Methodology to Quantify and Screen the Demineralization of Teeth by Immersing Them in Acidic Drinks (Orange Juice, Coca-Cola™, and Grape Juice): Evaluation by ICP OES.

Oral health problems may occur as a result of the ingestion of acid drinks. The objective of this in vitro study was to quantify and screen the concentration of potassium (K), phosphorus (P), calcium (Ca), magnesium (Mg), manganese (Mn), zinc (Zn), iron (Fe), copper (Cu), barium (Ba), lead (Pb), arsenic (As), cadmium (Cd), aluminum (Al), cobalt (Co), chromium (Cr), molybdenum (Mo), sodium (Na), nickel (Ni), selenium (Se), and vanadium (V) released from bovine incisors during an erosive challenge at different times of exposure when immersed in Coca-Cola™, orange juice, and grape juice. A total of 240 samples of bovine incisor teeth were used for the erosive challenge and allocated in groups. Digestion of drinks was performed using microwave-assisted digestion. The content in acidic drinks was monitored before and after the erosive challenge at exposure times of 1, 5, and 60 min using inductively coupled plasma optical emission spectrometry (ICP OES). The drinks' pH varied slightly during the erosive challenge but remained below the critical value of pH 5 to cause tooth demineralization. The concentrations of elements released from the bovine incisors during the in vitro erosive challenge depend on exposure times when immersed in acidic beverages. For some elements such as Ca, Mn, Zn, Fe, Cu, Ba, Pb, As, and Cd, quantified in acidic drinks, grape juice had greater erosive potential than Coca-Cola™ and orange juice. Quantification and monitoring of chemical elements in bovine teeth can be performed considering a longer erosive time and other types of acidic drinks. Further analysis using human teeth is still not available and must be conducted. The demineralization of teeth not only occurs in acidic beverages; physical and chemical factors play other roles and should be investigated.

An unusual disordered alveolar bone material in the upper furcation region of minipig mandibles: A 3D hierarchical structural study.

Teeth are subjected to compressive loads during mastication. Under small loads the soft tissue periodontal ligament (PDL) deforms most. However when the loads increase and the PDL is highly compressed, the tooth and the alveolar bone supporting the tooth, begin to deform. Here we report on the structure of this alveolar bone in the upper furcation region of the first molars of mature minipigs. Using light microscopy and scanning electron microscopy (SEM) of bone cross-sections, we show that this bone is hypermineralized, containing abundant small pores around 1-5 µm in diameter, lacunae around 10-20 µm as well as larger spaces. This bone does not possess the typical lamellar motif or other repeating structures normally found in cortical or trabecular mammalian bone. We also use high resolution focused ion beam scanning electron microscopy (FIB-SEM) in the serial surface mode to image the 3D organization of the demineralized bone matrix. We show that the upper furcation bone matrix has a disordered isotropic structure composed mainly of individual collagen fibrils with no preferred orientation, as well as highly staining material that is probably proteoglycans. Much larger aligned arrays of collagen fibers - presumably Sharpey's fibers - are embedded in this material. This unusual furcation bone material is similar to the disordered material found in human lamellar bone. In the upper furcation region this disordered bone comprises almost all the volume excluding Sharpey's fibers. We surmise that this most unusual bone type functions to resist the repeating compressive loads incurred by molars during mastication.

The Effects of Fluoride Treatment Time and Concentration on In Vitro Caries Lesion Demineralisation and Remineralisation.

