| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Scientific Section |
Department of Orthodontics, Matsumoto Dental University School of Dentistry, 1780 Gohbara-Hirooka, Shiojiri city, Nagano-ken, Japan 399-0781
Department of Orthodontics, Eastman Dental Institute for Oral Health Care Sciences, University College London, 256 Gray's Inn Road, London WC1X 8LD, UK
Toshio Deguchi, International Centre for Excellence in Dentistry, Eastman Dental Institute for Oral Health Care Sciences, University College London, 123 Gray's Inn Road, London WC1X 8TZ, UK. Tel: +44(0)20-7-905-1219. Fax: +44(0)20-7-242-8685. E-mail: deguchi{at}po.mdu.ac.jp.
Abstract
The aetiology of asymmetric growth in the mandible is not well understood. Previous studies have indicated that the functional lateral shift of the mandible in the period of prepubertal growth may translate to a true skeletal asymmetry, exclusively in skeletal Class III malocclusion. This asymmetry develops more characteristic features during the pubertal and post-pubertal growth periods. Early correction of a functional lateral shift of the mandible is recommended. The purpose of this study was to examine the relationship between the morphology of the temporomandibular joints and asymmetry in skeletal Class III malocclusion in adult female patients.
Cephalometric and laminographic findings in 36 asymmetric skeletal Class III patients with a lateral shift of mandible (group 3) were compared to those of 25 symmetric skeletal Class I patients (group 1) and the same number of symmetric skeletal Class III malocclusions (group 2). All the patients had received no orthodontic treatment. The results showed that the TMJ of the side to which the mandible shifted showed a significantly narrower and shorter shape of the condyle head, smaller superior condylar space, and steeper eminence than those of the unshifted side.
Key words: Asymmetry, Laminography, Skeletal I, Skeletal III, TMJ
Introduction
The aetiology of asymmetric deformity of the mandible is not well understood (Erickson and Waite, 1974
). Genetics, functional side shift of the mandible, and unbalanced lateral and vertical growth of the craniofacial structures could be factors in the young growing patients (Sakuda et al., 1969; Kobayashi et al., 1996' Sugawara, 1996). Mandibular asymmetry is often associated with an asymmetric occlusal plane and is characteristically accelerated through the adolescent growth period (Widman, 1988). A few studies have suggested that the asymmetric morphology of the temporomandibular joint may cause asymmetric growth of the mandible (Mongini and Schmid, 1987; Aoshima et al., 1992; Satoh et al., 1993).
Skeletal Class III malocclusion in Japanese adolescents tends to show the asymmetry not only the mandible, but also condylar inclination when compared with those of Class I and Class II malocclusion, studying a Sectograph (Ogawa and Deguchi, 1991). Sagittal arthrotomograms, obtained with a cephalometric laminograph (Sectograph), show a clear image of the temporomandibular joint and are of value in the study of the morphological changes with time in individuals (Hayasaka et al., 1983).
There is still a lack of information in relation of TMJ morphology and asymmetrical skeletal Class III malocclusion. In the present study, sagittal arthrotomograms were designed to examine morphological differences of the condyles and mandibular fossae in both skeletal Class I and Class III patients with or without asymmetry of the mandible.
However, difficulties may arise in standardization of the sectograph, according to the method of X-ray projection (Ogawa et al., 1988). A pilot study was planned to evaluate the accuracy and utility of sectograph in TMJ morphology, using a dry skull. The magnification of the sliced image subject and the geometric distortion were also investigated.
Methods
The axial projected head plate
This projection was obtained to orientate the head with the axial X-ray projection perpendicular to the Frankfort plane and to assure the visualization of the sagittal plane across the center of the joint, using the laser analyser (Figure 1). The slice depth and the inclination of the slice path were measured on the tracings (Ogawa et al., 1988; Figure 2). The conditions of projection were a focus-film distance (150 cm), voltage (54 kV), currency (50 mA) and the exposure time (0•5 seconds).
|
|
).
|
) and the inclination of the slice (
) obtained from the axial projected head plate, with the sliced cut of the x-ray projection intersecting the center of the condylar head and perpendicular to its long axis. The conditions of the x-ray projection were as follows: a focus-film distance (160 cm), focus-mid point of ear rods (150 cm), voltage (54 kV), currency (50 mA), exposure time (3 seconds: Figure 4A,B).
|
). The distances were calculated to the second place of decimals. The same analysis was applied to the sectograph on the tracings.
|
). Alpha was calculated from the formula; = 
/1•1 (Figure 2
). The significance of the difference of the measurements from the skull and sectograph was statistically analysed with the Student's t-test, Statt-view, Abacus concepts Inc.).
