The effect of silver diammine fluoride on In Vitro Enamel caries lesion remineralization and staining as a function of lesion baseline mineral distribution.

OBJECTIVES: to investigate whether baseline mineral distribution modulates the ability of silver diammine fluoride (SDF) to remineralize and stain enamel caries lesions. METHODS: This laboratory study followed a 3 [treatment: SDF/fluoride varnish (FV)/deionized water (DIW)] ×3 [lesion protocol: methylcellulose (MeC)/hydroxyethylcellulose (HEC)/Carbopol 907 (C907)] factorial design. Lesions were created in bovine enamel specimens (n = 20). Treatments were applied and lesions remineralized in artificial saliva. Digital transverse microradiography (TMR-D) was used to analyze lesions. Lesion color was monitored spectrophotometrically. The effects of lesion protocol and treatment on changes in lesion depth (ΔLD), mineral loss (ΔΔZ), maximum mineral density at the surface zone (ΔSZmax), and color changes related to remineralization (ΔL*remin) were analyzed using two-way ANOVA. RESULTS: The treatment×lesion protocol interaction was significant for ΔΔZ (p < 0.01) and ΔL*remin (p < 0.01), however not for ΔLD (p = 0.23) or ΔSZmax (p = 0.91). There were no differences in ΔΔZ between treatments in HEC and C907 lesions. However, DIW resulted in more remineralization than both SDF (p < 0.01) and FV (p = 0.01) in MeC lesions. Considering changes from lesion baseline after remineralization in MeC lesions, SDF treatment resulted in the highest mineral gain in the surface zone. However, DIW revealed the highest mineral gain after remineralization in the lesion body. SDF stained lesions with the intensity increasing after remineralization in C907 lesions, whereas staining decreased in MeC and HEC lesions. CONCLUSION: High fluoride treatments can interfere with continuous remineralization of caries lesions due to partial arrest. Baseline lesion mineral distribution affects SDF's ability to enhance remineralization and the staining caused by SDF. CLINICAL SIGNIFICANCE: SDF is being used to arrest active caries lesions extending into dentin and to treat dentin hypersensitivity. This study shed light on SDF's effect on an isolated process in dental caries only, remineralization. It achieved this by examining enamel caries lesions with differing mineral distributions and assessing their staining properties.

Enamel Caries Lesion Depth Obtained by Optical Coherence Tomography and Transverse Microradiography: A Comparative Study.

INTRODUCTION: Visual imaging of subsurface caries lesions is of vital interest in dentistry, which can be obtained by invasive radiography technique as well as by available non-destructive imaging approaches. Thus, as a first step toward the development of a new innovative approach, Spectral-domain optical coherence tomography (SD-OCT) was applied to detect the lesion depth in comparison to the established reference technique (transverse microradiography [TMR]). METHODS: Bovine enamel specimens were demineralized for 5 days, following previous studies. For OCT, the resulting artificial lesions were scanned three-dimensionally (SD-OCT) and semi-automated measured (CarLQuant). For TMR, specimens were sectioned and the lesion depth was manually determined (Inspektor Research System). RESULTS: The range of lesion depth detected with OCT was 24.0-174.0 µm (mouth rinse study), 18.0-178.0 µm (toothpastes study) and with TMR 59.2-198.0 µm (mouth rinse study), 33.2-133.4 µm (toothpastes study). We found a strong correlation between both methods in terms of lesion depth (Spearman rankwith outlierp < 0.001, Rho = 0.75, Spearman rankwithout outlierp = 0.001, Rho = 0.79). The two methods produce similar results (Passing-Bablok regression, 1.16). As deeper is the lesion, the smallest is the difference between both methods as indicated by Bland-Altman-plots. CONCLUSION: Especially in the case of deep lesions, the values obtained by both methods are in agreement, and OCT can potentially substitute TMR to detect and assess lesion depth with the benefit of being non-destructive.

Evaluation of Iontophoresis as a Tool in Comparison to Topical Remineralization Systems by Transverse Microradiography and Polarized Light Microscopy: An In Vitro Study.

