OBJECTIVESTo investigate the carious dissolution mechanism of enamel apatite nano-crystals at lattice fringe level and the possible correlation between the carious dissolution and the appearance of central dark line (CDL) in enamel crystals.

METHODSThe body of the lesion in incipient enamel caries was observed by high resolution transmission electron microscopy (HRTEM, JOEL-2010 operating at 200 kv), combined with selected-area argon-ion-beam thinning technique.

RESULTSIn the body of the lesion, the preferential core dissolution was found in most of enamel nano-crystals, whereas the peripheral dissolution of individual crystal could be occasionally observed. The initial carious dissolution of individual enamel apatite crystal occurred as a number of small electron-lucent spots along the central dark line with blurry, bent or disconnected lattice fringes. These small electron-lucent spots fused with each other to form large electron-lucent areas. Finally the central perforation was frequently seen in the crystals. The CDL always appeared in the same place with central perforation in carious crystals, which could be seen to extend along the CDL.

CONCLUSIONSThe initial carious dissolution is directly related to the lattice defects in the enamel nano-crystals. The preferential core dissolution can be partly ascribed to the CDL, which is presumed to be particularly susceptible area to caries.

Dental Caries ; metabolism ; Dental Enamel Solubility ; Humans ; Microscopy, Electron, Scanning

Tooth enamel is a complex mineralized tissue consisting of long and parallel apatite crystals configured into decussating enamel rods. In recent years, multiple approaches have been introduced to generate or regenerate this highly attractive biomaterial characterized by great mechanical strength paired with relative resilience and tissue compatibility. In the present review, we discuss five pathways toward enamel tissue engineering, (i) enamel synthesis using physico-chemical means, (ii) protein matrix-guided enamel crystal growth, (iii) enamel surface remineralization, (iv) cell-based enamel engineering, and (v) biological enamel regeneration based on de novo induction of tooth morphogenesis. So far, physical synthesis approaches using extreme environmental conditions such as pH, heat and pressure have resulted in the formation of enamel-like crystal assemblies. Biochemical methods relying on enamel proteins as templating matrices have aided the growth of elongated calcium phosphate crystals. To illustrate the validity of this biochemical approach we have successfully grown enamel-like apatite crystals organized into decussating enamel rods using an organic enamel protein matrix. Other studies reviewed here have employed amelogenin-derived peptides or self-assembling dendrimers to re-mineralize mineral-depleted white lesions on tooth surfaces. So far, cell-based enamel tissue engineering has been hampered by the limitations of presently existing ameloblast cell lines. Going forward, these limitations may be overcome by new cell culture technologies. Finally, whole-tooth regeneration through reactivation of the signaling pathways triggered during natural enamel development represents a biological avenue toward faithful enamel regeneration. In the present review we have summarized the state of the art in enamel tissue engineering and provided novel insights into future opportunities to regenerate this arguably most fascinating of all dental tissues.
Acid Etching, Dental ; Amelogenin ; Biomimetics ; trends ; Dental Enamel ; metabolism ; Dental Enamel Proteins ; Dentistry ; trends ; Tissue Engineering ; methods ; Tooth Remineralization

The main mineral component of natural tooth was determined as calcium apatite many years ago; most of them exist in the form of hydroxyapatite with different crystallites. If a tooth decayed, the crystalline of hydroxyapatite would be changed and decomposed. In our experiment, a natural tooth with caries was measured by high resolution XRD equipment: X'pert Pro. Three spots which included normal enamel, normal dentin and caries tissue were analyzed. The results showed that tooth was a kind of biological mixed crystal composed of many crystal phases, the main crystal phase was hydroxyapatite. From normal enamel to normal dentin and to caries tissue, the length of the a-axis of hydroxyapatite crystallite increased, the length of the c-axis of hydroxyapatite crystallite remained unchanged. The crystal sizes were: normal enamel D002 = 27.600 nm; normal dentin D002 = 16.561 nm; caries tissue D002 = 13.163 nm. Crystallinity: normal enamel>normal dentin>caries tissue. According to our experiment, tooth could be conveniently studied by high resolution microdiffracion XRD equipment.
Dental Caries ; metabolism ; Dental Enamel ; chemistry ; Dentin ; chemistry ; Humans ; Tooth ; chemistry ; X-Ray Diffraction ; methods

