J Oral Maxillofac
Surg
46:690-696.1990
Condylar Position in Superior Maxillary Repositioning and Its Effect on the Temporomandibular Joint EUGENIO G. HERBOSA, DMD, MMSc,* KENNETH S. ROTSKOFF, BERNARD F. RAMOS, MD,+ AND HENRYS. AMBROOKIAN,
DDS, MD,t DDS§
Twenty-nine patients (58 joints) were tomographically evaluated for condylar position and assessed for temporomandibular joint function following superior maxillary repositioning with mandibular autorotation. Seventy-six percent of the condyles showed postoperative posterior repositioning, whereas tomographic measurement of the joint spaces revealed significant posterior condylar position (P < .Ol) relative to the preoperative position. Pre- and postoperative comparative values of condylar displacement from absolute concentricity based on the Pullinger index also showed posterior condylar repositioning postoperatively (P -C ,001). However, there was no correlation between condylar position and the presence of temporomandibular joint symptoms in both the asymptomatic and symptomatic groups.
clicking and popping after the release of maxillomandibular fixation. All TMJ symptoms eventually resolved after a few months, and there was no evidence of myofascial pain or dysfunction (MPD) observed in any of their patients either pre- or postoperatively. On the other hand, in a recent study, Kahnberg reported that 60% of his 13 patients who underwent superior maxillary repositioning developed symptoms of painful TMJ clicking, decreased mandibular range of motion, and MPD.’ Many clinicians have associated myalgia, arthralgia, internal derangement, and arthrosis with nonconcentric condylar position in the glenoid fossa.&13 However, Markovic and Rosenberg, in their tomographic evaluation of 100 patients, showed that 86% of their symptomatic patients had concentric condyles.t4 Likewise, Katzberg et al arthrographitally demonstrated no statistical difference in condylar position between asymptomatic and symptomatic patients. I5 A number of investigators also have claimed that posteriorly positioned condyles are a precursor to anterior disc dislocation/displacementgY” and consequent development of TMJ and myofascial pain and dysfunction.‘1~‘3716,17However, other studies have shown a wide variation of condylar position in selected
Superior repositioning of the maxilla with mandibular autorotation is widely advocated as a surgical treatment for the correction of vertical maxillary hyperplasia with or without anterior apertognathia. l-3 The significance of the postoperative condylar position in relation to postoperative temporomandibular joint (TMJ) function is, however, controversial. O’Ryan and Epker,4 in a retrospective study of 10 randomly selected patients showed 60% of their patients to have posteriorly positioned condyles after treatment, but they claimed that only 15% of the joints exhibited immediate postoperative * Fellow, Oral and Maxillofacial Surgery, St Mary’s Health Center and Dentofacial Deformities and Orofacial Pain Center, St Louis, MO. t Program Director, Oral and Maxillofacial Surgery, St Mary’s Health Center and Dentofacial Deformities and Orofacial Pain Center, St Louis, MO. $ Research Fellow, Washington University School of Medicine, St Louis, MO. 8 In private practice, Milwaukee, WI. Address correspondence and reprint requests to Dr Herbosa: Orofacial Pain Center, 1031 Bellevue, Suite 310, St Louis, MO 63117. 0 1990 geons
American
Association
of Oral
and
Maxillofacial
Sur-
0278-2391/90/4807-0005$3.00/0
690
691
HERBOSAETAL asymptomatic18~” and symptomatic populations,22 thereby questioning the diagnosis of internal derangement based solely on a tomographically determined condylar position. Most recently, it has been shown that there was high statistical variability and unpredictability of condylar position as it relates to TMJ disorders in both asymptomatic and symptomatic groups.22-24 This further implies that there is insufficient evidence to support the contention that a nonconcentric condyle-fossa relationship predisposes to TMJ disorders. The purpose of this study was to compare and quantify the pre- and postoperative changes in condylar position following superior repositioning of the maxilla and to clinically evaluate its effect on the TMJ. Likewise, this study compared the changes in condylar position in patients with or without temporomandibular joint symptoms. Materials and Methods The study was based on 29 patients (58 joints), 19 females and 10 males, with a mean age of 20.2 years (range, 16 to 33 years). All were diagnosed as having vertical maxillary hyperplasia, with 20 of the patients exhibiting anterior apertognathia. All patients were treated orthodontically and underwent superior repositioning of the maxilla via a one-piece (13 patients) or segmental (16 patients) Le Fort I osteotomy. The range of impaction was from 3 to 7 mm. Semirigid (Steinman pins) or rigid fixation (bone plates) was used to stabilize the maxilla in its predetermined postoperative position. Maxillomandibular fixation was maintained from 5 days to 4 weeks depending on the type of fixation. The interocclusal splint remained for at least 3 weeks (one-piece cases) or up to 10 to 12 weeks for segmental cases requiring transverse expansion.
RADIOGRAPHICASSESSMENTOF CONDYLAR POSITION Preoperative and postoperative condylar positions were evaluated from left and right cephalometric linear full-head tomograms (QuintSectograph, Los Angeles, CA). These were corrected for axial rotation based on a submentovertex radiograph as described by Beckwith et a1.2s Preoperatively, the views were obtained with the mandible in centric occlusion using Coprwax bite wafers (Surgident, Columbus Dental Co, St Louis, MO) to stabilize the occlusion and to minimize the
likelihood of the patient’s slipping into an acquired centric occlusion. The same interocclusal wafer was used to orient the mandibular cast to the maxillary cast for purposes of model surgery. The casts were mounted on a semiadjustable articulator (Denar Mark-4, Anaheim, CA) with the maxillary cast oriented using a facebow transfer. Three to five days after surgery, postoperative tomograms were taken, with the occlusion stable in the interocclusal splint. DETERMINATIONOF JOINT SPACES AND CONDYLARDISPLACEMENT All pre- and postoperative left and right full-head tomograms were independently traced, joint spaces measured to the nearest tenth of a millimeter, and evaluated for condylar position by three different individuals (Fig 1). The Frankfort horizontal (porion to orbitale), mandibular condyle, and glenoid fossa landmarks were traced on an 8 x 10 inch 0.003 cephalometric acetate paper. Perpendicular lines were then drawn tangential to the anterior and posterior surfaces of the mandibular neck (a and b). A parallel line to FH was drawn tangential to the superior surface of the condyle (c). The distance between a and b was then measured, and another line (d) was drawn parallel to line c using this dimension to form a perfect square. Two diagonal lines were then drawn intersecting each other and extending to the fossa outline. The intersection was interpreted as the center of the condyle.26 Another vertical line (e), parallel to lines a and b, was drawn across the center of the condyle to the fossa outline. The three lines formed in the intra-articular spaces were designated as anterior (A), superior (S), and posterior (P) joint spaces (Fig 1). Preoperative and postoperative changes in condylar position were quantitatively defined as a decimal percentage of displacement from a position S
FIGURE 1. Determination of anterior (A), superior (s), and posterior (P)joint spaces based on Frankfort horizontal (FH) and geometric center of the condyle.
