Bovine Enamel Research Articles

Effects of violet radiation and nonthermal atmospheric plasma on the mineral contents of enamel during in-office dental bleaching.

This in vitro study assessed the effects of in-office bleaching with gels (35% hydrogen peroxide [HP] or 37% cabamide peroxide [CP]) and two activation sources (violet radiation [LED] or nonthermal atmospheric plasma [NTAP]) on the mineral content of bovine enamel. Dental blocks (n = 90) were assessed for initial microhardness before random distribution into nine groups: LED, LED + HP, LED + CP, NTAP, NTAP + HP, NTAP + CP, HP, CP and control (without treatment). Specimens were subjected to bleaching (2 clinical sessions, 7 days apart) using LED [20x/session, 1-min/each, 30 s apart] or NTAP [1x/session, 10 min]. μRaman determined contents of phosphate (PO43) and carbonate (CO32). Micro-energy dispersive X-ray fluorescence (μEDXRF) and spectrophotometry of enamel microbiopsy evaluated the calcium to phosphorous ratios (Ca/P). Two-way ANOVA and Tukey tests analyzed μRAMAN and μEDXRF results. Spectrophotometry results were analyzed using Kruskal-Wallis and Dunn tests. Pearson correlation tested μEDXRF and spectrophotometry results (α = 5%). NTAP and NTAP + HP exhibited greater PO43- content than LED, LED + HP and control (p < 0.05). No statistical differences were detected between CO32- among groups. While μEDXRF evaluation demonstrated that NTAP and LED did not alter Ca/P ratio of enamel (p > 0.05), spectrophotometry showed that Ca/P reduced for LED + HP (p < 0.05). No correlation was found between μEDXRF and enamel microbiopsy spectrophotometry (p > 0.05). Activation sources did not adversely impact enamel's phosphate and carbonate concentrations after specimens' exposure to bleaching gels (either HP or CP). Visible light radiation emitted by a LED source was shown to adversely impact specimens' Ca/P ratios when treated with HP-containing bleaching gels.

Effect of double-layer application on the early enamel bond strength of universal adhesives.

The present study aimed to investigate the changes in the enamel bond strengths of universal adhesives in the early phase of specimen creation and evaluate the effect of double-layer application on enamel bond effectiveness using different etching modes. Four universal adhesives, namely Clearfil Universal Bond Quick, G-Premio Bond, Scotchbond Universal, and Tokuyama Universal Bond, were used. Clearfil SE Bond two-step self-etch adhesive system was used as a comparison. Fifteen specimens per group were used for determining the shear bond strength (SBS) to bovine enamel in the etch-and-rinse or self-etch mode. The adhesive was applied to specimens in accordance with the manufacturers' instructions (single-layer application), or the adhesive was applied twice (double-layer application). The bonded specimens were stored in distilled water at 37°C for 5min or 1, 6, 12, or 24h before SBS testing. The flexural properties of the resin composite Clearfil AP-X were measured for the same storage periods. All universal adhesives exhibited increased SBS values with prolonged storage periods regardless of the application technique or etching mode used. Double-layer application was associated with higher SBS values than single-layer application for most universal adhesives over the same storage period. Phosphoric acid pre-etching and double-layer application of universal adhesives resulted in increased enamel bond strength in the early phase of specimen bonding. Care should be taken when using universal adhesives in the self-etch mode for enamel bonding because the enamel adhesion is sensitive to the duration after filling.

