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1.
PLoS One ; 15(9): e0239073, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32966343

RESUMEN

Lower Eocene (Wasatchian-aged) sediments of the Margaret Formation on Ellesmere Island in Canada's High Arctic preserve evidence of a rainforest inhabited by alligators, turtles, and a diverse mammalian fauna. The mammalian fossils are fragmentary and often poorly preserved. Here, we offer an alternative method for their identification. Among the best preserved and extensive of the Eocene Arctic forests is the Strathcona Fiord Fossil Forest, which contains permineralized in situ tree stumps protruding from a prominent coal seam, but a paucity of vertebrate fossils. In 2010 and 2018, we recovered mammalian tooth fragments at the fossil forest, but they are so incomplete as to be undiagnostic by using their external morphology. We used a combination of light microscopy and SEM analysis to study the enamel microstructure of two tooth fragments from the fossil forest-NUFV2092B and 2092E. The results of our analysis indicate that NUFV2092B and 2092E have Coryphodon-enamel, which is characterized by vertical bodies that manifest as bands of nested chevrons or treelike structures visible in the tangential section under light microscopy. This enamel type is not found in other mammals known from the Arctic. Additionally, when studied under SEM, the enamel of NUFV2092B and 2092E has rounded prisms that open to one side and are surrounded by interprismatic matrix that is nearly parallel to the prisms, which also occurs in Coryphodon enamel, based on prior studies. The tooth fragments reported here, along with some poorly preserved bone fragments, thus far are the only documented vertebrate fossils from the Strathcona Fiord Fossil Forest. However, fossils of Coryphodon occur elsewhere in the Margaret Formation, so its presence at the fossil forest is not surprising. What is novel in our study is the way in which we identified the fossils using their enamel microstructure.


Asunto(s)
Esmalte Dental/ultraestructura , Fósiles/ultraestructura , Animales , Regiones Árticas , Canadá , Esmalte Dental/anatomía & histología , Bosques , Fósiles/anatomía & histología , Mamíferos/anatomía & histología , Microscopía Electrónica de Rastreo , Microscopía de Polarización , Diente/anatomía & histología , Diente/ultraestructura
2.
PLoS One ; 15(8): e0237195, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32764819

RESUMEN

This study investigated the caries-preventive effect of 445 nm laser radiation in combination with fluoride on the prevention of white spot lesions. Previously, several studies have indicated the ability of 488 nm argon ion laser irradiation to reduce early enamel demineralization. A diode laser (445 nm) could be an alternative technology for possible caries-preventive potential. Each sample of a group of seventeen caries-free bovine teeth was treated in four different ways on four different zones of the labial surface: control/no treatment (C), laser irradiation only (L) (0.3 W, 60 s and applied dose of 90 J/cm2), amine fluoride application only (10,000 ppm and pH 3.9) (F), and amine fluoride application followed by laser irradiation (FL). After treatment, the teeth were subjected to a demineralization solution (pH 4.3 for 48 h at 37 °C) to induce subsurface lesions. After sectioning, the teeth were examined by light microscopy. Three teeth were analyzed by scanning electron microscopy (SEM). The depths of the subsurface lesions in the C, L, F, and FL groups were 103.01 (± 13.04), 96.99 (± 14.51), 42.59 (± 17.13), and 24.35 (± 11.38) µm, respectively. The pairwise group comparison showed the following results: p < 0.001 for FL versus C, FL versus L, F versus C, and F versus L, p = 0.019 for FL versus F and p = 0.930 for L versus C. The SEM micrographs support the light-microscopic examination. The results of the current study have shown that using relatively low irradiation settings of 445 nm laser on fluoridated enamel may be effective for prevention of white spot lesions.


Asunto(s)
Caries Dental/prevención & control , Fluoruros Tópicos/administración & dosificación , Terapia por Luz de Baja Intensidad/métodos , Desmineralización Dental/prevención & control , Animales , Bovinos , Terapia Combinada/métodos , Esmalte Dental/efectos de los fármacos , Esmalte Dental/efectos de la radiación , Esmalte Dental/ultraestructura , Humanos , Láseres de Semiconductores/uso terapéutico , Microscopía Electrónica de Rastreo
3.
J Cancer Res Ther ; 16(3): 612-618, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32719276

RESUMEN

Objective: The objective of this study is to evaluate the effects of radiotherapy doses on mineral density and percentage mineral volume of human permanent tooth enamel. Materials and Methods: Synchrotron radiation Xray microcomputed tomography (SRµCT) and microhardness testing were carried out on 8 and 20 tooth samples, respectively. Enamel mineral density was derived from SRµCT technique using ImageJ software. Microhardness samples were subjected to Vickers indentations followed by calculation of microhardness and percentage mineral volume values using respective mathematical measures. Data were analyzed using paired t-test at a significance level of 5%. Qualitative analysis of the enamel microstructure was done with two-dimensional projection images and scanned electron micrographs using µCT and field emission scanning electron microscopy, respectively. Results: Vickers microhardness and SRµCT techniques showed a decrease in microhardness and an increase in mineral density, respectively, in postirradiated samples. These changes were related to mineral density variation and alteration of hydroxyapatite crystal lattice in enamel surface. Enamel microstructure showed key features such as microporosities and loss of smooth homogeneous surface. These indicate tribological loss and delamination of enamel which might lead to radiation caries. Conclusions: Tooth surface loss might be a major contributing factor for radiation caries in head-and-neck cancer patients prescribed to radiotherapy. Such direct effects of radiotherapy cause enamel abrasion, delamination, and damage to the dentinoenamel junction. Suitable measures should, therefore, be worked out to protect nontarget oral tissues such as teeth while delivering effective dosages to target regions.


