Longitudinal evaluation of condylar position in extraction and nonextraction treatment Anthony A. Gianelly, DMD, PhD, MD, Cheryl K. Anderson, DDS, and Joseph Boffa, DDS, MPH Boston, Mass. In 111 patients pretreatment and posttreatment condylar position was evaluated with corrected tomograms taken with the mandible in centric occlusion. Seventy-nine of the patients were treated by nonextraction procedures and 32 were treated by extraction procedures, 27 of the patients with the extraction of one or more premolars and 5 with the extraction of one or more anterior teeth. When the condylar positions before and after treatment were compared in the entire sample of 111 patientsl in the nonextraction patients, in the extraction patients, and in extraction patients relative to nonextraction patients, no statistically significant differences were found. Thus condylar position was stable during treatment and did not behave differently under extraction and nonextraction conditions. On an individual basis, condylar relropositioning, as defined in this study, occurred in only nine of the 222 joints examined and was noted in patients treated both with and without extraction. (AMJ ORTHOO DENTOFACORTHOP 1991 ;100:416-20.)

C o n d y l a r position is an important consideration in orthodontics, in part because of two interrelated views. One is that posterior condylar position can lead to temporomandibular disease (TMD). For example, Farrar and McCarty ~ suggested that condylar retroposition is a predisposing factor to the development of an internal derangement. Similarly, Weinberg and Chastain 2 and o.thers 3-8 h'ave emphasized the association between posteriorly located condyles and TMD. The second view is that extraction treatment commonly results in distal displacement of the conclyles, t As explained by Farrar and McCarty ~ and implied by Witzig and Yerkes, 8 during space closure the maxillary incisor segment is retracted and, as a consequence, entraps the mandible and forces it posteriorly. Accordingly, nonextraction treatment may be preferable since condylar retropositiouing would not occur. There is no evidence to support the association between extraction treatment and condylar retroposition. On the contrary, the available information is that distal repositioning of the condyles during extraction treatment is not a compelling concern. 9 Specifically, no difference in condylar position was noted in a group of 30 patients treated by extraction procedures when compared with the positions of the condyles in a control sample. The present study will evaluate condylar position

From the Boston University School of Graduate Dentistry. 8/I/25704

416

longitudinally in extraction and nonextraction patients before and after treatment to define the changes that occur in condylar position in these patients and to determine whether the changes that occur are characteristic of extraction and nonextraction treatment.

MATERIALS AND METHODS One hundred eleven patients whose treatment records included treatment-corrected tomograms of the riglat and left condyles with the mandible in centric occlusion were included in this study. There were 42 men, with an average age of 20.2 years, and 69 women, with an averageage of 22.9 years. The edgewise appliance was used in 97 patients, and the light wire appliance was used in 14 patients. Of the patients 33 had a Class I malocclusion; 68 had a Class II, Division 1 malocclusion; three had a Class II, Division 1 malocclusion; and seven had a Class III malocclusion. Seventy-nine patients Were treated by nonextraction procedures (mean age, 20.7 years) and 32 (mean age, 25.3 years) were treated with the extraction of teeth, 27 of the patients with the extraction of one or more premolars and five with the extraction o f one or more antei:iol: teeth. The average treatment time was 20.7 months. Twelve 0fthe cases involved partial treatment (molar uprighting, one-arch leveling, and aligning or diastema closure) and 99 represented complete treatment. Twelve of the patients wore either cervical or highpull gear to correct the Class II malocclusion. The procedure for taking the corrected tomograms to identify condylar position in centric occlusion with the patient's head in the natural position has been previously described. 9''° Two linear tomographie units, the Axial Tome 60 (Axial Tome Corp., San Carlos, Calif.) and the Quint X-ray Sectograph (Quint X-ray Sectograph Corp., Los Angeles, CaliL), were