PURPOSE: To investigate the possible interaction between fluoride treatment time and concentration on enamel caries lesion de-/remineralisation. MATERIALS AND METHODS: The study design followed a three (fluoride concentration: 0, 275, 1250 ppm as sodium fluoride) x four (treatment time: 10, 30, 60, 120 s) factorial design. Caries lesions were created in bovine enamel and the extent of demineralisation determined using Vickers surface microhardness (VHN). Lesions were pH cycled (18 days) with the daily schedule consisting of two fluoride treatments, a 4-h demineralisation period and exposure to artificial saliva at all other times. VHN was determined again after pH cycling and changes to baseline values calculated (∆VHN). Enamel fluoride uptake (EFU) was determined using the microbiopsy technique. Data were analyzed using two-way ANOVA. RESULTS: The concentration x treatment time interaction was significant for ∆VHN (p < 0.0001) and EFU (p = 0.0298). Dose-response relationships were observed for both variables for fluoride concentration and treatment time. ∆VHN: higher fluoride concentration compensated for shorter treatment time (e.g. ∆VHN [mean ± SD] = 85.5 ± 60.6 for 30 s with 1250 ppm fluoride vs ∆VHN = 84.3 ± 26.9 for 120s with 275 ppm fluoride). EFU data were similar but highlighted a greater ability to discern between fluoride concentrations (e.g. EFU = 4364 ± 1166 ppm vs 8538 ± 9531 ppm; above examples). Although ∆VHN and EFU correlated well (r = 0.723; p < 0.001), lesion demonstrated a greater ability to acquire fluoride than to remineralise. CONCLUSIONS: Behavioural aspects relating to caries can be studied in vitro, although model limitations must be considered. Adequate exposure times to cariostatic concentrations of fluoride are important in maximising caries prevention.

Bacterial factors of cariogenicity (literature review).

OBJECTIVE: Introduction: According to the 2003 WHO report, dental caries affects from 60% to 90% of school-age children and adults that makes it one of the most common diseases worldwide. The aim was to systematize data about the modern conception of plaque formation and role of microorganisms in its development. PATIENTS AND METHODS: Materials and methods: Biblosemantic, 50 medical literature sources were systematically reviewed as the material for the research. RESULTS: Review: According to Miller's theory, oral microorganisms can decompose dietary carbohydrates into acids, which in turn dissolve the calcium phosphates found in the enamel, causing it demineralisation Along with Streptococcus mutans, nowadays some other bacteria as Streptococcus sorbinus, Lactobacillus spp. and Actinomyces spp. have been well studied as caries contributors. However, the disease is related to plaque-mediated, because a much larger number of normal oral microflora representatives are involved in creating favourable preconditions for its development. There are a lot of original research papers about a role of bacteria in caries decay but compositions and characters of oral microflora are changing nowadays. Therefore, authors show the main cariogenic bacteria and their factors of pathogenicity which create special conditions for caries lesions. Modern concepts of dental plaque formation and pathogenesis of plaque-assosiative diseases are presented according to the new actual dental research. A lot of attention is paid to the biochemical properties of cariogenic bacteria and chemical process in biofilm. Role of acid and alkali production by oral bacteria in caries decay are shown in this article. Moreover, mechanisms of bacterial acid-fast and acid-tolerance are presented. CONCLUSION: Conclusions: Analysis of literature demonstrates a lot of bacterial pathogenicity factors which play key role in caries development.

Influence of multi-wavelength laser irradiation of enamel and dentin surfaces at 0.355, 2.94, and 9.4 µm on surface morphology, permeability, and acid resistance.

OBJECTIVE: Ultraviolet (UV) and infrared (IR) lasers can be used to specifically target protein, water, and mineral, respectively, in dental hard tissues to produce varying changes in surface morphology, permeability, reflectivity, and acid resistance. The purpose of this study was to explore the influence of laser irradiation and topical fluoride application on the surface morphology, permeability, reflectivity, and acid resistance of enamel and dentin to shed light on the mechanism of interaction and develop more effective treatments. METHODS: Twelve bovine enamel surfaces and twelve bovine dentin surfaces were irradiated with various combinations of lasers operating at 0.355 (Freq.-tripled Nd:YAG (UV) laser), 2.94 (Er:YAG laser), and 9.4 µm (CO2 laser), and surfaces were exposed to an acidulated phosphate fluoride gel and an acid challenge. Changes in the surface morphology, acid resistance, and permeability were measured using digital microscopy, polarized light microscopy, near-IR reflectance, fluorescence, polarization sensitive-optical coherence tomography (PS-OCT), and surface dehydration rate measurements. RESULTS: Different laser treatments dramatically influenced the surface morphology and permeability of both enamel and dentin. CO2 laser irradiation melted tooth surfaces. Er:YAG and UV lasers, while not melting tooth surfaces, showed markedly different surface roughness. Er:YAG irradiation led to significantly rougher enamel and dentin surfaces and led to higher permeability. There were significant differences in acid resistance among the various treatment groups. CONCLUSION: Surface dehydration measurements showed significant changes in permeability after laser treatments, application of fluoride and after exposure to demineralization. CO2 laser irradiation was most effective in inhibiting demineralization on enamel while topical fluoride was most effective for dentin surfaces. Lasers Surg. Med. 49:913-927, 2017. © 2017 Wiley Periodicals, Inc.

