Optimizing the use of low-frequency ultrasound for bacterial detachment of in vivo biofilms in dental research-a methodological study.

OBJECTIVES: Low-frequency, low-intensity ultrasound is commonly utilized in various dental research fields to remove biofilms from surfaces, but no clear recommendation exists in dental studies so far. Therefore, this study aims to optimize the sonication procedure for the dental field to efficiently detach bacteria while preserving viability. MATERIALS AND METHODS: Initial biofilm was formed in vivo on bovine enamel slabs (n = 6) which were worn by four healthy participants for 4 h and 24 h. The enamel slabs covered with biofilm were then ultrasonicated ex vivo for various time periods (0, 1, 2, 4, 6 min). Colony-forming units were determined for quantification, and bacteria were identified using MALDI-TOF. Scanning electron microscopic images were taken to also examine the efficiency of ultrasonications for different time periods. RESULTS: Ultrasonication for 1 min resulted in the highest bacterial counts, with at least 4.5-fold number compared to the non-sonicated control (p < 0.05). Most bacteria were detached within the first 2 min of sonication, but there were still bacteria detached afterwards, although significantly fewer (p < 0.0001). The highest bacterial diversity was observed after 1 and 2 min of sonication (p < 0.03). Longer sonication periods negatively affected bacterial counts of anaerobes, Gram-negative bacteria, and bacilli. Scanning electron microscopic images demonstrated the ability of ultrasound to desorb microorganisms, as well as revealing cell damage and remaining bacteria. CONCLUSIONS: With the use of low-frequency, low-intensity ultrasound, significantly higher bacterial counts and diversity can be reached. A shorter sonication time of 1 min shows the best results overall. CLINICAL RELEVANCE: This standardization is recommended to study initial oral biofilms aged up to 24 h to maximize the outcome of experiments and lead to better comparability of studies.

The Wear Behavior of Glass-Ceramic CAD/CAM Blocks against Bovine Enamel.

The wear of enamel and crown restorative materials often occur by occlusion. The purpose of this study was to evaluate the wear volume between glass-ceramics used for CAD/CAM blocks (lithium disilicate: Initial LiSi block (LIS), IPS e.max CAD (IPS), zirconia-reinforced lithium silicate glass-ceramics: Celtra DUO (DUO), VITA Suprinity (VITS) and feldspar-based glass-ceramics: Vitablocs Mark II (MAK)) and bovine tooth enamel using a two-body wear test, the hardness, three-point bending strength, micro-structure and the element components of glass-ceramics. The data were analyzed using a one-way analysis of variance and Tukey's multiple comparison test (α = 0.05). IPS and DUO with relatively large size crystal gain had significantly larger abrader wear volumes. Zirconia-reinforced lithium silicate glass-ceramics (DUO, VITS) caused significantly greater wear volume in antagonist enamel. MAK with scale-shape crystals grains produced distinct scratches after wear tests, both in the material itself and in the enamel. A strong correlation between the mechanical properties (hardness, three-point bending strength) and wear volume could not be confirmed. The type of glass-ceramic, size, and shape of the crystal grains affected the wear behavior of the glass-ceramics for CAD/CAM blocks. Therefore, dentists should consider that wear behavior varies with crystal structure, size, and shape in glass-ceramics for CAD/CAM blocks.

Adhesion and whitening efficacy of P11-4 self-assembling peptide and HAP suspension after using NaOCl as a pre-treatment agent.

BACKGROUND: This study evaluated the adhesion and whitening efficacy of a mixture of hydroxyapatite and P11-4 self-assembling peptide (HAP-peptide) on bovine enamel after pre-treatment with low-concentrated sodium hypochlorite (NaOCl). METHODS: Fifty-two caries-free bovine incisors were selected. 50 teeth were randomly allocated to five groups (n = 10). The first group was treated with a mixture of 6.25 wt% HAP and 5 ml P11-4 peptide, using NaOCl 3% as pre-treatment. Second, third and fourth groups were treated with 6.25 wt% HAP, 5 ml P11-4 peptide, and NaOCl 3%, respectively. In the fifth group, only water was applied (control group). The color of samples was measured using a spectrophotometer (USB4000-VIS-NIR-ES, Ostfildern, Germany). To evaluate color changes, ΔE values were statistically analyzed. Finally, adherence of HAP particles on two enamel surfaces with and without pre-treatment with NaOCl was analyzed with SEM. RESULTS: It was observed that the ΔE of the HAP-peptide suspension after pre-treatment with NaOCl was significantly stronger than the control group. In contrast, the overall color changes of separate applications of HAP, peptide, and NaOCl did not differ notably from the control group. SEM observations confirmed that pre-treatment with NaOCl resulted in a more pronounced coverage of HAP on the enamel surface. CONCLUSIONS: Pre-treatment with a low-concentrated NaOCl enhanced the adherence of the HAP layer on the enamel surface, resulting in a stronger whitening effect. TRIAL REGISTRATION: The peptide-HAP suspension is effective in improving tooth whiteness.

