Comportamiento Mecánico de un Premolar Humano Sano Sometido a Fuerzas Funcionales y Disfuncionales en un MEF / Mechanical Behavior of a Healthy Human Premolar Subjected to Functional and Dysfunctional Forces in a FEM

El propósito de este estudio fue analizar el comportamiento mecánico de la estructura dental sana de un primer premolar inferior humano sometido a fuerzas funcionales y disfuncionales en diferentes direcciones. Se buscó comprender, bajo las variables contempladas, las zonas de concentración de esfuerzos que conllevan al daño estructural de sus constituyentes y tejidos adyacentes. Se realizó el modelo 3D de la reconstrucción de un archivo TAC de un primer premolar inferior, que incluyó esmalte, dentina, ligamento periodontal y hueso alveolar considerando tres variables: dirección, magnitud y área de la fuerza aplicada. La dirección fue dirigida en tres vectores (vertical, tangencial y horizontal) bajo cuatro magnitudes, una funcional de 35 N y tres disfuncionales de 170, 310 y 445 N, aplicadas sobre un área de la cara oclusal y/o vestibular del premolar que involucró tres contactos estabilizadores (A, B y C) y dos paradores de cierre. Los resultados obtenidos explican el fenómeno de combinar tres vectores, cuatro magnitudes y un área de aplicación de la fuerza, donde los valores de esfuerzo efectivo equivalente Von Mises muestran valores máximos a partir de los 60 MPa. Los valores de tensión máximos se localizan, bajo la carga horizontal a 170 N y en el proceso masticatorio en la zona cervical, cuando la fuerza pasa del 60 %. Sobre la base de los hallazgos de este estudio, se puede concluir que la reacción de los tejidos a fuerzas funcionales y disfuncionales varía de acuerdo con la magnitud, dirección y área de aplicación de la fuerza. Los valores de tensión resultan ser más altos bajo la aplicación de fuerzas disfuncionales tanto en magnitud como en dirección, produciendo esfuerzos tensiles significativos para la estructura dental y periodontal cervical, mientras que, bajo las cargas funcionales aplicadas en cualquier dirección, no se generan esfuerzos lesivos. Esto supone el reconocimiento del poder de detrimento estructural del diente y periodonto frente al bruxismo céntrico y excéntrico.

SUMMARY: The purpose of this study was to analyze the mechanical behavior of the healthy dental structure of a human mandibular first premolar subjected to functional and dysfunctional forces in different directions. It was sought to understand, under the contemplated variables, the areas of stress concentration that lead to structural damage of its constituents and adjacent tissues. The 3D model of the reconstruction of a CT file of a lower first premolar was made, which included enamel, dentin, periodontal ligament and alveolar bone considering three variables: direction, magnitude and area of the applied force. The direction was directed in three vectors (vertical, tangential and horizontal) under four magnitudes, one functional of 35 N and three dysfunctional of 170, 310 and 445 N, applied to an area of the occlusal and/or buccal face of the premolar that involved three stabilizing contacts (A, B and C) and two closing stops. The results obtained explain the phenomenon of combining three vectors, four magnitudes and an area of force application, where the values of effective equivalent Von Mises stress show maximum values from 60 MPa. The maximum tension values are located under the horizontal load at 170 N and in the masticatory process in the cervical area, when the force exceeds 60%. Based on the findings of this study, it can be concluded that the reaction of tissues to functional and dysfunctional forces varies according to the magnitude, direction, and area of application of the force. The stress values turn out to be higher under the application of dysfunctional forces both in magnitude and in direction, producing significant tensile stresses for the dental and cervical periodontal structure, while under functional loads applied in any direction, no damaging stresses are generated. This supposes the recognition of the power of structural detriment of the tooth and periodontium against centric and eccentric bruxism.

