Comparison of biofilm models for producing artificial active white spot lesions.

OBJECTIVE: This study compared three protocols for developing artificial white spot lesions (WSL) using biofilm models. METHODOLOGY: In total, 45 human enamel specimens were sterilized and allocated into three groups based on the biofilm model: Streptococcus sobrinus and Lactobacillus casei (Ss+Lc), Streptococcus sobrinus (Ss), or Streptococcus mutans (Sm). Specimens were incubated in filter-sterilized human saliva to form the acquired pellicle and then subjected to the biofilm challenge consisting of three days of incubation with bacteria (for demineralization) and one day of remineralization, which was performed once for Ss+Lc (four days total), four times for Ss (16 days total), and three times for Sm (12 days total). After WSL creation, the lesion fluorescence, depth, and chemical composition were assessed using Quantitative Light-induced Fluorescence (QLF), Polarized Light Microscopy (PLM), and Raman Spectroscopy, respectively. Statistical analysis consisted of two-way ANOVA followed by Tukey's post hoc test (α=0.05). WSL created using the Ss+Lc protocol presented statistically significant higher fluorescence loss (ΔF) and integrated fluorescence (ΔQ) in comparison to the other two protocols (p<0.001). RESULTS: In addition, Ss+Lc resulted in significantly deeper WSL (137.5 µm), followed by Ss (84.1 µm) and Sm (54.9 µm) (p<0.001). While high mineral content was observed in sound enamel surrounding the WSL, lesions created with the Ss+Lc protocol showed the highest demineralization level and changes in the mineral content among the three protocols. CONCLUSION: The biofilm model using S. sobrinus and L. casei for four days was the most appropriate and simplified protocol for developing artificial active WSL with lower fluorescence, higher demineralization, and greater depth.

Comparison between a bulk-fill resin-based composite and three luting materials on the cementation of fiberglass-reinforced posts.

Objectives: This study verified the possibility of cementing fiberglass-reinforced posts using a flowable bulk-fill composite (BF), comparing its push-out bond strength and microhardness with these properties of 3 luting materials. Materials and Methods: Sixty endodontically treated bovine roots were used. Posts were cemented using conventional dual-cured cement (CC); self-adhesive cement (SA); dual-cured composite (RC); and BF. Push-out bond strength (n = 10) and microhardness (n = 5) tests were performed after 1 week and 4 months of storage. Two-way repeated measures analysis of variance (ANOVA), 1-way ANOVA, t-test, and Tukey post-hoc tests were applied for the push-out bond strength and microhardness results; and Pearson correlation test was applied to verify the correlation between push-out bond strength and microhardness results (α = 0.05). Results: BF presented higher push-out bond strength than CC and SA in the cervical third before aging (p < 0.01). No differences were found between push-out bond strength before and after aging for all the luting materials (p = 0.84). Regarding hardness, only SA presented higher values measured before than after aging (p < 0.01). RC and BF did not present 80% of the maximum hardness at the apical regions. A strong positive correlation was found between the luting materials' push-out bond strength and microhardness (p < 0.01, R2 = 0.7912). Conclusions: The BF presented comparable or higher push-out bond strength and microhardness than the luting materials, which indicates that it could be used for cementing resin posts in situations where adequate light curing is possible.

Comparison of collagen features of distinct types of caries-affected dentin.