Electrochemical mineralization of iron-tannate stain on HAp and bovine enamel-A non-peroxide approach.

Prolonged treatments for the destaining of teeth using high concentrations of hydrogen peroxide may cause secondary unwanted effects such as tooth hypersensitivity and gingival irritation. Hence, it is aimed to develop a non-peroxide-based method to oxidize iron-tannate (Fe-TA) stained hydroxyapatite (HAp) and bovine enamel (BE) samples. Constant current electrolysis (CCE) experiments were carried out on Pt working electrode in aqueous NaCl, KCl and KI solutions at discrete concentrations under continuous experiment and a non-continuous experiment. CCE shows that in the presence of iron tannate (Fe-TA) stained HAP, approximately 30 ppm of iodine was generated using 0.1M KI and nearly 40 ppm was produced with 0.2 M KI. By using a non-continuous CCE process, the lowest amount of chlorine was generated from NaCl solution, which was well within the safety limits for oral applications. Depending on the experimental conditions used, between 13 ppm and 124 ppm of chlorine was generated. CCE of Fe-TA stained on HAp using KCl reveals that at the lowest current density of 10 mA/cm2, the amount of hypochlorite generated was 20 ppm on Pt electrode having a surface area of 6 cm2. Ion chromatographic (IC) analysis revealed that non-continuous CCE of Fe-TA-BE in NaCl generated a low concentration of sodium perchlorate (0.8 ppm), whereas the continuous process generated no perchlorate, but a considerable higher quantity of chlorate for Fe-TA-BE (37 ppm) and Fe-TA-HAp (140 ppm) samples.

Adhesion and whitening effects of P11-4 self-assembling peptide and HAP suspension on bovine enamel.

OBJECTIVES: This study evaluated the adhesion and whitening effects of a combination of P11-4 self-assembling peptide and hydroxyapatite (peptide-HAP) on bovine enamel. METHODS: Forty-six caries-free bovine teeth were selected, and 40 teeth were randomly allocated to one of five groups (n = 8). First, the effects of application frequency, exposure time, and storage in saliva on the whitening effects of an experimental low-concentrated peptide-HAP suspension (0.5 wt% HAP; Curodont, Credentis) were evaluated and compared with a commercial bleaching agent (VivaStyle Paint on Plus, VS, Ivoclar Vivadent). Tooth color was measured using a spectrophotometer (Gretag MacBeth), and color changes ΔE were statistically analyzed. Second, the effects of peptide-HAP concentration (low versus high: 6.25% HAP; Curodont Protect), and its interactions with saliva and postapplication restaining, were investigated. Third, enamel surfaces (n = 2) were treated with low concentration peptide-HAP and high-concentration peptide-HAP in polymeric and monomeric forms (Curodont Protect & Curodont Repair, Credentis) and analyzed by SEM. RESULTS: The ΔE of the low-concentration peptide-HAP suspension did not differ from that of VS. Application frequency, exposure time, and storage in saliva did not have any significant impact on whitening efficacy of the peptide-HAP suspension. Increasing the concentration of the suspension did not promote overall ΔE. SEM observations confirmed the presence of the newly generated peptide and HAP on the enamel surface. CONCLUSIONS: The peptide-HAP suspension is a mild tooth whitener, and the adhesion of peptide-HAP to enamel is concentration dependent. CLINICAL RELEVANCE: This peptide-HAP suspension is effective in offsetting discoloration caused by restaining after treatment.

Comparison of human and bovine enamel in a microbial caries model at different biofilm maturations.