Asunto(s)
Esmalte Dental/efectos de la radiación , Neoplasias de Cabeza y Cuello/radioterapia , Traumatismos por Radiación/etiología , Desmineralización Dental/etiología , Esmalte Dental/ultraestructura , Dureza/efectos de la radiación , Neoplasias de Cabeza y Cuello/patología , Humanos , Técnicas In Vitro , Microscopía Electrónica de Rastreo/métodos , Traumatismos por Radiación/patología , Propiedades de Superficie , Desmineralización Dental/patología , Microtomografía por Rayos X/métodos
4.
Nature ; 583(7814): 66-71, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32612224

RESUMEN

Dental enamel is a principal component of teeth1, and has evolved to bear large chewing forces, resist mechanical fatigue and withstand wear over decades2. Functional impairment and loss of dental enamel, caused by developmental defects or tooth decay (caries), affect health and quality of life, with associated costs to society3. Although the past decade has seen progress in our understanding of enamel formation (amelogenesis) and the functional properties of mature enamel, attempts to repair lesions in this material or to synthesize it in vitro have had limited success4-6. This is partly due to the highly hierarchical structure of enamel and additional complexities arising from chemical gradients7-9. Here we show, using atomic-scale quantitative imaging and correlative spectroscopies, that the nanoscale crystallites of hydroxylapatite (Ca5(PO4)3(OH)), which are the fundamental building blocks of enamel, comprise two nanometric layers enriched in magnesium flanking a core rich in sodium, fluoride and carbonate ions; this sandwich core is surrounded by a shell with lower concentration of substitutional defects. A mechanical model based on density functional theory calculations and X-ray diffraction data predicts that residual stresses arise because of the chemical gradients, in agreement with preferential dissolution of the crystallite core in acidic media. Furthermore, stresses may affect the mechanical resilience of enamel. The two additional layers of hierarchy suggest a possible new model for biological control over crystal growth during amelogenesis, and hint at implications for the preservation of biomarkers during tooth development.


Asunto(s)
Amelogénesis , Esmalte Dental/química , Ácidos/química , Calcio/química , Carbonatos/química , Cristalización , Teoría Funcional de la Densidad , Esmalte Dental/ultraestructura , Durapatita/química , Fluoruros/química , Humanos , Magnesio/química , Microscopía Electrónica de Transmisión de Rastreo , Sodio/química , Tomografía , Difracción de Rayos X
5.
Arch Oral Biol ; 117: 104795, 2020 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-32540555

RESUMEN

OBJECTIVE: To investigate fluid flow through enamel in intact human premolars in vivo and in vitro by using the replica technique. DESIGN: The experiments were done on 17 premolars of 10 subjects (aged 10-25 yrs) to be extracted during orthodontic treatment. Teeth were divided into 2 groups. In the first group (n = 11), the fluid accumulated on the enamel surface was recorded with the impression material in the mid-buccal enamel both in vivo and in vitro. In vitro replicas were obtained when the pressure in the pulp cavity held at 0, +20, +100, and +200 mmHg. They were examined by a scanning electron microscope (SEM). For the second group (n = 10), each tooth was prepared for fluid flow measurement during which the pulpal pressures of +20, +100, +200, and +300 mmHg were applied. RESULTS: The mean number of droplets presented after the pressure had been raised to 200 mmHg is significantly greater than those observed at lower pressures, including those obtained from the same tooth in vivo. A significant linear relationship between these numbers and the pulpal pressures was found (p < 0.001). In vitro fluid conductance through the crown also increased significantly with increased pressure (p < 0.001). CONCLUSION: SEM evaluation of droplets distribution on enamel surface revealed that the presence of fluid transudation forced by pulpal pressure may influence the accumulation of enamel fluid on the tooth surface in vitro, similar to those observed in vivo.