In vitro Induction of residual caries lesions in dentin: comparative mineral loss and nano-hardness analysis.

Artificially inducing dentinal lesions mimicking those remaining after selective excavation should allow to investigate the effects and limits of such selective excavation, for example regarding the mechanical properties of treated teeth or the remineralisation of sealed residual lesions. Such analyses might otherwise be limited by the variability of natural lesions or ethical and practical concerns. This study compared different demineralisation protocols for their suitability to induce lesions similar to natural residual caries. Twelve natural deep lesions were excavated until leathery dentin remained, and analysed for their mineral loss (ΔZ), lesion depth (LD), mineral loss ratio (R), the slope of the mineral gradient and their nano-hardness profile. Artificial lesions were induced using four different demineralisation protocols (acetic acid pH = 4.95; 0.1 M lactic acid gel pH = 5.0; 0.5 M ethylenediaminetetraacetic acid pH = 7.2; Streptococcus mutans biofilms) and their depths monitored over different demineralisation times. Lesions with depths most according to those of natural lesions were analysed using transversal microradiography. Lesions induced by acetic acid solution did not significantly differ with regards to LD, ΔZ, R and mineral profile. Seven dentin specimens were subsequently submitted to a moderately acidic (pH = 5.3) methylhydroxydiphosphonate-buffered acetate solution for 12 weeks. Natural and artificial residual lesions were similarly deep (mean ± SD: LD = 626 ± 212 and 563 ± 88 µm), demineralised (R = 19.5 ± 4.7 and 29.8 ± 4.1%), showed a flat and continuous mineral gradient (slope = 0.10 ± 0.05 and 0.13 ± 0.06 vol%/µm) and did not significantly differ regarding their nano-hardness profile. The described protocol induces lesions with mineral content and mechanical properties similar to natural residual lesions.

Enamel demineralization after different methods of interproximal polishing.

OBJECTIVES: The aim of this in vitro study was to investigate the demineralization rate in human enamel after interproximal polishing (IPP) and to detect possible correlations with the IPP method used, with special emphasis on the surface characteristics of the enamel being treated. MATERIALS AND METHODS: This in vitro study tested five IPP systems (Profin Directional System®, Intensiv ProxoStrip®, OS discs®, ARS Safe-Tipped Bur Kit® and Ortho-Strips Set®) that are currently available on the market. Each of the five examination groups comprised 12 randomly selected teeth, while the control group consisted of six teeth. The teeth were placed in an artificial model for each group. The proximal contacts were then resolved by IPP. To allow detection of any surface characteristics, one surface was not further processed after IPP, while the other side was additionally polished. After IPP, the teeth were exposed to a pH-cycling model with alternating phases of demineralization and remineralization. Substance loss was analyzed using optical emission spectrometry. Data were subjected to simple analysis of variance (ANOVA) performed with Tukey's test. Comparison between the groups with and without polishing was conducted using the t test for independent samples. The significance level was set at p < 0.05. RESULTS: Demineralization significantly increased after IPP. The rates of demineralization differed significantly among the examination groups, with the greatest loss of substance being produced with Sheridan's Air-Rotor Stripping® system (ARS; 145.34 ± 20.37 µm). In all of the examination groups, subsequent polishing of the surfaces did not significantly reduce the amount of demineralization (polished 119.64 ± 28.61 µm; unpolished 114.16 ± 28.61 µm). CONCLUSION: No correlation between surface morphology and the degree of susceptibility of human enamel was detected. However, it must be taken into consideration that there was no potential bacterial colonization in this in vitro erosive set-up. Thus, in contrast to previous explanations, the outermost fluorapatite layer and the individual composition of the enamel may have a greater impact on the solubility of the enamel and the amount of enamel loss after IPP than the type of system used and the resulting surface texture. CLINICAL RELEVANCE: Whenever the outermost layer of enamel is reduced, the practitioner must expect an increase in demineralization. Subsequent polishing does not appear to affect the amount of demineralization.