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used. The magnification factor of the Axial Tome 60 was 15%, and that of the Quint Sectograph was 11%. Computer analysis of the joint spaces and condylar position was performed on enhanced and enlarged images with a specific computer program? ° After the posterior, anterior, superior, and joint space values were derived, the ratio of posterior to anterior joint space was defined as the P/A ratio (the ratio of the posterior to the anterior joint space). A ratio of 1 indicated that the posterior and anterior joint spaces were equal and the condyle was in the midfossa position. As an example, if the posterior joint space were 2 mm, the anterior joint space would also be 2 mm. The condyles were considered to be concentric when the PIA ratio was between 0.8 and 1.2. In practical terms, this meant that the condyle would be no more than ±0.20 mm from the midfossa position in a fossa with 4 mm of anteroposterior joint space. For instance, a P / A ratio of 1.2 would indicate a fossa with approximately 2.2 mm posterior joint space and a 1.8 mm anterior joint space. A ratio of less than 0.8 mm would signify a posteriorly positioned condyle, and a ratio of greater than 1.2 would represent an anteriorly located ~:ondyle. To determine the reliability of the tracings, 10 images were selected at random and retraced at different times, and a correlation was derived between the first and the second tracings. Actual joint space measurements were calculated after correction for the magnification factor of the machine used for the specific image. Pretreatment and posttreatment condylar position, as represented by the PIA ratio, after log transformation," and the individual right and left joint spaces were compared in the following groups: (1) all the patients, (2) the extraction and nonextraction subjects, and (3) the 12 headgear patients compared with all other nonextraction patients. An analysis of variance for independent groups was used to test for the significance of these comparisons. We also identified individual condyles that were concentric or anterior before treatment and finished treatment in a retruded position. A condyle was arbitrarily considered to be in retroposition when the posterior joint space was less than 1.5 mm. The 1.5 mm limit was chosen because the posterior joint space noted in this study was 2.18 -.+ 0.88 mm, and in fossae with concentric condyles it commonly approximates 2 mm +--0.5 mm"U"; thus the 1.5 mm space represents the I SD boundary.

RESULTS The correlation coefficients comparing tracings prepared at two different time intervals ranged from 0.91 to 0.96 (Table I). This demonstrates that the tracing procedure was replicable. There were no statistical differences in condylar position when the right and left sides were compared. Therefore the sides were combined for analysis. Also, condylar position was not different in partial-treatment

Longitudinal evaluation of condylar position 417 Table !. Corrleation coefficients o f joint space measurements performed at different times Joint space

] I

Posterior Anterior Superior

r 0.918 0.962 0.946

Table II. Condylar position ( P / A ) PIA position Pretreatment (n = 111) Posttreatment (n = I 1 I)

1.38 !.3 i

Table III. Joint space measurements Joint space Posterior Anterior Superior

] [

Pretreatment (mm)

Posttreatment (ram)

!.95 -4- 0.77 1.69 +-- 0.83 2.58 +-- 0.93

1.96 -'- 0.73 1.74 - 0.71 2.73 --- 0.97

nonextraction patients than in full-treatment nonextraction patients and when nonextraction headgear subjects were compared with all other nonextraction patients. For these reasons, all nonextraction cases were combined.

CONDYLAR POSITION: BEFORE AND AFTER TREATMENT (Table II) The P / A ratio illustrating condylar position in centric occlusion in the 111 patients was 1.38 before treatment and 1.31 after treatment, indicating that the condyles were in essentially the same position before and after treatment. The minor difference was not statistically significant.

JOINT SPACES (Table III) The pretreatment and posttreatment posterior, anterior, and superior joint spaces are shown in Table IIl. There were no statistical differences in any o f the joint space measurements. The posterior joint space was 1.95 + 0.77 m m before treatment and 1.96 ± 0.73 m m after treatment. The anterior joint space was 1.69 ± 0.83 m m before treatment and 1.74 ± 0.71 m m after treatment. The superior joint space was 2.58 - 0.93 m m before treatment and 2.73 ± 0.97 mm after treatment.

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Am.J. Orthod.Dentofac.Orthop. November1991

Table IV. Condylar position (P/A)

at the start of treatment and 1.77 mm 4- 0.62 mm after treatment. The superior joint space, in the extraction group, was 2.61 mm ± 0.86 mm before treatment and 2.77 mm ± 0.97 mm after treatment (Table VII). In the nonextraction patients, the superior space was 2.57 mm _ 0.96 mm before treatment and it was 2.71 ± 0.96 mm after treatment.

