title: The effect of vertical dimension and mandibular position on isometric strength of the cervical flexors.
abstract: This study compared the peak isometric strength of the cervical flexors in deep bite temporomandibular dysfunction (TMD) patients while biting in four bite positions: habitual occlusion, edge-to-edge, lateral shift and retruded. These values were then compared to those of the same subjects' bite positions elevated to a functional criterion (maximum isometric strength of the deltoid muscles). The mean height increase was 2.4 mm with a range of 1.5-3.8 mm. Fifteen of eighteen deep bite subjects met an inclusionary criterion, at least 13.3 Newtons (N) stronger cervical muscle strength with mandible relaxed open than habitual bite. Peak strength biting edge-to-edge was significantly greater than biting in habitual occlusion. Strength was found to increase significantly when biting in each of four mandibular positions when the bite was elevated to the functional criterion. The greatest strength was obtained from elevated habitual and edge-to-edge positions. The findings are of clinical significance, suggesting that cervical muscle isometric strength is affected by bite position and vertical dimension of occlusion. The results suggest that when biting, individuals with deep bite may be functioning at about 60% of their potential cervical flexor, isometric strength. The interaction between occlusal position, vertical dimension and cervical muscle function suggests a craniomandibular-cervical masticatory system.
authors.affiliation: Implant Center, Tufts University School of Dental Medicine, Massachusetts 02111, USA.
authors.forename: H
authors.initials: H
authors.lastname: al-Abbasi
authors.forename: N R
authors.initials: NR
authors.lastname: Mehta
authors.forename: A G
authors.initials: AG
authors.lastname: Forgione
authors.forename: R E
authors.initials: RE
authors.lastname: Clark
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001732:Bite Force; D016009:Chi-Square Distribution; D003799:Dental Stress Analysis; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008310:Malocclusion / Q000150:complications* / Q000503:physiopathology; D008334:Mandible / Q000502:physiology; D008875:Middle Aged; D009334:Neck Muscles / Q000502:physiology* / Q000503:physiopathology; D013706:Temporomandibular Joint Dysfunction Syndrome / Q000209:etiology / Q000503:physiopathology*; D014716:Vertical Dimension