Asunto(s)
Esmalte Dental/ultraestructura , Pulpa Dental , Adolescente , Adulto , Diente Premolar/ultraestructura , Niño , Cavidad Pulpar , Humanos , Microscopía Electrónica de Rastreo , Adulto Joven
6.
Lasers Med Sci ; 35(7): 1607-1620, 2020 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-32472426

RESUMEN

The aim of the present study was to evaluate the effects of different remineralization agents associated with erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) (0.5 W power, 20 Hz frequency, 60% water, 40% air, 25 mJ pulse energy, 8.84 J/cm2 fluence, 60 µs pulse duration, 600 µm tip diameter, and an approximate 1-1.5 mm distance to the target) laser irradiation on erosion induced by the consumption of carbonated drinks in human primary enamel. There were 8 groups and 10 primary teeth in each g0roup. The distribution was as follows: group 1, casein phosphopeptide-amorphous calcium phosphate with fluoride (CPP-ACPF); group 2, Er,Cr:YSGG laser+CPP-ACPF; group 3, fluor varnish; group 4, Er,Cr:YSGG Laser+fluoride varnish; group 5, ROCS® medical mineral gel; group 6, Er,Cr:YSGG laser + ROCS® medical mineral gel; group 7, Er,Cr:YSGG laser; and group 8, artificial saliva. The samples in the groups were submerged in artificial saliva and acid twice a day for 6 s at 6-h intervals and were then exposed to an erosion cycle 15 times. In the groups in which the Er,Cr:YSGG laser was applied in combination with the remineralization agents, the laser application was made first, and then the remineralization agents were applied for 4 min in each group. The Friedman and Wilcoxon signed-rank tests and the Bonferroni correction were used in statistical analyses, and the significance level was taken as p < 0.05. According to the results, all agents had a statistically significant difference (groups 1, 2, 3, 4, and 6: p = 0.005, p < 0.017; groups 5 and 7: p = 0.007, p < 0.017) between BL-RM periods. However, all agents had a statistically significant remineralization effect on primary teeth enamel (groups 1, 2, 3, 6, and 7: p = 0.005, p < 0.017; group 4: p = 0.011, p < 0.017) except that group 5 (p = 0.074, p < 0.017) between DM-RM periods. The coadministration of an agent with the laser did not make any difference at a statistical level (p = 0.804, p > 0.05). The results were supported by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. As a result of this study, CPP-ACPF had a notable impact in terms of the remineralization effect on eroded enamel, and the Er,Cr:YSGG laser alone may be an alternative method, which may be related to the modified hydroxyapatite structure, 38.5% H0.56Ca4.56O13P3Y0.44, that was determined in XRD analysis.


Asunto(s)
Esmalte Dental/efectos de la radiación , Láseres de Estado Sólido/uso terapéutico , Erosión de los Dientes/cirugía , Remineralización Dental , Diente Primario/efectos de la radiación , Esmalte Dental/ultraestructura , Dureza , Humanos , Difracción de Rayos X
7.
Arch Oral Biol ; 112: 104682, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32126356

RESUMEN

OBJECTIVE: The aim of this study was to determine the heterogeneity in chemical composition of bovine enamel using atom probe tomography, and thereby evaluate the suitability of bovine enamel as a substitute for human enamel in in vitro dental research. DESIGN: Enamel samples from extracted bovine incisor teeth were first sectioned using a diamond saw and then milled into needle-like samples (<100 nm diameter) by focused ion beam (FIB) coupled with a scanning electron microscope (SEM). These samples were analyzed in the atom probe to acquire three-dimensional (3D) images and quantify the atomic chemistry and distribution in bovine enamel. RESULTS: For the first time, the atomic-level composition and clustering of major constituents and impurities within bovine enamel were determined and imaged. We discovered that the chemical composition of bovine enamel is spatially inhomogeneous at the atomic scale. The average bulk Ca/P ratio, ∼1.4, was in agreement with previously reported literature values from alternative conventional methods. When assessed locally at the atomic scale, the Ca/P ratio varied between 1.1 and 2.03. We also discovered that the Mg impurities were significantly segregated throughout the enamel, and such clustering influenced the variation of Ca/P ratios. The increase in Mg concentrations, near the Mg clusters, correlated with increased Ca and decreased P concentrations. CONCLUSION: The presented findings of variability in local composition should be taken into account when interpreting dental research results from bovine enamel.


Asunto(s)
Esmalte Dental/ultraestructura , Tomografía , Animales , Bovinos , Incisivo , Microscopía Electrónica de Rastreo
8.
Lasers Med Sci ; 35(5): 1213-1222, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32030555

