Biomodification of eroded and abraded dentin with epigallocatechin-3-gallate (EGCG).

This study aimed to evaluate in vitro the effects of epigallocatechin-3-gallate (EGCG) as a biomodifier of eroded and abraded dentin. Forty dentin specimens were obtained from the buccal surface of bovine teeth. The specimens were randomly distributed in 4 groups according to dentin substrate: sound or eroded/abraded and dentin biomodification: with 0.5% EGCG and no biomodification (control group). Specimens were subdivided according to aging time: 24 h and 3 months for the analysis of microtensile bond strength (n = 10), morphology of the adhesive interface by SEM (n = 3) and dentin micropermeability by fluorescence microscope (n = 8). Statistical analysis was performed using SPSS system version 20.0 with a significance level of 5%. The results revealed that the control group with eroded-abraded dentin exhibited the lowest bond strength values at 24 h and 3 months. However, the application of 0.5% EGCG as a biomodifier significantly increased bond strength on both sound and eroded-abraded substrates. After 3 months, all groups exhibited an adhesive interface with a more intense fluorescence in the adhesive layer, indicating an increase in porosity at the interface. In conclusion, the EGCG application as a biomodifier enhanced bond strength on both sound and eroded-abraded dentin substrates, however, adhesive interfaces are more regular when restorations are performed on sound dentin, regardless of the biomodification with EGCG.

In vitro antibacterial activity of green tea-loaded chitosan nanoparticles on caries-related microorganisms and dentin after Er:YAG laser caries removal.

This study aimed to determine the inhibitory effects of green tea (Gt), EGCG, and nanoformulations containing chitosan (Nchi) and chitosan+green tea (Nchi+Gt) against Streptococcus mutans and Lactobacillus casei. In addition, the antibacterial effect of nanoformulations was evaluated directly on dentin after the selective removal of carious lesion. At first, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against S. mutans and L. casei isolates were investigated. In parallel, dentin specimens were exposed to S. mutans to induce carious lesions. Soft dentin was selectively removed by Er:YAG laser (n=33) or bur (n=33). Remaining dentin was biomodified with Nchi (n=11) or Gt+Nchi (n=11). Control group (n=11) did not receive any treatment. Dentin scraps were collected at three time points. Microbiological analyses were conducted and evaluated by agar plate counts. Gt at 1:32 dilution inhibited S. mutans growth while 1:16 was efficient against L. casei. EGCG at 1:4 dilution completely inhibited S. mutans and L. casei growth. Independently of the association with Gt, Nchi completely inhibited S. mutans at 1:4 dilution. For L. casei, different concentrations of Nchi (1:32) and Nchi+Gt (1:8) were required to inhibit cell growth. After selective carious removal, viability of S. mutans decreased (p<0.001), without difference between bur and Er:YAG laser (p>0.05). Treatment with Nchi and Nchi+Gt did not influence the microbial load of S. mutans on dentin (p>0.05). Although variations in concentrations were noticed, all compounds showed antibacterial activity against S. mutans and L. casei. Both bur and Er:YAG laser have effectively removed soft dentin and reduced S. mutans counts. Nanoformulations did not promote any additional antibacterial effect in the remaining dentin.

Longitudinal analyses of composite resin restoration on erosive lesions: effect of dentin treatment with a chitosan nanoformulation containing green tea

Aim To evaluate the influence of the biomodification of erosive lesions with a chitosan nanoformulation containing green tea (NanoCsQ) on the clinical performance of a composite resin. Methods The study was performed in a split-mouth, randomized and double-blinded model with 20 patients with 40 erosive lesions. The patient's teeth were randomized into two groups (n=20) according to the surface treatment: 1) Without biomodification (control), and 2) Biomodification with NanoCsQ solution (experimental). The lesions were restored with adhesive (Tetric N-bond, Ivoclar) and composite resin (IPS Empress Direct, Ivoclar). The restorations were polished and 7 days (baseline), 6 months, and 12 months later were evaluated according to the United States Public Health Service (USPHS) modified criteria, using clinical exam and photographics. Data were analyzed by Friedman's and Wilcoxon signed-rank tests. Results No significant differences were found between the control and experimental groups (p=0.423), and also among the follow-up periods (baseline, six months, and 12 months) (p=0.50). Regarding the retention criteria, 90% of the restoration had an alpha score in the control group. Only 10% of the restorations without biomodification (control) had a score charlie at the 12-month follow-up. None of the patients reported post-operatory sensitivity. Conclusion The NanoCsQ solution did not negatively affect the performance of the composite resin restorations after 12 months.

