Skip Navigation


The European Journal of Orthodontics Advance Access originally published online on September 5, 2006
The European Journal of Orthodontics 2007 29(1):21-25; doi:10.1093/ejo/cjl036
This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
29/1/21    most recent
cjl036v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Sato, M.
Right arrow Articles by Shimizu, N.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Sato, M.
Right arrow Articles by Shimizu, N.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© The Author 2006. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oxfordjournals.org.

Inclination of the occlusal plane is associated with the direction of the masticatory movement path

Motonori Sato*, Mitsuru Motoyoshi*,**, Masayuki Hirabayashi***, Kouhei Hosoi*, Narihiro Mitsui* and Noriyoshi Shimizu*,**

* Department of Orthodontics
** Division of Clinical Research, Nihon University School of Dentistry
*** Private Office, Tokyo, Japan

Address for correspondence Motonori Sato, Department of Orthodontics, Nihon University School of Dentistry, 1-8-13, Kanda Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan. E-mail: sato-mt{at}dent.nihon-u.ac.jp


   Summary
Top
 Summary
Introduction
 Subjects and methods
 Results
 Discussion
 Conclusions
 References
 
Using lateral cephalograms and a jaw movement-recording system, the relationship between the masticatory movement path and dentofacial morphology was investigated in 17 subjects (9 males and 8 females, mean age 23.5 years) without a history of orthodontic treatment. The masticatory movement path was measured at the right and left lower first molar while the subjects chewed gum. The angle between the Frankfort horizontal plane and the masticatory axis (FH-masticatory angle), defined as the axis passing the opening and closing turning point on the sagittal masticatory path, was also measured. The correlation between the angular measurements derived from the lateral cephalogram and the FH-masticatory angle was then investigated.

A positive correlation was observed in the FH-masticatory, occlusal plane (P < 0.05), and mandibular plane (P < 0.01) angles. Furthermore, it was found that the angle between the masticatory axis and the occlusal plane (69.1 ± 4.2 degrees) remained constant even as the masticatory axis showed a tendency to incline forward as the mandibular plane angle became steeper; the rates of change of the FH-masticatory and the occlusal plane angles were approximately 1:1. This finding suggests that the masticatory movement path is closely associated with the occlusal plane.


   Introduction
Top
 Summary
 Introduction
Subjects and methods
 Results
 Discussion
 Conclusions
 References
 
Clinical studies have indicated that functions of the body are mutually related to dentofacial morphology (Harvold, 1963Go; Moss and Salentijin, 1969Go) and that the maxilla, mandible, teeth, temporomandibular joints (TMJs), and masticatory muscles correspond to stomatognathic function (Moss, 1981Go). Occlusal interdigitation that does not complement function in this setting after orthodontic treatment may result in relapse and/or the onset of stomatognathic dysfunction.

Masticatory movement, a stomatognathic function, complements the functions of the mandible, tongue, and face in relation to the central nervous system (Lund, 1991Go; Nakamura and Katakura, 1995Go). The masticatory function regulatory mechanism modulates rhythmic jaw movements via sensory feedback from mechanoreceptors in the periodontal tissues regarding the masticatory force and the direction of force loaded onto the teeth (Appenteng et al., 1982Go; Ramfjord and Ash, 1983Go; Lavigne et al., 1987Go; Inoue et al., 1989Go; Yamamura and Shimada, 1993Go).

Sassouni (1969)Go reported a tendency that if the mandibular plane angle is smaller, bite force is larger, and conversely, if the mandibular plane angle is larger, bite force is smaller. These findings show a part of relationship between dentofacial morphology and stomatognathic function. However, it is important to consider not only force strength, but also the direction of the force.

Although, it is thought that the masseter muscle is especially related to the factor in which the direction of masticatory movement is decided, other masticatory and facial muscles also affect the direction of masticatory movement. Therefore, this study investigated the masticatory movement path generated with harmonized movement of the muscles. The aim was to verify a hypothesis that some relationships are observed between maxillofacial morphology and the masticatory movement path.