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EFFECT OF CONDYLAR POSITION ON TMJ FUNCTION
of absolute concentricity (0) in the fossa. These were based on an index modified from the Pullinger et al formula*‘: posterior posterior
- anterior joint space + anterior joint space
According to this index, complete posterior condylar displacement (no posterior joint space), would equal - 1, complete anterior condylar displacement (no anterior joint space) + 1, and absolute or perfect concentricity 0.27 To correlate the relationship of this index to the actual condylar displacement in millimeters, a change of 0.1 was considered approximately equal to a OS-mm to 0.6-mm difference in either the anterior or posterior direction (personal communication, Drs L. Johnston and A. Frost, St Louis University, Department of Orthodontics) .
CLINICALEVALUATION OF THE TEMPOROMANDIBULARJOINT
All patients were evaluated for internal derangement and myofascial pain and dysfunction pre- and postoperatively using the following criteria: range of mandibular opening (measured interincisally in millimeters) and lateral excursions (measured from facial midline in millimeters); presence of joint noises such as clicking, popping, or crepitation by auscultation; and myofascial pain and tenderness by palpation. TMJ function was further assessed using the same criteria 12 months after surgery (range, 6-18 months). Table 1. Tomographic Measurement (mm) of Anterior, Superior, and Posterior Joint Spaces Preoperative Left (29 joints) Anterior Superior Posterior* Right (29 joints) Anterior Superior Posterior* Left and right (58 joints) Anterior? Superior Posteriort
Postoperative
2.52 k 0.97 2.62 * 0.59 2.42 t 0.95
2.76 k 1.00 2.43 f 1.03 2.02 f 0.81
2.47 f 0.89 2.46 + 0.59 2.28 -f- 0.78
2.67 f 1.04 2.41 ” 0.64 1.99 ? 0.72
2.49 * 0.92 2.53 ? 0.85 2.35 2 0.86
2.72 2 1.02 2.41 k 0.85 2.00 f 0.76
Measurements are given as mean k SD. * Paired t test, P < .Ol. t Paired f test, P < .05.
Results
AND STATISTICALANALYSIS OF CONDYLAR POSITION
RADIOGRAPHIC
Table 1 shows the actual pre- and postoperative anterior, superior, and posterior joint space measurements. A tendency toward posterior condylar positioning was seen preoperatively, with further posterior repositioning postoperatively. When the right and left side values were combined, the difference was statistically significant at P < .Ol. The combined superior joint space values, although not significant, showed a tendency toward superior condylar repositioning after surgery. Table 2 shows the frequency of condylar position based on the actual anterior and posterior joint space measurements. Preoperatively, both left and right condyles showed a tendency to posterior positioning in about 52% of the joints. Postoperatively, further posterior condylar positioning was seen in 76% of the joints (left and right joints combined), with only 26% and 1.7% of the joints, respectively, exhibiting anterior and concentric positions. Table 3 shows the actual deviation in condylar displacement from absolute concentricity (0) as based on the Pullinger index. As mentioned previously, an anterior position is denoted by a positive ( +) value and a posterior position with a negative ( - ) value. The differences between ail pre- and postoperative values for the left and right sides alone or combined were statistically significant at P < .OOl. An approximate 0.5-mm to 0.6-mm postoperative condylar displacement, relative to the preoperative position, was seen. These findings Table 2. Frequency of Tomographic Condylar Position Based on Actual Joint Soace Measurements (%) Left (29 joints) Anterior Concentric Posterior Right (29 joints) Anterior Concentric Posterior Left and right (58 joints) Anterior Concentric Posterior
Preoperative
Postoperative
12/29 (41 .O%) 2/29 (6.9%) 15/29 (51.7%)
8129 (27.6%) l/29 (3.5%) 20/29 (69.0%)
12/29 (41 .O%) 2/29 (6.9%) 15/29 (51.7%)
7129 (24.0%) O/29 (0.0%) 22/29 (76.0%)
24/58 (41 .O%) 4/58 (6.9%) 30/58 (52.0%)
15/58 (26.0%) l/58 (1.7%) 42/58 (76.0%)
Numerator, no. of joints in respective position; denominator, total no. of joints.
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HERBOSA ET AL
Table 3. Comparative Pullinger Index* Values of Condylar Displacement From Absolute Concentricity (0)
Left (29 joints)t Right (29 joints)? Combined (58 joints)t
Preoperative
Postoperative
-0.02 2 0.26 -0.04 2 0.26 -0.03 + 0.26
-0.14 * 0.26 -0.13 2 0.29 -0.13 k 0.28
tistically significant (P < .05), with a change toward the posterior direction in both groups. This is reflected postoperatively in that 68.4% of females and 80% of males showed posterior repositioning of the condyle in the fossa.
TEMPOROMANDIBULAR Values are given as mean 2 SD. * Negative values = posterior condylar position from absolute concentricity (0); 0.1 change - 0.5 mm displacement. t Paired t test, P < .OOl.
correlated with the tomographic measurements described in Tables 1 and 2, confirming postoperative condylar repositioning (Fig 2). Table 4 shows the comparative values for females and males to clarify the differences in condylar position between these groups. Preoperatively, there was a tendency toward posterior condylar positioning in 52.6% of the female group and in 50% of the male population. Postoperatively, males showed a significantly greater tendency toward posterior repositioning than females. The 0.16 Pullinger index difference in the male group corresponded to approximately a 0.75mm posterior displacement in condylar position as compared with a .086 change (0.4 mm) in the female group. The difference in Pullinger indices pre- and postoperatively for both groups was statistically significant (P < .Ol). Likewise, the difference in anterior joint space values during the pre- and postoperative periods was sta-
JOINT EVALUATION
Preoperatively, 11 of 29 patients (37.9%) examined showed symptoms of internal derangement and myofascial pain and dysfunction. Table 5 summarizes the pre and 1Zmonth postoperative findings, showing a marked decrease in symptoms in 5 of the previously 11 symptomatic patients. There was a slight, although not statistically significant, decrease in the postoperative mandibular range of motion. The condylar position in asymptomatic and symptomatic patients was evaluated as shown in Table 6. Almost 56% of the asymptomatic group demonstrated posterior condylar positioning preoperatively compared with 45.5% in the symptomatic group. Further posterior repositioning was seen after surgery in both groups. Interestingly, the asymptomatic group demonstrated a greater degree of posterior repositioning than the symptomatic group. The differences, however, were not statistically significant. Pre- and postoperative Pullinger indices confirmed consistent posterior condylar position in both groups (Table 6).
