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OBJECTIVES: Surface conditioning of enamel and dentin is a key step during adhesive restorative procedures and strategies. The aim of this study was to investigate the effectiveness of five α-hydroxy-acids (AHAs) as enamel and dentin surface etchants. METHODS: Enamel and dentin specimens were prepared from human molars to determine the depth of demineralization by optical profilometry (Δz), the resin bond strength to enamel and dentin (μTBS), the micro-permeability of dentin-resin interfaces, and the gelatinolytic activity of dentin matrix induced by AHAs [glycolic (GA), lactic (LA), citric (CA), malic (MI) and tartaric (TA)] and controls [phosphoric (PA) and maleic (MA)]. All acids were prepared at 35% concentration. Adhesion studies employed Adper Single Bond Plus bonding system. Data were individually processed and analyzed by ANOVA, post-hoc tests and Pearson correlations (α=0.05). RESULTS: AHA exhibited statistically lower depth of demineralization of enamel and dentin (average 4 fold) than controls (p

The purpose of this study was to explore the influence of Er:YAG laser irradiation with different pulse durations on the organic matrix, micromorphology of the hybrid layer (HL), and bond strength over time. Sixty caries-free human molars were cut to obtain flat dentin surfaces which were randomly divided into 4 groups: control (not irradiated–G1) and laser groups (80 mJ/2 Hz) with pulse duration ranging between 50 (G2), 300 (G3), and 600 μs (G4). A self-etch adhesive system (Universal 3M ESPE) was applied on pre-treated dentin surfaces and cylinders of resin composite were built up and stressed in a universal testing machine (μSBS) at 24 h and after12 months (n = 12). In addition, 3 other dentin-bonded specimens were prepared as previously described for each group with the adhesive doped with 0.1 wt% Rhodamine B to analyze hybrid layer morphology under Confocal Laser Microscope Scanning (CLMS). Organic matrix and collagen fibrils were analyzed by second harmonic generation (SGH). Two-way ANOVA and Tukey’s test detected significantly higher μSBS values for the control group, whereas the lower values were observed in all laser groups at 24 h (p

Proanthocyanidin-rich plant-derived agents have been shown to increase dentin biomechanical properties and resistance of dentinal collagen to degradation. This study investigated the effects of proanthocyanidin-rich extract (grape seed extract, GSE; Vitis vinifera) on the mechanical properties of demineralized dentin matrix, and the bond strength and stability of the adhesion of fiber posts to the root dentin. Demineralized dentin beams (n = 15) were incubated with 6.5% or 10% GSE for 30, 60, or 120 s. The modulus of elasticity (E) and the fold increase in E were determined by comparing specimens at baseline and after treatment. The data were analyzed by two-way ANOVA and Tukey post hoc tests (α = 0.05). For the bond strength test, single-rooted human teeth were randomly divided into seven groups: control group, no treatment; and experimental groups as described for the modulus of elasticity. Fiber posts were cemented with RelyX U200. Each group was randomly divided into two subgroups: 24 hours of water storage and 12 months of water storage. All roots were sectioned transversely in the coronal, middle, and apical regions, producing 1-mm thick slices, and the push-out test was performed. The failure modes were observed, and the bond strength means were analyzed by ANOVA (α = 0.05). For E test, no significant difference was observed among the incubation times (P > 0.05); however, high concentration of GSE (10%) resulted in a statistically higher fold increase in E compared to 6.5% (P 0.05), irrespective of the GSE concentration, time of treatment, and root regions (P > 0.05); however, the use of GSE contributed to a significant reduction in adhesive failure mode. The results indicate that 10% GSE exhibits a high cross-linking potential for dentin extracellular matrix. Moreover, the bond strength of fiber posts luted to root dentin with RelyX U200 remained stable after 12 months of water storage, with or without pre-treatment with GSE.