OBJECTIVES: To compare human versus bovine enamel when used in microbial caries models; and to evaluate the use of nylon mesh to support biofilm growth over enamel. METHODS: Twenty-four sub-subgroups were included (time factor: 4, 8, and 12 days; substrate factor: human/bovine; mesh factor: yes/no; treatment factor: 18.4 mM NaF (350 ppm F), de-ionized water [DIW]; n = 9/sub-subgroup). Microcosm biofilm from human saliva (IRB approval #1,406,440,799) was grown on enamel specimens for 24-h (Brain Heart Infusion media; 0.2 % sucrose), using active attachment model. Then, pH-cycling took place. At the end of each pH-cycling period, enamel specimens were analyzed: surface microhardness (VHNchange); transverse microradiography (integrated mineral loss [ΔZ], lesion depth [L]). Biofilm was analyzed: lactic acid production (LDH activity); exopolysaccharide (EPS) amount; and viability (12-day sub-groups). Data were analyzed using ANOVA at a 5 % level of significance. RESULTS: The three-way interaction between pH-cycling duration, substrate type, and treatment type was significant for (VHNchange [p < 0.0005], ΔZ [p = 0.0027], and L [p < 0.0001]). VHNchange exhibited increased lesion severity as pH-cycling time increases, in both treatments. VHNchange data indicated a treatment effect in all timepoints. ΔZ and L exhibited higher values with more mature biofilms. ANOVA analyses for LDH and EPS indicated a significance between variables (LDH p = 0.0100; EPS p < 0.0001). Mesh-covered specimens resulted in lower LDH and EPS values in all maturations. ANOVA analyses of viability (12 days) between variables was significant. CONCLUSION: within the study's limitations, human or bovine enamel can be used in microbial in vitro caries models to study biofilm's maturation and anticaries agents. CLINICAL SIGNIFICANCE: This study demonstrated how a known cariostatic effect of a fluoride concentration in toothpastes can be modulated by the maturation stage of oral biofilm. This can represent hard to reach areas in the oral cavity (e.g. in orthodontic patients or patients with intermaxillary fixation following oral and maxillofacial surgeries).

Chemical, structural and mechanical characterization of bovine enamel.

OBJECTIVE: The purpose of this investigation was to establish microstructure, microhardness, fracture toughness, chemical composition, and crack repair of bovine enamel and to compare these features with their human counterparts. DESIGN: Bovine enamel fragments were prepared and optical microscopy and atomic force microscopy were used to establish microstructure; Raman spectroscopy was used to estimate composition and microindentation using Vickers testing was performed to evaluate hardness. RESULTS: A strong dependence between indentation load and microhardness values was observed, as was the case in human enamel. Similar microstructure and chemical composition between bovine and human enamel, 7.89% lower microhardness and 40% higher fracture toughness values for bovine enamel were found. CONCLUSION: From a structural and mechanical standpoint, bovine enamel is a suitable alternative to human enamel for in vitro testing of dental products.

Deep sequencing of biofilm microbiomes on dental composite materials.

Background: The microbiome on dental composites has not been studied in detail before. It has not been conclusively clarified whether restorative materials influence the oral microbiome. Methods: We used Illumina Miseq next-generation sequencing of the 16S V1-V2 region to compare the colonisation patterns of bovine enamel (BE) and the composite materials Grandio Flow (GF) and Grandio Blocs (GB) after 48 h in vivo in 14 volunteers. Applying a new method to maintain the oral microbiome ex vivo for 48 h also, we compared the microbiome on GF alone and with the new antimicrobial substance carolacton (GF+C). Results: All in vitro biofilm communities showed a higher diversity and richness than those grown in vivo but the very different atmospheric conditions must be considered. Contrary to expectations, there were only a few significant differences between BE and the composite materials GB and GF either in vivo or in vitro: Oribacterium, Peptostreptococcaceae [XI][G-1] and Streptococcus mutans were more prevalent and Megasphaera, Prevotella oulorum, Veillonella atypica, V. parvula, Gemella morbillorum, and Fusobacterium periodonticum were less prevalent on BE than on composites. In vivo, such preferences were only significant for Granulicatella adiacens (more prevalent on BE) and Fusobacterium nucleatum subsp. animalis (more prevalent on composites). On DNA sequence level, there were no significant differences between the biofilm communities on GF and GF+C. Conclusion: We found that the oral microbiome showed an increased richness when grown on various composites compared to BE in vitro, but otherwise changed only slightly independent of the in vivo or in vitro condition. Our new ex vivo biofilm model might be useful for pre-clinical testing of preventive strategies.

Effect of dentifrice containing fTCP, CPP-ACP and fluoride in the prevention of enamel demineralization.

