An ossified or 'fused' mandibular symphysis characterizes the origins of the Anthropoidea, a primate suborder that includes humans. Longstanding debate about the adaptive significance of variation in this jaw joint centers on whether a bony symphysis is stronger than an unfused one spanned by cartilage and ligaments. To provide essential information regarding mechanical performance, intact adult symphyses from representative primates and scandentians were loaded ex vivo to simulate stresses during biting and chewing - dorsoventral (DV) shear and lateral transverse bending ('wishboning'). The anthropoid symphysis requires significantly more force to induce structural failure vs. strepsirrhines and scandentians with unfused joints. In wishboning, symphyseal breakage always occurs at the midline in taxa with unfused conditions, further indicating that an ossified symphysis is stronger than an unfused joint. Greater non-midline fractures among anthropoids suggest that fusion imposes unique constraints on masticatory function elsewhere along the mandible, a phenomenon likely to characterize the evolution of fusion and jaw form throughout Mammalia.
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http://dx.doi.org/10.1038/s41598-020-62025-8 | DOI Listing |
J Pers Med
October 2024
Department of Orthodontics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung, University College of Medicine, Kaohsiung 833253, Taiwan.
Objective: Mandibular full-arch distalization (MFD) is a popular approach, particularly in non-extraction cases. However, we still cannot confirm whether facial patterns affect the amount of limits. This study aimed to determine the anatomical MFD limits in patients with different facial patterns.
View Article and Find Full Text PDFJ Clin Exp Dent
October 2024
MD DDS. Division of Maxillofacial Surgery, University Hospital "Maggiore della Carità", University of Eastern Piedmont, Novara, Italy.
Background: The treatment of multiple mandibular fractures may often be challenging. The aim of this study was to evaluate the characteristics and outcomes of multiple mandibular fractures, with a focus on triple mandibular fractures.
Material And Methods: Patients with multiple (triple) mandibular fractures were included.
Contemp Clin Dent
September 2024
Department of Growth and Development, College of Dentistry, University of Nebraska Medical Center, Lincoln, Nebraska.
Background: External apical root resorption (EARR) is an unfavorable side effect of orthodontic treatment. Orthodontic treatment of patients with increased crowding could lead to the proclination of incisors and proximity of roots to the cortical plates.
Aims: The aim of this study was to evaluate the effects of the proximity of the labial and lingual cortical plates and the inclination of incisors on EARR.
J Anat
October 2024
Department of Biosciences, Universidade Federal de São Paulo (UNIFESP), Santos, São Paulo, Brazil.
When developing, the mandible presents great plasticity and contains condensed mesenchymal cells that develops into Meckel's cartilage, of which the anterior part forms the mandibular symphysis. Mandible human development studies focus on investigating whether the beginning of mandibular fusion in fetal period is related to symphysis ossification and the tensions imposed on it, considering that tongue movements, mouth opening, and closing can be seen in fetuses. This research analyses tissue modifications during human mandibular symphysis growth using light and scanning electron microscopy to relate them to its functional structure.
View Article and Find Full Text PDFJ Neurosurg Pediatr
October 2024
1Department of Neurosurgery, Osaka Metropolitan University Graduate School of Medicine, Osaka, Japan; and.
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