Protective Effects of GIC and S-PRG Filler Restoratives on Demineralization of Bovine Enamel in Lactic Acid Solution

This study was aimed at investigating the protective effects of glass ionomer cement (GIC) and surface pre-reacted glass ionomer (S-PRG) fillers used as dental restorative materials on demineralization of bovine enamel. GlasIonomer FX ULTRA (FXU), Fuji IX GP Extra (FIXE), CAREDYNE RESTORE (CDR) were used as GICs. PRG Barrier Coat (BC) was used as the S-PRG filler. They were incubated in a lactic acid solution (pH = 4.0) for six days at a temperature of 37 °C. The mineral was etched from the enamel surface, and a large number of Ca and P ions were detected in solution. The Al, F, Na, Sr, and Sr ions were released in GICs and S-RPG fillers. The Zn ion was released only in CDR and the B ion was released only in BC. The presence of apparent enamel prism peripheries was observed after six days of treatment for the group containing only enamel blocks. pH values for the FXU, FIXE, CDR, BC, and enamel block groups after six days were 6.5, 6.6, 6.7, 5.9, and 5.1, respectively. Therefore, the observed pH neutralization effect suppressed progression of caries due to the release of several ions from the restoratives.

Anti-caries effect of resin infiltrant modified by quaternary ammonium monomers

ObjectivesResin infiltrant is used in early enamel caries. However, commercial resin infiltrant lacks persistent antibacterial activity. Dimethylaminododecyl methacrylate (DMADDM) was added to resin infiltrant to give it sustainable antibacterial properties and inhibit demineralization. MethodsAfter the application of resin infiltrant to bovine enamel, cytotoxicity, surface roughness, and aesthetics were assessed. A multi-species biofilm was incubated on the enamel disk before and one month after microbial-aging. After a 48-h anaerobic incubation, biomass accumulation, metabolic activity, and lactic acid were analyzed using a crystal violet assay, an MTT (3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and a lactic acid assay. Biofilm structure and composition were determined by live/dead staining, exopolysaccharide (EPS) staining, scanning electron microscopy (SEM), and quantitative polymerase chain reaction (qPCR). The depth and content of demineralization were tested by transverse microradiography (TMR). ResultsIncorporating DMADDM did not increase the cytotoxicity or change the physical properties when the mass fraction of the DMADDM was 2.5–10 %. The modification decreased the amount of bacterial biofilm, metabolic activity, lactic acid production, EPS, and the proportion of Streptococcus mutans in the biofilms. It also provided anti-demineralization effects. The surface roughness and antibacterial ability were not changed after one month of microbial-aging. ConclusionThe incorporation of DMADDM improved the antibacterial and anti-demineralization effects of the material. It demonstrated a sustained antibacterial effect. Clinical significanceThe antibacterial modification might be a potential choice for future clinical applications to inhibit early enamel caries.

Deep Proteomic Insights into the Individual Short-Term Pellicle Formation on Enamel-An In Situ Pilot Study.

Dental pellicle formation starts instantaneously after oral hygiene due to the adsorption of salivary proteins to all orally exposed surfaces. The pellicle acts as a physiological mediator, protects the tooth surface from mechanical damages and reduces acid-induced enamel demineralization. The aim of this pilot study is to identify and characterize individual proteomic profiles of the initial pellicle formed on dental enamel and to compare the profiles with the corresponding saliva to analyze specific adsorption patterns occurring during pellicle formation. The 3-min pellicle of five subjects formed in situ on bovine enamel is eluted chemically and analyzed separately by nano-mass spectrometry. The analysis of the corresponding saliva is conducted in parallel. Up to 498 pellicle proteins and up to 1032 salivary proteins are identified on an individual level. Comparison of the salivary and pellicle protein profiles demonstrates the pellicle formation to be highly individual. Nineteen proteins are significantly enriched in the 3-min pellicle of all subjects and 22 proteins are significantly depleted indicating that pellicle formation relies on selective adsorption. The short-term enamel pellicle is composed of several hundreds of adsorbed salivary proteins and reveals a highly individual proteomic profile.

