龋病人牙釉质表面硬度及抗磨损性能测试

采用人工方法制成人牙釉质浅龋及使用抗龋措施的龋损釉质样本，分别测量各组釉质表面显微硬度，并以微动摩擦磨损试验机测试其抗磨性能，试验结果表明：各组实验组釉质较对照组表面硬度都有不同程度下降，氟化钠前处理会使釉质表达硬度显著下降，人工浅龋牙釉质的抗磨损性能不如正常釉质，使用两种抗龋措施对其抗磨性能没有明显改善。     

Permeability of Human Tooth Surfaces Studied In Vitro by Electrochemical Impedance Spectroscopy

Electrochemical Faradaic impedance spectroscopy was applied to evaluate dependence of the electrical resistance on human teeth. The experiments were performed using iodide anions as a redox probe to model permeability of teeth for fluoride upon an iontophoresis process. Tooth molars were used – as these are teeth most affected by tooth decay processes in vivo. Teeth compared included sound molars – with no evidence of pit and fissure decay, teeth with pits and fissures regarded ‘clinically’ as showing signs of decay, and teeth with crowns removed to present exposed dentin surfaces. A difference of more than an order of magnitude in electrical resistance was observed between sound molars and those regarded as showing evidence of tooth decay processes. Sound dentin, as expected from structural considerations demonstrated significantly lower resistance when compared to sound molars. Importantly, the difference in tooth resistance measured between carious and sound molars was shown to be much more representative of their structural integrity than comparison of digitally processed images of the teeth. The results support the utility of electrochemical Faradaic impedance spectroscopy for the development of understanding on how tooth electrical resistance may vary according to structural changes. This understanding may be useful to continued refinements in the use of electrical resistance measures as caries diagnostics and support generically the potential for iontophoretic processes in in‐office fluoride treatments of teeth.     

Structural features of human tooth tissues affected by high dose of external ionizing radiation after nuclear catastrophe of Chernobyl plant

The application of micro-Raman spectroscopy is discussed for the analysis of structural features of human tooth tissues affected by high doses of external ionizing radiation (0.5–1.7 Gy) after the nuclear plant catastrophe in Chernobyl in 1986. The results have shown significant changes in the mineral matrix of dental enamel that lead to the decrease of tooth enamel hardness. Destruction of the collagen chain of the organic matrix has been observed for dentin and cementum.     

The Influence of Different Bleaching Protocols on Dentinal Enzymatic Activity: An In Vitro Study

This study aimed to investigate matrix metalloproteinase (MMP) activity in human dentin using in-situ and gelatin zymography, after at-home and in-office bleaching, related to their clinical exposure times. Dentin specimens (n = 5) were treated with 35% hydrogen peroxide (50 min per session/4 sessions), 10% carbamide peroxide (180 min/21 sessions), or no treatment. All were subjected to in-situ zymography. Dentin slices were, subsequently, obtained, covered with fluorescein-conjugated gelatin, and examined with confocal laser-scanning microscopy. The fluorescence intensity was quantified and statistically analyzed using one-way ANOVA and Bonferroni tests (α = 0.05). Furthermore, gelatin zymography was performed on protein extracts obtained from dentin powder (N = 8 teeth), treated with hydrogen peroxide or carbamide peroxide, with different exposure times (10/50 min for hydrogen peroxide; 252/1260 min for carbamide peroxide). The results of the in-situ zymography showed no statistical differences between the bleached specimens and the control group, with a medium level of gelatinolytic activity expressed in the dentin tubules. The results of gelatin zymography showed an increased expression of pro-MMP-9 in carbamide peroxide groups. The expression of pro-MMP-2 decreased in all the experimental groups. The bleaching treatments performed on the enamel of sound teeth do not influence dentinal enzymatic activity. However, when unprotected dentin tissue is bleached, matrix metalloproteinases are more expressed, particularly when carbamide peroxide is used, proportional to the exposure time.     

Elemental composition of dental biologic tissues: study by means of different analytical techniques

The present study determined the organic and inorganic composition of human enamel and dentin. The instrumental neutron activation analysis, inductively-coupled plasma spectrometer, thermogravimetric and differential thermal analysis and X-ray diffraction analysis applied were and performed in the Nuclear Technology Development Centre (CDTN) and Elemental Analysis in the Department of Chemistry of the Federal University of Pernambuco, Brazil. The coronal dentin and enamel were separated from dentin mechanically (1) and by wear (2). The analyses were effective and led to the identification of the main elements present in enamel and dentin: Ca, Na, Cl, Zn, P, Mg, N, C, H, O. There was no contamination of samples of enamel or dentin in either separation technique; however, with separation technique 1, lower percentages of mainly Ca (7.25%) and O (15.16%) components were detected in dentin compared with technique 2.     