OBJECTIVES: To compare the biodegradability, mechanical behavior, and physicochemical features of the collagen-rich extracellular matrix (ECM) of artificial caries-affected dentin (ACAD), natural caries-affected dentin (NCAD) and sound dentin (SD). METHODS: Dentin specimens from human molars were prepared and assigned into groups according to the type of dentin: ACAD, NCAD, or SD. ACAD was produced by incubation of demineralized SD with Streptococcus mutans in a chemically defined medium (CDM) with 1% sucrose for 7 days at 37 °C under anaerobic conditions. Specimens were assessed to determine collagen birefringence, biodegradability, mechanical behavior, and chemical composition. Data were individually processed and analyzed by ANOVA and post-hoc tests (α = 0.05). RESULTS: CDM-based biofilm challenge reduced loss, storage, and complex moduli in ACAD (p < 0.001), while the damping capacity remained unaffected (p = 0.066). Higher red and lower green birefringence were found in ACAD and NCAD when compared with SD (p < 0.001). Differently to ACAD, SD and NCAD presented higher biodegradability to exogenous proteases (p = 0.02). Chemical analysis of the integrated areas of characteristic bands that assess mineral quality (carbonate/phosphate and crystallinity index), mineral to matrix (phosphate/amide I) and post-translational modifications (amide III/CH2, pentosidine/CH2, and pentosidine/amide III) (p<0.05) showed that NCAD was significantly different from SD while ACAD exhibited intermediate values. CONCLUSIONS: CDM-based biofilm challenge produced a dentin ECM with decreased mechanical properties and increased collagen maturity. The compositional and structural conformation of the ACAD suggested that CDM-based biofilm challenge showed potential to produce artificial lesions by revealing a transitional condition towards mimicking critical features of NCAD. CLINICAL SIGNIFICANCE: This study highlights the importance of developing a tissue that mimics the features of natural caries-affected dentin ECM for in vitro studies. Our findings suggested the potential of a modified biofilm challenge protocol to produce and simulate a relevant substrate, such as caries-affected dentin.

Characterization of sound enamel and natural white spot lesions / Caracterização de esmalte hígido e lesões de mancha branca naturais

Objective: To compare optical, morphological, chemical, and physical aspects of the sound enamel and white spot lesions (WSL) classified as ICDAS 2. Material and Methods: Seventeen human molars with one surface presenting WSL and a sound surface (2 x 2 mm window) were characterized by Quantitative light-induced fluorescence (QLF ®), Optical coherence tomography (OCT), microhardness, and Raman spectroscopy. The ANOVA and Tukey's test were used at 5% significance level. Results: The QLF comparison between distinct substrates yielded decreased ∆Q (integrated fluorescence loss) of -15,37%mm2 and -11,68% ∆F (fluorescence loss) for WSL. The OCT detected mean lesion depth of 174,43 µm. ANOVA could not detect differences in the optical attenuation coefficient between the substrates (p>0.05). Lower microhardness measures were observed in WSL than on sound enamel (p<0.05). The Raman spectra showed four vibrational phosphate bands (v1, v2, v3, v4), where the highest peak was at 960.3 cm-1(v1) for both substrates. However, a 40% decrease in phosphate (v1) was detected in WSL. The peak at 1071 cm-1 was higher for sound enamel, indicating the presence of a phosphate band instead of the B-type carbonate. The spectra showed higher intensity of the organic composition at 1295 cm-1 and 1450 cm -1 for WSL. Conclusion: Non-invasive QLF, OCT and Raman spectroscopy were able to distinguish differences in fluorescence, optical properties, and organic/inorganic components, respectively, between sound enamel and WSL, validated by the destructive microhardness analysis. (AU)

Objetivo: Comparar os aspectos ópticos, morfológicos, químicos e físicos do esmalte sadio e das lesões de mancha branca naturais, classificada como ICDAS 2. Material e métodos: Dezessete molares humanos com uma face apresentando uma lesão de mancha branca natural e outra face o esmalte hígido (2 x 2 mm) foram caracterizados utilizando a Fluorescência quantitativa induzida pela luz (QLF ®), Tomografia de coerência óptica (OCT), Microdureza e Espectroscopia Raman. A ANOVA e o teste de Tukey foram utilizados ao nível de significância de 5%. Resultados: A comparação entre os substratos distintos, utilizando o QLF ® demonstrou uma diminuição no ∆Q (perda de fluorescência integrada) de -15,37%mm2 e -11,68% de ∆F (Perda de fluorescência) para a lesão de mancha branca. O OCT detectou uma profundidade média de lesão de 174,43µm. A ANOVA não detectou diferenças no coeficiente de atenuação óptica entre os substratos (>0,05). Microdureza significantemente menor foi detectada nas lesões de mancha branca do que no esmalte sadio (p<0,05). Os espectros Raman mostraram quatro bandas vibracionais do fosfato (v1,v2,v3,v4), onde o maior pico foi em 960,3cm-1para ambos os substratos. No entanto, uma diminuição de 40% no fosfato (v1) foi detectada na lesão. O pico em 1071cm-1foi maior para o esmalte hígido, demonstrando tratar-se da banda do fosfato, ao invés do carbonato tipo B. Os espectros apresentaram maior intensidade da composição orgânica em 1295cm-1e 1450 cm-1para a lesão de mancha branca. Conclusão:Os métodos não invasivos QLF, OCT e espectroscopia Raman foram capazes dediferenciar a fluorescência, propriedades ópticas e conteúdo orgânico/inorgânico do esmalte sadio comparado com esmalte com lesões de mancha branca, sendo validado pela análise de microdureza. (AU)