This study sought to determine the impact of dental fluorosis severity on demineralization and remineralization of human fluorosed teeth in vitro. Surface enamel microhardness was measured on the enamel blocks before and after demineralization and after remineralization. The results showed that after demineralization, the sequence of % Surface microhardness demineralization (% SMHD) was TFI4 (18.92 +/- 1.31) < TFI3 (20.50 +/- 1.32) < TFI2 (25.08 +/- 1.69) < TFI1 (27.77 +/- 1.79) < TFI0 (30.70 +/- 1.35) (P < 0.05), and there was no statistically significant differences between TFI1 (27.77 +/- 1.79) and the normal group TFI0 (30.70 +/- 1.35). After remineralization, the sequence of % Surface microhardness remineralization (% SMHR) was TFI1 (55.17 +/- 1.23) > TFI0 (53.97 +/- 3.05) > TFI2 (49.17 +/- 1.81) > TFI3 (44.85 +/- 1.89) > TFI4 (36.51 +/- 2.95) (P < 0.05). Moderately fluorosed enamel showed a significatnt resistance to caries, but mildly fluorosed enamel could get better remineralization. These facts and figures deserve clinicians' attention.
Dental Enamel ; chemistry ; pathology ; Fluorosis, Dental ; metabolism ; Humans ; In Vitro Techniques ; Tooth Demineralization ; Tooth Remineralization

Ameloblasts are specialized cells derived from the dental epithelium that produce enamel, a hierarchically structured tissue comprised of highly elongated hydroxylapatite (OHAp) crystallites. The unique function of the epithelial cells synthesizing crystallites and assembling them in a mechanically robust structure is not fully elucidated yet, partly due to limitations with in vitro experimental models. Herein, we demonstrate the ability to generate mineralizing dental epithelial organoids (DEOs) from adult dental epithelial stem cells (aDESCs) isolated from mouse incisor tissues. DEOs expressed ameloblast markers, could be maintained for more than five months (11 passages) in vitro in media containing modulators of Wnt, Egf, Bmp, Fgf and Notch signaling pathways, and were amenable to cryostorage. When transplanted underneath murine kidney capsules, organoids produced OHAp crystallites similar in composition, size, and shape to mineralized dental tissues, including some enamel-like elongated crystals. DEOs are thus a powerful in vitro model to study mineralization process by dental epithelium, which can pave the way to understanding amelogenesis and developing regenerative therapy of enamel.
Mice ; Animals ; Durapatite/metabolism* ; Dental Enamel/metabolism* ; Ameloblasts/metabolism* ; Amelogenesis ; Stem Cells ; Organoids

OBJECTIVETo invesitgate the expression patterns of amelogenin and enamelin in the developing tooth germs.

METHODSMandible sections of postnatal day 1, 3, 7 and 14 mouse were prepared, immunohistochemical analysis and reverse transcriptase polymerase chain reaction (RT-PCR) were performed to detect the expression patterns of amelogenin and enamelin in mandibular first molars.

RESULTSAmelogenin was observed in the cytoplasm of secretory ameloblasts and the whole enamel matrix layer. It was also transiently expressed in the odontoblasts of postnatal day 1 molars. Enamelin proteins were observed in the enamel layer deposited by secretory ameloblasts, especially intense beneath the ameloblast process and dentino-enamel junction. The mRNA levels of both amelogenin and enamelin were highest on postnatal day 7 (the ratio to glyceraldehyde phosphate dehydrogenase of amelogenin and enamelin: 0.813 ± 0.085 and 0.799 ± 0.064, respectively, P < 0.05).

