A Comparison of the Fluoride 'Paint- On' vs Tray Application Techniques for Enamel Remineralisation.

BACKGROUND: Fluoride gel treatment is not recommended for children < 6 years old due to its potential toxicity. Hence the aim of this study was to compare the effect of 1.23% acidulated-phosphate fluoride (APF) gel paint-on and the conventional tray application techniques on artificial, deciduous enamel carious lesions embedded on wearable appliances. METHODS: In a randomised crossover study, the volunteer children (n = 29) wore mandibular removable appliances containing embedded tooth specimens with artificial carious lesions. The volunteers had 3 different treatment protocols: (I) 0.4 mL non-fluoride (control) gel, (II) 0.4 mL paint-on 1.23% APF gel or (III) 5 mL 1.23% APF gel, 4 minutes tray application. After 1 hour, the appliances were removed and the specimens underwent an in vitro, 14 days of pH-cycling. The mean percentage reduction in fluorescence (ΔF, %) at baseline (ΔF0) and after the pH-cycling (ΔF1) were determined using quantitative light-induced fluorescence-digital analysis. The mean ΔΔF (ΔF1-ΔF0) was calculated to compare the differences between groups. RESULTS: The mean ΔΔF of groups I to III were -1.42 ± 1.49, 1.06 ± 2.11, and 1.12 ± 3.57 and -1.25 ± 1.44, 1.13 ± 1.84 and 1.44 ± 3.62 for the smooth surface and proximal surface lesions, respectively. The mean ΔΔF in the 2 treatment groups were significantly greater compared with the control group (P < .001). There was no significant difference in ΔΔF between the APF gel tray and paint-on groups either in the smooth surfaces, or the proximal surfaces (P = .629 and P = .613, respectively). CONCLUSION: Our study, for the first time, indicates that the paint-on application of APF gel or the tray application of APF had a similar enamel remineralisation effect. Clinically, this implies that, particularly in younger children, the paint-on application of fluoride is less cumbersome, and possibly more tolerable with a lesser likelihood of fluoride ingestion than the tray application technique. TRIAL REGISTRATION: Thai Clinical Trial Registry (https://www.thaiclinicaltrials.org/show/TCTR20190724001).

Dental caries and associated risk factors in 13- to 18-month-old infants receiving breast or formula milk feeding: A cross-sectional study.

BACKGROUND: The association between breast milk feeding and dental caries risk in children remains controversial. Moreover, it is unclear whether risk factors for caries differ between breast milk-fed and formula milk-fed infants. AIM: To investigate dental caries in 13- to 18-month-old infants receiving breast milk or formula milk feeding and associated risk factors. DESIGN: One hundred and sixty-six 13- to 18-month-old infants were recruited from a tertiary hospital in Bangkok, Thailand. Information on feeding practices, demographics, and potential risk factors was collected using a caregiver questionnaire. Carious lesions were identified by visual and tactile examination. The Chi-squared test, Mann-Whitney U test, and logistic regression model were used for statistical analysis. RESULTS: The prevalence of caries in breast milk- and formula milk-fed infants was 31.8% and 36.0%, respectively, with no statistically significant difference (p = .579). Among all children, having dental plaque deposition on more than one third of the crown (adjusted OR (aOR): 15.11%; 95% CI: 6.11-37.35) and sleeping while milk feeding (aOR: 2.20%; 95%CI: 1.01-4.77) were associated with dental caries. In subgroup analysis, however, sleeping while milk feeding increased caries risk in the formula milk-fed group only (aOR: 2.95%; 95%CI: 1.07-8.12). CONCLUSIONS: The type of milk feeding was not associated with dental caries, whereas dental plaque and sleeping while milk feeding increased the odds of having dental caries in this population.

Molecular Cloning of Mouse Homologue of Enamel Protein C4orf26 and Its Phosphorylation by FAM20C.