Effect of silica coating and laser treatment on the flexural strength, surface characteristics, and bond strength of a dental zirconia.

This study investigated the effect of irradiation with an erbium-doped yttrium aluminium garnet (Er:YAG) laser and coating with silica on the surface characteristics, bond strength, and flexural strength of dental zirconia. Three hundred and forty-three standard zirconia specimens were created, and 49 were assigned to each of seven surface treatment groups: (i) no treatment; Er:YAG laser (80 mJ/2 Hz) with pulse widths of 50 µs (ii), 100 µs (iii), 300 µs (iv), or 600 µs (v); or tribochemical silica coating at the partially sintered stage (vi) or after sintering was complete (vii). All specimens were sintered after the surface treatments, except for the group in which specimens were sintered before treatment. The study outcomes were roughness, surface loss, microshear bond strength (µSBS), and biaxial flexural strength (BFS). Mean roughness and surface loss values were significantly higher in specimens from irradiated groups than in those from silica-coated groups. Regarding µSBS, after aging, specimens from all experimental groups presented very low and similar µSBS values, irrespective of the surface treatment. Silica coating after sintering yielded the highest BFS (1149.5 ± 167.6 MPa), while coating partially sintered specimens with silica resulted a BFS (826.9 ± 60.9 MPa) similar to that of the untreated control group (794.9 ± 101.7 MPa). Laser treatments, irrespective of pulse width used, significantly decreased the BFS. In the group treated with laser at 300 µs pulse width, specimens exhibited the lowest BFS value (514.1 ± 71.5 MPa). Adhesion to zirconia was not stable after aging, regardless of the surface treatment implemented.

Effect of erosive and abrasive challenges on the glaze layer applied to ceramic materials.

PURPOSE: This study aims to evaluate the effect of erosive, abrasive, and erosive/abrasive challenges on the glaze layer of ceramic materials. METHODS: Ninety-five samples of monolithic zirconia (MZ) (LuxaCam Zircon HT-Plus) and lithium disilicate (LD) (IPS e.max CAD) were divided according to the response variables: Surface roughness and surface loss (n = 10), evaluated with optical profilometry; surface topography, with scanning electron microscopy SEM (n = 3); and biofilm deposition, with microbiological assay (n = 5). The evaluations were performed in three different time evaluations: (a) Sintered, (b) Glaze, and (c) Challenge (Erosion, Abrasion, and Erosion/Abrasion). Erosion consisted in immersing specimens in HCl solution, abrasion was performed with brushing machine, and erosion/abrasion consisted of a combination of the two previous protocols. Data were analyzed with parametric tests (P < 0.05). RESULTS: MZ glaze layer presented significantly higher surface roughness (P = 0.00), surface loss (P = 0.03), and biofilm deposition (P = 0.00) than LD. Abrasion and erosion/abrasion showed similar outcomes, generating significantly higher surface roughness (P = 0.00), surface loss (P = 0.00), and biofilm deposition (P = 0.01) than erosion. CONCLUSIONS: Glaze layer properties were altered by the challenges, with abrasion and erosion/abrasion generating higher surface roughness, surface loss, and biofilm deposition than erosion. A significant correlation was found between the surface roughness and biofilm deposition. CLINICAL SIGNIFICANCE: The glaze layer is susceptible to challenges, especially to abrasion and erosion/abrasion, which generated greater surface roughness and surface loss than erosion. The greater surface roughness lead to a greater biofilm deposition on the glaze layer.