CONCLUSIONSAmelogenin and enamelin were enamel matrix proteins predominately expressed by secretory ameloblasts. The temporal-spatial expression patterns of amelogenin and enamelin indicate the important roles they played in amelogenesis and biomineralization.

Ameloblasts ; metabolism ; Amelogenesis ; Amelogenin ; genetics ; metabolism ; Animals ; Dental Enamel ; metabolism ; Dental Enamel Proteins ; genetics ; metabolism ; Mice ; Mice, Inbred ICR ; Molar ; metabolism ; Odontoblasts ; metabolism ; RNA, Messenger ; metabolism ; Time Factors ; Tooth Germ ; growth & development ; metabolism

Various biological approaches to the promotion of periodontal regeneration have been used. These can be divided into the use of growth and differentiation factors, application of extracellular matrix proteins and attachment factors and use of mediators of bone metabolism. The purpose of this study was to evaluate the effect of enamel matrix protein and platelet-rich plasma on the treatment of intrabony defect, with bovine-derived bone powder in humans by digital subtraction radiography. 12 teeth(experimental I group) were treated with enamel matrix protein combined with bovine-derived bone powder and 12 teeth(experimental II group) were treated with platelet-rich plasma combined with bovine-derived bone powder. The change of bone density was assessed by digital subtraction radiography in this study. The change of mineral content was assessed in the method that two radiographs were put into computer program to be overlapped and the previous image was subtracted by the later one. Both groups were statistically analyzed by Wilcoxon signed Ranks Test and Mann-whitney Test using SPSS program for windows(5% significance level). The results were as follows: 1. The radiolucency in 3 months after surgery was significantly increased than 1 month after surgery in both groups(experimental I and II groups)(p<0.05). 2. The radiopacity in 6 months after surgery was significantly increased than 3 months after surgery in both groups(experimental I and II groups)(p<0.05). 3. In experimental I group, there was no significant difference between 1 month and 6 months after surgery. 4. In experimental II group, the radiopacity in 6 months after surgery was significantly increased than 1 month after surgery(p<0.05). 5. There was no significant difference between experimental I and II group at 1 month and 3 months after surgery, but the radiopacity in experimental II group was significantly increased at 6 months after surgery(p<0.05). In conclusion, platelet-rich plasma can enhance bone density than enamel matrix protein until 6 months after surgery.
Bone Density ; Dental Enamel* ; Extracellular Matrix Proteins ; Heterografts* ; Humans* ; Metabolism ; Platelet-Rich Plasma* ; Radiography* ; Regeneration

OBJECTIVETo analyze the effects of emdogain(EMD) on the expression of the bone sialoprotein(BSP) gene in human dental pulp cells and to elucidate the molecular mechanism of BSP gene regulated by EMD.

METHODSHuman dental pulp was harvested from premolars freshly extracted for orthodontic purpose and cultured. Cells were divided into different concentrations (25, 50, 100 and 250 mg/L) of EMD and control groups (Dulbecco's modified Eagle's medium). Total RNA of cells was extracted. Human BSP mRNA levels was detected with the real-time PCR. Regulations of EMD on human BSP protein levels were detected with Western blotting.

RESULTSIn the real-time PCR, at the same time point, there were significant differences on BSP mRNA levels between 25, 50, 100 and 250 mg/L EMD groups (7 d:1.79 ± 0.03, 2.03 ± 0.10, 2.67 ± 0.08, 2.94 ± 0.07) and control group (7 d:1.06 ± 0.11) (P < 0.001); at the different time point (1, 3, 5 and 7 d), the same dose(250 mg/L) of EMD stimulated human dental pulp cells, BSP mRNA (2.30 ± 0.06, 2.65 ± 0.05, 2.76 ± 0.05, 2.94 ± 0.07) was increased (P < 0.05). Treatment of human dental pulp cells with EMD (250 mg/L) increased the protein levels.

CONCLUSIONSEMD increases BSP mRNA and protein levels in human dental pulp cells.