418

I Extraction (n = 32) Nonextraction (n =

Pretreatment [ Posttreatment 1.41

1.33

1.33

1.26

79)

CONDYLAR POSITION AND HEADGEAR (Table VIII)

Table V. Posterior joint space

Pretrealment(ram) Extraction Nonextraction

1.92 __- 0.79 2.03 ± 0.71

I

Posltreatment(mm) 1 . 9 6 ± 0.75 1.94 ± 0.77

Table Vl. Anterior joint space

eretreatment (ram) Extraction Nonextraction

1.64 ± 0.79 1.85 -4- 0.94

eosttreatment (ram) 1.73 ± 0.74 1.77 --- 0.62

CONDYLAR POSITION: EXTRACTION VERSUS NONEXTRACTION (Table IV)

The P / A ratio for condylar position in the extraction group was 1.41 before treatment and 1.33 after treatment. In the nonextraction group, it was 1.33 before treatment and 1.26 after treatment. There were no statistical differences when the positions of the condyles were compared in (1) extraction patients before and after treatment, (2) nonextraction patients before and after treatment, (3) extraction and nonextraction patients before treatment and (4) extraction and nonextraction patients after treatment. JOINT SPACES (Tables V to VII)

The before- and after-treatment posterior, anterior, and superior joint spaces of the extraction and nonextraction groups are outlined in Tables V to VII. All differences were not statistically significant. In the extraction group, the posterior joint space was 1.92 mm ± 0.79 mm before treatment and 1.96 mm ± 0.75 mm after treatment (Table V). In the nonextraction group, the space was 2.03 mm ± 0.71 mm before treatment and 1.94 mm ± 0.77 mm after treatment. The anterior joint space in the extraction group was 1.64 mm ± 0.79 mm before treatment and 1.73 mm ± 0.74 mm after treatment (Table VI). In the nonextraction group, the space was 1.85 mm ± 0.94 mm

The P / A ratio for the headgear group was 1.43 before treatment and 1.29 after treatment. The P / A ratio for the nonextraction patients who did not use a headgear to correct the sagittal relationships was 1.38 at the start of treatment and 1.32 when treatment was completed. There were no statistical differences in condylar position when positions for each group were compared before and after treatment and when the respective groups were compared before and after treatment. Therefore headgear use did not influence the location of the condyles. POSTERIORLY POSITIONED CONDYLES

Only nine condyles were in a retruded position (i.e., the posterior joint space was less than 1.5 ram). The nine joints represented nine different patients, signifying that bilateral involvement did not occur in any patient. The posterior joint space in these subjects ranged from 0.98 mm to 1.29 mm. The right condyle was involved in six patients and the left condyle in the other three patients. In three patients, extractions were done (two involving the removal of two or more premolars and one in whom a maxillary lateral incisor was removed). Six patients were treated by nonextraction procedures, and only one used a headgear for Class II correction. DISCUSSION

Several questions prompted this longitudinal investigation. One question was, does mean condylar position change during orthodontic treatment? According to our results, the answer is "no!" The position of the condyles remained essentially stable with treatment as performed in this study. The actual change in both the anterior and the posterior joint spaces was less than 0. I mm. Since this investigation represents the only longitudinal tomographie evaluation of condylar position in orthodontic patients, there are no data available for comparison. Inferentially, the stability of condylar position is compatible with the observations of Johnston 15 and Sadowsky and Poison t6 that the retruded contact-intercuspal (RC-IC) relationships in a group of postorth-

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odontic patients were similar to those recorded in a control group. Since the RC-IC relationships were the same, one could assume that the condylar/fossa relationships also were comparable. On the other hand, Sadowsky and BeGole 17 identified a larger RC-IC discrepancy in a control group when compared to the RCIC slides of persons who had undergone orthodontic treatment at least 10 years previously. One might expect more anteriorly positioned condyles in the control group, reflecting the larger RC-IC movement. Sampling variation may help explain the inconsistencies since the same investigator was involved in two disparate studies. A second question was, is there a difference in condylar movement in extraction and nonextraction treatment as done in this study? Again, the answer is "no!" This means that extraction treatment was not preferentially associated with condylar distal repositioning, as suggested by Farrar and McCarty 1and by Witzig and Yerkess with implied potential for developing TMD. The condyles of both the nonextraction and the extraction patients were effectively in the same position before and after treatment. This result conforms to the findings of Dibbets et al.lS that there was no long-term difference in the symptoms of TMD in nonextraction patients treated with functional appliances than in extraction patients treated with the Begg appliance. The stability of condylar position in extraction patients is also consistent with the cross-sectional data indicating that condylar position in groups of postorthodontic extraction patients was the same as in the corresponding control samples. 9'~° In the 12 patients who used a headgear to correct Class II relationships, the positions of the condyles were the same as the positions noted in the other nonextraction patients. Since the headgear group was small, this finding needs confirmation with larger samples. However, it does not raise the concern that headgear therapy often results in condylar retropositioning, as presumed by Wyatt.19 It may also mean that observations noted in experimental animals are not directly relevant since 700 gm of high-pull traction applied to the maxillae of 8-pound monkeys for approximately 70 days led to resorption of the anterior surfaces of the postglenoid tubercles, possibly reflecting distal repositioning of the condyles, z° A comparable force in an 80-pound person would be 7000 gm or 15 to 16 pounds. The overall stability of condylar position noted in this study is not surprising in view of the fact that orthodontic treatment, for the most part, is not related to an increased incidence of T M D . 16'17"263 Temporomandibular disease has been associated with posterior condylar position. For example, Pullinger et a l . 24 determined that the condyles of 60 patients with sympI