Gelatinolytic Activity and Adhesion Studies of Artificial Caries-affected Dentin do not Simulate Natural Caries.

PURPOSE: To investigate whether interfacial enzymatic activity and adhesion receptiveness of artificial caries-affected dentin (ACAD) simulate those of natural caries-affected dentin (NCAD). MATERIALS AND METHODS: Thirty dentin specimens were prepared from human molars to determine interfacial gelatinolytic activity using in situ zymography and adhesion experiments (micropermeability and bond strength [µTBS]). Groups were formed according to the type of dentin: artificial caries-affected dentin (ACAD), natural caries-affected dentin (NCAD), or sound dentin. ACAD was produced by incubating dentin with Streptococcus mutans in a chemically defined medium (CDM) with 1% sucrose for 7 days at 37°C under anaerobic conditions. CDM was replaced daily, and the sterility as well as the pH of the culture was monitored. Adhesion experiments employed Single Bond Universal (3M Oral Care) in self-etch mode. Data were individually processed and analyzed using ANOVA and post-hoc tests (α = 0.05). RESULTS: The enzymatic activity of ACAD was similar to that of sound dentin, but was lower than that of NCAD, which elicited the highest activity (p < 0.05). Interfacial micropermeability intensity at the hybrid layer or in underlying dentin (5 µm below the interface) was similar in all types of dentin (p > 0.05). On the other hand, substrate permeability was higher for NCAD than for ACAD. The highest sealing ability was detected in sound dentin. Bond strengths to ACAD were higher than to NCAD. However, the highest µTBS was observed in sound dentin (p < 0.05). CONCLUSION: Artificial caries-affected dentin simulated neither the gelatinolytic activity nor bonding receptiveness of natural caries-affected dentin.

Effect of thermal and acid challenges on the surface properties of pink restorative materials.

PURPOSE: To compare the effect of thermal cycling and erosive challenge on color change, surface roughness, surface loss and biofilm deposition of three resin-based composites. METHODS: Three resin-based composites that reproduce the color of gingival tissues [two nanohybrid composites (A and B) and a giomer (C) ] were tested before and after distinct challenges [ thermal cycling (TC) and erosive challenge (EC) ] in regard to its color stability, surface roughness, surface loss and biofilm deposition. Surface roughness and surface loss specimens (n=10) were measured with an optical profilometer and, color stability (n=10) was measured with a spectrophotometer. Biofilm deposition (n=5) was measured after 3 and 24 hours by safranin staining. RESULTS: Two-way ANOVA test was performed to analyze color change, roughness and surface loss. A significant color change was detected for resin-based composites (P< 0.05) and its interaction with tested challenges (P< 0.05). The highest color variation was observed on the giomer after erosive challenge. Surface loss was not different between tested groups (P= 0.708). The roughness was significantly higher in specimens submitted to thermal cycling (P> 0.05). For biofilm quantification, after 3 and 24 hours, ANOVA (3-way) detected significance for the interaction of challenges and resin-based composites (P< 0.05 and P< 0.05, respectively). All resin-based composites presented color changes after challenges; higher roughness was observed after thermal cycling for all resin-based composites tested, without significant surface loss; and higher biofilm deposition was observed on the giomer samples when submitted to erosive challenge after 3 and 24 hours. CLINICAL SIGNIFICANCE: Pink esthetic is as important as dental esthetics and some restorative materials can mimic gingival tissue. However, the tested giomer must be indicated with caution, since it presented significant changes after thermal and acid challenges.

Investigation of five α-hydroxy acids for enamel and dentin etching: Demineralization depth, resin adhesion and dentin enzymatic activity.

