Inhibition of mineral loss at the enamel/sealant interface of fissures sealed with fluoride- and non-fluoride containing dental materials in vitro

OBJECTIVE: In this in vitro study we evaluated the enamel mineral loss effect of fluoride-containing and non-fluoride-containing materials at different distances from the sealant margin, and verified the fluoride-releasing capability of these materials. MATERIAL AND METHODS: Extracted molars were randomly assigned into nine groups (n = 12): Concise (C), FluroShield (F), Helioseal Clear Chroma (H), Vitremer (V), Fuji II-LC (FII), Ketac Molar (KM), Fuji IX (FIX), Single Bond (SB), and Clearfil Protect Bond (CF). All groups were subjected to thermo and pH cycling. Enamel mineral loss was evaluated by cross-section micro-hardness analysis at distances: -100 microm, 0 microm, 100 microm, 200 microm. The mineral loss data were analyzed using a multi-factor ANOVA with split-plot design, and fluoride-released data were submitted to ANOVA and Tukey tests. RESULTS: FIX demonstrated a lower mineral loss than C, F, and H, but did not differ from the SB, CF, V, FII, and KM groups, which also demonstrated no difference among them. C, F, H, and V presented the highest mineral loss, with no difference among them. V did not differ from the other groups (p > 0.05). Regarding the different distances from the sealant margin, -100 microm presented the lowest mineral loss. FIX showed the highest fluoride release on the 7th and 14th days of evaluation, while CF showed high fluoride release only on the 7th day. CONCLUSION: Resin sealant did not prevent enamel mineral loss, contrary to glass-ionomer cement, which showed the highest capacity for fluoride release. It is not exclusively the presence of fluoride in a material's composition that indicates its capability to interfere with the development of enamel caries-like lesions.     

Inhibition of enamel mineral loss by fissure sealant: An in situ study

ObjectivesThis study evaluated the effect of fluoride and non-fluoride sealants on hardness decrease (HD) and marginal adaptation (MA) on enamel substrates after cariogenic challenge.MethodsOcclusal enamel blocks, from human third molars, were randomly divided into six groups (n = 12), according to occlusal fissures condition (S – sound; C – caries-like lesion; CF – caries-like lesion + topical fluoride) and sealants (F – FluroShield; H – Helioseal Clear Chroma). Lesion depths were 79.3 ± 33.9 and 61.3 ± 23.9 for C and CF groups, respectively. Sealants were placed on occlusal surface and stored at 100% humidity (37 °C; 24 h/d). HD was measured by cross-sectional microhardness analysis at the sealant margin distances: ?1 (under sealant), 0 (sealant margin), 1, 2 (outer sealant). Sealant MA was observed by polarized light microscopy and scored according to: 0 – failure (no sealant MA or total sealant loss); 1 – success (sealant MA present). MA and HD were analysed by ANOVA-R and mixed model analysis, respectively.ResultsFor HD (ΔS), F values (6900.5 ± 3686.6) were significantly lower than H values (8534.6 ± 5375.3) regardless of enamel substrates and sealant margin distances. Significant differences were observed among sealant margin distances: ?1 (5934.0 ± 3282.6) < 0 (8701.5 ± 6175.7) = 1 (8473.2 ± 4299.4) = 2 (7761.5 ± 4035.1), regardless of sealant and substrate. MA was similar for all groups (p ≥ 0.05).ConclusionMA was not affected by sealant type or substrate condition, whereas enamel HD was favourably impacted by fluoride in the sealant. In addition, sealants were more effective as a physical barrier than as its chemical potency in reducing enamel HD.Clinical significanceSealing with a fluoride material is a recommended procedure to prevent caries of occlusal permanent molars in high-caries-risk patients, even though those exhibiting white spot lesions, since the enamel hardness decrease when fluoride sealant was used in vitro.     