Polydopamine-assisted co-deposition of polyacrylic acid inducing dentin biomimetic mineralization for tooth-like structure repair in vitro

The aging of the global population has caused dentin exposure and root caries to become significant patient-management issues in clinical dentistry. Biomimetic remineralization, as a non-invasive therapeutic method, is of great significance to solve the problem. Herein, a novel biomimetic-mineralizing strategy to induce the self-healing of dentin defects with similar tooth structure was developed through the easy one-step polydopamine (PDA)-assisted co-deposition of polyacrylic acid (PAA) (denoted as PDA@PAA) in vitro. Immersing demineralized dentin into PAA and dopamine (DA) mixed solutions. Hereafter, the modified demineralized dentin was immersed in the supersaturated solution of calcium and phosphate at 37 °C at designated time. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflection fourier transform infrared (ATR-FTIR) were performed to analyze the interaction and co-deposition between PDA and PAA. The remineralization of demineralized dentin was characterized by field emission scanning electron microscope (FE-SEM), TEM, X-ray diffraction (XRD), friction and wear test, nanoindentation, acid resistance. And the cytocompatibility of PDA@PAA was evaluated by cell counting kit-8 (CCK-8) and cell morphology observation. The results that PAA inhibited further PDA polymerization and aggregation, PDA@PAA were co-deposited onto the surface of demineralized dentin matrix. SEM and TEM showed that the demineralized-dentin modified with PDA@PAA was completely remineralized at 12 h, not only the dentin tubules were occluded, but more importantly, the demineralized dentin collagen matrix was remineralized. Moreover, after mineralization for 24 h, a dense mineral layer similar to enamel structure was regenerated on the surface of dentin and closely combined with dentin. The results of mechanical properties and acid resistance suggested that the mechanical properties of the regenerated enamel-like structure are close to that of enamel, and its acid resistance is better than that of enamel. This study demonstrated that the PDA-assisted co-deposition of PAA can offer an inexpensive, rapid, and efficient strategy for the management of illnesses related to exposed and demineralized dentin.     

A new procedure for separation of the enamel and dentin of human teeth

A new method for the separation of enamel and dentin in various types of human teeth is proposed. The separated enamel and dentin samples have been analysed for thirteen elements by inductively-coupled plasma emission-spectroscopy and also for fluoride.     

Energy absorption build-up factors in teeth

Geometric progression fitting method has been used to compute energy absorption build-up factor of teeth [enamel outer surface, enamel middle, enamel dentin junction towards enamel, enamel dentin junction towards dentin, dentin middle and dentin inner surface] for wide energy range (0.015?C15?MeV) up to the penetration depth of 40 mean free path. The dependence of energy absorption build-up factor on incident photon energy, penetration depth, electron density and effective atomic number has also been studied. The energy absorption build-up factors increases with the penetration depth and electron density of teeth. So that the degree of violation of Lambert?CBeer (I?=?I ₀e^???t ) law is less for least penetration depth and electron density. The energy absorption build-up factors for different regions of teeth are not same hence the energy absorbed by the different regions of teeth is not uniform which depends on the composition of the medium. The relative dose of gamma in different regions of teeth is also estimated. Dosimetric implication of energy absorption build-up factor in teeth has also been discussed. The estimated absorption build up factors in different regions of teeth may be useful in the electron spin resonance dosimetry.     

INAA of enamel and dentine samples of a group of children and adults: A comparative study

Instrumental neutron activation analysis (INAA) was applied to determine Ca, Cl, Mg, Mn, Na, Sr and Zn in dentine and enamel tissues from human permanent and deciduous teeth. Comparisons were made between the results obtained in these different dental tissues as well as those obtained in permanent and deciduous teeth. The findings obtained were also compared with the published data. The accuracy and the precision of the results were evaluated by analyzing certified reference material.     

Relationship between microhardness and fluorine contents on tooth enamel determined by PIGE analysis

The remineralization effect of fluoride has been measured by surface microhardness on tooth enamel. The purpose of this study was to investigate the relationship between microhardness and fluorine concentration on tooth enamel. Twelve sound bovine enamel specimens were prepared and immersed in 0.05% NaF solution for 1, 3, 6, 24 and 36 hours, respectively. The concentration of fluorine in specimens were measured by PIGE analysis and surface microhardness of each specimen was measured by surface microhardness tester. Fluorine concentration was increased by immersing time. There was no change in microhardness of each specimen by fluorine content. The results of this study suggest that there was no relationship between the fluorine concentration and surface microhardness in sound tooth enamel. PIGE analysis can be used effectively to assess the remineralization effect of fluorine content in tooth enamel.     