FIGURE 2. A, Preoperative position. B, Representative condylar position after mandibular autorotation following superior maxillary repositioning, showing tendency to posterior condylar repositioning.
694
EFFECT OF CONDYLAR POSITION ON TMJ FUNCTION
Table 4. Comparative Joint Space Measurements (mm), Puiiinger index Values, and Frequency (%) of Condyiar Position in Female and Male Groups
No. of patients Total no. of joints Preoperative Anterior* Posterior Pullinger index Postoperative Anterior* Posterior Pullinger index
Female
Male
19 38
10 20
Asymptomatic
2.29 -+ 0.76 (31.6%) 2.89 * 1.09 (50%) 2.54 +- 1.00 (50%) 2.26 f 0.78 (52.6%) -0.004 2 0.24t -0.06 * 0.297 3.13 f 1.15 (20%) 2.50 f 0.89 (28.9%) 1.96 f 0.87 (80%) 2.02 k 0.70 (68.4%) -0.22 -+ 0.29t -0.09 k 0.26t
Values are given as mean f SD. Negative Pullinger index values = posterior condylar position from absolute concentricity (0); 0.1 change = 0.5 mm displacement. Frequency percentage is based on no. of joints in respective position/total no. of joints in each group. * Unpaired t test, P < .05. t Preoperative vs Postoperative paired t test, P < .Ol.
Discussion
There is paucity of information regarding condylar position and its effect on the temporomandibular joint after superior maxillary repositioning with mandibular autorotation. Recently, Kahnberg’ reported that 60% of his patients developed some form of TMJ disorder after undergoing this procedure. Despite the absence of radiographic evaluation of condylar position, he speculated that development of these symptoms was secondary to “squeezing of the disc.” This implies anterior condylar repositioning with disc displacement, contrary to our present study. Conversely, O’Ryan and Epker,4 in their retrospective study supported by Table 5. Summary of Frequency of Subjective and Clinical Manifestations of Temporomandibuiar Joint Function in the Symptomatic Group (%) Preoperative Symptomatic patients Range of motion (mm) Mandibular opening* Lateral excursions Joint noises Clicking Popping Crepitation TMJ-myofascial pain
Postoperative
1l/29 (37.9%)
6/29 (20.7%)
48.77 + 6.00 10.2-10.3
46.92 ” 8.20 9.4-9.8
8129 (27.6%) l/29 (3.5%) l/29 (3.5%) 8/29 (27.6%)
5/29 (17.2%) O/29 (0.0%) l/29 (3.5%) 2/29 (6.8%)
Numerator, no. of symptomatic patients; denominator, no. of patients. * Paired t test, P > .05. t Right-left mean lateral excursions.
Table 6. Comparative Joint Space Measurements (mm), Puiiinger Index Values, and Frequency (%) of Condylar Position in the Asymptomatic and Symptomatic Groups
total
Symptomatic
Preoperative No. of patients* 18/29 (62.1%) 1l/29 (37.9%) Condylar positiont Anterior* 2.72 2 0.94 (36.1%) 2.14 + 0.78 (45.5%) Posterior 2.38 f 0.88 (55.5%) 2.27 f 0.82 (45.5%) Pullinger index -0.07 k 0.26 -0.04 * 0.25 Postoperative No. of patients* 6129 (20.7%) 23129 (79.3%) Condylar positiont Anterior 2.79 k 1.00 (23.9%) 2.42 + 1.06 (50.0%) Posterior 2.00 k 0.84 (73.9%) 2.00 + 0.34 (41.7%) Pullinger index -0.16 2 0.27 -0.01 + 0.28 Values are given as mean 2 SD. Negative Pullinger index values = posterior condylar position from absolute concentricity (0); 0.1 change = 0.5 mm displacement. * Numerator, no. of patients in each group; denominator, total no. of patients. t Percentage based on no. of joints in respective position/total no. of joints. $ Unpaired t test, P < .05.
tomographic evaluation, showed that 60% of their patients had posteriorly positioned condyles. In addition, 15% of the joints that were symptomatic had reduction of TMJ and MPD symptoms after surgery, which was consistent with our findings. The effect of condylar position and the relationship to the development of TMJ disorders has remained controversial in the literature.8’10-15V22*27 Numerous investigators have associated abnormal joint function with “distalized” condylar position. 11*13*16,17 However, several studies have found no significant statistical difference in condylar position between asymptomatic and symptomatic Although 51.7% of our patients populations. 15*22v27 demonstrated a preoperative tendency to posterior condylar position, only 37.9% of the patients exhibited symptoms of TMJ and myofascial disorders. Postoperatively, 76% of the joints studied showed a significant posterior condylar repositioning, corresponding to approximately 0.5 mm to 0.6 mm of actual change as based on the Pullinger index. In spite of these changes, we observed a reduction in the number of symptomatic patients (20.7%). In addition, there was no significant difference in the measured condylar position between the asymptomatic and symptomatic patients either pre- or postoperatively. More significantly, the asymptomatic group demonstrated more posterior condylar displacement than the symptomatic group in the postoperative period. These findings suggest that
695
HERBOSAETAL
during a 6- to l&month follow-up there is no correlation between condylar position and development of TMJ symptoms. The occurrence of TMJ dysfunction is known to be multifactorial. The relative absence of TMJ and MPD symptoms in the presence of posterior condylar position can be attributed to several factors. The amount of posterior positioning or displacement of the condyle may be within the physiologic tolerance of the temporomandibular joint. The resultant establishment of the desired postoperative occlusion may eliminate any pre-existing occlusal disharmonies and thereby alleviate preoperative TMJ symptoms.28 The reduction of clicking and popping observed in some of the symptomatic patients during the postoperative period may represent further anterior disc displacement without reduction. This, in part, may be due to changes in condylar position, not necessarily reflecting the actual soft tissue changes.” Lastly, there may be the patient’s inherent ability to adapt neuromuscularly to changes resulting from superior maxillary repositioning.29,30 There are a number of factors that can be identified as contributing to the postoperative posterior repositioning of the condyle. A discrepancy between centric occlusion and maximum occlusal intercuspation is occasionally seen in patients exhibiting vertical maxillary hyperplasia with anterior apertognathia. Although we were aware of this discrepancy, and used an interocclusal wafer to minimize the frequency and magnitude of an acquired centric occlusion, some patients still demonstrated preoperative anterior condylar displacement secondary to this occlusal discrepancy. This, in part, contributed to postoperative posterior condylar repositioning, which in some patients actually represented seating of the condyle in the fossa from an acquired centric occlusal position. The mandibular autorotation that follows superior maxillary repositioning results in rotation of the condyle along its long axis, and this may also result in the appearance of posterior displacement of the condyle as it rotates in the fossa. Hence, the magnitude of the axis of condylar rotation is directly related to the amount of vertical impaction. Lastly, the possibility exists for a bodily shift of the mandible as a result of the autorotation of the maxillomandibular complex affecting condylar position. This factor can be attributable to existing soft tissue tension and resistance as the maxillomandibular complex is accommodated in the desired postoperative position. 3’ Intraoperatively, the supine position of the patient and the use of muscle relaxants during general anesthesia can influence bodily displacement of the mandible. In addition, the unde-
