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Aspects of morphology and guidance of the human temporomandibular joint
ARTICLE IN PRESS Ann Anat 189 (2007) 339—341
www.elsevier.de/aanat
Aspects of morphology and guidance of the human temporomandibular joint Dankmar Ihlowa,, Dietmar Kubein-Meesenburga, Jochen Fangha ¨nelb, Kirsten M. Thiemea, Wolfram Hahna, Henning Dathea, Susanne Zecha, Hans Na ¨gerla a
Department of Orthodontics, Georg-August-University of Go ¨ttingen, Robert-Koch-Straße 40, D-37099 Go ¨ttingen, Germany b Department of Oral Anatomy, Ernst-Moritz-Arndt-University of Greifswald, Rotgerberstraße 8, D-17487 Greifswald, Germany Received 21 December 2006; accepted 20 February 2007
KEYWORDS Temporomandibular joint; Morphology of the TMJ; Cranial border function of the TMJ; Dimeric link chain
Summary Examinations of the curvature morphology of the temporomandibular joints (TMJs) in macerated human skulls yielded that in initial protrusive cranial border motion, parts of the condylar articulating surfaces are only functional under force transmission. These areas were found on the lateral–central side of the condyle. In contrast to the Cercopithecus mona, a monkey species, the human TMJ apparently possesses a distinctly higher spatial performance range. & 2007 Elsevier GmbH. All rights reserved.
Introduction In protrusive and retrusive cranial motion, the temporomandibular joint (TMJ) couples under occlusal–articular force transmission to a constraint gear system with the appropriate anterior guidance, provided by teeth contact. Its function could be mapped to a link quadrangle for the initial protrusive cranial border motion (Kubein-MeesenCorresponding author. Tel.: +49 551 398344;
fax: +49 551 398350. E-mail address: [email protected] (D. Ihlow).
burg et al., 1988) whose posterior parameters are determined by the morphology of the TMJ. We wondered how morphological structures of the TMJ resulting from parallel sagittal sections are related to the cranial border function.
Material and methods Contours of sagittal sections through the osseous structures of 22 left and right TMJs of macerated human skulls (collection of the Institute of Anatomy, Greifswald) were measured. The skulls
0940-9602/$ - see front matter & 2007 Elsevier GmbH. All rights reserved. doi:10.1016/j.aanat.2007.02.007
ARTICLE IN PRESS 340
D. Ihlow et al.
Results The variance analysis did not significantly differentiate the radii of the condyle or the eminence with respect to the medial (I), central (II), or lateral (III) slice. Using the paired t-test, in all slices the radii of the eminence did not differ. The mean radii of the condyle showed no statistically significant difference between slices I and II. The respective differences between slices II and III or between slices I and III, however, were significant (p ¼ 0.012 or p ¼ 0.038, resp.). The medial radius was the smallest. The inclinations of the DLC lines to the FP were medial 33.21 (SD: 7.21), central 29.01 (SD: 6.51), and lateral 29.31 (SD: 5.91). The angles differed significantly. The inclination in the medial slice was at po0.025 (standard of significance) higher than that of the two other cuts.
Figure 1. Superimposed three slices (medial I, central II, and lateral III) of a right and a left TMJ. Approximated circles of the condyle and the eminence as well as the resulting DLC lines (300% enlarged).
showed complete dentition. Thus, the mandible could be related to the maxilla in centric occlusion (CO). We supposed the physiological state that CO would meet centric relation. Clinically proven impression techniques were employed to take the geometrical arrangement of condyle and os temporale. The silicone impressions were aligned to the Frankfort plane (FP) and the sagittal–vertical plane (reference planes). We assumed that the centres of curvatures of the bony joint surfaces coincided in good approximation with those of the vanished cartilaginous surfaces (Hansson et al., 1977). The negative casts were positively converted and again carefully aligned to the reference planes. The positive casts were cut in parallel to the sagittal– vertical plane at 25%, 50%, and 75% of the transversal condyle width. The slices were scanned, enlarged (300%), and measured. Collected data: (a) The coordinates of the curvature centres of the respective contour of condyle and eminence in the sagittal–vertical plane, (b) the distances of the curvature centres ( ¼ the lengths of the respective dimeric link chains (DLC)), and (c) the angles between the DLC and the FP. Figure 1 shows an example of the approximated circle-like contours of condyle and eminence as well as the resulting DLC lines for the three slices of a right and left TMJ.
