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Concept: Remineralisation of teeth

177

Human dental enamel, the hardest tissue in the body, plays a vital role in protecting teeth from wear as a result of daily grinding and chewing as well as from chemical attack. It is well established that the mechanical strength and fatigue resistance of dental enamel are derived from its hierarchical structure, which consists of periodically arranged bundles of hydroxyapatite (HAP) nanowires. However, we do not yet have a full understanding of the in vivo HAP crystallization process that leads to this structure. Mg(2+) ions, which are present in many biological systems, regulate HAP crystallization by stabilizing its precursor, amorphous calcium phosphate (ACP), but their atomic-scale distribution within HAP is unknown. We use atom probe tomography to provide the first direct observations of an intergranular Mg-rich ACP phase between the HAP nanowires in mature human dental enamel. We also observe Mg-rich elongated precipitates and pockets of organic material among the HAP nanowires. These observations support the postclassical theory of amelogenesis (that is, enamel formation) and suggest that decay occurs via dissolution of the intergranular phase. This information is also useful for the development of more accurate models to describe the mechanical behavior of teeth.

Concepts: Hierarchy, Solubility, Philosophy of science, Teeth, Crystallization, Tooth enamel, Nucleation, Remineralisation of teeth

28

Background:  Dentinal hypersensitivity has been defined as a short, sharp pain arising from exposed dentine as a result of various stimuli such as heat, cold, chemical, or osmotic, that cannot be ascribed to any other pathology. This study was conducted to assess the efficacy of three commercially available toothpastes in the reduction of dentinal hypersensitivity. Methods:  A total of 149 subjects (72 males and 77 females; aged 20 to 60 years) were entered into the study and randomly divided into four groups: Group 1 - toothpaste containing 5% potassium nitrate; Group 2 - toothpaste containing 5% calcium sodium phosphosilicate with fused silica; Group 3 - toothpaste containing 3.85% amine fluoride; and Group 4 - a placebo toothpaste. After sensitivity scores for controlled air stimulus and cold water at baseline were recorded, subjects were given toothpastes and sensitivity scores were measured again at 2 weeks and 6 weeks. Results:  All groups showed a reduction in sensitivity scores at 2 weeks and 6 weeks. The calcium sodium phosphosilicate group was found to be significantly better compared to the other groups at the end of 6 weeks. Conclusions:  The calcium sodium phosphosilicate group showed a better reduction in the symptoms of dentinal hypersensitivity.

Concepts: Clinical trial, Randomized controlled trial, Touring car racing, Sodium, Potassium, Dentine hypersensitivity, Remineralisation of teeth, Toothpaste

9

Dental enamel, a hierarchical material composed primarily of hydroxylapatite nanowires, is susceptible to degradation by plaque biofilm-derived acids. The solubility of enamel strongly depends on the presence of Mg(2+), F(-), and CO3 (2-). However, determining the distribution of these minor ions is challenging. We show-using atom probe tomography, x-ray absorption spectroscopy, and correlative techniques-that in unpigmented rodent enamel, Mg(2+) is predominantly present at grain boundaries as an intergranular phase of Mg-substituted amorphous calcium phosphate (Mg-ACP). In the pigmented enamel, a mixture of ferrihydrite and amorphous iron-calcium phosphate replaces the more soluble Mg-ACP, rendering it both harder and more resistant to acid attack. These results demonstrate the presence of enduring amorphous phases with a dramatic influence on the physical and chemical properties of the mature mineralized tissue.

Concepts: Chemistry, Solubility, Chemical substance, Teeth, X-ray absorption spectroscopy, Tooth enamel, Absorption spectroscopy, Remineralisation of teeth

0

The aim of this study was to compare the caries-preventive effect of different fluoride varnishes on sound dentin as well as on artificial dentin caries-like lesions. Bovine dentin specimens (n = 220) with one sound surface (ST) and one artificial caries lesion (DT) were prepared and randomly allocated to 11 groups. The interventions before pH cycling were as follows: application of a varnish containing NaF (22,600 ppm F-; Duraphat [NaF0/NaF1]), NaF plus tricalcium phosphate (22,600 ppm F-; Clinpro White Varnish Mint [TCP0/TCP1]), NaF plus casein phosphopeptide-stabilized amorphous calcium phosphate complexes (CPP-ACP; 22,600 ppm F-; MI Varnish [CPP0/CPP1]), or silver diamine fluoride (SDF; 35,400 ppm F-; Cariestop 30% [SDF0/SDF1]) and no intervention (NNB/N0/N1). During pH cycling (14 days, 6 × 120 min demineralization/day) half of the specimens in each group were brushed (10 s; 2 times/day) with either fluoride-free (“0”; e.g., TCP0) or 1,100 ppm F- (“1”; e.g., TCP1) dentifrice slurry. In another subgroup, the specimens were pH cycled but not brushed (NNB). Differences in integrated mineral loss (ΔΔZ), lesion depth (ΔLD), and colorimetric values (ΔΔE) were calculated between the values after initial demineralization and those after pH cycling, using transversal microradiography and photographic images. After pH cycling, no discoloration could be observed. Furthermore, NNB, N0, and N1 showed significantly increased ΔZDT/LDDT and ΔZST/LDST values, indicating further demineralization. In contrast, CPP0, CPP1, SDF0, and SDF1 showed significantly decreased ΔZDT/LDDT values, indicating remineralization (p ≤ 0.004; paired t test). CPP0, CPP1, SDF0, and SDF1 showed significantly higher changes in ΔΔZDT/ΔLDDT and ΔΔZST/ΔLDST than NNB, N0, and N1 (p < 0.001; Bonferroni post hoc test). In conclusion, under the conditions chosen, all fluoride varnishes prevented further demineralization. However, only NaF plus CPP-ACP and SDF could remineralize artificial dentin caries-like lesions under net-demineralizing conditions, thereby indicating that NaF plus CPP-ACP and SDF may be helpful to high-caries-risk patients.

