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1.
PLoS One ; 15(3): e0229595, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32119700

RESUMO

OBJECTIVES: To assess and compare the enamel surface quality after interproximal enamel reduction (IPR) was performed with different systems and to study the relation between acid penetration depth and enamel surface quality as well as the importance of remineralization. METHODS: Sixty-five extracted teeth were randomly allocated to five experimental groups: untreated control, manual with New Metal Strips, mechanical with oscillating segment (OS) discs, Safe-Tipped Bur Kit, and the Ortho-Strip, followed by 30 s of polishing with the Softflex system and the Compo-system after treating the tooth with OS discs. Mesial surfaces were demineralized for 24 h and distal surfaces were subjected to interchanging demineralization and remineralization cycles of 24 h each for 18 days. The analysis was carried out by profilometry, scanning electron microscopy, and polarization microscopy. RESULTS: After IPR and polishing, enamel roughness was reduced for all systems tested except for the Essix Safe-Tipped Bur Kit. Subsequent demineralization increased enamel roughness in all groups except controls beyond the original level prior to IPR except for IPR with New Metal Strips or Ortho-Strips and subsequent polishing. Cyclic demineralization and remineralization for 18 days yielded a reduction in acid penetration depth and an increase in surface smoothness, which correlated with each other only for controls and treatment with New Metal Strips or Ortho-Strips. CONCLUSIONS: Manual IPR, using New Metal Strips and, even more, the oscillating IPR system Ortho-Strips, yielded smoother interproximal enamel surfaces and less acid penetration depth than the IPR systems with OS discs and the Safe-Tipped Bur Kit after polishing and 18 days of cyclic demineralization and remineralization. Irrespective of the IPR procedure, proper remineralization of IPR-treated surfaces is advisable to reduce caries susceptibility.


Assuntos
Esmalte Dentário/fisiologia , Corrosão Dentária/métodos , Humanos , Microscopia Eletrônica de Varredura , Microscopia de Polarização , Propriedades de Superfície , Dente/fisiologia
2.
Sci Adv ; 5(8): eaax3250, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31489378

RESUMO

Nursing is pivotal in the social and biological evolution of hominins, but to date, early-life behavior among hominin lineages is a matter of debate. The calcium isotopic compositions (δ44/42Ca) of tooth enamel can provide dietary information on this period. Here, we measure the δ44/42Ca values in spatially located microsized regions in tooth enamel of 37 South African hominins to reconstruct early-life dietary-specific variability in Australopithecus africanus, Paranthropus robustus, and early Homo. Very low δ44/42Ca values (<-1.4‰), indicative of milk consumption, are measured in early Homo but not in A. africanus and P. robustus. In these latter taxa, transitional or adult nonmilk foods must have been provided in substantial quantities relative to breast milk rapidly after birth. The results suggest that early Homo have continued a predominantly breast milk-based nursing period for longer than A. africanus and P. robustus and have consequently more prolonged interbirth interval.


Assuntos
Comportamento Animal/fisiologia , Isótopos de Cálcio/metabolismo , Cálcio/metabolismo , Hominidae/metabolismo , Hominidae/fisiologia , Animais , Evolução Biológica , Esmalte Dentário/metabolismo , Esmalte Dentário/fisiologia , Dieta/métodos , Fósseis , África do Sul , Dente/metabolismo , Dente/fisiologia
3.
Integr Comp Biol ; 59(6): 1681-1689, 2019 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-31318032

RESUMO

Dental functional morphology, as a field, represents a confluence of materials science and biology. Modern methods in materials testing have been influential in driving the understanding of dental tissues and tooth functionality. Here we present a review of dental enamel, the outermost tissue of teeth. Enamel is the hardest biological tissue and exhibits remarkable resilience even when faced with a variety of mechanical threats. In the light of recent work, we progress the argument that the risk of mechanical degradation across multiple scales exhibits a strong and continued selection pressure on the structural organization of enamel. The hierarchical nature of enamel structure presents a range of scale-dependent toughening mechanisms and provides a means by which natural selection can drive the specialization of this tissue from nanoscale reorganization to whole tooth morphology. There has been much learnt about the biomechanics of enamel recently, yet our understanding of the taxonomic diversity of this tissue is still lacking and may form an interesting avenue for future research.