Cerium chloride reduces enamel lesion initiation and progression in vitro.

AIM: Determination of the potential of cerium chloride to reduce artificial carious mineral loss and lesion depth progression. METHODS: A total of 160 enamel samples were prepared from 40 bovine lower central incisors. Crowns were sectioned into four pieces, embedded in acrylic resin, ground flat and allocated to eight groups (S1-S4 and D1-D4; n = 20). Specimens of groups D1-D4 were stored (for 7 days) in a demineralizing buffer solution to induce caries-like lesions. Afterwards, samples were treated for 30 s with one of the following solutions: placebo (S1 and D1), amine fluoride (S2 and D2), cerium chloride (S3 and D3) and a combination of fluoride and cerium chloride (S4 and D4). After another 7 (D1-D4) or 14 (S1-S4) days in demineralizing buffer solution, integrated mineral loss and lesion depth were determined by transversal microradiography and compared by Scheffé's post hoc tests. RESULTS: In groups S1-S4, the highest values for integrated mineral loss and lesion depth were observed for group S1 (placebo), the lowest values for group S4. The results in groups S2-S4 were not significantly different. In groups D1-D4, the highest values for integrated mineral loss and lesion depth were observed for group D1 (placebo), the lowest values in groups D3 and D4. In group D2, integrated mineral loss and lesion depth were significantly lower as compared to D1, but significantly higher compared to groups D3 and D4. CONCLUSION: Cerium chloride and its combination with fluoride are able to significantly reduce carious mineral loss and the progression of lesion depth.

Numerical modelling of tooth enamel subsurface lesion formation induced by dental plaque.

Using a one-dimensional mathematical model that couples tooth demineralisation and remineralisation with metabolic processes occurring in the dental plaque, two mechanisms for subsurface lesion formation were evaluated. It was found that a subsurface lesion can develop only as the result of alternating periods of demineralisation (acid attack during sugar consumption) and remineralisation (resting period) in tooth enamel with uniform mineral composition. It was also shown that a minimum plaque thickness that can induce an enamel lesion exists. The subsurface lesion formation can also be explained by assuming the existence of a fluoride-containing layer at the tooth surface that decreases enamel solubility. A nearly constant thickness of the surface layer was obtained with both proposed mechanisms. Sensitivity analysis showed that surface layer formation is strongly dependent on the length of remineralisation and demineralisation cycles. The restoration period is very important and the numerical simulations support the observation that often consumption of sugars is a key factor in caries formation. The calculated profiles of mineral content in enamel are similar to those observed experimentally. Most probably, both studied mechanisms interact in vivo in the process of caries development, but the simplest explanation for subsurface lesion formation remains the alternation between demineralisation and remineralisation cycles without any pre-imposed gradients.

DENTINE CARIES: ACID-TOLERANT MICROORGANISMS AND ASPECTS ON COLLAGEN DEGRADATION.