Accuracy on sectograph
The measurements obtained from the dry skull and sectograph showed a small variation in each of the trials (Table 1). However, there was no significant difference between the measurements obtained from the dry skull multiplied by the theoretical magnification and the sectograph (Table 2). The theoretical magnification was close to the real magnification (right side; 1•032, left; 1•0.33).
|
The materials consisted of 25 skeletal Class I cases (group 1), 25 skeletal Class III symmetrical cases (group 2) and 36 skeletal Class III with mandibular asymmetry cases (group 3). All the subjects were female Japanese adults who had received no orthodontic treatment and showed no symptoms of TMJ disorder. The mean age of the patients was 22 years (range 16 years to 33 years) for group 1; 19 years (range 16 years to 29 years) for group 2 and 20 years (range 16 years to 29 years) for group 3 (Table 3). Growth is considered to be complete in Japanese females around 17 years of age (Asai, 1973).
|
).
|
). The median point of the cranium was marked on a line connecting the center of both spinous foramina. A perpendicular to this axis at the median point was then constructed as the facial midline (Marmary et al., 1979). The line through this median point to the mental spine was designated as the mid-sagittal mandibular plane.
The angle of these two planes was measured to determine the lateral shift of the mandible. The angle of shift value larger than ± 3•5 degrees was designated in asymmetrical skeletal class III malocclusion (group 3; Satoh et al., 1994; Figure 6).
|
; Mimura and Deguchi, 1994; Satoh et al., 1994). The FH plane and two lines parallel to the FH plane in contact with mandibular fossae and eminence were drawn on the tracings. Subsequently, a tangent to the posterior border of the ramus was drawn (the ramus plane). From the superior contact point of the ramus plane, a line parallel to the FH plane was drawn. On this line, the median point of the superior contact point and the point intersecting the anterior outline of the mandibular neck was marked. This was considered as the median point of the mandibular neck. A line parallel to the ramus plane, crossing the median point of mandibular neck, was drawn. This was designated as the condylar head angle.
The coefficient of reliability for almost all cephalometric parameters satisfied the level of confidence (<0•90), shown at Tables 4–6. A few results, however, had a low coefficient of reliability which should be evaluated with caution (Houston, 1983).
|
|
|
Results
Intra-group comparisons
Group 1 showed a significant difference between sides in the width of the fossae (P < 0•05) and also in the anterior condyle space (P < 0•05) in group 2 (Tables 4 and 5). Group 3 showed a significant difference between the sides in the eminence to FH angle, width of fossae, height of fossae, width of condyle (P < 0•05) and superior condyle space (P < 0•01; Table 6). In summary, TMJ morphology in the shifted side showed a steeper eminence to FH angle, smaller width of fossae, and smaller superior condyle space. The head of the condyle in the shifted side showed a shorter height and smaller width.
Inter-group comparisons
Comparison of group 1 and group 2 showed a statistical difference in the values of eminence to FH angle (P < 0•01) and superior condylar space (P < 0•05; Table 7).
|
Accuracy on sectograph
The pilot study based on a dry skull indicated that a Sectograph was an accurate sagittal arthrotomogram for representing the morphology of the TMJ.