Assuntos
Esmalte Dentário/anatomia & histologia , Mastigação , Dente/anatomia & histologia , Animais , Esmalte Dentário/fisiologia , Humanos , Ciência dos Materiais , Dente/fisiologia
4.
Mater Sci Eng C Mater Biol Appl ; 100: 354-362, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30948071

RESUMO

Natural bio-ceramics have attracted extensive interests due to its high strength and high toughness, which can hardly be achieved in artificial ceramics simultaneously. In this work, the microstructure and properties of the wild boar's tusk enamel were investigated. The enamel was found to exhibit a hierarchical structure ranging from the hydroxyapatite (HAP) fibers (single or poly-crystals, nano-scale), enamel rods (micro-scale), enamel types (meso-scale) to enamel patterns (macro-scale). It is worth mentioning that the high-density and high-order hierarchical nanotwins were observed in the HAP fibers. The mechanical properties of the wild boar's tusk enamel showed strong anisotropy and were higher along the longitudinal direction than along the transverse direction. The mechanical properties varied from the dentin-enamel junction (DEJ) to the outer surface. The elastic modulus increased with the distance from the DEJ and then kept invariant. The nano-hardness increased in inner enamel but decreased in outer enamel. There was a peak of nano-hardness in inner enamel area. The fracture toughness showed an opposite tendency. It exhibited high values in inner enamel, but fell in the outer enamel zone. The irregular, decussating texture of the enamel, as well as the nanotwins/hierarchical nanotwins was considered as the main reason for its excellent mechanical properties. These unique structures of the wild boar's tusk enamel are expected to cast light on the design of medical materials and provide some guidelines to improve their mechanical properties.


Assuntos
Esmalte Dentário/anatomia & histologia , Esmalte Dentário/fisiologia , Sus scrofa/anatomia & histologia , Animais , Fenômenos Biomecânicos , Esmalte Dentário/ultraestrutura , Módulo de Elasticidade , Dureza , Nanopartículas/química , Nanopartículas/ultraestrutura , Difração de Raios X
5.
J Contemp Dent Pract ; 19(10): 1181-1188, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-30498172

RESUMO

AIM: To compare the effect of nano-hydroxyapatite (9000 ppm F) and casein phosphopeptide-amorphous calcium phosphate fluoride (900 ppm F) pastes on initial enamel carious lesions of young permanent teeth. MATERIALS AND METHODS: Sixty extracted young premolars with a standardized window on enamel were immersed in a demineralizing solution for 48 hours to produce subsurface enamel lesions. They were divided into three groups according to remineralizing agents (n = 20) group I: nano-hydroxyapatite paste; group II: casein phosphopeptide-amorphous calcium phosphate fluoride paste; and group III: control (without an agent). The enamel surface microhardness (SMH) was measured at baseline, after the incipient enamel lesion, and after treatment. Additional twenty young premolars were selected and prepared as mentioned above for surface morphology evaluation by scanning electron microscope (SEM). RESULTS: No significant difference was found in mean surface microhardness in teeth treated with nano-hydroxyapatite paste and those treated with casein phosphopeptide-amorphous calcium phosphate fluoride p = 0.26. SEM showed improvement in surface defects of demineralized enamel in the two test groups. CONCLUSION: Nano-hydroxyapatite and casein phosphopeptide-amorphous calcium phosphate fluoride pastes were effec -tive in rehardening the initial enamel caries lesions in young permanent teeth. CLINICAL SIGNIFICANCE: The best strategy for caries management is to focus on the methods of improving the reminer-alization process with the aid of the remineralizing agents. The current study compared the remineralizing effect of two remineralizing agents. Within the limitations of the study, both remineralizing agents were effective for remineralization of early caries-like lesions.


Assuntos
Dente Pré-Molar/fisiologia , Caseínas/farmacologia , Colágeno/farmacologia , Esmalte Dentário/fisiologia , Durapatita/farmacologia , Calcificação de Dente/efeitos dos fármacos , Remineralização Dentária/métodos , Caseínas/administração & dosagem , Colágeno/administração & dosagem , Cárie Dentária/fisiopatologia , Esmalte Dentário/efeitos dos fármacos , Esmalte Dentário/ultraestrutura , Durapatita/administração & dosagem , Dureza , Humanos , Técnicas In Vitro , Microscopia Eletrônica de Varredura , Pomadas , Propriedades de Superfície
6.
Biomed Tech (Berl) ; 63(5): 595-602, 2018 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-30144381