tected presence of residual bony interferences at the osteotomy sites can potentially contribute to posterior repositioning of the condyle as an effect of mandibular bodily shift after autorotation of the maxillomandibular complex. Despite these consequences, however, we have found no causeand-effect relationship between condylar position and the manifestation of TMJ dysfunction in asymptomatic and symptomatic patients during the preand postoperative periods. References 1. Hall D, Roddy SC: Treatment of maxillary alveolar hyperplasia by total maxillary osteotomy. J Oral Surg 30:262, 1972 2. West RA, Epker BN: Maxillary alveolar hyperplasia: Diagnosis and treatment planning. J Maxillofac Surg 4:239, 1975 3. Fish LC, Wolford LM, Epker BN: Surgical-orthodontic correction of vertical maxillary excess. Am J Orthod 73:241, 1978 4. O’Ryan FS, Epker BN: Surgical orthodontics
and the temporomandibular joint. I. Superior repositioning of the maxilla. Am J Orthod 83:408, 1983 5. Kahnberg KE: Temporomandibular joint complications associated with superior repositioning of the maxilla. J Craniomandib Pratt 6:312, 1988 6. Ricketts RM: Abnormal function of the temporomandibular joint. Am J Orthod 41:435, 1955 7. Laskin DM: Etiology of the pain-dysfunction syndrome. J Am Dent Assoc 79:147, 1969 8. Farrar WB: Diagnosis and treatment of anterior dislocation of the articular disc. NY J Dent 41:348, 1971 9. Weinberg LA: Correlation of temporomandibular dysfunction with radiographic findings. J Prosthet Dent 28:519, 1972 10. Farrar WB: Characteristics of condylar path in internal derangements of the temporomandibular joint. J Prosthet Dent 39:319, 1978 11. Weinberg LA: Role of condylar position in temporomandibular dysfunction-pain syndrome. J Prosthet Dent 41:636, 1979 12. Blaschke DD, Solberg WK, Sanders B: Arthrography of the temporomandibular joint: Review of current status. .I Am Dent Assoc 100:388, 1980 13. Owen AH: Orthodontic/orthopedic treatment of craniomandibular pain dysfunction. Part 2: Posterior condylar displacement. J Craniomandib Pratt 2:333, 1984b 14. Markovic M, Rosenberg H: Tomographic evaluation of 100 TMJ patients. Oral Surg 42:838, 1976 15. Katzberg RW, Keith DA, Ten Eick WR, et al: Internal derangements of the temporomandibular joint: An assessment of condylar position in centric occlusion. J Prosthet Dent 49:250, 1983 16. Costen JB: Syndrome of ear and sinus symptoms dependent upon distributed function of the temporomandibularjoint. Ann Otol Rhino1 Laryngo143: 1, 1934 17. Perry HT: Relation of occlusion to temporomandibular joint dysfunction: The orthodontic viewpoint. J Am Dent Assot 79: 137, 1969 18. Madsen B: Normal variations in anatomy, condylar movements, and arthrosis frequency of the temporomandibular joint. Acta Radio1 Diagn 4:273, 1%6 19. Blaschke DD, Blaschke TJ: Normal bony relationships in centric occlusion. J Dent Res 60:98, 1981
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20. Rieder CE, Martinoff JT: Comparison of the multiphasic dysfunction profile with lateral transcranial radiographs. J Prosthet Dent 52:572, 1984 21. Pullinger AG, Hollender L, Solberg WK, et al: A tomographic study of mandibular condyle position in an asymptomatic population. J Prosthet Dent 53:706, 1985 22. Bean LR, Thomas CA: Significance of condylar positions in patients with temporomandibular disorders. J Am Dent Assoc 114:76, 1987 23. Fomero RJ: The progression of temporomandibular joint dysfunction symptoms in treated and untreated patients. Thesis, Department of Orthodontics, St Louis University, 1989 24. Frost RA: The relationship between condylar position and temporomandibular joint status in subjects with untreated malocclusion. Thesis, Department of Orthodontics, St Louis University, 1989 25. Beckwith P, Monfort D, Williams B: Accurate depth of cut in temporomandibular joint laminographs. Angle Orthod 50:16, 1980 26. Dumas AL, Neff PA, Moaddab MB, et al: A combined to-
EFFECT OF CONDYLAR POSITION ON TMJ FUNCTION
27.
28. 29.
30.
31.
mographic-cephalometric analysis of the temporomandibular joint. J Craniomandib Pratt 1:24, 1983 Pulliiger AG, Solberg WK, Hollender S, et al: Relationship of mandibular condylar position to dental occlusion factors in an asymptomatic population. Am J Orthod Dentofac Orthop 91:200, 1987 Bell WH, Gonyea W, Finn RA, et al: Muscular rehabilitation after orthognathic surgery. Oral Surg 56:229, 1983 Wessberg GA, O’Ryan FS, Washburn MC, et al: Neuromuscular adaptation to surgical superior repositioning of the maxilla. J Maxillofac Surg 9: 117, 1981 Finn RA, Thockmorton GS, Gonyea WJ, et al: Neuromuscular aspects of vertical maxillary dysplasia, in Bell WE, Protitt WR, White RP (eds): Surgical Correction of Dentofacial Deformities. Philadelphia, PA Saunders, 1980, pp 1712-1730 Wessberg GA, Washburn MC, Labanc JP, et al: Autorotation of the mandible: Effect of surgical superior repositioning of the maxilla on mandibular resting posture. Am J Orthod 81:465, 1982
Surg
46:690-696.1990
Condylar Position in Superior Maxillary Repositioning and Its Effect on the Temporomandibular Joint EUGENIO G. HERBOSA, DMD, MMSc,* KENNETH S. ROTSKOFF, BERNARD F. RAMOS, MD,+ AND HENRYS. AMBROOKIAN,
DDS, MD,t DDS§
Twenty-nine patients (58 joints) were tomographically evaluated for condylar position and assessed for temporomandibular joint function following superior maxillary repositioning with mandibular autorotation. Seventy-six percent of the condyles showed postoperative posterior repositioning, whereas tomographic measurement of the joint spaces revealed significant posterior condylar position (P < .Ol) relative to the preoperative position. Pre- and postoperative comparative values of condylar displacement from absolute concentricity based on the Pullinger index also showed posterior condylar repositioning postoperatively (P -C ,001). However, there was no correlation between condylar position and the presence of temporomandibular joint symptoms in both the asymptomatic and symptomatic groups.