OBJECTIVE: To evaluate the effect of different fluoride- and calcium- and/or phosphate-containing products on their ability to prevent enamel demineralization under pH cycling conditions. MATERIAL AND METHODS: Enamel bovine specimens were assigned to the following groups: G1-MPP (MI Paste Plus, 0.2% NaF, Recaldent™, GC Corporation Tokyo, Japan); G2-FD (Crest™ Cavity Protection, 0.243% NaF, Procter & Gamble, USA); G3-CLP (Clinpro™ 5000, 1.1% NaF, 3M ESPE, USA); and G4-CO (Control without fluoride, Silica-based dentifrice; Daudt Ltda, Brazil). The specimens were soaked in demineralizing solution for 6 h and remineralizing solution for 18 h alternatively for 10 days. The toothpaste was prepared with deionized water in a 1:3 ratio (w/v) for three minutes daily. The solutions were renewed every 48 h. After cycling, enamel changes were analysed by percentage change of SMH (%SMH) and energy-dispersive X-ray spectroscopy (EDS). The %SMH value observed for G3-CLP (2.9 ± 39.2) was higher than that found in G4-CO (-13.0 ± 20.7), G1-MPP (-8.9 ± 20.9) and G2-FD (-3.9 ± 27.1). The %SMH was similar for all treatment groups (one-way ANOVA and Tukey's HSD; p < .05). The pH, Ca2+ and Ptotal in the remineralization solutions were not different among all groups (Kruskal-Wallis; p < .05). At 24 h, the Ca2+ concentration in the demineralization solution was significantly lower in G1-MPP. Ca2+ concentration increased in all groups after 48 h, except for G3-CLP. The EDX quantitative analysis showed that the atomic % of elements is lower level at G4-CO. CONCLUSIONS: The Clinpro™ 5000 demonstrated having the most protective effect against demineralization; however, the % SMH was similar for all groups.

Shear bond strength of two 2-step etch-and-rinse adhesives when bonding ceramic brackets to bovine enamel.

AIM: The present study assessed a fracture analysis and compared the shear bond strength (SBS) of two 2-step etch-and-rinse (E&R) adhesives when bonding ceramic orthodontic brackets to bovine enamel. MATERIALS AND METHODS: Thirty healthy bovine mandibular incisors were selected and were equally and randomly assigned to 2 experimental groups. Ceramic brackets (FLI Signature Clear®, RMO) were bonded onto bovine enamel using an adhesive system. In group 1 (n=15), the conventional E&R adhesive (OrthoSolo®+Enlight®, Ormco) was used, and in group 2 (n=15), the new E&R adhesive limited to ceramic bracket bonding (FLI ceramic adhesive®: FLI sealant resin®+FLI adhesive paste®, RMO) was used. In order to obtain appropriate enamel surfaces, the vestibular surfaces of mandibular bovine incisors were flat ground. After bonding, all the samples were stored in distilled water at room temperature for 21 days and subsequently tested for SBS, using the Instron® universal testing machine. The Adhesive Remnant Index (ARI) scores were evaluated. Failure modes were assessed using optical microscopy at magnification ×40. A statistic data analysis was performed using the Mann-Whitney U-test (P<0.05). RESULTS: The test showed a significant difference (P=0.00155) between the two groups for the SBS values. Group 1 had significantly higher SBS values (9.79 to 20.83MPa) than group 2 (8.45 to 13.94MPa). Analysis of the ARI scores revealed that most of the failures occurred at the enamel/adhesive interface. A statistically significant difference was found for the ARI scores between the two groups (P=0.00996). Only two fractured brackets, which remained bonded onto the bovine enamel, were reported. Both occurred in group 1. CONCLUSION: When bonded to ceramic brackets, FLI ceramic adhesive® (RMO) was demonstrated to be very predictable and safe for clinical application in enamel bonding, whereas the results obtained with the conventional adhesive system (OrthoSolo®+Enlight®, Ormco) were less reproducible and revealed slightly excessive shear bond strength values.

Influence of irradiation by a novel CO2 9.3-µm short-pulsed laser on sealant bond strength.