Dental caries is a common disease all over the world, despite the fact that it can be both effectively prevented and treated. It is driven by acids produced by oral microorganisms as a consequence of their metabolism of dietary carbohydrates. Given enough acid challenge, eventually the tooth enamel barrier will be broken down, and the carious lesion will extend into underlying hard tissue, forming a macroscopic cavity in the dentine. In comparison to biofilm on enamel, a dentine carious lesion provides a vastly different environment for the residing microorganisms. The environment influences the types and numbers of microorganisms that can colonize the dentine caries lesion. The overall aims for this thesis are to enumerate and further study microorganisms found in established dentine caries lesions and also to illuminate how host-derived proteolytic enzymes might contribute to this degradation, not only to better understand the caries process in dentine but also to find incitements for new methods to influence the natural progression of caries lesions. In Paper I, the numbers of remaining viable microorganisms after completed excavation using two excavation methods were investigated. Samples of carious dentine tissue were collected before and after excavation and cultivated on different agar media in different atmospheres. Analysis was performed by counting the number of colony-forming units (CFUs). Key findings: The number of remaining microorganisms after excavation was low for both methods, but some microorganisms always remained in the cavity floors even when the cavities were judged as caries free using normal clinical criteria. In Paper II, the acid tolerant microbiota in established dentine caries lesions was investigated. Samples were taken as in Paper I, but on three levels (superficial, center of lesion, floor of lesion after completed excavation). The samples were cultivated in anaerobic conditions on solid pH-selective agar media of different acidity. Key findings: Each investigated lesion harbored a unique microbiota in terms of both species composition and numbers of microorganisms. This indicates that various combinations of aciduric microorganisms can colonize, survive in and probably also propagate dentine carious lesions. We also found that solid pH-selective agars can be used successfully to select acid-tolerant microorganisms in caries lesions. This would preserve their phenotypic traits for further study. In Paper III, the relation between salivary levels of matrix metalloproteinase-8 (MMP-8), salivary levels of tissue inhibitor of MMP (TIMP-1), and the presence of manifest caries lesions in a large number of subjects was investigated. Saliva samples were collected and analyzed for concentrations of MMP-8, TIMP-1 and total protein using immunofluorometric assays, enzyme linked immunosorbent assays and Bradford assays, respectively. Key findings: Subjects with manifest caries lesions had significantly elevated levels of salivary MMP-8 compared to subjects without caries lesions. TIMP-1 was not significant in any case. In Paper IV, a new method for generating bioactive demineralized dentine matrix substrate (DDM) was developed using a dialysis system and two different demineralization approaches (acetic acid or EDTA). The generated DDM was subsequently analyzed for the presence of type 1 collagen, active MMP-8 and hydroxyproline (HYP) levels using SDS-PAGE, ELISA or immunofluorescence assay. Key findings: Both demineralization methods produced a substrate rich in collagen and with preserved MMP-8 activity. This report presents new knowledge on the composition of the acid tolerant dentine caries microbiota from three levels in dentine carious lesions and on the efficacy of operative caries removal on the numbers of viable microorganisms in the caries free cavity using two operative methods. Moreover, the basic mechanisms behind collagen degradation in the dentine caries process are studied from both a clinical and laboratory perspective. The report also provides a reference for further studies on dentine caries microbiology and dentine caries collagen degradation mechanisms, both of which are known only in part.

Does post-bleaching fluoridation affect the further demineralization of bleached enamel? An in vitro study.

BACKGROUND: Topical fluoride agents have been shown to be the most effective method in treating demineralized enamel after in-office bleaching treatments. Thus, this study aimed to examine the effects of two different post-bleaching fluoridation agents: 1.5% titanium tetrafluoride (TiF(4)) (9200 ppm) and 2.1% sodium fluoride (NaF) (9500 ppm), on the calcium loss of enamel after an acidic challenge. METHODS: Ten maxillary premolars were sectioned into four pieces and then divided into the following four groups: Group 1: Control, kept in artificial saliva, no treatment; Group 2: 38% hydrogen peroxide (HP); Group 3: 38% HP followed by 1.5% TiF(4); Group 4: 38% HP followed by 2.1% NaF solution. The specimens were subjected to demineralization for 16 days, refreshing the solution every 4 days; that is, on the 4th, 8th, 12th, and 16th days. Calcium ion (Ca(2+)) concentration was determined by an atomic absorption spectrophotometer. Data were analyzed using Friedman and Wilcoxon tests (p = 0.05). RESULTS: The loss of Ca(2+) in each of the test groups was compared with that of the control group, depicting that there was a statistically significant difference among the groups after 4, 8, 12, and 16 days and in total (p < 0.05). The calcium released from the fluoride-applied groups was lower when compared with the 38% HP and control group. At the end of the 16th day, the total amount of calcium released from the TiF(4-)treated samples (9.12 mg/mL) was less than from the NaF-treated samples (13.67 mg/mL) (p < 0.05). CONCLUSIONS: Regarding the results of our in vitro study, the risk of further demineralization was significantly reduced with the use of TiF(4) and NaF after bleaching with 38% HP. TiF(4) was found to be more effective in preventing Ca2+ release owing to acid attack when compared with NaF. In the case of an intra-oral acidic exposure, the use of topical 1.5% TiF(4) and 2.1% NaF agents might be beneficial after bleaching with 38% HP.