Photoinactivation of multispecies cariogenic biofilm mediated by aluminum phthalocyanine chloride encapsulated in chitosan nanoparticles.

This study aimed to characterize the aluminum phthalocyanine chloride (AlClPc) encapsulated in chitosan nanoparticles (CN) and apply it in antimicrobial photodynamic therapy (aPDT) on multispecies biofilm composed of Streptococcus mutans, Lactobacillus casei, and Candida albicans to analyze the antimicrobial activity and lactate production after treatment. Biofilms were formed in 24-well polystyrene plates at 37 °C for 48 h under microaerophilia. The following groups were evaluated (n = 9): as a positive control, 0.12% chlorhexidine gluconate (CHX); phosphate-buffered saline (PBS) as a negative control; 2.5% CN as release vehicle control; the dark toxicity control of the formulations used (AlClPc and AlClPc + CN) was verified in the absence of light; for aPDT, after 30 min incubation time, the photosensitizers at a final concentration of 5.8 × 10-3 mg/mL were photoirradiated for 1 min by visible light using a LED device (AlClPc + L and AlClPc + CN + L) with 660 nm at the energy density of 100 J/cm2. An in vitro kit was used to measure lactate. The biofilm composition and morphology were observed by scanning electron microscopy (SEM). The antimicrobial activity was analyzed by quantifying colony forming units per mL (CFU/mL) of each microorganism. Bacterial load between groups was analyzed by ANOVA and Tukey HSD tests (α = 0.05). A lower lactate dosage was observed in the aPDT AlClPc + CN + L and CHX groups compared to the CN and AlClPc groups. The aPDT mediated by the nanoconjugate AlClPc + CN + L showed a significant reduction in the viability of S. mutans (3.18 log10 CFU/mL), L. casei (4.91 log10 CFU/mL), and C. albicans (2.09 log10 CFU/mL) compared to the negative control PBS (p < 0.05). aPDT using isolated AlClPc was similar to PBS to the three microorganisms (p > 0.05). The aPDT mediated by the nanoconjugate AlClPc + CN + L was efficient against the biofilm of S. mutans, L. casei, and C. albicans.

Effect of desensitizing dentifrices on eroded dentin wettability / Efeito de dentifrícios dessensibilizantes na molhabilidade da dentina erodida

Objective: To analyze the wettability on the surface of eroded dentin in teeth submitted to abrasive wear with desensitizing dentifrices. Material and Methods: Bovine dentin specimens were polished and immersed in 10 mL of citric acid (pH=3.2) for 2 h. The eroded specimens were submitted to mechanic brushing according to the 4 dentifrices adopted: Colgate Total (control); Colgate Sensitive Pro-Relief; Sensodyne Repair & Protect; or Sensodyne Rapid Relief. Afterwards, it was conditioned in 37% aqueous phosphoric acid solution. Wettability of 80 specimens (n=10) brushed for 7 or 21 days was evaluated by measuring the contact angle between the dentin surface and a drop of the adhesive Single Bond Universal® (3M) with a goniometer. Changes in the surface morphology of 12 specimens (n = 3) brushed for 21 days were followed by confocal laser scanning microscopy (CLSM). Data were analyzed by two-way ANOVA and Tukey test (p > 0.05). Results: Groups treated with desensitizing dentifrices did not differ significantly (p ≤ 0.05). Surface treatment and abrasive wear did not interact significantly (p ≤ 0.05). Brushing along 7 days gave the smallest contact angle value (p ≥ 0.05). CLSM images showed morphological changes for all the groups. Conclusion: The desensitizing dentifrices did not interfere in eroded dentin wettability after brushing along 7 or 21 days. Brushing with any of the dentifrices along 21 days promoted open dentinal tubules.(AU)