RESUMO

The detection of the beginning demineralization process of dental hard tissue remains a challenging task in dentistry. As an alternative to bitewing radiographs, optical and spectroscopic technologies showed promising results for caries diagnosis. The aim of the present work is to give an overview of optical and spectroscopic properties of healthy and carious human teeth in vitro by means of Raman spectroscopy (RS), optical coherence tomography (OCT) and hyperspectral imaging (HSI). OCT was able to represent microstructural changes below the enamel surface and revealed increased scattering for white spot lesions and a white scattering trail for deeper lesions. HSI showed similar absorbance characteristics for healthy and demineralized enamel over the entire spectrum and a characteristic absorbance peak at 550 nm for discolored lesions. Already at early carious stages (white spot), we found a distinct loss of hydroxylapatite-related intensity at 959 cm-1 in demineralized regions with RS. Healthy and demineralized tooth surfaces can be distinguished at different signal levels by means of RS, OCT and HSI. The presented modalities provide additional information to the current clinical diagnosis of caries such as microstructural changes, quantification of the demineralization and imaging of caries-related chemical changes.


Assuntos
Cárie Dentária/diagnóstico , Esmalte Dentário/patologia , Esmalte Dentário/fisiologia , Minerais/análise , Tomografia de Coerência Óptica/métodos , Desmineralização do Dente/metabolismo , Esmalte Dentário/química , Humanos
7.
Zhonghua Kou Qiang Yi Xue Za Zhi ; 53(7): 470-474, 2018 Jul 09.
Artigo em Chinês | MEDLINE | ID: mdl-29996365

RESUMO

Objective: To evaluate the remineralization effect and mechanism of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) with different concentrations of fluorine on demineralized enamel using electronic probe. Methods: Extracted premolar teeth for orthodontic purpose were immersed into lactic acid gel to prepare artificial white spot lesions (10 teeth in each group). Then the specimens were randomly assigned to three groups: Control group, with 5% of the CPP-ACP+deionized water; Group A with 5% CPP-ACP+500 mg/L F(-) and Group B with 5% CPP-ACP+900 mg/L F(-). The teeth in each group were soaked in different solutions for 4 days and then were measured using electron probe tester. The changes of contents among the three groups were compared. Results: No statistically significant difference in the percentage of fluorine was found in the control group before and after treatment (P=0.06), and the difference in the percentage of fluorine quality in the other two groups was statistically significant (P<0.05). Statistically significant difference was found between calcium oxide and phosphorus peroxide in the three groups before and after mineralization (P<0.05). The percentage change of fluorine mass in group B [(0.107±0.035)%] was significantly greater than that in group A [(0.057±0.038)%] (P<0.05), while fluorine mass in group A was significantly greater than that in control group [(0.013±0.019)%] (P<0.05). In group A and group B, the change in quality of calcium oxide and phosphorus peroxide was significantly greater than that in control group (P<0.05), while no significant difference was found between group A and group B (P>0.05). Conclusions: The addition of fluorine in CPP-ACP increased the transport and penetration of calcium, phosphorus and fluorine on enamel surface.


Assuntos
Caseínas/farmacologia , Esmalte Dentário/efeitos dos fármacos , Flúor/administração & dosagem , Remineralização Dentária/métodos , Dente Pré-Molar , Cálcio/farmacocinética , Compostos de Cálcio/farmacologia , Assistência Odontológica , Esmalte Dentário/fisiologia , Microanálise por Sonda Eletrônica/métodos , Flúor/farmacocinética , Flúor/farmacologia , Humanos , Óxidos/farmacologia , Fósforo/farmacocinética , Compostos de Fósforo/farmacologia , Distribuição Aleatória
8.
Acta Biomater ; 75: 279-286, 2018 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-29874598

