Relationship between orthodontic treatment, condylar position, and internal derangement in the temporomandibular joint Jon Artun, DDS, Dr.Odont.,* Lars G. Hollender, DDS, Odont. Dr.,** and Edmond L. Truelove, DDS, MSD*** Seattle, Wash.
The purpose of this study was to test the hypothesis that retraction of maxillary front teeth may lock the mandible in a posterior position, and to evaluate any relationship between condylar position and signs and symptoms of internal derangements in the temporomandibular joint. A total of 29 female patients treated for Angle Class II, Division 1 malocclusion with extraction of maxillary first premolars and 34 female patients treated for Angle Class I malocclusion without tooth extraction consented to participate in a radiographic and clinical follow-up examination. The mean ages of the patients were 16.9 (SD 3.0) and 16.6 (SD 2.6) years, and the mean times after treatment were 1.6 (SD 1.0) and 1.5 (SD 0.9) years, respectively. Condylar position was measured in percent anterior and posterior displacement from absolute concentricity on lateral, central, and medial tomographic sections of each joint. Mean condylar position was more posterior at right central (P < 0.05) and medial (P < 0.01) tomographic sections in patients treated with extraction. The difference was due to a higher frequency of anteriorly positioned condyles in the nonextraction cases. No intergroup differences in the sagittal occlusal slide from CR to CO and the number of patients with clicking were found. However, the condyles were located more posteriorly in all tomographic sections (P < 0.05 for lateral, P < 0.001 for central and medial) in patients with clicking than in those without. (AM J ORTHODDENTOFACORTHOP1992;101:48-53.)
E
xcentric position of the condyle in the glenoid fossa 13 and internal derangements in the temporomandibular (TM) joint 47 may cause pain and dysfunction. In addition, an association has been found between posteriorly seated condyles in centric occlusion and anterior disk displacement. 8*° On the other hand, such condylar position may also be present in subjects without any signs and symptoms of disk displacement.11"12 Many subjects with anterior disk displacement may remain in the clicking phase throughout life without development of other signs or symptoms of TM diso r d e r s . 6,7 However, some subjects proceed to displacement of the disk without reduction (closed lock). Mobility and function may be restored in some of the patients with closed lock6; whereas the other patients proceed to phases of pain and constriction, character-
From the University of Washington. *Associate Professor, Department of Orthodontics. **Professor, Department of Oral Medicine, Division of Radiology. ***Associate Professor, Department of Oral Medicine. 811/32958
48
ized by active osteoarthrosis. 7 In the burned out stage of degenerative osteoarthrosis, crepitation may be the only lasting residual symptom of TM disorder, despite marked changes in shape and structure as observed radiographically. 7 Orthodontists have been accused of neglecting to consider condylar position when making treatment plans. 13In particular, the danger of extraction treatment has been pointed out. The logic is that "careless" ret,-action of front teeth may lock the mandible in a posterior position. 13.14 An increasing number of patients sue their orthodontist on the basis that such treatment has led to TM disorders. Studies on the relationship between orthodontic treatment on TM health are few.~S-2° Available data do not disclose any major differences between groups of treated and untreated subjects. However, the effect of particular treatment strategies has not been sufficiently analyzed. Attempts have been made to evaluate differences in condylar position between patients treated with extraction of maxillary premolars and controis. 1g'2° However, one study used patients treated with extraction of both maxillary and mandibular premolars. TM Accordingly, any retraction of mandibular
Volume 101
Number I
incisors m a y have reduced the potential for c o n d y l a r displacement. The other study was limited to patients without signs of internal derangements. -'° The purpose o f o u r study was to test the hypothesis that patients treated with extraction o n l y in the maxilla have increased prevalence o f posteriorly located condyles and to evaluate any relationship between condylar position and signs and s y m p t o m s o f internal derangements in the T M joint. MATERIALS AND METHODS Subjects. A total of 29 female subjects from ages 11.0 to 25.0 years (mean 16.9 years, SD 3.0) with a period of 0.1 to 3.0 years (mean 1.6 years, SD 1.0) after treatment for Angle Class II, Division 1 malocclusion with extraction of maxillary first premolars and 34 female subjects from ages 13.1 to 24.9 years (mean 16.6 years, SD 2.6) with a period of 0.3 to 3.0 years (mean 1.5 years, SD 0.9) after treatment for Angle Class I malocclusion without tooth extraction consented