Effect of home-bleaching gels modified by calcium and/or fluoride and the application of nano-hydroxyapatite paste on in vitro enamel erosion susceptibility

Objective. This in vitro study compared the effect of bleaching agents modified by the addition of calcium and/or fluoride and the application of a nano-hydroxyapatite paste after bleaching, on the susceptibility of enamel to erosion. Materials and methods. Bovine enamel cylindrical samples (3 mm diameter) were assigned to six groups (n = 20 specimens/group) according to the bleaching agent: no bleaching (C-control), 7.5% hydrogen peroxide gel (HP), HP with 0.5% calcium gluconate (HP+Ca), HP with 0.2% sodium fluoride (HP+F), HP with calcium and fluoride (HP+Ca+F) and HP followed by the application of a nano-hydroxyapatite agent (HP+NanoP). The gels were applied on the enamel surface (1 h) followed by cyclic erosive challenges (Sprite Zero®-2 min), for 14 days. The paste was applied after bleaching for 5 min (HP+NanoP). The enamel surface alteration was measured by contact profilometry (µm) (after 7 and 14 days). Results. C-control (mean ± SD: 2.29 ± 0.37 at 7 days/4.86 ± 0.72 at 14 days) showed significantly lower loss compared to the experimental groups. HP+Ca (3.34 ± 0.37/6.75 ± 1.09) and HP+F (4.49 ± 0.92/7.61 ± 0.90) presented significantly lower enamel loss than HP (4.18 ± 0.50/10.30 ± 1.58) only for 14 days and HP+Ca+F (4.92 ± 1.03/8.12 ± 1.52) showed values similar to the HP+F group. The HP+NanoP (5.51 ± 1.04/9.61 ± 1.21) resulted in enamel loss similar to the HP after 14 days. Conclusions. It was found that 7.5% hydrogen peroxide increased the susceptibility of enamel to erosion. The addition of calcium or fluoride to the bleaching gel reduced the erosion effect, while the nano-hydroxyapatite agent did not provide any protective effect.     

Fluoride toothpastes containing micrometric or nano-sized sodium trimetaphosphate reduce enamel erosion in vitro

Objective: To evaluate the effect of fluoride toothpastes supplemented with micrometric or nano-sized sodium trimetaphosphate (TMP or TMPnano, respectively) on enamel erosion in vitro, as well as the influence of salivary acquired pellicle and saliva.

Material and methods: Bovine enamel blocks (n?=?120) were randomly assigned into the following experimental toothpastes: no F/TMP/TMPnano (Placebo); 1100?ppm F (1100?ppm F); 1100?ppm F plus 3% TMP or 3% TMPnano (1100 TMP or 1100 TMPnano, respectively) and 5000?ppm F (5000?ppm F). Erosive challenge was performed by immersion of the blocks in citric acid for 5?min, followed by 2?h immersion in human or artificial saliva, 4×/day, during 5 days. After each erosive challenge, blocks were exposed to slurries of the toothpastes. Enamel erosion (µm), surface hardness (SHf) and cross-sectional hardness (ΔKHN) were analyzed as response variables and the data were submitted to two-way ANOVA, followed by the Student–Newman–Keuls test (p?Results: 1100 TMPnano significantly reduced enamel loss when compared to 1100 TMP (p?=?.002), reaching values similar to those promoted by 5000?ppm F (p?=?.96). 1100?ppm F presented significantly lower enamel loss than Placebo (p?p?p?Conclusion: The addition of 3% TMPnano to 1100?ppm F toothpastes significantly increases the protective effect against enamel erosion in vitro when compared with its counterparts with micrometric TMP or without TMP. This effect was not influenced by the presence of acquired enamel pellicle and saliva.     

Adjunctive use of fluoride rinsing and brush-on gel increased incipient caries-like lesion remineralization compared with fluoride toothpaste alone in situ

Objective: The objective of this study was to compare the remineralizing effect of sodium fluoride (NaF) mouth rinse or NaF gel as an adjunct to NaF dentifrice on incipient caries-like lesions in an in situ cross-over design study, with three sessions of 30 days each.

Materials and methods: Orthodontic brackets with artificial demineralized enamel slabs were attached to the upper first molars of 12 participants. A set of 3 test specimens from the same tooth was randomly assigned to each participant and allocated into three 30-day sessions: 1) brushing with 0.22% NaF dentifrice 2 times/day (F dentifrice), 2) brushing with 0.22% NaF dentifrice 2 times/day+?rinsing with 0.05% NaF before bedtime (F mouth rinse), 3) brushing with 0.22% NaF dentifrice 2 times/day?+?brushing with 1.1% NaF gel before bedtime (F brush-on gel). The mineral gain and lesion depth of the specimens were evaluated by micro-computed tomography.