RESUMO

Fossil teeth are a primary source for inferring species development via evolutionary adaptation due to their linkage to feeding ecology and well perseverance. The main working tools in such studies are bite force analysis derived from jaw musculature and lever arms and morphogenetic based on enamel thickness and occlusal surface area. Despite progress made, quantitative correlation between predictions and behavior is still lacking. We studied histological sections in varieties of extracted premolar and molar human teeth. Sections corresponding to planes intersecting tips of primary cusps as well as more random planes were considered. The results revealed a unique, conclusive link between cuspal enamel thickness dc and dentin horn angle φ, a developmental parameter which contribution to tooth functioning has been overlooked. Naturally led by design principles of corbel arches, we examined the bending stress at the horn apex due to axial cuspal loading. The results show that this dc vs. φ relationship produces a constant force causing cusp fracture PF, making the latter a viable measure of tooth resilience. A preliminary study on published sections of extinct hominin teeth showed that their dc vs. φ behavior is consistent with modern humans albeit with varying PF. Scaling BF with PF enables direct estimate of bite force from measures of dc and φ in fossil teeth, achievable nondestructively from micro-computed tomography scans. STATEMENT OF SIGNIFICANCE: The correspondence between cuspal enamel thickness and dentin horn angle in the postcanine row is a natural design here revealed for the first time. This correspondence yields constant force causing fracture at the horn apex, PF, making the latter a viable measure of tooth resilience. Scaling bite force (BF) with PF enables direct estimate of BF. The proposed mechanistic link between bite force and anatomical parameters dc and φ, expressed in a simple analytic form, offers direct, development-based expectation for examining evolutionary processes in hominins.


Assuntos
Força de Mordida , Esmalte Dentário , Dentina , Dente Molar , Esmalte Dentário/anatomia & histologia , Esmalte Dentário/fisiologia , Dentina/anatomia & histologia , Dentina/fisiologia , Humanos , Dente Molar/anatomia & histologia , Dente Molar/fisiologia
9.
J R Soc Interface ; 15(143)2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29899156

RESUMO

Eilenodontines are one of the oldest radiation of herbivorous lepidosaurs (snakes, lizards and tuatara) characterized by batteries of wide teeth with thick enamel that bear mammal-like wear facets. Unlike most reptiles, eilenodontines have limited tooth replacement, making dental longevity particularly important to them. We use both X-ray and neutron computed tomography to examine a fossil tooth from the eilenodontine Eilenodon (Late Jurassic, USA). Of the two approaches, neutron tomography was more successful and facilitated measurements of enamel thickness and distribution. We find the enamel thickness to be regionally variable, thin near the cusp tip (0.10 mm) but thicker around the base (0.15-0.30 mm) and notably greater than that of other rhynchocephalians such as the extant Sphenodon (0.08-0.14 mm). The thick enamel in Eilenodon would permit greater loading, extend tooth lifespan and facilitate the establishment of wear facets that have sharp edges for orally processing plant material such as horsetails (Equisetum). The shape of the enamel dentine junction indicates that tooth development in Eilenodon and Sphenodon involved similar folding of the epithelium but different ameloblast activity.


Assuntos
Esmalte Dentário/diagnóstico por imagem , Dinossauros , Fósseis , Herbivoria , Difração de Nêutrons , Tomografia Computadorizada por Raios X , Animais , Esmalte Dentário/fisiologia
10.
Int J Nanomedicine ; 13: 2755-2765, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29780246

RESUMO

Objective: This study investigates the effects of nano-hydroxyapatite (NHA) gel and Clinpro (CP) on remineralization potential of enamel and cementum at the cavosurface area of computer-aided design and computer-aided manufacturing ceramic restoration. Materials and methods: Thirty extracted human mandibular third molars were sectioned at 1 mm above and below the cemento-enamel junction to remove the cemento-enamel junction portions and replaced them with zirconia ceramic disks by bonding them to the crown and root portions with resin cement. The enamel and cementum with an area of 4×4 mm2 surrounding the ceramic disk was demineralized with carbopol. The demineralized surfaces were treated with either NHA or CP, while 1 group was left with no treatment. Vickers microhardness of enamel and cementum were determined before demineralization, after demineralization, and after remineralization. Analysis of variance and Tukey multiple comparisons were used to determine statistically significant differences at 95% level of confidence. Scanning electron microscopy and X-ray diffraction were used to evaluate for surface alterations. Results: The mean ± SD of Vickers microhardness for before demineralization, after demineralization, and after remineralization for enamel and cementum were 377.37±22.99, 161.95±10.54, 161.70±5.92 and 60.37±3.81, 17.65±0.91, 17.04±1.00 for the no treatment group; 378.20±18.76, 160.72±8.38, 200.08±8.29 and 62.58±3.37, 18.38±1.33, 27.99±2.68 for the NHA groups; and 380.53±25.14, 161.94±5.66, 193.16±7.54 and 62.78±4.75, 19.07±1.30, 24.46±2.02 for the CP groups. Analysis of variance indicated significant increase in microhardness of demineralized enamel and cementum upon the application of either NHA or CP (p<0.05). Post hoc multiple comparisons indicated significantly higher remineralization capability of NHA for both enamel and cementum than CP (p<0.05), as evidenced by scanning electron microscopy, indicating NHA particle deposition in the area of remineralization, and crystallinity accumulation, as indicated by X-ray diffraction. Conclusion: NHA gel and CP were capable of remineralization of the enamel and cementum. NHA was more capable in the remineralization process than CP. NHA was extremely capable in the remineralization process for enamel and cementum surrounding the margin of the computer-aided design and computer-aided manufacturing ceramic.