to participate in a radiographic and clinical follow-up examination. An acceptable treatment result was achieved in all patients, and only minimal relapse was observed. The patients treated with extraction had used headgear and Class II elastics for various periods. Only simple tooth movements were performed in the patients treated without extraction, without use of extraoral traction or interareh elastics. Radiographic examhzation. Panoramic radiographs were obtained with a Siemens Orthopantomograph-10 (Siemens AG, Erlangen, Germany), which used Kodak Lanex Regular screens and T-Mat G films (Eastman-Kodak, Rochester, N.Y.). The radiographs were taken with the mandible in a slightly protruded position and the focal trough coinciding with the dental arches. The condylar images were evaluated with a standard view box. Any changes in shape and structure were recorded. Sagittal corrected tomograms of each joint were obtained with the use of a Philips polytome (Philips Medical Systems, Eindhoven, The Netherlands) with a 48 ° hypocycloidal movement pattern. The panoramic radiograph was used as an initial guide to determine any asymmetries or marked deviations in angulation of the condyles. Final positioning of the patients was assisted with the use of fluoroscopy. Lateral, central, and medial radiographic sections of tess than 2 mm nominal thickness were obtained at 4 mm separation. Every effort was made to secure identical intercuspal position at each radiographic projection. Again, the same sensitive combination of screens and films, as well as a minimal radiation field, were used. A total of eight tomographic sections were eliminated from evaluation because of unsatisfactory quality: one lateral section and one medial section of the fight condyle and two lateral sections and one medial section of the left condyle of patients treated with extraction, and three medial sections of the right condyle of patients treated without extractions. The remaining radiographs were projected on a screen at about x 10 magnification. Linear measurements were made with a millimeter ruler to the nearest millimeter at what appeared to be the narrowest posterior and anterior interarticular
Effect of treatment on the TMJ
49
Fig. 1. Locations of measurement of narrowest anterior (A) and posterior (P) interarticular spaces in TM joint tomographs. ConP-A dylar position is expressed as ~ × 100
distance. Condylar position was expressed as a percent of anterior or posterior displacement from absolute concentricity (zero) according to the following formula (Fig. 1). t°-" posterior - anterior interarticular distance posterior + anterior interarticular distance
×
100%
Clinical examhtation. The amount of sagittal and lateral oeclusal slide between retruded contact position (CR) and maxinmm intercuspal position (CO) was assessed with the use of a vertical pencil line guide at the right and left premolars and by observation of the dental midlines at these two positions. The slide was measured to the nearest 0.5 mm. Temporomandibular joint sounds were recorded as present or absent by palpation. Any history of clicking or locking was also recorded. Presence of TM joint tenderness was examined by palpating the joint from the lateral section and from behind through the auditory meatus. Error of the method. The reproducibility in determining the condylar position was assessed by statistically analyzing the difference between double determinations made ! week apart on tomograms of 20 patients selected at random. The error of the method was calculated from the following equation:
S'=
~/ 2 N
where D is the difference between duplicated determinations and N is the number of double determinations.~ The error was 3% for each radiographic section in each joint. The maximum difference between double determinations was 11%. Data analysis. The different measurements of condylar position from lateral, central, and medial tomographic sections were averaged into one value per joint per patient. Measurements from each section were also analyzed separately. The Student's t test for independent means was used to determine any statistically significant differences in condylar position and sagittal occlusal slide from CR to CO between patients treated with and without extraction. A definite displacement of the condyle was defined as more than 12% deviation from concentricity." Chi-square test was used to determine any statistically significant differences in the number of patients with definite anterior and posterior condylar
50
~trtun, Hollender, and Truelove
Am. J. Orthod.Dentofac. Orthop. January 1992
Table I. Mean percent anterior ( + ) or posterior ( - ) displacement of condylar position from absolute concentricity (zero) measu,ed in lateral, central, and medial tomographic sections of the right and left condyles of patients treated with extraction of maxillary first premolars and without tooth extraction
Nonextraction
Extraction 414
I
x±SD Right Lateral Central Medial Left Lateral Central Medial