TMJ morphology and skeletal pattern
This study showed significant differences in the values of the eminence to FH angle and superior condylar space between groups 1 and 2. There are a few reports that TMJ morphology has a strong correlation with skeletal morphology (Widman, 1988; Yamaki et al., 1990; Ogawa, 1991), and exclusively an inverse relationship between the angle of the articular eminence, and the occlusal and the mandibular planes (Widman, 1988). Skeletal Class III pattern tended to be more closely associated with the asymmetry of condylar inclination than skeletal I and II groups (Ogawa, 1991). The small angle of eminence to FH plane and the large superior condylar space in the asymmetric skeletal III subjects supports the finding that mandibular movement in skeletal class I is induced by the lingual surface of maxillary incisors at anterior guidance whereas on the other hand skeletal Class III does not have anterior guidance, showing the different eminence to FH angle and mandibular movement (Yamaki et al., 1990).
Asymmetry of TMJ and mandible
Group 3 showed a significant side difference in the morphology of the TMJ; a smaller superior condylar space with upward position of the condyle, shorter height and smaller width of the condyle being evident in the shifted side. For the non-shifted side, the condylar head was positioned downward in relation to the fossae and tended to be longer than that of the shifted side.
Studies associated with transcranial radiographs (Myers et al., 1980) and corrected tomograms (Hesse et al., 1997) have reported asymmetries in condylar position in the fossa in unilateral posterior crossbite children prior to treatment. However, Lam et al. (1999) was unable to demonstrate any differences in condylar position between the crossbite and Class I non-crossbite groups at pre- and post-treatment stages, demonstrating a large standard deviation.
Correction of a unilateral posterior cross bite eliminates the funcational side shift in children and allow the mandible to assume a symmetric position (Myers et al., 1980; Pullinger et al., 1985; Ishii, 1992; Hesse et al., 1997). Consequently, early treatment has been recommended (Schroder and Schroser, 1984; Thilander et al., 1984; Lindner et al., 1986; Vig and Vig, 1986; Mongini and Schmid, 1987; Lindner, 1989). The facial asymmetry describing the shifted position of mandible shows the strongest correlation with condyle path asymmetry (Pirttiniemi et al., 1990; Fukui et al., 1992; Mimura and Deguchi, 1994). Furthermore, the degree of asymmetry was found to be twice as great in the untreated as in the treated groups, emphasizing the importance of early treatment of posterior crossbite (Pirttiniemi et al., 1990). As functional corrector appliances in Class II cases and orthopedic forces in Class III malocclusions produce orthopedic effects on the TMJ experimentally (McNamara and Carlson, 1979; McNamara et al., 1982) and clinically (Mimura and Deguchi, 1996), a functional shift of the mandible in children resulting in a asymmetric position of condyle suggests that this functional shift may transmit forces to the skeleton resulting in asymmetry in the adult (Myers et al., 1980).
Although asymmetrical skeletal Class III adults are commonly treated by ortho-surgical procedures (Sugawara, 1996), asymmetry of TMJ morphology in group 3 in the present study may have effects on the stability of the treatment results. Interestingly, there are only a few reports in the literature, which describe the relationship between mandibular asymmetry and asymmetry (plagiocephaly) of the cranial vault (Kushima, 1979; Yoshikawa et al., 1986; Satoh et al., 1994). However, these findings suggest that plagiocephaly is a factor in the etiology of posterior crossbite.
Asymmetry of the mandible shows a high incidence of TMJ disorders (Sato et al., 1993), these being especially observed on the shifted side of mandible (Fushima et al., 1989). In those cases where the head of condyle is located at a posterior site, the articular disc is anteriorly dislocated and symptoms (e.g. sound) of TMJ disorders are induced at anterior guidance (Bandou et al., 1993). In this study, the position of the condyle on the shift side is located posteriorly which may induce anterior dislocation of the articular disc, causing a clicking.
Conclusions
|
* Present address: International Centre of Excellence in Dentistry, Eastman Dental Institute for Oral Health Care Sciences, University College London, 123 Gray's Inn Road, London WC1X 8TZ, UK 
References
Aoshima, O., Yamashita, T., Imamura, R. and Uehara, S. (1992) Morphological examination of condyle with basilar view cephalogram of true Class III and crossbite requiring surgical orthodontics treatment, Nihon University Journal of Oral Science, 18, 274–279.