clicking and popping after the release of maxillomandibular fixation. All TMJ symptoms eventually resolved after a few months, and there was no evidence of myofascial pain or dysfunction (MPD) observed in any of their patients either pre- or postoperatively. On the other hand, in a recent study, Kahnberg reported that 60% of his 13 patients who underwent superior maxillary repositioning developed symptoms of painful TMJ clicking, decreased mandibular range of motion, and MPD.’ Many clinicians have associated myalgia, arthralgia, internal derangement, and arthrosis with nonconcentric condylar position in the glenoid fossa.&13 However, Markovic and Rosenberg, in their tomographic evaluation of 100 patients, showed that 86% of their symptomatic patients had concentric condyles.t4 Likewise, Katzberg et al arthrographitally demonstrated no statistical difference in condylar position between asymptomatic and symptomatic patients. I5 A number of investigators also have claimed that posteriorly positioned condyles are a precursor to anterior disc dislocation/displacementgY” and consequent development of TMJ and myofascial pain and dysfunction.‘1~‘3716,17However, other studies have shown a wide variation of condylar position in selected
Superior repositioning of the maxilla with mandibular autorotation is widely advocated as a surgical treatment for the correction of vertical maxillary hyperplasia with or without anterior apertognathia. l-3 The significance of the postoperative condylar position in relation to postoperative temporomandibular joint (TMJ) function is, however, controversial. O’Ryan and Epker,4 in a retrospective study of 10 randomly selected patients showed 60% of their patients to have posteriorly positioned condyles after treatment, but they claimed that only 15% of the joints exhibited immediate postoperative * Fellow, Oral and Maxillofacial Surgery, St Mary’s Health Center and Dentofacial Deformities and Orofacial Pain Center, St Louis, MO. t Program Director, Oral and Maxillofacial Surgery, St Mary’s Health Center and Dentofacial Deformities and Orofacial Pain Center, St Louis, MO. $ Research Fellow, Washington University School of Medicine, St Louis, MO. 8 In private practice, Milwaukee, WI. Address correspondence and reprint requests to Dr Herbosa: Orofacial Pain Center, 1031 Bellevue, Suite 310, St Louis, MO 63117. 0 1990 geons
American
Association
of Oral
and
Maxillofacial
Sur-
0278-2391/90/4807-0005$3.00/0
690
691
HERBOSAETAL asymptomatic18~” and symptomatic populations,22 thereby questioning the diagnosis of internal derangement based solely on a tomographically determined condylar position. Most recently, it has been shown that there was high statistical variability and unpredictability of condylar position as it relates to TMJ disorders in both asymptomatic and symptomatic groups.22-24 This further implies that there is insufficient evidence to support the contention that a nonconcentric condyle-fossa relationship predisposes to TMJ disorders. The purpose of this study was to compare and quantify the pre- and postoperative changes in condylar position following superior repositioning of the maxilla and to clinically evaluate its effect on the TMJ. Likewise, this study compared the changes in condylar position in patients with or without temporomandibular joint symptoms. Materials and Methods The study was based on 29 patients (58 joints), 19 females and 10 males, with a mean age of 20.2 years (range, 16 to 33 years). All were diagnosed as having vertical maxillary hyperplasia, with 20 of the patients exhibiting anterior apertognathia. All patients were treated orthodontically and underwent superior repositioning of the maxilla via a one-piece (13 patients) or segmental (16 patients) Le Fort I osteotomy. The range of impaction was from 3 to 7 mm. Semirigid (Steinman pins) or rigid fixation (bone plates) was used to stabilize the maxilla in its predetermined postoperative position. Maxillomandibular fixation was maintained from 5 days to 4 weeks depending on the type of fixation. The interocclusal splint remained for at least 3 weeks (one-piece cases) or up to 10 to 12 weeks for segmental cases requiring transverse expansion.
RADIOGRAPHICASSESSMENTOF CONDYLAR POSITION Preoperative and postoperative condylar positions were evaluated from left and right cephalometric linear full-head tomograms (QuintSectograph, Los Angeles, CA). These were corrected for axial rotation based on a submentovertex radiograph as described by Beckwith et a1.2s Preoperatively, the views were obtained with the mandible in centric occlusion using Coprwax bite wafers (Surgident, Columbus Dental Co, St Louis, MO) to stabilize the occlusion and to minimize the
likelihood of the patient’s slipping into an acquired centric occlusion. The same interocclusal wafer was used to orient the mandibular cast to the maxillary cast for purposes of model surgery. The casts were mounted on a semiadjustable articulator (Denar Mark-4, Anaheim, CA) with the maxillary cast oriented using a facebow transfer. Three to five days after surgery, postoperative tomograms were taken, with the occlusion stable in the interocclusal splint. DETERMINATIONOF JOINT SPACES AND CONDYLARDISPLACEMENT All pre- and postoperative left and right full-head tomograms were independently traced, joint spaces measured to the nearest tenth of a millimeter, and evaluated for condylar position by three different individuals (Fig 1). The Frankfort horizontal (porion to orbitale), mandibular condyle, and glenoid fossa landmarks were traced on an 8 x 10 inch 0.003 cephalometric acetate paper. Perpendicular lines were then drawn tangential to the anterior and posterior surfaces of the mandibular neck (a and b). A parallel line to FH was drawn tangential to the superior surface of the condyle (c). The distance between a and b was then measured, and another line (d) was drawn parallel to line c using this dimension to form a perfect square. Two diagonal lines were then drawn intersecting each other and extending to the fossa outline. The intersection was interpreted as the center of the condyle.26 Another vertical line (e), parallel to lines a and b, was drawn across the center of the condyle to the fossa outline. The three lines formed in the intra-articular spaces were designated as anterior (A), superior (S), and posterior (P) joint spaces (Fig 1). Preoperative and postoperative changes in condylar position were quantitatively defined as a decimal percentage of displacement from a position S
FIGURE 1. Determination of anterior (A), superior (s), and posterior (P)joint spaces based on Frankfort horizontal (FH) and geometric center of the condyle.