The objective of this in vitro study was to evaluate whether irradiation of enamel with a novel CO2 9.3-µm short-pulsed laser using energies that enhance caries resistance influences the shear bond strength of composite resin sealants to the irradiated enamel. Seventy bovine and 240 human enamel samples were irradiated with a 9.3-µm carbon dioxide laser (Solea, Convergent Dental, Inc., Natick, MA) with four different laser energies known to enhance caries resistance or ablate enamel (pulse duration from 3 µs at 1.6 mJ/pulse to 43 µs at 14.9 mJ/pulse with fluences between 3.3 and 30.4 J/cm2, pulse repetition rate between 4.1 and 41.3 Hz, beam diameter of 0.25 mm and 1-mm spiral pattern, and focus distance of 4-15 mm). Irradiation was performed "freehand" or using a computerized, motor-driven stage. Enamel etching was achieved with 37% phosphoric acid (Scotchbond Universal etchant, 3M ESPE, St. Paul, MN). As bonding agent, Adper Single Bond Plus was used followed by placing Z250 Filtek Supreme flowable composite resin (both 3M ESPE). After 24 h water storage, a single-plane shear bond test was performed (UltraTester, Ultradent Products, Inc., South Jordan, UT). All laser-irradiated samples showed equal or higher bond strength than non-laser-treated controls. The highest shear bond strength values were observed with the 3-µs pulse duration/0.25-mm laser pattern (mean ± SD = 31.90 ± 2.50 MPa), representing a significant 27.4% bond strength increase over the controls (25.04 ± 2.80 MPa, P ≤ 0.0001). Two other caries-preventive irradiation (3 µs/1 mm and 7 µs/0.25 mm) and one ablative pattern (23 µs/0.25 mm) achieved significantly increased bond strength compared to the controls. Bovine enamel also showed in all test groups increased shear bond strength over the controls. Computerized motor-driven stage irradiation did not show superior bond strength values over the clinically more relevant freehand irradiation. Enamel that is made caries-resistant with CO2 9.3-µm short-pulsed laser irradiation showed at least equal or significantly higher shear bond strength to pit and fissure sealants than non-laser-irradiated enamel. The risk of a sealant failure due to CO2 9.3-µm short-pulsed laser irradiation appears reduced. If additional laser ablation is required before placing a sealant, the CO2 9.3-µm enamel laser-cut showed equivalent or superior bond strength to a flowable sealant.

Amazonian delicacy tucupi is as erosive as a cola-based soft drink.

OBJECTIVE: Acidic diets are advocated as main risk factor for tooth erosion, which could be prevented, or at least controlled, if patients were early advised. It is important to identify, hence, if possible dietary constituents regionally consumed on large scale, such as tucupi, a low-pH yellowish-green color and strong flavor delicacy made from the juice of a bitter cassava, may explain its occurrence in specific patient groups. This cross-over in situ/ex vivo study evaluated tucupi's ability to promote erosion of bovine enamel by assessing its percentage of surface microhardness change (%SMHC), taking a cola-based soft drink and human saliva as positive and negative controls. DESIGN: For three 7-days spaced out legs of 7 days each, nine volunteers wore palatal devices with three bovine enamel blocks, which were challenged with one of the following solutions: TUC-tucupi (n=27); COL-cola-based soft drink (n=27); SAL-saliva (n=27). Erosive challenges were performed extra-orally (4×/day) by dropping TUC or COL at room temperature on specimens. After 5min, palatal devices were replaced into the mouth. SAL permanently acted as the negative control while volunteers solely wore the device. One-way ANOVA followed by Tukey's post-hoc tests (α=0.05) were applied. RESULTS: TUC promoted an enamel %SMHC (-21.56±10.08(a)) similar than that promoted by COL (-18.19±12.99(a); p=0.275), which were both significantly higher than that promoted by SAL (-1.86±13.65(b); p<0.0001). CONCLUSIONS: Besides the most worldwide appreciated cola-based soft drink, the greatly consumed Amazonian delicacy tucupi can be considered a potential risk factor for tooth erosion.

Fluoride dose-response of human and bovine enamel artificial caries lesions under pH-cycling conditions.

OBJECTIVES: This laboratory study aimed to (a) compare the fluoride dose-response of different caries lesions created in human and bovine enamel (HE/BE) under pH-cycling conditions and (b) investigate the suitability of Knoop and Vickers surface microhardness (K-SMH/V-SMH) in comparison to transverse microradiography (TMR) to investigate lesion de- and remineralization. MATERIALS AND METHODS: Caries lesions were formed using three different protocols (Carbopol, hydroxyethylcellulose-HEC, methylcellulose-MeC) and assigned to 24 groups using V-SMH, based on a 2 (enamel types) × 3 (lesion types) × 4 (fluoride concentrations used during pH-cycling-simulating 0/250/1100/2800 ppm F as sodium fluoride dentifrices) factorial design. Changes in mineral content and structural integrity of lesions were determined before and after pH-cycling. Data were analyzed using three-way ANOVA. RESULTS: BE was more prone to demineralization than HE. Both enamel types showed similar responses to fluoride with BE showing more remineralization (as change in integrated mineral loss and lesion depth reduction), although differences between tissues were already present at lesion baseline. Carbopol and MeC lesions responded well to fluoride, whereas HEC lesions were almost inert. K- and V-SMH correlated well with each other and with the integrated mineral loss data, although better correlations were found for HE than for BE and for MeC than for Carbopol lesions. Hardness data for HEC lesions correlated only with surface zone mineral density data. CONCLUSION: BE is a suitable surrogate for HE under pH-cycling conditions. CLINICAL RELEVANCE: The in vitro modeling of dental caries is complex and requires knowledge of lesion behavior, analytical techniques, and employed hard tissues.

