Dental Loss in the Lower Socioeconomic Stratum of a Sample of the Chilean Population Born in the 19TH and 20TH Centuries

SUMMARY: Partial or total dental loss (edentulism) is associated with decreased quality of life. Chile has large socioeconomic gaps, which are also recognized in oral health, but it is not known how Edentulism has evolved throughout the country. The aim of this study was to determine the edentulism in people born during the 19th and 20th centuries in Chile, who died in the 20th century, and to compare it with current data from the Chilean Ministry of Health (MINSAL) to observe its evolution in the country. For this purpose, 60 3D models of skulls from the Subactual Osteological Collection of Santiago were analyzed (30 individuals per sex), in which the presence and absence of teeth in antemortem in the maxilla were analyzed. A high percentage of tooth loss was observed, with 65 % partial edentulism, a 30 % total edentulism, and only 5 % had complete dentition in this osteological collection. In addition, a significant decrease over time was found; in 2017, the percentage of complete dentition at the national level was 32.8 %. A higher frequency of edentulism was also found in females from the osteological collection, with a significant probability of twice as much edentulism as in males. However, this sex difference was smaller than those found in the current study. Our study is the first to compare edentulism in Chile in two different time periods, since, in addition to studying it in the 19th and 20th century, it is carried out with data from the present day and in line with previous research, reveals the importance of socioeconomic and sex variables for dental loss.

La pérdida parcial o total de dientes (edentulismo) se asocia a una disminución de la calidad de vida. Chile tiene grandes brechas socioeconómicas, que también se reconocen en la salud oral, pero se desconoce cómo ha evolucionado el edentulismo en el país. El objetivo de este estudio fue determinar el edentulismo en personas nacidas durante los siglos XIX y XX en Chile y fallecidas en el siglo XX, y compararlo con datos actuales del Ministerio de Salud de Chile (MINSAL) para observar su evolución en el país. Para ello, se analizaron 60 modelos 3D de cráneos de la Colección Osteológica Subactual de Santiago (30 individuos por sexo), en los que se analizó la presencia y ausencia de dientes en dentición antemortem en el maxilar. Se observó un alto porcentaje de pérdida dentaria, con un 65 % de edentulismo parcial y un 30 % de edentulismo total, y sólo un 5 % presentaba dentición completa en esta colección osteológica. Además, se encontró una disminución significativa a lo largo del tiempo; en 2017, la dentición completa a nivel país fue del 32,8 %. También se encontró una mayor frecuencia de edentulismo en las mujeres de la colección osteológica, con una probabilidad significativa del doble de edentulismo que en los hombres. Sin embargo, esta diferencia de sexo fue menor que la hallada en datos actuales. Este estudio es el primero que compara el edentulismo en Chile en dos épocas diferentes, ya que además de estudiarlo en los siglos XIX y XX, se realizó con datos de la actualidad y, en línea con investigaciones previas, revela la importancia de las variables socioeconómicas y de sexo en la pérdida dental.

An R Script to Estimate Which and How Many Landmarks Represent the Most Variable Parts of an Object

SUMMARY: The study of the shape variation in geometric morphometrics has an important limitation known as the Pinocchio effect. The Pinocchio effect produces artifactual variances of the landmarks and implies that it is not possible to know the morphological change structure of an object, other than by dividing the landmark sets and then comparing them. This, however, involves making prior assumptions about the pattern of variation of an object. In this study, we provide a code in R to iterate over a complete set of landmarks and test all possible combinations of landmarks until deliver those landmarks associated with the largest to the smallest morphological changes. We tested this on a sample of 28 landmarks in 143 3D models of human skulls. The results indicated that this process can result in a pooled variance of a subset of landmarks that is an order of magnitude larger than that of several other regions of the skull. This method makes it possible to describe the pattern of variation of any 2D or 3D object represented by fixed landmarks, to distinguish the shape features that have more morphological dispersion, and to avoid any aprioristic assumptions about how the morphological changes of an object behave.

El estudio de la variación de la forma en morfometría geométrica tiene una limitación importante conocida como efecto Pinocho. El efecto Pinocho produce variaciones artefactos de los puntos de referencia e implica que no es posible conocer la estructura del cambio morfológico de un objeto, salvo dividiendo los conjuntos de puntos de referencia y luego comparándolos. Sin embargo, esto implica hacer suposiciones previas sobre el patrón de variación de un objeto. En este estudio, proporcionamos un código en R para iterar sobre un conjunto completo de puntos de referencia y probar todas las combinaciones posibles de puntos de referencia hasta entregar aquellos puntos de referencia asociados con los cambios morfológicos más grandes a los más pequeños. Probamos esto en una muestra de 28 puntos de referencia en 143 modelos 3D de cráneos humanos. Los resultados indicaron que este proceso puede dar como resultado una variación combinada de un subconjunto de puntos de referencia que es un orden de magnitud mayor que el de varias otras regiones del cráneo. Este método permite describir el patrón de variación de cualquier objeto 2D o 3D representado por puntos de referencia fijos, distinguir las características de forma que tienen más dispersión morfológica y evitar suposiciones apriorísticas sobre cómo se comportan los cambios morfológicos de un objeto.