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EFFECT OF CONDYLAR POSITION ON TMJ FUNCTION
of absolute concentricity (0) in the fossa. These were based on an index modified from the Pullinger et al formula*‘: posterior posterior
- anterior joint space + anterior joint space
According to this index, complete posterior condylar displacement (no posterior joint space), would equal - 1, complete anterior condylar displacement (no anterior joint space) + 1, and absolute or perfect concentricity 0.27 To correlate the relationship of this index to the actual condylar displacement in millimeters, a change of 0.1 was considered approximately equal to a OS-mm to 0.6-mm difference in either the anterior or posterior direction (personal communication, Drs L. Johnston and A. Frost, St Louis University, Department of Orthodontics) .
CLINICALEVALUATION OF THE TEMPOROMANDIBULARJOINT
All patients were evaluated for internal derangement and myofascial pain and dysfunction pre- and postoperatively using the following criteria: range of mandibular opening (measured interincisally in millimeters) and lateral excursions (measured from facial midline in millimeters); presence of joint noises such as clicking, popping, or crepitation by auscultation; and myofascial pain and tenderness by palpation. TMJ function was further assessed using the same criteria 12 months after surgery (range, 6-18 months). Table 1. Tomographic Measurement (mm) of Anterior, Superior, and Posterior Joint Spaces Preoperative Left (29 joints) Anterior Superior Posterior* Right (29 joints) Anterior Superior Posterior* Left and right (58 joints) Anterior? Superior Posteriort
Postoperative
2.52 k 0.97 2.62 * 0.59 2.42 t 0.95
2.76 k 1.00 2.43 f 1.03 2.02 f 0.81
2.47 f 0.89 2.46 + 0.59 2.28 -f- 0.78
2.67 f 1.04 2.41 ” 0.64 1.99 ? 0.72
2.49 * 0.92 2.53 ? 0.85 2.35 2 0.86
2.72 2 1.02 2.41 k 0.85 2.00 f 0.76
Measurements are given as mean k SD. * Paired t test, P < .Ol. t Paired f test, P < .05.
Results
AND STATISTICALANALYSIS OF CONDYLAR POSITION
RADIOGRAPHIC
Table 1 shows the actual pre- and postoperative anterior, superior, and posterior joint space measurements. A tendency toward posterior condylar positioning was seen preoperatively, with further posterior repositioning postoperatively. When the right and left side values were combined, the difference was statistically significant at P < .Ol. The combined superior joint space values, although not significant, showed a tendency toward superior condylar repositioning after surgery. Table 2 shows the frequency of condylar position based on the actual anterior and posterior joint space measurements. Preoperatively, both left and right condyles showed a tendency to posterior positioning in about 52% of the joints. Postoperatively, further posterior condylar positioning was seen in 76% of the joints (left and right joints combined), with only 26% and 1.7% of the joints, respectively, exhibiting anterior and concentric positions. Table 3 shows the actual deviation in condylar displacement from absolute concentricity (0) as based on the Pullinger index. As mentioned previously, an anterior position is denoted by a positive ( +) value and a posterior position with a negative ( - ) value. The differences between ail pre- and postoperative values for the left and right sides alone or combined were statistically significant at P < .OOl. An approximate 0.5-mm to 0.6-mm postoperative condylar displacement, relative to the preoperative position, was seen. These findings Table 2. Frequency of Tomographic Condylar Position Based on Actual Joint Soace Measurements (%) Left (29 joints) Anterior Concentric Posterior Right (29 joints) Anterior Concentric Posterior Left and right (58 joints) Anterior Concentric Posterior
Preoperative
Postoperative
12/29 (41 .O%) 2/29 (6.9%) 15/29 (51.7%)
8129 (27.6%) l/29 (3.5%) 20/29 (69.0%)
12/29 (41 .O%) 2/29 (6.9%) 15/29 (51.7%)
7129 (24.0%) O/29 (0.0%) 22/29 (76.0%)
24/58 (41 .O%) 4/58 (6.9%) 30/58 (52.0%)
15/58 (26.0%) l/58 (1.7%) 42/58 (76.0%)
Numerator, no. of joints in respective position; denominator, total no. of joints.
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Table 3. Comparative Pullinger Index* Values of Condylar Displacement From Absolute Concentricity (0)
Left (29 joints)t Right (29 joints)? Combined (58 joints)t
Preoperative
Postoperative
-0.02 2 0.26 -0.04 2 0.26 -0.03 + 0.26
-0.14 * 0.26 -0.13 2 0.29 -0.13 k 0.28
tistically significant (P < .05), with a change toward the posterior direction in both groups. This is reflected postoperatively in that 68.4% of females and 80% of males showed posterior repositioning of the condyle in the fossa.
TEMPOROMANDIBULAR Values are given as mean 2 SD. * Negative values = posterior condylar position from absolute concentricity (0); 0.1 change - 0.5 mm displacement. t Paired t test, P < .OOl.
correlated with the tomographic measurements described in Tables 1 and 2, confirming postoperative condylar repositioning (Fig 2). Table 4 shows the comparative values for females and males to clarify the differences in condylar position between these groups. Preoperatively, there was a tendency toward posterior condylar positioning in 52.6% of the female group and in 50% of the male population. Postoperatively, males showed a significantly greater tendency toward posterior repositioning than females. The 0.16 Pullinger index difference in the male group corresponded to approximately a 0.75mm posterior displacement in condylar position as compared with a .086 change (0.4 mm) in the female group. The difference in Pullinger indices pre- and postoperatively for both groups was statistically significant (P < .Ol). Likewise, the difference in anterior joint space values during the pre- and postoperative periods was sta-
JOINT EVALUATION
Preoperatively, 11 of 29 patients (37.9%) examined showed symptoms of internal derangement and myofascial pain and dysfunction. Table 5 summarizes the pre and 1Zmonth postoperative findings, showing a marked decrease in symptoms in 5 of the previously 11 symptomatic patients. There was a slight, although not statistically significant, decrease in the postoperative mandibular range of motion. The condylar position in asymptomatic and symptomatic patients was evaluated as shown in Table 6. Almost 56% of the asymptomatic group demonstrated posterior condylar positioning preoperatively compared with 45.5% in the symptomatic group. Further posterior repositioning was seen after surgery in both groups. Interestingly, the asymptomatic group demonstrated a greater degree of posterior repositioning than the symptomatic group. The differences, however, were not statistically significant. Pre- and postoperative Pullinger indices confirmed consistent posterior condylar position in both groups (Table 6).