Objetivo: Analisar a aplicação de um adesivo na superfície de dentina erodida em dentes submetidos ao desgaste abrasivo com agentes dessensibilizantes. Material e Métodos: Espécimes de dentina bovina foram polidos e imersos em 10 mL de ácido cítrico (pH=3,2) por 2 h. Os espécimes erodidos foram submetidos à escovação mecânica de acordo com os 4 dentifrícios adotados: Colgate Total (controle); Colgate Sensitive Pro-Alívio; Sensodyne Repair & Protect; ou Sensodyne Rápido Alívio. Em seguida, foram condicionados em ácido fosfórico a 37%. A molhabilidade de 80 espécimes (n=10) escovados por 7 ou 21 dias foi avaliada medindo-se o ângulo de contato entre a superfície dentinária com uma gota do adesivo Single Bond Universal® (3M) por um goniômetro. Alterações na morfologia da superfície de 12 espécimes (n = 3) escovados por 21 dias foram seguidos por Microscopia Confocal de Varredura a Laser (MCVL). Os dados foram analisados por ANOVA dois fatores e teste de Tukey (p > 0,05). Resultados: Os grupos tratados com dentifrícios dessensibilizantes não diferiram significativamente (p ≤ 0,05). O tratamento de superfície e o desgaste abrasivo não interagiram significativamente (p ≤ 0,05). A escovação ao longo de 7 dias apresentou o menor valor de ângulo de contato (p ≥ 0,05). As imagens do MCVL mostraram alterações morfológicas para todos os grupos. Conclusão: Os dentifrícios dessensibilizantes não interferiram na molhabilidade da dentina erodida após escovação ao longo de 7 ou 21 dias. A escovação com qualquer um dos dentifrícios ao longo de 21 dias promoveu a abertura dos túbulos dentinários (AU)

Effect of green tea-loaded chitosan nanoparticles on leathery dentin microhardness.

The purpose of this study was to assess the effect of a chitosan-based nanoformulation containing green tea on leathery (remaining) dentin subsurface microhardness. Size distribution, polydispersity index (PDI) and zeta potential (mV) of nanoformulations were previously determined by dynamic light scattering (DLS). Human dentin specimens were exposed to Streptococcus mutans for 14 d. Soft dentin were selectively removed by Er:YAG laser (n = 30) or bur (n = 30). Remaining dentin was biomodified with chitosan nanoparticles (Nchi, n = 10) or green tea-loaded chitosan nanoparticles (Gt + Nchi, n = 10) for 1 min. Control group (n = 10) did not receive any treatment. Subsurface microhardness (Knoop) was evaluated in hard (sound) and soft dentin, and then, in leathery dentin and after its biomodification, at depths of 30, 60 and 90 µm from the surface. Nchi reached an average size of ≤ 300 nm, PDI varied between 0.311 and 0.422, and zeta potential around + 30 mV. Gt + Nchi reached an average size of ≤ 350 nm, PDI < 0.45, and zeta potential around + 40 mV. Soft dentin showed significantly reduced microhardness at all depths (p > 0.05). The subsurface microhardness was independent of choice of excavation method (p > 0.05). At 30 µm from the surface, Gt + Nchi increased the leathery dentin microhardness compared to untreated group (p < 0.05). Nchi promoted intermediate values (p > 0.05). Both nanoformulations showed an average size less than 350 nm with nanoparticles of different sizes and stability along the 90-day period evaluated. Subsurface microhardness of bur-treated and laser-irradiated dentin was similar. At 30 µm, the biomodification with Gt + Nchi improved the microhardness of leathery dentin, independently of caries excavation method used.

Influence of nanoparticulated chitosan on the biomodification of eroded dentin: clinical and photographic longitudinal analysis of restorations.

To evaluate the influence of the pre-treatment with 2.5% nanoparticulate chitosan (2.5% NanoChi) solution on eroded dentin before the restorative dental treatment. The sample consisted of 22 patients (age between 33 and 52 years) with shallow or medium erosion lesions located in two homologous teeth. The teeth were randomly assigned according to dentin treatment: with 2.5% NanoChi and without with chitosan (control). The NanoChi were applied immediately after acid etching. The teeth were restored with Single Bond Universal (3 M) and Charisma resin (Kulzer). Analyzes were done using modified USPHS (retention, secondary caries, marginal adaptation, and sensitivity) and photographic (color, marginal pigmentation, and anatomical form) criteria at 7 days (baseline) and 1 year. Population demographics, Kaplan-Meier estimates and log-rank test (Mantel-Cox) were calculated for 1 year (α = 0.05). No significant difference was found in the survival rates between groups (p > 0.05) at 7 days and 1 year after treatment. After 7 days, 100% of the restorations were scored as Alpha on all criteria. After 1 year, 91% of the NanoChi restorations were scored as Alpha and 9% as Charlie for the retention, marginal adaptation, and anatomical form criteria, while 86% of the control restorations (without NanoChi) received the Alpha score and 14% received the Charlie. Secondary caries, sensitivity, color, and marginal pigmentation criteria were scored as Alpha in 100% of the restorations. The biomodification of eroded dentin with 2.5% NanoChi did not influence the survival of the restorations after 1 year. The application of 2.5% NanoChi on eroded dentin did not increase failures of resin restorations after 1 year and it can be used as a pre-treatment solution.

