OBJECTIVES: Through the investigation of the microhardness and microstructure of permanent tooth enamel at various eruption stages during childhood, this research offers references for the early prevention of childhood dental caries. METHODS: Forty-five premolars extracted due to orthodontic reasons were collected and screened. These premolars were divided into three experimental groups according to the time since eruption: Group A (erupted for 0-1 year), Group B (erupted for 1-3 years), and Group C (erupted for 3-5 years). Additionally, the third molars that were extracted due to impaction and had not erupted were selected as the control group, with 15 teeth in each group. Samples were prepared, and the surface microhardness, microstructure, and elemental composition of the enamel were measured using Vickers microhardness tester, scanning electron microscope, and electron probe, respectively. RESULTS: Compared with that in the control group, the microhardness of enamel in groups A, B, and C increased with prolonged eruption time, the surface porosity structure decreased considerably, the contents of Na and Mg on the surface decreased, and that of F increased (P<0.05). CONCLUSIONS The microhardness and microstructure of enamel in permanent teeth at different stages vary. Permanent teeth are at a substantially higher risk of caries within one year after eruption, and early prevention should be emphasized.
Dental Enamel/ultrastructure* ; Humans ; Hardness ; Dental Caries/prevention & control* ; Microscopy, Electron, Scanning ; Tooth Eruption ; Bicuspid/chemistry* ; Dentition, Permanent ; Child ; Child, Preschool

OBJECTIVE: To explore the histological structure of the deciduous teeth and the tooth germs of Tibetan miniature pigs for studies of dental tissue diseases and tooth regeneration. METHODS: The structure of the deciduous teeth of Tibetan miniature pigs was observed by X-ray. The ultrastructure of the enamel and dentin of deciduous teeth was characterized by scanning electron microscopy. The jaws and teeth were three-dimensionally reconstructed using Mimics software based on Micro-CT scanning of the deciduous teeth. Image J software was used to calculate the gray value and the mineralization density of the deciduous teeth. Hisotological structure of the tooth germ and the pulp tissue of Tibetan miniature pigs was observed using HE staining. RESULTS: The deciduous teeth of Tibetan miniature pigs were composed of enamel, dentin and medullary pulp tissue. The permanent tooth germ were formed during the deciduous dentition. The enamel and dentin ultrastructure of deciduous teeth were consistent with that of human deciduous teeth. The enamel and dentin mineralization densities were 2.47±0.09 g/cm and 1.72±0.07 g/cm, respectively. The pathological structures of tooth germ and pulp tissue were similar to those of human teeth, and the pulp tissue of the deciduous teeth was in an undifferentiated state. CONCLUSIONS The deciduous teeth of Tibetan miniature pig have similar anatomy, ultrastructure and histopathological structure to human teeth and can serve as a good animal model for studying human dental tissue diseases and the mechanisms of tooth regeneration.
Animals ; Dental Enamel ; ultrastructure ; Dental Pulp ; Dentin ; ultrastructure ; Swine ; Swine, Miniature ; Tibet ; Tooth Germ ; Tooth, Deciduous ; anatomy & histology