FIGURE 2. A, Preoperative position. B, Representative condylar position after mandibular autorotation following superior maxillary repositioning, showing tendency to posterior condylar repositioning.
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EFFECT OF CONDYLAR POSITION ON TMJ FUNCTION
Table 4. Comparative Joint Space Measurements (mm), Puiiinger index Values, and Frequency (%) of Condyiar Position in Female and Male Groups
No. of patients Total no. of joints Preoperative Anterior* Posterior Pullinger index Postoperative Anterior* Posterior Pullinger index
Female
Male
19 38
10 20
Asymptomatic
2.29 -+ 0.76 (31.6%) 2.89 * 1.09 (50%) 2.54 +- 1.00 (50%) 2.26 f 0.78 (52.6%) -0.004 2 0.24t -0.06 * 0.297 3.13 f 1.15 (20%) 2.50 f 0.89 (28.9%) 1.96 f 0.87 (80%) 2.02 k 0.70 (68.4%) -0.22 -+ 0.29t -0.09 k 0.26t
Values are given as mean f SD. Negative Pullinger index values = posterior condylar position from absolute concentricity (0); 0.1 change = 0.5 mm displacement. Frequency percentage is based on no. of joints in respective position/total no. of joints in each group. * Unpaired t test, P < .05. t Preoperative vs Postoperative paired t test, P < .Ol.
Discussion
There is paucity of information regarding condylar position and its effect on the temporomandibular joint after superior maxillary repositioning with mandibular autorotation. Recently, Kahnberg’ reported that 60% of his patients developed some form of TMJ disorder after undergoing this procedure. Despite the absence of radiographic evaluation of condylar position, he speculated that development of these symptoms was secondary to “squeezing of the disc.” This implies anterior condylar repositioning with disc displacement, contrary to our present study. Conversely, O’Ryan and Epker,4 in their retrospective study supported by Table 5. Summary of Frequency of Subjective and Clinical Manifestations of Temporomandibuiar Joint Function in the Symptomatic Group (%) Preoperative Symptomatic patients Range of motion (mm) Mandibular opening* Lateral excursions Joint noises Clicking Popping Crepitation TMJ-myofascial pain
Postoperative
1l/29 (37.9%)
6/29 (20.7%)
48.77 + 6.00 10.2-10.3
46.92 ” 8.20 9.4-9.8
8129 (27.6%) l/29 (3.5%) l/29 (3.5%) 8/29 (27.6%)
5/29 (17.2%) O/29 (0.0%) l/29 (3.5%) 2/29 (6.8%)
Numerator, no. of symptomatic patients; denominator, no. of patients. * Paired t test, P > .05. t Right-left mean lateral excursions.
Table 6. Comparative Joint Space Measurements (mm), Puiiinger Index Values, and Frequency (%) of Condylar Position in the Asymptomatic and Symptomatic Groups
total
Symptomatic
Preoperative No. of patients* 18/29 (62.1%) 1l/29 (37.9%) Condylar positiont Anterior* 2.72 2 0.94 (36.1%) 2.14 + 0.78 (45.5%) Posterior 2.38 f 0.88 (55.5%) 2.27 f 0.82 (45.5%) Pullinger index -0.07 k 0.26 -0.04 * 0.25 Postoperative No. of patients* 6129 (20.7%) 23129 (79.3%) Condylar positiont Anterior 2.79 k 1.00 (23.9%) 2.42 + 1.06 (50.0%) Posterior 2.00 k 0.84 (73.9%) 2.00 + 0.34 (41.7%) Pullinger index -0.16 2 0.27 -0.01 + 0.28 Values are given as mean 2 SD. Negative Pullinger index values = posterior condylar position from absolute concentricity (0); 0.1 change = 0.5 mm displacement. * Numerator, no. of patients in each group; denominator, total no. of patients. t Percentage based on no. of joints in respective position/total no. of joints. $ Unpaired t test, P < .05.
tomographic evaluation, showed that 60% of their patients had posteriorly positioned condyles. In addition, 15% of the joints that were symptomatic had reduction of TMJ and MPD symptoms after surgery, which was consistent with our findings. The effect of condylar position and the relationship to the development of TMJ disorders has remained controversial in the literature.8’10-15V22*27 Numerous investigators have associated abnormal joint function with “distalized” condylar position. 11*13*16,17 However, several studies have found no significant statistical difference in condylar position between asymptomatic and symptomatic Although 51.7% of our patients populations. 15*22v27 demonstrated a preoperative tendency to posterior condylar position, only 37.9% of the patients exhibited symptoms of TMJ and myofascial disorders. Postoperatively, 76% of the joints studied showed a significant posterior condylar repositioning, corresponding to approximately 0.5 mm to 0.6 mm of actual change as based on the Pullinger index. In spite of these changes, we observed a reduction in the number of symptomatic patients (20.7%). In addition, there was no significant difference in the measured condylar position between the asymptomatic and symptomatic patients either pre- or postoperatively. More significantly, the asymptomatic group demonstrated more posterior condylar displacement than the symptomatic group in the postoperative period. These findings suggest that
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during a 6- to l&month follow-up there is no correlation between condylar position and development of TMJ symptoms. The occurrence of TMJ dysfunction is known to be multifactorial. The relative absence of TMJ and MPD symptoms in the presence of posterior condylar position can be attributed to several factors. The amount of posterior positioning or displacement of the condyle may be within the physiologic tolerance of the temporomandibular joint. The resultant establishment of the desired postoperative occlusion may eliminate any pre-existing occlusal disharmonies and thereby alleviate preoperative TMJ symptoms.28 The reduction of clicking and popping observed in some of the symptomatic patients during the postoperative period may represent further anterior disc displacement without reduction. This, in part, may be due to changes in condylar position, not necessarily reflecting the actual soft tissue changes.” Lastly, there may be the patient’s inherent ability to adapt neuromuscularly to changes resulting from superior maxillary repositioning.29,30 There are a number of factors that can be identified as contributing to the postoperative posterior repositioning of the condyle. A discrepancy between centric occlusion and maximum occlusal intercuspation is occasionally seen in patients exhibiting vertical maxillary hyperplasia with anterior apertognathia. Although we were