Comparison of Knoop and Vickers surface microhardness and transverse microradiography for the study of early caries lesion formation in human and bovine enamel.

OBJECTIVE: The aims of the present laboratory study were twofold: a) to investigate the suitability of Knoop and Vickers surface microhardness (SMH) in comparison to transverse microradiography (TMR) to investigate early enamel caries lesion formation; b) to compare the kinetics of caries lesion initiation and progression between human and bovine enamel. DESIGN: Specimens (90×bovine and 90×human enamel) were divided into six groups (demineralization times of 8/16/24/32/40/48h) of 15 per enamel type and demineralized using a partially saturated lactic acid solution. SMH was measured before and after demineralization and changes in indentation length (ΔIL) calculated. Lesions were characterized using TMR. Data were analyzed (two-way ANOVA) and Pearson correlation coefficients calculated. RESULTS: ΔIL increased with increasing demineralization times but plateaued after 40h, whereas lesion depth (L) and integrated mineral loss (ΔZ) increased almost linearly throughout. No differences between Knoop and Vickers SMH in their ability to measure enamel demineralization were observed as both correlated strongly. Overall, ΔIL correlated strongly with ΔZ and L but only moderately with the degree of surface zone mineralization, whereas ΔZ and L correlated strongly. Bovine demineralized faster than human enamel (all techniques). CONCLUSIONS: Lesions in bovine formed faster than in human enamel, although the resulting lesions were almost indistinguishable in their mineral distribution characteristics. Early caries lesion demineralization can be sufficiently studied by SMH, but its limitations on the assessment of the mineral status of more demineralized lesions must be considered. Ideally, complementary techniques to assess changes in both physical and chemical lesion characteristics would be employed.

Using bearing area parameters to quantify early erosive tooth surface changes in enamel: a pilot study.

OBJECTIVES: Most in vitro studies investigate the erosive process using relatively simple roughness parameters such as roughness average (Ra). In isolation, Ra may misrepresent the surface features. Further, few studies report baseline surface characteristics after sample preparation. This study aimed to test the hypothesis that measuring the bearing area parameters in addition to Ra may be useful when qualifying the surface of enamel at baseline and after an erosive challenge. The null hypothesis for this study was that the bearing area parameters provide no more useful information than Ra alone, when qualifying the surface of enamel at baseline and after an erosive challenge. METHODS: Enamel slabs (n=20) were prepared from human (n=2) and bovine (n=4) incisor teeth and polished with 0.05µm paste. Roughness average (Ra) and bearing parameters (MR1, MR2, Rpk, Rk, Rvk) were used to record baseline characteristics. Specimens were subjected to erosion with 1% citric acid solution for 1min. Profilometric characteristics were recorded post-erosion, along with the maximum height changes within the profile. T-tests were carried out in order to compare baseline surface characteristics between tissue types. Post-erosion, analysis of variance (ANOVA) was used to test the effects of tissue type (bovine or human). RESULTS: There was no significant difference in Ra between human and bovine incisor enamel at baseline (human 0.11µm, bovine 0.12µm P>0.05), and no significant difference was observed post-erosion (human 0.23µm, bovine 0.20µm P>0.05). There were significant differences in bearing parameters at baseline and post-erosion that were not identified by the Ra measurement alone. CONCLUSIONS: The results suggest that if Ra alone is measured, important differences in surface characteristics may be missed. The null hypothesis is rejected, and the recommendation is made that bearing parameters are included within profile measurements in order to further triangulate the results of surface analysis studies. CLINICAL RELEVANCE: In isolation, Ra may misrepresent the surface features of a profile. These results have shown that the bearing parameters are an important and informative set of measurements. The recommendation is made that bearing parameters are included within profile measurements at baseline and post-erosion, in order to further triangulate the results of surface analysis studies.

