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Mandibular helical axis pathways during mastication.


Gallo, L M; Fushima, K; Palla, S (2000). Mandibular helical axis pathways during mastication. Journal of Dental Research, 79(8):1566-1572.

Abstract

Condylar and incisor trajectories are often used for the study of mandibular movements. Condylar trajectories, however, depend on the location of the reference point and can be interpreted erroneously. In contrast, the helical axis analysis yields an unequivocal description of rigid body kinematics. The aim of this study was to analyze the mandibular helical axis during mastication. Seven subjects without signs and symptoms of craniomandibular disorders and with class I occlusion were recorded by means of the opto-electronic system Jaws-3D during unilateral mastication of bread cubes (2-cm side). The helical axis was computed every 14 ms with a rotation threshold of 1 . Parameters describing its spatial orientation and position relative to the condyles were calculated. The helical axis changed orientation and position more pronouncedly during the closing than during the opening phases of mastication. The orientation varied significantly from beginning to end of closing but not of opening, indicating less fluctuation of the helical axis on opening than on closing. Also, the distance dCP between helical axis and reference condylar point varied more significantly (p < 0.05) on the working than on the balancing side: On the working side, dCP decreased during both opening and closing, whereas on the balancing side, dCP increased only for closing. Furthermore, the helical axis pathway often showed a bowing ventrally to the balancing condyle, indicating that, during closing, the balancing condyle still translated backward while essentially only rotation occurred around the working condyle. Thus, the helical axis changed its position and orientation continuously during mastication.

Condylar and incisor trajectories are often used for the study of mandibular movements. Condylar trajectories, however, depend on the location of the reference point and can be interpreted erroneously. In contrast, the helical axis analysis yields an unequivocal description of rigid body kinematics. The aim of this study was to analyze the mandibular helical axis during mastication. Seven subjects without signs and symptoms of craniomandibular disorders and with class I occlusion were recorded by means of the opto-electronic system Jaws-3D during unilateral mastication of bread cubes (2-cm side). The helical axis was computed every 14 ms with a rotation threshold of 1 . Parameters describing its spatial orientation and position relative to the condyles were calculated. The helical axis changed orientation and position more pronouncedly during the closing than during the opening phases of mastication. The orientation varied significantly from beginning to end of closing but not of opening, indicating less fluctuation of the helical axis on opening than on closing. Also, the distance dCP between helical axis and reference condylar point varied more significantly (p < 0.05) on the working than on the balancing side: On the working side, dCP decreased during both opening and closing, whereas on the balancing side, dCP increased only for closing. Furthermore, the helical axis pathway often showed a bowing ventrally to the balancing condyle, indicating that, during closing, the balancing condyle still translated backward while essentially only rotation occurred around the working condyle. Thus, the helical axis changed its position and orientation continuously during mastication.

Citations

28 citations in Web of Science®
32 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed
Communities & Collections:04 Faculty of Medicine > Center for Dental Medicine > Clinic for Masticatory Disorders and Complete Dentures, Geriatric and Special Care Dentistry
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:1 August 2000
Deposited On:11 Feb 2008 12:23
Last Modified:05 Apr 2016 12:19
Publisher:Sage Publications
ISSN:0022-0345
Publisher DOI:10.1177/00220345000790080701
Related URLs:http://jdr.iadrjournals.org/cgi/content/abstract/79/8/1566?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&author1=palla+%2C+s&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT
PubMed ID:11023276

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