It is widely accepted that cellular processes are controlled by protein phosphorylation and has become increasingly clear that protein degradation, localization and conformation as well as protein-protein interaction are the examples of subsequent cellular events modulated by protein phosphorylation. Enamel matrix proteins belong to members of the secretory calcium binding phosphoprotein (SCPP) family clustered on chromosome 4q21, and most of the SCPP phosphoproteins have at least one S-X-E motifs (S; serine, X; any amino acid, E; glutamic acid). It has been reported that mutations in C4orf26 gene, located on chromosome 4q21, are associated with autosomal recessive type of Amelogenesis Imperfecta (AI), a hereditary condition that affects enamel formation/mineralization. The enamel phenotype observed in patients with C4orf26 mutations is hypomineralized and partially hypoplastic, indicating that C4orf26 protein may function at both secretory and maturation stages of amelogenesis. The previous in vitro study showed that the synthetic phosphorylated peptide based on C4orf26 protein sequence accelerates hydroxyapatite nucleation. Here we show the molecular cloning of Gm1045, mouse homologue of C4orf26, which has 2 splicing isoforms. Immunohistochemical analysis demonstrated that the immunolocalization of Gm1045 is mainly observed in enamel matrix in vivo. Our report is the first to show that FAM20C, the Golgi casein kinase, phosphorylates C4orf26 and Gm1045 in cell cultures. The extracellular localization of C4orf26/Gm1045 was regulated by FAM20C kinase activity. Thus, our data point out the biological importance of enamel matrix-kinase control of SCPP phosphoproteins and may have a broad impact on the regulation of amelogenesis and AI.

FAM20A binds to and regulates FAM20C localization.

Mutations in the Family with sequence similarity (FAM) 20 gene family are associated with mineralized tissue phenotypes in humans. Among these genes, FAM20A mutations are associated with Amelogenesis Imperfecta (AI) with gingival hyperplasia and nephrocalcinosis, while FAM20C mutations cause Raine syndrome, exhibiting bone and craniofacial/dental abnormalities. Although it has been demonstrated that Raine syndrome associated-FAM20C mutants prevented FAM20C kinase activity and secretion, overexpression of the catalytically inactive D478A FAM20C mutant was detected in both cell extracts and the media. This suggests that FAM20C secretion doesn't require its kinase activity, and that another molecule(s) may control the secretion. In this study, we found that extracellular FAM20C localization was increased when wild-type (WT), but not AI-forms of FAM20A was co-transfected. On the other hand, extracellular FAM20C was absent in the conditioned media of mouse embryonic fibroblasts (MEFs) derived from Fam20a knock-out (KO) mouse, while it was detected in the media from WT MEFs. We also showed that cells with the conditioned media of Fam20a WT MEFs mineralized, but those with the conditioned media of KO MEFs failed to mineralize in vitro. Our data thus demonstrate that FAM20A controls FAM20C localization that may assist in the extracellular function of FAM20C in mineralized tissues.

IL-6 regulates stress-induced REX-1 expression via ATP-P2Y1 signalling in stem cells isolated from human exfoliated deciduous teeth.

OBJECTIVE: To investigate the relationship between ATP and IL-6 in mechanical stress-induced REX-1 expression in SHEDs. METHODS: Cells were stimulated with mechanical stress (0-2.5 gcm(-2)), IL-6 (0.1-5 ng/ml), or ATP (10-100 µM) for 2h in serum-free media. IL-6 and REX-1 expression was examined by qualitative and quantitative polymerase chain reaction. ATP release was measured using a bioluminescence assay. The molecular mechanisms of the signalling pathways were investigated using chemical inhibitors. RESULTS: Mechanical stress induced IL-6 and REX-1 mRNA expression and ATP release. JAK inhibitor I inhibited the increase in REX-1 expression and ATP release but not IL-6 induction. Furthermore, suramin inhibited the upregulation of REX-1 mRNA expression but not ATP release. Exogenous IL-6 promoted both ATP release and REX-1 expression. The IL-6-induced REX-1 expression was attenuated by a P2Y1-specific receptor antagonist. Moreover, REX-1 expression was upregulated in a dose-dependent manner by the addition of ATP or a P2Y1 agonist. This inductive effect was abolished by the P2Y1-specific receptor antagonist. CONCLUSIONS: ATP-P2Y1 signalling is involved in IL-6-regulated stress-induced REX-1 expression in SHEDs. These results imply the participation of mechanical stress, IL-6, and ATP in regulating the expression of REX-1, a pluripotent stem cell marker.