- Email: [email protected]
Long-term outcomes of nonsurgical treatment in nonreducing anteriorly displaced disk of the temporomandibular joint
Long-term outcomes of nonsurgical treatment in nonreducing anteriorly displaced disk of the temporomandibular joint Sadako Kai, DDS, PhD, a Hiroyuki Kai, DDS, a Osamu Tabata, DDS, b Yuji Shiratsuchi, DDS, PhD, c and Masamichi Ohishi, MD, DDS, PhD, d Fukuoka, Japan. KYUSHUUNIVERSITY
Objectives. The aim of this study was to evaluate long-term outcomes of nonsurgical treatment in patients with persistent anterior disk displacement without reduction of the temporomandibular joint. Study Design.Thirty-five patients were treated with occlusal splints, and 12 patients underwent additional occlusal treatments after splint treatment. These patients were evaluated clinically and radiographically. At least 2 years after the treatment, the 34 patients' symptoms were assessedwith the use of a questionnaire. Results. The mean maximal interincisal distance (MID) was 27.6 turn before treatment and 44.4 mm at the end of treatment (p < 0.001 ). Before the treatment, all 35 patients had complained of pain, and mild pain persisted in 9 patients at the end of treatment. Flattening of the condylar head and of the articular eminence increased in prevalence from 12.1% and 9.1%, respectively, before treatment to 54.5% and 51.5%, respectively, at the time of follow-up observation. At the time of the survey, the mean self-reported MID was 46.8 mm (p < 0.01). Conclusions. After the nonsurgical treatment, the clinical signs and symptoms improved significantly, although the prevalence of osteoarthrotic findings increased. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:258-67.) The findings of imaging of the temporomandibular joint (TMJ) suggest that in many patients with anterior displacement without reduction (ADw/oR), disk position after TMJ disk-repositioning surgery 1-3 or arthroscopic surgery 4-6 does not change, despite clinical improvements. The current consensus is that a successful treatment outcome may require only mobilization of the disk through procedures such as arthroscopic lysis of the adhesions and lavage of the joint, rather than the anatomic reduction of the displaced disk. 4,6,7 Surgery has been assumed to offer a greater likelihood of improvement than nonsurgical treatment. 8,9 The findings of recent long- and short-term evaluations, however, have suggested that TMJ surgery is not always a panacea; a high percentage of the patients continue to report persistent pain and restricted mandibular movement after surgery. 2,6,8-11 Nonsurgical treatment outcomes in patients with persistent ADw/oR have not been studied as closely as have surgical treatments. In 1990, we reported favorable outcomes for nonsurgical treatment in 35 subjects with ADw/oR. 12 At the end of the nonsurgical treatment, these patients showed remarkable improvement in pain aInstructor, First Department of Oral and Maxillofacial Surgery, Faculty of Dentistry. bInstructor, Departmentof Oral and MaxillofacialRadiology. CAssistant Professor, First Department of Oral and Maxillofacial Surgery, Faculty of Dentistry. dProfessor and Chairman, First Department of Oral and Maxillofacial Surgery, Faculty of Dentistry. Receivedfor publicationMay 5, 1997; returned for revisionAug. 8, 1997; acceptedfor publication Oct. 2, 1997. Copyright © 1998 by Mosby,Inc. 1079-2104/98/$5.00 + 0 7/12/86706 258
and maximal mouth opening in spite of the persistence of the displaced disk. In this study, we monitored the symptoms of these same subjects so that we might examine the stability of the outcomes. The conceptual foundations in the treatment of ADw/oR are discussed from a nonsurgical viewpoint. MFIHODS The subjects of this study were 35 female patients with ADw/oR. They were selected from consecutively treated patients who visited the First Department of Oral and Maxillofacial Surgery, Kyush u University, between 1987 and 1988. The patients' ages ranged from 15 to 63 years, with a mean of 37.3 years. All the subjects complained of restricted mandibular movement and unilateral pain located in the area of the TMJ, the masticatory muscles, or both. The mean duration after onset of the restricted mouth opening was 4.9 months (range, 2 weeks to 48 months), and no subject had undergone surgical treatment. Before the treatment, single contrast dual-space arthrotomography under fluoroscopy was used to confirm ADw/oR of the symptomatic side in 31 patients. Arthrographic examination was performed on the symptomatic TMJ in 2 patients and bilaterally in 29 patients. In the remaining four patients, a clinical diagnosis of ADw/oR was made on the basis of restricted mouth-opening, continuous mandibular deviation toward the painful side on mouthopening, and history of clicking and intermittent locking that ceased with a sudden and persistent limitation of mouth opening. Manual disk-repositioning attempts 13 were unsuccessful in all 35 patients.
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai et al. 259
Volume 85, Number 3
Treatment methods The treatment began with an occlusal stabilization splint. The splint was flat and fully covered the maxillary dental arch. Fabrication of the splint to centric relation was not performed. The maxillomandibular relationship of the splint was decided on the basis of the patients' soft biting after rest of the mandible without tooth contact. We ensured that the mandibular arch was not positioned more posteriorly than that at the intercuspal position without the splint to avoid an increase in the loading on the posterior attachment. The patients were instructed to wear their splints while sleeping. The splint was adjusted every three to four weeks in a search for a more comfortable and less painful craniomandibular relationship with a minimum increase in the occlusal vertical dimension. In several patients, the splint was remade because the patient reported increased pain while wearing the splint. Muscle relaxants or nonsteroidal antiinflammatory agents were prescribed for less than 2 weeks for eight patients who complained of severe pain. Neither mouthopening exercises nor other physical treatments were performed. The splint therapy was continued until the maximal interincisal distance (MID; active opening without any assistance) increased to 40 mm or greater and the pain was reduced. Occlusal equilibration was performed in four patients during splint therapy because of occlusal interferences at intercuspal position or at mandibular excursion. Because 12 patients complained of persistent pain when they removed the splint, they underwent localized prosthodontic treatment after the limited mouth-opening improved. Restoration of missing molar teeth was performed on four patients. The remaining patients had crowns or bridges with occlusal interferences or asymmetry in the vertical occlusal dimensions. These inadequate crowns and bridges were replaced with new ones to establish stable maxillomandibular relationships without or with reduced occlusal interference.
Clinical evaluation before and at the end of treatment The patients were evaluated before and at the end of the treatment with respect to MID, TMJ sounds, and pain in the TMJ and masticatory muscles.
Follow-up survey Questionnaire sheets were mailed to the 35 patients at least 2 years after treatment as a means of following up on their craniomandibular condition. All patients but one (whose address could not be traced) returned the completed questionnaires. The time between the end of the treatment and the questionnaire survey ranged from
25 to 42 months, with a mean of 32 months. The questions inquired as to the presence of TMJ sounds, and of any pain in the TMJ, cheek, or temporal region. The intensity of pain was classified by the patients into the following 4 categories: no pain, mild and of no concern, moderate, and severe with a need for analgesic medications. Each patient measured MID to the closest millimeter with a ruler, which was sent with instructions on its use. Other questions pertained to changes in the symptoms since the end of the treatment, current dietary restrictions, and the perceived need for further treatments for their symptoms aside from whether the patient was willing to visit our clinic.
Radiographic evaluation Standardized bilateral transcranial projections with mouth closed and maximal mouth-opening were obtained in 35 patients before the treatment and 33 patients after the treatment to identify osteoarthrotic changes in the lateral condyle and to estimate the condylar position at maximal mouth-opening in relation to the crest of the articular eminence. Arthrographic examination after the treatment was performed in six patients who were not reluctant to undergo this examination.
Statistical analysis With regard to nominal data, )~2 tests were used to test differences before treatment, after the treatment, and at follow-up. Paired Student t tests were used to compare pretreatment and posttreatment differences, and single Student t tests were used to test differences in MID between groups. We considered p values less than 0.05 statistically significant.
RESULTS Clinical symptoms The duration of the treatment--including splint therapy, prosthodontic treatment, and observation--ranged from 6 months to 24 months, with mean of 15.5 months. The mean duration of splint wear was 7.4 months. Table I summarizes the symptoms before the treatment, at the end of the treatment, and at the follow-up survey as assessed with the questionnaire. Before the treatment, all of the patients had complained of pain. Three patients presented with pain in the TMJ region, 5 with pain in the masticatory muscle region, and 27 with pain in both regions. At the end of the treatment, pain in the TMJ region persisted in one patient, masticatory muscle pain persisted in 6 patients, and pain at both regions persisted in 2 patients, but the intensity was reduced. At follow-up, 11 patients (32.4%) complained of pain in the TMJ region, cheek, or temporal region on the previously symptomatic side. The distinction between the
260
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai et al.