Effect of three different remineralizing agents on enamel caries formation--an in vitro study.

BACKGROUND: Caries process is not a static one, but is dynamic with interspersed periods of demineralization and remineralization of enamel, intimately related and occurs episodically based upon the presence of cariogenic bacteria in dental plaque and the availability of refined carbohydrates for fermentation to organic acids. OBJECTIVES: Early enamel caries could be reversed with avoidance of frank cavitation. The main objective of this study is to check wether enamel demineralization can be prevented by using the remineralizing agents. METHOD: Forty freshly extracted human central incisors were selected and stored in saline at normal temperature. A window of 3 X 3mm enamel was created and all the specimens were then randomly divided into 4 groups of 10 each. Group I--teeth received no treatment, Group II--teeth treated with Acidulated Phosphate Flouride gel, Group III--teeth treated with Tooth Mousse Plus, Group IV--teeth treated with Remin+. Samples in all the groups were kept in artificial saliva for 24 hours and subjected to modified Ten Cate's solution at an acidic pH of 3.5 for 10 days. The samples were sectioned and subjected to SEM evaluation. RESULT: Scanning Electron Microscope(SEM) images showed decrease in pore volume of the enamel in all the treatment groups compared to the control group indicating increase in resistance to demineralization in acidic pH. CONCLUSION: The three groups of remineralizing agents, Acidulated Phosphate Fluoride gel, Tooth Mousse Plus and Remin + showed significant increase in fluoride content and negligible increase in calcium content indicating there is remineraliztion.

Characterizing and identifying incipient carious lesions in dental enamel using micro-Raman spectroscopy.

Early detection of dental caries is vital if improved patient outcomes are to be achieved by reversal of the demineralization process. Current techniques used by dentists for identifying carious lesions are effective in identifying more advanced lesions, but do not have sufficient sensitivity and specificity to detect them at the earliest stages. This study focused on characterizing the growth of incipient carious lesions in vitro using micro-Raman spectroscopy. The incipient carious lesions were grown on the buccal faces of human molars by controlled exposure to lactic acid. Lesions were cross-sectioned to expose the subsurface body of the lesion and then examined using micro-Raman spectroscopy. The intensity of the phosphate peaks in the Raman spectra was found to differ significantly between healthy enamel and the demineralized region of the lesions. The sensitivity of the phosphate peaks to the degree of demineralization was observed by taking a series of spectra over the cross section of the lesions. This revealed that the body of the lesion is highly demineralized, but in a narrow surface region (up to 10 µm) there is little demineralization. All the phosphate peaks were found to be sensitive to the degree of demineralization; however, changes in the intensity of the pronounced phosphate peak at 961 cm(-1) offer the most promise for identifying lesions. The results indicate that micro-Raman spectroscopy has both the sensitivity and selectivity to identify incipient carious lesions, but the presence of a surface layer with a relatively high mineral content could complicate the analysis.

Characteristics of methylcellulose acid gel lesions created in human and bovine enamel.

Acid gel caries lesions were created in 3,100 human and bovine enamel specimens and studied with transverse microradiography. Small, significant differences were found. Human enamel lesions were found to be less demineralized, shallower, had a higher ratio of integrated mineral loss (ΔZ) to lesion depth (L), a lower degree of surface zone mineralization (SZ(max)) and showed less variability than those in bovine enamel. SZ(max) showed the highest variability. Between tissues, L differed the most, ΔZ the least. Biological variation within bovine enamel is perhaps not only bigger than previously assumed, it may also overshadow any structural and chemical differences between tissues.