aware of this discrepancy, and used an interocclusal wafer to minimize the frequency and magnitude of an acquired centric occlusion, some patients still demonstrated preoperative anterior condylar displacement secondary to this occlusal discrepancy. This, in part, contributed to postoperative posterior condylar repositioning, which in some patients actually represented seating of the condyle in the fossa from an acquired centric occlusal position. The mandibular autorotation that follows superior maxillary repositioning results in rotation of the condyle along its long axis, and this may also result in the appearance of posterior displacement of the condyle as it rotates in the fossa. Hence, the magnitude of the axis of condylar rotation is directly related to the amount of vertical impaction. Lastly, the possibility exists for a bodily shift of the mandible as a result of the autorotation of the maxillomandibular complex affecting condylar position. This factor can be attributable to existing soft tissue tension and resistance as the maxillomandibular complex is accommodated in the desired postoperative position. 3’ Intraoperatively, the supine position of the patient and the use of muscle relaxants during general anesthesia can influence bodily displacement of the mandible. In addition, the unde-
tected presence of residual bony interferences at the osteotomy sites can potentially contribute to posterior repositioning of the condyle as an effect of mandibular bodily shift after autorotation of the maxillomandibular complex. Despite these consequences, however, we have found no causeand-effect relationship between condylar position and the manifestation of TMJ dysfunction in asymptomatic and symptomatic patients during the preand postoperative periods. References 1. Hall D, Roddy SC: Treatment of maxillary alveolar hyperplasia by total maxillary osteotomy. J Oral Surg 30:262, 1972 2. West RA, Epker BN: Maxillary alveolar hyperplasia: Diagnosis and treatment planning. J Maxillofac Surg 4:239, 1975 3. Fish LC, Wolford LM, Epker BN: Surgical-orthodontic correction of vertical maxillary excess. Am J Orthod 73:241, 1978 4. O’Ryan FS, Epker BN: Surgical orthodontics
and the temporomandibular joint. I. Superior repositioning of the maxilla. Am J Orthod 83:408, 1983 5. Kahnberg KE: Temporomandibular joint complications associated with superior repositioning of the maxilla. J Craniomandib Pratt 6:312, 1988 6. Ricketts RM: Abnormal function of the temporomandibular joint. Am J Orthod 41:435, 1955 7. Laskin DM: Etiology of the pain-dysfunction syndrome. J Am Dent Assoc 79:147, 1969 8. Farrar WB: Diagnosis and treatment of anterior dislocation of the articular disc. NY J Dent 41:348, 1971 9. Weinberg LA: Correlation of temporomandibular dysfunction with radiographic findings. J Prosthet Dent 28:519, 1972 10. Farrar WB: Characteristics of condylar path in internal derangements of the temporomandibular joint. J Prosthet Dent 39:319, 1978 11. Weinberg LA: Role of condylar position in temporomandibular dysfunction-pain syndrome. J Prosthet Dent 41:636, 1979 12. Blaschke DD, Solberg WK, Sanders B: Arthrography of the temporomandibular joint: Review of current status. .I Am Dent Assoc 100:388, 1980 13. Owen AH: Orthodontic/orthopedic treatment of craniomandibular pain dysfunction. Part 2: Posterior condylar displacement. J Craniomandib Pratt 2:333, 1984b 14. Markovic M, Rosenberg H: Tomographic evaluation of 100 TMJ patients. Oral Surg 42:838, 1976 15. Katzberg RW, Keith DA, Ten Eick WR, et al: Internal derangements of the temporomandibular joint: An assessment of condylar position in centric occlusion. J Prosthet Dent 49:250, 1983 16. Costen JB: Syndrome of ear and sinus symptoms dependent upon distributed function of the temporomandibularjoint. Ann Otol Rhino1 Laryngo143: 1, 1934 17. Perry HT: Relation of occlusion to temporomandibular joint dysfunction: The orthodontic viewpoint. J Am Dent Assot 79: 137, 1969 18. Madsen B: Normal variations in anatomy, condylar movements, and arthrosis frequency of the temporomandibular joint. Acta Radio1 Diagn 4:273, 1%6 19. Blaschke DD, Blaschke TJ: Normal bony relationships in centric occlusion. J Dent Res 60:98, 1981
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20. Rieder CE, Martinoff JT: Comparison of the multiphasic dysfunction profile with lateral transcranial radiographs. J Prosthet Dent 52:572, 1984 21. Pullinger AG, Hollender L, Solberg WK, et al: A tomographic study of mandibular condyle position in an asymptomatic population. J Prosthet Dent 53:706, 1985 22. Bean LR, Thomas CA: Significance of condylar positions in patients with temporomandibular disorders. J Am Dent Assoc 114:76, 1987 23. Fomero RJ: The progression of temporomandibular joint dysfunction symptoms in treated and untreated patients. Thesis, Department of Orthodontics, St Louis University, 1989 24. Frost RA: The relationship between condylar position and temporomandibular joint status in subjects with untreated malocclusion. Thesis, Department of Orthodontics, St Louis University, 1989 25. Beckwith P, Monfort D, Williams B: Accurate depth of cut in temporomandibular joint laminographs. Angle Orthod 50:16, 1980 26. Dumas AL, Neff PA, Moaddab MB, et al: A combined to-
EFFECT OF CONDYLAR POSITION ON TMJ FUNCTION
27.
28. 29.
30.
31.
mographic-cephalometric analysis of the temporomandibular joint. J Craniomandib Pratt 1:24, 1983 Pulliiger AG, Solberg WK, Hollender S, et al: Relationship of mandibular condylar position to dental occlusion factors in an asymptomatic population. Am J Orthod Dentofac Orthop 91:200, 1987 Bell WH, Gonyea W, Finn RA, et al: Muscular rehabilitation after orthognathic surgery. Oral Surg 56:229, 1983 Wessberg GA, O’Ryan FS, Washburn MC, et al: Neuromuscular adaptation to surgical superior repositioning of the maxilla. J Maxillofac Surg 9: 117, 1981 Finn RA, Thockmorton GS, Gonyea WJ, et al: Neuromuscular aspects of vertical maxillary dysplasia, in Bell WE, Protitt WR, White RP (eds): Surgical Correction of Dentofacial Deformities. Philadelphia, PA Saunders, 1980, pp 1712-1730 Wessberg GA, Washburn MC, Labanc JP, et al: Autorotation of the mandible: Effect of surgical superior repositioning of the maxilla on mandibular resting posture. Am J Orthod 81:465, 1982