March 1998
Table h Symptoms at each stage Before treatment n=35 No. of patients with pain (%)
Site of pain (%) TMJ Masticatorymuscle TMJ and masticatorymuscles Severity of pain (%) Severe Moderate Mild Maximal interincisal distance (mm) Mean SD Minimum Maximum No. of patients with TMJ sounds (%)
End of treatment n=35
35 !100)
Follow-up n=34
9 (25.7)
*
11 (3214)
NS
3 5 27
1 6 2
10
0
0
18 7
2 7
3 8
44i4
46i8
3.1 36 51 23 (65.7)
4.2 40 61 16 (47.1)
27.6 6.2 14 38 9 (25.7)
*
L
Ir
*
I
NS
NS, p > 0.05 *p < 0.001 *0.001
Table II. Questionnaire results (n = 34) No. of patients (%) Overall change in symptoms after end of treatment Improved Unchanged Worsened Dietary restriction No dietary restriction Inconvenience only by tough and hard foods Necessity for further treatment No Asymptomatic Negligible mild symptoms Yes
19 (55.9) 13 (38.2) 2 (5.9) 27 (79.4) 7 (20.6) 31 (91.2) 10 (29.4) 21 (61.8) 3 (8.8)
muscle pain and the TMJ pain was not made in the follow-up survey. The pain was so mild as to be of no concern in eight subjects and was moderate in three other subjects. Mean MID, 27.6 mm before treatment, significantly increased to 44.4 mm at the end of the treatment (p < 0.001). In 34 patients (97.1%), MID was greater than 40 m m after the treatment. The duration until MID increased to more than 40 mm ranged from 1 month to 18 months, with a mean of 7.5 months. At the follow-up survey, the MID measured by the patients themselves ranged from 40 mm to 61 mm, with a mean of 46.8 mm. Paired Student t testing revealed that MID had
increased at the end of the treatment (p < 0.001) and at follow-up (p < 0.01). In terms of TMJ sounds, 9 patients (25.7%) had crepitation on the symptomatic side before treatment, compared with 23 patients (65.7%) at the end of treatment (p < 0.001). On the questionnaire, 16 patients (47.1%) reported some kind of TMJ sounds on the previously symptomatic side. Table II shows changes in the symptoms at the follow-up survey compared with the end of the treatment. Nineteen patients (55.9%) reported that their overall symptoms had improved; 13 (38.2%) reported that their symptoms were unchanged. Only two patients (5.9%) reported that their symptoms had worsened. Twentyseven patients (79.4%) reported that they had no dietary restrictions, and the remaining 7 reported that they were inconvenienced only by tough and hard foods. With respect to whether they felt the need for further treatments, 31 patients (91.2%) answered "no" because they were asymptomatic (10 patients) or only had negligible mild symptoms (21 patients). The remaining three patients, who responded that they felt a need for further treatment, visited us at our request. One of these patients showed decreased MID and pain pattern, suggesting that ADw/oR had occurred on the contralateral side. After renewed splint therapy for 5 months, the symptoms disappeared. Two of these patients complained of functional pain in the masseter muscles on the previously symptomatic side that appeared immediately after prosthodontic treatment received at other dental clinics during the follow-up period. We noted
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai et al. 261
Volume 85, Number 3
Fig. 1. Standardized lateral transcranial projections in a 51-year-old womn with anterior disk displacement without reduction. This patient had the most marked bone changes of our subjects. A, Before treatment. Patient presented with pain at the left TMJ and at the masseter muscle. MID was 28 mm. Marked osteoarthrotic changes were not observed. B, At the end of treatment (19 months after the first visit), the pain had been relieved and the MID had increased to 44 mm. Crepitations in the left TMJ were palpated. Flattening of the condylar head and the eminence is observed. The condyle translated beyond the crest of the articular eminence at m0uth-opening. C, Seventeen months after the end of the treatment (36 months after the first visit), the patient had no pain, and her MID was 48 ram. We noted no further aggressive degenerative changes, and the outline of the bones became distinct.
occlusal interferences in the newly established occlusion. The patients reported reduced symptoms after occlusal equilibration aimed at the elimination of the occlusal interferences.
Radiographic findings Osteoarthrotic findings were observed in 16 of 33 TMJs (48.5%) on the symptomatic side before treatment and in 24 TMJs (72.7%) at the end of the treatment (Table III). The prevalence was significantly higher at the end of the treatment than before the treatment
(p < 0.05). The most frequent findings in the condyle in the bilateral transcranial projection were erosion before treatment (42.4%) and flattening after treatment (54.5%). The erosion tended to change into flattening with reforming cortical bone (Fig. 1). In the lateral view of the articular eminence, flattening of the anterior part in the posterior slope was observed after treatment in 51.5% of patients. The outline of the posterior slope changed from a sigmoid curve to a straight line with decreased steepness of the posterior slope of the articular eminence. The frequency of eburnation of the poste-
262
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai et al.
March 1998
Fig 2. Standardized lateral transcranial projections in a 28-year-old woman with anterior disk displacement without reduction. Osteoarthrotic change was not marked in this patient. A, Before treatment, the patient presented with pain at the left TMJ. MID was 25 ram. B, At the end of treatment (19 months after the first visit), pain was relieved and MID was 45 ram. The condyle translated beyond the crest of the articular eminence at month-opening. We noted little change in the condyle or the eminence.
Table Ill. Bone changes in the symptomatic TMJ observed in lateral tanscranial projection (n = 33)
No. of TMJs with osteoarthrotic change (%) No. of findings (categories not mutually excnlsive) Condyle Erosion Flattening Sclerosis Osteophyte Posterior slope of eminence Flattening Eburnation
Before treatment (%)
End of treatment (%)
16 (48.5)*
24 (72.7)
14 (42.4)* 4 (12.1) ~ 1 (3.0) 1 (3.0)
5 (15.2) 18 (54.5) 1 (3.0) 6 (18.2)
3 (9.1) + 1 (3.0)
17 (51.5) 8 (24.2)
*0.01
rior slope also increased from 3.0% before treatment to 24.2% after treatment. Nine TMJs (27.3%) showed no morphologic change in transcranial projections after treatment (Fig. 2). Before treatment, no condyles on the symptomatic side translated anteriorly to the crest of the eminence at maximal mouth-opening. After treatment, 18 condy!es (54.5%) translated anteriorly to, and 9 condyles (27.3%) translated beneath, the crest of the eminence, as depicted on the transcranial view (Table IV). Table V summarizes the arthrographic findings. Before treatment, perforation of the disk-posterior
attachment component was observed in 8 TMJs (25.8%), intraarticular adhesions in 10 (32.3%). Mean M I D s in these 10 patients before the treatment, at the end of the treatment, and at the time of survey were 26.5, 43.4, and 46.1 mm, respectively. Mean MIDs in the remaining 21 patients were 28.1, 44.1, and 47.2 ram, respectively (Table VI). Student t testing showed no significant differences between the MID according to the presence or absence of adhesion at any stage. In the patients with intraarticular adhesions in pretreatment arthrography, the condyle at mouth-opening was positioned beneath or anterior to the crest of the eminence after treatment. Of the 29 patients who underwent bilateral arthrography, 34.5% presented ADw/oR on the asymptomatic contralateral side. All six of the patients who underwent posttreatment arthrography continued to show ADw/oR in the previously symptomatic TMJs. Two showed intraarticular adhesions in the upper joint cavity that had not been observed before treatment. Nevertheless, these two patients showed good clinical improvement and condylar translation beyond the crest of the articular eminence.
DISCUSSION Intraarticular adhesions are a common finding on direct arthroscopic inspection 14,15 in chronic ADw/oR. It has been suggested that intraarticular adhesion may contribute to the pathophysiology of painful hypomobility of the TMJ. 16,17 Murakami et al. 15 reported that although a weak, statistically significant negative corre-
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai etal. 263
Volume 85, Number 3
Table IV. Position of condyle at maximum mouth
Table V. Arthrographic findings
opening (n = 33)
Position
No. of TMJs (%) Before End of treatment treatment
Anterior to crest of articular eminence Beneath crest of articular eminence Posterior to crest of articular eminence
0 6 (t8.2) 27 (81.8)
18 (54.5) 9 (27.3) 6 (18.2)
lation was found between the degree of MID and an adhesion index, the adhesion might not be a significant barometer of joint hypomobility. Our results raise the question of whether the surgical removal of adhesions is essential for the improvement of condylar movement; mean MID after the nonsurgical treatment was greater than that reported after some arthroscopic surgeries. 6,7 In most of our patients, the condyles after the treatment translated to Or beyond the crest of the articular eminence. In addition, there were no statistically significant differences between mean MID in 10 patients with arthrographic findings indicating intraarticular adhesion and that in the remaining 21 patients without adhesions. Furthermore, there is the possibility of new intraarticular adhesions after surgery, as reported in arthrographic 1 and magnetic resonance imaging studies. 2 Finally, it must be considered that other factors (except intraarticular mechanical interferences such as anteriorly displaced disk or adhesions) might be responsible for the restricted condylar movements in chronic Adw/oR. It is widely accepted that pain and a reflex limitation of mouth-opening occur with synovitis. Synovitis accompanying ADw/oR may modify the mouth-opening limitation in addition to the limitation resulting from mechanical disturbance by the anteriorly displaced disk. This study and others 6,9,1s,19 have revealed that muscle pain, as well as TMJ pain, is frequent in ADw/oR. In an electromyographic study, Isberg et al. 2° observed abnormal activity of the masticatory muscles in patients with anterior disk displacement with reduction and continuous electromyographic activity in the masticatory muscle in some patients with ADw/oR. These findings suggest that a mechanical restriction of condylar movement can induce increased muscle activity, which may be relieved by improved condylar mobility, regardless of the type of treatment. In this study, however, masticatory muscle pain persisted in some patients even after the improvement of the condylar translation, whereas the TMJ pain was resolved in most of the patients. Holmlund et al. 11 made a long-term evaluation of diskectomy and pointed out that preoperative muscle soreness was more frequent in the group with the unsuccessful outcome than in that with the successful
No. of TMJs (%) Before treatment After treatment n=31 n=6
Symptomatic side ADw/oR Perforation Adhesion Asymptomatic contralateral side (n = 29*) ADw/oR
31 (100) 8 (25.8) 10 (32.3)
6 (100)
10 (34.5)
*Bilateral arthrography was performed in 29 patients.
