Bovine Enamel Research Articles

Enamel Demineralization and Remineralization Detection Using Non-invasive Optical Imaging

Introduction: Optical Coherence Tomography (OCT), is one of the most emerging diagnostic imaging technique. It is capable of producing 3D images using optical scattering media. The fast signal acquisition quality has made it a promising tool to detect early in vivo and in vitro lesions. The aim of this study was to reproduce previous demineralization results and to detect remineralization using OCT. Methodology: Bovine enamel discs were used thoroughly in this study. The study was done using the flow cell for detecting demineralization and remineralization following 96 hours demineralization and 192 hours remineralization. A time lapse monitoring was done and the lesions were assessed visually. ImageJ software was used to process the images produced through OCT. The lesion depth and intensity was measured across the images produced which helped in assessing the difference between remineralization and demineralization. Results: OCT B-scan images result in increased backscattering light which is considered the main principle to measure lesion depth and mineral loss. Whereas, in remineralization decreased band of light appeared with reduction in porosity during mineral precipitation. The results for remineralization were diverse and could not be assessed. Conclusion: OCT is favorable technique to detect demineralization and remineralization but it still needs a lot of improvement especially regarding remineralization there are limitations which need to be improved.

Wear of conventional and pre-polymerized composite materials under erosive/abrasive conditions.

The aim of this study was to examine the wear of three different composite materials usable for vertical bite reconstruction under erosive/abrasive conditions and to compare them with the bovine dental hard tissues enamel and dentin in-vitro. The composite materials Filtek Supreme XTE, CeraSmart and Brilliant Crios and bovine enamel and dentin specimens were evenly allocated to five groups (n=10). Samples were firstly exposed to hydrochloric acid for 1 min, then stored for 30 min in artificial saliva. In the second step, the samples were brushed for 1 min with 100 brushing strokes each and an applied force of 2.5 N in an automated brushing device. After 60 of these erosive/abrasive cycles, wear of the samples was determined by contact profilometry. Filtek Supreme XTE showed significantly less wear (mean ± standard deviation; 0.15 ± 0.11 μm) compared to the other two composite materials (p < 0.05). No significant difference (p > 0.05) could be found between CeraSmart (0.25 ± 0.03 μm) and Brilliant Crios (0.24 ± 0.04 μm). The two bovine dental hard tissues, enamel (13.70 ± 0.94 μm) and dentin (50.08 ± 4.46 μm), each showed a significantly higher amount of wear than the three restorative materials (p <0.05). In conclusion, this study exhibited that the three composite materials, Filtek Supreme XTE, CeraSmart and Brilliant Crios, were more resistant under erosive/abrasive conditions compared to bovine enamel and bovine dentin, respectively.

The influence of the CIELAB parameters on the perception of color after the use of whitening toothpastes

Aim: To evaluate the influence of the parameters L* a* b* on the variation of the color of bovine tooth enamel submitted to artificial darkening, after simulated brushing, with whitening toothpastes containing blue covarine. Methods: To undertake this study in vitro, 60 specimens (SP) were divided into 6 groups (n=10): control group (CGwater) and 5 test groups (GT1-Colgate Total 12, GT2-Oral-B 3D White Perfection, GT3- Colgate Luminous Instant White, GT4-CloseUp White Diamond Attraction, GT5-Sorriso Xtreme White). The specimens were darkened with coffee and submitted to simulated brushing for 6, 12, and 24 months. The alteration in the color was evaluated using CIELAB parameters and the ΔL, Δa, Δb and ΔE were calculated. The data was analyzed through generalized linear models using the R program and considering a level of significance of 5%. Results: The parameters L*, a* and the ΔL, Δa obtained better results in the test group than in the control group. There were no statistical differences between CG and the test groups for the evaluation of the b* parameter. In the evaluation of the Δb, the GT3 differed statistically from the CG. In relation to the ΔE, all the group tests showed a variation in color statistically greater than that of the CG and the GT4 showed the greatest variation, not differing from the GT3 during the periods studied. Conclusion: The mechanical and optical whitening agents positively influenced the values L*a* and b*, as well as in its variations and in the ΔE. It is important to emphasize, however, that to analyze tooth whitening it is necessary to evaluate their parameters together.