Tooth size discrepancy in different malocclusion groups in Libya: a pilot study

Background: Orthodontists need to evaluate intermaxillary tooth size discrepancy (TSD) prior to initiating treatment in order to achieve a stable treatment. Thus, the aim of the present study was to determine the prevalence of TSD in Libyan subjects among different malocclusion groups. Methods: A sample of 60 dental casts of Libyan subjects with different types of malocclusions (Class I, Class II div 1 and Class III) were included in the study. Each malocclusion group (20 dental casts) included equal numbers of males and females, 12-17 years of age. Mesio-Distal tooth measurements were extracted to compute the anterior and overall TSD ratios. Paired Student t-test was used to detect significant discrepancies between the paired teeth measurements. Analysis of Variance (ANOVA) and Tukey Honestly tests were undertaken to detect significant discrepancies among the malocclusion groups. Results: Paired t-test revealed that there were no significant discrepancies between the paired tooth widths except for the upper first molars, upper first premolars, lower lateral incisors and lower canines (P<0.010). ANOVA found no significant differences in the mean anterior TSD ratio in regard to malocclusion groups. However, a significant disparity was noticed in the mean overall TSD ratio among the different malocclusion categories (P<0.04). Conclusion: Statistically significant TSD between the examined malocclusion groups were observed only in the mean overall TSD ratio

Stem Cell Therapy in Dentistry: An Overview.

Cells with a unique capacity for self-renewal and potency are called stem cells. With appropriate biochemical signals stem, cells can be transformed into desirable cells. Regeneration of oral and maxillofacial structures is earned out by using stem cell therapy, and this has gained momentum in recent days. Future tissues like tissue engineered bone grafts, engineered joints and cranial sutures can be developed with stem cell therapy. We have described the properties, types and advantages of dental stem cells. Emphasis is been given to the possibilities of stem cell therapy in the oral and maxillofacial region including regeneration of tooth and craniofacial defects.

The application of finite element analysis in the skull biomechanics and dentistry.

Empirical concepts describe the direction of the masticatory stress dissipation in the skull. The scientific evidence of the trajectories and the magnitude of stress dissipation can help in the diagnosis of the masticatory alterations and the planning of oral rehabilitation in the different areas of Dentistry. The Finite Element Analysis (FEA) is a tool that may reproduce complex structures with irregular geometries of natural and artificial tissues of the human body because it uses mathematical functions that enable the understanding of the craniofacial biomechanics. The aim of this study was to review the literature on the advantages and limitations of FEA in the skull biomechanics and Dentistry study. The keywords of the selected original research articles were: Finite element analysis, biomechanics, skull, Dentistry, teeth, and implant. The literature review was performed in the databases, PUBMED, MEDLINE and SCOPUS. The selected books and articles were between the years 1928 and 2010. The FEA is an assessment tool whose application in different areas of the Dentistry has gradually increased over the past 10 years, but its application in the analysis of the skull biomechanics is scarce. The main advantages of the FEA are the realistic mode of approach and the possibility of results being based on analysis of only one model. On the other hand, the main limitation of the FEA studies is the lack of anatomical details in the modeling phase of the craniofacial structures and the lack of information about the material properties.

Bioengineering of dental tissues: bibliometric analysis 2000-2011 / Bioingeniería de tejidos dentales: análisis bibliométrico 2000-2011

Introduction: There has been a noticeable increase in experimental use and therapies based on stem cells over recent years. Nevertheless, there is a lack of information about this progress in the dental field, which makes it difficult to trace development and design policies. The purpose of this study, as a first approach to the subject, is to determine a bibliometric profile for the investigation related to bioengineering of dental tissue at a worldwide scale, based on the MEDLINE database, for the period 2000-2011.Methodology: A bibliometric study was carried out. Every article indexed in the MEDLINE database and associated with the terms “stem cells” and “tooth regeneration” for the period 2000-2011 was included. The analyzed variables were publishing date, country of origin, language and publication type (original or review), journal, author, associated university and tissue source (human or animal). Results: For the entire period included in the study, 257 articles were found. Of these, 149 corresponded to original works published in English; 5 in other languages; 92 comprised literature reviews in English, 9 in other languages and 2 publications were included in the “others” category. The countries with the highest research productivity were the United States (24.51 percent, Japan (20.62 percent) and China (17.90 percent), while Brazil (3.9 percent) was the only Latin-American country found in the list. Animal tissues were used in 59.09 percent of them. The most productive authors were Ueda M (17) and Jin Y (11), whereas Fourth Military University (13), University of Tokyo (12) and Capital Medical University (10) had the largest number of publications. Conclusion: The United States, Japan and China concentrate about two thirds of the production. Latin-America was represented only by Brazil.