Conjugate of chitosan nanoparticles with chloroaluminium phthalocyanine: Synthesis, characterization and photoinactivation of Streptococcus mutans biofilm.

BACKGROUND: Antimicrobial photodynamic therapy (aPDT) using chloroaluminium phthalocyanine (ClAlPc) has high oxidative power allowing for the control of biofilms, especially when the photosensitizer is administered in an appropriate release vehicle. This study aimed to develop/characterize the ClAlPc encapsulated in chitosan nanoparticles (CSNPs), and evaluate its antimicrobial properties against S. mutans biofilms. METHODS: CSNPs were prepared by ion gelation, and characterization studies included particle size, polydispersion index (IPd), zeta potential, accelerated stability, absorption spectrum and ClAlPc quantification. The S. mutans biofilms were formed in bovine dentin blocks at 37 °C for 48 h under microaerophilic conditions. 8 µM ClAlPc was combined with a diode laser (InGaAlP) at 660 nm and 100 J/cm2. The aPDT toxicity was verified by dark phototoxicity. The antimicrobial activity was verified by CFU/mL and biofilm was analyzed by scanning electron microscopy (SEM). The number of viable bacteria was analyzed by ANOVA and Tukey HSD tests (α = 0.05). RESULTS: The characterization revealed that the ClAlPc nanoparticles were found in nanometer-scale with adequate photophysical and photochemical properties. The aPDT mediated by ClAlPc + CSNPs nanoconjugate showed a significant reduction in the viability of S. mutans (1log10 CFU/mL) compared to the negative control (PBS, p < 0.05). The aPDT mediated by ClAlPc was similar to PBS (p > 0.05). SEM revealed change in biofilm morphology following the treatment of bacteria with aPDT ClAlPc + CSNPs. Cells were arranged as single or in shorted chains. Irregular shapes of S. mutans were found. CONCLUSION: ClAlPc nanoparticles are considered stable and aPDT mediated by ClAlPc + CSNPs nanoconjugate was effective against S. mutans biofilm.

The Impact of CO2 Laser Treatment and Acidulated Phosphate Fluoride on Enamel Demineralization and Biofilm Formation.

Introduction: This study evaluated the impact of CO2 laser treatment and acidulated phosphate fluoride (APF) on enamel demineralization and biofilm formation, using in vitro and in situ designs. Methods: Demineralized enamel slabs were distributed among 8 groups: placebo, placebo + continuous CO2 laser, placebo + repeated CO2 laser, placebo + ultrapulsed CO2 laser, 1.23% APF, APF + continuous CO2 laser, APF + repeated CO2 laser and APF + ultrapulsed CO2 laser. In the in vitro study, 15 enamel slabs from each group were subjected to a pH-cycling regimen for 14 days. In the cross over in situ design, 11 volunteers wore palatal appliances with demineralized enamel slabs for 2 periods of 14 days each. Drops of sucrose solution were dripped onto enamel slabs 8×/day. Biofilms formed on slabs were collected and the colony-forming units (CFU) of Streptococcus mutans and Lactobacillus were determined. Results: For both in vitro and in situ studies, there was no significant difference between treatments (P>0.05). However, all treatments increased microhardness of demineralized enamel (P<0.05). After a further in situ cariogenic challenge, with the exception of the placebo, all treatments maintained microhardness values (P<0.05). Microbiological analysis showed no difference in Streptococcus mutans (P>0.05) or Lactobacillus (P>0.05) counts between groups. Conclusion: The results suggest that APF gel combined with the CO2 laser, regardless of the pulse emission mode used, was effective in controlling enamel demineralization, but none of the tested treatments was able to prevent bacterial colonization.

Selective Removal of Necrotic Dentin in Primary Teeth Using Laser Irradiation: One-Year Clinical Evaluation of Composite Restorations.