Which Polishing Method Is Effective for Coffee Stains? – An In-Vitro Study of Surface Roughness and Color Change

Aim: To assess the effect of three different polishing protocols on the surface roughness and color change of the enamel and compare the results with the enamel specimens exposed to coffee. &#x0D; Methods: Seventy-two bovine enamel specimens were randomly divided into two groups-Group I:only polishing,Group II:immersion in coffee solution and polishing–which were then subdivided into 3 groups according to polishing procedures as follows:polishing with rubber cup and Pumice Flour(PF),polishing with rubber cup and Prophy Paste(PP),polishing with Air Abrasion(AA). Surface roughness(Ra) and tooth color were assessed using a surface profilometer and a digital spectrophotometer. The color change was determined by the CIE L*a*b* system. SEM analysis were also performed. Statistical analyses were performed by GraphPad software. Multiple comparisons between-groups and in-groups were performed using Kruskal-Wallis and Friedman tests, respectively.&#x0D; Results: At baseline measurements, no significant differences were found among groups in terms of roughness and color values(p&gt;0.05). In Group I,surface roughness values and color change were similar after polishing (p:0.393,p:0.093, respectively). In Group II,post-polishing Ra values were significantly increased in all groups(p0.05) and the highest ΔE value was detected in PP group. &#x0D; Conclusion: Following coffee immersion, enamel surfaces become rougher in all polishing protocols and the roughest surface was in PF group. In all study groups visible clinical success was achieved in terms of color, therefore dental clinicians should prefer PP in clinical practice due to the less abrasive and sufficient color change properties.

Bioadhesive Curcumin-Mediated Photodynamic Inactivation and Its Potential to Cause Undesirable Effects on Dental and Restorative Surfaces.

Curcumin-mediated Photodynamic Inactivation (PDI) has shown great potential to disinfect specific sites on tooth enamel but may involve contact with restorative materials. Thus, before use in dentistry, it is necessary to investigate whether the PDI protocol causes undesirable changes in the surfaces of aesthetic restorative materials and dental enamel. This study investigated the effect of PDI mediated by curcumin (CUR) in a liquid crystal precursor system on color stability (ΔE), surface roughness (Ra), and microhardness (kgf) of three different composite resins and bovine dental enamel specimens. The microhardness and roughness readings were performed 60 days after the treatments while the color readings were performed immediately, 24, 48, and 72 h, 7, 14, 21, 30, and 60 days after the treatments. Results showed that CUR mediated-PDI does not seem to have the potential to promote any esthetic or mechanical changes to the surface of tooth enamel and can be applied safely in clinical practice. However, the results on color, roughness, and hardness obtained for composite resins show that some negative effects can be produced, depending on the type of restorative material; more experiments must be performed with different formulations and, perhaps, with lower concentrations of CUR.

Surface Free Energy, Interaction, and Adsorption of Calcium and Phosphate to Enamel Treated with Trimetaphosphate and Glycerophosphate