Discussion Theoretical implication: In the initial protrusive cranial border function out of CO that part of the condylar articular surface takes the guidance whose respective DCL line includes the smallest angle with the FP because this guidance forces the condyle to run along the steepest path. Since the medial and the lateral slices yielded DLC lines the inclinations of which took the minimum, the dominating guidance seemed to be located at the medial–lateral part of the condyle. By this relatively small joint contact area, the joint gains considerable freedom for laterotrusion. These findings are in contrast with the morphological outcomes concerning the guidance of the TMJ of the Cercopithecus mona, a monkey species. Here, the DLCs are practically arranged in parallel over the complete width of the joint. Zech et al. (2007) found the following inclinations: Medial 49.91 (SD: 12.21), central 49.41 (SD: 10.11), and lateral 49.31 (SD: 9.21). The condyle seemed to be shaped rather like a roller. The generally high capacity of spatial motion of the human mandible possibly requires extensive spatial changes in the position of the disc.
References ¨ berg, T., Carlsson, G.E., Kopp, S., 1977. Hansson, T., O Thickness of the soft tissue layers and the articular disk in the temporo-mandibular joint. Acta Odont. Scand. 35, 77.
ARTICLE IN PRESS Morphology and guidance of human TMJ Kubein-Meesenburg, D., Na ¨gerl, H., Klamt, B., 1988. The biomechanical relation between incisal and condylar guidance in man. J. Biomech. 21, 997–1009. Zech, S., Fricke, J., Fangha ¨nel, J., Dathe, H., Ihlow, D., Thieme, K.M., Kubein-Meesenburg, D., Na ¨gerl, H.,
341 2007. Morphological structures and protrusive cranial border guidance of the temporomandibular joint of Cercopithecus mona. Ann. Anatomy (2007), doi:10.1016/j.aanat.2007.02.006.
www.elsevier.de/aanat
Aspects of morphology and guidance of the human temporomandibular joint Dankmar Ihlowa,, Dietmar Kubein-Meesenburga, Jochen Fangha ¨nelb, Kirsten M. Thiemea, Wolfram Hahna, Henning Dathea, Susanne Zecha, Hans Na ¨gerla a
Department of Orthodontics, Georg-August-University of Go ¨ttingen, Robert-Koch-Straße 40, D-37099 Go ¨ttingen, Germany b Department of Oral Anatomy, Ernst-Moritz-Arndt-University of Greifswald, Rotgerberstraße 8, D-17487 Greifswald, Germany Received 21 December 2006; accepted 20 February 2007
KEYWORDS Temporomandibular joint; Morphology of the TMJ; Cranial border function of the TMJ; Dimeric link chain
Summary Examinations of the curvature morphology of the temporomandibular joints (TMJs) in macerated human skulls yielded that in initial protrusive cranial border motion, parts of the condylar articulating surfaces are only functional under force transmission. These areas were found on the lateral–central side of the condyle. In contrast to the Cercopithecus mona, a monkey species, the human TMJ apparently possesses a distinctly higher spatial performance range. & 2007 Elsevier GmbH. All rights reserved.
Introduction In protrusive and retrusive cranial motion, the temporomandibular joint (TMJ) couples under occlusal–articular force transmission to a constraint gear system with the appropriate anterior guidance, provided by teeth contact. Its function could be mapped to a link quadrangle for the initial protrusive cranial border motion (Kubein-MeesenCorresponding author. Tel.: +49 551 398344;
fax: +49 551 398350. E-mail address: [email protected] (D. Ihlow).
burg et al., 1988) whose posterior parameters are determined by the morphology of the TMJ. We wondered how morphological structures of the TMJ resulting from parallel sagittal sections are related to the cranial border function.