Longitudinal evaluation of condylar position 419 Table VII. Superior joint space

eretreafment(mm) I Posttreatment(mm) Extraction Nonextraction

2.61 ± 0.86 2.57 - 0.96

2.77 _ 0.97 2.71 __- 0.96

Table VIII. Condylar position (P/A)

I Pretreatment l Posttreatment tleadgear (n = 12) Nonextraction (n = 67)

1.43

1.29

1.38

1.32

toms were more posterior than the condyles of 37 control patients. Similar results have been recorded by others. 2"46 Since orthodontic treatment has little effect on the incidence of TMD, one would not expect an increased incidence of aberrant condylar position, characteristic of patients with symptoms, in persons who had been orthodontically treated. Although the group data indicated stability of condylar position incident to orthodontic treatment, nine of the 222 condyles moved into a retruded position. This means that distal repositioning that placed the condyles into retroposition was a distinctly rare event, occurring less than 5% of the time. It never occurred bilaterally in any of the 111 patients. Metaphorically, in statistical testing, a sample of observations that occurs less than 5% of the time when compared to with the central tendency is so exceptional that it does not represent the main body of data. A similar assessment can be made of condylar retropositioning as a result of orthodontic treatment. It does not represent the normal or expected condition. For comparison purposes, it would be useful to know how many condyles in persons who have never received orthodontic treatment have moved to the posterior part of the fossa with time. Unfortunately, suitable information is not available. One would guess that distal repositioning would occur in untreated persons since condylar retroposition has been associated with TMD in the general population I-8.24and the incidence of TMD increases with age. 25 Equally significant, when condylar retropositioning occurred, it was noted in persons who had undergone both extraction and nonextraction treatment. Six of the nine patients with a condyle in a retruded position were treated by nonextraction procedures and only one patient wore a headgear to correct the Class II relationship.

420

Gianelly, Anderson, and Boffa

T h r e e patients w e r e treated with extractions, and incisor retraction occurred in o n l y one o f these patients. A l t h o u g h the incidence o f c o n d y l a r retropositioning in the two groups reflected the e x p e c t e d 2 : 1 nonextract i o n / e x t r a c t i o n ratio, a larger sample size is necessary to confirm this trend. Since c o n d y l a r retropositioning was associated with both extraction and nonextraction treatment as done in this study, it is clear that c o n d y l a r distal repositioning to the posterior part o f the fossa was not an exclusive function o f either type o f treatment. O n e interpretation o f these data, w h i c h need corroboration in other studies, is that c o n d y l a r position appears i n d e p e n d e n t o f c o n v e n t i o n a l extraction and nonextraction treatment strategies in w h i c h fixed appliances, including headgear, are used to correct malocclusions. T h e risk o f c o n d y l a r retropositioning is less than 5% and is not related to any single treatment modality or procedure. Thus c o n d y l a r position does not appear to be a pivotal consideration w h e n one is selecting treatment options. In practical terms, an extraction a p p r o a c h is not contraindicated because o f the potential for c o n d y l a r distal repositioning. B y a similar analysis, a nonextraction strategy should not be favored solely because o f an i m p u t e d salutory effect on condylar position. IqEFERElqOES 1. Farrar WB, McCarty WL. A clinical outline of t.emporomandibular joint diagnosis and treatment. Montgomery, Ala.: Walker Printing, 1983:84-5. 2. Weinberg LA, Chastain JK. New TMJ clinical data and the implication on diagnosis and treatment. J Am Dent Assoc 1990;120:305ol 1. 3. Ireland VE. The problem of "the clicking jaw". J Prosthet Dent 1953;3:200. 4. Blaschke DD, Solberg WK, Sanders B. Arthrography of the temporomandibular joint: review of current status. J Am Dent Assoc 1980;100:388. 5. Mongini E Abnormalities in condylar and occlusal positions. In: Solberg WT, Clark GT, eds. Abnormal jaw mechanics, diagnosis, and treatment. Chicago: Quintessence, 1984. 6. Ricketts RM. Abnormal function of the temporomandibular joint. AM J OR~tOD 1955;41:435-41. 7. OwenAH. Orthodontic/orthopedic treatment of mandibular dysfunction. Part 2. posterior condylar displacement. J Craniomandibular Pract 1984;2:344-9. 8. Witzig JW, Yerkes I. Functional jaw orthopedics; mastering more than a technique. In: Gelb, ed. Clinical management of head neck and TMJ pain and dysfunction. 2nd ed. Philadelphia: WB Saunders, 1985:604-5.