This study aimed to evaluate the surface (γs) and interaction (ΔGiwi) free energy and calcium (Ca2+) and phosphate (PO43−) adsorption to dental enamel treated with sodium trimetaphosphate (TMP) or calcium glycerophosphate (CaGP) that had or had not been exposed to CaPO4-containing solutions. Bovine enamel blocks (n = 192; 24 blocks/group) were treated (2 mL/block; 2 min) with TMP (0%, 1%, 3%, and 9%) and CaGP (0, 0.25, 0.5, and 1%) or exposed to a CaPO4-containing solution. The adsorption of these compounds by enamel was assessed before and after treatment. γs and ΔGiwi and their apolar (γsLW and ΔGiwiLW) and polar (γsAB and ΔGiwiAB) components and acid-base interactions (γs+/γs−) were determined by the contact angles. The data were subjected to ANOVA, followed by the Student-Newman-Keuls test (p < 0.05). The adsorption of TMP was dose dependent (p < 0.001), and it reduced γs and γsAB and increased ΔGiwiAB (ΔGiwi > 0) and γs− when compared with the group without TMP (p < 0.001). The immersion in CaPO4-containing solution increased γs and γsAB and reduced ΔGiwiAB (ΔGiwi > 0) and γs− (p < 0.001). There was a correlation between the adsorption of TMP and Ca2+ (r = 0.916; p < 0.001) and PO43− (r = 0.899; p < 0.001). The adsorption of CaGP on the enamel was dose dependent (p < 0.001), reducing γs, ΔGiwiAB (ΔGiwi < 0), γsLW, and γs− when compared to the group without CaGP (p < 0.001). When exposed to the CaPO4-containing solution, there was an increase in ΔGiwiAB (ΔGiwi > 0), γsLW, and γs− and a decrease in γsAB (p < 0.001) without adsorption of Ca2+ by enamel. It may be concluded that TMP and CaGP were adsorbed onto the enamel, producing hydrophilic and hydrophobic surfaces, respectively. TMP produces electron donor sites that induce Ca2+ adsorption, while CaGP releases Ca2+ into the medium.

Influence of Pre-Etched Area and Functional Monomers on the Enamel Bond Strength of Orthodontic Adhesive Pastes

This study was performed to investigate the influence of pre-etching area and functional monomers in orthodontic adhesive pastes on enamel bond strength. Bovine enamel was partially pre-etched with phosphoric acid for 30 s over areas with a diameter of 1.0, 2.0 or 3.0 mm, and metal brackets were then bonded with or without functional monomers in the orthodontic adhesive paste. For the baseline groups, the whole adherent area was pre-etched. The shear bond strength (SBS) and adhesive remnant index (ARI) were determined. The adhesive paste/enamel interfaces were observed by scanning electron microscopy (SEM). Although the adhesive paste with functional monomers showed higher SBS than the functional monomer-free adhesive paste in all groups, there were no significant differences in SBS between them regardless of the pre-etched area. The SBS increased with increasing pre-etched area in both orthodontic adhesive pastes. In SEM images of adhesive paste/enamel interfaces, although adhesive with functional monomers showed excellent adaptation, the functional monomer-free adhesive paste showed gap formation at the interface. These findings suggested that the pre-etching area greatly influenced bond strength, regardless of the presence or absence of the functional monomer in the orthodontic adhesive paste.

LED/laser photoactivation enhances the whitening efficacy of low concentration hydrogen peroxide without microstructural enamel changes

Background: The association of low concentration hydrogen peroxide (HP) and a light source has been widely used to achieve efficient bleaching. We investigated the colorimetric and microstructural changes of bovine enamel bleached with 6% HP associated or not with a hybrid light source system of violet light and laser (LED/laser). Methods: Twenty bovine crowns were used to obtain specimens of 7 × 7 × 2 mm. Then, they were randomized in two groups (n=10): 6% HP and 6% HP + LED/laser. After staining with dark tea solution, three bleaching sessions were performed. Colorimetric evaluation (∆L*, ∆a*, ∆b*, ∆E00 [CIEDE2000] and WID) after 24 hours of each session and 7 days after the final bleaching session was performed. Enamel Vickers microhardness at baseline, 24 hours and 7 days after the last bleaching session were also evaluated. Two-way repeated measures ANOVA and Bonferroni post-test was used at a significance level of 5%. Results: 6% HP and 6% + HP LED/laser showed satisfactory bleaching results. The group photoactivated showed higher WID values (p<0.05). Differences between groups were observed for ∆E00, ∆L* and ∆a* (p<0.05), except for ∆b* (p>0.05). Intra-group differences were also found (p<0.05). Regarding microhardness, no inter or intra-group differences were observed (p>0.05). Conclusions: The photoactivation with LED/laser enhanced the whitening efficacy of 6% HP compared to the group without photoactivation. Thus, the LED/laser activation appears to be a good option when using low concentration HP-based agents. In addition, both bleaching protocols did not cause changes on enamel microhardness.