OBJECTIVES: Proanthocyanidins (PACs) are biocompounds mimicking native collagen cross-links. The effective and practical delivery of any biocompound is pivotal for clinical usage. The aim was to investigate the dentin biomodification and effective formation of dentin-resin biointerfaces of two highly bioactive PAC-rich extracts, Vitis vinifera (Vv) and Camellia sinensis (Cs), delivered using neutral (NP) or acidic (AP) rinse-out primer approaches. METHODS: The depth of dentin demineralization (optical profilometry), dentin biomodification (apparent modulus of elasticity, collagen auto-fluorescence) and properties of dentin-resin interfaces (microtensile bond strength – μTBS, and micro-permeability) were investigated. NP consisted of either 15% Vv or Cs applied for 60s after surface etching; while AP contained 15% Vv or Cs in either 35% glycolic acid (GA) or tartaric acid (TA) applied for 30s or 60s. Data were analyzed using ANOVA and post-hoc tests (α=0.05). RESULTS: The depth of demineralization was statistically higher when applied for 60s, regardless of rinse-out primer approach (p

To evaluate the treatment of eroded dentin (Sensodyne Repair & Protect™, Er:YAG laser and combinations). The occlusal surfaces of 25 third molars were sectioned 1.5 mm in thickness. After an erosion cycle (5 min in demineralizing solution + 3 h in remineralizing solution; six cycles a day for 8 days), the samples were divided into five groups (n = 5): (E) erosion − control; (ES) erosion + Sensodyne Repair & Protect (NovaMin); (EL) erosion + Er:YAG laser (40 mJ, 10 Hz, 0.4 W, 50 μs, 3.1 J/cm2, 63 W/cm2); (ELS) erosion + Er:YAG laser + Sensodyne; and (ESL) erosion + Sensodyne + Er:YAG laser. Following storage in ultrapure water (37 °C/14 days), the Ca/P ratio was evaluated by EDXRF and the morphology surfaces examined in SEM. The percentage of exposed dentin tubules was calculated. One-way analysis of variance and Tukey’s test at 5% were used to treat the data. The Ca/P ratio was higher in E and ES groups. More exposed dentin tubules were found in E group and less exposed tubules were found in the ES group (p

To evaluate the ultra-morphology of the dentin after irradiation with Er:YAG laser using shorter pulse durations in different protocols by transmission electron microscopy (TEM). The Er:YAG laser is an effective alternative method for hard dental tissue treatment with great acceptability among patients. However, undesirable effects may occur in dental substrate if the correct parameters are not chosen during irradiation protocols, jeopardizing bonding that could result in premature failures. But, before doing bonding tests, it is fundamental the knowledge of the laser action into dentin. It is well known that shorter pulses have less thermal damage due to less heat loss during irradiation; hence, it is primordial to evaluate the performance of shorter pulses in irradiation protocols. Eighteen dentin disks with 2 mm thick were assigned into six experimental groups according to the irradiation protocol: cavity preparation (200 mJ and 20 Hz) and pretreatment (80 mJ and 2 Hz) varying the pulse duration (50, 300, or 600 μs), in focused distance and under refrigeration. Qualitative and semi-quantitative analyses were performed. The pretreatment with 50 μs was the protocol that maintained intact both architecture of collagens fibrils and an organized extracellular matrix. Nevertheless, the other groups showed a melted and carbonized dentin surface followed by fused zone of collagen fibrils with loss of interfibrillar spaces. It was concluded that the thickness of the altered layer is directly proportional to the enhance of pulse duration for cavity preparation protocols tested. Moreover, pretreatment with 50 μs is an adequate protocol for dentin, which did not alter its ultra-morphology.