Aim: To compare the efficacy of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) (GC Tooth Mousse) and tricalcium phosphate formulation (Clinpro) by topical application and iontophoresis. Background: Noninvasive treatment of dental caries is a major advance in the clinical management of the disease. Materials and methods: A total of 20 primary anterior and 20 primary molars were included in the study to be analyzed by transverse microradiography (TMR) and polarized light microscopy (PLM). The samples were coated with acid-resistant varnish, leaving a window on the buccal/lingual surface of enamel and immersed in demineralizing solution for 96 hours. Each sample was coated with varnish on the left half (control), and the right half served as a test. All the samples were divided into four groups. The test windows of specimens in groups I (GC Tooth Mousse) and II (Clinpro) were subjected to remineralization treatments for 10 days. Similarly, groups III and IV were subjected to iontophoresis using GC Tooth Mousse and Clinpro for 7 minutes. The samples were analyzed by TMR and PLM. Results: There was no significant difference in the mean difference of mineral loss among the four groups. There was a significant difference in the mean difference of lesion depth among the four groups. Conclusion: Both iontophoresis and topical application were equally efficient, but one remineralization by iontophoresis equals 10 topical applications. How to cite this article: VC R, Muppa R, Nallanchakrava S, et al. Evaluation of Iontophoresis as a Tool in Comparison to Topical Remineralization Systems by Transverse Microradiography and Polarized Light Microscopy: An In Vitro Study. Int J Clin Pediatr Dent 2023;16(S-1):S85-S90.

Evaluation of Resin Infiltration, Fluoride and the Biomimetic Mineralization of CPP-ACP in Protecting Enamel after Orthodontic Inter-Proximal Enamel Reduction.

BACKGROUND: This study investigated the effect of using different agents for protecting enamel proximal surfaces against acidic attack after interproximal reduction (IPR) using the trans micro radiography technique. METHODS: Seventy-five sound-proximal surfaces were obtained from extracted premolars for orthodontic reasons. All teeth were measured miso-distally and mounted before being stripped. The proximal surfaces of all teeth were hand stripped with single-sided diamond strips (OrthoTechnology, West Columbia, SC, USA) followed by polishing via Sof-Lex polishing strips (3M, Maplewood, MN, USA). Three-hundred micrometers of enamel thickness was reduced from each proximal surface. The teeth were randomly divided into 5 groups: group 1 (control un-demineralized) received no treatment, group 2 (control demineralized) had their surfaces demineralized after the IPR procedure, group 3 (fluoride) specimens were treated with fluoride gel (NUPRO, DENTSPLY, Charlotte, NC, USA) after the IPR, group 4 (Icon) resin infiltration material (Icon Proximal Mini Kit, DMG, Bielefeld, Germany) was applied after IPR, group 5 (MI varnish) specimens were treated with Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) containing varnish (MI Varnish, G.C, USA, St. Alsip, IL, USA) after the IPR. The specimens in (groups 2-5) were stored in a 4.5 pH demineralization solution for 4 days. The trans-micro-radiography (TMR) technique was conducted to evaluate the mineral loss (∆Z) and lesion depth of all specimens after the acid challenge. The obtained results were analyzed statistically using a one-way ANOVA at a significance level of α = 0.05. RESULTS: The MI varnish recorded significant ∆Z and lesion depth values compared to the other groups p > 0.05. There was no significant difference in ∆Z and lesion depth between the control demineralized, Icon, and fluoride groups p < 0.05. CONCLUSION: The MI varnish increased the enamel resistance to acidic attack, and thus can be considered an agent capable of protecting the proximal enamel surface after IPR.

Incremental lines in human cellular cementum: A histological study.