Introduction: This study aimed to evaluate the child's salivary cortisol levels, clinical performance and marginal adaptation of restorations after selective removal of necrotic dentin in primary teeth using Er: YAG laser irradiation. Methods: A double-blind clinical study was performed in children at 7-10 years. Children who had at least 2 teeth with carious lesions involving the occlusal and proximal surfaces of primary molars counterparts were selected. Removal of necrotic dentin was performed by 2 methods: Er: YAG laser irradiation and bur-preparation. Cortisol levels (n =24) was evaluated by ELISA. Clinical analysis (n =20) was performed after the restorations polish, 6 and 12 months after restorative procedure using United States Public Health Service (USPHS) method and photographs. Scanning electron microscopy (SEM) was used to analyz the marginal gap formation (n =20). The analysis of the data was performed by 95% confidence interval, Shapiro-Wilk test, Friedman and Wilcoxon post hoc tests (α =5%). Results: Cortisol levels were higher during selective removal of necrotic dentin, regardless of the method used (P>0.05). After 12 months, there was no evidence of the difference in the restorations performed on cavities prepared by both methods. SEM analysis revealed that the laser-irradiated teeth showed 10% of gaps in the full extent of restoration. For bur-prepared teeth, 20% of gaps were found at the cavosurface margin. Conclusion: The salivary cortisol levels on children that received Er: YAG laser irradiation for removal the necrotic dentin was similar to the control group. Class II restorations evaluated after 1 year period did not suffer interference by the use of Er: YAG laser irradiation.

Influence of antimicrobial photodynamic therapy in carious lesion. Randomized split-mouth clinical trial in primary molars.

BACKGROUND: The literature presents many studies regarding photodynamic antimicrobial therapy (aPDT). However, the great variety of protocols to be used can directly influence its effectiveness in reducing microorganisms. The aim of this randomized split-mouth clinical study was to evaluate the effect of aPDT in the reduction of Streptococcus mutans and their effect on restorations performed. METHODS: Twenty children between 6 and 8 years old with active caries and dentin cavitation, located on the occlusal surface of homologous primary molars were included. The selective removal of carious tissue was performed in both molars, than one was subsequently restored and the other received aPDT treatment on the affected dentin with low intensity laser (InGaAlP) associated to 0.005% methylene blue photosensitizer before restoration. Dentin collections were performed only in the tooth submitted to aPDT in three moments: before and after selective caries removal and after application of aPDT. The restorations were analyzed after polishing and after 6 months using United States Public Health Service (USPHS) method. Data were analyzed using ANOVA with repeated measures and Bonferroni post-hoc test with a significance level of 5%. RESULTS: There was a significant reduction on the amount of microorganisms after selective caries removal (p = 0.04) and also after the application of aPDT (p = 0.01). The reduction of S. mutans CFU was of 76.4% after caries removal, but associated with aPDT was 92.6%. After 6 months of clinical evaluation, no difference between groups was found for retention, marginal adaptation, color, marginal discoloration, and secondary caries. CONCLUSIONS: aPDT can be used as an additional treatment against cariogenic microorganisms after selective caries removal without compromising composite resin restorations.

Effect of Er:YAG laser irradiation and chitosan biomodification on the stability of resin/demineralized bovine dentin bond.

OBJECTIVE: The purpose of this study was to evaluate the effect of Er:YAG laser for selective removal of carious lesion, followed by biomodification with chitosan on the microtensile bond strength (µTBS), adhesive interface, dry mass loss and hydroxyproline release (HYP). METHODS: Artificial lesions were created in 104 bovine dentin blocks. Blocks were divided according to caries removal method: bur or Er:YAG laser. Seventy-six blocks were acid etched and subdivided according to dentin biomodification: no chitosan and 2.5% chitosan. Composite resin restorations were performed. Blocks were sectioned into beams and stored in water. After 24 h, 6 and 12 months, beams were submitted to µTBS test (n = 10) and analysis of adhesive interface by SEM (n = 3). The other 28 blocks were sectioned into beams and initial dry mass (DM) was determined (n = 7). Beams were stored and after 7 days, DM was redetermined. HYP release (n = 7) was evaluated by ELISA. Data were analyzed by ANOVA and Bonferroni's tests (α = 0.05). RESULTS: After 24 h, the highest µTBS was found for bur (p < 0.001). After 6 months, methods were similar (p = 0.432). After 12 months, laser-irradiated dentin showed the highest µTBS values (p = 0.025). Chitosan promoted higher µTBS values after 6 (p = 0.011) and 12 months (p < 0.001) preserving adhesive interface. Dry mass loss and HYP release were not influenced (p > 0.05) by caries removal method or by dentin biomodification. CONCLUSION: The bond strength to demineralized dentin reduced over 50% in all groups after water storage. From 6 months of water storage, Er:YAG laser irradiation and biomodification with chitosan maintained the stability of the resin-dentin bonds, but did not influence dry mass loss and HYP release.