Assuntos
Cemento Dentário/efeitos dos fármacos , Esmalte Dentário/efeitos dos fármacos , Restauração Dentária Permanente/métodos , Durapatita/farmacologia , Remineralização Dentária/métodos , Cerâmica/química , Resinas Compostas/farmacologia , Desenho Assistido por Computador , Cemento Dentário/fisiologia , Esmalte Dentário/fisiologia , Desgaste de Restauração Dentária , Restauração Dentária Permanente/instrumentação , Géis , Humanos , Dente Molar , Dente Serotino , Selantes de Fossas e Fissuras/farmacologia , Zircônio/química
11.
PLoS One ; 13(5): e0196557, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29734362

RESUMO

This study investigated the effect of the period of use and location of intraoral appliances on enamel surface loss. This randomized, single blind in situ study was conducted in 2 crossover phases based on the period of use, in which maxillary and mandibular appliances were simultaneously worn. Bovine enamel blocks (n = 120) were randomly divided among the studied groups by surface hardness. In each phase, fifteen volunteers used one maxillary appliance and two mandibular appliances for 5 days. Erosive challenge was performed 4X/day by immersion in 0.01 M HCL for 2 minutes. In the continuous phase, the intraoral appliances were worn for 20 hours. In the intermittent phase the appliances were worn for 8 hours and 30 minutes. Enamel loss was determined profilometrically. The discomfort of use of the appliances were evaluated in a questionnaire. Data were analyzed by two-way ANOVA/Tukey's test and chi-square test (p<0.05). The maxillary appliance promoted higher enamel loss compared to the mandibular one (p<0.001). Intermittent use of appliances resulted in similar enamel loss to the continuous one (p = 0.686). All volunteers preferred to use the maxillary appliance in an intermittent regimen. The intermittent use of maxillary appliance is a simplified reliable protocol appropriated for in situ erosion studies in enamel.


Assuntos
Esmalte Dentário/efeitos dos fármacos , Esmalte Dentário/fisiologia , Aparelhos Ortodônticos/efeitos adversos , Adulto , Estudos Cross-Over , Feminino , Dureza , Humanos , Masculino , Maxila/fisiologia , Método Simples-Cego , Propriedades de Superfície , Inquéritos e Questionários , Erosão Dentária/etiologia , Erosão Dentária/prevenção & controle , Remineralização Dentária , Adulto Jovem
12.
PLoS One ; 13(4): e0194908, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29634748

RESUMO

Pteropus (flying-foxes) are a speciose group of non-echolocating large bats, with five extant Australian species and 24 additional species distributed amongst the Pacific Islands. In 2015, an injured flying-fox with unusual facial markings was found in Sydney, Australia, following severe and widespread storms. Based on an initial assessment, the individual belonged to Pteropus but could not be readily identified to species. As a consequence, four hypotheses for its identification/origin were posited: the specimen represented (1) an undescribed Australian species; or (2) a morphological variant of a recognised Australian species; or (3) a hybrid individual; or (4) a vagrant from the nearby Southwest Pacific Islands. We used a combination of morphological and both mitochondrial- and nuclear DNA-based identification methods to assess these hypotheses. Based on the results, we propose that this morphologically unique Pteropus most likely represents an unusual P. alecto (black flying-fox) potentially resulting from introgression from another Pteropus species. Unexpectedly, this individual, and the addition of reference sequence data from newly vouchered specimens, revealed a previously unreported P. alecto mitochondrial DNA lineage. This lineage was distinct from currently available haplotypes. It also suggests long-term hybridisation commonly occurs between P. alecto and P. conspicillatus (spectacled flying-fox). This highlights the importance of extensive reference data, and the inclusion of multiple vouchered specimens for each species to encompass both intraspecific and interspecific variation to provide accurate and robust species identification. Moreover, our additional reference data further demonstrates the complexity of Pteropus species relationships, including hybridisation, and potential intraspecific biogeographical structure that may impact on their management and conservation.