-6 -9 -5
x+-SD
I
Significance
- 17 ± 16 ± 18
28 29 28
+ l --- 21 0 ± 21 + ! 1 _-+ 23
34 34 31
NS P < 0.05 P
The purpose of this study was to test the hypothesis that retraction of maxillary front teeth may lock the mandible in a posterior position, and to evaluate any relationship between condylar position and signs and symptoms of internal derangements in the temporomandibular joint. A total of 29 female patients treated for Angle Class II, Division 1 malocclusion with extraction of maxillary first premolars and 34 female patients treated for Angle Class I malocclusion without tooth extraction consented to participate in a radiographic and clinical follow-up examination. The mean ages of the patients were 16.9 (SD 3.0) and 16.6 (SD 2.6) years, and the mean times after treatment were 1.6 (SD 1.0) and 1.5 (SD 0.9) years, respectively. Condylar position was measured in percent anterior and posterior displacement from absolute concentricity on lateral, central, and medial tomographic sections of each joint. Mean condylar position was more posterior at right central (P < 0.05) and medial (P < 0.01) tomographic sections in patients treated with extraction. The difference was due to a higher frequency of anteriorly positioned condyles in the nonextraction cases. No intergroup differences in the sagittal occlusal slide from CR to CO and the number of patients with clicking were found. However, the condyles were located more posteriorly in all tomographic sections (P < 0.05 for lateral, P < 0.001 for central and medial) in patients with clicking than in those without. (AM J ORTHODDENTOFACORTHOP1992;101:48-53.)
E
xcentric position of the condyle in the glenoid fossa 13 and internal derangements in the temporomandibular (TM) joint 47 may cause pain and dysfunction. In addition, an association has been found between posteriorly seated condyles in centric occlusion and anterior disk displacement. 8*° On the other hand, such condylar position may also be present in subjects without any signs and symptoms of disk displacement.11"12 Many subjects with anterior disk displacement may remain in the clicking phase throughout life without development of other signs or symptoms of TM diso r d e r s . 6,7 However, some subjects proceed to displacement of the disk without reduction (closed lock). Mobility and function may be restored in some of the patients with closed lock6; whereas the other patients proceed to phases of pain and constriction, character-
From the University of Washington. *Associate Professor, Department of Orthodontics. **Professor, Department of Oral Medicine, Division of Radiology. ***Associate Professor, Department of Oral Medicine. 811/32958
48
ized by active osteoarthrosis. 7 In the burned out stage of degenerative osteoarthrosis, crepitation may be the only lasting residual symptom of TM disorder, despite marked changes in shape and structure as observed radiographically. 7 Orthodontists have been accused of neglecting to consider condylar position when making treatment plans. 13In particular, the danger of extraction treatment has been pointed out. The logic is that "careless" ret,-action of front teeth may lock the mandible in a posterior position. 13.14 An increasing number of patients sue their orthodontist on the basis that such treatment has led to TM disorders. Studies on the relationship between orthodontic treatment on TM health are few.~S-2° Available data do not disclose any major differences between groups of treated and untreated subjects. However, the effect of particular treatment strategies has not been sufficiently analyzed. Attempts have been made to evaluate differences in condylar position between patients treated with extraction of maxillary premolars and controis. 1g'2° However, one study used patients treated with extraction of both maxillary and mandibular premolars. TM Accordingly, any retraction of mandibular
Volume 101
Number I
incisors m a y have reduced the potential for c o n d y l a r displacement. The other study was limited to patients without signs of internal derangements. -'° The purpose o f o u r study was to test the hypothesis that patients treated with extraction o n l y in the maxilla have increased prevalence o f posteriorly located condyles and to evaluate any relationship between condylar position and signs and s y m p t o m s o f internal derangements in the T M joint. MATERIALS AND METHODS Subjects. A total of 29 female subjects from ages 11.0 to 25.0 years (mean 16.9 years, SD 3.0) with a period of 0.1 to 3.0 years (mean 1.6 years, SD 1.0) after treatment for Angle Class II, Division 1 malocclusion with extraction of maxillary first premolars and 34 female subjects from ages 13.1 to 24.9 years (mean 16.6 years, SD 2.6) with a period of 0.3 to 3.0 years (mean 1.5 years, SD 0.9) after treatment for Angle Class I malocclusion without tooth extraction consented to participate in a radiographic and clinical follow-up examination. An acceptable treatment result was achieved in