Differential effects of natural Curcumin and chemically modified curcumin on inflammation and bone resorption in model of experimental periodontitis.

OBJECTIVE: The purpose of this study was to compare the effects of the oral administration of natural curcumin and a chemically modified curcumin (CMC2.24) on osteoclast-mediated bone resorption, apoptosis, and inflammation in a murine model of experimental periodontal disease. DESIGN: Fifty male rats were distributed among the following treatment groups: (i) 2% carboxymethylcellulose, (ii) CMC2.24 30 mg/kg body weight, (iii) Curcumin 100 mg/kg body weight and (iv) no treatment. Compounds were administered daily by oral intubation over a 15-day period of time. Periodontal disease was induced by injections of LPS (lipopolysaccharide) into the gingival tissues three times per week. Contralateral sides were injected with the same volume of PBS (phosphate buffered saline) vehicle. After 15 days, hemimaxillae and gingival tissues were harvested. Bone resorption was assessed by µCT (microcomputer tomography). Formalin-fixed, paraffin embedded histological sections were stained with haematoxylin/eosin (H/E) for the assessment of cellular infiltrate or subjected to immunohistochemistry for detecting TRAP (tartrate-resistant acid phosphatase)-positive cells and caspase-3. Apoptosis was assessed in the gingival tissues by DNA fragmentation. RESULTS: CMC2.24 and curcumin caused a significant reduction of the inflammatory cell infiltrate, however µCT analysis showed that only CMC2.24 reduced bone resorption and the number of TRAP-positive multinucleated cells (osteoclasts). Curcumin, but not CMC2.24, significantly reduced the number of apoptotic cells in the gingival tissues and of osteocytes in the alveolar bone crest. CONCLUSIONS: The results suggest that CMC2.24 and curcumin inhibit inflammation by different mechanisms, but only CMC2.24 was capable of reducing alveolar bone resorption in the LPS-induced model of periodontitis.

Human teeth biobank: Microbiological analysis of the teeth storage solution.

The cross-infections may occur during handling of dental elements, affecting the health of dental practitioners and researchers. This study aimed to analyze the influence of the storage medium temperature on the bacterial contingent of the human teeth used for research purposes. Thirty human teeth were donated to the Human Teeth Biobank immediately after extraction. The teeth were cleaned with tap water and neutral soap. The teeth were randomly distributed according to the temperature of the storage solution (deionized water): at 4 °C (refrigerator) or at -10 °C (freezer) and were stored individually in sterile vials during 60 days. After this period, a microbiological analysis (CFU/mL) of the storage solutions was performed and teeth were submitted to SEM analysis. Data were analyzed by Kruskal-Wallis test followed by Dunn's post-test (p ≤ .05). Total aerobic bacteria ranged from 5.8 to 8.4 log10 CFU/mL for refrigerated solution and from 1.9 to 8.5 log10 CFU/mL for frozen solution. No statistical differences were found between the storage solutions (p > .05). The counts of Streptococcus spp., Lactobacillus spp., and Staphylococcus spp. were similar for both storage solutions (p > .05). SEM analysis showed spiral- and rod-shaped bacteria attached on teeth stored under 4 °C, which may suggest the presence of Treponema spp. and Lactobacillus spp. Similar morphological forms were found on teeth stored under -10 °C. A biofilm organized in honeycomb-like form was found in the frozen teeth. Cocci were eventually found in all the samples. It was concluded that bacterial growth and survival were not influenced by the temperature of the teeth storage solution.

Wettability and surface morphology of eroded dentin treated with chitosan.