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 < 0.001). In enamel, MA and PA etching resulted in higher µTBS than AHA groups (p < 0.001). In dentin, GA, TA, CI and LA etching resulted in statistically similar µTBS than PA (p < 0.05). The hybrid-layer (HL) thickness and interfacial micro-permeability intensity were statistically lower for AHA groups (p < 0.05). A significant positive correlation was observed between the intensity of micro-permeability and the thickness of HL (p < 0.05). AHA etchants elicited lower dentin enzymatic activity than controls (p < 0.05). SIGNIFICANCE: AHAs effectively etched enamel and dentin surfaces. In particular, GA and TA resulted in suitable µTBS and sealing ability as well as induced less gelatinolytic activity in dentin than PA and MA.

Influence of Er:YAG laser pulse duration on the long-term stability of organic matrix and resin-dentin interface.

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 < 0.05). Storage in artificial saliva did not reduce µSBS in all groups. The low signal emitted by SHG images below the irradiated area demonstrated thermal damage of the collagen matrix. CLMS images of laser groups exhibited thicker and irregular resin-dentin interfaces than the control group. Regardless of the pulse duration, Er:YAG laser pre-treatment altered the organic matrix and HL formation which resulted in low µSBS values at 24 h. The alterations on dentin's organic structure did not jeopardize the µSBS after 1 year of saliva storage.

Optical coherence tomography and polarized light microscopy for the evaluation of artificial caries: a preliminary study.

This study was designed to investigate whether there is a correlation between the findings of optical coherence tomography (OCT) and polarized light microscopy (PLM) when these techniques are used to evaluate standard enamel white-spot lesions developed by distinct cariogenic challenges. Bovine enamel fragments (N = 168) were randomly allocated into 6 experimental groups according to the microbiologic model (Streptococcus mutans UA159, Streptococcus sobrinus ATCC 33478, or mixed S mutans and S sobrinus) and carbohydrate sources (1% sucrose or combined 1% sucrose and 1% starch). Specimens were examined by OCT and PLM every day within a period of 7 days. Five measurements of demineralization depth were recorded for each specimen, and means were calculated. Data were analyzed with analysis of variance and Tukey tests (α = 0.05), and a correlation test was performed. All cariogenic challenges created sub-superficial lesions. In both the OCT and PLM analyses, the demineralization depth reached its peak between days 6 and 7 of the cariogenic challenge, except for the group challenged with S sobrinus supplemented with combined sucrose and starch; for that group, demineralization peaked on day 5 in the OCT analysis. There was a significant correlation between OCT and PLM (P = 0.00; r = 0.842). This preliminary study suggests that OCT is a reliable, nondestructive method to measure the demineralization depth of enamel white-spot lesions, which can be useful for the laboratory and has potential for clinical studies. Using the 1% sucrose and S mutans model for 6 days is a simple and effective method to induce enamel caries-like lesions without compromising the depth and morphologic features of the obtained lesions.

Effects of different treatments on chemical and morphological features of eroded dentin.

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 < 0.0001). When the toothpaste and laser were combined, the number of occluded dentin tubules was higher when laser was performed first (ELS). A positive effect was found when the laser and toothpaste were combined.

Non-thermal plasma increase bond strength of zirconia to a resin cement / Plasma não-térmico aumenta a resistência de união da zircônia a um cimento resinoso

Objective: This study investigated the influence of different surface treatments on zirconia surface energy, roughness and microshear bond strength. Material and Methods: Forty eight slices of Yttriastabilized tetragonal zirconia polycrystal (Y-TZPVITA In-Ceram® YZ for inLab®) (6.4 x 3.2 x 1.6 mm) were divided into 3 groups according to the surface treatment (n = 16): YTZP_control -untreated; YTZP_plasma -surface treatment with non-thermal oxygen plasma; YTZP_primer - coating with ceramic primer. Surface energy (n = 6) was measured with a goniometer; and surface roughness (n = 10) was analyzed with a 3D profilometer were performed over zirconia surface. On the same specimens of surface roughness, on the treated zirconia's surface, resin cement (PANAVIA V5 - Kuraray Noritake Dental) was built up by inserting the resin cement into Tygon tubes (1 mm of internal diameter X 1 mm length). After 24h storage, microshear test was assessed. Data were analyzed by one-way ANOVA and Tukey posthoc test (p < 0.05). Results: Nonthermal oxygen plasma treated specimens exhibited higher statistically significant surface energy (p = 0.00) and bond strength (p = 0.00) when compared to control and primer groups. Roughness test (p = 0.897) could not detect statistical difference among the tested groups. Conclusion: Non-thermal oxygen plasma should be a suitable alternative for zirconia surface treatment prior to luting hence it improved microshear bond strength and provided higher surface energy without affecting surface roughness. (AU)