Estimation of the enamel and dentin mineral content from the refractive index.

Recent advances in the field of optics have enabled accurate and localized measurement of optical properties of biological substrates. This work aimed to elucidate the relationship between the local refractive index (n) and mineral content (MC) of enamel and dentin. De- and remineralized lesions in bovine enamel and dentin blocks were sectioned into 300- to 400-µm-thick slices, and placed on a metal plate to capture images of sound, de- and remineralized regions transversely by optical coherence tomography. Mean n at each depth level of the lesion (20- or 40-µm steps for enamel or dentin) was measured by the optical path length-matching method and used to plot n through lesion depth. The specimens were further polished and processed for transverse microradiography for analysis of MC. The n and MC ranged from 1.52 to 1.63 and 50 to 87 (vol.%) in enamel, and from 1.43 to 1.57 and 11 to 48 (vol.%) in dentin, respectively. Strong, positive linear correlations were found between n and MC (Pearson's r = 0.95 and 0.91 for de- and remineralized enamel, and r = 0.94 and 0.91 for dentin, respectively, p < 0.001). Experimental data were validated with a theoretical calculation of n from MC. De- and remineralization of enamel and dentin resulted in measurable changes of n, and, in turn, MC changes of the tissue could be estimated with good accuracy from this long-known optical property by the new analytical approach. Compositional changes of enamel crystallites after remineralization affect n.

Subablative Er:YAG laser effect on enamel demineralization.

OBJECTIVES: To characterize the cariostatic potential of a low-energy Er:YAG laser treatment. METHODS: Twelve sound premolars were selected. Two 2 × 1 mm windows were created on each tooth and randomly assigned to L(1) and L(2) groups. Three sites in each window were chosen with the middle site as the control and the left and right ones receiving Er:YAG laser treatment of 5.1 J/cm(2) (L(1)) or 2.0 J/cm(2) (L(2)), respectively. The teeth were further subjected to 4-day pH cycling to create caries-like lesions. After mineral quantification using a micro-computed tomography scanner, the preventive effects (ΔML = mineral loss of the control area minus that of the lased area) of L(1) and L(2) treatments were calculated based on the difference in the gray value of the control and lased sites. RESULTS: Significant inhibitory effects of L(1) and L(2) on enamel demineralization were demonstrated (both p ≤ 0.001), with the L(1) treatment having a greater effect (45.2%) than the L(2) treatment (25.2%, p = 0.004). CONCLUSIONS: Subablative low-energy Er:YAG laser irradiation can significantly prevent enamel demineralization potentially through the retardation of enamel diffusion. This study confirmed that high-energy laser treatment, which may damage the peripheral and underlying tissues, may not be needed for caries prevention.

Effect of dialyzed saliva on human enamel demineralization.

BACKGROUND: Saliva is supersaturated with respect to calcium and phosphate ions. Salivary ions may well play a role in the subsequent adsorption of proteins and consequently in the formation of the acquired enamel pellicle. Among several biological functions, the enamel pellicle forms a selectively permeable barrier that regulates demineralization processes. AIM: The aim of this study was to evaluate the importance of salivary proteins when adsorbed on enamel surface and the resultant protective effect against demineralization without the presence of salivary ions. METHODS: Enamel surfaces were coated with whole saliva, parotid saliva, dialyzed whole saliva or dialyzed parotid saliva (molecular weight cutoff 1 kDa). Adsorption was allowed to proceed for a period of 2 h. Enamel specimens were then washed with deionized water and immersed into a demineralization solution of pH 4.5 for 12 days. This solution was used to measure the amount of calcium and phosphate released from enamel specimens after the demineralization period. RESULTS: All coated specimen groups showed a significantly higher protection than those not coated with any type of saliva. In addition, undialyzed saliva (whole saliva and parotid saliva) was more effective in protecting the enamel against demineralization than dialyzed saliva. CONCLUSION: The present investigation indicates that the ionic composition of saliva can amplify the demineralization protection effect by reducing acid-induced enamel demineralization. Moreover, a protective effect of salivary proteins without presence of ions was demonstrated in this study.