OBJECTIVES: Human cellular cementum has incremental lines that demarcate individual cementum lamellae. The structural and functional details of the lines remain poorly understood. This study was designed to examine human cellular cementum using light microscopy, scanning electron microscopy, and contact microradiography and to elucidate the ultrastructure of incremental lines and their significance in cellular cementogenesis. METHODS: Longitudinal paraffin and ground sections of human mandibular molars were prepared. Paraffin sections were stained with hematoxylin, or hematoxylin and eosin, or impregnated with silver. Hematoxylin-stained sections were observed via scanning electron microscopy using NaOH maceration. Silver-impregnated sections were further stained with hematoxylin. Hematoxylin-stained ground sections were examined using contact microradiography. RESULTS: The incremental lines were found to be collagen fibril-poor layers. The outer area of each cementum lamella consisted of highly mineralized fibrils involved in constructing an alternating lamellar structure, whereas the inner area consisted of irregularly arranged, less highly mineralized, fibrils. The incremental lines corresponded with the innermost sites of the inner area. CONCLUSIONS: Based on the obtained findings, we suggest that cellular cementogenesis progresses as follows. (1) Cementoblasts alternate between low-to high-activity states. (2) In the earliest low-activity stage, cementoblasts generate poorly mineralized, fibril-poor, incremental lines. (3) As cementoblasts recover activity, fibril-organization and mineralization advance in the cementum. (4) In the high-activity stage, cementoblasts reach full activity and construct the highly mineralized, alternating lamellar structure. (5) Cementoblasts revert back to the low-activity stage. (6) The above processes are repeated, thus, alternately generating the incremental lines and cementum lamellae.

Effects of silver diamine fluoride on demineralization protection after a secondary acid challenge

Abstract Objective This investigation describes the effects of 5% sodium fluoride varnish and 38% silver diamine fluoride on demineralization protection of human enamel lesions of three different severities after a secondary acid challenge. Study design Specimens underwent color and enamel surface microhardness change measurements after demineralization and treatment events. Transverse microradiography was conducted following the secondary demineralization. Results After treatments, enamel surface microhardness change showed that 24-hour lesions treated with fluoride varnish had less rehardening than 24-hour lesions treated with silver diamine fluoride (p<0.05), whereas 144-hour lesions from both treatment groups showed a beneficial decrease in surface microhardness change that was markedly better in samples treated with silver diamine fluoride (p<0.05). After the secondary demineralization, 24- and 144-hour lesions treated with silver diamine fluoride showed a sustained beneficial decrease in enamel surface microhardness change when compared to fluoride varnish-treated samples of the corresponding lesion severity (p<0.05). Transverse microradiography showed no difference between fluoride varnish- and silver diamine fluoride-treated samples of any corresponding lesion severity, indicating that remineralization in both fluoride varnish- and silver diamine fluoride-treated samples was proportional to each other after a secondary acid challenge. Conclusions Using silver diamine fluoride may have comparable benefits to fluoride varnish in mineral loss prevention.

Development of Root Caries Prevention by Nano-Hydroxyapatite Coating and Improvement of Dentin Acid Resistance.

There is no established method for optimizing the use of dentin to prevent root caries, which are increasing in the elderly population. This study aimed to develop a new approach for root caries prevention by focusing on bioapatite (BioHap), a new biomaterial, combined with fluoride. Bovine dentin was used as a sample, and an acid challenge was performed in three groups: no fluoride (control group), acidulated phosphate fluoride treatment (APF group), and BioHap + APF treatment (BioHap group). After applying the new compound, the acid resistance of dentin was compared with that of APF alone. The BioHap group had fewer defects and an increased surface hardness than the APF group. The BioHap group had the smallest lesion depth and least mineral loss among all groups. Using a scanning electron microscope in the BioHap group showed the closure of dentinal tubules and a coating on the surface. The BioHap group maintained a coating and had higher acid resistance than the APF group. The coating prevents acid penetration, and the small particle size of BioHap and its excellent reactivity with fluoride are thought to have contributed to the improvement of acid resistance in dentin. Topical fluoride application using BioHap protects against root caries.

Evaluation of the mineral-promoting effects of in-office bleaching on experimental subsurface enamel lesions.

The aim of this study was to investigate the mineral-promoting effects of in-office bleaching agent on enamel subsurface lesions. Enamel subsurface lesions were divided into following groups; D: demineralized samples without any further treatment, DS: samples were further immersed in fresh saliva, DSR: samples were immersed in saliva followed by remineralization buffer, and DSBR: samples were immersed in saliva, subjected to in-office bleaching, and then immersed in remineralization buffer. The control group (CONT) consisted of untreated enamel specimens. Transverse microradiography showed that integrated mineral loss was significantly lower in the DSBR group than in the DSR group. Confocal laser Raman analysis revealed that ν1 phosphate peak height of 959 cm-1 and mineral to matrix ratio of peak heights 959 cm-1 to 1,610 cm-1 in the DSBR group were similar to those in the CONT. In-office bleaching can promote enamel remineralization by altering or removing proteins infiltrated to enamel subsurface lesions.