Bicuspid ; Cells, Cultured ; Dental Enamel Proteins ; pharmacology ; Dental Pulp ; cytology ; metabolism ; Gene Expression Regulation ; Humans ; Integrin-Binding Sialoprotein ; genetics ; metabolism ; RNA, Messenger ; metabolism

OBJECTIVEThere is a paucity of published works that systematically evaluate gene anomalies or clinical features of patients with renal cysts and diabetes syndrome (RCAD)/maturity onset diabetes of the young type 5 (MODY5). The purpose of this review was to systematically assess the detection rate, genetic and phenotypic implications of heterozygous autosomal dominant TCF2 anomalies.

DATA SOURCESMEDLINE database was searched to select articles recorded in English from 1997 to 2008. The focus was monoallelic germline TCF2 gene mutations/deletions. Biallelic inactivation, polymorphisms, DNA modification (hypomethylation and hypermethylation), loci associated with cancer risk, and somatic TCF2 anomalies were all excluded.

STUDY SELECTIONAfter searching the literature, 50 articles were selected.

RESULTSThe detection rate of TCF2 anomalies was 9.7% and varied considerably among MODY (1.4%), renal structure anomalies (RSA) (21.4%) and RSA with MODY (41.2%) subgroups. Mutations were strikingly located within the DNA binding domain and varied among exons of the DNA binding domain: exons 2 and 4 were the hottest spots, while mutations were sporadically distributed in exon 3. The consistent phenotypes were RSA (89.6%) and diabetes mellitus (DM) (45.0%). However, the concurrence of RSA and DM was relatively low (27.5%), which hinders the optimal performance of genetic testing and obtainment of timely diagnosis. Other organ involvements were complementary and necessary for the early identification of patients with TCF2 anomalies. Analysis of phenotypes of TCF2 point mutations showed significant differences in the detection rates of RSA, impaired renal function (IRF) and DM according to mutation type but not mutation location.

CONCLUSIONThese valuable features of TCF2 anomalies that previously did not receive sufficient attention should not be neglected.

Central Nervous System Diseases ; metabolism ; Dental Enamel ; abnormalities ; metabolism ; Diabetes Mellitus ; metabolism ; Diabetes Mellitus, Type 2 ; metabolism ; Hepatocyte Nuclear Factor 1-beta ; metabolism ; Humans ; Kidney Diseases, Cystic ; metabolism

OBJECTIVETo evaluate in vivo the remineralization containing trace elements.

METHODSThe volunteers were selected by pre-designed criteria of adopting and eliminating. Caries-like lesions were prepared in the enamel of extracted human premolars with the use of demineralizing solution. Sections of the normal and lesion enamel (approximately 2 mm x 2 mm) were prepared, with the cut surfaces protected by nail varnish. 2 enamel specimens were mounted in a removable appliance. By measuring lesion parameters (area, total and average dye fluorescence) on a tooth with confocal laser scanning microscopy (CLSM), the effect of remineralization was assessed. Specimens were cut and stained with a fluorescent dye (0.1 mmol/L rhodamine B) for 1 h and analyzed using CLSM.

RESULTSCLSM detected significantly greater remineralization (P < 0.05) in the specimens treated with the trace elements fluoride-containing solution and only containing fluoride (P < 0.05), especially more obvious difference was shown upon remineralized solution with trace elements, which means it produced a greater remineralization. CLSM data of remineralized solution with trace elements were showed: delta Z vs. Area = -50.4 +/- 8.1; delta Z vs. TF = -27.8 +/- 3.8; delta Z vs. AF = -91.5 +/- 8.9.

CONCLUSIONSThe ability of remineralization of the new solution is better than that only containing fluoride in in vivo study. It can potentially prevent initiation of caries. This study provides not only the theoretical foundation for clinical application, but also shows a new kind of experimental method in the study of demineralization and remineralization.

Dental Caries ; drug therapy ; metabolism ; Dental Enamel ; drug effects ; metabolism ; Fluorides ; pharmacology ; Humans ; Microscopy, Confocal ; Tooth Remineralization ; methods ; Trace Elements ; pharmacology