Biological properties of stem cells from the apical papilla exposed to lipopolysaccharides: An in vitro study.

OBJECTIVE: The aim of this study was to analyze the effect of lipopolysaccharides (LPS) on the biological properties of stem cells from the apical papilla (SCAPs), such as viability, adhesion to dentin, odontoblast-like differentiation, mineralization, and release of immunomodulatory cytokines. DESIGN: SCAPs were isolated from immature teeth of three donors (10 to 15 years old) and cultured in mineralizing media with or without 1 µg/mL lipopolysaccharide (LPS). Cells were seeded and cultured under standardized conditions; viability was assessed by MTT assay on days 1, 3, 5, and 7; adhesion to dentin was analyzed using an environmental scanning electron microscope after 2 days; the expression of odontogenic and mineralization genes (DSPP, DMP-1, OCN, Col1A1) was evaluated through qPCR after 14 days, mineralization was evaluated with alizarin red staining after 21 days; and the release of immunomodulatory cytokines (IL-6 and IL-10) was measured by ELISA after 1 and 7 days. The Kruskal-Wallis test was performed to detect the effect of LPS on SCAPs, followed by the Dunn-Sidak test. RESULTS: LPS presence in the culture media affected SCAPs viability on day 5 and increased IL-6 secretion by day 7, however, SCAPs retained the adhesion to dentin and mineralization capacities, as well as the differentiation capacity into a mineralizing phenotype. CONCLUSION: In conclusion, within the limitations of this in vitro study, and under the inflammatory microenvironment simulated in this study, stem cells from the apical papilla were found with retained adhesion capacity to dentin, differentiation into a mineralizing phenotype, mineralization, and release of IL-10.

Biological Properties of Dental Pulp Stem Cells Isolated from Inflamed and Healthy Pulp and Cultured in an Inflammatory Microenvironment.

INTRODUCTION: The aim of this study was to assess whether the biological characteristics of dental pulp stem cells (DPSCs), such as viability, adhesion to dentin, mineralization, and release of immunomodulatory cytokines, are affected by the inflammatory status of the donor tissue and/or the sustained inflammatory environment. METHODS: DPSCs were isolated from pulps from 3 caries-free teeth (healthy or hDPSCs), and from 3 teeth with irreversible pulpitis or deep caries (unhealthy DPSCs or uDPSCs). The cells were cultured in odontogenic and osteogenic media with or without lipopolysaccharides. Viability was analyzed by MTT assay at days 1, 3, 5, and 7; adhesion to dentin was evaluated through an environmental scanning electron microscope after 48 hours and through MTT assay; mineralization was analyzed with alizarin red staining after 21 days; and the release of proinflammatory (interleukin 6) and immunosuppressive cytokines (interleukin 10) was measured with the enzyme-linked immunosorbent assay after 24 hours and 7 days. RESULTS: The inflammatory status of the pulp significantly reduced the viability and mineralization capacity of the DPSCs, although it did not affect the adhesion capacity to dentin or the secretion of the proinflammatory interleukin. The inflammatory microenvironment (lipopolysaccharide) only had a significant impact on the secretion of interleukin 6, which was augmented after 7 days. CONCLUSIONS: The inflammatory status of the dental pulp should be taken into account when the use of DPSCs is intended either for research and/or for application in reparative or regenerative therapies.

Modularity of the wrist in extant hominines.

Wrist shape varies greatly across primates and previous studies indicate that the numerous morphological differences among them are related to a complex mixture of phylogeny and function. However, little is known about whether the variation in these various anatomical differences is linked and to what extent the wrist bones vary independently. Here, we used 3D geometric morphometrics on a sample of extant hominines (Homo sapiens, Pan troglodytes, Gorilla gorilla, and Gorilla beringei), to find the model that best describes the covariation patterns among four of the eight carpals (i.e., capitate, lunate, scaphoid, and trapezium). For this purpose, 15 modular hypotheses were tested using the Covariance Ratio. Results indicate that there is a covariation structure common to all hominines, which corresponds to stronger covariation within each carpal as compared to the covariation between carpals. However, the results also indicate that that there is a degree of codependence in the variation of some carpals, which is unique in humans, chimpanzees, and gorillas, respectively. In humans there is evidence of associated shape changes between the lunate and capitate, and between the scaphoid and trapezium. This covariation between lunate and capitate is also apparent in gorillas, while chimpanzees display the greatest disassociation among carpals, showing low covariation values in all pairwise comparisons. Our analyses indicate that carpals have an important level of variational independence which might suggest a high degree of independent evolvability in the wrists of hominines, and that although weak, the structure of associated changes of these four carpals varies across genera. To our knowledge this is the first report on the patterns of modularity between these four wrist bones in the Homininae and future studies might attempt to investigate whether the anatomical shape associations among carpals are functionally related to locomotion and manipulation.