Assuntos
Quirópteros/genética , Quirópteros/fisiologia , DNA Mitocondrial/genética , Animais , Austrália , Teorema de Bayes , Conservação dos Recursos Naturais , DNA/química , Esmalte Dentário/fisiologia , Genes RAG-1/genética , Geografia , Funções Verossimilhança , Ilhas do Pacífico , Filogenia , Análise de Sequência de DNA , Especificidade da Espécie
13.
Dent Mater ; 34(7): 1036-1040, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29678330

RESUMO

OBJECTIVE: To investigate if Vickers microhardness of dentin and enamel correlated with acoustic velocity c(l) or acoustic reflection from the sample's top (amplitude). METHODS: Eight transversal sections of a sound human tooth were investigated with scanning acoustic microscopy (SAM) and Vickers microhardness measurements. Longitudinal acoustic velocity c(l), amplitude and microhardness MHV were evaluated and for each c(l) test point corresponding amplitude and MHV were linearly interpolated and graphically analyzed. Spearman rank order correlation (rS) was calculated (p<0.05). RESULTS: c(l) was predominantly 6100-7000ms-1 in enamel and 3800-4600ms-1 in dentin and correlated significantly with MHV with 27-420 in enamel and 20-90 in dentin (rs=0,57). Amplitudes significantly correlated with MHV, too, but even better (rs=0,77). SIGNIFICANCE: Acoustic velocity and amplitudes were appropriate to detect microhardness differences of dentin and enamel and certain value ranges of both could be assigned to certain MHV ranges. Further research is needed to differentiate more precisely between the different hard tooth tissues.


Assuntos
Esmalte Dentário/fisiologia , Esmalte Dentário/ultraestrutura , Dentina/fisiologia , Dentina/ultraestrutura , Microscopia Acústica , Testes de Dureza , Humanos , Técnicas In Vitro , Projetos Piloto
14.
Mol Genet Genomic Med ; 6(3): 339-349, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29512331

RESUMO

BACKGROUND: Dentinogenesis imperfecta (DI) is a rare debilitating hereditary disorder affecting dentin formation and causing loss of the overlying enamel. Clinically, DI sufferers have a discolored and weakened dentition with an increased risk of fracture. The aims of this study were to assess genotype-phenotype findings in three families with DI-II with special reference to mutations in the DSPP gene and clinical, histological, and imaging manifestations. METHODS: Nine patients participated in the study (two from family A, four from family B, and three from family C). Buccal swab samples were collected from all participants and extracted for genomic DNA. Clinical and radiographic examinations had been performed longitudinally, and the dental status was documented using photographic images. Four extracted and decalcified tooth samples were prepared for histological analysis to assess dysplastic manifestations in the dentin. Optical coherence tomography (OCT) was applied to study the health of enamel tissue from in vivo images and the effect of the mutation on the function and structure of the DSPP gene was analyzed using bioinformatics software programs. RESULTS: The direct DNA sequence analysis revealed three distinct mutations, one of which was a novel finding. The mutations caused dominant phenotypes presumably by interference with signal peptide processing and protein secretion. The clinical and radiographic disturbances in the permanent dentition indicated interfamilial variability in DI-II manifestations, however, no significant intrafamilial variability was observed. CONCLUSION: The different mutations in the DSPP gene were accompanied by distinct phenotypes. Enamel defects suggested deficit in preameloblast function during the early stages of amelogenesis.


Assuntos
Dentinogênese Imperfeita/genética , Dentinogênese Imperfeita/fisiopatologia , Adolescente , Adulto , Criança , Pré-Escolar , Esmalte Dentário/fisiologia , Dentina/patologia , Família , Feminino , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Mutação , Países Baixos/epidemiologia , Linhagem , Fenótipo , Análise de Sequência de DNA , Dente/patologia
15.
Med Arch ; 72(6): 425-429, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30814774