Introducción: El creciente uso experimental de células madres y el perfeccionamiento de las terapias con estas es un hecho notorio en los últimos años. Sin embargo, en odontología no existen datos del desarrollo de esta área, lo que hace difícil un seguimiento o diseño de políticas. El objetivo de este estudio, siendo una primera aproximación a la temática, es definir el perfil bibliométrico de la investigación asociada a la bioingeniería de tejidos dentales a nivel mundial en la base de datos MEDLINE para el periodo 2000-2011. Metodología: Estudio bibliométrico. Se incluyeron todos los artículos asociados a los términos “stem cells” y “tooth regeneration” para el periodo 2000-2011, indexadas en MEDLINE. Se analizaron las variables: año de publicación, país de origen, idioma y tipo de publicación (original o revisión), revista, autor, universidad de afiliación y origen del tejido utilizado (humano o animal). Resultados: Para todo el período en estudio se hallaron 257 artículos: 149 trabajos de originales publicados en inglés, 5 en otros idiomas; 92 revisiones de literatura en inglés y 9 en otros idiomas; y 2 publicaciones en categoría otros. Los países más productivos fueron Estados Unidos (24,51 por ciento), Japón (20,62 por ciento), China (17,90 por ciento), el único latinoamericano es Brasil (3,9 por ciento). El 59,09 por ciento utilizó tejidos de origen animal. Los autores más productivos fueron Ueda M (17) y Jin Y (11), en universidades fueron Fourth Military University (13), University of Tokyo (12) y Capital Medical University (10). Conclusión: Estados Unidos, Japón y China concentran dos tercios de la producción, Brasil es el único representante latinoamericano.

Eficácia do método de estimativa de idade de Lamendin / Efficacy of Lamendins dental age estimation method

Diante das dificuldades em estimar a idade de adultos e procurando se basear em pesquisas com evidência de qualidade, o presente trabalho objetivou verificar a eficácia do método de estimativa de idade de Lamendin por meio de uma revisão sistemática com metanálise e também aplicando a técnica a uma amostra brasileira. Para a metanálise, foram pesquisados estudos que tinham como objetivo mostrar a eficácia do método, comparando as idades cronológica e estimada da amostra. Foram excluídos os artigos com amostra histórica, os que modificaram a técnica, os que analisaram outros aspectos do método sem retratar sua eficácia e os que apresentaram a amostra em grupo único com indivíduos de menos de 25 anos de idade. Em seguida, a escala de qualidade de evidência QUADAS foi utilizada com modificações. A amostra final foi constituída de oito estudos. O trabalho de campo foi realizado numa amostra composta de 49 dentes provenientes de 26 crânios da coleção do Centro de Estudo e Pesquisa em Ciências Forenses do IML de Guarulhos-SP.

Os resultados mostraram que os estudos identificados descuidam de alguns aspectos metodológicos e que o método é ineficaz em idosos, mas que produz boas estimativas nos outros adultos. Nos brasileiros, adultos jovens mostraram as menores médias das diferenças Entretanto, existem discordâncias na literatura quanto à faixa etária em que o método funciona melhor. Diante do exposto, sugerimos que os estudos tenham mais rigor metodológico e que a técnica seja testada antes de ser usada numa determinada população, para que se possa constatar em qual faixa etária os resultados são mais precisos. Uma pesquisa com uma amostra brasileira maior também deve ser realizada, para que se possa verificar se sexo e tipo de dente influenciam os resultados.

Given the difficulties in estimating the age of adults and trying to rely on surveys of quality evidence, this study aimed to determine the effectiveness of Lamendins method of age estimation through a systematic review and meta-analysis and also by applying the technique to a Brazilian sample. For the meta-analysis, we researched studies that aimed to show the effectiveness of the method by comparing the chronological and estimated ages of the sample. We excluded studies with historical samples, those that changed the technique, the ones that analyzed other aspects of the method without presenting results on effectiveness and the ones that presented the sample in a single group with individuals less than 25years of age. Then, the quality evidence scale QUADAS was used with some modifications. The final sample consisted of eight studies. Fieldwork was conducted in a sample of 49 teeth from 26 skulls from the collection of the Center for Study and Research in Forensic Sciences from the IML Guarulhos-SP. The results showed that the studies identified could be methodologically careless and that the method is ineffective in the elderly, but produces good estimates for other adults. In Brazil, young adults showed the smallest mean errors.

However, there are discrepancies in the literature as to the age at which the method works best. We suggest that the studies have more methodological rigor and that the technique be tested before used in a given population, so it can be verified at what age the results are more accurate. A research with a larger Brazilian sample should be made, so it can be confirmed if sex and type of tooth influence the results.