Results: The mean mineral gain from the NaF mouth rinse and the NaF brush-on gel was similar, but greater than that from the NaF dentifrice (p?p?Conclusions: Both 0.05% NaF mouth rinse and 1.1% NaF brush-on gel, used at bedtime, increased incipient caries-like lesion remineralization in situ in combination with brushing with NaF dentifrice twice a day.     

Sodium trimetaphosphate enhances the effect of 250 p.p.m. fluoride toothpaste against enamel demineralization in vitro

This in vitro study investigated the effect of sodium trimetaphosphate (TMP), added to toothpaste containing 250 p.p.m. fluoride, on enamel demineralization. Bovine enamel blocks (n = 96) were subjected to five pH cycles over a 7‐d period and treatment with suspensions of toothpastes containing 0, 250, 500, and 1,100 p.p.m. fluoride (as sodium fluoride), as well as with 250 p.p.m. fluoride containing TMP at 0.25, 0.5, 1.0, and 3.0%. Treatment with toothpaste suspensions was performed under agitation twice a day, for 1 min. Surface and cross‐sectional hardness, and fluoride firmly bound to enamel, were quantified. Data were subjected to one‐way anova , followed by Tukey's test. Low‐fluoride toothpastes containing TMP at 0.25–1.0% resulted in enamel mineral loss similar to that seen for the toothpaste containing 1,100 p.p.m. fluoride. Also, the addition of TMP to the toothpaste containing 250 p.p.m. fluoride promoted enamel fluoride concentrations similar to those obtained for the 500 p.p.m. fluoride group. The toothpaste containing 250 p.p.m. fluoride and 0.25% TMP led to the lowest mineral loss among all groups. It was concluded that the addition of as little as 0.25% TMP to a toothpaste containing 250 p.p.m. fluoride can reduce enamel demineralization to levels similar to those seen for a conventional toothpaste containing 1,100 p.p.m. fluoride, in vitro.     

An alkasite restorative material effectively remineralized artificial interproximal enamel caries in vitro

Objective

To evaluate the remineralization of artificial interproximal enamel caries (AIEC) adjacent to alkasite, high viscous glass ionomer cement (HVGIC), and resin composite in class II restorations.

Materials and methods

Human enamel specimens were randomly assigned to 3 groups (n?=?22): Filtek? Z350, EQUIA Forte^®, and Cention N^®. The baseline hardness was determined using a Knoop microhardness assay. AIEC was formed in the specimens, and they were placed in contact with the proximal restorative materials then subjected to a 7-day pH cycling. Microhardness was determined post-artificial caries formation and post-pH cycling. The differences in the percentage of surface hardness recovery (%SHR) between the groups were compared using the Kruskal–Wallis test. The Dunn’s test was used for between-group comparisons (p?<?0.05). Specimen surface morphology was evaluated using scanning electron microscopy (SEM), and the calcium, phosphorus, and fluoride contents were analyzed by energy-dispersive spectroscopy (EDS). ANOVA with the post hoc Tukey multiple comparison test was used to evaluate the differences between groups (p?<?0.05).

Results

The Cention N^® %SHR was the highest, followed by EQUIA Forte^®, and Filtek? Z350. There was a significant difference in the %SHR between Cention N^® and Filtek? Z350 (p?<?0.05). In contrast, there were no significant difference between Cention N^® and EQUIA Forte^®. Significantly increased enamel surface fluoride content was observed in the Cention N^® compared with Filtek? Z350 specimens (p?<?0.05). The SEM image of the Cention N^® specimens demonstrated the greatest mineral deposition.

Conclusions

Cention N^® markedly increased the surface hardness and fluoride content of adjacent AIEC compared with Filtek? Z350 restorations.

Clinical relevance

Cention N^® is a promising alternative restorative material to remineralize initial enamel lesions in approximal adjacent surfaces, especially in high-risk caries patients.