Effect of bleaching on sound enamel and with early artificial caries lesions using confocal laser microscopy

The aim of this study was to evaluate effect of bleaching agents on sound enamel (SE) and enamel with early artificial caries lesions (CL) using confocal laser scanning microscopy (CLSM). Eighty blocks (4 x 5 x 5 mm) of bovine enamel were used and half of them were submitted to a pH cycling model to induce CL. Eight experimental groups were obtained from the treatments and mineralization level of the enamel (SE or CL) (n=10). SE groups: G1 - unbleached (control); G2 - 4% hydrogen peroxide (4 HP); G3 - 4 HP containing 0.05% Ca (Ca); G4 - 7.5% hydrogen peroxide (7.5 HP) containing amorphous calcium phosphate (ACP). CL groups: G5 - unbleached; G6 - 4 HP; G7 - 4 HP containing Ca; G8 - 7.5 HP ACP. G2, G3, G6, G7 were treated with the bleaching agents for 8 h/day during 14 days, while G4 and G8 were exposed to the bleaching agents for 30 min twice a day during 14 days. The enamel blocks were stained with 0.1 mM rhodamine B solution and the demineralization was quantified using fluorescence intensity detected by CLSM. Data were analyzed using ANOVA and Fisher’s tests (α=0.05). For the SE groups, the bleaching treatments increased significantly the demineralization area when compared with the unbleached group. In the CL groups, no statistically significant difference was observed (p>0.05).The addition of ACP or Ca in the composition of the whitening products did not overcome the effects caused by bleaching treatments on SE and neither was able to promote remineralization of CL.

O objetivo deste estudo foi avaliar o efeito de agentes clareadores no esmalte sadio (ES) ou esmalte com lesão inicial de cárie artificial (LC), utilizando microscopia confocal laser de varredura (CLSM). Oitenta blocos (4 x 5 x 5 mm) de esmalte bovino foram usados, sendo que 40 destes foram desmineralizados com ciclagem de pH para induzir a LC. Oito grupos experimentais foram obtidos a partir dos tratamentos e condição do esmalte (ES ou LC), com n=10: Grupos ES: G1 - sem tratamento (controle); G2 - peróxido de hidrogênio 4% (PH4); G3: PH4 contendo 0,05% cálcio (Ca); G4 - peróxido de hidrogênio 7,5% (pH 7,5) contendo fosfato de cálcio amorfo (ACP). Grupos LC: G5 - não clareado; G6 - pH 4; G7 - pH 4 Ca; G8 - pH 7,5 ACP. Os grupos G2, G3, G6 e G7 foram tratados com o gel clareador por 8 h/dia durante 14 dias, enquanto as amostras dos grupos G4 e G8 foram submetidas ao agente clareador por 30 min/duas vezes ao dia, durante 14 dias. Os blocos de esmalte foram corados com solução de Rodamina B e a área fluorescente de desmineralização foi quantificada utilizando CLSM. Os dados foram submetidos a ANOVA e teste de Fisher (p<0,05). Para ES, os tratamentos clareadores aumentaram significativamente a área de desmineralização quando comparado com os grupos não clareados, entretanto, para LC não foi observado diferença estatística significante entre os grupos. A adição de ACP e Ca na composição dos géis clareadores não anulou os efeitos dos tratamentos clareadores no ES, assim como não teve capacidade de remineralizar o LC.

Effect of caries infiltration technique and fluoride therapy on the bond strength of the demineralized enamel / Efeito da técnica de infiltração de cárie e fluorterapia na resistência adesiva ao esmalte desmineralizado

Different techniques are employed to control de caries progression, such as fluoride remineralization and resin infiltration (ICON®). However, the interference of these techniques on further adhesive procedures on the treated tissue is still controversial. The aim of this study was to evaluate the bond strength (BS) of the bovine enamel demineralized and treated with either fluoride or ICON®. Material and Methods: The tooth fragments were randomly divided into 4 groups: Group Sound samples (control); Group Demineralized samples (DS); Group Remineralized samples (NaF- 0.05% /8 weeks); Group ICON® samples. The samples were etched and next, a total etch bonding system was applied followed by resin composite. Then, they were submitted to microtensile test in a universal testing machine (10 Kg 1 mm/min). Results: Data were evaluated by ANOVA. There were statistically significant differences among groups (p = 0.28), with the following mean values (MPa): Group: Sound samples ((20,20 ± 2,97), Group: Demineralized Samples (21.99 ± 4.25), Group: Remineralized Samples (23.48 ± 4.03), Group: ICON® samples (22.10 ± 3,37). Conclusion: The treatments did not interfere in bond strength of the composite resin to enamel, providing values similar to those of the control group