Effect of blue light plus chlorhexidine therapy on Streptococcus mutans biofilm and its regrowth in an in vitro orthodontic model

Fixed orthodontic appliances create areas of stagnation for dental biofilms and make it difficult to clean the teeth; therefore, there is a risk of developing incipient caries lesions during the orthodontic treatment. The objective of this study is to determine if the combination of 2 different therapies, phototherapy by blue light (BL) and the antimicrobial 0.12% chlorhexidine (CHX) on enamel, orthodontic brackets, and elastics, would reduce or inhibit mature Streptococcus mutans biofilms and their regrowth on these substrates 24hours after the application of the treatment; and if this treatment would interfere with bracket adhesion to the enamel. Biofilms of S. mutans UA159 were formed for 5-days over samples composed of a bovine enamel, orthodontic bracket, and orthodontic elastic. Then, the specimens were treated with 0.89% NaCl for 1minute, BL for 12minutes (72J/cm2), 0.12% CHX for 1minute, and BL for 12minutes, followed by 0.12% CHX for 1minute (BL+CHX). Biofilm was evaluated by colonies forming units and dry weight immediately after treatments and 24hours after treatments (regrowth). The pH of the spent media was measured on the fifth and sixth days. Biofilm formation on the samples after the treatments and regrowth was visually evaluated by confocal laser scanning microscopy. Shear bond strength (SBS) between bracket and enamel was evaluated using a universal testing machine at a crosshead speed of 1mm/min. After bonding, specimens were thermocycled (500× at 5-55°C), treated, and thermocycled again. After 5days of biofilm formation, BL+CHX significantly reduced the bacterial viability on enamel compared with NaCl (P=0.004) and BL (P=0.014). For bracket and elastic, all the treatments resulted in similar bacterial viability (P ≥0.081). In the regrowth, CHX and BL+CHX significantly reduced the bacterial viability in the enamel compared with the NaCl (P≤0.015) and BL (P≤0.013). For bracket, BL+CHX significantly reduced the bacterial viability compared with NaCl (P=0.008) and BL (P=0.009). For the elastic, BL+CHX eliminated the biofilms from the substrate. CHX and BL+CHX significantly reduced the bacterial viability 24hours after treatment for all substrates (P≤0.05). The media pH significantly increased when samples were treated with CHX and BL+CHX (P≤0.001). Confocal laser scanning microscopy images visually showed an abundant quantity of red cells in the samples treated with BL+CHX. There was no difference in the SBS between the treatments (P ≥0.932). The association between BL and CHX reduced S. mutans biofilm and its regrowth on an invitro orthodontic model and did not influence the bonding strength between bracket and enamel.

An In Vitro Assessment of the Acid Resistance Characteristics of Nanohydroxyapatite/Silica Biocomposite Synthesized Using Mechanochemistry

This paper reports on the in vitro assessment of the acid resistance characteristics of mesoporous silica/nanohydroxyapatite (MSN@nHAp) biocomposite synthesized through the mechanochemical method. Bovine enamel models were used to study the acid resistance characteristics of the composite (n=5). X-ray diffraction and Fourier transform infrared spectroscopy were used to characterize the surface morphology of the MSN@nHAp. The XRD and FTIR results confirmed the successful syntheses and surface modification of nanohydroxyapatite with silica. The MSN@nHAp exhibits superior acid resistance characteristics. The salient aspect of this study suggests that mechanochemistry is a useful technique in the synthesis and surface modification of valuable biomaterials. The study concludes that the MSN@nHAp composite could be utilised in toothpaste formulation for oral healthcare management due to its acid resistance properties.