     

A 2-year clinical evaluation of sealed noncavitated approximal posterior carious lesions in adolescents

The objective was to evaluate the clinical performance of a therapeutic sealant to arrest the progression of noncavitated approximal posterior carious lesions. The study population comprised 50 adolescents in whom bitewing radiographs had been taken for diagnosis of caries. Approximal noncavitated lesions in premolars and molars (4d–7m) were selected. One group (n=17) had a sealant placed after tooth separation on all enamel lesions. A second group (n=7) received sealant and fluoride varnish in a split-mouth design. A control group (n=26) received a standard fluoride varnish treatment without tooth separation. Follow-up radiographs were taken after 2 years and were analyzed together with the baseline radiographs in a blind study setting. About 93% of the sealed initial carious lesions showed no progression. The corresponding value for the fluoride varnish control group was 88%. In the split-mouth study, 92 and 88% of the surfaces with enamel caries showed no progression after sealant or fluoride varnish treatment, respectively. The difference between the two treatment procedures was not statistically significant. The incidence rate for the transition from enamel caries to dentin caries or fillings was 3.5–3.9 surfaces/100 years in the sealant groups and 5.9–6.1 surfaces/100 years in the fluoride varnish groups. The results show the potential of sealants to act as a noninvasive treatment of early approximal enamel lesions.     

A randomised controlled trial to investigate the remineralising potential of Tooth Mousse™ in orthodontic patients

Objective: To investigate the remineralisation of enamel subsurface lesions treated with fluoride toothpaste (1450 ppm) or a combination of fluoride toothpaste in addition to Tooth Mousse?.

Design: An in situ, cross-over, randomised controlled trial.

Setting: Orthodontic department at Liverpool University Dental Hospital, UK. Participants: Twelve patients receiving fixed orthodontic treatment. Methods: Demineralised subsurface enamel lesions were placed in a carrier and attached onto a fixed orthodontic appliance. Interventions were either standard fluoride toothpaste or CPP-ACP paste (Tooth Mousse?) in addition to the fluoride toothpaste. Participants received both interventions in a randomised order. Transverse microradiography analysis was used to compare lesion mineral content profiles.

Results: Mineral loss was reduced by 15.4 and 24.6% between the fluoride and CPP-ACP groups, respectively (p = 0.023). Lesion depth was reduced by 1.6 and 11.1% between the fluoride and CPP-ACP groups, respectively (p = 0.037). Lesion width was reduced by 4.5 and 15.3% between the fluoride and CPP-ACP groups, respectively (p = 0.015).

Conclusions: Remineralisation occurred regardless of treatment group allocation. However, the addition of Tooth Mousse? resulted in a significantly increased remineralisation effect, compared to fluoride alone. Tooth Mousse? may be beneficial for patients undergoing orthodontic treatment who are at high risk of demineralisation.

Trial Registration: Registered on Current Control Trials http://www.controlled-trials.com/ISRCTN04899524     

Influence of prophylaxis paste treatment on the abrasive wear of surface sealants

Abstract

Objective. To investigate the abrasive wear of surface sealants (Seal&Protect and K-0184 (experimental sealant)) and the influence of pre-treatment with mineral deposit forming prophylaxis pastes (NUPRO Sensodyne and NUPRO) on this wear. Methods. One hundred and eight bovine dentine samples were randomly allocated to nine groups (1–9). Pre-treatment (10 s): groups 1–3: untreated, groups 4–6: NUPRO, groups 7–9: NUPRO Sensodyne. Sealing: groups 1, 4 and 7: unsealed, groups 2, 5 and 8: Seal&Protect, groups 3, 6 and 9: K-0184 (experimental sealer). Samples were then brushed with 12 000 brushing strokes (BS) with toothpaste slurry in an automatic brushing machine (120 BS/min; F = 2.5 N). Surface profiles were recorded at baseline, after pre-treatment and sealing and after each 2000 BS. Results. Total profile change (wear or gain due to pre-treatment, treatment and 12 000 BS): groups 1, 4 and 7 (no surface sealant) showed a not significantly different wear of 18.48 ± 2.63 µm, 24.98 ± 3.02 µm and 21.50 ± 5.47 µm, respectively. Remaining groups (sealed) showed a gain in height with no significant difference among each other. Wear in sealed groups (2, 3, 5, 6, 8 and 9) were not significantly different at all numbers of brushing strokes. Starting with 4000 BS, the wear in unsealed groups (1, 4 and 7) was statistically significantly higher compared to all other groups. Conclusion. Stability and wear resistance of surface sealants are not affected by pre-treatment of dentine with NUPRO Sensodyne. The surface sealants tested provide a stable protective surface layer on dentine, which lasts for at least 12 000 brushing strokes.     