Randomized in situ trial on the efficacy of Carbopol in enhancing fluoride / stannous anti-erosive properties

ObjectiveTo evaluate if the bioadhesive polymer (Carbopol 980) could potentiate the protective effect of sodium fluoride with stannous chloride (FS) solution on the control of enamel erosive wear. MethodsCylindrical bovine enamel specimens were polished and randomly allocated into three groups (n = 60): FS (500 ppm F- +800 ppm Sn2+ - positive control), FS + Carbopol (0.1% Carbopol), and ultrapure water (negative control). A randomized double-blind cross-over in situ model with three phases was used. In each phase, volunteers (n = 15) used a palatal appliance containing 4 specimens: two were submitted to an erosion model (2 h of pellicle formation; immersion in 1% citric acid, pH 2.3, for 5 min, 4x/day; 1 h intervals of saliva exposure; and treatment with the test solutions for 1 min, 2x/day). Besides erosion, the other two specimens were also subjected to abrasion (2x/day, 15 s) with active electric toothbrush, before the treatment with the solutions. After 5 days, enamel surface loss (μm) was evaluated by profilometry. Data were analyzed by two-way RM-ANOVA and Tukey tests (5%). ResultsThere were significant differences for both challenge and treatment factors. Erosion/abrasion challenge resulted in significantly higher enamel loss than erosion only (p < 0.05). The surface loss values for the erosion/remineralization model were (means ± SL): C = 14.7 ± 5.8b; FS = 9.0 ± 7.5ab; FS + Carbopol = 5.9 ± 3.8a; and for erosion/abrasion: C = 26.6 ± 10.1c; FS = 15.0 ± 8.8b; FS + Carbopol = 12.3 ± 7.9ab. ConclusionThe association of Carbopol to the FS solution significantly protected the enamel against erosive wear, but it was not significantly superior to FS only. Clinical SignificanceUnder highly erosive and abrasive conditions, rinsing with solutions containing sodium fluoride plus stannous chloride, associated or not with the Carbopol polymer, is an effective approach to control enamel erosive wear.

In situ efficacy of an experimental toothpaste on enamel rehardening and prevention of demineralisation: a randomised, controlled trial

BackgroundA novel sodium fluoride toothpaste containing lactate ion and polyvinylmethylether-maleic anhydride has been developed to promote enamel remineralisation and resistance to demineralisation. In this in situ study, we compared this toothpaste (‘Test’) with a stannous fluoride-zinc citrate (SnF2-Zn) toothpaste (‘Reference’) (both 1100–1150 ppm fluoride) and a fluoride-free toothpaste (‘Placebo’) using an enamel dental erosion-rehardening model.MethodsIn each phase of this randomised, investigator-blind, crossover study, participants wore palatal appliances holding bovine enamel specimens with erosive lesions. They brushed their natural teeth with either the Test, Reference or Placebo toothpastes, then swished the resultant slurry. Specimens were removed at 2 h and 4 h post-brushing and exposed to an in vitro acid challenge. Surface microhardness was measured at each stage; enamel fluoride uptake was measured after in situ rehardening. Surface microhardness recovery, relative erosion resistance, enamel fluoride uptake and acid resistance ratio were calculated at both timepoints.ResultsSixty two randomised participants completed the study. Test toothpaste treatment yielded significantly greater surface microhardness recovery, relative erosion resistance and enamel fluoride uptake values than either Reference or Placebo toothpastes after 2 and 4 h. The acid resistance ratio value for Test toothpaste was significantly greater than either of the other treatments after 2 h; after 4 h, it was significantly greater versus Placebo only. No treatment-related adverse events were reported.ConclusionsIn this in situ model, the novel-formulation sodium fluoride toothpaste enhanced enamel rehardening and overall protection against demineralisation compared with a fluoride-free toothpaste and a marketed SnF2-Zn toothpaste.Trial registrationClinicalTrials.gov; NCT03296072; registered September 28, 2017.