RESUMEN

The aim of this in vitro study was to evaluate the protective effect of short-pulsed CO2 9.3 µm laser irradiation against erosion in human enamel without and combined with TiF4 and AmF/NaF/SnCl2 applications, respectively, as well as compared to the protective effect of these fluoride treatments alone. After polishing, ninety enamel samples (3 × 3mm) were used for 9 different treatment groups: 4% TiF4 gel (pH 1.5, 24,533 ppm F-); AmF/NaF/SnCl2 rinse (pH 4.5; 500 ppm F-, 800 ppm Sn2); CO2 laser (average power 0.58 W); CO2 laser (0.58 W) + TiF4; CO2 laser (0.58 W) + AmF/NaF/SnCl2; CO2 laser (0.69 W); CO2 laser (0.69 W) + TiF4; CO2 laser (0.69 W) + AmF/NaF/SnCl2; negative control (deionized water). TiF4 gel was brushed on only once before the first erosive cycling, while samples treated with AmF/NaF/SnCl2 were daily immersed in 5 ml of the solution before cycling. Laser treatment occurred with a CO2 laser (wavelength 9.3 µm, pulse repetition rate 100 Hz, pulse duration 14.6 µs/18 µs, average power 0.58 W/0.69 W, fluence 1.9 J/cm2/2.2 J/cm2, beam diameter 0.63 mm, irradiation time 10 s, air cooling). TiF4 was applied only once, while AmF/NaF/SnCl2 was applied once daily before the erosive challenge. Surface loss (in µm) was measured with optical profilometry immediately after treatment, and after 5 and 10 days of erosive cycling (0.5% citric acid, pH 2.3, 6 × 2 min/day). Additionally, scanning electron microscopy investigations were performed. All application measures resulted in loss of surface height immediately after treatment. After 5 days, significantly reduced surface loss was observed after applying laser irradiation (both power settings) followed by applications of TiF4 or AmF/NaF/SnCl2 solution (p < 0.05; 2-way ANOVA and Tukey test) compared to fluoride application alone. After 10 days, compared to after 5 days, a reduced tissue loss was observed in all groups treated with AmF/NaF/SnCl2 solution. This tissue gain occurred with the AmF/NaF/SnCl2 application alone and was significantly higher when the application was combined with the laser use (p < 0.05). Short-pulsed CO2 9.3 µm laser irradiation followed by additional application of AmF/NaF/SnCl2 solution significantly reduces the progression of dental enamel erosion in vitro.


Asunto(s)
Esmalte Dental/patología , Esmalte Dental/efectos de la radiación , Fluoruros/uso terapéutico , Láseres de Gas/uso terapéutico , Erosión de los Dientes/cirugía , Esmalte Dental/ultraestructura , Humanos , Compuestos de Estaño/uso terapéutico
9.
Lasers Med Sci ; 35(5): 1193-1203, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32006264

RESUMEN

This study investigated the combined effect of CO2 laser irradiation and Remin Pro paste on microhardness of enamel white spot lesions (WSLs). Seventy-eight intact premolars were randomly assigned into six groups and then stored in a demineralizing solution to create WSLs. Afterwards, the teeth in group 6 (negative control) remained untreated, while groups 1 and 4 were exposed to CO2 laser irradiation (20 Hz, 1 W, 30 s) and Remin Pro paste, respectively. In groups 2 and 3, the teeth were exposed to laser either before (group 2) or after (group 3) Remin Pro application. The teeth in groups 1 to 5 were then immersed in artificial saliva for 90 days while subjected to fluoride mouthwash and weekly brushing. Finally, the teeth were sectioned, and Vickers microhardness was measured at the enamel surface and at 50, 100, and 150 µm from the surface. One sample of each group was also examined with scanning electron microscope (SEM). Data were analyzed by two-way analysis of variance (ANOVA) and Tukey's test. The significance was set at 0.05. Laser irradiation followed by Remin Pro application (group 2) caused a significant increase in total WSLs' microhardness compared with laser alone (group 1) and control groups (P < 0.05). Microhardness at depths of 100 and 150 µm was also significantly greater in group 2 compared with those of group 3 and control groups (P < 0.05). Combined application of CO2 laser with Remin Pro paste, when laser is irradiated before the paste, is suggested for re-hardening of WSLs in deep layers of enamel.


Asunto(s)
Caries Dental/cirugía , Esmalte Dental/patología , Esmalte Dental/efectos de la radiación , Láseres de Gas/uso terapéutico , Pastas de Dientes/uso terapéutico , Esmalte Dental/ultraestructura , Dureza , Humanos
10.
Lasers Med Sci ; 35(3): 709-718, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-31713778

RESUMEN

The potential anti-cariogenic effect of blue light was evaluated using an oral biofilm model. Two species, Streptococcus mutans and Streptococcus sanguinis, were cultivated ex vivo on bovine enamel blocks for 24 h, either separately or mixed together, then exposed to blue light (wavelengths 400-500 nm) using 112 J/cm2. Twenty four or 48 h after exposure to light the biofilm structure and biomass were characterized and quantified using SEM and qPCR, respectively. Bacterial viability was analyzed by CLSM using live/dead bacterial staining. Gene expression was examined by RT-qPCR. After exposure to light, S. mutans biomass in mono-species biofilm was increased mainly by dead bacteria, relative to control. However, the bacterial biomass of S. mutans when grown in mixed biofilm and of S. sanguinis in mono-species biofilm was reduced after light exposure, with no significant change in viability when compared to control. Furthermore, when grown separately, an upregulation of gene expression related to biofilm formation of S. mutans, and downregulation of similar genes of S. sanguinis, were measured 24 h after exposure to blue light. However, in mixed biofilm, a downregulation of those genes in both species was observed, although not significant in S. mutans. In conclusion, blue light seems to effectively alter the bacterial biomass by reducing the viability and virulence characteristics in both bacterial species and may promote the anti-cariogenic balance between them, when grown in a mixed biofilm. Therefore, exposure of oral biofilm to blue light has the potential to serve as a complementary approach in preventive dentistry.