Table Vl. MID in patients with and without arthro-
graphic findings of intra-articular adhesion before treatment (ram) Adhesion status
Before treatment
With adhesion (n = 10) Mean Minimum Maximum Without adhesion (n = 21) Mean SD Minimum Maximum
End of treatment Follow-up
26.5-] 7.1 14 NS 36 1
43.4-] 2.5 40 NS 47J
46.1 -] 4.6 40 NS 55J
28.1 6.2 15 38
44.1 2.9 36 49
47.2 4.3 42 60
/
/
/
NS, Difference not significant.
outcome. Thus, the persistence of muscle symptoms may be a more important factor affecting the prognosis of ADw/oR than the intraarticular adhesions. The range of mandibular motion is also restricted in some patients with normal arthrographic findings. 18,zl Furthermore, pain or hyperactivity of the closing muscles may functionally reduce mandibular movements in some patients even after an intraarticular mechanical obstruction is relieved. In chronic ADw/oR, persistent myogenous restriction of mandibular movement should not necessarily be interpreted as the result of the intraarticular disorders.
Nonsurgical treatment Contrary to earlier reports by others, 9,22 the nonsurgical treatment outcomes in our study were favorable. The long treatment period, lasting several months to more than 1 year, may account in part for the favorable results. In addition, the reduction in symptoms was maintained or progressed during the follow-up period in most of the patients. Some of this improvement was likely the result of a naturally occurring healing
264 Kai et aL
A
B
overloading~"~ C
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY March 1998
process, which in this study we were unable to assess for a lack of untreated controls. We hypothesize that the posterior attachment should gradually elongate during the period of subjective symptom improvement; posttreatment arthrography revealed persistent ADw/oR with improved condylar translation. Although various surgical techniques to treat ADw/oR have been applied after nonsurgical treatments have failed, 6,7-9 the nonsurgical treatment period in these studies was brief, lasting only a few months. 6,8,11 Our results suggest it is not possible to assess the success of nonsurgical treatment over such short periods. Although arthroscopic surgery usually produces rapid regression of subjective symptoms, 6,7 postoperative imaging demonstrates that the position of the disk does not change in most patients. 4-6 The rapid improvement of MID after arthroscopic surgery may be a result of rapid elongation of the posterior attachment during mandibular manipulation under anesthesia or of postoperative mouth-opening exercises, rather than the lysis of the fibrous adhesion. The nerve in the posterior attachment may be strongly stretched or injured by mandibular manipulation during surgery or surgical intervention itself under general anesthesia or TMJ local anesthesia. The rapid relief of TMJ pain may be attributed to such denervation of the posterior attachment.
Osteoarthrotic change
D
Fig. 3. TMJ structural changes in anterior disk displacement without reduction. A, Normal disk position at mouth-closing. B, Acute stage of anterior disk displacement without reduction. Condylar translation is restricted because posterior attachment prohibits anterior movement of disk. C, In chronic state, posterior attachment is elongated and mandibular translation improved. Posterior slope of the eminence and the condylar head are overloaded on condylar translation. Degenerative change occurs at these areas. D, Final stage of anterior disk displacement without reduction after improvement of condylar translation. Flattening of the condylar head and posterior slope of eminence are beneficial for condylar movement. Eburuatiou or sclerosis is structural reinforcement in response to increased loading. Bone surface resistance and compression force are in equilibrium.
Osteoarthrotic bone changes are frequently seen with disk displacement, 23-26 especially in Adw/oR. 27 In this study, 48.5% of the patients showed osteoarthrosis in the transcranial projection in the symptomatic condyle before the treatment, and the prevalence increased to 72.7% after the treatment. These findings are in accord with a report that bone changes are commonly observed in the TMJ with long-standing ADw/oR. 23 The increase in the prevalence of osteoarthrosis also reflects the increased prevalence of joint sounds after treatment observed in this study. The most common osteoarthrotic sign observed was erosion before treatment and flattening after treatment. These two changes were frequently transitional, and erosion tended to change into flattening with reforming of the bone cortex as described in the previous reports. 28,29 Flattening and ebumations of the posterior slope of the articular eminence were predominantly observed after treatment, a finding in agreement with previous reports that osteoarthrotic changes are not rare in the articular eminence 24'27,3°'31 and that the prevalent radiographic features are sclerosis and flattening of the eminence.27,3 °,31 It is proposed that osteoarthrosis occurs whenever articular remodeling does not maintain an equilibrium between form and function, 32 and overloading of the
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai et al. 265
Volume 85, Number 3
articular surface has been suggested to be a causative factor of osteoarthrosis. 33,34 The anterosuperior part of the condyle, and the posterior slope of the eminence, are thought to be functionally structured for loading because they show the thickest articular soft-tissue layer in the normal T M J Y We hypothesize that after the onset of ADw/oR, the displaced disk acts as a mechanical obstruction and repeatedly generates compressive and shearing forces toward the condyle and the posterior slope of the articular eminence when the patient attempts to move the condyle anteriorly (Fig. 3). This increased force may induce deformation of the disk, as well as degenerative changes in the articular cartilage and the subchondral bone. 'The degenerative changes may begin with softening of the articular cartilage 36 and be manifested as an erosion on radiography. Such a change may continue until the mechanical resistance of the bone surface and the force reach an equilibrium state, then stabilizes with the reformation of new cortical bone. Flattening of the condyle and the articular eminence is the typical feature of the equilibrium state. Eburnation and sclerosis are also considered to be a final-equilibrium state, with reinforcement of the structures against increased loading. In osteoarthrosis, the radiographic findings do n o t correlate well with the clinical symptoms. 25,37 Osteoarthrosis of the TMJ has a relatively good prognosis in terms of subjective symptoms 2529,37,38 In the literature, the terminal stage with no or reduced symptom severity is referred as burnout osteoarthrosis 25,28 or rearrangement of the TMJ. 29 Decreased steepness of the posterior slope of the articular eminence, which we frequently observed at the end of the treatment in this study, seems favorable for the condyle to translate anteriorly. Osteoarthrotic changes should therefore not be overestimated as an indication for surgical treatments.
Conceptual foundations of treatment for ADw/oR Natural regression of acute symptoms in ADw/oR has been reported. 39 Bilateral arthrography in this study revealed ADw/oR in the asymptomatic contralateral side in 10 (34.5%) of 29 patients. Isberg et al. 4° reported that 60% of patients with unilateral symptoms of ADw/oR had ADw/oR in the asymptomatic contralateral joints. Such ADw/oR on the asymptomatic side seemed to have developed earlier, preceding that on the symptomatic side. These findings raise the question of whether all patients with ADw/oR should receive nonsurgical treatment, such as the splint therapy implemented in this study. However, if the patients do not require treatment, no patients with chronic Adw/oR should complain of pain or limited mouth-opening.
tructuraland Functional~ iscrepancybetween / J and Occlusion )
Disk Displacement J
I
I
A
IStructuraland Functional
g0cclusal RehabilitationJ [///////////////////////////.~ ~OsteoarthroticChange:I
LTIDiMs,~renP~)CcYlbJestiWV./JJJl enen ~J./JJJ./././././/~. [ DiskDisplacement )I I
B
.c;
ta.°°°c'us'°.