Asai, Y. (1973) Growth changes of maxillofacial skeleton of Japanese from 12 to 20 years of age. A longitudinal study by means of cephalomeric roentogenograms, Journal of the Japanese Orthodontic Society, 32, 61–98.
Bandoh, E., et al. (1993)Color Atlas of Temporomandibular Disorders—New system of Diagnosis and Therapy,Ishiyaku Publishers Inc., Tokyo, Japan.
Erickson, G. E. and Waite, D. E. (1974) Mandibular asymmetry, Journal of the American Dental Association, 89, 1369–1373.[Medline]
Fukui, T., Satoh, Y., Tamada, K., Morita, S. and Hanada, K. (1992) Relationships between mandibular lateral deviation and bilateral condylar paths on mandibula protrusive movement, Journal of the Japanese Orthodontic Society, 51, 203–209.
Fushima, K., Akimoto, S., Takamoto, K., Sato, S. and Suzuki, Y. (1989) Morphological feature and incidence of TMJ disorders in mandibular lateral displacement cases, Journal of the Japanese Orthodontic Society, 48, 322–328.
Hayasaka, M., Takahashi, K., Kataoka, Y. and Tajima, T. (1983) A study of condylar position with sectograph. Part 1. Condylar position with reference to the various mandibular positions, Journal of the Japan Prosthodontic Society, 27, 550–572.
Hesse, K., Artun, J., Joondeph, D. R. and Kennedy, D. B. (1997) Changes in condyle position and occlusion associated with maxillary expansion for correction of functional unilateral posterior crossbite, American Journal of Orthodontics Dentofacial Orthopedics, 111, 410–418.
Houston, W. J. (1983) The analysis of errors in orthodontic measurements, American Journal of Orthodontics, 83, 382–390.[Medline]
Ishii, K. (1992) A histological study on the maxillary change to lateral deviation of the mandible and morphologic recovery after renovation of it, Journal of the Japanese Orthodontic Society, 51, 109–125.
Kobayashi, M., Saito, I., Ishii, K., Takeyama, M., Morita, S. and Hanada, K. (1996) Long-term observation of mandibular protrusion cases worsen in pubertal growth spurt, Journal of the Japanese Orthodontic Society, 55, 234–245.
Kushima, F. (1979) The relationships between the horizontal cranial contour and the position or form of the maxillary dental and basal arches-A study by means of roentogenocephalograms in vertico-basillar direction, Ohsaka Dai Shi Shi, 24, 211–236.
Lam, P. H., Sadowsky, C. and Omerza, F. (1999) Mandibular asymmetry and condylar position in children with unilateral posterior crossbite, American Journal of Orthodontics Dentofacial Orthopedics, 115, 569–575.
Lindner, A., Henrickson, C. O., Odenrick, L. and Modeer, T. (1986) Maxillary expansion of unilateral crossbite in preschool children, Scandinavian Journal of Dental Research, 94, 411–418.[Medline]
Lindner, A. (1989) Longitudinal study on the effect of early interceptive treatment in 4-year old children with unilateral crossbite, Scandinavian Journal of Dental Research, 97, 432–438.[Medline]
Marmary, Y., Zilberman, Y. and Mirsky, Y. (1979) Use of foramina spinosa to determine skull midlines, Angle Orthodontist, 49, 263–268.[Medline]
McNamara, J. A. and Carlson, D. S. (1979) Quantitative analysis of temporomandibular joint adaptations to protrusive function, American Journal of Orthodontics, 76, 593–611.[Medline]
McNamara, J. A., Hinton, R. J. and Hoffman, D. L. (1982) Histologic analysis of temporomandibular joint adaptation to protrusive function in young adult rhesus monkeys, American Journal of Orthodontics, 82, 288–298.[Medline]
Mimura, H. and Deguchi, T. (1994) Relationship between sagittal condylar path and the degree of mandibular asymmetry in unilateral cross-bite patients, Journal of Craniomandibular Practice, 12, 161–166.[Medline]
Mimura, H. and Deguchi, T. (1996) Morphologic adaptation of temporomandibular joint after chincup therapy, American Journal of Orthodontics Dentofacial Orthopedics, 110, 541–546.
