The Morphological Characteristics, Growth, and Etiology of the Hyperdivergent Phenotype

Buschang, Peter H.; Jacob, Helder B.; Carrillo, Roberto

doi:10.1053/j.sodo.2013.07.002

Cited by 37 publications

(40 citation statements)

References 94 publications

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“…The loss of mandibular space in the combined group is consistent with findings that report a greater loss of space in the mandible than in the maxilla, 2,6,7 possibly due to the combination of both mesial and distal movements into the extraction site. This finding is also consistent with studies [19][20][21][22][23] that have shown that weaker jaw muscles are associated with hyperdivergent individuals, who also display reduced muscle size, efficiency, and anchorage loss during orthodontic tooth movement. No space loss in the maxilla or mandible was observed in individuals with a Class I molar occlusion and mesoprosopic/ euryprosopic facial forms, indicating that space maintenance may not be necessary in patients with these clinical findings.…”

Section: -13supporting

confidence: 81%

The premature loss of primary first molars: Space loss to molar occlusal relationships and facial patterns

Alexander

Askari

Lewis

2015

The Angle Orthodontist

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Objective: To investigate space changes with the premature loss of primary first molars and their relationship to permanent molar occlusion and facial forms. Materials and Methods: Two hundred twenty-six participants (ranging in age from 7 years 8 months to 8 years 2 months; 135 female, 91 male) met all inclusion criteria designed to study space loss as a result of the premature loss of the primary first molar. After 9 months, space loss was evaluated in relationship to molar occlusion and facial form. Statistical evaluation was performed with the paired t-test and with a two-way analysis of variance for independent groups. Results: Patients with leptoprosopic facial form and end-on molar occlusions all exhibited a statistically significant difference when compared to controls in terms of space loss (P , .001). The mandibular extraction site for individuals with a mesoprosopic/euryprosopic facial form and end-on molar occlusion displayed space loss as well (P , .05). All patients with a leptoprosopic facial form and Class I molar occlusion displayed space loss in the maxilla (P , .05) and the mandible (P , .001) respectively, that was statistically significant when compared to that of the control. Individuals within the mesoprosopic/euryprosopic group and with Class I molar occlusions showed no significant difference in space loss. Conclusions:The relationship between the first permanent molar occlusion and facial form of the child has an influence on the loss of space at the primary first molar site. (Angle Orthod. 2015;85:218-223.)

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Section: -13supporting

confidence: 81%

The premature loss of primary first molars: Space loss to molar occlusal relationships and facial patterns

Alexander

Askari

Lewis

2015

The Angle Orthodontist

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“…In contrast, reduced chin prominence is more closely associated with a pattern of backward mandibular rotation. Variation in mandibular rotation and associated correlated symphyseal form are tied to the complex interaction of mandibular posture, dentoalveolar development and the direction of growth of the condylar cartilage ( € Odegaard, 1970a,b;Lavergne & Gasson, 1976;Buschang & Gandini, 2002;Araujo et al 2004;Buschang et al 2013). In addition, variation in chin prominence has also been tied to differential anterior-posterior dimensions of the dentoalveolar complex and the lower border of the mandible both during ontogeny (Marshall et al 2011) and across broader ranges of population variation (Scott et al 2010;Scott, 2014).…”

Section: Introductionmentioning

confidence: 99%

The ontogeny of the chin: an analysis of allometric and biomechanical scaling

et al. 2015

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The presence of a prominent chin in modern humans has been viewed by some researchers as an architectural adaptation to buttress the anterior corpus from bending stresses during mastication. In contrast, ontogenetic studies of mandibular symphyseal form suggest that a prominent chin results from the complex spatial interaction between the symphysis and surrounding soft tissue and skeletal anatomy during development. While variation in chin prominence is clearly influenced by differential growth and spatial constraints, it is unclear to what degree these developmental dynamics influence the mechanical properties of the symphysis. That is, do ontogenetic changes in symphyseal shape result in increased symphyseal bending resistance? We examined ontogenetic changes in the mechanical properties and shape of the symphysis using subjects from a longitudinal cephalometric growth study with ages ranging from 3 to 20+ years. We first examined whether ontogenetic changes in symphyseal shape were correlated with symphyseal vertical bending and wishboning resistance using multivariate regression. Secondly, we examined ontogenetic scaling of bending resistance relative to bending moment arm lengths. An ontogenetic increase in chin prominence was associated with decreased vertical bending resistance, while wishboning resistance was uncorrelated with ontogenetic development of the chin. Relative to bending moment arm lengths, vertical bending resistance scaled with significant negative allometry whereas wishboning resistance scaled isometrically. These results suggest a complex interaction between symphyseal ontogeny and bending resistance, and indicate that ontogenetic increases in chin projection do not provide greater bending resistance to the mandibular symphysis.

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“…The coronoid region is highly responsive to the temporalis muscle, while the angular region grows in concert with the masseter and pterygoid muscles. Relative to the other regions, the condyloid and basal regions show the greatest amount of ontogenetic autonomy; also, both provide the largest contributions to mandibular extension . Paramount to the formation of the modern human chin is the ontogenetic interaction between the basal and alveolar mandibular modules.…”

Section: Integrated Ontogeny Of the Chinmentioning

confidence: 99%

“…Relative to the other regions, the condyloid and basal regions show the greatest amount of ontogenetic autonomy; also, both provide the largest contributions to mandibular extension. [16][17][18][19][20] Paramount to the formation of the modern human chin is the ontogenetic interaction between the basal and alveolar mandibular modules. Before the eruption of the deciduous dentition, the labial symphyseal surface containing both the alveolar and basal regions is an area of bone deposition, a pattern conserved among anthropoids.…”

Section: Box 2 Chins Among the Neanderthalsmentioning

confidence: 99%

The enduring puzzle of the human chin

Pampush¹,

Daegling²

2016

Evolutionary Anthropology

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Although modern humans are considered to be morphologically distinct from other living primates because of our large brains, dexterous hands, and bipedal gait, all of these features are found among extinct hominins. The chin, however, appears to be a uniquely modern human trait. Probably because of the chin's exclusivity, many evolutionary scenarios have been proposed to explain its origins. To date, researchers have developed adaptive hypotheses relating chins to speech, mastication, and sexual selection; still others see it as a structural artifact tangentially related to complex processes involving evolutionary retraction of the midfacial skeleton. Consensus has remained elusive, partly because hypotheses purporting to explain how this feature developed uniquely in modern humans are all fraught with theoretical and/or empirical shortcomings. Here we review a century's worth of chin hypotheses and discuss future research avenues that may provide greater insight into this human peculiarity.

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The Morphological Characteristics, Growth, and Etiology of the Hyperdivergent Phenotype

Cited by 37 publications

References 94 publications

The premature loss of primary first molars: Space loss to molar occlusal relationships and facial patterns

The premature loss of primary first molars: Space loss to molar occlusal relationships and facial patterns

The ontogeny of the chin: an analysis of allometric and biomechanical scaling

The enduring puzzle of the human chin

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