Effect of Adhesive Application Method on the Enamel Bond Durability of a Two-Step Adhesive System Utilizing a Universal Adhesive-Derived Primer

This study aimed to evaluate the effect of the adhesive application method on the durability of the enamel bond and the thickness of the adhesive layer. A new-generation two-step universal adhesive system, G2-Bond Universal, and two conventional two-step adhesive systems were utilized. The shear bond strength to bovine enamel was measured after thermal cycling in both etch-and-rinse and self-etch modes. Fifteen specimens were divided into three groups as follows: Group I, wherein a strong air stream was applied over the bonding agent for 5 s; Group II, wherein a gentle air stream was applied over the bonding agent for 5 s; and Group III, which was prepared as in Group II, followed by the application of a second layer of the bonding agent and a gentle air stream for 5 s. The durability of the enamel bond and thickness of the tested adhesives were influenced by the application method in both etching modes. The application method used in Group II appeared to be most suitable in terms of the bonding of the adhesives to the enamel. The new-generation two-step self-etch adhesive, comprising a universal adhesive-derived primer and a hydrophobic bonding agent, showed superior bond performance to the conventional two-step adhesive systems.

Effects of occlusal splint therapy on opposing tooth tissues, filling materials and restorations.

BackgroundLittle is known about the effect of the type of splint material, heat‐cured PMMA (HC) or chemical‐cured PMMA (CC) on the wear of opposing tooth surfaces.ObjectiveThe aim of this in vitro study was to evaluate two‐body wear of dentin, enamel, glass‐ceramic or one of four resin composites when opposing splint materials, namely ProBase HC and CC.MethodsThe two‐body wear of bovine dentine, bovine enamel, glass‐ceramic IPS e.max CAD (EMAX) and four composites (Filtek Z250 [Z250], Clearfil AP‐X [AP‐X], Clearfil Majesty Posterior [CMP], Filtek Supreme XTE [FSE]) opposing three antagonists (HC and CC and stainless steel as control) were evaluated in the ACTA wear machine. In addition, all the surfaces were evaluated with scanning electron microscopy.ResultsThe highest average wear was observed in the case of dentin. The lowest average wear was found EMAX. In every case—except for EMAX—the wear rate was higher with HC than with CC (all differences being statistically significant).ConclusionsThe level of wear of enamel, dentin and various resin composites was higher in contact with HC than in CC, the wear of dentin being the highest. In the case of a patient with no or little tooth wear or whose teeth are restored with composite material or glass‐ceramic, the splint HC might be preferred because of its better durability. However, when the splint is in contact with opposing dentin preservation of the dentin, CC might be the best choice.

Vitamin E: A potential preventive approach against dental erosion-an in vitro short-term erosive study

ObjectivesThis study evaluated the in vitro effect of different components of palm oil on enamel in a short-term erosive challenge. MethodsThe acquired enamel pellicle (AEP) was previously formed in situ for 2 h. Subsequently, the bovine enamel blocks were treated in vitro according to following solutions: G1–palm oil; G2–85% tocotrienol solution; G3–oily vitamin E; G4–oily vitamin A; G5–deionized water (negative control); G6-stannous-containing solution (Elmex® Erosion Protection Dental Rinse) (positive control). After application of the treatment solutions (500 µl, 30 s), the blocks were immersed in 0.5% citric acid (pH 2.4) during 30 s (initial erosion). The response variable was the percentage of surface hardness loss. Data were analyzed by one-way ANOVA and Fisher's Test (p < 0.05). ResultsThe positive control (G6), palm oil (G1) and oily vitamin E (G3) groups presented the lowest percentage of surface hardness loss, and were statistically different from the negative group (G5) (p < 0.05), and no differences were found between these three groups. The 85% tocotrienol solution (G2) and oily vitamin A groups (G4) were not different to the negative control group. ConclusionsStannous-containing positive control (Elmex® Erosion Protection), palm oil and oily Vitamin E were able to protect enamel against the erosive challenge performed in this in vitro study. In addition, vitamin E is probably the key ingredient of palm oil responsible for preventing enamel erosion. Clinical significanceVitamin E presented similar preventive effect to a commercial mouthwash stannous-containing solution (Elmex® Erosion Protection) against initial erosion and, it can be considered as a promising natural alternative for the formulations of solutions aiming to prevent erosive tooth wear.