Odontogenic cell culture in PEGDA hydrogel scaffolds for use in tooth regeneration protocols

In order to obtain a tooth-like structure, embryonic oral ectoderm cells (EOE) and bone marrow-derived stem cells (BMSC) were stratified within a synthetic hydrogel matrix (PEGDA) and implanted in the ileal mesentery of adult male Lewis rats. Wholemount in situ hybridization was used to evaluate the expression of Pitx2, Shh and Wnt10a signals indicative of tooth initiation. In rats, expression of the three markers was present in the oral ectoderm starting at embryonic stage E12.5, which was therefore selected for cell harvesting. Embryos were obtained by controlled service of young female Lewis rats in which estrus was detected by impedance reading. At E12.5, pregnant rats were humanely euthanized and embryos were collected. The mandibular segment of the first branchial arch was dissected and the mesenchyme separated from the ectoderm by enzymatic digestion with pancreatin trypsin solution. BMSCs were collected by flushing the marrow of tibiae and femurs of adult Lewis rats with a-MEM and cultured in a-MEM in 25 cm2 flasks. Second passage BMSC's were recombined with competent oral ectoderm (E12.5-E13) stratifying them within a 3D PEGDA scaffold polymerized by exposure to UV (365nm) inside a pyramidal polypropylene mold. Constructs were incubated from 24 to 48 hrs in a-MEM and then implanted for four to six weeks in the mesentery of adult male (3- 6 month old) Lewis rats. 76 constructs were implanted (37 experimental, 27 negative controls and 12 positive controls). Upon maturation, constructs were harvested, fixed in buffered formalin, processed and stained with hematoxylin eosin (HE). Histological evaluation of the experimental and negative constructs showed that BMSCs underwent an apoptotic process due to lack of matrix interactions, known as anoikis, and were thus incapable of interacting with the competent ectoderm. In contrast, embryonic oral ectoderm was able to proliferate during the mesenteric implantation. In conclusion, PEGDA scaffolds are incompatible with BMSCs, therefore it is essential to continue the search for an ideal scaffold that allows proper tissue interactions.

Para lograr la formacion de una estructura similar a un diente se estratificaron celulas de ectodermo oral embrionario (EOE) con celulas troncales de medula osea (BMSC) dentro de una matriz de diacrilato de polietilenglicol (PEGDA) que se implanto en el mesenterio ileal de machos adultos de ratas Lewis. Mediante hibridizacion in situ de bloque completo se evaluo la expresion de tres genes iniciadores putativos de la formacion dental (Pitx2, Shh y Wnt10a), estableciendo que en ratas las senales iniciadoras de dentogenesis aparecen entre E12.5 y E13. El tejido ectodermico embrionario se obtuvo haciendo cruces controlados de hembras a las que se les detecto el estro mediante impedanciometria. En E12.5 las hembras se sacrificaron y se extrajeron los embriones. Se diseco la porcion mandibular del primer arco branquial y el ectodermo se separo del mesenquima mediante disociacion enzimatica con una solucion de pancreatina tripsina. Las BMSC se extrajeron de los huesos largos de las extremidades inferiores de ratas mediante lavado con a-MEM y se cultivaron en cajas de 25cm2 hasta un segundo pasaje. Las BMSC fueron recombinadas con ectodermo embrionario competente (E12.5 - E13) estratificandolas en un soporte tridimensional de PEGDA, polimerizado con luz ultravioleta (365nm) dentro de un molde piramidal de polipropileno (PP). Los constructos se cultivaron entre 48 y 72 horas en a-MEM y posteriormente fueron implantados en el mesenterio ileal de machos adultos (3 a 6 meses de edad) por un periodo de cuatro a seis semanas. Se implantaron 76 constructos (37 experimentales, 27 controles negativos y 12 controles positivos). En la fecha determinada los animales se sacrificaron mediante asfixia con una mezcla de CO2 y aire recuperando los constructos que se fijaron en formalina tamponada para luego procesarlos y tenirlos con hematoxilina eosina (HE). La evaluacion histologica de los constructos experimentales, positivos y negativos mostro que las BMSC incluidas en el hidrogel sufrieron un proceso de apoptosis conocido como anoikis que impidio su interaccion con las celulas ectodermicas. En contraste el EOE prolifero durante el periodo de implantacion. A futuro se debe buscar la matriz portadora ideal que permita el confinamiento de los dos grupos celulares y que brinde el soporte estructural necesario para la proliferacion de las BMSC facilitando su interaccion con las celulas inductoras de origen ectodermico.

