ABSTRACT

Objectives

To test the hypotheses that mechanobehavior scores (MBS) were correlated with mandibular ramus lengths (Co-Go) and differed between facial phenotypes.

Materials and Methods

Subjects gave informed consent to participate. Co-Go (mm), mandibular plane angles (SN-GoGn, °), and three-dimensional anatomy were derived from cephalometric radiography or cone beam computed tomography. Temporomandibular joint (TMJ) energy densities (ED) (mJ/mm3) were measured using dynamic stereometry and duty factors (DF) (%) were measured from electromyography, to calculate MBS (= ED2 × DF,) for each TMJ. Polynomial regressions, K-means cluster analysis, and analysis of variance (ANOVA) with Tukey post-hoc tests were employed.

Results

Fifty females and 23 males produced replete data. Polynomial regressions showed MBS were correlated with Co-Go (females, R2 = 0.57; males, R2 = 0.81). Cluster analysis identified three groups (P < .001). Dolichofacial subjects, with shorter normalized Co-Go, clustered into two subgroups with low and high MBS compared to brachyfacial subjects with longer Co-Go. SN-GoGn was significantly larger (P < .03) in the dolichofacial subgroups combined (33.0 ± 5.9°) compared to the brachyfacial group (29.8 ± 5.5°).

Conclusions

MBS correlated with Co-Go within sexes and differed significantly between brachyfacial and dolichofacial subjects.

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Author notes

a

Private Practice, Leawood, Kansas, USA.

b

Professor-Provisional, Department of Orthodontics, School of Dentistry, Oregon Health & Science University, Portland, Oregon, USA; and Research Associate Professor, Department of Oral Diagnostic Sciences, University at Buffalo, School of Dental Medicine, Buffalo, New York, USA.

c

Assistant Professor, Department of Biostatistics and Epidemiology, College of Public Health, East Tennessee State University, Johnson City, Tennessee, USA.

d

Associate Professor, Department of Oral Diagnostic Sciences, University at Buffalo, School of Dental Medicine, Buffalo, New York, USA.

e

Professor, Physiology and Biomechanics of the Masticatory System, Dental School, Faculty of Medicine, University of Zurich, Zurich, Switzerland.

f

Private Practice, Washington, Pennsylvania, USA.

g

Statistician, University of Buffalo Microbiome Center, School of Dental Medicine, Buffalo, New York, USA.

h

Senior Research Associate, Department of Orthodontics, School of Dentistry, Oregon Health & Science University, Portland, Oregon, USA.