Análise da eficácia de dentifrícios clareadores e seus efeitos na superfície dental: um estudo in vitro

Tooth whitening can be performed at the dental office, at-home or upon the use of OTC (Over-the-Counter) products. Among the latter, there are whitening toothpastes that promise to bleach and to prevent tooth staining. Objectives: (1) to investigate the bleaching and abrasive potential of different whitening dentifrices to enamel; and (2) to evaluate the effect of Oral-B 3D White Perfection® (Oral-B) toothpaste in preventing staining. Materials and Methods: Bovine enamel samples were stained and brushed for 14 days with water (negative control) or with different products: Colgate Total 12® (control), Oral-B, Sensodyne Branqueador Extra Fresh® (Sensodyne), and Colgate Luminous White Advanced® (Colgate). Oral-B was also tested before and after staining. The samples were tested by their color (spectrophotometer) and surface roughness (profilometer). Color change (ΔDE00) was calculated using the CIEDE2000 color system. The data were analyzed using Kruskal-Wallis, SNK, and Mann-Whitney tests (ɑ=5%). Results: The negative control showed the lowest ΔE00 (p

Interactions of boron released from surface pre-reacted glass ionomer with enamel/dentin and its effect on pH

This study investigated the interaction of borate ions released from surface pre-reacted glass ionomer (S-PRG) fillers with the biological apatites of enamel and dentin using solid-state (SS) magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy analysis. We further evaluated the effect of borate ions on the pH change. Bovine enamel and dentin powder were submerged in S-PRG eluate (with borate ion concentration of 100 mM) for 3 h, then washed with deionized water (DW). The dried enamel and dentin specimens were used for 11B SS-NMR and Fourier transform infrared spectroscopy (FT-IR) analysis. Enamel and dentin blocks were treated with three solutions: DW (control), S-PRG eluent and borate solution (100 mM). The treated samples were submerged in the demineralization solution and the pH was measured using a pH meter daily for 6 days. The surfaces of the enamel and dentin blocks were then observed using field emission scanning electron microscopy (FE-SEM). SS-NMR analysis revealed the presence of adsorbed borate ions in the enamel and dentin samples in a tetra-coordinated form. The pH results demonstrated an increase in pH values in the S-PRG and borate groups. SEM images showed that the surfaces of the control group were demineralized, whereas the surfaces of the S-PRG and borate groups were intact. These results concluded that borate ions could be adsorbed to enamel and dentin in the tetra-coordinated form. Borate ions possess a buffer capacity which may help to protect the tooth structure against acid attacks and promote remineralization.

In Vitro Evaluation of the Effectiveness of Dental Bleaching with Carbamide Peroxide and Violet Light.