Comparison of fracture resistance of teeth restored with ceramic inlay and resin composite: An in vitro study.

Aim: The aim of this study was to evaluate the in vitro fracture resistance of teeth restored with bonded ceramic inlay and direct composite resin restoration in comparison to the normal tooth. Materials and Methods: This study evaluated the fracture strength of the teeth restored with bonded ceramic inlay and direct composite resin restoration in comparison to the normal teeth. Thirty intact human maxillary first premolars were assigned to three groups: Group 1 - comprising sound/unprepared teeth (control). Group 2 - comprising of Class-II direct composite resin restored teeth and Group 3 - comprising Class-II ceramic inlay restored teeth. Cavities were prepared with occlusal width of 1/3 intercuspal distance and 2 mm deep pulpally. Group 2 teeth were restored with hybrid composite resin (Z350 3M ESPE, USA) and group 3 teeth were restored with Vitadur Alpha alumina (Ivoclare Vivadent, Liechtenstein, Europe). Ceramic inlay was bonded with adhesive cement (rely X resin cement of 3MESPE, USA). The specimens were subjected to a compressive load until they fractured. Data were analyzed statistically by unpaired Student's t test. Results: The fracture resistant strength, expressed as kilonewton (KN), was group 1 - 1.51 KN, group 2 - 1.25 KN, and group 3 - 1.58 KN. Statistically, group III had highest fracture resistance followed by group I, while group II had the lowest average fracture resistance. Conclusion: The fracture resistant strength of teeth restored with ceramic inlay was comparable to that of the normal intact teeth or slightly higher, while teeth restored with direct composite resin restoration showed less fracture resistant strength than that of the normal teeth.

Sex determination by observation of barr body in teeth subjected to high temperatures / Determinación del sexo mediante la observación de la cromatina de barr en piezas sometidas a altas temperaturas

Sex determination is one of the keys in the identification process. A useful histological method for sex determination is the observation of Barr chromatin or Barr body. This study determines the effect of high temperatures on the diagnostic performance of the Barr chromatin observation on teeth. Were used 50 healthy teeth from 25 male and 25 female individuals aged between 14 and 44 years. The teeth were divided into 5 groups (each group with 5 female and 5 male teeth) and were exposed to controlled temperatures of 200, 400, 600, 800, and 1000 degrees C for 5 minutes. The coronal pulp was obtained and the tissue was processed and stained with hematoxylin-eosin. Four histological slides of male and 4 of female individuals were randomly selected, for each temperature level, which were observed by conventional microscopy at 100X magnification, each showing 50 cells per plate. The presence of 1 cell with visible sex chromatin was considered positive for females. It was only possible to evaluate the samples from groups subjected to 200 and 400 degrees C. In the groups analyzed, the test showed 100 percent accuracy. The average number of cells found to be positive Barr chromatin was 15 (SD 3.9) at 200 degrees C and 11 (SD 2.8) at 400 degrees C. Hence, it was possible to detect the sex at these temperatures by observing chromatin of the Barr body in dental pulp.

La determinación del sexo es uno de los pilares del proceso de identificación, Un método histológico útil para la determinación del sexo es la observación de cromatina de Barr. El objetivo de este estudio fue determinar el efecto de altas temperaturas sobre el rendimiento diagnóstico de observación de cromatina de Barr en piezas dentarias. Se utilizaron 50 piezas dentarias sanas, 25 de individuos de sexo masculino y 25 de sexo femenino con edades comprendidas entre los 14 y 44 años. Las piezas dentarias fueron divididas en 5 grupos, (cada grupo con 5 piezas de sexo femenino y 5 de sexo masculino) y fueron expuestas a temperaturas controladas de 200°C, 400°C, 600°C, 800°C y 1000°C por 5 minutos. La pulpa coronaria fue obtenida y el tejido fue procesado para H-E. Se seleccionaron aleatoriamente 4 placas histológicas de individuos de sexo masculino y 4 de sexo femenino, por cada nivel de temperatura, las cuales fueron observadas por microscopía convencional a un aumento de 100X, observándose 50 células por placa. La presencia de 1 célula con cromatina sexual visible se consideró positiva para el sexo femenino. Sólo fue posible evaluar las muestras provenientes de los grupos sometidos a 200°C y 400°C. En los grupos analizados la prueba presentó un 100 por ciento de exactitud. El número medio de células Barr positivas encontradas fue de 15 (DS 3,9) a 200°C y 11 (DS 2,8) a 400°C, por lo que a estas temperaturas fue posible el diagnóstico del sexo mediante la observación de la cromatina sexual en pulpa dental.