Diferentes técnicas são empregadas como forma de controle da progressão da lesão cariosa, como a remineralização com flúor e a infiltração com resina (ICON®). No entanto, a interferência destas técnicas sobre futuros procedimentos adesivos no tecido tratado ainda mostra-se controversa. O objetivo do estudo foi avaliar a resistência adesiva (RA) em esmalte bovino desmineralizado e tratado com flúor ou com ICON®. Materiais e Métodos: Fragmentos dentais foram divididos aleatoriamente em 4 grupos: Grupo Espécimes íntegros (controle); Grupo Espécimes desmineralizados (ED); Grupo Espécimes Remineralizados (NaF- 0,05% /8 semanas); Grupo Espécimes ICON®. Sobre os espécimes tratados foi feito condicionamento ácido, aplicação de adesivo total etch e resina composta, sendo submetidos ao teste de microtração em máquina de ensaio universal (10Kg 1mm/min). Resultados: Os dados foram avaliados pelo teste ANOVA. Não houve diferença significante entre os grupos (p=0,28) sendo que, os valores médios em MPa obtidos para os diferentes grupos foram: Grupo: Espécimes Íntegros (20,20 ± 2,97), Grupo: Espécimes Desmineralizados (21,99 ± 4,25), Grupo: Espécimes Remineralizados (23,48 ± 4,03), Grupo: Espécimes ICON® (22,10 ±3,37). Conclusão: os tratamentos não interferiram na RA da resina composta ao esmalte, fornecendo valores semelhantes ao controle.

Resistência ao cisalhamento de braquetes metálicos utilizando sistema adesivo autocondicionante / Shear bond strength evaluation of metallic brackets using self-etching system

OBJETIVO: avaliar a resistência ao cisalhamento de braquetes metálicos colados com sistema autocondicionante utilizado imediatamente e após 2, 5 e 9 dias depois da ativação e armazenagem. MÉTODOS: utilizaram-se 64 dentes bovinos divididos igualmente em quatro grupos e devidamente preparados para receber a colagem dos braquetes. Em T1, realizou-se a ativação de 7 blisters de adesivos autocondicionantes (de acordo com as normas do fabricante) e procedeu-se à colagem imediata apenas dos braquetes do grupo I. Os adesivos ativados foram, então, armazenados à temperatura de 4ºC e reutilizados em períodos de 2 dias (T2), 5 dias (T3) e 9 dias (T4) para a colagem dos braquetes dos grupos II, III e IV, respectivamente. RESULTADOS: não se observou diferença estatística quando comparados os valores médios de tensão para resistência ao cisalhamento entre os grupos I, II e III. Entretanto, diferença estatística foi encontrada quando esses valores foram comparados aos do grupo IV. CONCLUSÃO: o armazenamento do adesivo autocondicionante depois de ativado, à temperatura média de 4ºC, por até 5 dias, parece não afetar os resultados quanto às tensões de resistência ao cisalhamento; novos estudos são necessários para avaliação das demais características do material quando de sua utilização por período de tempo prolongado após sua ativação.

OBJECTIVE: To evaluate the shear bond strength of metallic brackets using the self-etching system after its activation and storage for 2, 5 and 9 day periods. METHODS: A total of 64 bovine teeth were divided in four groups and prepared to receive the brackets. Initially, seven self-etching primer blisters were activated and used to bond the brackets of group I. The blisters were store at a constant temperature of 4ºC for 2, 5 and 9 days and used to bond the brackets of groups II, III and IV, respectively. RESULTS: No statistic difference was found in shear bond strength comparing groups I, II and III. However, a significant difference was found in group IV. CONCLUSION: The shear bond strength seems not to be affected by activation and storage of the self-etching primer for a 5 day period. More studies are necessary to evaluate other characteristics of the material after its activation and storage for long periods of time.

Effects of different bleaching time intervals on fracture toughness of enamel.

AIM: This study was designed to evaluate the influence of different time intervals of a vital home bleaching procedure on the fracture toughness of bovine enamel. MATERIALS AND METHODS: Labial aspects of 48 bovine incisors were prepared and stored in artificial saliva. The samples were divided into four groups (n = 12) according to the different time intervals of the bleaching procedure: 0, 2, 4, and 6 weeks. The experimental groups were subjected to the bleaching agent; 15% Opalescence PF according to manufacturer's instructions. The fracture toughness (FT) of enamel was assessed using Vickers hardness indentation. Then, FTs were compared statistically by one-way ANOVA (α = 0.05). RESULTS AND DISCUSSION: Different tested time intervals did not significantly influence the fracture toughness of bovine enamel following treatment with 15% carbamide peroxide (P = 0.05) CONCLUSION: 15% Opalescence PF after 6 weeks did not reduce the fracture toughness of human enamel compared with the baseline, 2 and 4-week values.