Mongini, F. and Schmid, W. (1987) Treatment of mandibular asymmetries during growth. A longitudinal study, European Journal of Orthodontics, 9, 51–67.
Myers, D. R., Barenie, J. T., Bell, R. A. and Williamson, E. H. (1980) Condylar position in children with functional posterior crossbites: before and after crossbite correction, Pediatric Dentistry, 2, 190–194.[Medline]
Ogawa, Y. (1991) Investigation of the relationship between the inclination of the condylar head and maxillofacial morphology, Journal of Fukuoka Dental College, 18, 137–153.
Ogawa, Y., Yoshikawa, Y., Maruyama, K., Nichimoto, M., Kato, Y. and Deguchi, T. (1988) Application of subtraction to T.M.J. Cephalometric laminagraph, Journal of the Japanese Stomatological Society, 37, 81–88.
Pirttiniemi, P., Kantomaa, T. and Lahtela, P. (1990) Relationship between craniofacial and condyle path asymmetry in unilateral cross-bite patients, European Journal of Orthodontics, 12, 408–413.
Pullinger, A., Thurston, M. and Turley, P. (1985)Condylar adaptation to unilateral posterior crossbite in adults,Journal of Dental Research, 64, 269, Abstract 851.
Sakuda, M., Nakago, T., Matsumoto, M., Katayama, T., Yoshida, K. and Ishizawa, M. (1969) A case of posterior cross-bite: changes in form and function following orthodontic treatment, Journal of the Japanese Orthodontic Society, 28, 329–343.
Sato, S., Kawamura, H., Nagasaka, H., Goto, S., Motegi, K., Sugawara, J., Mitani, H. (1993) Incidence of temporomandibular joint disorders in patients with orofacial deformities, Journal of Japanese Society for Temporomandibular Joint, 5, 8–16.
Satoh, Y., Fukui, T., Hara, S., Yamada, K., Morita, S., Hanada, K. (1993) Relationship among mandibular deviation, condylar morphology and condylar movement, Journal of Japanese Society for Temporomandibular Joint, 5, 58–68.
Satoh, Y., Matsugishi, K., Fukui, T., Yamada, K., Morita, S. and Hanada, K. (1994) Relationship between mandibular lateral deviation and morphology of the cranial vault, Japanese Journal of Jaw Deformities, 4, 96–103.
Schroder, U. and Schroser, I. (1984) Early treatment of unilateral posterior crossbite in children with bilaterally contracted maxillae, European Journal of Orthodontics, 6, 65–69.
Sugawara, J. (1996)Surgical orthodontic treatment for facial asymmetry,Journal of Orthodontic Practice, Dec., 11–28.
Thilander, B., Wahllund and Lennartsson, B. (1984) The effects of early interceptive treatment in children with posterior crossbite, European Journal of Orthodontics, 6, 25–34.
Vig, P. S. and Vig, K. W. L. (1986) Hybrid appliances: a component approach to dentofacial orthopedics, American Journal of Orthodontics, 90, 273–285.
Walther, D. P. (1967)Orthodontic Notes,John Wright & Sons Ltd. Bristol.
Widman, D. J. (1988) Functional and morphologic considerations of the articular eminence, Angle Orthodontist, 58, 221–236.[Medline]
Yamaki, M., Mohri, T., Terada, K., Hanada, K., Nishi, K., Iwakata, S., Saitou, A. and Ishioka, K. (1990) The relationship between mandibular movement and dentofacial morphology: a preliminary report, Journal of Japanese Society for Temporomandibular Joint, 2, 22–33.
Yoshikawa, Y., Takagi, S., Kato, Y., Deguchi, T. (1986)The outline of skulls with unilateral posterior cross bite,Matsumoto Shigaku, 12, 145–149.
This article has been cited by other articles:
|
|
 |
|
  B. Buranastidporn, M. Hisano, and K. Soma Temporomandibular joint internal derangement in mandibular asymmetry. What is the relationship? Eur J Orthod, February 1, 2006; 28(1): 83 - 88. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