Utilization of the extract of Cedrus deodara (Roxb. ex D.Don) G. Don against the biofilm formation and the expression of virulence genes of cariogenic bacterium Streptococcus mutans

Ethnopharmacological relevanceCedrus deodara (Roxb. ex D.Don) G. Don is applied as anti-inflammatory and anti-infection agents in folklore medicine. Aim of the studyThe present study aimed to assess the antimicrobial activity of Cedrus deodara (Roxb. ex D.Don) G. Don extract (CDE) against Streptococcus mutans biofilm formation and its biocompatibility, as well as to identify its chemical components. Materials and methodsConfocal laser scanning microscopy (CLSM), crystal violet staining, and CFU counting assay were applied to investigate the effect of CDE on S. mutans biofilm formation and extracellular polysaccharides (EPS) synthesis. The microstructure of S. mutans biofilms formed on glass coverslips and bovine enamel treated with CDE was observed by scanning electron microscopy (SEM). qRT-PCR was used to measure the expression of virulence genes gtfB, gtfC, and gtfD, and zymogram assay was performed to investigate the enzymatic activity of Gtfs. Moreover, HPLC-MS and NMR were applied to identify its chemical components. CCK-8 assay was also performed on human oral cells to evaluate its biocompatibility. ResultsUnder the treatment of CDE, S. mutans formed less biofilm on both coverslips and enamel surfaces and synthesized less EPS. Moreover, CDE downregulated the expression of gtf genes and inhibited the enzymatic activity of Gtfs. According to HPLC-MS and NMR results, molecular structures of six main compounds in CDE were identified. CDE also has a good biocompatibility. ConclusionsCDE exhibits inhibitory activity against S. mutans and a good biocompatibility. It has the potential to be developed as anti-caries agents for clinical use.

The Effect of a Charcoal-based Powder for Enamel Dental Bleaching.

Charcoal based-powders are not effective for dental bleaching. Charcoal-based dentifrices for dental whitening are a novelty in the market. Manufacturers claim that such charcoal-based products have whitening, remineralization, antimicrobial, and antifungal properties of charcoal in such products. However, there is no substantial scientific evidence for these claims. This laboratory randomized study was designed to evaluate the whitening properties of a charcoal-based toothpowder. A total of 45 bovine dental enamel discs were randomly distributed into three groups (n=15): group 1, mechanical brushing with a 1450-ppm F toothpaste (control group); group 2, mechanical brushing with an activated charcoal-based powder; group 3, bleaching per the standard protocol using 10% carbamide peroxide. The surface roughness and color of each specimen were analyzed at baseline and after 14 days of experiment. The surface of one randomly selected specimen from each group was examined using a scanning electron microscope (SEM). The Kruskal-Wallis test was used to compare groups at a significance level of 5%. Only group 3 promoted a statistically significant effect on ΔE compared with groups 1 and 2 (p<0.001 and p=0.003, respectively). No statistically significant difference was found between groups for surface roughness (p>0.05). SEM revealed a more irregular surface in group 1 specimens compared with group 2 and 3 specimens. The charcoal-based powder did not seem to have any bleaching effect.

Elution of Monomers from an Infiltrant Compared with Different Resin-Based Dental Materials.

Low-molecular weight residuals eluting from dental materials may contribute to local and systemic adverse effects. Therefore, the aim of the present study was to compare triethylene glycol dimethacrylate (TEGDMA)-based commercial infiltrant with different conventional resin-based materials regarding their release of monomers. Cylindrical blocks (n = 10) of either two sealants (Helioseal, Delton FS+), a composite (EcuSphere), an adhesive (Teco) and an infiltrant (Icon) were prepared. Additionally, 20 artificial lesions (depths ≥100 µm) were created in bovine enamel and after etching with phosphoric acid infiltrated with the infiltrant. Except for 10 infiltrated lesions, all other specimens were polished. Each specimen was stored in 1 ml distilled water (elution medium) for 240 h. The medium was renewed in logarithmical divided time periods (4.5 min-76 h). Total concentrations of eluted monomers within 240 h from the cylindrical specimens were 0.04-0.09 mg/ml (p >0.05; Mann-Whitney test). Unpolished infiltrated specimens showed significantly higher monomer concentrations compared to all other groups, whereas polishing of specimens resulted in significantly lower concentrations (p <0.05; Mann-Whitney test). It can be concluded that release of monomers was low in general, but for infiltrated lesions it was considerably reduced by surface polishing reaching similar values as for commonly used monomer-containing dental materials. Thus, adverse effects by the use of an infiltrant are not expected, but polishing of the infiltrated area should be considered.

