Jaw mechanics in dolichofacial and brachyfacial phenotypes: A longitudinal cephalometric-based study

Laura Iwasaki, Y. Liu, H. Liu, Jeffrey Nickel

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Objectives: To determine whether dolichofacial (Frankfort horizontal mandibular plane angle (FHMPA) ≥30°) vs brachyfacial (FHMPA ≤22°) phenotypes differ in temporomandibular joint (TMJ) loads and whether these differences correlate longitudinally with mandibular ramus height (Condylion-Gonion, Co-Go). Setting and Sample Population: Lateral and posteroanterior cephalographs from ten dolichofacial and ten brachyfacial individuals made at average ages of 6 (T1), 12 (T2) and 18 (T3) years and available online (http://www.aaoflegacycollection.org/aaof_home.html) were used. Materials and Methods: Three-dimensional anatomical data were derived from cephalographs and used in numerical models to predict TMJ loads for a range of biting angles on incisors, canines and first molars. Two criteria were used to define clinically important between-group TMJ load differences: statistical significance was defined with a two-group t-test, and where differences were also ≥20%. A statistical approach called response surface analysis was used to assess correlation between TMJ loads and its predictors considered in this study. Results: The two phenotypes had significantly different FHMPA at all ages (P<.05). No differences in TMJ loads were found at T1. Ipsilateral and contralateral TMJ loads at T2 and T3 were significant and ≥20% larger in dolichofacial than brachyfacial phenotypes for specific biting angles (all adjusted P<.05). Regression analysis indicated age and ramus height contribute 53% of the variability in normalized values of TMJ loads. At higher ages, dolichofacial phenotypes had significantly higher TMJ loads which were correlated with shorter ramus heights compared to brachyfacial phenotypes. Conclusions: Craniofacial mechanics may explain, in part, mandibular growth differences between dolichofacial and brachyfacial phenotypes.

Original languageEnglish (US)
Pages (from-to)145-150
Number of pages6
JournalOrthodontics and Craniofacial Research
Volume20
DOIs
StatePublished - Jun 1 2017
Externally publishedYes

Fingerprint

Cephalometry
Temporomandibular Joint
Jaw
Mechanics
Phenotype
Incisor
Canidae
Regression Analysis

Keywords

  • growth
  • loads
  • longitudinal
  • mandible
  • temporomandibular joint

ASJC Scopus subject areas

  • Orthodontics
  • Surgery
  • Oral Surgery
  • Otorhinolaryngology

Cite this

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title = "Jaw mechanics in dolichofacial and brachyfacial phenotypes: A longitudinal cephalometric-based study",
abstract = "Objectives: To determine whether dolichofacial (Frankfort horizontal mandibular plane angle (FHMPA) ≥30°) vs brachyfacial (FHMPA ≤22°) phenotypes differ in temporomandibular joint (TMJ) loads and whether these differences correlate longitudinally with mandibular ramus height (Condylion-Gonion, Co-Go). Setting and Sample Population: Lateral and posteroanterior cephalographs from ten dolichofacial and ten brachyfacial individuals made at average ages of 6 (T1), 12 (T2) and 18 (T3) years and available online (http://www.aaoflegacycollection.org/aaof_home.html) were used. Materials and Methods: Three-dimensional anatomical data were derived from cephalographs and used in numerical models to predict TMJ loads for a range of biting angles on incisors, canines and first molars. Two criteria were used to define clinically important between-group TMJ load differences: statistical significance was defined with a two-group t-test, and where differences were also ≥20{\%}. A statistical approach called response surface analysis was used to assess correlation between TMJ loads and its predictors considered in this study. Results: The two phenotypes had significantly different FHMPA at all ages (P<.05). No differences in TMJ loads were found at T1. Ipsilateral and contralateral TMJ loads at T2 and T3 were significant and ≥20{\%} larger in dolichofacial than brachyfacial phenotypes for specific biting angles (all adjusted P<.05). Regression analysis indicated age and ramus height contribute 53{\%} of the variability in normalized values of TMJ loads. At higher ages, dolichofacial phenotypes had significantly higher TMJ loads which were correlated with shorter ramus heights compared to brachyfacial phenotypes. Conclusions: Craniofacial mechanics may explain, in part, mandibular growth differences between dolichofacial and brachyfacial phenotypes.",
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author = "Laura Iwasaki and Y. Liu and H. Liu and Jeffrey Nickel",
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TY - JOUR

T1 - Jaw mechanics in dolichofacial and brachyfacial phenotypes

T2 - A longitudinal cephalometric-based study

AU - Iwasaki, Laura

AU - Liu, Y.