Tooth bleaching agents may weaken the tooth structure. Therefore, it is important to minimize any risks of tooth hard tissue damage caused by bleaching agents. The aim of this study was to evaluate the effects of applying 45S5 bioglass (BG) before, after, and during 35% hydrogen peroxide (HP) bleaching on whitening efficacy, physicochemical properties and microstructures of bovine enamel. Seventy-two bovine enamel blocks were prepared and randomly divided into six groups: distilled deionized water (DDW), BG, HP, BG before HP, BG after HP and BG during HP. Colorimetric and microhardness tests were performed before and after the treatment procedure. Representative specimens from each group were selected for morphology investigation after the final tests. A significant color change was observed in group HP, BG before HP, BG after HP and BG during HP. The microhardness loss was in the following order: group HP>BG before HP, BG after HP>BG during HP>DDW, BG. The most obvious morphological alteration of was observed on enamel surfaces in group HP, and a slight morphological alteration was also detected in group BG before HP and BG after HP. Our findings suggest that the combination use of BG and HP could not impede the tooth whitening efficacy. Using BG during HP brought better protective effect than pre/post-bleaching use of BG, as it could more effectively reduce the mineral loss as well as retain the surface integrity of enamel. BG may serve as a promising biomimetic adjunct for bleaching therapy to prevent/restore the enamel damage induced by bleaching agents.
Animals ; Biomimetic Materials ; analysis ; therapeutic use ; Cattle ; Ceramics ; analysis ; chemistry ; Chemical Phenomena ; Color ; Colorimetry ; Dental Enamel ; drug effects ; ultrastructure ; Electron Probe Microanalysis ; Glass ; analysis ; chemistry ; Hardness ; Hydrogen Peroxide ; pharmacology ; Hydrogen-Ion Concentration ; Microscopy, Electron, Scanning ; Protective Agents ; analysis ; therapeutic use ; Random Allocation ; Solubility ; Spectroscopy, Fourier Transform Infrared ; Time Factors ; Tooth Bleaching ; methods ; Tooth Bleaching Agents ; pharmacology ; Water ; chemistry ; X-Ray Diffraction

This in vitro study aims to evaluate the crystal and surface microstructure of dental enamel after cold-light bleaching treatment. Twelve sound human premolars were cross-split into four specimens, namely, mesio-buccal (Group LP), disto-buccal (Group P), mesio-lingual (Group NP) and disto-lingual (Group L) specimens. These four groups were treated using the standard cold-light bleaching procedure, a bleaching agent, a peroxide-free bleaching agent and cold-light, respectively. Before and after treatment, all specimens were analyzed by high-resolution, micro-area X-ray diffraction and scanning electron microscopy. Using a spectrometer, tooth color of all specimens was measured before and after treatment. The phase of the enamel crystals was identified as hydroxyapatite and carbonated hydroxyapatite. After treatment, specimens in Groups LP and P showed significantly weaker X-ray diffraction peaks, significant reduction in crystal size and crystallinity, significant increase in L* but decrease in a* and b*, and obvious alterations in the surface morphology. However, specimens in Groups NP and L did not show any significant changes. The cold-light bleaching treatment leads to demineralization in the enamel surface. The acidic peroxide-containing bleaching agent was the major cause of demineralization, whereas cold-light did not exhibit significant increase or decrease effect on this demineralization.
Color ; Crystallography ; Dental Enamel ; drug effects ; radiation effects ; ultrastructure ; Durapatite ; radiation effects ; Humans ; Hydrogen Peroxide ; pharmacology ; Hydrogen-Ion Concentration ; Lighting ; instrumentation ; Materials Testing ; Microscopy, Electron, Scanning ; Silicon Dioxide ; pharmacology ; Spectrum Analysis ; Tooth Bleaching ; methods ; Tooth Bleaching Agents ; classification ; pharmacology ; Tooth Demineralization ; pathology ; X-Ray Diffraction

OBJECTIVETo evaluate casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and several fluoride products in inhibiting enamel demineralization.

METHODSSeventy healthy premolars extracted before orthodontic treatment were divided into seven groups (A: CPP-ACP; B: CPP-ACP + fluoride mouth rinses; C: fluoride mouth rinses; D: fluoride glass ionomer protection; E: fluoride resin binder; F: fluoride varnish; G: control group). There were ten samples in each group. The teeth were dipped into an artificial caries solution ten minutes at a time, then applied separately with CPP-ACP, CPP-ACP + fluoride mouth rinses, fluoride mouth rinses, fluoride glass ionomer protection, fluoride resin binder and fluoride varnish on labial enamel. The samples were dipped into an artificial saliva solution (37°C). Then all samples were examined with atomic force microscope (AFM) at the end of first, second and third monthes.

RESULTSAt the end of the first month, surface roughness in group D [(114 ± 1) nm] was significantly lower than that in group G[(172 ± 9) nm]. At the end of the second month and the third month, significant difference was found in surface roughness between group G and the rest of groups (P < 0.05); between group B and the rest of groups; and between group C and groups (D, E and F).