Fisiología periodontal del movimiento dentario durante el tratamiento ortodóntico / Periodontal Physiology of tooth movement during orthodontic treatment

La movilización de los dientes durante el tratamiento ortodóncico involucra procesos químicos, físicos y mecánicos. A partir de la aplicación de una fuerza, se da inicio a una serie de acontecimientos que dan como resultado el traslado del órgano dental desde su posición original. Existen diversas teorías o hipótesis que intentan describir el proceso de activación del sistema de remodelado óseo, sin embargo, todavía se siguen realizando investigaciones a fin de comprenderlo más detalladamente. El movimiento dentario en sí, requiere del remodelado del hueso alveolar, el cual involucra fases de resorción y aposición ósea. En la siguiente revisión bibliográfica se exponen secuencial y resumidamente los procesos mencionados

The teeth mobilization during orthodontic treatment involves chemical, physical and mechanical processes. Since the force application, initiates a series of events that result in the removal of the dental organ from its original position. There are various theories or hypotheses that attempt to describe the activation process of bone remodeling, however, research is still being conducted to understand it in more detail. Tooth movement itself, requires the remodeling of alveolar bone, which involves resorption phases and bone apposition. In the following literature review outlines the summary and sequential processes

Tooth regeneration: Current status.

Regeneration of a functional tooth has the potential to be a promising therapeutic strategy. Experiments have shown that with the use of principles of bioengineering along with adult stem cells, scaffold material, and signaling molecules, tooth regeneration is possible. Research work is in progress on creating a viable bioroot with all its support. A new culture needs to be created that can possibly provide all the nutrients to the stem cells. With the ongoing research, tissue engineering is likely to revolutionize dental health and well-being of people by regenerating teeth over the next decade.

Importancia clínica de la antropología dental / Dental anthropology: clinical importance

El propósito de este artículo es hacer una revisión de la literatura que evidencie la aplicación clínica de la antropología dental dentro del contexto odontológico, de tal manera que los estudiantes, profesionales y especialistas de la salud oral comprendan la importancia del trabajo interdisciplinario de la odontología y la antropología, cuyo puente técnico y científico se centra en los dientes, y todo aquello que del estudio de estos se desprende, como es el caso de la morfología, la odontometría, la patología y las modificaciones intencionales y culturales. Por tanto, la interacción de estas dos disciplinas fortalecerá la perspectiva investigativa, con lo que la generación de nuevo conocimiento podrá permear tanto el trabajo clínico-científico del odontólogo como la labor técnico-científica del antropólogo.

This article reviewed the literature about dental anthropology in souch manner that dental studets, dentistry and Specialist would understand the importance of multidisciplinary work between dental anthropology and dentistry. Both proffesions are linned by teeth in wich dental morphology, odontometrics, dental pathology and even culture interacts. These interactions between dental anthropology and detistry might improve research and knowledge.

El aparato dentario, su forma y función con dientes naturales, artificiales y mixtos / The dental apparatus, its form and function with natural artificial and mixed teeth

En el siglo XX, diversos autores acordaron denominar la forma de la cavidad bucal en seres humanos como una figura ovalada, terminología que no concuerda, por referirse este fonema a un gráfico plano. Entonces, se decidió buscar nuevos vocablos para la forma de la misma; conjuntamente, se estudió y se determinó el volumen que aún no estaba establecido. Finalmente, se acordó que la cavidad bucal es un cuerpo cuadridimensional cambiante, con superficie, volumen, espesor, límites, anexos y un tiempo individual de concavidad interna, comprobándose que la forma es esferoidal y de un volumen apropiado para establecer el tamaño del bolo alimenticio.