Effect of pepsin on erosive tissue loss and the efficacy of fluoridation measures in dentine in vitro

Objectives. In dentine, erosive lesion progression and efficacy of fluoridation measures for symptomatic therapy of dental erosion are both dependent on the presence of the organic matrix. In patients with eating disorders in combination with chronic vomiting, the demineralized organic matrix can be degraded by gastric enzymes. The aim of this study was to investigate the effect of pepsin on erosion progression and the efficacy of fluoride in dentine. Material and methods. Human dentine specimens were prepared and randomly divided into 4 groups of 20 specimens each. They were subjected to a cyclic de- and remineralization procedure for 9 days. For demineralization (6×2 min per day), an HCl solution (pH 1.6) was used in all groups. In two groups, pepsin (1.5 mg mL^?1) was added to the demineralization solution. Fluoridation was performed in two groups 6×1 min per day with a mouth rinse (Olaflur/SnF₂; 250 ppm F^?) after demineralization with both the HCl solution and the pepsin containing solution. Degradation of collagen was quantified by analyzing hydroxyproline and tissue loss was determined microradiographically. SEM images were taken in addition. Results. In the pepsin group, 1.72 (0.26) µg mL^?1 (mean (SD)) hydroxyproline per day was detected, and in the pepsin-fluoride group 1.95 (0.50) µg mL^?1. Tissue loss after 9 days in the control group was similar to that in the pepsin group (122.2 (53.4) µm and 122.2 (38.0) µm, n.s., respectively). Fluoridation reduced tissue loss after demineralization (98.8 (30.2) µm) but not after pepsin treatment (125.2 (34.2) µm; p≤0.05). Conclusion. Under the conditions used, pepsin had no influence on tissue loss, but altered the efficacy of fluoridation measures.     

Fluoride varnishes containing sodium trimetaphosphate reduce enamel demineralization in vitro

Objective: This study evaluated the effects of fluoride varnishes containing sodium trimetaphosphate (TMP) on bovine enamel demineralization in vitro.

Material and methods: Enamel bovine discs were randomly assigned into six groups (n?=?20/group): placebo, 2.5% NaF, 2.5% NaF/5% TMP, 5% NaF, 5% NaF/5% TMP, and a commercial formulation (Duraphat, 5% NaF). Varnishes were applied on all enamel discs and kept for 6?h. Loosely and firmly bound fluoride formed on/in enamel after treatment were analyzed in 10 discs from each group. The other 10 discs were subjected to a pH-cycling regimen for 7 days, and analyzed for surface (SH) and cross-sectional hardness (ΔKHN), as well as for loosely and firmly bound fluoride in/on enamel. Data were analyzed by analysis of variance (ANOVA) followed by Student–Newman–Keuls’ test (p?Results: The lowest SH change and ΔKHN were observed for the 5%NaF/5%TMP varnish, which was significantly different from all the other groups. Both fluoridated varnishes containing TMP promoted significantly lower SH change and ΔKHN when compared with their counterparts without TMP. Loosely and firmly bound fluoride was significantly lower in groups treated with varnishes containing TMP.

Conclusion: TMP and fluoride added to varnishes have a synergistic effect against enamel demineralization in vitro.     