all patients, and only minimal relapse was observed. The patients treated with extraction had used headgear and Class II elastics for various periods. Only simple tooth movements were performed in the patients treated without extraction, without use of extraoral traction or interareh elastics. Radiographic examhzation. Panoramic radiographs were obtained with a Siemens Orthopantomograph-10 (Siemens AG, Erlangen, Germany), which used Kodak Lanex Regular screens and T-Mat G films (Eastman-Kodak, Rochester, N.Y.). The radiographs were taken with the mandible in a slightly protruded position and the focal trough coinciding with the dental arches. The condylar images were evaluated with a standard view box. Any changes in shape and structure were recorded. Sagittal corrected tomograms of each joint were obtained with the use of a Philips polytome (Philips Medical Systems, Eindhoven, The Netherlands) with a 48 ° hypocycloidal movement pattern. The panoramic radiograph was used as an initial guide to determine any asymmetries or marked deviations in angulation of the condyles. Final positioning of the patients was assisted with the use of fluoroscopy. Lateral, central, and medial radiographic sections of tess than 2 mm nominal thickness were obtained at 4 mm separation. Every effort was made to secure identical intercuspal position at each radiographic projection. Again, the same sensitive combination of screens and films, as well as a minimal radiation field, were used. A total of eight tomographic sections were eliminated from evaluation because of unsatisfactory quality: one lateral section and one medial section of the fight condyle and two lateral sections and one medial section of the left condyle of patients treated with extraction, and three medial sections of the right condyle of patients treated without extractions. The remaining radiographs were projected on a screen at about x 10 magnification. Linear measurements were made with a millimeter ruler to the nearest millimeter at what appeared to be the narrowest posterior and anterior interarticular
Effect of treatment on the TMJ
49
Fig. 1. Locations of measurement of narrowest anterior (A) and posterior (P) interarticular spaces in TM joint tomographs. ConP-A dylar position is expressed as ~ × 100
distance. Condylar position was expressed as a percent of anterior or posterior displacement from absolute concentricity (zero) according to the following formula (Fig. 1). t°-" posterior - anterior interarticular distance posterior + anterior interarticular distance
×
100%
Clinical examhtation. The amount of sagittal and lateral oeclusal slide between retruded contact position (CR) and maxinmm intercuspal position (CO) was assessed with the use of a vertical pencil line guide at the right and left premolars and by observation of the dental midlines at these two positions. The slide was measured to the nearest 0.5 mm. Temporomandibular joint sounds were recorded as present or absent by palpation. Any history of clicking or locking was also recorded. Presence of TM joint tenderness was examined by palpating the joint from the lateral section and from behind through the auditory meatus. Error of the method. The reproducibility in determining the condylar position was assessed by statistically analyzing the difference between double determinations made ! week apart on tomograms of 20 patients selected at random. The error of the method was calculated from the following equation:
S'=
~/ 2 N
where D is the difference between duplicated determinations and N is the number of double determinations.~ The error was 3% for each radiographic section in each joint. The maximum difference between double determinations was 11%. Data analysis. The different measurements of condylar position from lateral, central, and medial tomographic sections were averaged into one value per joint per patient. Measurements from each section were also analyzed separately. The Student's t test for independent means was used to determine any statistically significant differences in condylar position and sagittal occlusal slide from CR to CO between patients treated with and without extraction. A definite displacement of the condyle was defined as more than 12% deviation from concentricity." Chi-square test was used to determine any statistically significant differences in the number of patients with definite anterior and posterior condylar
50
~trtun, Hollender, and Truelove
Am. J. Orthod.Dentofac. Orthop. January 1992
Table I. Mean percent anterior ( + ) or posterior ( - ) displacement of condylar position from absolute concentricity (zero) measu,ed in lateral, central, and medial tomographic sections of the right and left condyles of patients treated with extraction of maxillary first premolars and without tooth extraction
Nonextraction
Extraction 414
I
x±SD Right Lateral Central Medial Left Lateral Central Medial
-6 -9 -5
x+-SD
I
Significance
- 17 ± 16 ± 18
28 29 28
+ l --- 21 0 ± 21 + ! 1 _-+ 23
34 34 31
NS P < 0.05 P
