheating and grit blasting conditions and the presence of a thick plasma-sprayed Ti sublayer or a thin TiO(2) layer prepared by oxidation were investigated through LASAT. It was assessed that a rough surface can significantly improve the coating's bond strength. However, it was also demonstrated that a thin TiO(2) layer on a smooth Ti-6Al-4V substrate can have a major influence on adhesion as well. Preheating up to 270°C just prior to the first HA spraying pass had no effect on the adhesion strength. Further development of the procedure was done to achieve an in situ LASAT with in vitro conditions applied on HA coatings. To that end, different crystalline HA contents were soaked in simulated body fluid (SBF). Beyond the demonstration of the capability of this laser-driven adhesion test devoted to HA coatings in dry or liquid environment, the present study provided empirical information on pertinent processing characteristics that could strengthen or weaken the HA/Ti-6Al-4V bond.

Fabrication of submicrometer biomolecular patterns by near-field exposure of plasma-polymerized tetraglyme films.

Plasma-polymerized tetraglyme films (PP4G) have been modified by exposure to ultraviolet (UV) light from a frequency-doubled argon ion laser (244 nm) and characterized using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS data indicated that the ether component of the C 1s spectrum declined after UV exposure, while components due to carbonyl and carboxylate groups increased. The film was physically eroded by UV exposure: after 100 s the rate of erosion reached a steady state of 0.05 nm s(-1). The coefficient of friction, measured by friction force microscopy (FFM), increased substantially following exposure to UV light, reaching a limiting value after 10 min exposure, in agreement with the time taken for the ether and carboxylate components in the C 1s spectrum to reach a limiting value. Samples exposed to UV light through a mask yielded excellent frictional contrast. When immersed in solutions of proteins and protein-functionalized nanoparticles labeled with fluorescent markers, selective adsorption occurred onto the exposed regions of these samples. Excellent fluorescence contrast was obtained when samples were characterized by confocal microscopy, indicating that the exposed areas become adhesive toward proteins, while the masked areas remain resistant to adsorption. Submicrometer structures have been formed by exposing PP4G films to UV light using a scanning near-field optical microscope coupled to a UV laser. Structures as small as 338 nm have been formed and used to immobilize proteins. Again, excellent contrast difference was observed when labeled proteins were adsorbed and characterized by confocal microscopy, suggesting a simple and effective route to the formation of submicrometer scale protein patterns.

Liquid-phase packaging of a glucose oxidase solution with parylene direct encapsulation and an ultraviolet curing adhesive cover for glucose sensors.

We have developed a package for disposable glucose sensor chips using Parylene encapsulation of a glucose oxidase solution in the liquid phase and a cover structure made of an ultraviolet (UV) curable adhesive. Parylene was directly deposited onto a small volume (1 µL) of glucose oxidase solution through chemical vapor deposition. The cover and reaction chamber were constructed on Parylene film using a UV-curable adhesive and photolithography. The package was processed at room temperature to avoid denaturation of the glucose oxidase. The glucose oxidase solution was encapsulated and unsealed. Glucose sensing was demonstrated using standard amperometric detection at glucose concentrations between 0.1 and 100 mM, which covers the glucose concentration range of diabetic patients. Our proposed Parylene encapsulation and UV-adhesive cover form a liquid phase glucose-oxidase package that has the advantages of room temperature processing and direct liquid encapsulation of a small volume solution without use of conventional solidifying chemicals.

Biofouling studies on nanoparticle-based metal oxide coatings on glass coupons exposed to marine environment.

Titania, niobia and silica coatings, derived from their respective nanoparticle dispersions or sols and fabricated on soda lime glass substrates were subjected to field testing in marine environment for antimacrofouling applications for marine optical instruments. Settlement and enumeration of macrofouling organisms like barnacles, hydroides and oysters on these nanoparticle-based metal oxide coatings subjected to different heat treatments up to 400 degrees C were periodically monitored for a period of 15 days. The differences observed in the antifouling behaviour between the coated and uncoated substrates are discussed based on the solar ultraviolet light induced photocatalytic activities as well as hydrophilicities of the coatings in case of titania and niobia coatings and the inherent hydrophilicity in the case of silica coating. The effect of heat treatment on the photocatalytic activity of the coatings is also discussed.