Effect of High-Fluoride Dentifrice on the Enamel Demineralization Related in Concern to Microhardness

Objetivo: Avaliar a efetividade do dentifrício de alta concentração de F na diminuição do processo de desmineralização do esmalte. Material e Métodos: Foram confeccionadas trinta amostras de esmalte bovino, as quais foram lixadas, polidas e obtida a microdureza (Knoop) inicial. As amostras foram distribuídas aleatoriamente em três grupos (G): DP - dentifrício sem F (placebo), DC - dentifrício convencional (1450 ppmF) e DAC - dentifrício de alta concentração (5000 ppmF). Para avaliar o processo dinâmico de desmineralização, cada grupo foi submetido a uma ciclagem de pH com solução desmineralizante e solução remineralizante. As amostras foram imersas durante 6 e 18h nas respectivamente soluções, durante cinco dias, a 37oC. O dentifrício correspondente a cada grupo foi diluído (1:3) e as amostras foram tratadas por 1 minuto, duas vezes ao dia. Após a ciclagem, foi realizada a análise da microdureza final e aplicado ANOVA e Tukey (p&lt;0,05). Resultados: Os resultados mostraram que a microdureza final do DAC (247,4?39,4) comparada ao DC (211,9?53,5) mostrou diferença estatística (p?0,05). Conclusão: De acordo com os resultados, pode-se sugerir que o dentifrício de alta concentração de Flúor apresenta resultados superiores na inibição do processo de desmineralização do esmalte quando comparado ao dentifrício convencional

Tribocorrosion of dental tissues: The role of mucin

Artificial saliva can benefit tooth degradation management; this study assesses the role of mucins in this process using a combination of techniques to assess wear and surface degradation. Different neutral and acidic artificial saliva solutions were investigated, focusing on the protective capability of mucins. Static immersion and reciprocating ball-on-flat tribometer tests were performed on bovine enamel samples. The calcium released into the test solutions were assessed using Atomic Absorption Spectrophotometry (AAS) and enamel surfaces were examined using Vertical Scanning Interferometry (VSI). The addition of mucins reduced the coefficient of friction and wear scar volumes for neutral pH solutions. In acidic conditions the addition of mucin did not affect the lubrication, however it significantly reduced the calcium release under tribological conditions.

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

ObjectivesTo 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. MethodsTwenty-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. ResultsThe 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. Conclusionwithin 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).

Color evaluation of white spot lesions treated with resin infiltration after water or grape juice storage

Aim: To evaluate the color stability of bovine enamel with artificial white spot lesions treated with resin infiltration (ICON) or remineralization with fluoride using two storage methods. Methods: Sixty incisors were submitted to artificial white spot lesion induced by demineralization-remineralization (DE-RE) cycling. Initial color was evaluated with CIE-Lab to measure ΔEab. Demineralized teeth were divided according to the treatment of the white spot lesion (n = 20): 1) Remineralization with 2% neutral fluoride gel for 4min (control); 2) ICON application following manufacturer’s recommendations; and 3) ICON with decreased drying time after the application of ethanol. After 24h, color was evaluated and samples were subdivided (n = 10) according to storage: 1) distilled water for 1 month; 2) grape juice for 10min daily. After storage, color was evaluated. L*, a* and b* data were analyzed by one-way ANOVA and ∆Eab data by two-way ANOVA followed by Tukey’s HSD (α = 0.05). Results: L* was affected by juice storage, and decreased when ICON was applied with decreased drying time after the ethanol application. The same behavior occurred with a* (increase with reduced drying time), while b* was not affected. For ∆Eab significant differences were observed between groups (p = 0.0219) and storage methods (p = 0.0007). There was no interaction effect (p = 0.1118). Remineralization with fluoride presented the lowest color changes after storage in water. Conclusion: Treatment of artificial carious lesions with resin infiltration presented greater color changes than fluoride remineralization after storage in both solutions in vitro.