Asunto(s)
Biopelículas/efectos de la radiación , Luz , Modelos Biológicos , Boca/microbiología , Streptococcus mutans/efectos de la radiación , Streptococcus sanguis/efectos de la radiación , Animales , Biopelículas/crecimiento & desarrollo , Bovinos , Esmalte Dental/microbiología , Esmalte Dental/ultraestructura , Regulación Bacteriana de la Expresión Génica/efectos de la radiación , Streptococcus mutans/genética , Streptococcus mutans/ultraestructura , Streptococcus sanguis/genética , Streptococcus sanguis/ultraestructura
11.
Braz. dent. sci ; 23(3): 1-11, 2020. tab, ilus
Artículo en Inglés | LILACS, BBO - Odontología | ID: biblio-1116331

RESUMEN

Objective: To compare the remineralization potential of theobromine and sodium fluoride gels on artificial caries like lesion. Materials and Methods: Forty longitudinal halves of human mandibular premolars were equally divided into 4 groups of 10 samples each: control group (C), samples were stored in distilled water during the experiment period. The remaining 30 specimens were subjected to demineralization protocol to create caries like lesions. samples were immersed for three days in a demineralization solution (pH 5.0) containing 0.2% carbopol and 0.1% lactic acid saturated with calcium phosphate tribasic. The samples were subdivided into 3 equal groups according to the treatment applied during the pH cycle. Demineralization group "D": no treatment applied. Group "F" treated with 2000 mg/liter sodium fluoride gel. Group "T" treated with 200 mg/liter theobromine gel. The specimens of the two studies groups were subjected to Demineralization- Remineralization PH Cycle Protocol for 5 days (Alternating four steps: 1: Treatment material, fluoride or theobromine ˜= 3 minutes. 2: Demineralizing solution 3 hours. 3: treatment material ˜= 3 minutes. 4: Remineralizing solution till the next cycle). The samples were investigated by scanning electron microscope (SEM) and energy dispersive x-ray analysis (EDXA). Results: The enamel of the demineralization group was porous with artificial caries like changes exposing the subsurface enamel rods with severe rod core defects. Theobromine gel and fluoride gel groups showed marked improvement in the surface characteristics in the enamel in both groups. Theobromine gel group showed more observable enamel surface improvement than the fluoride gel group. EDXA revealed that the calcium-phosphorus ratio displayed a descending order: (C > T > F > D). The differences between the two tested groups were not statistically significant. Conclusion: Theobromine gel had more effective remineralizing potential than fluoride gel as a result of its effect in improving the enamel surface characteristics of human teeth. (AU)


Objetivo: Comparar o potencial de remineralização dos géis de teobromina e fluoreto de sódio em lesões de cáries artificiais. Materiais e Métodos: Quarenta metades longitudinais de pré-molares inferiores humanos foram igualmente divididas em 4 grupos de 10 amostras cada: grupo controle (C), as amostras foram armazenadas em água destilada durante o período do experimento. As 30 amostras restantes foram submetidas ao protocolo de desmineralização paracriar lesões artificiais de cárie. As amostras foram imersas por três dias em uma solução de desmineralização (pH 5,0) contendo 0,2% de carbopol e 0,1% de ácido lático saturado com fosfato de cálcio tribásico. As amostras foram subdivididas em 3 grupos iguais, de acordo com o tratamento aplicado durante o ciclo do pH. Grupo de desmineralização "D": nenhum tratamento aplicado. Grupo "F" tratado com 2000 mg / litro de fluoreto de sódio em gel. Grupo & quot;T &q uot; tratado com 200 mg / litro de gel de teobromina. As amostras dos dois grupos de estudo foram submetidas ao protocolo de ciclo de desmineralização - remineralização por 5 dias (quatro etapas alternativas: 1: material de tratamento, flúor ou teobromina ˜= 3 minutos. 2: solução desmineralizante 3 horas. 3: material de tratamento ˜= 3 minutos 4: Solução de remineralização até o próximo ciclo). As amostras foram investigadas por microscopia eletrônica de varredura(MEV) e análise de raios-x dispersivos de energia (EDXA). Resultados: O esmalte do grupo de desmineralização era poroso, com cáries artificiais, como alterações que expunham as hastes de esmalte do subsolo com graves defeitos no núcleo da haste. Os grupos gel de teobromina e flúor apresentaram melhora acentuada nas características da superfície do esmalte nos dois grupos. O grupo gel de teobromina mostrou uma melhoria na superfície do esmalte mais observável do que o grupo gel de fluoreto. A EDXA revelou que a razão cálcio-fósforo exibia uma ordem decrescente: (C> T> F> D). As diferenças entre os dois grupos testados não foram estatisticamente significantes. Conclusão: O gel de teobromina teve um potencial remineralizante mais eficaz que o gel de flúor como resultado de seu efeito na melhoria das características da superfície do esmalte dos dentes humanos. (AU)