~habilitation
J
1
3
Disk Displacement J
I
c Fig. 4. Compensation of discrepancy between TMJ and occlusion. A, If discrepancy is compensated for by disk displacement and a certain degree of osteoarthrotic change in TMJ, occlusal rehabilitation is not required. B, If discrepancy exceeds level of disk displacement and osteoarthrotic changes, occlusal treatment is necessary to eliminate residual symptoms. C, With increase in contribution from occlusal rehabilitation, degree of osteoarthrotic change will decrease. Some patients with chronic ADw/oR have continued pain despite long-standing ADw/oR and TMJ osteoarthrotic changes that have already stabilized. The persistence of the symptoms may depend on whether the causative factors that induced disk displacement have been compensated for. The cause of the internal derangement is still unclear and controversial. We hypothesize that a structural and functional discrepancy between the TMJ and occlusion is a major cause of the disk displacement (Fig. 4). Evidence of the occlusions importance is complete recapturing of the displaced disk, inducing an occlusal c h a n g e - - a posterior open bite, because it requires increase in the joint space where the displaced disk returns. 41 In other words, disk displacement may be induced by any occlusal condition that causes overloading of the TMJ. Under such occlusions, the disk receives increased friction from the articular surface and loses the necessary space to locate between the condyle and the fossa. Occlusal factors that functionally induce hyperactivity of masticatory muscles may
266
Kai et aL
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY March 1998
also increase loading. If the discrepancy is compensated for by displacement of the disk, the symptom should disappear as the posterior attachment elongates. When the discrepancy exceeds the level of compensation with disk displacement, further osteoarthrotic changes would follow to fill the remaining discrepancy. For patients presenting with these conditions, occlusal treatment should not be required. If the discrepancy is not compensated for by these structural changes, pain (especially masticatory muscle pain) will persist, with or without limited mandibular functions. To resolve the symptoms, some further structural changes are necessary (e.g., a permanent occlusal treatment to fill the remaining discrepancy). Our two patients with recurrence of symptoms after additional prosthodontic treatments performed at other clinics presented with features corroborating this hypothesis. In these patients, the occlusal changes after the additional treatment m a y have disrupted the equilibrium between TMJ function and its structure. Because the patients were sequentially selected, the study groups comprised patients presenting a variety of stages of anterior disk displacement without reduction. Therefore the study included subjects with many patterns of natural progression, ranging from those in w h o m the symptoms would resolve spontaneously to those in w h o m some occlusal treatment intervention would be considered. It is difficult to predict the outcome in an individual patient at the beginning of treatment in the early stage of ADw/oR. The major objectives o f wearing a splint are to reduce mechanical loading on the articular surfaces 42 and to address hyperactivity of the masticatory muscles. 43 Even in patients who do not need final occlusal treatments, appropriate splint therapy may shorten the interval until the equilibrium state is attained. Adequate prosthodontic treatment m a y reduce the degree of osteoarthrotic changes. Therefore we cannot conclude that patients with acute A D w / o R should not undergo splint therapy. In contrast, Lundh et al.39 raised a question as to the need for occlusal splint therapy; 16% of the patients in a nontreated control group and 40% of the patients treated with splints were worse at the end than at the beginning of observation. Their splints were fabricated and adjusted to the maximal contact in centric occlusion and centric relation. In the fabrication of splints in our study, adjustment to central relation was not performed, but attention was focused on avoiding the reduction in the joint space, especially in the posterior and superior portions. In addition, the splint was adjusted repeatedly, and restorative treatment or occlusal equilibration was p e r f o r m e d in the patients with persistent pain after removal of the splint. Differences in the techniques used in splint therapy and additional prosthodontic treat-
ments for persistent residual symptoms may account for the difference in symptomatic improvement between the patients studied by Lundh et al. 39 and our own. REFERENCES 1. Bronstein SL. Postsurgical TMJ arthrography. J Craniomandib Pract 1984;2:165-71. 2. Westesson P-L, Cohen JM, Tallents RH. Magnetic resonance imaging of temporomandibularjoint after surgical treatment of internal derangement. Oral Surg Oral Med Oral Pathol 1991; 71:407-11. 3. Conway WF, Hayes CW, Campbell RL, Laskin DM, Swanson KS. Temporomandibularjoint after meniscoplasty: appearance at MR imaging. Radiology 1991;i80:749-53. 4. Gabler MJ, Greene CS, Palacios E, Perry HT. Effect of arthroscopic temporomandibularjoint surgery on articular disk position. J Craniomandib Disord Facial Oral Pain 1989;3:191-202. 5. Moses JJ, Sartoris D, Glass R, Tanaka I", Poker I. The effect of arthroscopic surgical lysis and lavage of the superior joint space on TMJ disk position and mobility. J Oral Maxillofac Surg 1989;47:674-8. 6. Montgomery MT, Van Sickles JE, Harms SE. Success of temporomandibularjoint arthroscopy in disk displacement with and without reduction. Oral Surg Oral Med Oral Pathol 1991;71: 651-9. 7. Clark GT, Moody DG, Sanders B. Arthroscopic treatment of temporomandibularjoint locking, resulting from disk derangement: two-year results. J Oral Maxillofac Surg 1991;49:157-64. 8. Benson BJ, Keith DA. Patient response to surgical and nonsurgical treatment of the temporomandibular joint. J Oral Maxillofac Surg 1985;43:770-7. 9. Vallerand WE Hall MB. Improvement in myofascial pain and headaches following TMJ surgery: J Craniomandib Disord Facial Oral Pain 1991;5:197-204. 10. McCain JR Sanders B, Koslin MG, Quinn JD, Indresano AT. Temporomandibularjoint arthroscopy: a 6-year multicenter retrospective study of 4831 joints. J Oral Maxillofac Surg 1992;50:926-30. 11. HolmlundAB, Gynther G, Axelsson S. Diskectomy in treatment of internal derangement of the temporomandibularjoint: followup at 1, 3 and 5 years. Oral Surg Oral Med Oral Pathol 1993; 76:266-71. 12. Kai S, Kai H, Hamasaki A, ShiratsuchiY, Tashiro H, Tabata O. Clinical course of the conservative treatment in patients with persistent anterior disk displacement without reduction. J Jpn Soc TMJ 1990;2:34-46. 13. Farrar WB, McCarty WL. Clinical outline of temporomandibular joint: diagnosis and treatment. Montgomery, Ala.: Normandie Publications; 1982. p. 129. 14. Sanders B. Arthroscopic surgery of the temporomandibular joint: treatment of internal derangement with persistent closed lock. Oral Surg Oral Med Oral Pathol 1986;62:361-72. 15. Murakami K, Segami N. Intraarticular adhesions of the temporomandibularjoint: arthroscopic views and clinical perspectives. In: Clark G, Sanders B, Bertolami C, editors: Advances in diagnostic and surgical arthroscopy of the temporomandibular joint. Philadelphia: Saunders, 1993:15-21. 16. Kaminishi RM, Davis CL. Temporomandibularjoint arthroscopic observations of superior space adhesions. Oral Maxillofac Surg Clin North Am 1989;1:103-9. 17. Bewyer DC. Biomechanical and physiological process leading to internal derangement with adhesion. J Craniomandib Disord Facial Oral Pain 1989;3:44-9. 18. Seligman DA, Pullinger AG. TMJ derangements and osteoarthrosissubgroups differentedaccording to active range of mandibular opening. J Craniomandib Disord Facial Oral Pain 1988;2:35-40. 19. Linde C, Isacsson G. Clinical signs in patients with disk displacement versus patients with myogenic craniomandibulardis-
Kai et al. 267
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Volume 85, Number 3
20.
21.
22.
23.
24.
25.
26.
27.
28. 29. 30.
31.
32.
33.
orders. J Craniomandib Disord Facial Oral Pain 1990;4:197204. Isberg A, Widmalm SE, Ivarsson R. Clinical, radiographic, and eleetrographic study of patients with internal derangement of the temporo-mandibular joint. Am J Orthod 1985;88:453-60. Roberts CA, Tallents RH, Espeland MA, Handelman SL, Katzberg RW. Mandibular range of motion versus arthrographic diagnosis of the temporomandibular joint. Oral Surg Oral Med Oral Pathol 1985;60:244-51. Kirk WS, Calabrese DK. Clinical evaluation of physical therapy in the management of internal derangement of the temporomandibular joint. J Oral Maxillofac Surg 1989;47:113-9. Westesson P-L. Structural hard-tissue changes in temporomandibular joints with internal derangement. Oral Surg Oral Med Oral Pathol 1985;59:220-4. Anderson QN, Katzberg RW. Pathologic evaluation of disk dysfunction and osseous abnormalities of the temporomandibular joint. J Oral Maxillofac Surg 1985 ;43:947-51. Nikerson JW Jr. Boering G. Natural course of osteoarthrosis as it relates to internal derangement of the temporomandibular joint. Oral Maxillofac Surg Clin North Am 1989;1:27-45. Kai H, Kai S, Miyajima T, Tashiro H, Tabata O. Clinical observation of osteoarthrosis of the temporomandibular joint: relation to internal derangement. Jpn J Oral Maxillofac Surg 1991;37: 118-26. Ren Y-F, Isberg A, Westesson P-L. Steepness of the articular eminence in the temporomandibular joint. Oral Surg Oral Med Oral Pathol 1995;80:258-66. Toller PA. Osteoarthrosis of the mandibular condyle. Br Dent J 1973;134:223-31. Ogus H. The mandibular joint: internal rearrangement. Br J Oral Maxillofac Surg 1987;25:218-26. Hansson L-G, Hansson T, Petersson A. A comparison between clinical and radiologic findings in 259 temporomandibular joint patients. J Prosthet Dent 1983;50:89-94. Holumlund A, Hellsing G. Arthroscopy of the temporomandibular joint: a comparative study of arthroscopic and tomographic findings. Int J Oral Maxillofac Surg 1988;17:128-33. Moffett B. Definitions of temporomandibular joint derangement. In: Moffet BC, editor. Diagnosis of internal derangements of the temporomandibular joint. Vol. 1: Double-contrast arthrography and clinical correlations. Seattie: University of Washington, Continuing Dental Education, 1984:5-6. Stegenga B, de Bont LGM, Boering G. Osteoarthrosis as a cause
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
of craniomandibular pain and dysfunction: a unifying concept. J Oral Maxillofac Surg 1989;47:249-56. Hansson T, Oberg T, Carlsson GE, Kopp S. Thickness of the soft tissue layers and articular disk in the temporomandibular joint. Acta Odontol Scand 1977;35:77-83. Milam SB, Schmitz JE Molecular biology of temporomandibular joint disorders: proposed mechanisms of disease. J Oral Maxillofac Surg 1995;53:1448-54. Quinn JH. Arthroscopic and histologic evidence of chondromalacia in the temporomandibular joint. Oral Surg Oral Med Oral Pathol 1990;70:387-92. Greene CS, Markovic MA. Response to non surgical treatment of patients with positive radiographic findings in the temporomandibular joint. J Oral Surg 1976;34:692-7. de Leeuw R, Boering G, Stegenga B, de Bout LGM. Clinical signs of TMJ osteoarthrosis and internal derangement 30 years after nonsurgical treatment. J Orofacial Pain 1994;8:18-24. Lundh H, Westesson P-L, Eriksson L, Books SL. Temporomandibular joint disk displacement without reduction: treatment with flat occlusal splint versus no treatment. Oral Surg Oral Med Oral Pathol 1992;73:655-8. Isberg A. Stensttim B, Isacsson G. Frequency of bilateral temporomandibular joint disk displacement in patients with unilateral symptoms: a 5-year follow-up of the asymptomatic joints: a clinical and arthrotomographic study. Dentomaxillofac Radiol 1991;20:73-6. Kai S, Kai H, Tabata O, Tashiro H. The significance of posterior open bite after anterior repositioning splint therapy for anteriorly displaced disk of the temporomandibular joint. J Craniomandib Pract 1993; 11:146-52. Nizan DW. Intraarticular pressure in the functioning human temporomandibuIar joint and its alteration by uniform elevation of the occlusal plane. J Oral Maxillofac Surg 1994;52:671-9. Clark GT. Interocclusal appliance therapy. In: Mohl ND, Zarb GA, Carlsson GE, Rugh JD, editors: A textbook of occlusion. Chicago: Quintessence; 1988. p. 271-81.