Preventing and Arresting Primary Tooth Enamel Lesions Using Self- Assembling Peptide P11-4 In Vitro.

Objectives: To evaluate self-assembling peptides (SAP) for caries prevention and arrest in primary tooth enamel in vitro. Materials and Methods: Overall, 180 extracted primary teeth were used. In the prevention experiment (n = 20 samples per group), self-assembling peptide for prevention (SAPP), fluoride varnish/mouthwash (FV/FMW), casein-phosphopeptide amorphous-calcium phosphate (CPP-ACP), and nanohydroxyapatite (nHA) were applied. Samples were subjected to a demineralizing pH cycling for 14 days. In the arrest experiment (n = 15/group), 60 samples were pre-demineralized; induced lesions were treated using self-assembling peptide for repair (SAPR), FV, CPP-ACP plus fluoride, and resin infiltration (RI) and submitted to pH cycling. Mineral loss and its differences as well as lesion depth were determined using transversal microradiography. Numerical data were tested for normality using Shapiro-Wilk's test and were compared using Kruskal-Wallis test followed by pairwise comparisons utilizing multiple Mann-Whitney U tests with Bonferroni correction. The significance level was set at P < 0.05 within all tests. Results: FV (median: -46.3 [interquartile range: 175.52] vol% × µm) and FMW (-33.35 [124.65] vol% × µm) prevented caries significantly more effectively than all other groups (P < 0.001), which did not show significant preventive effects. RI (median: 4949.70 [1637.20] vol% × µm) and FV (median = 6076.05 [5190.08] vol% × µm) arrested lesions, whereas SAPR and CPP-ACPF did not show such arrest. Conclusions: FV and FMW showed the largest caries-preventive effect, whereas RI and FV arrested lesion progression in primary tooth enamel in vitro.

The impact of glass ionomer cement and composite resin on microscale pH in cariogenic biofilms and demineralization of dental tissues.

OBJECTIVE: Secondary caries is among the most frequent reasons for the failure of dental restorations. Glass ionomer cement (GIC) restorations have been proposed to protect the surrounding dental tissues from demineralization through the release of fluoride and by buffering the acid attack from dental biofilms. In contrast, the lack of buffering by composite resin (CR) restorations has been suggested as a promoting factor for the development of secondary caries. METHODS: The present study employed transversal microradiography and confocal microscopy based pH ratiometry to quantify mineral loss and map microscale pH gradients inside Streptococcus mutans biofilms grown on compound specimens consisting of enamel, dentin and either GIC or CR. RESULTS: Mineral loss in dentin was significantly lower next to GIC than next to CR, but no significant differences in local biofilm pH were observed between the two restorative materials. SIGNIFICANCE: The cariostatic effect of GIC relies predominantly on the provision of fluoride and not on a direct buffering action. The lack of buffering by CR did not affect local biofilm pH and may therefore be of minor importance for secondary caries development.

Effects of desensitizer containing fluoroaluminocalciumsilicate glass nanoparticles on remineralization of root dentin subsurface lesions in vitro.

We investigated the remineralization effects of Nanoseal (NS) dentin desensitizer on demineralized root dentin. Baseline lesion specimens prepared from bovine root dentin were immersed in artificial saliva (AS) or deionized water (DW) after treatment with NS or fluoride-free Nanoseal (NS(-)). Treatment and control groups comprised: 1, AS; 2, NS/AS; 3, NS(-)/AS; 4,NS/DW; 5, NS(-)/DW; and 6, baseline demineralization. Integrated mineral loss (IML) and lesion depth (LD) were determined by transverse microradiography. Fluoride concentrations in the immersion solutions were measured. AS, NS/AS and NS(-)/AS showed higher mineral volume % at the surface and lesion body than did other groups. NS/AS showed significantly lower IML than did AS. There was no significant difference in IML between NS/AS and NS(-)/AS. The highest concentration of fluoride was in the NS/AS immersion solution. The findings suggest Nanoseal facilitated remineralization of demineralized root dentin, and fluoride and other ions included may have contributed to this effect.