Alternative methodology for flexural strength testing in natural teeth

Tem-se observado na área odontológica a utilização de dentes naturais para a realização de pesquisas diversas (in vivo, in situ e/ou in vitro ). O comportamento mecânico de dentes, sujeitos aos esforços mastigatórios, geralmente é utilizado como variável de resposta. Durante uma condição de maloclusão, a componente mais relevante para a integridade da estrutura dental é a não-axial (de flexão). Esta, quando atua em um dente em função na cavidade bucal, gera uma situação semelhante à de uma viga em equilíbrio suportando uma carga concentrada na extremidade livre. Com base nessa configuração, foi desenvolvida uma metodologia para o estudo do comportamento de dentes sujeitos a esforços dessa natureza. A metodologia leva em consideração aspectos particulares do dente analisado, tais como área de secção transversal, momento de inércia, etc. Na determinação da área da secção transversal, descreveu-se a utilização de um analisador de imagens. Para a determinação das demais variáveis, implementou-se um programa em linguagem de programação C++ utilizando o compilador Borland C++ Builder, versão 1.0, para ambiente Windows (Borland International, EUA). Os resultados mostraram que, com o emprego da metodologia desenvolvida, alcançam-se resultados mais precisos, sendo sua utilização adequada a pesquisas que utilizam o comportamento à flexão de dentes extraídos como variável de resposta.

Periodontal regeneration--fantasizing the future.

Periodontal Regenerative Surgical Procedures are, by definition, supposed to restore all three tooth-supporting tissues i.e. periodontal ligament fibres, alveolar bone and the cementum. In humans, we can now regenerate considerable amounts of alveolar bone, and periodontal ligament with the use of bone graft material and barrier membranes. The purpose of this article is to acquaint the reader with the current trends as well as some new areas along which periodontal regenerative therapy might shape up in the future. Since, some fields are still in their infancy, it can be only envisioned as to how these new fields of science might constantly evolve to redefine periodontal therapy in due time.

Postes de base orgánica y resistencia del remanente dentario: modelo experimental / Organic-based posts and resistance of the tooth remainder: an experimental model

Se han desarrollado postes de base orgánica para ser utlilizados en piezas dentarias con tratamiento endodóntico. El objetivo de este trabajo fue evaluar, mediante un modelo experimental, la resistencia a la fractura del remanente dentario cuando se utiliza este tipo de postes, en comparación con la obtenida mediante otros de base metálica. Se confeccionaron varillas cilíndricas de 20mm. de largo y 3mm. de diámetro con aleaciones metálicas (Ni-Cr Y Cu-Al) y con materiales de base orgánica (resina acrílica y resina reforzada). Se incluyeron las varillas en cilindros de yeso piedra mejorado dejando expuestos 5mm. Después de fraguado, sobre el extremo expuesto de las varillas se aplicaron cargas compresivas crecientes y se registró la fuerza en Newton necesaria para producir la fractura del yeso. Los valores medios de fuerza requerida para producir este efecto fueron significativamente mayores en el caso de ls varillas metálicas. Se considera que estas diferencias podrían deberse a que la mayor deformación que se produce en el material orgánico generó tensiones traccionales y flexurales que no pudieron ser absorbidas por el yeso. Los postes de base orgánica no estarían indicados en situaciones clínicas en las que el esfuerzo oclusal se concentre directamente sobre ellos

Nutrição e fisiologia dos dentes / Teeth nutrition and physiology

The teeth, organ present in the oral cavity, perform important functions such as esthetic, phonetic, preventive and masticatory. In its masticatory function, it is strictly related to salivation, both becoming of great importance in the food digestion. Nutrition is related systemically and topically to the teeth. When this relation is adequate, it allows the teeth to perform all its functions and contribute for the good functioning of the organism.

Los dientes, órganos presentes en lacavidad bucal desempeñan funciones estética, fonética y masticatoria. La función masticatoria esta estrechamente relacionada con la salivación y ambas son importantes para la digestión de los alimentos. El cuidado con los dientes debe estar siempre presente, desde su erupción en la primera infancia, hasta la vejez, para que desempeñen su función en forma adecuada y contribuyan al buen funcionamiento del organismo

Os dentes, órgão presente na cavidade oral, desempenham funções importantes tais como estética, fonética, preventiva e mastigatória. Na sua função mastigatória, relaciona-se estreitamente com a salivação, tornando-se ambas de grande importância na digestão dos alimentos. A nutrição relaciona-se com os dentes sistêmica e topicamente. Quando esta relação se faz adequadamente, permite aos dentes exercer todas as suas funções e contribuir para o bom funcionamento do organismo