Effect of diode laser and fluoride varnish on initial surface demineralization of primary dentition enamel: an in vitro study

Summary. Introduction. Previous investigations have demonstrated improved enamel caries resistance after laser irradiation. The purpose of this in vitro study was to assess the caries‐preventive potential of 809 nm diode laser treatment of the enamel of primary teeth compared to topical fluoride application. Methods. Eighty samples of sound primary teeth were embedded in plastic and stored in saline solution. The enamel surface of 80 samples was polished in an area of 2 × 2 mm. These tooth specimens were randomly assigned to one control and three test groups: (1) no treatment/control; (2) application of 0·1 mg of fluoride varnish (Duraphat^®) for 6 h; (3) diode laser application (809 nm, 140 mJ, 50 Hz, Ø 600 µm fibre, contact mode, absorber, 1 min; ORA‐LASER01^® I.S.T.); and (4) combined application – laser/fluoride varnish. Caries‐like lesions were created by pH‐cycling. After lesion formation, longitudinal sections were taken and examined by polarized light microscopy. Results. In the control group, all samples showed lesions up to 30 µm in depth. After laser application, lesions could be identified in 15 out of 20 samples. Topical fluoride treatment in groups 2 (varnish) and 4 (laser/varnish) completely inhibited the development of caries‐like lesions in all samples. Conclusion. In this in vitro investigation, topical fluoride treatment enhances the resistance of sound enamel of primary teeth more effectively than diode laser application.     

Enamel erosion depths measured on impressions by a white light interferometer

Abstract

Objective. To investigate if measurements of the step heights on an impression of eroded enamel surfaces may give reliable values of the etching depths measured directly on the enamel. Materials and methods. Twelve human enamel specimens, with one circular amalgam reference surface in each, were mounted on an epoxy block and ground flat. Baseline images were taken by a White Light Interferometer (WLI) followed by 12 min etch by 0.01 M HCl, pH 2.2. The mean etch depth on each specimen was calculated from three repeated measurements, both on the specimen surfaces and on the silicone polymer impressions of the surfaces. Paired samples t-test was used when comparing the precision of measurements on enamel vs on impression. Results. The mean lesion depths after 12 min etch measured on the 12 enamel surfaces and impressions were 9.9 µm and 10.6 µm, respectively. The direct and indirect measurements correlated well (r ² = 0.95), with 7% higher mean etch depth measured on the impressions (p < 0.05). The reliability of three repeated measurements on enamel and impressions expressed by Intra Class Correlation (ICC) were 0.98 and 0.99, respectively. The average relative precisions of three repeated measurements on the 12 tooth and impression surfaces were (0.5 ± 0.1)% and (0.1 ± 0.02)%, respectively (p < 0.05). The accuracies were 0.4% and 7%, respectively. Conclusion. WLI gave reliable but slightly higher etch depth measurements on impressions compared to enamel surfaces.     

The threshold of an intra oral scanner to measure lesion depth on natural unpolished teeth

ObjectivesTo investigate the threshold and accuracy of intraoral scanning in measuring freeform human enamel surfaces.MethodsSoftware softgauges, ranging between 20 and 160 µm depth, were used to compare four workflow analysis techniques to measure step height on a freeform surface; with or without reference areas and in combination with surface-subtraction to establish which combination produced the most accurate outcome. Having established the optimum combination, 1.5 mm diameter, individual depths ranging from 11 to 81 µm were created separately on 14 unpolished human enamel samples and then scanned with gold standard laboratory optical profilometry (NCLP, TaiCaan Technologies?, XYRIS2000CL, UK) and a clinical intraoral scanner (TrueDefinition?, Midmark Corp., USA). The sequence of surface registration and subtraction determined from the softgauges was used to measure step height on natural human enamel surfaces. Step heights (μm) were compared using two-way ANOVA with post-hoc Bonferroni (p < 0.05) and Bland-Altman analyses.ResultsSoftware differences were significantly reduced from ? 29.7 to ? 32.5% without, to ? 2.4 to ? 3.6% with reference areas (p < 0.0001) and the addition of surface-subtraction after registration reduced this further to 0.0 to ? 0.3% (p < 0.0001). The intraoral scanner had a depth discrimination threshold of 73 µm on unpolished natural enamel and significant differences (p < 0.05) were observed compared to NCLP below this level.SignificanceThe workflow of combining surface-registration and subtraction of surface profiles taken from intraoral scans of freeform unpolished enamel enabled confident measurement of step height above 73 µm. The limits of the scanner is related to data capture and these results provide opportunities for clinical measurement.     