Chlorhexidine rinsing inhibits biofilm formation and causes biofilm disruption on dental enamel in situ.

This in situ study aims to evaluate the effects of chlorhexidine (CHX) mouth rinsing on biofilm formation and moreover on the disruption of existing mature dental biofilms. Biofilms were formed in situ by five volunteers on bovine enamel specimens fixed to individual acrylic splints. For biofilm formation analysis, the volunteers intraorally exposed the splint for 48h. Mouth rinsing using 10ml of 0.2% CHX or water as control was performed for 30s every 12h. For analysis of biofilm disruption, the biofilm was formed on enamel specimens for 48h. Then, the first CHX rinse was carried out. A second rinse followed after an additional 12h, again for 30s using 10ml of 0.2% CHX. Biofilm vitality was imaged by fluorescence microscopy after vital fluorescence staining. Additionally, the ultrastructure of the biofilm was examined by transmission electron microscopy. Rinses with 0.2% CHX significantly reduced biofilm formation on enamel. Both biofilm colonization and vitality were dramatically impaired. Moreover, a considerable biofilm disruption induced by the CHX rinses was observed. Remarkably, a single application of CHX to a 48-h mature biofilm causes biofilm ultrastructure alterations and induces a substantial reduction in biofilm thickness and bacterial vitality. CHX mouth rinses induced a significant inhibition of biofilm formation on native enamel. Furthermore, an important biofilm disrupting effect under in situ conditions was detected. CHX rinses could be used as a short-term treatment protocol for biofilm management focused on patients unable to reach adequate oral hygiene.

Re- and demineralization characteristics of dentin depending on fluoride application and baseline characteristics in situ

ObjectivesThe aim of this double-blinded, randomized, cross-over in situ study was to evaluate the re- and demineralization characteristics of sound dentin as well as highly and lowly demineralized dentin after the application of different fluoride concentrations. MethodsIn each of four experimental legs of four weeks 20 participants wore intraoral mandibular appliances containing two (highly demineralized [EH]) bovine enamel and four (lowly and highly demineralized [DL,DH]) bovine dentin specimens (n = 480). Each specimen included one sound (ST) and one demineralized lesion area (DT). The four randomly allocated treatments included the following dentifrices: fluoride-free, zinc-carbonate-nano-hydroxyapatite [nHA0], 0 ppm F− [negative control,NaF0], 1100 ppm F− as NaF [standard therapy,NaF1100] and 5000 ppm F− as NaF [positive control,NaF5000]. Differences in integrated mineral loss (ΔΔZ) and lesion depth (ΔLD) were calculated between values before and after the in situ period using transversal microradiography. ResultsAfter the in situ period specimens of nHA0 and NaF0 showed signs of demineralization, indicated by significantly lower ΔZ&LD values for EH and DL (only nHA0)(p ≤ 0.028), whereas specimens of NaF1100 and NaF5000 showed signs of remineralization, indicated by significantly higher ΔZ values for EH (only NaF5000), DL and DH (p ≤ 0.012). The correlation between ΔΔZDT/ΔΔZST and F− was moderate for EH(rDT = 0.497;rST = 0.463) and DL(rDT = 0.575;rST = 0.598) and strong for DH(rDH = 0.700;rST = 0.611)(p < 0.001). No significant differences for ΔΔZDT/ΔΔZST were observed between nHA0 and NaF0(p ≥ 0.333;ANCOVA). ConclusionThe present in situ model was capable to reveal a fluoride dose-response on sound, lowly and highly demineralized dentin and also enamel specimens. Furthermore, both fluoride-free dentifrices, one containing nanohydroxyapatite, did not hamper demineralization. Clinical SignificanceThe present in situ model was capable to reveal a fluoride dose-response on dentin similar to the anticipated clinical efficacy. Highly demineralized specimens seem to be recommendable for measuring anti-caries effects on dentin in situ. Furthermore both fluoride-free dentifrices, one containing nanohydroxyapatite, did not hamper demineralization.The study was registered in the German Clinical Trials Register (DRKS-ID: DRKS00011653).