Digital Reconstructions Using Linear Regression: How Well Can It Estimate Missing Shape Data from Small Damaged Areas?

Skeletal remains analyzed by anthropologists, paleontologists and forensic scientists are usually found fragmented or incomplete. Accurate estimations of the original morphologies are a challenge for which several digital reconstruction methods have been proposed. In this study, the accuracy of reconstructing bones based on multiple linear regression (RM) was tested. A total of 150 digital models from complete zygomatics from recent past populations (European and African American) were studied using high-density geometric morphometrics. Some landmarks (i.e., 2, 3 and 6) were coded as missing to simulate incomplete zygomatics and the missing landmarks were estimated with RM. In the zygomatics, this simulated damage affects a few square centimeters or less. Finally, the predicted and original shape data were compared. The results indicate that the predicted landmark coordinates were significantly different from the original ones, although this difference was less than the difference between the original zygomatic and the mean zygomatic in the sample. The performance of the method was affected by the location and the number of missing landmarks, with decreasing accuracy with increasing damaged area. We conclude that RM can accurately estimate the original appearance of the zygomatics when the damage is small.

A geometric morphometric approach to the study of sexual dimorphism in the modern human frontal bone.

OBJECTIVES: We analyzed the main anatomical traits found in the human frontal bone by using a geometric morphometric approach. The objectives of this study are to explore how the frontal bone morphology varies between the sexes and to detect which part of the frontal bone are sexually dimorphic. MATERIALS AND METHODS: The sample is composed of 161 skulls of European and North American individuals of known sex. For each cranium, we collected 3D landmarks and semilandmarks on the frontal bone, to examine the entire morphology and separate modules (frontal squama, supraorbital ridges, glabellar region, temporal lines, and mid-sagittal profile). We used Procrustes ANOVAs and LDAs (linear discriminant analyses) to evaluate the relation between frontal bone morphology and sexual dimorphism and to calculate precision and accuracy in the classification of sex. RESULTS: All the frontal bone traits are influenced by sexual dimorphism, though each in a different manner. Variation in shape and size differs between the sexes, and this study confirmed that the supraorbital ridges and glabella are the most important regions for sex determination, although there is no covariation between them. The variable size does not contribute significantly to the discrimination between sexes. Thanks to a geometric morphometric analysis, it was found that the size variable is not an important element for the determination of sex in the frontal bone. CONCLUSION: The usage of geometric morphometrics in analyzing the frontal bone has led to new knowledge on the morphological variations due to sexual dimorphism. The proposed protocol permits to quantify morphological covariation between modules, to calculate the shape variations related to sexual dimorphism including or omitting the variable size.

Recommendations for improving photo quality in close range photogrammetry, exemplified in hand bones of chimpanzees and gorillas / Recomendaciones para mejorar la calidad de las fotos en fotogrametría de corto alcance, ejemplificado en huesos de las manos de chimpancés y gorillas

SUMMARY: Photogrammetry is becoming increasingly popular in morphological research and teaching due to its portability, ability to reliably render 3D models, and quality-to-price relationship relative to some popular surface scanners. Compared to surface scanners, however, the learning process in photogrammetry can be very time consuming. Here we describe common mistakes of photo capture in close-range photogrammetry that greatly affect 3D output and tips to improve them. Problems were identified after the 3D model construction of 780 hand bones of chimpanzees and gorillas from museum collections. Their hands are composed of 27 bones which vary in length and complexity. We show how lighting, object position and orientation, camera angle, and background affect the 3D output. By taking these factors into account, time and error rates for beginners can be greatly reduced and 3D model quality can be considerably improved.

RESUMEN: La fotogrametría está siendo cada vez más popular en la investigación y enseñanza morfológica. Esto debido a su portabilidad, confiabilidad de los modelos 3D y buena relación calidadprecio. Comparada con los escáneres de superficie, sin embargo, el proceso de aprendizaje de la fotogrametría puede llevar mucho tiempo. Aquí se describen errores comunes en la toma de fotos para fotogrametería que afectan de manera importante la creación de los modelos 3D, así como consejos para superarlos. Los problemas descritos fueron identificados luego de la construcción de 780 modelos 3D de huesos de la mano de chimpancés y gorillas depositados en distintas colecciones de museos. Las manos de estas especies están compuestas por 27 huesos que varían en tamaño y complejidad. En este artículo mostramos como la luz, la posición y orientación del objeto, el ángulo de la cámara y el fondo de la imagen afectan el resultado en 3D. Considerando estos factores, personas que están aprendiendo esta técnica pueden reducir de manera importante el tiempo y la probabilidad de error, y mejorar considerablemente la calidad de los modelos 3D.