Objective: The aim of the current study was to use the CIELab system to evaluate the performance of the whitening treatment involving violet light-emitting diode (LED) combined with a home 10% and 22% carbamide peroxide dental bleaching technique on dental enamel. Methods: Fifty blocks of bovine dental enamel were divided into five groups: control group (control), receiving only LED irradiation; Whitening 10%, receiving 10% carbamide peroxide treatment; Whitening 10%+VL, receiving 10% carbamide peroxide treatment combined with LED irradiation; Whitening 22%, receiving 22% carbamide peroxide treatment; and Whitening 22%+VL, receiving 22% carbamide peroxide treatment combined with violet LED irradiation. Color tests were performed before the protocols, after 1 week and after 2 weeks of treatment by using a spectrophotometer and the CIELab parameters: L*, (a*) and (b*). The Whitening 10%, Whitening 10%+VL, Whitening 22% and Whitening 22%+VL groups were submitted to 10% and 22% carbamide peroxide 8 h per day for 14 days, whereas the Control was only stored in artificial saliva. For irradiation in the Control, Whitening 10%+VL, and Whitening 22%+VL groups, we used violet LED at a wavelength of 405-410 nm activated for 60 permanent seconds and 30 sec of pause once per week. As all data exhibited normal distribution, the comparisons were performed by using two-way repeated-measures analysis of variance. A post hoc t-test was employed, followed by the Ryan-Holm stepdown Bonferroni procedure. Results: After 1 week, the Whitening 22%+VL group differed significantly from all other groups in relation to hue, while no difference was found between the remaining groups (p < 0.05). Analyzing lightness, the Whitening 22%+VL and Whiteness10%+VL groups differed from the other groups (p > 0.05). In the 2nd week, the Whitening 22%+VL groups differed significantly from all other groups (p < 0.05) in hue, chroma, and lightness. The comparative analysis of bleaching times within the same group revealed significant differences in the Whitening 22%+VL group between baseline and week 1, baseline and week 2, as well as weeks 1 and 2 in terms of hue (p > 0.05). In the Whitening 22%+VL group, significant differences (p < 0.05) were found between baseline and week 2 as well as between weeks 1 and 2 in chroma (p > 0.05). In the Whitening 22%+VL group, statistically significant differences (p < 0.05) were found between baseline and week 1, baseline and week 2, as well as between weeks 1 and 2 in lightness. In the Whitening 10%+VL group, statistically significant differences (p < 0.05) were found between baseline and week 1, between baseline and week 2, as well as between weeks 1 and 2 in lightness. Conclusions: Tooth whitening treatment involving 10% and 22% carbamide peroxide combined with violet light promoted changes in the three axes of color (ΔH, ΔC, and ΔL) of the specimens evaluated. The use of the gel bleach alone was more efficient when the higher concentration was used. When violet light was combined with the gel, the lower concentration was more efficient.

The influence of biofilm maturation on fluoride's anticaries efficacy.

(1) To explore the influence of biofilm maturation and timing of exposure on fluoride anticaries efficacy and (2) to explore biofilm recovery post-treatment. Bovine enamel specimens were utilized in a pH cycling model (28 subgroups [n = 18]). Each subgroup received different treatments [exposure]: sodium fluoride [NaF]; stannous fluoride [SnF2]; amine fluoride [AmF]; and de-ionized water [DIW], at a specific period: early: days 1-4; middle: days 3-6; and late: days 7-10. During non-exposure periods, pH cycling included DIW instead of fluorides. Objective 1: part 1 (cycling for 4, 6, or 10days). Part 2 (cycling for 10days). Objective 2: early exposure: three sample collection time points (immediate, 3days, and 6days post-treatment); middle exposure: two sample collection time points (immediate, 4days post-treatment). The enamel and biofilm were analyzed ([surface microhardness; mineral loss; lesion depth]; [lactate dehydrogenase enzyme activity; exopolysaccharide amount; viability]). Data were analyzed using ANOVA (p = 0.05). Objective 1: Early exposure to fluorides produced protective effects against lesion progression in surface microhardness and mineral loss, but not for lesion depth. Objective 2: Early exposure slowed the demineralization process. SnF2 and AmF were superior to NaF in reducing LDH and EPS values, regardless of exposure time. They also prevented biofilm recovery. Earlier exposure to SnF2 and AmF may result in less tolerant biofilm. Early fluoride treatment may produce a protective effect against demineralization. SnF2 and AmF may be the choice to treat older biofilm and prevent biofilm recovery. The study provides an understanding of biofilm-fluoride interaction with mature biofilm (e.g., hard-to-reach areas, orthodontic patients) and fluoride's sustainable effect hours/days after brushing.

Effect of Cold Atmospheric Pressure Plasma Coupled with Resin-Containing and Xylitol-Containing Fluoride Varnishes on Enamel Erosion.

