Rocker jaws

Houghton, Philip

doi:10.1002/ajpa.1330470303

Cited by 15 publications

(13 citation statements)

References 3 publications

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“…It is also possible that an increased vertical jaw depth is required in the human mandible when it is called upon to produce high, molar biting forces. The Polynesian "rocker jaw," for example, is characterized by a continuously curved lower border without an antegonial notch (i.e., an increased vertical depth), and has a vertically oriented, high ramus (Houghton, 1977(Houghton, , 1978. This unique shape is thought to be an adaptive response to the combined influences of the open cranial base angle and large vertical facial development found in Polynesians (Kean and Houghton, 1990).…”

mentioning

confidence: 99%

Three‐dimensional finite element stress analysis of the dentate human mandible

Korioth

Romilly

Hannam

1992

American J Phys Anthropol

292

211

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The biomechanical events which accompany functional loading of the human mandible are not fully understood. The techniques normally used to record them are highly invasive. Computer modelling offers a promising alternative approach in this regard, with the additional ability to predict regional stresses and strains in inaccessible locations. In this study, we built two three-dimensional finite element (FE) models of a human mandible reconstructed from tomographs of a dry dentate jaw. The first model was used for a complete mechanical characterization of physical events. It also provided comparative data for the second model, which had an increased vertical corpus depth. In both cases, boundary conditions included rigid restraints at the first right molar and endosteal cortical surfaces of the articular eminences of temporal bones. Groups of parallel multiple vectors simulated individual masticatory muscle loads. The models were solved for displacements, stresses, strains, and forces. The simulated muscle loads in the first model deformed the mandible helically upward and toward its right (working) side. The highest principal stresses occurred at the bite point, anterior aspects of the coronoid processes, symphyseal region, and right and left sides of the mandibular corpus. In general, the observed principal stresses and strains were highest on the periosteal cortical surface and alveolar bone. At the symphyseal region, maximum principal stresses and strains were highest on the lower lingual mandibular aspect, whereas minimum principal stresses and strains were highest on its upper labial side. Subcondylar principal strains and condylar forces were higher on the left (balancing or nonbiting) side than on the right mandibular side, with condylar forces more concentrated on the anteromedial aspect of the working-side condyle and on the central and lateral aspects of the left. When compared with in vivo strain data from macaques during comparable biting events, the predictive strain values from the first model were qualitatively similar. In the second model, the reduced tensile stress on the working-side, and decreased shear stress bilaterally, confirmed that lower stresses occurred on the lower mandibular border with increased jaw depth. Our results suggested that although the mandible behaved in a beam-like manner, its corpus acted more like a combination of open and closed cross sections due to the presence of tooth sockets, at least for the task modelled.(ABSTRACT TRUNCATED AT 400 WORDS)

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mentioning

confidence: 99%

Three‐dimensional finite element stress analysis of the dentate human mandible

Korioth

Romilly

Hannam

1992

American J Phys Anthropol

292

211

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“…The mandible does not overtly display a 'rocker jaw' morphology-the lower border has an indication of convexity from front to back, but the gonial angle (120.5°) is larger than that associated with the 'rocker' morphology displayed in pre-historical New Zealand remains measured by Houghton (1977): mean gonial angle of female rocker jaws (n=63): 97.85°, SD 4.05; mean gonial angle of females lacking rocker jaws (n=18): 102.20°, SD 4.05). That the gonial angle is also considerably larger than Houghton's non-rocker jaw values is curious, but it should be noted that Houghton's sample of pre-historical female remains lacking rocker jaws is fairly small (n=18).…”

Section: Jawmentioning

confidence: 95%

“…Two studies have been undertaken on the remains, including the field observations of Roger Duff during excavation (1950Duff during excavation ( , 1956 and detailed laboratory analysis by Philip Houghton (1975Houghton ( , 1977. In April 2009, the Wairau Bar tupuna (ancestors) were repatriated to the iwi Rangitane, the custodians of the site, and ceremonially reburied.…”

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confidence: 99%

Approximating the Face of ‘Aunty’: A Question of Likeness

Hayes

Buckley

Bradley³

et al. 2011

J Archaeol Method Theory

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This paper describes two approaches to the facial approximation of three individuals from the Wairau Bar burial site (New Zealand). Two individuals were approximated working in direct reference to the remains and incorporated manual drafting. The third individual, 'Aunty' (the respectful title given by the iwi Rangitane elders) was approximated from CT scans and using computer graphics. The computer graphic approach enabled a greater level of precision in the application of the research and recommendations that inform a facial approximation, and facilitated collaboration with appropriate expertise. The computer-graphic approach, however, also resulted in a more photographic facial appearance, which can imply a greater level of knowledge about hard/soft tissue relationships than is currently available.

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“…Rocker shape jaws are seen in some populations at puberty due to increased muscular force with growth [7]. The mandible loses the antigonial notch and the angle becomes more convex in appearance [8]. Overall, these studies all point to the conclusion that there is an influence of masticatory muscle function on craniofacial growth.…”

Section: Muscle Function Alters Craniofacial Formmentioning

confidence: 99%

Masseter function and skeletal malocclusion

Sciote

Raoul

Ferri

et al. 2013

Revue de Stomatologie, de Chirurgie Maxillo-faciale et de Chiru

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Summary The aim of this work is to review the relationship between the function of the masseter muscle and the occurrence of malocclusions. An analysis was made of the masseter muscle samples from subjects who underwent mandibular osteotomies. The size and proportion of type-II fibers (fast) decreases as facial height increases. Patients with mandibular asymmetry have more type-II fibers on the side of their deviation. The insulin-like growth factor and myostatin are expressed differently depending on the sex and fiber diameter. These differences in the distribution of fiber types and gene expression of this growth factor may be involved in long-term postoperative stability and require additional investigations. Muscle strength and bone length are two genetically determined factors in facial growth. Myosin 1H (MYOH1) is associated with prognathia in Caucasians. As future objectives, we propose to characterize genetic variations using “Genome Wide Association Studies” data and their relationships with malocclusions.

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Rocker jaws

Cited by 15 publications

References 3 publications

Three‐dimensional finite element stress analysis of the dentate human mandible

Three‐dimensional finite element stress analysis of the dentate human mandible

Approximating the Face of ‘Aunty’: A Question of Likeness

Masseter function and skeletal malocclusion

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