RESUMO

Introduction: Bracket bonding to porcelain has high failure rate compared to bonding to enamel. Aim: This study aimed to assess the shear bond strength (SBS) of metal brackets to porcelain using a universal adhesive. Material and Methods: In this in vitro experimental study, 40 porcelain blocks (1x1x1 cm3)were divided into four groups (n=10). The porcelain surfaces were etched with 10% hydrofluoric (HF) acid and bonded to metal brackets using Transbond XT composite and the following bonding protocols: Transbond XT bonding agent alone in group 1, silane plus Transbond XT bonding agent in group 2, silane plus universal adhesive (G-Premio bond) in group 3 and universal adhesive alone in group 4. The SBS was measured using a universal testing machine at a crosshead speed of 1 mm/minute. Fracture surfaces were evaluated under a stereo microscope, and the adhesive remnant index (ARI) scores were determined. Results: The highest and the lowest SBS values were noted in groups 3 (17.06±2.58 MPa) and 4 (9.85±4.76 MPa), respectively. Type of adhesive had no significant effect on SBS (P=0.611). However, the effect of application of silane on SBS was significant (P=0.000). Groups subjected to the application of silane showed higher SBS values than others. The mode of failure was mainly adhesive in groups 2 and 3, and adhesive and mixed in groups 1 and 4. The difference in ARI scores was statistically significant (P=0.016). Conclusion: Universal adhesive and Transbond XT were not significantly different in SBS. However, application of silane significantly increased the bond strength.


Assuntos
Condicionamento Ácido do Dente/métodos , Colagem Dentária/métodos , Esmalte Dentário/fisiologia , Porcelana Dentária/química , Colagem Dentária/instrumentação , Humanos , Técnicas In Vitro , Teste de Materiais , Braquetes Ortodônticos , Resistência ao Cisalhamento , Estresse Mecânico , Propriedades de Superfície
16.
Anat Rec (Hoboken) ; 301(5): 902-912, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29244244

RESUMO

We studied the spatio-temporal variation of mineral apposition rate (MAR) in postnatally formed coronal dentine of mandibular first molars from Soay sheep repeatedly injected with different fluorochromes. MAR declined along the cuspal to cervical crown axis, and from early to late formed dentine, that is, from the dentine at the enamel-dentine-junction (EDJ) to the dentine adjacent to the dentine-pulp-interface (DPI). Highest mean MARs (about 21 µm/day) were recorded in cuspal dentine formed in the period of 28-42 days after birth. Lowest values (<2 µm/day) were recorded in late-formed (secondary) dentine close to the DPI. The high MARs recorded in the dentine of the cuspal crown portions enable the formation of a large tooth crown within a relatively short period of less than one year. The established MARs in the dentine of the different crown portions of sheep molars will allow a precise determination of the timing of stress events affecting dentine formation. They are also helpful for devising sampling protocols in studies of trace element or stable isotope distributions in sheep dentine aimed at assessing temporal variation of incorporation into forming dentine. Such data are useful in a variety of contexts, including, for example, the exposure to pollutants and the reconstruction of husbandry practices or feeding regimes. Anat Rec, 301:902-912, 2018. © 2017 Wiley Periodicals, Inc.


Assuntos
Esmalte Dentário/fisiologia , Dentina/fisiologia , Dente Molar/fisiologia , Animais , Ovinos
17.
Dent Mater ; 34(1): 69-77, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29175159

RESUMO

OBJECTIVE: This article investigates the mechanical properties of a material with hierarchically arranged microcracks. METHODS: Hierarchically structured biomaterials such as enamel exhibit superior mechanical properties as being stiff and damage tolerant at the same time. The common mechanical explanation for this behavior is based on the hierarchically structured arrangement of hard minerals and soft organics and their cooperative deformation mechanisms. In situ mechanical experiments with mm-sized bovine enamel bending bars an scanning electron microscope reveal that enamel is able to withstand mechanical loading even if it contains microcracks on different lengths scales. To clarify this issue an analytical hierarchical microcrack model of non-interacting cracks is presented. RESULTS AND SIGNIFICANCE: The model predicts a decrease of the elastic modulus and the fracture strength with increasing levels of hierarchy. The fracture strain on the other hand may decrease or increase with the number of hierarchical levels, depending on the microcrack density. This simple hierarchical microcrack model is able to explain already published experiments with focused ion beam prepared µm-sized enamel cantilevers on different hierarchical levels. In addition it is shown that microcracking during loading in hierarchical materials may lead to substantial pseudoplastic behavior.