Effects of fluoride on in vitro enamel demineralization analyzed by ¹9F MAS-NMR.

The mechanistic action of fluoride on inhibition of enamel demineralization was investigated using (19)F magic angle spinning nuclear magnetic resonance (MAS-NMR). The aim of this study was to monitor the fluoride-mineral phase formed on the enamel as a function of the concentration of fluoride ions [F(-)] in the demineralizing medium. The secondary aim was to investigate fluorapatite formation on enamel in the mechanism of fluoride anti-caries efficacy. Enamel blocks were immersed into demineralization solutions of 0.1 M acetic acid (pH 4) with increasing concentrations of fluoride up to 2,262 ppm. At and below 45 ppm [F(-)] in the solution, (19)F MAS-NMR showed fluoride-substituted apatite formation, and above 45 ppm, calcium fluoride (CaF2) formed in increasing proportions. Further increases in [F(-)] caused no further reduction in demineralization, but increased the proportion of CaF2 formed. Additionally, the combined effect of strontium and fluoride on enamel demineralization was also investigated using (19)F MAS-NMR. The presence of 43 ppm [Sr(2+)] in addition to 45 ppm [F(-)] increases the fraction of fluoride-substituted apatite, but delays formation of CaF2 when compared to the demineralization of enamel in fluoride-only solution.

Differences in loosely bound fluoride formation and anticaries effect of resin-based fluoride varnishes.

OBJECTIVE. Our in vitro study evaluated calcium fluoride formation in enamel and the anticaries effect of seven resin-based varnishes under cariogenic challenge. METHODS. Enamel blocks were subjected to pH cycling. The experimental groups received fluoride varnish application, the positive control received topical fluoride gel treatment, and the negative control did not receive any treatment. The pH cycling surface hardness (SH1 ) and integrated loss of subsurface hardness (ΔKHN) were then determined. We measured the amount of fluoride released into the demineralizing and remineralizing (DE-RE) solutions used in pH cycling. The fluoride concentration in the enamel was determined 24 h after application of the products as loosely bound fluoride and firmly bound fluoride. RESULTS. Higher deposits of loosely bound fluoride were observed for Duofluorid, followed by Biophat. For Duraphat, Bifluorid, Duraflur, and Duofluorid, no difference was observed in the SH1 and ΔKHN values, with the lowest mineral loss compared to the other groups. The Bifluorid and Duofluorid groups released high fluoride amounts into the DE-RE, and statistically significant difference was noted between them. CONCLUSIONS. The anticaries effect showed no correlation with higher deposited fluoride amounts, resin type, or fluoride source.

Long-term preservation of Bone Morphogenetic Activity in stored demineralized murine incisors.

Demineralized bone or dentine implanted intramuscularly induce endochondral bone formation. This phenomenon, termed "bone induction" is triggered by non-collagenous signal molecules, named "Bone Morphogenetic Proteins" (BMPs), released from bone or dentine. Demineralization of bone/dentine prior their implantation facilitates the release of BMPs from the extracellular matrix allowing to reach a BMP threshold level needed to initiate the process of differentiation of mesenchymal cells towards an osteogenic/chondrogenic lineage. Unprocessed, mineralized tissues usually fail to induce cartilage/bone. Isolated BMPs are commercially available, and in clinical practice are an alternative for demineralized tissues, however, in many cases demineralized bone has advantages over soluble BMPs, as it combines both bone inducing principles and mechanical properties, a feature important for bridging bone fracture and filling bone defects. Demineralized bones are an inexpensive source of bone forming agents for bone-fracture healing or filling bone defects. In this report we demonstrated that storage of lyophilized demineralized murine incisors for 30 months does not deteriorate its osteoinductive potency and colonizing induced bone by bone marrow. Lyophylized incisors, stored for 0-30 months at refrigator were implanted intramuscularly and recovered, together with surrounding tissues at various time intervals ranging 10-450 days. Bone closely associated with implant was observed in about 87% of cases, regardless the storage duration. It is concluded that storage of demineralized and lyophilized incisor matrices for at least 30 months does not change their osteoinductive potency.