This study has compared morphological characteristics of dentin and enamel surfaces after cavity preparation by conventional methods and Er:YAG laser irradiation in different settings by using an Er:YAG laser scanner. Thirty-five human teeth were randomly divided into seven groups that received cavity preparations as follows: G1 and G2 with high-speed drill with diamond and carbide burs, respectively, and G3 to G7 with Er:YAG laser scanner (λ = 2940 nm) operating at pulse energies (energy densities) of 420 mJ (840 J/cm2), 490 mJ (980 J/cm2), 560 mJ (1120 J/cm2), 630 mJ (1260 J/cm2) and 700 mJ (1400 J/cm2), respectively. The lased groups were treated with Er:YAG laser scanner in non-contact mode, keeping both frequency (20 Hz) and pulse duration (300 μs) fixed. Samples were sectioned and scanning electron micrographs of the lateral wall of the cavities were taken at different magnifications. The results showed that both groups of conventional cavity preparations exhibited enamel and dentin surfaces covered by smear layer, with no dentin-enamel boundary being identifiable. All lased groups showed clear enamel-dentin boundaries and clean surfaces of enamel and dentin with different micro-morphologies. The morphology of lased dental surfaces presented homogeneous alterations. The Er:YAG scanner-assisted cavity preparation produced topographies in the entire dental surfaces and whose morphological characteristics were more favourable to further adhesion of resin restorations than the conventional ones.

Objective: The aim of this study was to evaluate the adhesion of a self-etching system to caries-affected dentin (CAD) and sound dentin (SD) after different caries removal techniques by using microtensile bond strength test (?TBS). Materials and Methods: Twenty-four extracted human molars with coronal carious lesions were used. The samples were randomly divided into 5 groups, according to caries removal method: G1 - negative control (no removal); G2 abrasive disc; G3 – slow speed steel bur; G4 - Nd:YAG laser (energy density 21.2J/cm2); G5 - Er:YAG laser (energy density 80.24J/cm2). SD and CAD/ infected dentin substrates were tested. Self-etch system (Clearfil SE Bond) was applied and resin crowns were built up. Results: One-way ANOVA showed statistically significant difference between experimental groups (p

This study investigated the contribution of small leucine rich proteoglycans (SLRPs) to the fracture toughness of the dentin extracellular matrix (ECM) by enzymatically-assisted selective removal of glycosaminoglycan chains (GAGs) and proteoglycans (PGs) core protein. We adapted the Mode III trouser tear test to evaluate the energy required to tear the dentin ECM. Trouser-shaped dentin specimens from crown and root were demineralized. Depletion of GAGs and PGs followed enzymatic digestion using chondroitinase ABC (c-ABC) and matrix metalloproteinase 3 (MMP-3), respectively. The legs from specimen were stretched under tensile force and the load at tear propagation was determined to calculate the tear energy (T, kJ/m2). SLRPs decorin and biglycan were visualized by immunohistochemistry and ECM tear pattern was analyzed in SEM. Results showed T of crown ECM was not affected by PGs/GAGs depletion (p = 0.799), whereas the removal of PGs significantly reduced T in root dentin ECM (p = 0.001). Root dentin ECM exhibited higher T than crown (p

Collagen glycation takes place under physiological conditions during chronological aging, leading to the formation of advanced glycation end-products (AGEs). AGEs accumulation induces non-enzymatic collagen cross-links increasing tissue stiffness and impairing function. Here, we focused on determining the cumulative effect of induced glycation on the mechanical behavior of highly collagen cross-linked dentin matrices and assess the topical inhibition potential of aminoguanidine. Bulk mechanical characterization suggests that early glycation cross-links significantly increase the tensile strength and stiffness of the dentin matrix and promote a brittle failure response. Histologically, glycation yielded a more mature type I collagen in a densely packed collagen matrix. The time-dependent effect of glycation indicates cumulative damage of dentin matrices that is partially inhibited by aminoguanidine. The regional dentin sites were differently affected by induced-glycation, revealing the crown dentin to be mechanically more affected by the glycation protocol. These findings in human dentin set the foundation for the proposed in vitro ribose-induced glycation model, which produces an early matrix stiffening mechanism by reducing tissue viscoelasticity and can be partially inhibited by topical aminoguanidine.