Anticaries effect of toothpaste with nano-sized sodium hexametaphosphate

Objective

To evaluate the effect of a fluoride toothpaste containing nano-sized sodium hexametaphosphate (HMPnano) on enamel demineralization on the biochemical composition and insoluble extracellular polysaccharide (EPS) in biofilm formed in situ.

Methods

This crossover double-blind study consisted of four phases (7 days each), in which 12 volunteers wore intraoral appliances containing four enamel bovine blocks. The cariogenic challenge was performed using 30% sucrose solution (6×/day). Blocks were treated 3×/day with the following toothpastes: no F/HMP/HMPnano (Placebo), conventional fluoride toothpaste, 1100 ppm F (1100F), 1100F + 0.5% micrometric HMP (1100F/HMP), and 1100F + 0.5% nano-sized HMP (1100F/HMPnano). The percentage of surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), and enamel calcium (Ca), phosphorus (P), and fluoride (F) were determined. Moreover, biofilms formed on the blocks were analyzed for F, Ca, P, and insoluble extracellular polysaccharide (EPS) concentrations. Data were analyzed using one-way ANOVA, followed by Student–Newman–Keuls’ test (p < 0.001).

Results

1100F/HMPnano promoted the lowest %SH and ΔKHN among all groups (p < 0.001). The addition of HMPnano to 1100F significantly increased Ca concentrations (p < 0.001). The 1100F/HMPnano promoted lower values of EPS when compared with 1100F (~ 70%) (p < 0.001) and higher values of fluoride and calcium in the biofilms (p < 0.001).

Conclusion

1100F/HMPnano demonstrated a greater protective effect against enamel demineralization and on the composition of biofilm in situ when compared to 1100F toothpaste.

Clinical relevance

This toothpaste could be a viable alternative to patients at high risk of caries.

     

Impact of combined CO2 laser irradiation and fluoride on enamel and dentin biofilm-induced mineral loss

Objectives

The caries-protective effects of CO₂ laser irradiation on dental enamel have been demonstrated using chemical demineralization models. We compared the effect of CO₂ laser irradiation, sodium fluoride, or both on biofilm-induced mineral loss (∆Z) and Streptococcus mutans adhesion to enamel and dentin in vitro.

Materials and methods

Ground, polished bovine enamel, and dentin samples were allocated to four groups (n = 12/group): no treatment (C); single 22,600-ppm fluoride (F) varnish (5 % NaF) application; single CO₂ laser treatment (L) with short pulses (5 μs/λ = 10.6 μm); and laser and subsequent fluoride treatment (LF). Samples were sterilized and submitted to an automated mono-species S. mutans biofilm model. Brain heart infusion plus 5 % sucrose medium was provided eight times daily, followed by rinses with artificial saliva. After 10 days, bacterial numbers in biofilms were enumerated as colony-forming units/ml (CFU/ml) (n = 7/group). ∆Z was assessed using transversal microradiography (n = 12/group). Univariate ANOVA with post hoc Tukey honestly-significant-difference test was used for statistical analysis.

Results

Bacterial numbers were significantly higher on dentin than enamel (p < 0.01/ANOVA). On dentin, LF yielded significantly lower CFUs than other groups (p = 0.03/Tukey), while no differences between groups were found for enamel. The lowest ∆Z in enamel was observed for L (mean/SD 2036/1353 vol%×μm), which was not only significantly lower than C (9642/2452 vol%×μm) and F (7713/1489 vol%×μm) (p < 0.05) but also not significantly different from LF (3135/2628 vol%×μm) (p > 0.05). In dentin, only LF (163/227) significantly reduced ∆Z (p < 0.05).

Conclusion/clinical relevance

CO₂ laser irradiation did not increase adhesion of S. mutans in vitro. Laser treatment alone protected enamel against biofilm-induced demineralization, while a combined laser-fluoride application was required to protect dentin.