   Subjects and methods
Top
 Summary
 Introduction
 Subjects and methods
Results
 Discussion
 Conclusions
 References
 

Subjects

Seventeen healthy adults (9 males and 8 females, mean age 23.5 years) who had no restorations covering the cusp tips, no TMJ symptoms, and no history of orthodontic treatment were examined. The aim of the study was explained to the subjects, who all provided their informed consent to participate. The study was approved by the ethics committee of Nihon University School of Dentistry (number 2003-19).


Measurement of mandibular movement

Masticatory movement was recorded using the Gnathohexagraph (JM-1000H, Ono Sokki Manufacturing Co., Ltd, Yokohama, Japan). The installation and recording methods were performed following the guidelines of Miyawaki et al. (2000)Go. The accuracy of the Gnathohexagraph has previously been demonstrated (Tokiwa et al., 1996Go; Tokiwa, 2001Go).

The subjects were seated on chairs, with their heads in a fixed position. The co-ordinates of the right and left upper margins of the tragus and orbital, as well as those of the mesio-buccal cusp tips of the lower first molar, were recorded using the LED pointer of the gnathohexagraph. Chewing gum (Freezone, Lotte Co., Ltd, Tokyo, Japan) was used for the measurement of masticatory movement. Before measurement, the subjects chewed the gum for 1 minute to soften it, and centric occlusion was then fixed as the starting position for masticatory movement recording. The subjects chewed 15 times on both the right and left sides of their mouths, and the masticatory path of the lower first molar on the working side was recorded. These measurements were obtained by one author (MS).


Definition of the masticatory axis

The sagittal movement path was evaluated to compare the recorded masticatory path with measurements from the lateral cephalograms (Figure 1A). The masticatory axis was defined as the axis passing the opening and closing turning point on the sagittal masticatory path (Figure 1B). The average masticatory axis during 15 cycles and the FH plane were measured. The mean values of the right and left angles were then calculated and compared with the cephalometric measurements (Figure 2).


Figure 1
View larger version (30K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 1 The masticatory path of the lower first molar (A). Definition of the masticatory axis (B).

 

Figure 2
View larger version (16K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 2 Definition of the masticatory axis. FH-masticatory angle (a), FH-Occ (b), the angle of the masticatory axis to the occlusal plane (c).

 

Morphometry

The angles between the FH plane and the occlusal (FH-Occ), mandibular (FH-Mand), and SN (FH-SN) planes, as well as SNA, SNB, and ANB, were measured (Figure 3). One examiner (MS) traced and measured all the radiographs to eliminate interexaminer errors. All the tracings and measurements were performed at least twice with an interval of 1 month to reduce intraexaminer errors, and the mean values were used. When there was more than a 1-degree difference in the measurements, the tracing was remeasured and the mean value of the three measurements was used.


Figure 3
View larger version (17K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 3 Cephalometric measurements—1, FH-Occ; 2, FH-SN; 3, FH-Mand; 4, ANB; 5, SNA; and 6, SNB.

 

Statistical analysis

Pearson's correlation coefficient between the FH-masticatory angle and the cephalometric measurements was calculated. FH-Occ was designated as an independent variable in order to examine the relationship between the FH-masticatory angle and the occlusal plane, and regression analysis was used for the FH-masticatory angle. The statistical analyses were performed using SPSS for Windows version 8.0J (SPSS Inc., Tokyo, Japan).


   Results
Top
 Summary
 Introduction
 Subjects and methods
 Results
Discussion
 Conclusions
 References
 
Table 1 shows the descriptive statistics for the FH-masticatory angle and the cephalometric measurements. The ANB ranged from –1.5 to 7.0 degrees and the Frankfort mandibular plane angle from 14.5 to 36.0 degrees. Thus, the study included subjects with various skeletal abnormalities.


View this table:
[in this window]
[in a new window]

  		Table 1 Means and standard deviations (SDs) of the FH-masticatory angle and cephalometric measurements (degrees).

 
The correlation coefficient between the FH-masticatory angle and the cephalometric measurements is shown in Table 2. The FH-masticatory angle demonstrated significant correlation with FH-Occ and FH-Mand. The data indicated that as the FH-masticatory angle increased, FH-Occ and FH-Mand also increased; however, no other significant correlation was observed.


View this table:
[in this window]
[in a new window]

  		Table 2 Pearson's correlation coefficient between the FH-masticatory angle and cephalometric measurements.