Enhancement of bonding to enamel and dentin prepared by Er,Cr:YSGG laser.

BACKGROUND AND OBJECTIVE: Erbium lasers are potential tools to remove caries and dental hard tissue but bond strengths of composites to those preparations are reported to be lower than conventional methods. The purpose of this study was to evaluate the effect of mechanical excavation and/or chemical alteration on bond strength of composites to laser irradiated enamel and dentin. MATERIALS AND METHODS: Seventy-two premolars were ground to obtain flat enamel (E, n = 36) or dentin (D, n = 36) surfaces in both buccal and lingual cusps, divided into: LaserExcavation (LEx), LaserNo-excavation (LNex), and Bur (B) groups. The laser groups were irradiated for 10 seconds by Er,Cr:YSGG laser [4.5 W, 60% air, 80% water (enamel) 3 W, 60% air, 70% water (dentin)]. Irradiated surfaces in the excavation groups (Ex) were then mechanically smoothed with a dental excavator, prepared surfaces were then etched (37% H(3)PO(4)) for 20 or 40 seconds (enamel) and 15 or 30 seconds (dentin), washed (20 seconds), adhesive was applied(Single Bond Plus), and light cured (20 seconds). A composite cylinder (Filtek Supreme Plus) formed, placed and light cured (40 seconds). The specimens were stored (37 degrees C,48 hours), shear bond tested (1 mm/minute), and statistically analyzed (P < 0.05). RESULTS: Mixed-model ANOVA showed significant differences between enamel (P = 0.0091) and between dentin groups (P = 0.0035). Tukey/Kramer showed mean shear bond strength (SBS+/-SE) of EB40 (27.01+/-2.38 MPa) was significantly higher than ELNoExc20 (14.39+/-2.5 MPa) and ELExc40 (14.90+/-2.28 MPa). Also DB30 (17.57+/- 1.67 MPa) and DLExc30 (18.6+/-1.74 MPa) were significantly higher than DLNoExc15 (9.56+/-1.86 MPa). CONCLUSION: Increasing the etching time up to 40 seconds or excavation of the laser prepared surface (but not the combination) may increase the bond strength to the level of conventional methods in enamel but excavation has a greater influence in dentin. Also the combination of both methods [excavation+longer etching time (30 seconds)] exhibit significantly better results in dentin.Mode of failure study showed mechanical excavation in both enamel and dentin can significantly reduce the cohesive failure in tooth structure.

Effect of a simulated high-heat environment on bond strengths of dental adhesive systems.

OBJECTIVE: The goal was to evaluate the effect of high-heat storage of three dental adhesive bonding agents on the bond strength of composite resin to dentin. METHODS: Three different adhesive bonding agents were stored for 1 month at the manufacturers' recommended temperatures and simultaneously at high temperatures (43 degrees C). The adhesives and a composite resin restorative material were bonded to the dentinal surface of five sectioned, extracted, human teeth for each of the six groups. The teeth were further sectioned into four beams per tooth (N=20) and separated with a universal testing machine. Data were analyzed with analysis of variance/Tukey's test and Student's t test. RESULTS: One of the three bonding agents had significantly lower bond strength when stored in a high-heat environment (p = 0.0003). CONCLUSIONS: High-heat storage conditions, as may occur in areas of deployment in Southwest Asia, may cause a reduction in the performance of some dental adhesives, potentially leading to premature failure of the restoration.

Adhesion after erbium, chromium:yttrium-scandium-gallium-garnet laser application at three different irradiation conditions.