Reprint requests: Sadako Kai, DDS, PhD First Department of Oral and Maxillofacial Surgery Faculty of Dentistry Kyushu University Maidashi 3-1-1, Higashi-ku Fukuoka 812, Japan
Objectives. The aim of this study was to evaluate long-term outcomes of nonsurgical treatment in patients with persistent anterior disk displacement without reduction of the temporomandibular joint. Study Design.Thirty-five patients were treated with occlusal splints, and 12 patients underwent additional occlusal treatments after splint treatment. These patients were evaluated clinically and radiographically. At least 2 years after the treatment, the 34 patients' symptoms were assessedwith the use of a questionnaire. Results. The mean maximal interincisal distance (MID) was 27.6 turn before treatment and 44.4 mm at the end of treatment (p < 0.001 ). Before the treatment, all 35 patients had complained of pain, and mild pain persisted in 9 patients at the end of treatment. Flattening of the condylar head and of the articular eminence increased in prevalence from 12.1% and 9.1%, respectively, before treatment to 54.5% and 51.5%, respectively, at the time of follow-up observation. At the time of the survey, the mean self-reported MID was 46.8 mm (p < 0.01). Conclusions. After the nonsurgical treatment, the clinical signs and symptoms improved significantly, although the prevalence of osteoarthrotic findings increased. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:258-67.) The findings of imaging of the temporomandibular joint (TMJ) suggest that in many patients with anterior displacement without reduction (ADw/oR), disk position after TMJ disk-repositioning surgery 1-3 or arthroscopic surgery 4-6 does not change, despite clinical improvements. The current consensus is that a successful treatment outcome may require only mobilization of the disk through procedures such as arthroscopic lysis of the adhesions and lavage of the joint, rather than the anatomic reduction of the displaced disk. 4,6,7 Surgery has been assumed to offer a greater likelihood of improvement than nonsurgical treatment. 8,9 The findings of recent long- and short-term evaluations, however, have suggested that TMJ surgery is not always a panacea; a high percentage of the patients continue to report persistent pain and restricted mandibular movement after surgery. 2,6,8-11 Nonsurgical treatment outcomes in patients with persistent ADw/oR have not been studied as closely as have surgical treatments. In 1990, we reported favorable outcomes for nonsurgical treatment in 35 subjects with ADw/oR. 12 At the end of the nonsurgical treatment, these patients showed remarkable improvement in pain aInstructor, First Department of Oral and Maxillofacial Surgery, Faculty of Dentistry. bInstructor, Departmentof Oral and MaxillofacialRadiology. CAssistant Professor, First Department of Oral and Maxillofacial Surgery, Faculty of Dentistry. dProfessor and Chairman, First Department of Oral and Maxillofacial Surgery, Faculty of Dentistry. Receivedfor publicationMay 5, 1997; returned for revisionAug. 8, 1997; acceptedfor publication Oct. 2, 1997. Copyright © 1998 by Mosby,Inc. 1079-2104/98/$5.00 + 0 7/12/86706 258
and maximal mouth opening in spite of the persistence of the displaced disk. In this study, we monitored the symptoms of these same subjects so that we might examine the stability of the outcomes. The conceptual foundations in the treatment of ADw/oR are discussed from a nonsurgical viewpoint. MFIHODS The subjects of this study were 35 female patients with ADw/oR. They were selected from consecutively treated patients who visited the First Department of Oral and Maxillofacial Surgery, Kyush u University, between 1987 and 1988. The patients' ages ranged from 15 to 63 years, with a mean of 37.3 years. All the subjects complained of restricted mandibular movement and unilateral pain located in the area of the TMJ, the masticatory muscles, or both. The mean duration after onset of the restricted mouth opening was 4.9 months (range, 2 weeks to 48 months), and no subject had undergone surgical treatment. Before the treatment, single contrast dual-space arthrotomography under fluoroscopy was used to confirm ADw/oR of the symptomatic side in 31 patients. Arthrographic examination was performed on the symptomatic TMJ in 2 patients and bilaterally in 29 patients. In the remaining four patients, a clinical diagnosis of ADw/oR was made on the basis of restricted mouth-opening, continuous mandibular deviation toward the painful side on mouthopening, and history of clicking and intermittent locking that ceased with a sudden and persistent limitation of mouth opening. Manual disk-repositioning attempts 13 were unsuccessful in all 35 patients.
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai et al. 259
Volume 85, Number 3
Treatment methods The treatment began with an occlusal stabilization splint. The splint was flat and fully covered the maxillary dental arch. Fabrication of the splint to centric relation was not performed. The maxillomandibular relationship of the splint was decided on the basis of the patients' soft biting after rest of the mandible without tooth contact. We ensured that the mandibular arch was not positioned more posteriorly than that at the intercuspal position without the splint to avoid an increase in the loading on the posterior attachment. The patients were instructed to wear their splints while sleeping. The splint was adjusted every three to four weeks in a search for a more comfortable and less painful craniomandibular relationship with a minimum increase in the occlusal vertical dimension. In several patients, the splint was remade because the patient reported increased pain while wearing the splint. Muscle relaxants or nonsteroidal antiinflammatory agents were prescribed for less than 2 weeks for eight patients who complained of severe pain. Neither mouthopening exercises nor other physical treatments were performed. The splint therapy was continued until the maximal interincisal distance (MID; active opening without any assistance) increased to 40 mm or greater and the pain was reduced. Occlusal equilibration was performed in four patients during splint therapy because of occlusal interferences at intercuspal position or at mandibular excursion. Because 12 patients complained of persistent pain when they removed the splint, they underwent localized prosthodontic treatment after the limited mouth-opening improved. Restoration of missing molar teeth was performed on four patients. The remaining patients had crowns or bridges with occlusal interferences or asymmetry in the vertical occlusal dimensions. These inadequate crowns and bridges were replaced with new ones to establish stable maxillomandibular relationships without or with reduced occlusal interference.
Clinical evaluation before and at the end of treatment The patients were evaluated before and at the end of the treatment with respect to MID, TMJ sounds, and pain in the TMJ and masticatory muscles.
Follow-up survey Questionnaire sheets were mailed to the 35 patients at least 2 years after treatment as a means of following up on their craniomandibular condition. All patients but one (whose address could not be traced) returned the completed questionnaires. The time between the end of the treatment and the questionnaire survey ranged from
25 to 42 months, with a mean of 32 months. The questions inquired as to the presence of TMJ sounds, and of any pain in the TMJ, cheek, or temporal region. The intensity of pain was classified by the patients into the following 4 categories: no pain, mild and of no concern, moderate, and severe with a need for analgesic medications. Each patient measured MID to the closest millimeter with a ruler, which was sent with instructions on its use. Other questions pertained to changes in the symptoms since the end of the treatment, current dietary restrictions, and the perceived need for further treatments for their symptoms aside from whether the patient was willing to visit our clinic.
Radiographic evaluation Standardized bilateral transcranial projections with mouth closed and maximal mouth-opening were obtained in 35 patients before the treatment and 33 patients after the treatment to identify osteoarthrotic changes in the lateral condyle and to estimate the condylar position at maximal mouth-opening in relation to the crest of the articular eminence. Arthrographic examination after the treatment was performed in six patients who were not reluctant to undergo this examination.
Statistical analysis With regard to nominal data, )~2 tests were used to test differences before treatment, after the treatment, and at follow-up. Paired Student t tests were used to compare pretreatment and posttreatment differences, and single Student t tests were used to test differences in MID between groups. We considered p values less than 0.05 statistically significant.
RESULTS Clinical symptoms The duration of the treatment--including splint therapy, prosthodontic treatment, and observation--ranged from 6 months to 24 months, with mean of 15.5 months. The mean duration of splint wear was 7.4 months. Table I summarizes the symptoms before the treatment, at the end of the treatment, and at the follow-up survey as assessed with the questionnaire. Before the treatment, all of the patients had complained of pain. Three patients presented with pain in the TMJ region, 5 with pain in the masticatory muscle region, and 27 with pain in both regions. At the end of the treatment, pain in the TMJ region persisted in one patient, masticatory muscle pain persisted in 6 patients, and pain at both regions persisted in 2 patients, but the intensity was reduced. At follow-up, 11 patients (32.4%) complained of pain in the TMJ region, cheek, or temporal region on the previously symptomatic side. The distinction between the
260
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai et al.