CONCLUSIONSCPP-ACP and fluoride could both inhibit enamel demineralization in vitro. Solid fluoride (groups D, E and F) had better results than liquid fluoride (group C).

Adolescent ; Bicuspid ; ultrastructure ; Caseins ; therapeutic use ; Child ; Dental Enamel ; ultrastructure ; Fluorides ; therapeutic use ; Humans ; Microscopy, Atomic Force ; Random Allocation ; Tooth Demineralization ; prevention & control ; Tooth Remineralization

OBJECTIVETo establish the femtosecond laser experimental platform in vitro for numerical controlled cavity preparation, and to evaluate the roughness quantitatively and observe the microscopic morphology of the cutting surface.

METHODSEnamel and dentin planes were prepared on human third molars. A universal motion controller was used to control the samples to do rectangle wave motion perpendicular to the incident direction of the laser at focus. The surface roughness was observed with confocal laser scanning microscope.

RESULTSPrecise ablation of the dental hard tissues can be achieved with the established femtosecond laser numerical control platform. For enamel, the surface roughness of the cavity inside laser scanning line was 7.173 µm at the bottom and 2.675 µm on the wall of the cavity. The surface roughness of the cavity between laser scanning lines was 13.667 µm at the bottom and 33.927 µm on the wall. For dentin, the surface roughness of the cavity bottom was 51.182 µm and 25.629 µm for the wall. Scanning electron microscope images showed no micro-cracks or carbonization on enamel, while carbonization, cracks and a small amount of crystalline particles were observed on dentin.

CONCLUSIONSPrecise tooth preparation can be achieved with femtosecond laser numerical control flatform. The surface roughness of cavity wall was less than that of the bottom and can meet the clinical needs. Suitable femtosecond laser output power should be set for different cutting objects, otherwise it may result in tissue damages.

Dental Cavity Preparation ; methods ; Dental Enamel ; surgery ; ultrastructure ; Dentin ; surgery ; ultrastructure ; Hardness ; Humans ; Laser Therapy ; methods ; Microscopy, Electron, Scanning ; Molar, Third ; surgery ; ultrastructure ; Surface Properties

OBJECTIVETo compare the three dimensional morphology and surface roughness changes of enamel eroded for different etching time.

METHODSFifteen freshly extracted sound human pre-molars for orthodontic purpose were collected. The buccal surface of teeth were prepared into smooth enamel slices, and then were randomly divided into 5 groups based on their etching time 0 s (control group), 5 s, 10 s, 20 s, 30 s, respectively by 37% phosphoric acid. The three dimensional morphology was observed under atomic force microscope (AFM). The profile was analyzed, and the value of Ra, Rq, Rz and the surface area and volume were measured.

RESULTSThe AFM photograph showed that with the etching time from 0 s to 20 s the enamel surface demineralised gradually, the top structure of enamel rod and the fish scaled structure became obvious. But the morphology only changed a bit after 20 s. The surrounding inter-rod enamel eroded first, the depth increased to 2.8 µm at 20 s but decreased to 1.8 µm at 30 s. The value of Ra increased from (19.69 ± 3.42) nm to (359.51 ± 75.79) nm, and Rq from (22.02 ± 5.57) nm to (431.02 ± 83.09) nm, Rz from (0.24 ± 0.08) µm to (2.38 ± 0.26) µm. Except for groups 20 s and 30 s, the difference among other groups was statistically significant (P < 0.05). The surface area expanded from (406.77 ± 3.88) µm(2) to (546.69 ± 84.02) µm(2), and surface volume from (65.73 ± 14.46) µm(3) to (474.63 ± 52.50) µm(3).

CONCLUSIONSThe depth, surface roughness, surface area and volume caused by erosion increased with etching time. The three dimensional morphology greatly changed by acid-etching process.

Acid Etching, Dental ; methods ; Analysis of Variance ; Dental Enamel ; drug effects ; ultrastructure ; Humans ; Microscopy, Atomic Force ; Phosphoric Acids ; pharmacology ; Random Allocation ; Surface Properties ; drug effects ; Time Factors

OBJECTIVETo study the effects of the cold-light bleaching technique on crystals and microstructure of the dental enamel.