Indirect caries-preventive effect of silver diamine fluoride on adjacent dental substrate: A single-section demineralization study.

This study assessed the indirect effect of 38% silver diamine fluoride (SDF) on demineralization of adjacent untreated sound and pre-demineralized enamel and dentine using a single-section model for digital transverse microradiography (TMR-D). Forty-eight bovine dentine single sections were demineralized, stratified (n = 12) according to integrated mineral loss (ΔZ), and treated with SDF or deionized water (DIW). Each "treated dentine" section was attached between untreated sound and pre-demineralized enamel or dentine and then subjected to demineralization. ΔZ and lesion depths (LD) of all specimens at baseline, 24 and 48 h demineralization, and after treatment of "treated dentine" were quantified using TMR-D. Fluoride in the demineralization solution of SDF clusters was determined using an ion-selective electrode. ΔZ and LD of sound and ΔZ of pre-demineralized enamel adjacent to SDF-treated dentine did not increase over time. All untreated dentine demineralized significantly; however, ΔZ of sound dentine adjacent to SDF-treated specimen was still significantly lower than control. SDF-treated dentine remineralized and released fluoride even after 48 h. Consistent with clinical findings, when applied only to demineralized teeth in this chemical model, 38% SDF completely inhibited demineralization in adjacent untreated sound enamel. Demineralization prevention was observed to a lesser extent in adjacent pre-demineralized enamel but not in dentine.

Artificial Caries Lesion Characteristics after Secondary Demineralization with Theobromine-Containing Protocol.

Developing artificial caries lesions with varying characteristics is needed to adequately study caries process in vitro. The objective of this study was to investigate artificial caries lesion characteristics after secondary demineralization protocol containing theobromine and fluoride. Sixty bovine enamel slabs (4 × 3 mm) were demineralized using a Carbopol-containing protocol for 6 days. A baseline area (2 × 3 mm) was protected with acid-resistant nail varnish, after which specimens were exposed for 24 h to a secondary demineralization protocol containing acetic acid plus one of four fluoride/theobromine combinations (n = 15): theobromine (50 or 200 ppm) and fluoride (0 or 1 ppm). Specimens were sectioned and analyzed using transverse microradiography for changes in mineral content, lesion depth, and surface layer mineralization. Data was analyzed using paired t-test and analysis of variance followed by Bonferroni test at 0.05 significance level. After secondary demineralization, fluoride-containing groups had significantly deeper lesions (p = 0.002 and 0.014) compared to the group with 0 ppm fluoride and 50 ppm theobromine. Mineral content and lesion depth were significantly different compared to baseline for all groups. Theobromine did not show an added effect on mineral uptake. Theobromine-containing groups exhibited particularly deep lesions with a more uniform mineral profile in the presence of fluoride.

Antimicrobial and anti-caries effects of a novel cystatin from sugarcane on saliva-derived multi-species biofilms.

This study evaluated the antimicrobial (anti-biofilm) and anti-caries (enamel demineralization prevention) effects of a new cystatin derived from sugarcane (CaneCPI-5). Microcosm biofilm was produced on bovine enamel specimens (4 x 4 mm; n=48) from a mixture of human saliva and McBain saliva at the first 8 h. From this moment until the end of the experiment, the enamel specimens were exposed to lsaMcBain saliva containing 0.2% sucrose and, once a day, they were treated with the test solutions for 1 min. This treatment was performed for 5 days. The solutions evaluated were: PBS (negative control), 0.12% chlorhexidine (positive control), 0.1 mg/ml CaneCPI-5 and 1.0 mg/ml CaneCPI-5. The biofilm viability was determined by fluorescence using confocal microscopy and the enamel demineralization was quantified using transverse microradiography (TMR). The data were analyzed by ANOVA/Tukey or Kruskal-Wallis/Dunn tests for biofilm and enamel, respectively (p<0.05). With respect to the antimicrobial effect, all treatment solutions significantly reduced the biofilm viability compared with PBS. The best antimicrobial effect was found for 1.0 mg/ml CaneCPI-5 (82.37±10.01% dead bacteria) that significantly differed from 0.12% chlorhexidine (73.13±15.07% dead bacteria). For the anti-caries effect, only 0.12% chlorhexidine (ΔZ: 2610, 1683-4343) performed significantly better than PBS (ΔZ: 8030, 7213-9115), but 0.12% chlorhexidine did not significantly differ from 0.1 mg/ml Cane-CPI-5. Under this experimental model, CaneCPI-5 significantly reduced the biofilm viability, but this effect was not reflected on its anti-caries potential.