Asunto(s)
Humanos , Fluoruro de Sodio/uso terapéutico , Teobromina/uso terapéutico , Caries Dental , Esmalte Dental/ultraestructura , Pruebas de Dureza , Microscopía
12.
Int J Mol Sci ; 22(1)2020 Dec 29.
Artículo en Inglés | MEDLINE | ID: mdl-33383975

RESUMEN

A series of linear profiles of the elements of the enamel in human molar teeth were made with the use of an electron microprobe and a Raman microscope. It is postulated that the enamel can be treated as the superposition of variable "overbuilt" enamel on the stable "core" enamel at the macro-, micro- and nanoscale level. The excessive values characterize the "overbuilt enamel". All the profiles of excessive parameters along the enamel thickness from the enamel surface to the dentin enamel junction (DEJ) can be approximated very precisely with the use of exponential functions, where Ca, P, Cl and F spatial profiles are decaying while Mg, Na, K and CO32- ones are growing distributions. The "overbuilt" apatite formed on the boundary with DEJ, enriched in Na, Mg, OH and carbonates, reacts continuously with Ca, Cl and F, passing into an acid-resistant form of the "overbuilt" enamel. The apparent phases arriving in boundary regions of the "overbuilt enamel" were proposed. Microdiffraction measurements reveal relative variation of energy levels during enamel transformations. Our investigations are the milestones for a further new class of biomaterial and nanomaterial development for biomedical applications.


Asunto(s)
Materiales Biocompatibles/química , Esmalte Dental/química , Nanoestructuras/química , Diente/química , Fenómenos Químicos , Esmalte Dental/ultraestructura , Humanos , Fenómenos Mecánicos , Modelos Químicos , Diente/ultraestructura , Difracción de Rayos X
13.
Biomed Res Int ; 2019: 9101642, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31781651

RESUMEN

Objective: This in vitro study is aimed at investigating the caries preventive effectiveness of 445 nm diode laser in combination with topical fluoridation. Materials and methods: A total of 30 caries-free bovine teeth were used in this study. Eighteen teeth were covered with nail varnish except four windows on the labial surface. The windows were assigned to no treatment/control (C), laser (L) (0.3 W, 60 s, and 90 J/cm2), fluoride (F), and fluoride followed by laser (FL) treatment groups. Artificial caries lesions were created, and the teeth were sectioned and investigated under polarized light microscopy for quantitative measurement of the resulted lesion depth. Ten teeth were used for surface temperature measurement and two teeth for scanning electron microscopy (SEM). Extra twelve human molars were used for the intrapulpal temperature measurement. The absorbance of fluoride at 445 nm was measured. Results: The means of lesion depth for the C, L, F, and FL groups were 123.48 (±21.93), 112.33 (±20.42), 99.58 (±30.68), and 89.03 (±30.38) µm, respectively. The pairwise differences of the L, F, and FL groups compared with the C group were significant (p < 0.05). The differences between groups were tested: FL versus L p=0.02, F versus L p=0.16, and FL versus F p=0.91, and the difference of the F versus FL was not significant (p=0.91). Temperature increment at the enamel surface and pulp roof were ∆T = 16.67 (±4.11) and 2.12 (±0.66)°C, respectively. The topical fluoride absorbance at 445 nm is five orders higher than that at 810 nm. SEM shows that after laser irradiation the enamel surface was intact and without thermal damage. Conclusions: The 445 nm laser irradiation may be useful for caries prevention, and its effectiveness is lower than those previously achieved using the argon ion laser.


Asunto(s)
Caries Dental/prevención & control , Fluoruros Tópicos/uso terapéutico , Láseres de Semiconductores/uso terapéutico , Terapia por Luz de Baja Intensidad , Animales , Bovinos , Caries Dental/tratamiento farmacológico , Caries Dental/radioterapia , Susceptibilidad a Caries Dentarias , Esmalte Dental/ultraestructura , Pulpa Dental/ultraestructura , Humanos , Microscopía Electrónica de Rastreo , Microscopía de Polarización , Diente Molar/ultraestructura , Temperatura , Diente/ultraestructura
14.
BMC Oral Health ; 19(1): 247, 2019 11 14.
Artículo en Inglés | MEDLINE | ID: mdl-31727047

RESUMEN

BACKGROUND: The aim of the present investigation was to evaluate enamel reduction efficiency, abrasive property decay, and enamel effects between oscillating mechanical and manual systems for interproximal enamel reduction (IPR). METHODS: Three oscillating strips and three manual strips were tested on twelve freshly extracted premolars blocked in an acrylic cylinder pot by means of a material testing machine. Each strip underwent one test of 8 cycles (30 s each). Both abrasive tracks and teeth surfaces were qualitative evaluated before and after IPR by means of SEM analysis. Efficiency and abrasive property decay of both IPR systems were investigated by the amount of enamel reduction within the eight-cycle testing. Independent t-test was used to evaluate differences in variables between the two systems. RESULTS: Mechanical IPR system showed higher efficiency in terms of enamel reduction (p < 0.005) when compared with manual IPR system (0.16 mm and 0.09 mm, respectively). Quantity of removed enamel decreased throughout the 8 cycles for both systems. Less presence of enamel debris and detachment of abrasive grains were observed on mechanical strips rather than manual strips. SEM analysis revealed more regular surface of teeth undergone mechanical IPR procedures. CONCLUSION: Oscillating diamond strips showed more controlled efficiency when compared with the manual IPR system leading to a more regular enamel surface.