Objetivo: Este estudo investigou a influência de diferentes tratamentos de superfície na energia de superfície, rugosidade e resistência de união da zircônia. Material e Métodos: Quarenta e oito fatias de zircônia tetragonal policristalina estabilizada por ítria (Y-TZP - VITA InCeram® YZ for inLab®) (6,4 x 3,2 x 1,6 mm) foram divididas em 3 grupos de acordo com o tratamento de superfície (n = 16): YTZP_controle sem tratamento; YTZP_plasma - tratamento de superfície com plasma de oxigênio não térmico; YTZP_primer - aplicação de um primer cerâmico. A energia da superfície (n = 6) foi medida com o auxilio de um goniômetro; e a rugosidade superficial (n = 10) foi analisada com um perfilômetro 3D. Nos mesmos espécimes da rugosidade, prolongamentos de cimento resinoso (PANAVIA V5 - Kuraray Noritake Dental) foram construídos inserindo o cimento em micro túbulos de silicone (1mm de diâmetro interno de X 1 mm de comprimento). O teste de microcisalhamento foi realizado após 24h. Os dados foram analisados estatisticamente ANOVA um fator e teste auxiliar de Tukey (p < 0,05). Resultados: Os espécimes tratados com plasma de oxigênio apresentaram maiores valores de energia de superficie (p = 0,00) e resistência de união estatisticamente significante (p = 0,00) quando comparados aos grupos controle e do primer. A análise de rugosidade (p = 0,897) não detectou diferença estatística entre os grupos testados. Conclusão: O plasma não térmico pode ser uma alternativa para o tratamento de superfície de zircônia antes da cimentação, pois aumentou a resistência de união ao microcilsalhamento e proporcionou maior energia superficial sem afetar a rugosidade da superfície. (AU)

Bonding efficiency and durability: current possibilities.

Bonding plays a major role in dentistry nowadays. Dental adhesives are used in association with composites to solve many restorative issues. However, the wide variety of bonding agents currently available makes it difficult for clinicians to choose the best alternative in terms of material and technique, especially when different clinical situations are considered. Moreover, although bonding agents allow for a more conservative restorative approach, achieving a durable adhesive interface remains a matter of concern, and this mainly due to degradation of the bonding complex in the challenging oral environment. This review aims to present strategies that are being used or those still in development which may help to prevent degradation. It is fundamental that professionals are aware of these strategies to counteract degradation as much as possible. None of them are efficient to completely solve this problem, but they certainly represent reasonable alternatives to increase the lifetime of adhesive restorations.

Bonding efficiency and durability: current possibilities

Abstract Bonding plays a major role in dentistry nowadays. Dental adhesives are used in association with composites to solve many restorative issues. However, the wide variety of bonding agents currently available makes it difficult for clinicians to choose the best alternative in terms of material and technique, especially when different clinical situations are considered. Moreover, although bonding agents allow for a more conservative restorative approach, achieving a durable adhesive interface remains a matter of concern, and this mainly due to degradation of the bonding complex in the challenging oral environment. This review aims to present strategies that are being used or those still in development which may help to prevent degradation. It is fundamental that professionals are aware of these strategies to counteract degradation as much as possible. None of them are efficient to completely solve this problem, but they certainly represent reasonable alternatives to increase the lifetime of adhesive restorations.

Is It Necessary to Prepare the Enamel before Dental Bleaching?