Material and methods Contours of sagittal sections through the osseous structures of 22 left and right TMJs of macerated human skulls (collection of the Institute of Anatomy, Greifswald) were measured. The skulls
0940-9602/$ - see front matter & 2007 Elsevier GmbH. All rights reserved. doi:10.1016/j.aanat.2007.02.007
ARTICLE IN PRESS 340
D. Ihlow et al.
Results The variance analysis did not significantly differentiate the radii of the condyle or the eminence with respect to the medial (I), central (II), or lateral (III) slice. Using the paired t-test, in all slices the radii of the eminence did not differ. The mean radii of the condyle showed no statistically significant difference between slices I and II. The respective differences between slices II and III or between slices I and III, however, were significant (p ¼ 0.012 or p ¼ 0.038, resp.). The medial radius was the smallest. The inclinations of the DLC lines to the FP were medial 33.21 (SD: 7.21), central 29.01 (SD: 6.51), and lateral 29.31 (SD: 5.91). The angles differed significantly. The inclination in the medial slice was at po0.025 (standard of significance) higher than that of the two other cuts.
Figure 1. Superimposed three slices (medial I, central II, and lateral III) of a right and a left TMJ. Approximated circles of the condyle and the eminence as well as the resulting DLC lines (300% enlarged).
showed complete dentition. Thus, the mandible could be related to the maxilla in centric occlusion (CO). We supposed the physiological state that CO would meet centric relation. Clinically proven impression techniques were employed to take the geometrical arrangement of condyle and os temporale. The silicone impressions were aligned to the Frankfort plane (FP) and the sagittal–vertical plane (reference planes). We assumed that the centres of curvatures of the bony joint surfaces coincided in good approximation with those of the vanished cartilaginous surfaces (Hansson et al., 1977). The negative casts were positively converted and again carefully aligned to the reference planes. The positive casts were cut in parallel to the sagittal– vertical plane at 25%, 50%, and 75% of the transversal condyle width. The slices were scanned, enlarged (300%), and measured. Collected data: (a) The coordinates of the curvature centres of the respective contour of condyle and eminence in the sagittal–vertical plane, (b) the distances of the curvature centres ( ¼ the lengths of the respective dimeric link chains (DLC)), and (c) the angles between the DLC and the FP. Figure 1 shows an example of the approximated circle-like contours of condyle and eminence as well as the resulting DLC lines for the three slices of a right and left TMJ.
Discussion Theoretical implication: In the initial protrusive cranial border function out of CO that part of the condylar articular surface takes the guidance whose respective DCL line includes the smallest angle with the FP because this guidance forces the condyle to run along the steepest path. Since the medial and the lateral slices yielded DLC lines the inclinations of which took the minimum, the dominating guidance seemed to be located at the medial–lateral part of the condyle. By this relatively small joint contact area, the joint gains considerable freedom for laterotrusion. These findings are in contrast with the morphological outcomes concerning the guidance of the TMJ of the Cercopithecus mona, a monkey species. Here, the DLCs are practically arranged in parallel over the complete width of the joint. Zech et al. (2007) found the following inclinations: Medial 49.91 (SD: 12.21), central 49.41 (SD: 10.11), and lateral 49.31 (SD: 9.21). The condyle seemed to be shaped rather like a roller. The generally high capacity of spatial motion of the human mandible possibly requires extensive spatial changes in the position of the disc.
References ¨ berg, T., Carlsson, G.E., Kopp, S., 1977. Hansson, T., O Thickness of the soft tissue layers and the articular disk in the temporo-mandibular joint. Acta Odont. Scand. 35, 77.
ARTICLE IN PRESS Morphology and guidance of human TMJ Kubein-Meesenburg, D., Na ¨gerl, H., Klamt, B., 1988. The biomechanical relation between incisal and condylar guidance in man. J. Biomech. 21, 997–1009. Zech, S., Fricke, J., Fangha ¨nel, J., Dathe, H., Ihlow, D., Thieme, K.M., Kubein-Meesenburg, D., Na ¨gerl, H.,
341 2007. Morphological structures and protrusive cranial border guidance of the temporomandibular joint of Cercopithecus mona. Ann. Anatomy (2007), doi:10.1016/j.aanat.2007.02.006.