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Orthod. Dentofac. Orthop. November 1991

9. Gianelly AA, Hughes HM, Wohlgemuth R, Gildea G. Condylar position and extraction treatment. AM J ORTHODDENTOFACOR"ntOP 1988;93:201-5. 10. Gianelly AA, Cozzani M, Boffa J. Condylar position and maxillary first premolar extraction. A.~ J ORrltoD DE,~rfOFACORTItOP tin press]. t I. Pullinger AG, Hollander L. Variation in condylar fossa relationships according to different methods of evaluation in tomograms. Oral Surg Oral Med, Oral Pathol 1986;62:719-27. 12. Ismail Y, Rokni A. Radiographic study of condylar position in centric relation and centfic occlusion. J Prosthet Dent 1980; 44:656-66. 13. Weinberg LA. Correlation of temporomandibular dysfunction with radiographic findings. J Prosthet Dent 1972;28:519-39. 14. Gianelly AA, Petras JC, Boffa J. Condylar position and Class It deep bite no overjet malocclusions. AM J ORTHODDENTOFAC OR~oe 1989;96:428-32. 15. Johnston LE. Gnathologic assessment of centric slides in post retention orthodontic patients. J Prosthet Dent 1988;60:712-5. 16. Sadowsky C, Polson AM. Temporomandibular disorders and functional occlusion after orthodontic treatment: results of two long-term studies. AM J ORTnOD 1984;86:386-90. 17. Sadowsky C, BeGole EA. Long-term status of temporomandibular joint function and functional occlusion after orthodontic treatment. AM J ORTHOD1980;78:210-2. 18. Dibbers ]MH, vander Weele LT. Orthodontic treatment in relation to symptoms attributed 1o dysfunction of the temporomandibular joint. AM J ORI-rIODDEN'fOFACORTHOP1987;91:192205. 19. Wyatt WE. Preventing adverse effects on the temporomandibular joint through orthodontic treatment. AM J OR'I'HODDENTOFAC OR~OP 1987;91:493-9. 20. Elder JR, Tuenge RH. Cephalometric and histologic changes produced by extraoral high-pull traction to the maxilla in Macaca mulatta. AM J OR174OD1974;66:599-617. 21. Larson E, Ronnerman A. Mandibular dysfunction symptoms in orthodontically treated patients ten years after the completion of treatment. Eur J Orthod 1981;3:89-94. 22. Janson M, Hasund A. Functional problems in orthodontic patients out of retention. Eur J Orthod 1981;3:143-9. 23. Dahl BL, Krogstad BS, Ogaard B, Ecksherg T. Signs and symptoms of craniomandibular disorders in two groups of 19-yearold individuals, one treated orthodontically and the other not. Acta Odontol Scand 1988;46:89-93. 24. Pullinger AG, Hollander L, Solberg WK, Peterson A. Radiographic condylar position, TMJ patients and a screened control population. J Dent Res 1983;62:189. 25. Egermark-Eriksson I, Carlsson C, Ingervall B. Prevalence of mandibular dysfunction and orofacial parafunction in 7, 11, and 15 year old Swedish children. Eur J Orthod 1981;3:163-72. Reprint requests to: Dr. Anthony A. Gianelly Boston University Goldman School of Graduate Dentistry 100 E. Newton St. Boston, MA 02118