Double-rowed teeth: design specialization of theH. venatorants for enhanced tribological stability.

The antH. venatorcan engage in various labors using a pair of elongated mandibles with the ability to rotate about two orthogonal axes. This biaxial rotation enables the ant to gently handle their small, fragile eggs with enhanced contact area and smaller work space. However, how this biaxial rotation influences the ant's predation ability and how the ant responds to this influence remain elusive. We quantitatively investigate the tribological performance of the ant's mandibles during interactions with prey by taking morphology and kinematics into consideration. We find that each ant mandible features unique, double-rows of dorsal teeth (DT) and ventral teeth (VT), which are employed to firmly clamp prey over a wide range of sizes by biting their different body parts, demonstrating the ant's predation ability. We hypothesize the mechanism underlying such an ability may rely on the two, non-parallel rows of teeth which potentially eliminate effects of biaxial rotation. To test this hypothesis, we systematically change the distribution and orientation of teeth on bio-inspired robotic mandibles and investigate the mandible tribological performance of different teeth configurations. We find that the friction coefficient varies prominently between the DT and VT resulting from biaxial rotation, with the variations showing an inverse pattern. This explains the observed phenomenon that mandibles equipped with DT and VT provide the most stable friction coefficient when clamping objects of different sizes using different mandible regions. The specialized distribution of teeth facilitates enhanced tribological stability in capturing prey, and demonstrates an intrinsic link between the form, motion, and function in the insect appendages. Our research sheds lights on the current understanding of the predation behaviors of ants, and can inspire future design of multifunctional robotic grippers.

Patient Eligibility for Standardized Treatment of the Edentulous Mandible: A Retrospective CBCT-Based Assessment of Mandibular Morphology.

The aim of the study was to evaluate the proportion of patients recommended for full-arch mandibular restoration that would be eligible for treatment with a recently developed premanufactured full-arch prosthesis (Trefoil™, Nobel Biocare) based on the morphology of their lower jaw. Anonymized cone beam computed tomography (CBCT) data from 100 partially and fully edentulous patients referred for full-arch mandibular restoration were retrospectively collected from an imaging center database. Using custom-built software, CBCTs of mandibles were registered to a reference CBCT of a patient treated previously with a premanufactured full-arch prosthesis to determine if patients had adequate horizontal width and vertical height for implant placement. Bone height and thickness around simulated implants and distances to the incisive canal were evaluated. Mandibular arch width and semi-automated volume calculations were also performed. Using the system-specific 5.0 mm diameter implants with lengths of 13 and 11.5 mm, 85% and 86% of patients, respectively, were eligible for treatment with the standardized prosthesis. Eligibility was higher for men than women (odds ratio = 3.9, p = 0.045) due to increased bone volume. Based on mandibular morphology, our results suggest that the standardized treatment concept could serve a large percentage of patients with edentulous mandibles or failing dentition in the mandible.

Hueso cortical en sínfisis mandibular de sujetos de clase I / Cortical bone in mandibular symphysis of class I subjects

El objetivo fue evaluar la relación de tejido óseo cortical presente en el sector anterior y posterior de sínfisis mandibular. Se seleccionaron 18 sujetos clase I dentaria y esqueletal, de ambos sexos, a partir de una tomografía computarizada de haz cónico para analizar morfométricamente en base a la posición de los dientes canino, incisivo lateral e incisivo central de ambos lados; se analizó la distancia vertical desde el ápice dentario hasta el punto más inferior del margen mandibular y la distancia anteroposterior en dos niveles inferiores del ápice (5 mm y 10 mm), donde se identificó el grosor de hueso cortical. El análisis de datos fue realizado con la prueba ANOVA considerando un valor de p<0,05. Se observó que el hueso cortical es de mayor tamaño en la cortical lingual que la cortical bucal con casi 1 mm de diferencia; la cortical inferior fue la de mayor tamaño; no se observaron diferencias en las mediciones realizadas para cada diente. Se concluye que el hueso cortical es de menor tamaño en el sector bucal al compararse con el lingual e inferior; se debe explorar los alcances quirúrgicos de este hallazgo.