The aim of this in vitro study was to assess the influence of distinct surface treatments on the microhardness and color of enamel that will be bleached. Surface treatments are tested, accordingly: G1, no treatment; G2, 2% sodium fluoride; G3, casein phosphopeptide paste; G4, 2% fluoride+Nd:YAG laser. Forty blocks from bovine teeth composed the sample that were tested in Knoop microhardness (n = 10) and in color change (n = 10). After 24 h, bleaching with 35% hydrogen peroxide was performed for 45 min. Microhardness and color changes (using parameters ΔE, ΔL, Δa, and Δb) were assessed before and after bleaching. The data were analyzed by two-way ANOVA and Tukey's test (p < 0.05). Despite all surface treatments, a reduction of enamel microhardness occurred immediately after bleaching in all groups, being greater in G1. Enamel color changed in all groups. Immediately after bleaching, there was a decrease on enamel microhardness. However, after 7 days, some of those specimens previously treated before bleaching significantly recovered their initial microhardness without influencing the esthetic results of bleaching.

Short-pulse Er:YAG laser increases bond strength of composite resin to sound and eroded dentin.

This study evaluated the influence of the irradiation with a short-pulse Er:YAG laser on the adhesion of composite resin to sound and eroded dentin (SD and ED). Forty-six samples of occlusal dentine, obtained from human molars, had half of their surface protected, while the other half was submitted to erosive cycles. Afterward, 23 samples were irradiated with Er:YAG laser, resulting in four experimental groups: SD, sound irradiated dentine (SID­Er:YAG, 50 µs 50 µs , 2 Hz, 80 mJ, and 12.6 J/cm 2 12.6 J/cm2 ), ED, and eroded irradiated dentin (EID­erosion + Er:YAG laser). A self-etching adhesive system was used, and then cylinders of composite resin were prepared. A microshear bond strength test was performed after 24 h storage (n=20 n=20 ). The morphology of SD and ED, with or without Er:YAG laser irradiation, was evaluated under scanning electron microscopy (n=3 n=3 ). Bond strength values (MPa) were subjected to analysis of variance followed by Tukey's test. Statistically significant differences were found among the experimental groups: SD (9.76±3.39 B 9.76±3.39 B ), SID (12.77±5.09 A 12.77±5.09 A ), ED (5.12±1.72 D 5.12±1.72 D ), and EID (7.62±3.39 C 7.62±3.39 C ). Even though erosion reduces the adhesion to dentin, the surface irradiation with a short-pulse Er:YAG laser increases adhesion to both ED and SD.

Adhesion of a self-etching adhesive to caries-affected dentin treated with different methods for caries removal: a preliminary study / Avaliação de um sistema adesivo autocondicionante em dentina afetada por cárie tratada por diferentes mecanismos de remoção: estudo preliminar

Objetivo: O objetivo deste estudo foi avaliar a adesão (RU) de sistemas autocondicionantes à dentina afetada por cárie (CAD) e dentina normal (ND), após diferentes técnicas de remoção de tecido cariado. Materiais e Métodos: Foram utilizados vinte e quatro molares humanos extraídos, com lesão de cárie oclusal. A amostra foi aleatoriamente dividida em 5 grupos, de acordo com o método de remoção do tecido cariado: G1 - controle negativo (sem remoção); G2 - disco abrasivo; G3 – broca de aço de baixa velocidade; G4 - laser Nd:YAG (21,2 J/cm2 ); G5 - laser Er:YAG (80,24 J/cm2 ). Dentinas normais e afetados / infectados foram tratadas com o sistema adesivo (Clearfil SE Bond) e coroas de resina foram construídas. Resultados: ANOVA um fator mostrou diferença estatisticamente significante entre os grupos experimentais (p < 0,001), com um valor menor para a dentina infectada (G1), quando comparado com todos os grupos experimentais. Maior RU foi observada para ND irradiada com laser Er:YAG, quando comparado a CAD. Para os espécimes tratados com broca e laser Nd:YAG, a RU em ND e CAD foi semelhante. Conclusão: a dentina infectada não é um substrato adequado para a adesão; laser de Nd:YAG e brocas de aço mostraram-se adequados como ferramenta de tratamento das dentinas normal e afetada prévio à instalação de restaurações adesivas. Contudo, ambas as dentinas tratadas pelos laser de Er:YAG, não interagiram adequadamente com o sistema auto-condicionante resultando em fraca adesão