Probing Heterogeneity in Bovine Enamel Composition through Nanoscale Chemical Imaging using Atom Probe Tomography

ObjectiveThe aim of this study was to determine the heterogeneity in chemical composition of bovine enamel using atom probe tomography, and thereby evaluate the suitability of bovine enamel as a substitute for human enamel in in vitro dental research. DesignEnamel samples from extracted bovine incisor teeth were first sectioned using a diamond saw and then milled into needle-like samples (<100 nm diameter) by focused ion beam (FIB) coupled with a scanning electron microscope (SEM). These samples were analyzed in the atom probe to acquire three-dimensional (3D) images and quantify the atomic chemistry and distribution in bovine enamel. ResultsFor the first time, the atomic-level composition and clustering of major constituents and impurities within bovine enamel were determined and imaged. We discovered that the chemical composition of bovine enamel is spatially inhomogeneous at the atomic scale. The average bulk Ca/P ratio, ∼1.4, was in agreement with previously reported literature values from alternative conventional methods. When assessed locally at the atomic scale, the Ca/P ratio varied between 1.1 and 2.03. We also discovered that the Mg impurities were significantly segregated throughout the enamel, and such clustering influenced the variation of Ca/P ratios. The increase in Mg concentrations, near the Mg clusters, correlated with increased Ca and decreased P concentrations. ConclusionThe presented findings of variability in local composition should be taken into account when interpreting dental research results from bovine enamel.

The effect of shape and size distribution of abrasive particles on the volume loss of enamel using micro-abrasion

Wear of enamel during tooth brushing is a complex phenomenon with many variables affecting the level of loss. Toothpastes contain angular abrasive particles at a concentration of 12%–15% v/v abrasive designed to remove biofilm and extrinsic stains that also have the potential to harm the tooth enamel resulting in wear. Toothpastes contain multi-modal particles in the size range of 4μm–12μm. The aim of this paper is to develop an understanding of the relationship between the combined effects of particle shape, size, size distribution and load on the volume loss of enamel under abrasive testing. Micro-abrasion testing using a Nylon ball, to simulate the toothbrush, was undertaken on hydrated bovine enamel disks using volume concentrations of 5% – 20% v/v alumina and silica. Post experimental surface analysis was performed to analyse the wear scar morphology and groove analysis. The synergistic effects were calculated of bimodal particles vs. mono sized particles. Mono-sized particles as compared to bimodal, appeared to give the best outcome and least wear of enamel. A positive synergy existed for the alumina and silica bimodal tests, indicating the bimodal particle distribution was causing more wear than the mono-sized particles. The mechanism of material removal was a combination of crushing and fracture of the enamel prisms (rods), followed by micro-chipping and removal of enamel. The magnitude and the distribution of the particle sizes is the most dominant factor in determining the levels of wear, with smaller particles and narrow distributions of the particle size reducing the magnitude of wear. The shape of the particles is also a major factor influencing wear, with the spherical tests generating lower wear rates than the angular tests.

Effects of 1450-ppm Fluoride-containing Toothpastes Associated with Boosters on the Enamel Remineralization and Surface Roughness after Cariogenic Challenge.