Cleaning time and fate of phosphoric acid as conditioning agent on human dental enamel and dentin. An in vitro radiotracer study

In this study the cleaning time and fate of phosphoric acid on human dental enamel and dentin has been investigated, using the radioactive tracer technique with³²P as an indicator of phosphorus. Twenty seconds were found to be sufficient for cleaning the enamel from phosphoric acid, which is used for conditioning, and from formulations produced from its interaction with enamel. It was also found that dentin protection is necessary before conditioning with phosphoric acid due to the retention penetration of the latter through subsurface dentinal tubules. In addition, there seems to be an interaction between phosphoric acid and Ca(OH)₂ leading to the formation of a sparingly soluble compound.     

Human Enamel and Dentin: Effect of Gender,Geographic Location and Smoking Upon Metal Concentrations

Abstract

The goal of this study was to determine the content of 12 metals in 23 samples of teeth from two cities in Bosnia and Herzegovina (B&H): Sarajevo, a capital city with heavy traffic, industrial facilities, and long periods of smog during winter and Bihac, a picturesque small city, with no industrialization, settled among vivid national park and rivers. The teeth were separated into enamel and dentin. Dissolution of samples was performed in concentrated HNO₃ with the addition of H₂O₂ followed by flame atomic absorption spectroscopy (FAAS) analysis. The results showed expected high contents of Ca, Na, Mg, and K, while elevated contents of Cu, Fe, and Zn were present in some samples. K and Na showed uniform distributions throughout enamel and dentin. Alkaline and earth-alkaline metals showed significant positive correlations. Zinc and manganese exhibited differences in the dentin content based on the place of residence. Zinc also displayed statistically significant differences between smokers’ and nonsmokers’ dentin samples. The differences were more pronounced between intra groups (within one sample) than for inter groups (within different groups, such as location, gender, and smoking).     

Differential resin-dentin bonds created after caries removal with polymer burs

The objective of this article was to investigate the effect of carbide and polymer burs caries removal methods on the bond strength of different adhesives to dentin. Resin restorations were performed in sound and caries-affected dentin, after using polymer or carbide burs and bonding with four different adhesive (Single bond, SB; Clearfil SE bond, SEB; FL-Bond II, FLB; and Fuji II-LC, FUJI). Microtensile bond strength (MTBS) was measured. Data were analyzed with ANOVA and Student-Newman-Keuls tests. Debonded surfaces were observed by scanning electron microscopy. Bonded interfaces were examined using light microscopy (Masson's trichrome staining). In sound dentin, MTBS was similar for SEB and SB, and higher than that of FLB and FUJI. Bond strength to carbide bur prepared dentin was similar for SB, SEB, and FLB; FUJI presented the lowest. SB applied on polymer bur excavated dentin presented similar values to those of the carbide bur group; MTBS attained by SEB, FLB, and FUJI decreased when bonding to dentin treated with polymer burs; FUJI yielded pretesting failures in all specimens. Polymer burs created a thick smear layer that was not infiltrated by tested self-etching agents. The bonding effectiveness of self-etching and glass-ionomer-like adhesives to dentin decreased when polymer burs were used.     

一种长链叔胺pH敏感抗菌牙体修复材料的合成与抗菌性能

口腔粘结剂常被用于粘结复合树脂和牙本质或牙釉质,但由于残留细菌会导致继发龋病从而使得粘结剂修复体不能提供长期疗效,目前市场上使用的粘结剂均无法避免细菌滋生。本文采用两步法合成了一种甲基丙烯酸酯基封端的长链叔胺,通过柱层析进行纯化,其结构经¹H NMR和FT-IR表征,并对其抗菌性能进行了研究。结果表明：该材料可通过质子化作用提升口腔pH值抑制细菌滋生。     

A new model for nanoscale enamel dissolution

The dissolution kinetics of human tooth enamel surfaces was investigated using nanomolar-sensitive constant composition (CC) and in situ atomic force microscopy (AFM) under simulated caries formation conditions (relative undersaturation with respect to hydroxyapatite = 0.902, pH = 4.5). Scanning electron microscopic (SEM) examination of the resulting etched enamel surfaces showed that deminerzalization, initiated at core/wall interfaces of rods, developed anisotropically along the c-axes. After an initial rapid removal of surface polishing artifacts, the dissolution rate decreased as the reaction proceeded in accordance with our recently proposed crystal dissolution model, resulting in hollow enamel cores and nanosized remaining crystallites, resistant to further dissolution. Generally, dissolution of minerals is regarded as a spontaneous reaction in which all the solid phase can be dissolved in undersaturated solutions. However, the dissolution of some biominerals may be suppressed when the crystallites approach nanometer size. This study shows that CC demineralization of enamel in acidic medium follows this new model that can be used to mimic carious lesion formation. In dissolution studies, nanosized enamel crystallites exhibit a remarkable degree of self-preservation in the fluctuating physiological milieu.     