The aim of this study was to investigate whether distinct cooling of low fluence erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation would influence adhesion. Main factors tested were: substrates (two), irradiation conditions (three), and adhesives (three). A 750 microm diameter tip was used, for 50 s, 1 mm from the surface, with a 0.25 W power output, 20 Hz, energy density of 2.8 J/cm(2) with energy per pulse of 12.5 mJ. When applied, water delivery rate was 11 ml/min. The analysis of variance (ANOVA) showed that laser conditioning significantly decreased the bond strength of all adhesive systems applied on enamel. On dentin, laser conditioning significantly reduced bond strength of etch-and-rinse and one-step self-etch systems; however, laser irradiation under water cooling did not alter bonding of two-step self-etching. It may be concluded that the irradiation with Er,Cr:YSGG laser at 2.8 J/cm(2) with water coolant was responsible for a better adhesion to dentin, while enamel irradiation reduced bond strength, irrespective of cooling conditions.

Nano-hardness of adhesive interface between Er:YAG laser-irradiated dentin and 4-META/MMA-TBB resin.

OBJECTIVE: The purpose of this study was to evaluate the hardness of the adhesive interface between resin and Er:YAG laser-irradiated bovine dentin by nano-indentation. BACKGROUND DATA: It has been reported that laser output energy and pulse repetition rate affect the tensile bond strength in Er:YAG laser-irradiated dentin. MATERIALS AND METHODS: Three laser settings were evaluated at the same total energy level (approximately 1.0 W): 100 mJ/pulse-10 pps (100-10), 50 mJ/pulse-20 pps (50-20), and 33 mJ/pulse-30 pps (33-30). Laser-irradiated dentin in each group was conditioned with 10% citric acid solution containing 3% ferric chloride for 15 sec, rinsed with distilled water for 30 sec, and bonded to PMMA rods with 4-META/MMA-TBB resin. The bonded specimens were sectioned vertically, embedded in epoxy resin, and their nano-hardness measured. A non-irradiated control group was also investigated. RESULTS: The adhesive resin interface in the controls showed the lowest level of hardness, which gradually increased from the top of the hybrid layer (0 microm) through the bottom of the hybrid layer (5 microm) and into the underlying dentin ( approximately 10 microm). Significant differences in hardness were observed between the 5 microm point in the controls, the 10 microm and 15 microm points in the 100-10 group, and the 10 microm point in the 50-20 and 33-30 groups. CONCLUSION: The results suggest that laser settings affect hybrid layer thickness, even when the total energy level is constant.

Micro-shear bond strength of Er:YAG-laser-treated dentin.

This study tested if dentin adhesion is affected by Er:YAG laser. Ninety dentin disks were divided in groups (n = 10): G1, control; G2, Er:YAG laser 150 mJ, 90 degrees contact, 38.8 J/cm(2); G3, Er:YAG laser 70 mJ, 90 degrees contact, 18.1 J/cm(2); G4, Er:YAG laser 150 mJ, 90 degrees non-contact, 1.44 J/cm(2); G5, Er:YAG laser 70 mJ, 90 degrees non-contact, 0.67 J/cm(2); G6, Er:YAG laser 150 mJ, 45 degrees contact, 37.5 J/cm(2); G7, Er:YAG laser 70 mJ, 45 degrees contact, 17.5 J/cm(2); G8, Er:YAG laser 150 mJ, 45 degrees non-contact, 1.55 J/cm(2); and G9, Er:YAG laser 70 mJ, 45 degrees non-contact, 0.72 J/cm(2). Bonding procedures were carried out and the micro-shear-bond strength (MSBS) test was performed. The adhesive surfaces were analyzed under SEM. Two-way ANOVA and multiple comparison tests revealed that MSBS was significantly influenced by the laser irradiation (p < 0.05). Mean values (MPa) of the MSBS test were: G1 (44.97 +/- 6.36), G2 (23.83 +/- 2.46), G3 (30.26 +/- 2.57), G4 (35.29 +/- 3.74), G5 (41.90 +/- 4.95), G6 (27.48 +/- 2.11), G7 (34.61 +/- 2.91), G8 (37.16 +/- 1.96), and G9 (41.74 +/- 1.60). It was concluded that the Er:YAG laser can constitute an alternative tool for dentin treatment before bonding procedures.