AU - Liu, H.

AU - Nickel, Jeffrey

PY - 2017/6/1

Y1 - 2017/6/1

N2 - Objectives: To determine whether dolichofacial (Frankfort horizontal mandibular plane angle (FHMPA) ≥30°) vs brachyfacial (FHMPA ≤22°) phenotypes differ in temporomandibular joint (TMJ) loads and whether these differences correlate longitudinally with mandibular ramus height (Condylion-Gonion, Co-Go). Setting and Sample Population: Lateral and posteroanterior cephalographs from ten dolichofacial and ten brachyfacial individuals made at average ages of 6 (T1), 12 (T2) and 18 (T3) years and available online (http://www.aaoflegacycollection.org/aaof_home.html) were used. Materials and Methods: Three-dimensional anatomical data were derived from cephalographs and used in numerical models to predict TMJ loads for a range of biting angles on incisors, canines and first molars. Two criteria were used to define clinically important between-group TMJ load differences: statistical significance was defined with a two-group t-test, and where differences were also ≥20%. A statistical approach called response surface analysis was used to assess correlation between TMJ loads and its predictors considered in this study. Results: The two phenotypes had significantly different FHMPA at all ages (P<.05). No differences in TMJ loads were found at T1. Ipsilateral and contralateral TMJ loads at T2 and T3 were significant and ≥20% larger in dolichofacial than brachyfacial phenotypes for specific biting angles (all adjusted P<.05). Regression analysis indicated age and ramus height contribute 53% of the variability in normalized values of TMJ loads. At higher ages, dolichofacial phenotypes had significantly higher TMJ loads which were correlated with shorter ramus heights compared to brachyfacial phenotypes. Conclusions: Craniofacial mechanics may explain, in part, mandibular growth differences between dolichofacial and brachyfacial phenotypes.

AB - Objectives: To determine whether dolichofacial (Frankfort horizontal mandibular plane angle (FHMPA) ≥30°) vs brachyfacial (FHMPA ≤22°) phenotypes differ in temporomandibular joint (TMJ) loads and whether these differences correlate longitudinally with mandibular ramus height (Condylion-Gonion, Co-Go). Setting and Sample Population: Lateral and posteroanterior cephalographs from ten dolichofacial and ten brachyfacial individuals made at average ages of 6 (T1), 12 (T2) and 18 (T3) years and available online (http://www.aaoflegacycollection.org/aaof_home.html) were used. Materials and Methods: Three-dimensional anatomical data were derived from cephalographs and used in numerical models to predict TMJ loads for a range of biting angles on incisors, canines and first molars. Two criteria were used to define clinically important between-group TMJ load differences: statistical significance was defined with a two-group t-test, and where differences were also ≥20%. A statistical approach called response surface analysis was used to assess correlation between TMJ loads and its predictors considered in this study. Results: The two phenotypes had significantly different FHMPA at all ages (P<.05). No differences in TMJ loads were found at T1. Ipsilateral and contralateral TMJ loads at T2 and T3 were significant and ≥20% larger in dolichofacial than brachyfacial phenotypes for specific biting angles (all adjusted P<.05). Regression analysis indicated age and ramus height contribute 53% of the variability in normalized values of TMJ loads. At higher ages, dolichofacial phenotypes had significantly higher TMJ loads which were correlated with shorter ramus heights compared to brachyfacial phenotypes. Conclusions: Craniofacial mechanics may explain, in part, mandibular growth differences between dolichofacial and brachyfacial phenotypes.

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