Relation between muscle architecture and first metacarpal morphology, and its implications for human hand evolution.

Previous studies have proposed that our ability to produce and use stone tools was the primary selective pressure explaining the evolution of the human hand. Derived traits in humans include a robust first metacarpal and longer thumbs relative to the other fingers. Along with other anatomical peculiarities, humans can exert forceful precision and have powerful grips, and can resist loads during tool production and use. Despite this biomechanical explanation for the morphology of the human hand, limited work has been done on the soft tissue and, therefore, the relationship between the hand bones and the muscles most heavily relied upon during tool-related behaviours still requires thorough investigation. For this purpose, we have dissected 23 forearms and hands of fresh human cadavers of known sex and age at death, and dissected all the muscles attached at the first metacarpal (the first dorsal interosseous, opponens pollicis, and abductor pollicis longus muscles). Variations in physiological cross-sectional area, muscle mass, and fibre length were compared with metacarpal anatomy. In no case bone traits were a significant predictor of muscle features. In contrast, sex and age predicted muscle architecture in several cases, thus substantially affecting the functional analysis based on linear measurements of this bone. The data, therefore, failed to provide a deductive framework for predicting muscle recruitment based on measurements of bone from the fossil record.

Insertion sites in manual proximal phalanges of African apes and modern humans.

OBJECTIVES: The primary aim of this study was to describe the insertion sites of the ligaments holding the flexor digitorum profundus and superficialis muscles (flexor ridges) in proximal phalanges 2-5 of African apes and modern humans. To interpret differences in flexor ridge size based on general behavioral differences among taxa. MATERIALS AND METHODS: We analyzed 3D models of manual proximal phalanges 2-5 from 29 gorillas (Gorilla beringei and Gorilla gorilla), 30 chimpanzees (Pan troglodytes) and 36 recent modern humans. Flexor ridges (mm2) were compared within and across genera. RESULTS: Gorillas and chimpanzees had larger flexor ridges for phalanges 2-4 than humans and this difference subsists when controlling for body size. Each genus had a unique insertion size pattern across the digits, with the most heterogeneous pattern found in chimpanzees, followed by humans, and lastly gorillas. These patterns corresponded strongly to the differences in the size of the phalanges within each genus, except for phalanx 5 in humans, which had a larger flexor ridge than expected. DISCUSSION: When comparing these genera, the flexor ridges signal differences between taxa that use their hands for manipulation and locomotion (gorillas and chimpanzees) and taxa that use them exclusively for manipulation (humans). This functional signal was also apparent in the PP5 of humans, whose larger FR may be indicating the high recruitment of this digit during forceful precision grip characteristic of humans.

El dimorfismo sexual en distintas relaciones cráneo-mandibulares / Sexual dimorphism in different craneomandibular relationships

La estimación del sexo en base a restos esqueletales es uno de los principales objetivos de las ciencias forenses. Esta estimación se basa en las diferencias de forma y tamaño que existen entre mujeres y hombres (dimorfismo sexual). En este trabajo se analiza la asociación entre el dimorfismo sexual de la mandíbula y las distintas relaciones cráneo-mandibulares (ortognata, prognata y retrognata). Se analizaron 4 medidas faciales (altura facial, altura de la rama de la mandíbula, ancho mínimo de la rama mandibular, largo del cuerpo de la mandíbula) en tele-radiografías de 114 pacientes chilenos de sexo y relación cráneo-mandibular conocidos para evaluar si, al igual que en poblaciones de otras partes del mundo, estas son sexualmente dimórficas. Los resultados indican que con la excepción del largo del cuerpo de la mandíbula, las demás variables permiten una elevada clasificación correcta del sexo de los individuos (88,6 % de los casos). Se concluye que una relación cráneo-mandibular retrognata o prognata, no afecta la estimación confiable del sexo de los individuos de población chilena.

Sex assessment using bone remains is one of the main goals of forensic sciences. This assessment is possible because of the morphological and size differences between women and men (sexual dimorphism). In this work we study the association between sexual dimorphism and the different positions of the mandible and skull (prognathism, retrognathism and orgotnatism). We analyze 4 facial measurements in 114 teleradiographies of Chilean patients with known sex and positional relationship of the mandible and cranium, to evaluate if, as in populations of other parts of the world, these are sexually dimorphic. The results indicate that, with the exception of mandible width, the rest of the variables allows a high correct classification of individuals by sex (88.6 % of the cases). We conclude that the relation between different positions of the mandible and skull does not affect a reliable sex assessment in Chilean population.