March 1998
Table h Symptoms at each stage Before treatment n=35 No. of patients with pain (%)
Site of pain (%) TMJ Masticatorymuscle TMJ and masticatorymuscles Severity of pain (%) Severe Moderate Mild Maximal interincisal distance (mm) Mean SD Minimum Maximum No. of patients with TMJ sounds (%)
End of treatment n=35
35 !100)
Follow-up n=34
9 (25.7)
*
11 (3214)
NS
3 5 27
1 6 2
10
0
0
18 7
2 7
3 8
44i4
46i8
3.1 36 51 23 (65.7)
4.2 40 61 16 (47.1)
27.6 6.2 14 38 9 (25.7)
*
L
Ir
*
I
NS
NS, p > 0.05 *p < 0.001 *0.001
Table II. Questionnaire results (n = 34) No. of patients (%) Overall change in symptoms after end of treatment Improved Unchanged Worsened Dietary restriction No dietary restriction Inconvenience only by tough and hard foods Necessity for further treatment No Asymptomatic Negligible mild symptoms Yes
19 (55.9) 13 (38.2) 2 (5.9) 27 (79.4) 7 (20.6) 31 (91.2) 10 (29.4) 21 (61.8) 3 (8.8)
muscle pain and the TMJ pain was not made in the follow-up survey. The pain was so mild as to be of no concern in eight subjects and was moderate in three other subjects. Mean MID, 27.6 mm before treatment, significantly increased to 44.4 mm at the end of the treatment (p < 0.001). In 34 patients (97.1%), MID was greater than 40 m m after the treatment. The duration until MID increased to more than 40 mm ranged from 1 month to 18 months, with a mean of 7.5 months. At the follow-up survey, the MID measured by the patients themselves ranged from 40 mm to 61 mm, with a mean of 46.8 mm. Paired Student t testing revealed that MID had
increased at the end of the treatment (p < 0.001) and at follow-up (p < 0.01). In terms of TMJ sounds, 9 patients (25.7%) had crepitation on the symptomatic side before treatment, compared with 23 patients (65.7%) at the end of treatment (p < 0.001). On the questionnaire, 16 patients (47.1%) reported some kind of TMJ sounds on the previously symptomatic side. Table II shows changes in the symptoms at the follow-up survey compared with the end of the treatment. Nineteen patients (55.9%) reported that their overall symptoms had improved; 13 (38.2%) reported that their symptoms were unchanged. Only two patients (5.9%) reported that their symptoms had worsened. Twentyseven patients (79.4%) reported that they had no dietary restrictions, and the remaining 7 reported that they were inconvenienced only by tough and hard foods. With respect to whether they felt the need for further treatments, 31 patients (91.2%) answered "no" because they were asymptomatic (10 patients) or only had negligible mild symptoms (21 patients). The remaining three patients, who responded that they felt a need for further treatment, visited us at our request. One of these patients showed decreased MID and pain pattern, suggesting that ADw/oR had occurred on the contralateral side. After renewed splint therapy for 5 months, the symptoms disappeared. Two of these patients complained of functional pain in the masseter muscles on the previously symptomatic side that appeared immediately after prosthodontic treatment received at other dental clinics during the follow-up period. We noted
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai et al. 261
Volume 85, Number 3
Fig. 1. Standardized lateral transcranial projections in a 51-year-old womn with anterior disk displacement without reduction. This patient had the most marked bone changes of our subjects. A, Before treatment. Patient presented with pain at the left TMJ and at the masseter muscle. MID was 28 mm. Marked osteoarthrotic changes were not observed. B, At the end of treatment (19 months after the first visit), the pain had been relieved and the MID had increased to 44 mm. Crepitations in the left TMJ were palpated. Flattening of the condylar head and the eminence is observed. The condyle translated beyond the crest of the articular eminence at m0uth-opening. C, Seventeen months after the end of the treatment (36 months after the first visit), the patient had no pain, and her MID was 48 ram. We noted no further aggressive degenerative changes, and the outline of the bones became distinct.
occlusal interferences in the newly established occlusion. The patients reported reduced symptoms after occlusal equilibration aimed at the elimination of the occlusal interferences.
Radiographic findings Osteoarthrotic findings were observed in 16 of 33 TMJs (48.5%) on the symptomatic side before treatment and in 24 TMJs (72.7%) at the end of the treatment (Table III). The prevalence was significantly higher at the end of the treatment than before the treatment
(p < 0.05). The most frequent findings in the condyle in the bilateral transcranial projection were erosion before treatment (42.4%) and flattening after treatment (54.5%). The erosion tended to change into flattening with reforming cortical bone (Fig. 1). In the lateral view of the articular eminence, flattening of the anterior part in the posterior slope was observed after treatment in 51.5% of patients. The outline of the posterior slope changed from a sigmoid curve to a straight line with decreased steepness of the posterior slope of the articular eminence. The frequency of eburnation of the poste-
262
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai et al.
March 1998
Fig 2. Standardized lateral transcranial projections in a 28-year-old woman with anterior disk displacement without reduction. Osteoarthrotic change was not marked in this patient. A, Before treatment, the patient presented with pain at the left TMJ. MID was 25 ram. B, At the end of treatment (19 months after the first visit), pain was relieved and MID was 45 ram. The condyle translated beyond the crest of the articular eminence at month-opening. We noted little change in the condyle or the eminence.
Table Ill. Bone changes in the symptomatic TMJ observed in lateral tanscranial projection (n = 33)
No. of TMJs with osteoarthrotic change (%) No. of findings (categories not mutually excnlsive) Condyle Erosion Flattening Sclerosis Osteophyte Posterior slope of eminence Flattening Eburnation
Before treatment (%)
End of treatment (%)
16 (48.5)*
24 (72.7)
14 (42.4)* 4 (12.1) ~ 1 (3.0) 1 (3.0)
5 (15.2) 18 (54.5) 1 (3.0) 6 (18.2)
3 (9.1) + 1 (3.0)
17 (51.5) 8 (24.2)
*0.01
rior slope also increased from 3.0% before treatment to 24.2% after treatment. Nine TMJs (27.3%) showed no morphologic change in transcranial projections after treatment (Fig. 2). Before treatment, no condyles on the symptomatic side translated anteriorly to the crest of the eminence at maximal mouth-opening. After treatment, 18 condy!es (54.5%) translated anteriorly to, and 9 condyles (27.3%) translated beneath, the crest of the eminence, as depicted on the transcranial view (Table IV). Table V summarizes the arthrographic findings. Before treatment, perforation of the disk-posterior
attachment component was observed in 8 TMJs (25.8%), intraarticular adhesions in 10 (32.3%). Mean M I D s in these 10 patients before the treatment, at the end of the treatment, and at the time of survey were 26.5, 43.4, and 46.1 mm, respectively. Mean MIDs in the remaining 21 patients were 28.1, 44.1, and 47.2 ram, respectively (Table VI). Student t testing showed no significant differences between the MID according to the presence or absence of adhesion at any stage. In the patients with intraarticular adhesions in pretreatment arthrography, the condyle at mouth-opening was positioned beneath or anterior to the crest of the eminence after treatment. Of the 29 patients who underwent bilateral arthrography, 34.5% presented ADw/oR on the asymptomatic contralateral side. All six of the patients who underwent posttreatment arthrography continued to show ADw/oR in the previously symptomatic TMJs. Two showed intraarticular adhesions in the upper joint cavity that had not been observed before treatment. Nevertheless, these two patients showed good clinical improvement and condylar translation beyond the crest of the articular eminence.
DISCUSSION Intraarticular adhesions are a common finding on direct arthroscopic inspection 14,15 in chronic ADw/oR. It has been suggested that intraarticular adhesion may contribute to the pathophysiology of painful hypomobility of the TMJ. 16,17 Murakami et al. 15 reported that although a weak, statistically significant negative corre-
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai etal. 263
Volume 85, Number 3
Table IV. Position of condyle at maximum mouth
Table V. Arthrographic findings
opening (n = 33)
Position
No. of TMJs (%) Before End of treatment treatment
Anterior to crest of articular eminence Beneath crest of articular eminence Posterior to crest of articular eminence
0 6 (t8.2) 27 (81.8)
18 (54.5) 9 (27.3) 6 (18.2)
lation was found between the degree of MID and an adhesion index, the adhesion might not be a significant barometer of joint hypomobility. Our results raise the question of whether the surgical removal of adhesions is essential for the improvement of condylar movement; mean MID after the nonsurgical treatment was greater than that reported after some arthroscopic surgeries. 6,7 In most of our patients, the condyles after the treatment translated to Or beyond the crest of the articular eminence. In addition, there were no statistically significant differences between mean MID in 10 patients with arthrographic findings indicating intraarticular adhesion and that in the remaining 21 patients without adhesions. Furthermore, there is the possibility of new intraarticular adhesions after surgery, as reported in arthrographic 1 and magnetic resonance imaging studies. 2 Finally, it must be considered that other factors (except intraarticular mechanical interferences such as anteriorly displaced disk or adhesions) might be responsible for the restricted condylar movements in chronic Adw/oR. It is widely accepted that pain and a reflex limitation of mouth-opening occur with synovitis. Synovitis accompanying ADw/oR may modify the mouth-opening limitation in addition to the limitation resulting from mechanical disturbance by the anteriorly displaced disk. This study and others 6,9,1s,19 have revealed that muscle pain, as well as TMJ pain, is frequent in ADw/oR. In an electromyographic study, Isberg et al. 2° observed abnormal activity of the masticatory muscles in patients with anterior disk displacement with reduction and continuous electromyographic activity in the masticatory muscle in some patients with ADw/oR. These findings suggest that a mechanical restriction of condylar movement can induce increased muscle activity, which may be relieved by improved condylar mobility, regardless of the type of treatment. In this study, however, masticatory muscle pain persisted in some patients even after the improvement of the condylar translation, whereas the TMJ pain was resolved in most of the patients. Holmlund et al. 11 made a long-term evaluation of diskectomy and pointed out that preoperative muscle soreness was more frequent in the group with the unsuccessful outcome than in that with the successful
No. of TMJs (%) Before treatment After treatment n=31 n=6
Symptomatic side ADw/oR Perforation Adhesion Asymptomatic contralateral side (n = 29*) ADw/oR
31 (100) 8 (25.8) 10 (32.3)
6 (100)
10 (34.5)
*Bilateral arthrography was performed in 29 patients.