 
A correlation of the FH-masticatory angle and FH-Occ is shown in Figure 4. The regression coefficient was 0.97, indicating an almost 1:1 ratio for the rates of change of the FH-masticatory angle and FH-Occ. Therefore, the angle between the FH-masticatory axis and the occlusal plane appeared to be constant.


Figure 4
View larger version (8K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 4 The relationship between the inclination of the occlusal plane and the masticatory axis.

 

   Discussion
Top
 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
Conclusions
 References
 
The gnathohexagraph has a small facebow, and the burden on the patient is reduced compared with previous jaw movement-recording systems. In addition, it can record arbitrary points, which are useful in the study of the masticatory movement path (Hannnam, 1991Go; Tokiwa et al., 1996Go; Palla et al., 1997Go; Huddleston Slater et al., 1999Go; Miyawaki et al., 2000Go; Tokiwa, 2001Go).

Previous masticatory movement investigations have attempted to clarify the masticatory mechanism (Ottenhoff et al., 1993Go; Slagter et al., 1993Go; Daet et al., 1995Go; Miyawaki et al., 2000Go; Beata et al., 2003Go; Hayasaki et al., 2003Go; Naeije and Hofman, 2003Go); however, these studies largely focused on incisor and condylar points, despite the fact that food crushing and tearing occur on the masticatory surfaces of the molars. Movement of the lower central incisor point differs from that of the lower first molar during mastication (Gibbs et al., 1981Go; Gibbs and Lundeen, 1982Go). Stresses and strains can be observed on the masticatory surface of the first molar during the terminal occlusal phase and can affect maxillo-mandibular formation (Korioth, 1990Go). For these reasons, the masticatory path of the first molar was recorded.

The sagittal masticatory path of the first molar, which is considered a simple parameter for masticatory functions, was compared with cephalometric measurements. The present study defined the masticatory axis as that passing the opening and closing turning point on the sagittal masticatory path. The superior turning point of closing to opening is the intercuspal position (i.e. centric occlusion; Hayasaki et al., 2003Go) and is thought to be stable in adults without abnormal TMJs or malocclusion. The inferior turning point is affected by the anatomical morphology of the TMJ (Yatabe et al., 1995, 1997GoGo; Naeije, 2003Go), the solidity and size of the food bolus (Bilt et al., 1991Go; Miyawaki et al., 2000Go), and the muscle reflective activity, strength, and operation. The inclination of the masticatory axis is alternated according to the location of the inferior turning point. Prior to measurement, the chewing gum used in the study was chewed for 1 minute to soften it in order to eliminate recording errors due to inconsistency in texture.

The results demonstrated a positive correlation in the inclination between the masticatory axis and the mandibular plane when measured relative to the FH plane (Table 2). As the angle between the FH plane and the masticatory axis increased, the angle of the FH plane and the mandibular plane also increased. The masticatory axis inclined forward in the subjects with a high angle (i.e. dolichofacial type). A positive correlation was also shown in the inclination between the masticatory axis and the occlusal plane (Table 2). When a larger masticatory angle was observed, a larger occlusal plane angle was also found; accordingly, when the occlusal plane was steep, the masticatory axis inclined forward.

The regression coefficient was 0.97, which indicates a 1:1 ratio for the rate of change in the inclination of the masticatory axis and occlusal plane. The angle between the masticatory axis and occlusal plane remained constant (approximately 69 degrees), regardless of the inter-skeletal variation among the subjects. The masticatory axis and the occlusal plane showed a tendency to incline forward with a high angle, thus maintaining a constant angle.

Sassouni and Nanda (1964), Proctor and DeVincezon (1970)GoGo, and DiPietro and Moergeli (1976)Go investigated the relationship between the masseter muscle and the occlusal plane and reported that the occlusal plane becomes steeper and the masseter muscle inclines forward as the mandibular plane becomes steeper. Proctor and DeVincezon (1970)Go showed that the angle between the anterior border of the masseter muscle and the occlusal plane remained at approximately 69 degrees—a value similar to that of the angle of the masticatory axis and the occlusal plane in the present study, suggesting that one of the factors determining the inclination of the masticatory axis is related to conditions such as muscle activity and the operation of the anterior border of the masseter muscle.