Objectives This in vitro study investigated the remineralization potential of 1450 ppm, fluoride-containing toothpastes containing different active remineralization agents after cariogenic challenge with pH cycling. The enamel surface roughness after brushing and the chemical and physical characteristics of the toothpastes tested were also analyzed. Materials and Methods Fifty-six bovine enamel blocks were obtained (4 × 4 × 6 mm) and divided into three thirds: intact (untreated), demineralized (artificial caries lesion), and treated (caries lesion, pH cycling, and brushing with dentifrices). Seven commercially available fluoride toothpastes (1450 ppm F): three with anti-erosion claims (Candida Professional [CPP], Colgate Total 12 Daily Repair [CDR], Regenerate Enamel Science [RES]); three with desensitizing claims (Bianco Pro Clinical [BPP], Elmex Sensitive [ESS], and Regenerador Diário DentalClean [RDC]); and one standard regular-fluoride toothpaste Colgate Total 12 (CTT) were selected. During pH cycling (demineralization 6 h/remineralization 18 h) for 7 days, the treated third was brushed with the different dentifrices for 10 minutes in a brushing machine before immersion in a remineralizing solution. The Knoop hardness (25 g, 10 second of the surface, and longitudinal section were then evaluated at eight depths (10 to 330 μm). Mean and percentage of surface hardness recovery (% SHR) were calculated. Surface enamel roughness (Ra) was also evaluated. The pH, %weight of particles, zeta potential, and polydispersity index of toothpaste slurries were also evaluated. Statistical Analysis Data were statistically analyzed (ANOVA/Tukey, 5%). Results The %SHR of CPP was significantly lower than the others ( p < 0.05). The enamel subsurface was more effectively remineralized when treated with BPP, ESS, and RDC. The surface roughness was higher when the demineralized third was treated with CTT, RDC, and RES and after the cariogenic challenge ( p < 0.05). For some of the products tested, there was no relationship between surface remineralization and subsurface remineralization. Although toothpastes CPP and RDC present the lowest %SHR means, both products effectively remineralize within the subsurface carious lesion. Regression analysis demonstrated no strong correlations of the enamel surface roughness with the chemical and physical parameters. Conclusions Most but not all the fluoride toothpastes were able to remineralize the enamel surface. No specific chemical or physical parameter alone correlated with the surface roughness.

Therapeutic Potential of Bauhinia forficata Link in Dental Biofilm Treatment.

The oral cytotoxicity, antimicrobial and anti-demineralizing effects of a tincture from Bauhinia forficata Link tincture (BFLT) were evaluated in vitro and ex vivo. Susceptibility tests (minimum inhibitory and microbicidal concentrations-MIC and time-kill assay-MMC) were performed against planktonic oral microorganisms. The contents of phenolic compounds were investigated. Cytotoxic potential was evaluated on oral fibroblasts after 1-5 min exposure to BFLT. Blocks of sound bovine enamel (N = 60) were inoculated with a saliva pool and sustained in a multiple plaque growth system for 48 h to form a biofilm. Biofilm blocks were randomly divided into groups-G (n = 10): G1-Baseline (48 h maturation biofilm), G2-BFLT 23.2 mg/mL, G3-Ethanol 81.20 g/mL, G4-Chlorhexidine 0.12%, G5-Growth control, and G6-Blank control. Treatments (50 μL/1 min) were performed once a day for a week. Streptococcus spp. (S) and total microorganism (TM) counts were expressed as Log10 CFU/mL. Biofilm height was evaluated by confocal microscopy analyses (CMA). Final surface hardness was assessed and percentage of microhardness loss (% MHL) was calculated. Results were significant when P < .05. BFLT inhibited all tested microorganisms (MIC = 1.3-23.2 mg/mL) and promoted optical reduction (0.05-0.22 nm) of all microorganisms after 48-h treatment compared with controls. After 5-min treatment, BFLT showed low values of cell death (3.20%). G2-BFLT reduced S (6.61 ± 0.20) and TM (7.14 ± 0.38) compared with G1-Baseline (S = 7.82 ± 0.28; TM = 8.81 ± 0.67) and G5-Growth control (S = 7.48 ± 0.39; TM = 7.89 ± 0.68); but G4-chlororexidine (S = 6.11 ± 0.48; TM = 6.45 ± 0.16) showed the highest antibiofilm activity. CMA was not different among treatment groups. G2 showed lower % MHL compared with G5, although G4 presented the lowest. Results suggest BFLT is beneficial against dental caries, showing antimicrobial effects against a mature dental biofilm and no cytotoxicity.