Table Vl. MID in patients with and without arthro-
graphic findings of intra-articular adhesion before treatment (ram) Adhesion status
Before treatment
With adhesion (n = 10) Mean Minimum Maximum Without adhesion (n = 21) Mean SD Minimum Maximum
End of treatment Follow-up
26.5-] 7.1 14 NS 36 1
43.4-] 2.5 40 NS 47J
46.1 -] 4.6 40 NS 55J
28.1 6.2 15 38
44.1 2.9 36 49
47.2 4.3 42 60
/
/
/
NS, Difference not significant.
outcome. Thus, the persistence of muscle symptoms may be a more important factor affecting the prognosis of ADw/oR than the intraarticular adhesions. The range of mandibular motion is also restricted in some patients with normal arthrographic findings. 18,zl Furthermore, pain or hyperactivity of the closing muscles may functionally reduce mandibular movements in some patients even after an intraarticular mechanical obstruction is relieved. In chronic ADw/oR, persistent myogenous restriction of mandibular movement should not necessarily be interpreted as the result of the intraarticular disorders.
Nonsurgical treatment Contrary to earlier reports by others, 9,22 the nonsurgical treatment outcomes in our study were favorable. The long treatment period, lasting several months to more than 1 year, may account in part for the favorable results. In addition, the reduction in symptoms was maintained or progressed during the follow-up period in most of the patients. Some of this improvement was likely the result of a naturally occurring healing
264 Kai et aL
A
B
overloading~"~ C
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY March 1998
process, which in this study we were unable to assess for a lack of untreated controls. We hypothesize that the posterior attachment should gradually elongate during the period of subjective symptom improvement; posttreatment arthrography revealed persistent ADw/oR with improved condylar translation. Although various surgical techniques to treat ADw/oR have been applied after nonsurgical treatments have failed, 6,7-9 the nonsurgical treatment period in these studies was brief, lasting only a few months. 6,8,11 Our results suggest it is not possible to assess the success of nonsurgical treatment over such short periods. Although arthroscopic surgery usually produces rapid regression of subjective symptoms, 6,7 postoperative imaging demonstrates that the position of the disk does not change in most patients. 4-6 The rapid improvement of MID after arthroscopic surgery may be a result of rapid elongation of the posterior attachment during mandibular manipulation under anesthesia or of postoperative mouth-opening exercises, rather than the lysis of the fibrous adhesion. The nerve in the posterior attachment may be strongly stretched or injured by mandibular manipulation during surgery or surgical intervention itself under general anesthesia or TMJ local anesthesia. The rapid relief of TMJ pain may be attributed to such denervation of the posterior attachment.
Osteoarthrotic change
D
Fig. 3. TMJ structural changes in anterior disk displacement without reduction. A, Normal disk position at mouth-closing. B, Acute stage of anterior disk displacement without reduction. Condylar translation is restricted because posterior attachment prohibits anterior movement of disk. C, In chronic state, posterior attachment is elongated and mandibular translation improved. Posterior slope of the eminence and the condylar head are overloaded on condylar translation. Degenerative change occurs at these areas. D, Final stage of anterior disk displacement without reduction after improvement of condylar translation. Flattening of the condylar head and posterior slope of eminence are beneficial for condylar movement. Eburuatiou or sclerosis is structural reinforcement in response to increased loading. Bone surface resistance and compression force are in equilibrium.
Osteoarthrotic bone changes are frequently seen with disk displacement, 23-26 especially in Adw/oR. 27 In this study, 48.5% of the patients showed osteoarthrosis in the transcranial projection in the symptomatic condyle before the treatment, and the prevalence increased to 72.7% after the treatment. These findings are in accord with a report that bone changes are commonly observed in the TMJ with long-standing ADw/oR. 23 The increase in the prevalence of osteoarthrosis also reflects the increased prevalence of joint sounds after treatment observed in this study. The most common osteoarthrotic sign observed was erosion before treatment and flattening after treatment. These two changes were frequently transitional, and erosion tended to change into flattening with reforming of the bone cortex as described in the previous reports. 28,29 Flattening and ebumations of the posterior slope of the articular eminence were predominantly observed after treatment, a finding in agreement with previous reports that osteoarthrotic changes are not rare in the articular eminence 24'27,3°'31 and that the prevalent radiographic features are sclerosis and flattening of the eminence.27,3 °,31 It is proposed that osteoarthrosis occurs whenever articular remodeling does not maintain an equilibrium between form and function, 32 and overloading of the
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Kai et al. 265
Volume 85, Number 3
articular surface has been suggested to be a causative factor of osteoarthrosis. 33,34 The anterosuperior part of the condyle, and the posterior slope of the eminence, are thought to be functionally structured for loading because they show the thickest articular soft-tissue layer in the normal T M J Y We hypothesize that after the onset of ADw/oR, the displaced disk acts as a mechanical obstruction and repeatedly generates compressive and shearing forces toward the condyle and the posterior slope of the articular eminence when the patient attempts to move the condyle anteriorly (Fig. 3). This increased force may induce deformation of the disk, as well as degenerative changes in the articular cartilage and the subchondral bone. 'The degenerative changes may begin with softening of the articular cartilage 36 and be manifested as an erosion on radiography. Such a change may continue until the mechanical resistance of the bone surface and the force reach an equilibrium state, then stabilizes with the reformation of new cortical bone. Flattening of the condyle and the articular eminence is the typical feature of the equilibrium state. Eburnation and sclerosis are also considered to be a final-equilibrium state, with reinforcement of the structures against increased loading. In osteoarthrosis, the radiographic findings do n o t correlate well with the clinical symptoms. 25,37 Osteoarthrosis of the TMJ has a relatively good prognosis in terms of subjective symptoms 2529,37,38 In the literature, the terminal stage with no or reduced symptom severity is referred as burnout osteoarthrosis 25,28 or rearrangement of the TMJ. 29 Decreased steepness of the posterior slope of the articular eminence, which we frequently observed at the end of the treatment in this study, seems favorable for the condyle to translate anteriorly. Osteoarthrotic changes should therefore not be overestimated as an indication for surgical treatments.
Conceptual foundations of treatment for ADw/oR Natural regression of acute symptoms in ADw/oR has been reported. 39 Bilateral arthrography in this study revealed ADw/oR in the asymptomatic contralateral side in 10 (34.5%) of 29 patients. Isberg et al. 4° reported that 60% of patients with unilateral symptoms of ADw/oR had ADw/oR in the asymptomatic contralateral joints. Such ADw/oR on the asymptomatic side seemed to have developed earlier, preceding that on the symptomatic side. These findings raise the question of whether all patients with ADw/oR should receive nonsurgical treatment, such as the splint therapy implemented in this study. However, if the patients do not require treatment, no patients with chronic Adw/oR should complain of pain or limited mouth-opening.
tructuraland Functional~ iscrepancybetween / J and Occlusion )
Disk Displacement J
I
I
A
IStructuraland Functional
g0cclusal RehabilitationJ [///////////////////////////.~ ~OsteoarthroticChange:I
LTIDiMs,~renP~)CcYlbJestiWV./JJJl enen ~J./JJJ./././././/~. [ DiskDisplacement )I I
B
.c;
ta.°°°c'us'°.
~habilitation
J
1
3
Disk Displacement J
I
c Fig. 4. Compensation of discrepancy between TMJ and occlusion. A, If discrepancy is compensated for by disk displacement and a certain degree of osteoarthrotic change in TMJ, occlusal rehabilitation is not required. B, If discrepancy exceeds level of disk displacement and osteoarthrotic changes, occlusal treatment is necessary to eliminate residual symptoms. C, With increase in contribution from occlusal rehabilitation, degree of osteoarthrotic change will decrease. Some patients with chronic ADw/oR have continued pain despite long-standing ADw/oR and TMJ osteoarthrotic changes that have already stabilized. The persistence of the symptoms may depend on whether the causative factors that induced disk displacement have been compensated for. The cause of the internal derangement is still unclear and controversial. We hypothesize that a structural and functional discrepancy between the TMJ and occlusion is a major cause of the disk displacement (Fig. 4). Evidence of the occlusions importance is complete recapturing of the displaced disk, inducing an occlusal c h a n g e - - a posterior open bite, because it requires increase in the joint space where the displaced disk returns. 41 In other words, disk displacement may be induced by any occlusal condition that causes overloading of the TMJ. Under such occlusions, the disk receives increased friction from the articular surface and loses the necessary space to locate between the condyle and the fossa. Occlusal factors that functionally induce hyperactivity of masticatory muscles may
266
Kai et aL
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY March 1998