Ogawa et al. (1998b)Go reported a correlation between the occlusal plane and the masticatory path of closure, in which the masticatory closing path and the occlusal plane maintained a consistent perpendicular relationship with each other regardless of the interindividual variation in occlusal plane inclination. Notably, Ogawa et al. (1998a)Go recorded masticatory movement using the incisor point, which resulted in differences between their findings and those of the present study. However, the results of both investigations confirm that there is a constant relationship in sagittal inclination between masticatory movement and the occlusal plane.


   Conclusions
Top
 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
 Conclusions
References
 
The present study replaced complex masticatory movement with the masticatory axis as a simple parameter of masticatory function. The results suggest that the masticatory axis is significantly correlated with the occlusal plane, involving agreement between stomatognathic function and dentofacial morphology during growth and development. Occlusal alteration caused by orthodontic treatment can be a factor in relapse and disharmony between functional movement and dentofacial morphology.


   Acknowledgement
 
This study was supported by a grant from the Ministry of Education, Culture, Sports, Science, and Technology.


   References
Top
 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
 Conclusions
 References
 

    Appenteng K, Lund JP, Seguin JJ. (1982) Intraoral mechanoreceptor activity during jaw movement in the anesthetized rabbit. Journal of Neurophysiology 48:27–37.[Free Full Text]

    Beata D, Andrzej M, Maciej R. (2003) Finite element analysis of stress in molars during clenching and mastication. Journal of Prosthetic Dentistry 90:591–597.[CrossRef][ISI][Medline]

    Bilt A, Glas HW, Olthoff LW, Bosman F. (1991) The effect of particle size reduction on the jaw gape in human mastication. Journal of Dental Research 70:931–937.[Abstract/Free Full Text]

    Daet DG, Watanabe M, Sasaki K. (1995) Association between the interarch distance and food bolus size in the early phase of mastication. Journal of Prosthetic Dentistry 74:367–372.[CrossRef][ISI][Medline]

    DiPietro GJ and Moergeli JR. (1976) Significance of the Frankfort-mandibular plane angle to prosthodontics. Journal of Prosthetic Dentistry 36:624–635.[CrossRef][ISI][Medline]

    Jaw movements and forces during chewing and swallowing and their clinical significance. In Gibbs CH and Lundeen HC (Eds.). Advances on occlusion (1982) , Wright, Boston pp. 2–32.

    Gibbs CH, Lundeen HC, Mahan PE, Fujimoto J. (1981) Chewing movements in relation to border movements at the first molar. Journal of Prosthetic Dentistry 46:308–322.[CrossRef][ISI][Medline]

    Hannnam AG. (1991) The measurement of jaw motion. In McNeill C (Ed.). Current controversies in temporomandibular disorders(Quintessence Publishing Co., Chicago) pp. 130–137.

    Harvold EP. (1963) Some biologic aspects of orthodontic treatment in the transitional dentition. American Journal of Orthodontics 49:1–14.[Medline]

    Hayasaki H, Saitoh I, Throckmorton GS, Iwase Y, Nakata S, Nakata M. (2003) Occlusal phase of gum-chewing strokes. Journal of Oral Rehabilitation 30:1041–1046.[CrossRef][ISI][Medline]

    Huddleston Slater JJ, Visscher CM, Lobbezoo F, Naeije M. (1999) The intra-articular distance within the TMJ during free and loaded closing movements. Journal of Dental Research 78:1815–1820.[Abstract/Free Full Text]

    Inoue T, Kato T, Masuda Y, Nakamura T, Kawamura Y, Morimoto T. (1989) Modifications of masticatory behavior after trigeminal deafferentation in the rabbit. Experimental Brain Research 74:579–591.[ISI][Medline]

    Korioth B. (1990) Number and location of occlusal contacts in intercuspal position. Journal of Prosthetic Dentistry 64:206–210.[CrossRef][ISI][Medline]

    Lavigne G, Kim JS, Valiquette C, Lund JP. (1987) Evidence that periodontal pressoreceptors provide positive feedback to jaw closing muscles during mastication. Journal of Neurophysiology 58:342–358.[Abstract/Free Full Text]

    Lund JP. (1991) Mastication and its control by the brain stem. Critical Reviews in Oral Biology and Medicine 2:33–64.