Anti-demineralization characteristics of surface pre-reacted glass-ionomer (S-PRG) filler-containing varnishes.

This study investigated the anti-demineralization effects of surface pre-reacted glass-ionomer (S-PRG) filler-containing varnishes. Thirty-five bovine root specimens were divided into five treatment groups, with seven specimens each coated with 1) MI varnish (MIV), 2) F varnish (FV), 3) PRG varnish I (PV), 4) PRG varnish II (with sodium fluoride added, PVF), and 5) acid-resistant nail varnish (Control). A 3×1 mm area of the dentin surface adjacent to each varnish was demineralized for one week at 37°C. Integrated mineral loss (IML) of these lesions was determined by transverse microradiography, as was the amount of fluoride released by each material. IML was significantly lower in the PV and PVF groups than in the Control group, and was significantly lower in the PVF than in the MIV and FV groups. These findings indicated that S-PRG filler-containing varnishes, especially varnish containing sodium fluoride, had superior anti-demineralization effects on root dentin.

In vitro demineralization prevention by fluoride and silver nanoparticles when applied to sound enamel and enamel caries-like lesions of varying severities.

OBJECTIVES: To investigate the effect of fluoride and silver nanoparticles on the prevention of in vitro demineralization of sound enamel and enamel caries-like lesions of varying severities. METHODS: Caries-like lesions of different severities (1/6/15 days) were created in bovine enamel specimens. One group remained sound. All specimens were demineralized again using a partially saturated acetic acid solution. Mimicking the intra-oral retention of fluoride and silver in vitro, this solution was supplemented with fluoride (0/1/10 ppm) and/or silver nanoparticles (0/10 ppm) in a factorial design. Changes in lesion depth (ΔL) and integrated mineral loss (ΔΔZ) were evaluated by digital transverse microradiography. Data was analyzed using three-way ANOVA. RESULTS: Lesion severity significantly affected ΔΔZ and ΔL, after no treatment and after the treatment of fluoride and silver independently (p = 0.012 and p = 0.037, respectively). Fluoride and the fluoride × lesion severity interaction were shown to be significant (p < 0.001) on ΔΔZ and ΔL. Silver nanoparticles significantly affected ΔΔZ (p = 0.041), but not ΔL (p = 0.15). The silver nanoparticles × lesion severity interaction was significant for ΔΔZ and ΔL (p = 0.032 and p = 0.024, respectively). No interaction was observed for ΔΔZ and ΔL between fluoride and silver (p = 0.962 and p = 0.971, respectively) as well as lesion severity and the use of fluoride and silver combined (p = 0.722 and p = 0.158, respectively). CONCLUSION: Fluoride and silver nanoparticles had a significant effect on the prevention of in vitro demineralization of sound enamel and enamel caries-like lesions of varying severities. CLINICAL SIGNIFICANCE: Fluoride and silver nanoparticles may potentially allow for more tailored caries prevention.

Probiotic Effects on Multispecies Biofilm Composition, Architecture, and Caries Activity In Vitro.

While probiotics have been tested for their anti-caries effect in vitro and also clinically, there is a lack of understanding of their effects on complex dental biofilms. We assessed two probiotics, Lactobacillus reuteri and Streptococcus oligofermentans, on a continuous-cultured model containing Streptococcus mutans, Lactobacillus rhamnosus and Actinomyces naeslundii. Cariogenic biofilms were grown on bovine enamel specimens and daily challenged with L. reuteri or S. oligofermentans whole culture (LC/SC) or cell-free supernatant (LS/SS) or medium only (negative control, NC) (n = 21/group) for 10 days. Biofilm was assessed via counting colony-forming units, quantitative polymerase chain reaction, and fluorescence in situ hybridization. Caries activity was determined by pH measurements and by assessing mineral loss (ΔZ) using transverse microradiography. Both LC and SC significantly reduced total and strain-specific cariogenic bacterial numbers (p < 0.05). ΔZ was reduced in LC (mean ± SD: 1846.67 ± 317.89) and SC (3315.87 ± 617.30) compared to NC (4681.48 ± 495.18, p < 0.05). No significant reductions in bacterial numbers and ΔZ was induced by supernatants. Biofilm architecture was not considerably affected by probiotic applications. Viable probiotics L. reuteri and S. oligofermentans, but not their culture supernatants, could reduce the caries activity of multi-species biofilms in vitro.