also increase loading. If the discrepancy is compensated for by displacement of the disk, the symptom should disappear as the posterior attachment elongates. When the discrepancy exceeds the level of compensation with disk displacement, further osteoarthrotic changes would follow to fill the remaining discrepancy. For patients presenting with these conditions, occlusal treatment should not be required. If the discrepancy is not compensated for by these structural changes, pain (especially masticatory muscle pain) will persist, with or without limited mandibular functions. To resolve the symptoms, some further structural changes are necessary (e.g., a permanent occlusal treatment to fill the remaining discrepancy). Our two patients with recurrence of symptoms after additional prosthodontic treatments performed at other clinics presented with features corroborating this hypothesis. In these patients, the occlusal changes after the additional treatment m a y have disrupted the equilibrium between TMJ function and its structure. Because the patients were sequentially selected, the study groups comprised patients presenting a variety of stages of anterior disk displacement without reduction. Therefore the study included subjects with many patterns of natural progression, ranging from those in w h o m the symptoms would resolve spontaneously to those in w h o m some occlusal treatment intervention would be considered. It is difficult to predict the outcome in an individual patient at the beginning of treatment in the early stage of ADw/oR. The major objectives o f wearing a splint are to reduce mechanical loading on the articular surfaces 42 and to address hyperactivity of the masticatory muscles. 43 Even in patients who do not need final occlusal treatments, appropriate splint therapy may shorten the interval until the equilibrium state is attained. Adequate prosthodontic treatment m a y reduce the degree of osteoarthrotic changes. Therefore we cannot conclude that patients with acute A D w / o R should not undergo splint therapy. In contrast, Lundh et al.39 raised a question as to the need for occlusal splint therapy; 16% of the patients in a nontreated control group and 40% of the patients treated with splints were worse at the end than at the beginning of observation. Their splints were fabricated and adjusted to the maximal contact in centric occlusion and centric relation. In the fabrication of splints in our study, adjustment to central relation was not performed, but attention was focused on avoiding the reduction in the joint space, especially in the posterior and superior portions. In addition, the splint was adjusted repeatedly, and restorative treatment or occlusal equilibration was p e r f o r m e d in the patients with persistent pain after removal of the splint. Differences in the techniques used in splint therapy and additional prosthodontic treat-
ments for persistent residual symptoms may account for the difference in symptomatic improvement between the patients studied by Lundh et al. 39 and our own. REFERENCES 1. Bronstein SL. Postsurgical TMJ arthrography. J Craniomandib Pract 1984;2:165-71. 2. Westesson P-L, Cohen JM, Tallents RH. Magnetic resonance imaging of temporomandibularjoint after surgical treatment of internal derangement. Oral Surg Oral Med Oral Pathol 1991; 71:407-11. 3. Conway WF, Hayes CW, Campbell RL, Laskin DM, Swanson KS. Temporomandibularjoint after meniscoplasty: appearance at MR imaging. Radiology 1991;i80:749-53. 4. Gabler MJ, Greene CS, Palacios E, Perry HT. Effect of arthroscopic temporomandibularjoint surgery on articular disk position. J Craniomandib Disord Facial Oral Pain 1989;3:191-202. 5. Moses JJ, Sartoris D, Glass R, Tanaka I", Poker I. The effect of arthroscopic surgical lysis and lavage of the superior joint space on TMJ disk position and mobility. J Oral Maxillofac Surg 1989;47:674-8. 6. Montgomery MT, Van Sickles JE, Harms SE. Success of temporomandibularjoint arthroscopy in disk displacement with and without reduction. Oral Surg Oral Med Oral Pathol 1991;71: 651-9. 7. Clark GT, Moody DG, Sanders B. Arthroscopic treatment of temporomandibularjoint locking, resulting from disk derangement: two-year results. J Oral Maxillofac Surg 1991;49:157-64. 8. Benson BJ, Keith DA. Patient response to surgical and nonsurgical treatment of the temporomandibular joint. J Oral Maxillofac Surg 1985;43:770-7. 9. Vallerand WE Hall MB. Improvement in myofascial pain and headaches following TMJ surgery: J Craniomandib Disord Facial Oral Pain 1991;5:197-204. 10. McCain JR Sanders B, Koslin MG, Quinn JD, Indresano AT. Temporomandibularjoint arthroscopy: a 6-year multicenter retrospective study of 4831 joints. J Oral Maxillofac Surg 1992;50:926-30. 11. HolmlundAB, Gynther G, Axelsson S. Diskectomy in treatment of internal derangement of the temporomandibularjoint: followup at 1, 3 and 5 years. Oral Surg Oral Med Oral Pathol 1993; 76:266-71. 12. Kai S, Kai H, Hamasaki A, ShiratsuchiY, Tashiro H, Tabata O. Clinical course of the conservative treatment in patients with persistent anterior disk displacement without reduction. J Jpn Soc TMJ 1990;2:34-46. 13. Farrar WB, McCarty WL. Clinical outline of temporomandibular joint: diagnosis and treatment. Montgomery, Ala.: Normandie Publications; 1982. p. 129. 14. Sanders B. Arthroscopic surgery of the temporomandibular joint: treatment of internal derangement with persistent closed lock. Oral Surg Oral Med Oral Pathol 1986;62:361-72. 15. Murakami K, Segami N. Intraarticular adhesions of the temporomandibularjoint: arthroscopic views and clinical perspectives. In: Clark G, Sanders B, Bertolami C, editors: Advances in diagnostic and surgical arthroscopy of the temporomandibular joint. Philadelphia: Saunders, 1993:15-21. 16. Kaminishi RM, Davis CL. Temporomandibularjoint arthroscopic observations of superior space adhesions. Oral Maxillofac Surg Clin North Am 1989;1:103-9. 17. Bewyer DC. Biomechanical and physiological process leading to internal derangement with adhesion. J Craniomandib Disord Facial Oral Pain 1989;3:44-9. 18. Seligman DA, Pullinger AG. TMJ derangements and osteoarthrosissubgroups differentedaccording to active range of mandibular opening. J Craniomandib Disord Facial Oral Pain 1988;2:35-40. 19. Linde C, Isacsson G. Clinical signs in patients with disk displacement versus patients with myogenic craniomandibulardis-
Kai et al. 267
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Volume 85, Number 3
20.
21.
22.
23.
24.
25.
26.
27.
28. 29. 30.
31.
32.
33.
orders. J Craniomandib Disord Facial Oral Pain 1990;4:197204. Isberg A, Widmalm SE, Ivarsson R. Clinical, radiographic, and eleetrographic study of patients with internal derangement of the temporo-mandibular joint. Am J Orthod 1985;88:453-60. Roberts CA, Tallents RH, Espeland MA, Handelman SL, Katzberg RW. Mandibular range of motion versus arthrographic diagnosis of the temporomandibular joint. Oral Surg Oral Med Oral Pathol 1985;60:244-51. Kirk WS, Calabrese DK. Clinical evaluation of physical therapy in the management of internal derangement of the temporomandibular joint. J Oral Maxillofac Surg 1989;47:113-9. Westesson P-L. Structural hard-tissue changes in temporomandibular joints with internal derangement. Oral Surg Oral Med Oral Pathol 1985;59:220-4. Anderson QN, Katzberg RW. Pathologic evaluation of disk dysfunction and osseous abnormalities of the temporomandibular joint. J Oral Maxillofac Surg 1985 ;43:947-51. Nikerson JW Jr. Boering G. Natural course of osteoarthrosis as it relates to internal derangement of the temporomandibular joint. Oral Maxillofac Surg Clin North Am 1989;1:27-45. Kai H, Kai S, Miyajima T, Tashiro H, Tabata O. Clinical observation of osteoarthrosis of the temporomandibular joint: relation to internal derangement. Jpn J Oral Maxillofac Surg 1991;37: 118-26. Ren Y-F, Isberg A, Westesson P-L. Steepness of the articular eminence in the temporomandibular joint. Oral Surg Oral Med Oral Pathol 1995;80:258-66. Toller PA. Osteoarthrosis of the mandibular condyle. Br Dent J 1973;134:223-31. Ogus H. The mandibular joint: internal rearrangement. Br J Oral Maxillofac Surg 1987;25:218-26. Hansson L-G, Hansson T, Petersson A. A comparison between clinical and radiologic findings in 259 temporomandibular joint patients. J Prosthet Dent 1983;50:89-94. Holumlund A, Hellsing G. Arthroscopy of the temporomandibular joint: a comparative study of arthroscopic and tomographic findings. Int J Oral Maxillofac Surg 1988;17:128-33. Moffett B. Definitions of temporomandibular joint derangement. In: Moffet BC, editor. Diagnosis of internal derangements of the temporomandibular joint. Vol. 1: Double-contrast arthrography and clinical correlations. Seattie: University of Washington, Continuing Dental Education, 1984:5-6. Stegenga B, de Bont LGM, Boering G. Osteoarthrosis as a cause
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
of craniomandibular pain and dysfunction: a unifying concept. J Oral Maxillofac Surg 1989;47:249-56. Hansson T, Oberg T, Carlsson GE, Kopp S. Thickness of the soft tissue layers and articular disk in the temporomandibular joint. Acta Odontol Scand 1977;35:77-83. Milam SB, Schmitz JE Molecular biology of temporomandibular joint disorders: proposed mechanisms of disease. J Oral Maxillofac Surg 1995;53:1448-54. Quinn JH. Arthroscopic and histologic evidence of chondromalacia in the temporomandibular joint. Oral Surg Oral Med Oral Pathol 1990;70:387-92. Greene CS, Markovic MA. Response to non surgical treatment of patients with positive radiographic findings in the temporomandibular joint. J Oral Surg 1976;34:692-7. de Leeuw R, Boering G, Stegenga B, de Bout LGM. Clinical signs of TMJ osteoarthrosis and internal derangement 30 years after nonsurgical treatment. J Orofacial Pain 1994;8:18-24. Lundh H, Westesson P-L, Eriksson L, Books SL. Temporomandibular joint disk displacement without reduction: treatment with flat occlusal splint versus no treatment. Oral Surg Oral Med Oral Pathol 1992;73:655-8. Isberg A. Stensttim B, Isacsson G. Frequency of bilateral temporomandibular joint disk displacement in patients with unilateral symptoms: a 5-year follow-up of the asymptomatic joints: a clinical and arthrotomographic study. Dentomaxillofac Radiol 1991;20:73-6. Kai S, Kai H, Tabata O, Tashiro H. The significance of posterior open bite after anterior repositioning splint therapy for anteriorly displaced disk of the temporomandibular joint. J Craniomandib Pract 1993; 11:146-52. Nizan DW. Intraarticular pressure in the functioning human temporomandibuIar joint and its alteration by uniform elevation of the occlusal plane. J Oral Maxillofac Surg 1994;52:671-9. Clark GT. Interocclusal appliance therapy. In: Mohl ND, Zarb GA, Carlsson GE, Rugh JD, editors: A textbook of occlusion. Chicago: Quintessence; 1988. p. 271-81.
Reprint requests: Sadako Kai, DDS, PhD First Department of Oral and Maxillofacial Surgery Faculty of Dentistry Kyushu University Maidashi 3-1-1, Higashi-ku Fukuoka 812, Japan