Assuntos
Esmalte Dentário/química , Fraturas dos Dentes/fisiopatologia , Animais , Bovinos , Força Compressiva/fisiologia , Esmalte Dentário/fisiologia , Módulo de Elasticidade , Dureza/fisiologia , Teste de Materiais , Microscopia Eletrônica de Varredura , Estresse Mecânico
18.
Int J Oral Sci ; 9(11): e3, 2017 11 22.
Artigo em Inglês | MEDLINE | ID: mdl-29165423

RESUMO

The Encouraging Novel Amelogenesis Models and Ex vivo cell Lines (ENAMEL) Development workshop was held on 23 June 2017 at the Bethesda headquarters of the National Institute of Dental and Craniofacial Research (NIDCR). Discussion topics included model organisms, stem cells/cell lines, and tissues/3D cell culture/organoids. Scientists from a number of disciplines, representing institutions from across the United States, gathered to discuss advances in our understanding of enamel, as well as future directions for the field.


Assuntos
Amelogênese , Esmalte Dentário/fisiologia , Animais , Técnicas de Cultura de Células , Linhagem Celular , Humanos , Células-Tronco/fisiologia
19.
J R Soc Interface ; 14(135)2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-29070592

RESUMO

The nanoscale responses of teeth to chewing loads are poorly understood. This has contributed to debate concerning the aetiology of enamel wear and resistance to fracture. Here we develop a new model for reactions of individual hydroxyapatite nanofibres to varying loads and directions of force. Hydroxyapatite nanofibres, or crystallites, composed of chains of bonded nanospheres, are the fundamental building blocks of enamel. This study indicates that these nanofibres respond to contact pressure in three distinct ways depending on force magnitude and direction: (i) plucking (nanosphere loss when the strength of the bonding protein 'glue' is exceeded), (ii) plastic deformation (compression to gradually bend nanofibres and squeeze the protein layer), and (iii) fragmentation (nanofibres fracture when the strength of H-bonds that bind smaller nanoparticles into nanospheres is exceeded). Critical contact pressure to initiate plucking is the lowest, followed by plastic deformation, and then fragmentation. Further, lower contact pressures are required for a response with shear forces applied perpendicular to the long axes of crystallites than with crushing forces parallel to them alone. These nanoscale responses are explained as a function of the interfacial nanochemical bonding between and within individual crystallites. In other words, nanochemistry plays a critical role in the responses of enamel to varying chewing loads.


Assuntos
Esmalte Dentário/fisiologia , Mastigação/fisiologia , Dente Molar/fisiologia , Fenômenos Biomecânicos , Força de Mordida , Humanos
20.
Comput Methods Biomech Biomed Engin ; 20(14): 1533-1542, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29063816

RESUMO

The objectives of this project were to use finite element methods to determine how changes in the elastic modulus due to oral cancer therapeutic radiation alter the distribution of mechanical stresses in teeth and to determine if observed failures in irradiated teeth correlate with changes in mechanical stresses. A thin slice section finite element (FE) model was constructed from micro CT sections of a molar tooth using MIMICS and 3-Matic software. This model divides the tooth into three enamel regions, the dentin-enamel junction (DEJ) and dentin. The enamel elastic modulus was determined in each region using nano indentation for three experimental groups namely - control (non-radiated), in vitro irradiated (simulated radiotherapy following tooth extraction) and in vivo irradiated (extracted subsequent to oral cancer patient radiotherapy) teeth. Physiological loads were applied to the tooth models at the buccal and lingual cusp regions for all three groups (control, in vitro and in vivo). The principal tensile stress and the maximum shear stress were used to compare the results from different groups since it has been observed in previous studies that delamination of enamel from the underlying dentin was one of the major reasons for the failure of teeth following therapeutic radiation. From the FE data, we observed an increase in the principal tensile stress within the inner enamel region of in vivo irradiated teeth (9.97 ± 1.32 MPa) as compared to control/non-irradiated teeth (8.44 ± 1.57 MPa). Our model predicts that failure occurs at the inner enamel/DEJ interface due to extremely high tensile and maximum shear stresses in in vivo irradiated teeth which could be a cause of enamel delamination due to radiotherapy.


Assuntos
Esmalte Dentário/fisiologia , Esmalte Dentário/efeitos da radiação , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Estresse Mecânico , Fenômenos Biomecânicos , Simulação por Computador , Esmalte Dentário/diagnóstico por imagem , Dentina/fisiologia , Dentina/efeitos da radiação , Módulo de Elasticidade , Humanos , Dente Molar/fisiologia , Dente Molar/efeitos da radiação , Resistência à Tração , Microtomografia por Raio-X
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