Concepts: Dental caries, Ablative brain surgery, Tooth enamel, Phosphates, Remineralisation of teeth, Fluoride, Calcium phosphate, Tricalcium phosphate

0

The study aimed to investigate the effects of bacterial biofilms on changes in the surface microhardness of enamel treated with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) with and without fluoride. Human enamel blocks with incipient caries-like lesions were divided into four groups of 13: G1: Saliva (Control); G2: fluoride dentifrice (Crest™, 1100 ppm as NaF); G3: CPP-ACP (MI Paste; Recaldent™); and G4: CPP-ACPF (MI Paste Plus; Recaldent™ 900 ppm as NaF). The specimens were soaked in demineralizing solution for 6 h and remineralized in artificial saliva for 18 h alternately for 10 days. The dentifrice was prepared with deionized water in a 1 : 3 ratio (w/w) or applied undiluted in the case of the CPP-ACP group. The surface microhardness (SMH) was evaluated at baseline, after artificial caries, after pH cycling and treatment with dentifrices, and after incubation in media with Streptococcus mutans for biofilm formation. The biofilms were exposed once a day to 2% sucrose and the biofilm viability was measured by MTT reduction. The percentage of change in surface microhardness (%SMHC) was calculated for each block. The data were analyzed by nonparametric test comparisons (α = 0.05). The %SMHC values observed in G2 were different from those of G1, G3, and G4 (p < 0.05). After biofilm formation, %SMHC was positive in G2 and G4 when compared to G1 and G3, but resistance to demineralization after biofilm formation was similar in all groups. In conclusion, the presence of biofilms did not influence the treatment outcomes of anticaries products.

Concepts: Bacteria, Biofilm, Dental caries, Dental plaque, Tooth enamel, Remineralisation of teeth, Streptococcus mutans, Recaldent

0

Dental enamel defects (DEDs) are faulty or deficient enamel formations of primary and permanent teeth. Changes during tooth development result in hypoplasia (a quantitative defect) and/or hypomineralisation (a qualitative defect).

Concepts: Psychology, Teeth, Tooth development, Dental caries, Tooth enamel, Remineralisation of teeth, Dental fluorosis, Enamel organ

0

The purpose of this study was to evaluate the sensitivity of teeth with MIH in children before and after the use of a tooth mousse containing casein phosphopeptide and amorphous calcium phosphate (CPP-ACP).

Concepts: Milk, Calcium, Teeth, Tooth, Remineralisation of teeth, Recaldent

0

To evaluate the effects of 8% arginine-containing toothpaste on the dental plaque of no caries (NC) and high caries (HC) individuals in situ.

Concepts: Effect, Dental plaque, Remineralisation of teeth, Oral hygiene

0

To determine the efficacy of topical applications of 10% casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste in reverting white spot lesions (WSLs) after fixed orthodontic treatment. Forty one participants were randomly assigned to either the test group (CPP-ACP) or the control group (only fluoride toothpaste). All patients used regular fluoride-containing toothpaste. CPPACP paste or fluoridated toothpaste was applied on to tooth surfaces with WSLs twice a day during 36-month after de-bonding. The labial/buccal surfaces of teeth were assessed by use of DIAGNOdent pen (DD), Gorelick Index and ICDAS II criteria at baseline (T1) and 36-month (T2) follow-up visits. The total counts of Streptococcus mutans and Lactobacillus were obtained at T1 and T2. DMFT, DMFS, stimulated flow rate and buffer capacity were calculated in two appointments. Daily usage of CPP-ACP paste was not better than normal care for improving the appearance of WSLs after 36 months.

Concepts: Milk, Teeth, Dental caries, Buffering agent, Remineralisation of teeth, Fluoride, Fluoride therapy, Streptococcus mutans

0

Secondary caries is a primary reason for dental restoration failures. The objective of this study was to investigate the remineralization of human dentin lesions in vitro via restorations using nanocomposites containing nanoparticles of amorphous calcium phosphate (NACP) or NACP and tetracalcium phosphate (TTCP) for the first time.

Concepts: Nanomaterials, Dental caries, Tooth enamel, Remineralisation of teeth, Dental materials