This study evaluated the effect of different pulse widths in the morphological characteristics of human dentin irradiated with Er:YAG in cavity preparation protocols and dentin pretreatment. Dentin discs with 2 mm thickness were obtained from 18 human molars. The experimental groups were composed from two variables: (1) clinical protocol—cavity preparation (E = 200 mJ/20 Hz)—and pretreatment (E = 80 mJ/2 Hz); and (2) pulse duration—50, 300, and 600 μs. This formed six experimental groups (n = 3): G1 (E = 200 mJ/20 Hz/50 μs); G2 (E = 200 mJ/20 Hz/300 μs); G3 (E = 200 mJ/20 Hz/600 μs); G4 (E = 80 mJ/2 Hz/50 μs); G5 (E = 80 mJ/2 Hz/300 μs); G6 (E = 80 mJ/2 Hz/600 μs). The samples were irradiated with the Er:YAG laser by noncontact mode at a focal distance of 7 mm from the target point under continuous water spray (60% water and 40% air). After the irradiation, they were processed for scanning electron microscopy (SEM). Morphological analysis showed an irregular dentin surface, absence of smear layer with opening of the exposure of dentinal tubules and protruding peritubular dentin—without indications of changes for all protocols used. Regardless of the analyzed experimental group, the dentin surface showed a microretentive morphology characteristic of ablation. The G1 and G4 showed a rougher surface when compared to other groups. Finally, we concluded that the pulse width can influence the morphological characteristics of the irradiated dentin tested in different clinical indications. The larger surface irregularity caused by regulation with less pulse width (50 µs) seems more appropriate to get a microretentive pattern necessary for successful adhesives restoration procedures. Microsc. Res. Tech. 78:472–478, 2015. © 2015 Wiley Periodicals, Inc.

Post-traumatic nerve repair represents a major challenge to health sciences. Although there have been great advances in the last few years, it is still necessary to find methods that can effectively enhance nerve regeneration. Laser therapy has been widely investigated as a potential method for nerve repair. Therefore, in this article, a review of the existing literature was undertaken with regard to the effects of low-power laser irradiation on the regeneration of traumatically/surgically injured nerves. The articles were selected using either electronic search engines or manual tracing of the references cited in key papers. In electronic searches, we used the key words as "paresthesia", "laser therapy", "low-power laser and nerve repair", and "laser therapy and nerve repair", considering case reports and clinical studies. According to the findings of the literature, laser therapy accelerates and improves the regeneration of the affected nerve tissues, but there are many conflicting results about laser therapy. This can be attributed to several variables such as wavelength, radiation dose, and type of radiation. All the early in vivo studies assessed in this research were effective in restoring sensitivity. Although these results indicate a potential benefit of the use of lasers on nerve repair, further double-blind controlled clinical trials should be conducted in order to standardize protocols for clinical application.

The aim of the present study was to conduct a review of the literature about adhesion on erbium laser prepared cavities, related to the specific conditions of the irradiated dentin substrate and the effects on bond strength values.Advances in adhesive restorative techniques significantly influenced modern restorative dentistry. The concept of "minimally invasive dentistry" aims to perform more conservative treatment of cavities in which the removal of sound dentin is no longer necessary. This approach, which relies on the concept of adhesion of restorative materials to the mineralized dental tissues, is considered to be a contemporary outcome in dentistry. Similarly, laser technology in restorative dentistry opened new possibilities and strategies as alternatives to conventional treatment. Considering the clinical aspects of the use of erbium lasers for caries removal, cavity preparations, and substrate conditioning, treatment with lasers can be considered to be an efficient technique with wide acceptance by patients.Computerized and manual searches were conducted for studies through 2015 that addressed the topic.According to the literature, there is no defined standard protocol concerning the information that articles must provide, making a definitive protocol very difficult to establish. Data varied from the type of adhesive and resin composite used, substrate, and parameters (power, energy density, pulse duration, irradiation time, distance, cooling system) to the bond strength test methodology used.Further studies are necessary in order to define a standard protocol with positive results and higher bond strength values when using erbium lasers. Detailed information concerning laser parameters should be implemented. Also, longitudinal clinical studies should be developed in the search for new parameters that behave favorably in the irradiated substrate.