Objective: The aim of this study was to evaluate the adhesion of a self-etching system to cariesaffected dentin (CAD) and sound dentin (SD) after different caries removal techniques by using microtensile bond strength test (μTBS). 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 21.2 J/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 < 0.001), with significantly lower results for infected dentin (G1), when compared to all other experimental groups. A statistically significant higher bond strength value was observed for SD irradiated with Er:YAG laser when compared to CAD. For bur and Nd:YAG laser specimens, SD and CAD showed the same bonding performance. Conclusion: infected dentin is not an adequate substrate for bonding; Nd:YAG laser and steel burs showed the same bonding performance for both SD and CAD; while both dentins, when irradiated by Er:YAG laser, did not adequately interact with self-etching system resulting in poor adhesion

Antimicrobial photodynamic therapy: a promise candidate for caries lesions treatment.

BACKGROUND: Antibacterial photodynamic therapy (aPDT) is a promising adjunctive therapy to the treatment of caries lesions, mainly in the minimally invasive approach to preserve dental tissue and favor its repair. Here we analyzed both the efficacy of aPDT in reducing the bacterial load in cariogenic biofilms and the indirect effect of noxious components produced by aPDT on the viability of dental pulp cells. METHODS: The aPDT protocol was established using 0.025g/mL methylene blue (MB) and 5min pre-irradiation time. A continuous-wave diode laser (660nm, 0.04cm(2) spot size, 40mW, 60s, 60J/cm(2) and 2.4J) was used in punctual and distance modes to excite the MB. The protocol was first tested against Streptococcus mutans (U159) biofilms produced in 96-well microplates, and then evaluated on caries-like affected human dentin discs of three thicknesses. The number of colony forming units (CFU) was compared between groups. Discs were then assembled in metallic inserts to produce an artificial pulp chamber and allow investigation of the indirect effects of aPDT on dental pulp cells by the 3-(4,5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide (MTT) assay. Data were analyzed using Student's t test or one-way analysis of variance (ANOVA) followed by the Tukey's test at a significance level of 5%. RESULTS: Bacterial load reduction was observed in biofilms produced both in the microplates (p<0.05) and on the caries-like affected dentin discs (81.01% or mean reduction of log21.010±0.1548; p=0.0029). The cell viability of aPDT and control group was similar (p>0.05). CONCLUSIONS: aPDT may be considered a promise adjunctive therapy for deep carious lesions.

Laser phototherapy enhances mesenchymal stem cells survival in response to the dental adhesives.

BACKGROUND: We investigated the influence of laser phototherapy (LPT) on the survival of human mesenchymal stem cells (MSCs) submitted to substances leached from dental adhesives. METHOD: MSCs were isolated and characterized. Oral mucosa fibroblasts and osteoblast-like cells were used as comparative controls. Cultured medium conditioned with two adhesive systems was applied to the cultures. Cell monolayers were exposed or not to LPT. Laser irradiations were performed using a red laser (GaAlAs, 780 nm, 0.04 cm(2), 40 mW, 1 W/cm(2), 0.4 J, 10 seconds, 1 point, 10 J/cm(2)). After 24 h, cell viability was assessed by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide reduction assay. Data were statistically compared by ANOVA followed by Tukey's test (P < 0.05). RESULTS: Different cell types showed different viabilities in response to the same materials. Substances leached from adhesives were less cytotoxic to MSCs than to other cell types. Substances leached from Clearfil SE Bond were highly cytotoxic to all cell types tested, except to the MSCs when applied polymerized and in association with LPT. LPT was unable to significantly increase the cell viability of fibroblasts and osteoblast-like cells submitted to the dental adhesives. CONCLUSION: LPT enhances mesenchymal stem cells survival in response to substances leached from dental adhesives.