Asunto(s)
Esmalte Dental/efectos de los fármacos , Diamante , Microabrasión del Esmalte/métodos , Diente Premolar , Esmalte Dental/patología , Esmalte Dental/ultraestructura , Microabrasión del Esmalte/instrumentación , Humanos , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Propiedades de Superficie
15.
Nan Fang Yi Ke Da Xue Xue Bao ; 39(9): 1113-1117, 2019 Sep 30.
Artículo en Chino | MEDLINE | ID: mdl-31640964

RESUMEN

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/cm3 and 1.72±0.07 g/cm3, 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.


Asunto(s)
Porcinos Enanos , Diente Primario/anatomía & histología , Animales , Esmalte Dental/ultraestructura , Pulpa Dental , Dentina/ultraestructura , Porcinos , Tibet , Germen Dentario
16.
Int Orthod ; 17(4): 744-757, 2019 12.
Artículo en Inglés | MEDLINE | ID: mdl-31543426

RESUMEN

BACKGROUND DATA: Enamel microcrack formation has a high incidence after mechanical debonding of ceramic brackets. This may be due to high delivered shear bond strength values when enamel is priorly etched by phosphoric acid. It is still not well elucidated in the literature if laser etching affects enamel the same way. The aim of the research was to analyze different Er,Cr:YSGG and Er:YAG laser etching settings as an alternative to phosphoric acid, in an attempt to prevent enamel microcrack formation during laser etching and mechanical debonding, while reducing the shear bond strength to the minimal clinical acceptable value. MATERIALS AND METHODS: One hundred and thirty-three teeth were randomly divided into 7 experimental groups according to their etching modalities. Settings used for enamel etching were in Er,Cr:YSGG groups: Er,Cr:YSGG (1.5Watt, W/20Hertz, Hz); Er,Cr:YSGG (1.5W/15Hz) and Er,Cr:YSGG (2W/20Hz) and settings used for enamel etching in Er:YAG groups were: Er:YAG (60 millijoules, mJ), Er:YAG (80mJ) and Er:YAG (100mJ). Group C etched with 37% phosphoric acid served as control. Microscopic analysis was performed to assess presence of enamel microcracks. Shear bond strength was evaluated after thermocycling using Weibull survival analysis. RESULTS: All groups showed a reduction in additional microcracks after debonding when compared to control, but only group Er:YAG (60mJ) exhibited a statistically significant difference. Groups Er:YAG (80mJ), control and Er:YAG (100mJ) showed respectively the highest probability of survival at various stress levels followed by groups Er:YAG (60mJ); Er,Cr:YSGG (1.5W/15Hz); Er,Cr:YSGG (2W/20Hz) and Er,Cr:YSGG (1.5W/20Hz) that presented a relatively considerable risk of failure, even at low stress levels. CONCLUSIONS: When considering reduction of enamel microcrack formation and clinical acceptable shear bond strength, none of the groups succeeded both. Etching by Er:YAG (60mJ) and Er,Cr:YSGG (1.5W/15Hz), showed the least overall microcrack incidence between groups, but Er:YAG (60mJ) displayed significant reduction compared to phosphoric acid. However, etching by Er:YAG (80mJ) had the most predictable results in term of shear bond strength.


Asunto(s)
Recubrimiento Dental Adhesivo/métodos , Desconsolidación Dental/métodos , Esmalte Dental , Grabado Dental/métodos , Soportes Ortodóncicos , Resistencia al Corte , Fracturas de los Dientes/patología , Grabado Ácido Dental , Cerámica , Esmalte Dental/ultraestructura , Análisis del Estrés Dental , Humanos , Láseres de Estado Sólido , Ensayo de Materiales , Ácidos Fosfóricos , Análisis de Regresión , Propiedades de Superficie
17.
Nat Commun ; 10(1): 4383, 2019 09 26.
Artículo en Inglés | MEDLINE | ID: mdl-31558712

RESUMEN

Enamel is the hardest and most resilient tissue in the human body. Enamel includes morphologically aligned, parallel, ∼50 nm wide, microns-long nanocrystals, bundled either into 5-µm-wide rods or their space-filling interrod. The orientation of enamel crystals, however, is poorly understood. Here we show that the crystalline c-axes are homogenously oriented in interrod crystals across most of the enamel layer thickness. Within each rod crystals are not co-oriented with one another or with the long axis of the rod, as previously assumed: the c-axes of adjacent nanocrystals are most frequently mis-oriented by 1°-30°, and this orientation within each rod gradually changes, with an overall angle spread that is never zero, but varies between 30°-90° within one rod. Molecular dynamics simulations demonstrate that the observed mis-orientations of adjacent crystals induce crack deflection. This toughening mechanism contributes to the unique resilience of enamel, which lasts a lifetime under extreme physical and chemical challenges.