The aim of this research was to evaluate the relation between the cortical bone in the anterior and posterior area of the mandible. Were selected 18 subjects, male and female, with dental and skeletal class I; in all of them was realized a cone beam computed tomography to make a morphometric analysis in agreed with de canine, lateral incisor and central incisor in the right and left, side. Was analyzed the distance in cortical area in a line from the dental apex and the horizontal line was obtained 5 mm and 10 mm from the dental apex; statistical significance was obtained by ANOVA considering a p value <0.05. Was observed that the cortical bone is thicker in the lingual side than the buccal side (1 mm diference approximately); the low cortical presented bigger size than anterior or posterior cortical bone; was not observed statistical differences between bone related to teeth. Its concluded that the buccal cortical bone is lower than lingual cortical bone; it is necessary an analysis about the surgical implications.

Morfología ósea de sínfisis mandibular: estudio piloto / Osseous morphology in the mandibular symphysis: a pilot study

El objetivo de este estudio fue evaluar la relación de tejido óseo cortical y esponjoso en el sector anterior de la mandíbula. Se seleccionaron 14 sujetos de ambos sexos para realizar el estudio piloto de este protocolo; en todos los sujetos se realizó un estudio con tomografía computarizada de haz cónico para realizar análisis morfométrico en base a la posición de los dientes canino, incisivo lateral e incisivo central de ambos lados; se analizó la distancia vertical desde el ápice dentario hasta el punto más inferior del margen mandibular y se analizó la distancia anteroposterior en dos niveles inferiores del ápice (5 mm y 10 mm); en estos niveles se identificó el tamaño de hueso cortical y el tamaño de hueso esponjoso. Se observó que el hueso cortical es de mayor tamaño en la cortical lingual que la cortical bucal, con casi 1 mm de diferencia; el hueso esponjoso fue similar a la sumatoria de ambos huesos corticales (5 mm aproximadamente) en las áreas evaluadas. Se concluye que el hueso cortical es menor en el sector bucal al compararse con el lingual; la distancia vertical desde el ápice dentario hasta el margen mandibular fue de 16,5 y 21,05 mm.

The aim of this research was to evaluate the relation between the cortical and cancellous bone in the anterior area of the mandible. Were selected 14 subjects, male and female, to make the pilot study with this protocol; in all of them was realized a cone beam computed tomography to make a morphometric analysis in agreed with de canine, lateral incisor and central incisor of the both, right and left, side. Was analyzed the distance between the apex of the tooth to the inferior point of the cortical bone in the marginal area and in 5 and 10 mm lower of the dental apex. In these levels were identified the cortical bone size and cancellous bone size. Was observed that the cortical bone is thicker in the lingual side than the buccal side (1 mm diference approximately); the cancellous bone size is like the lingual and buccal cortical size (5 mm approximately) in the evaluated areas. Its concluded that the buccal cortical bone is lower than lingual cortical bone; the vertical distance between the apex and the basilar area is close to 16.5 and 21.05 mm.

Relationship between masticatory rhythm, body mass and mandibular morphology in primates.

OBJECTIVE: It has been proposed that rhythmic movements such as locomotion and respiration have a period proportional to body mass(1/4). Mastication basically consists of rhythmic alternation of jaw-closing and jaw-opening movements. We studied the relation between masticatory rhythm and body mass in primates, and masticatory rhythm and mandible morphology. METHODS: We measured the chewing cycle duration (CCD), mandibular length, mandible height, mandible width and distance from the condylar process of mandible to the centre of gravity of the mandible. Body mass was quoted from the literature. RESULTS: The CCD is related to mandible morphology and was found to be proportional to body mass(1/6). CONCLUSION: These findings suggest that masticatory rhythm is correlated with body mass and mandibular morphology, and that scaling rate of masticatory rhythm to body mass is slower than for the other rhythms.