    Miyawaki S, Ohkochi N, Kawakami T, Sugimura M. (2000) Effect of food size on the movement of the mandibular first molars and condyles during deliberate unilateral mastication in humans. Journal of Dental Research 79:1525–1531.[Abstract/Free Full Text]

    Moss ML. (1981) Genetics, epigenetics, and causation. American Journal of Orthodontics 80:366–375.[CrossRef][ISI][Medline]

    Moss ML and Salentijin L. (1969) The primary role of functional matrices in facial growth. American Journal of Orthodontics 55:566–577.[CrossRef][ISI][Medline]

    Naeije M. (2003) Measurement of condylar motion: a plea for the use or the condylar kinematic center. Journal of Oral Rehabilitation 30:225–230.[CrossRef][ISI][Medline]

    Naeije M and Hofman N. (2003) Biomechanics of the human temporomandibular joint during chewing. Journal of Dental Research 82:528–531.[Abstract/Free Full Text]

    Nakamura Y and Katakura N. (1995) Generation of masticatory rhythm in the brainstem. Neuroscience Research 23:1–19.[CrossRef][ISI][Medline]

    Ogawa T, Koyano K, Suetsugu T. (1998a) Correlation between inclination of occlusal plane and masticatory movement. Journal of Dentistry 26:105–112.[CrossRef][ISI][Medline]

    Ogawa T, Koyano K, Umemoto G. (1998b) Inclination of the occlusal plane and occlusal guidance as contributing factors in mastication. Journal of Dentistry 26:641–647.[CrossRef][ISI][Medline]

    Ottenhoff FA, Bilt A, Glas HW, Bosman F. (1993) Control of human jaw elevator muscle activity during simulated chewing with varying bolus size. Experimental Brain Research 96:501–512.[ISI][Medline]

    Palla S, Krebs M, Gallo LM. (1997) Jaw tracking and temporomandibular joint animation. In McNeill C (Ed.). Science and practice of occlusion(Quintessence Publishing Co., Chicago) pp. 365–378.

    Proctor AD and DeVincezon JP. (1970) Masseter muscle position relative to dentofacial form. The Angle Orthodontist 40:37–44.[ISI][Medline]

    Neural and structural basis of motor behavior. In Ramfjord S and Ash MM (Eds.). Occlusion (1983) (W B Saunders, Philadelphia) pp. 71–127.

    Sassouni V. (1969) A classification of skeletal facial type. American Journal of Orthodontics 55:109–123.[CrossRef][ISI][Medline]

    Sassouni V and Nanda S. (1964) Analysis of dentofacial vertical proportions. American Journal of Orthodontics 50:801–823.[CrossRef][ISI]

    Slagter AP, Bosman F, Glas HW, Bilt A. (1993) Human jaw-elevator muscle activity and food comminution in the dentate and edentulous state. Archives of Oral Biology 38:195–205.[CrossRef][ISI][Medline]

    Tokiwa H. (2001) Evaluation of the clinical accuracy of an optical recording system for mandibular movement. Journal of Japanese Society of Stomatognathic Function 7:13–25.

    Tokiwa H, Miura F, Kuwahara Y, Wakimoto Y, Twuruta M. (1996) Development of a new analyzing system for stomatognathic functions. Journal of Japanese Society of Stomatognathic Function 3:11–24.

    Yamamura C and Shimada K. (1993) Differential controls of small and large motor unit activity in the masseter muscle with incisal stimulation in humans. Brain Research 632:339–341.[CrossRef][ISI][Medline]

    Yatabe M, Zwijnenburg A, Megens CC, Naeije M. (1995) The kinematic center: a reference for condylar movements. Journal of Dental Research 74:1644–1648.[Abstract/Free Full Text]

    Yatabe M, Zwijnenburg A, Megens CC, Naeije M. (1997) Movements of the mandibular condyle kinematic center during jaw opening and closing. Journal of Dental Research 76:714–719.[Abstract/Free Full Text]


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?



This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
29/1/21    most recent
cjl036v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Sato, M.
Right arrow Articles by Shimizu, N.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Sato, M.
Right arrow Articles by Shimizu, N.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?