Multi-frequency electron paramagnetic resonance study of irradiated human finger phalanxes

Electron paramagnetic resonance (EPR) is often used in dosimetry using biological samples such as teeth and bones. It is generally assumed that the radicals, formed after irradiation, are similar in both tissues as the mineral part of bone and tooth is carbonated hydroxyapatite. However, there is a lack of experimental evidence to support this assumption. The aim of the present study was to contribute to that field by studying powder and block samples of human finger phalanxes that were irradiated and analyzed by multi-frequency EPR. The results obtained from bones are different from the ones obtained in enamel by several respects: the ordering of the apatite crystallites is much smaller in bone, complicating the assignment of the observed CO2- radicals to a specific location, and one type of CO3(3-) radical was only found in enamel. Moreover, a major difference was found in the non-CO2- and non-CO3(3-) signals. The elucidation of the nature of these native signals (in bone and tooth enamel) still represents a big challenge.     

Concentration of hydroxyl groups in dental apatites: a solid-state 1H MAS NMR study using inverse 31P -->1H cross-polarization

The concentration of structural hydroxyl groups in the apatite mineral of enamel, dentin and cementum of healthy human teeth was estimated by reference to stoichiometric hydroxyapatite to be 73 +/- 3, 18 +/- 2 and 18 +/- 1%, respectively.     

Evaluation of Anti-Biofilm Activity of Mouthrinses Containing Tannic Acid or Chitosan on Dentin In Situ

In contrast to enamel, dentin surfaces have been rarely used as substrates for studies evaluating the effects of experimental rinsing solutions on oral biofilm formation. The aim of the present in situ study was to investigate the effects of tannic acid and chitosan on 48-h biofilm formation on dentin surfaces. Biofilm was formed intraorally on dentin specimens, while six subjects rinsed with experimental solutions containing tannic acid, chitosan and water as negative or chlorhexidine as positive control. After 48 h of biofilm formation, specimens were evaluated for biofilm coverage and for viability of bacteria by fluorescence and scanning electron microscopy. In addition, saliva samples were collected after rinsing and analyzed by fluorescence (five subjects) and transmission electron microscopy (two subjects) in order to investigate the antibacterial effect on bacteria in a planktonic state and to visualize effects of the rinsing agents on salivary proteins. After rinsing with water, dentin specimens were covered by a multiple-layered biofilm with predominantly vital bacteria. In contrast, chlorhexidine led to dentin surfaces covered only by few and avital bacteria. By rinsing with tannic acid both strong anti-adherent and antibacterial effects were observed, but the effects declined in a time-dependent manner. Transmission electron micrographs of salivary samples indicated that aggregation of proteins and bacteria might explain the antiadhesion effects of tannic acid. Chitosan showed antibacterial effects on bacteria in saliva, while biofilm viability was only slightly reduced and no effects on bacterial adherence on dentin were observed, despite proteins being aggregated in saliva after rinsing with chitosan. Tannic acid is a promising anti-biofilm agent even on dentin surfaces, while rinsing with chitosan could not sufficiently prevent biofilm formation on dentin.     

Determination of traces of heavy metals (Mn,Cu, Zn,Cd and Pb) in microsamples of teeth material by ETV-ICP-MS

Heavy metal levels in tooth compartments would appear to be a suitable indicator of long-term exposure. A method has been developed to assess the heavy metal levels (Mn, Cu, Zn, Cd and Pb) in tooth compartments like dentin and enamel. For the simultaneous determination of these elements in small dentin sample amounts (in some cases less than 1 mg) inductively coupled plasma mass spectrometry with electrothermal vaporization was the method of choice. Sample preparation, method development and first results of the application of the method for the analysis of tooth compartments have been described. Variation in the elemental concentrations depending on the kind of tooth and the sampling position have been observed. The method is useful for epidemiological studies of the heavy metal exposure of children.     

Determination of traces of heavy metals (Mn, Cu, Zn, Cd and Pb) in microsamples of teeth material by ETV-ICP-MS

Heavy metal levels in tooth compartments would appear to be a suitable indicator of long-term exposure. A method has been developed to assess the heavy metal levels (Mn, Cu, Zn, Cd and Pb) in tooth compartments like dentin and enamel. For the simultaneous determination of these elements in small dentin sample amounts (in some cases less than 1 mg) inductively coupled plasma mass spectrometry with electrothermal vaporization was the method of choice. Sample preparation, method development and first results of the application of the method for the analysis of tooth compartments have been described. Variation in the elemental concentrations depending on the kind of tooth and the sampling position have been observed. The method is useful for epidemiological studies of the heavy metal exposure of children.