Purpose Considering the suggested advantages of cold atmospheric plasma (CAP) in increasing the fluoride uptake by the enamel, this study aimed to assess enamel erosion following the application of helium CAP and two types of fluoride varnishes. Methods The microhardness of 70 bovine enamel specimens was measured using a Vickers hardness tester. The specimens were randomly divided into 7 groups (n = 10): control, CAP (P), resin-containing fluoride varnish (RF), CAP + resin-containing fluoride varnish (PRF), fluoride varnish (F), CAP + fluoride varnish (PF), and erosion (E). The specimens in the control and erosion groups did not receive CAP or fluoride varnish. All specimens underwent erosive challenge 4 times/day using hydrochloric acid and artificial saliva except for the control specimens that remained in distilled water during the course of the study. After 5 days of erosive challenge, microhardness was measured again, and the percentage of microhardness change was calculated. Surface roughness of two specimens in each group was assessed by atomic force microscopy (AFM). Data were analyzed using one-way ANOVA followed by Tamhane's post-hoc test. Results The percentage of microhardness change in all groups was significantly higher than that of the control group. All groups showed significantly lower percentage of microhardness change compared with the E group except for the P group; no significant difference was noted in microhardness change of P and E groups. Other experimental groups had no significant difference with each other. Surface roughness was the highest in PRF and the lowest in the F group. Conclusion CAP application had no significant effect on increasing the enamel resistance to erosion. However, enamel resistance to erosion increased significantly after fluoride varnish application alone or fluoride varnish application combined with CAP. No significant difference was noted between the two types of varnishes in this regard. CAP increased the surface roughness while fluoride varnish application alone decreased the roughness.

Effect of HAP crystallite orientation upon corrosion and tribocorrosion behavior of bovine and human dental enamel

Due to the complexity of the oral environment, understanding the relationship between the enamel microstructure and corrosion behavior of mammalian teeth is important for the development and bionic design of novel dental materials with corrosion resistance. In this paper, enamel microstructure and its influence on corrosion and tribocorrosion behavior of bovine and human molars are studied using focused ion beam & scanning electronic microscopy (FIB-SEM), transmission electron microscope (TEM), nanoindentation, and wear testing. It was found that the regions with transversal HAP nanocrystallites have better corrosion resistance than those with longitudinal crystallites. Apart from the chemical composition, the microstructure of enamel also involves in its surface corrosion. HAP nanocrystallite orientation changes the acid permeability into the enamel surface. Transversal nanocrystallites result in zigzagged acid permeation channels to increase the difficulty of acid penetration and then improve the corrosion resistance of enamel surface. The higher the fraction of transversal nanocrystallites on a surface, the better is the corrosion resistance. These findings extend our understanding of the corrosion/wear mechanisms of dental enamel with different microstructures.

Efficacy of fluoride varnishes with different compositions on white spot lesions remineralization

Objective: To evaluate the efficacy of different fluoride varnishes on white spot lesions (WSL) remineralization. Material and Methods: Polished bovine enamel specimens were obtained (n = 60) and had their initial surface Knoop microhardness (SMH) determined. WSL were created and the SMH was measured again. Then, specimens were allocated into six groups: C – Control (without varnish); BF – Bifluorid 12 (6% NaF + 6% CaF2); DP – Duraphat (5% NaF); PF – Profluorid (5% NaF); FP - Fluor Protector (0.2% NaF + 0.9% difluorsilane); CW - Clinpro White Varnish (5% NaF + 5% TCP). After varnishes application, specimens were immersed in artificial saliva for 24 h. Then, pH-cycling was performed for 8 days and SMH was measured. Data were analyzed by one-way ANOVA and Tukey’s test. Results: Non-significant differences were observed among the groups at baseline (p = 0.187) and after WSL formation (p = 0.999). After treatments, significant differences were observed among the groups (p = 0.001). Mean % of alteration (SD) and results of Tukey test were: C- 92.40 (12.10)a; PF- 88.66 (10.66)a; FP- 85.90 (14.49)ab; BF- 67.85 (17.86)bc; CW- 66.60 (18.48)c; DP- 58.62 (8.69)c. Conclusion:. Bifluorid 12, Clinpro White Varnish, and Duraphat showed higher efficacy than artificial saliva in promoting the remineralization of WSL, nevertheless, none of the treatments were able to recover sound enamel baseline microhardness. Keywords Dental caries; Fluoride; Fluoride varnishes.