Asunto(s)
Amelogénesis , Esmalte Dental/ultraestructura , Tercer Molar/ultraestructura , Cristalización , Esmalte Dental/metabolismo , Humanos , Microscopía Electrónica de Rastreo , Microscopía Electrónica de Transmisión , Tercer Molar/metabolismo , Simulación de Dinámica Molecular , Adulto Joven
18.
Microsc Res Tech ; 82(11): 1884-1890, 2019 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-31400189

RESUMEN

Determining surface topography of different tissues of the molar tooth with novel analytical methods has opened new horizons in dental surface measurements which characterize tooth surface quality in dentistry. Studying surface topological measurements and comparing surface morphology of hard tissue of the molar tooth are the ultimate goals of the present study. Ten molar teeth have been chosen for investigating their surface characteristics through image processing techniques. The power spectral density (PSD) and fast Fourier transform algorithms of every molar tooth containing enamel, dentin, and cementum have determined that the characterization of surface profiles is possible. As can be seen, PSD along with fractal dimensions leads to good results for teeth surface topography. Moreover, PSD angular plot assures appropriate description of surface.


Asunto(s)
Cemento Dental/ultraestructura , Esmalte Dental/ultraestructura , Dentina/ultraestructura , Fractales , Diente Molar/ultraestructura , Adulto , Cristalografía por Rayos X , Análisis de Fourier , Dureza/fisiología , Humanos , Masculino , Microscopía de Fuerza Atómica , Diente Molar/diagnóstico por imagen , Propiedades de Superficie
19.
Dokl Biol Sci ; 486(1): 79-82, 2019 May.
Artículo en Inglés | MEDLINE | ID: mdl-31317450

RESUMEN

In small mammals, the degree of micro- and mesowear of molars depends on the feed hardness, abrasiveness, and some other characteristics. Analysis of micro- and mesorelief of the paleontological material is used for reconstruction of some animal diet parameters. Small mammals pass through a series of complex transformations on the way from the objects of biocenosis to paleontological objects. Bone remains underwent transformations during accumulation and fossilization. In particular, bone remains from ornithogenous deposits were exposed to the bird digestive system elements. We have experimentally studied changes in some parameters of the narrow-headed vole (Microtus gregalis) molars derived from the owl pellets. Comparison of the same samples before and after exposure to the digestive system of the polar owl (Nyctea scandiaca) and eagle owl (Bubo bubo) showed that the tooth enamel microrelief undergoes serious changes and therefore, provides no information on the intravital diet of voles. A different degree of preservation of the characteristics of the mesorelief was shown. Depending on this, an assessment of their applicability to paleoreconstructions was given.


Asunto(s)
Arvicolinae/anatomía & histología , Esmalte Dental/ultraestructura , Dieta , Diente Molar/anatomía & histología , Estrigiformes/fisiología , Animales , Arvicolinae/fisiología , Conducta Alimentaria
20.
Microsc Res Tech ; 82(10): 1668-1680, 2019 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-31259458

RESUMEN

The study aimed at finding an optimal combination of acid concentration and etching time when nitric acid is used as etchant for the study of the finer details of human dental enamel structure. Four hundred 2-3-mm-thick segments of facio-lingually sectioned human third molar crowns were assigned to 20 groups with 20 specimens in each group, each group differing with respect to acid concentration (0.1, 1, 2.5, and 5%) and etching time (15, 30, 45, 90, and 180 s). After etching and preparation, specimens were observed in the scanning electron microscope (SEM). Surface roughness/topography increased with increasing acid concentration and increasing etching time, but not in a linear fashion; generally, prisms tended to go from flat-surfaced to cone-shaped and prism sheaths from fissure-like to wedge-shaped. Intragroup variations and intergroup similarities were considerable. The two major enamel factors determining the etch effect are crystal orientation and prism sheath properties. Other factors, such as distribution of porosities and crystal quality, also contribute probably. Slight to moderate topography is best for observing the finer enamel structure, for example, etching with concentrations in the range 0.1-1% and with etching times in the range 15-90 s, the stronger the acid, the shorter the time. The depth effect of nitric acid is judged to be relatively small. Considerable variations in expression of prism cross-striations were observed. SEM observations of acid-etched enamel in carefully selected planes are a powerful method for the study of enamel structure, bearing in mind the artifactual aspects of the observed surface.


Asunto(s)
Ácidos/metabolismo , Esmalte Dental/ultraestructura , Grabado Dental/métodos , Humanos , Microscopía Electrónica de Rastreo , Diente Molar/ultraestructura , Propiedades de Superficie , Factores de Tiempo
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