Remineralization effects of conventional and experimental ion-releasing materials in chemically or bacterially-induced dentin caries lesions.

OBJECTIVES: The aim of this study was to evaluate the remineralization effects of conventional and experimental ion-releasing materials on different artificial dentin carious lesions. METHODS: Forty human dentin discs were submitted to different demineralization protocols for simulated caries lesion: (D1) Shallow chemically-induced caries, (D2) deep chemically-induced caries, (D3) deep bacterially-induced caries. Each disc was divided in five parts; one of those served as baseline control. The remaining parts of each disc (n=12-16/group) were treated using the following materials: EXP, an experimental resin-based bioactive material consisting of a self-etch primer and an adhesive containing a fluoride-doped bioglass; GIC, a glass ionomer cement (Riva LC); MTA, Mineral Trioxide Aggregate (ProRoot MTA); BIO, a calcium silicate cement (Biodentine). Specimens were mounted in a dual-chamber device to simulate the exposure to pulpal pressure and oral fluids. After 3 months, mineral and mechanical gains were assessed using transverse microradiography (vol% × µm) and microhardness measurements (VHN). Characterization using confocal microscopy and transmission electron microscopy (TEM) was also performed. RESULTS: All four restorative materials induced mineral gains regardless of the protocol for caries lesion, without significant differences between materials. Microhardness significantly increased in the groups BIO and MTA, but not GIC; EXP only provided hardness gains in D3-lesions. Fluorescence and confocal microscopy confirmed these results. There was a clear "top-down" remineralization in the groups BIO and MTA, and "bottom-up" intrafibrillar collagen remineralization in EXP. SIGNIFICANCE: Mineral gains did not always translate into hardness gains. Biodentine and MTA induced evident mineral precipitation, but intra/inter-fibrillar collagen mineral infiltration was only provided by biomimetic remineralisation via the use of the experimental adhesive. Complete remineralization of caries lesions remains a challenge.

Bleaching of simulated stained-remineralized caries lesions in vitro.

OBJECTIVE: Non-invasive esthetic treatment options for stained arrested caries lesions have not been explored. This study aimed to develop laboratory models to create stained-remineralized caries-like lesions (s-RCLs) and to test the efficacy of bleaching on their esthetic treatment. MATERIALS AND METHODS: One hundred twelve enamel/dentin specimens were prepared from human molars, embedded, and had their color measured spectrophotometrically at baseline and after demineralization. They were randomly divided into four groups (n = 14) based on the staining/remineralization protocols for a total of 5 days: G1, no staining/no remineralization; G2, no staining/remineralization in artificial saliva (AS); G3, non-metallic staining/remineralization with sodium fluoride/AS; and G4, metallic staining/remineralization with silver diamine fluoride/AS. The lesion mineral loss (ΔZ) and depth (L) were measured using transverse microradiography along with color change (ΔE). Specimens were bleached and color was re-evaluated. Data were analyzed using ANOVA models followed by Fisher's PLSD tests (α = 0.05). RESULTS: s-RCLs in G4 were significantly (p < 0.001) darker than G3, G2, and G1 regardless of substrate type and condition. s-RCLs in G2, G3, and G4 showed significantly lower ΔZ and L than G1 (all p < 0.001), confirming occurrence of remineralization. G4 exhibited significantly lower ΔZ and L compared to G2 (p < 0.001). Bleaching was more effective in non-metallic than in metallic stained lesions regardless of substrate type (p < 0.001). CONCLUSION: The proposed models created distinct s-RCLs. Non-metallic s-RCLs were lighter and more responsive to bleaching compared to metallic s-RCLs. CLINICAL RELEVANCE: The developed experimental models allow the further investigation of the efficacy and safety of different clinical strategies for the esthetic management of s-RCLs.