METHODSThe human premolars extracted for orthodontic reasons were treated by a standard cold-light bleaching procedure. After the treatment, all samples were detected by high resolution micro-area X-ray diffractometer, Fourier transform infrared spectroscope and scanning electron microscope.

RESULTSAfter the permanent teeth were treated with cold-light bleaching technique, the enamels' crystal dimension, crystallinity decreased and irregular surfaces and shallow disk pits appeared.

CONCLUSIONThe cold-light bleaching technique could lead to the changes of crystals and microstructure in the surface layer of dental enamel.

Bicuspid ; Dental Enamel ; radiation effects ; ultrastructure ; Humans ; Light ; Microscopy, Electron, Scanning ; Spectroscopy, Fourier Transform Infrared ; Tooth Bleaching ; methods

OBJECTIVETo investigate the effect of ozone on remineralization of enamel in vitro.

METHODSCaries-like lesions were prepared in the enamel of extracted cattle incisors with demineralizing solution. The specimens were treated with deionized water, 1000 mg/kg fluoride, 4.5 mg/L ozone, and pH-cycled. The scanning electron microscope (SEM) was used to observe the surface of enamel specimens. The effect of remineralization was assessed by three lesion parameters (fluorescent area, total and average fluorescence), which were measured with confocal laser scanning microscope (CLSM). The data were collected and analyzed by SNK test in ANOVA.

RESULTSSEM observation showed that the surface morphology of the deionized water group and ozone group were similar: porous and atactic; but the surface morphology of fluoride group was smooth and the aperture became smaller. The three parameters in the three groups were as follows, respectively. Delta A were (0.31 +/- 0.28), (1.73 +/- 0.63) and (0.28 +/- 0.19) x 10(4) microm2, Delta TF were (0.42 +/- 0.34), (2.53 +/- 0.73) and (0.48 +/- 0.27) x 10(5), Delta AF were (3.35 +/- 2.55), (46.51 +/- 16.64) and (4.95 +/- 3.05). The fluoride group was significantly greater than deionized water group and ozone group (P < 0.05); but there was no significant difference between the deionized water group and ozone group.

CONCLUSIONSThe results of this in vitro study suggest that ozone has no effect on remineralization of enamel blocks.

Animals ; Cattle ; Dental Enamel ; drug effects ; pathology ; ultrastructure ; In Vitro Techniques ; Microscopy, Electron, Scanning ; Ozone ; pharmacology ; Tooth Demineralization ; pathology ; Tooth Remineralization

OBJECTIVETo investigate the effect of pulse Nd: YAG laser combined with NaF on caries resistance of human enamel in vitro.

METHODS24 caries-free, constant premolares were cut into enamel mass. Surface ultrastructure and fluoride distribution of enamel in laser-NaF treated group, laser treated group, NaF treated group and control group were observed by scanning electron microscope (SEM) and electron probe microanalyzer.

RESULTS(1) SEM observation: In laser-NaF treated group, the smear layer was almost removed, the enamel surface showed partially melted-like and bubble-like appearance, diffuse white-small particles distributed on enamel surface, and melted position, microcrack and microhole appeared whitely blocking-reflection. (2) Electron probe microanalyzer analysis: In enamel samples, the highest average Ci of F- and the hightest depth which F- entered in enamel were recorded in the laser-NaF treated group. The average Ci of F- in laser-NaF treated group was significantly increased compared with that in NaF-treated group or laser-treated group or control group (P < 0.001).

CONCLUSIONThe pulsed Nd:YAG laser combined with sodium fluoride could make the enamel surface partially melt, change the structure of the crystal, enhance the absorption of fluoride, and clear smear layer. This technology may resist the caries.

Dental Enamel ; ultrastructure ; Fluorides ; chemistry ; Humans ; Lasers, Solid-State ; Smear Layer ; Sodium Fluoride ; chemistry