     

The interplay of saliva,erosion and attrition on enamel and dentine

PurposeThis investigation aimed to compare the protective role of saliva against erosion and attrition challenges.MethodPolished enamel and dentine samples (n = 160) were prepared and randomly assigned to either the saliva or saliva-free group (n = 40 enamel and n = 40 dentine/group). Within each subgroup, they were allocated to four subgroups: negative control (deionized water exposure 10 min), erosion (0.3% citric acid 10 min), attrition (120 S of 300 g force), or combined erosion/attrition (0.3% citric acid 10 min then 120 S of 300 g force). Experimental cycles were repeated three times. Data analysis was performed using SPSS.ResultsThe mean and standard deviation (SD) of step heights produced by the attrition and erosion/attrition groups in enamel in the saliva-free group were 5.6 µm (2.4) and 13.4 µm (2.8), respectively, while they were 2.4 µm (3.8) and 12.9 µm (3.5) in the saliva group, with no significant difference between the saliva and saliva-free groups. For dentine, the corresponding step heights were 25.2 µm (5.5) and 35.9 µm (7.9) for the saliva-free group, but 21.8 µm (5.3) and 27.3 µm (6.4) for the saliva group (p < 0.001).ConclusionThere was a trend that saliva decreased wear, but this was only statistically significant for erosion/attrition dentine wear.     

Novel pit and fissure sealant containing nano-CaF2 and dimethylaminohexadecyl methacrylate with double benefits of fluoride release and antibacterial function

ObjectivePit and fissure sealants with antibacterial and remineralization properties have broad application prospects in caries prevention. The objectives of this study were to: (1) develop a novel pit and fissure sealant containing CaF₂ nanoparticles (nCaF₂) and dimethylaminohexadecyl methacrylate (DMAHDM); and (2) investigate the effects of nCaF₂ and DMAHDM on biofilm response and fluoride (F) ion release for the first time.MethodsHelioseal F was used as a control. Bioactive sealants were formulated with DMAHDM and nCaF₂. Flow properties, enamel shear bond strength, hardness and F ion releases were measured. Streptococcus mutans (S. mutans) biofilms were grown on sealants. Biofilm metabolic activity, lactic acid production, colony-forming units (CFU), and pH of biofilm culture medium were measured.ResultsAdding 5% DMAHDM and 20% nCaF₂ did not reduce the paste flow and enamel bond strength, compared to control (p < 0.05). Hardness of sealants with 20% nCaF₂ and DMAHDM was higher than control (p < 0.05). The F ion release from 20% nCaF₂ was much higher than that of commercial control (p < 0.05). The sealant with DMAHDM reduced the S. mutans biofilm CFU by 4 logs. The pH in biofilm medium of the new bioactive sealant was much higher (pH 6.8) than that of commercial sealant (pH 4.66) (p < 0.05).SignificanceThe new bioactive pit and fissure sealant with nCaF₂ and DMAHDM achieved high fluoride release and strong antibacterial performance. This novel fluoride-releasing and antibacterial sealant is promising to inhibit caries and promote the remineralizaton of enamel and dentin.     

Remineralization and acid resistance of enamel lesions after chewing gum containing fluoride extracted from green tea

Background: The aim of this study was to evaluate enamel remineralization and the acquisition of acid resistance by using sugar‐free chewing gum containing fluoride extracted from green tea. Methods: Forty‐five volunteers participated in a crossover, double‐blind study and wore intraoral appliances with human demineralized enamel. Subjects chewed fluoride chewing gum (FCG: 50 μg fluoride) or placebo gum. Remineralization and acid resistance were evaluated using the mineral change value (ΔZ, in vol%·μm). Fluoride concentrations in saliva and remineralized enamel were analysed. Results: The peak salivary fluoride concentration was 3.93 ± 1.28 ppm (mean ± SD). The elevated salivary fluoride concentration resulted in a higher fluoride concentration of 656 ± 95 ppm in the remineralized region versus 159 ± 26 ppm for placebo gum (p < 0.001). After remineralization, the ΔZ of the FCG group was higher than that of the placebo gum group. After an acid challenge, ΔZ of the FCG group was lower than the placebo gum group. Both ΔZ were statistically significant. Conclusions: FCG produced a superior level of remineralization and acid resistance, as compared to the placebo gum. The in situ results suggest that regular use of FCG is useful for preventing dental caries.