OBJECTIVE: To assess the effect of chitosan, at concentrations of 2.5% and 5.0%, on the wettability of the eroded dentin, followed by analysis of surface morphology by SEM. METHODS: 104 bovine dentin slabs were ground, polished and then immersed in 20mL of citric acid (pH=3.2) under continuous stirring for 2h. Specimens were randomly divided according to the dentin substrate: sound and eroded, and then, subdivided into 4 groups (n=10): without rewetting (control), 1% acetic acid, 2.5% chitosan and 5.0% chitosan. Then, a drop of the adhesive system Single Bond 2 (3M) was deposited onto surface of each specimen. The contact angle between dentin surface and the adhesive system was measured by using a goniometer. The other 24 specimens were subjected to analysis under SEM. Statistical analysis was performed using the normality test (Kolmogorov-Smirnov) and Analysis of Variance (ANOVA) (p>0.05). RESULTS: No differences were found between the angles produced on the eroded dentin rewetting with chitosan at the concentrations of 2.5% and 5%. CONCLUSION: The chitosan, regardless of the concentration used, did not influence the eroded dentin wettability. Through SEM analysis, it was found particles of chitosan deposited on the surface and within the dentinal tubules.

Clinical evaluation of composite restorations in Er:YAG laser-prepared cavities re-wetting with chlorhexidine.

OBJECTIVES: The objective of this study was to evaluate longitudinally the composite restorations, performed in cavities prepared by Er:YAG or conventional bur, and dentin re-wetting with water or chlorhexidine. MATERIALS AND METHODS: Twenty individuals with four active caries with cavitation reaching the dentin located on the occlusal surface of molars counterparts are selected. The teeth of each individual were randomly assigned into four groups: (I) Er:YAG laser (260 mJ/4 Hz) re-wetting with chlorhexidine, (II) Er:YAG laser (260 mJ/4 Hz) re-wetting with deionized water, (III) conventional method re-wetting with chlorhexidine, and (IV) conventional method re-wetting with deionized water. The teeth were isolated, prepared cavities, phosphoric acid etching, and re-wetting according to previously assigned method. Restoration was performed employing the Single Bond 2 and Z350XT resin. Clinical follow-up was held after the polishing of the restoration (baseline) and 6 and 12 months of the making of the restoration using the modified USPHS criteria. The restorations were qualitatively analyzed by means of photographs. In the evaluation period, replicas of the restorations were analyzed by SEM. Data were analyzed by statistics using chi-square test (p < 0.05). RESULTS: After 12 months of clinical evaluation, groups prepared with laser and re-wetting with chlorhexidine and water showed the lowest marginal staining value. There was no statistical difference between the groups for other factors. SEM analysis revealed that a non-expressive amount of restorations showed gaps and irregularities of tooth-restoration interface after 6 and 12 months compared to the baseline. CONCLUSION: The restorations performed in laser-prepared cavities, regardless of the re-wetting, presented the best clinical performance over the evaluated period. CLINICAL RELEVANCE: Laser-prepared teeth, regardless of re-wetting, showed greater resistance to marginal discoloration.

Sub ablative Er: YAG laser irradiation on surface roughness of eroded dental enamel.

OBJECTIVE: This study evaluated the effects of Er:YAG laser irradiation applied at varying pulse repetition rate on the surface roughness of eroded enamel. METHODS: Bovine enamel slabs (n = 10) were embedded in polyester resin, ground, and polished. To erosive challenges, specimens were immersed two times per day in 20mL of concentrated orange juice (pH = 3.84) under agitation, during a two-day period. Specimens were randomly assigned to irradiation with the Er:YAG laser (focused mode, pulse energy of 60 mJ and energy density of 3.79 J/cm(2) ) operating at 1, 2, 3, or 4 Hz. The control group was left nonirradiated. Surface roughness measurements were recorded post erosion-like formation and further erosive episodes by a profilometer and observed through atomic force microscopy (AFM). RESULTS: Analysis of variance revealed that the control group showed the lowest surface roughness, while laser-irradiated substrates did not differ from each other following post erosion-like lesion formation. According to analysis of covariance, at further erosive episodes, the control group demonstrated lower surface roughness (P > 0.05), than any of the irradiated groups (P < 0.05). CONCLUSIONS: The pulse repetition rate of the Er:YAG laser did not affect roughness of dental enamel eroded. The AFM images showed that the specimens irradiated by the Er:YAG laser at 1 Hz presented a less rough surface than those irradiated at 2, 3, and 4 Hz.