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Anterior condylar remodeling observed in stabilization splint therapy for temporomandibular joint osteoarthritis
Vol. 118 No. 3 September 2014
Anterior condylar remodeling observed in stabilization splint therapy for temporomandibular joint osteoarthritis Soo-Min Ok, PhD,a Jihyun Lee,b Yong-Il Kim, PhD,b Jae-Yeol Lee, PhD,c Ki Beom Kim, DDS, MSD, PhD,d and Sung-Hee Jeong, PhDa Pusan National University, Busan, South Korea; and Saint Louis University, St Louis, MO, USA
Objective. To comparatively evaluate condylar surface bone formation and cortical thickening in patients with temporomandibular joint osteoarthritis, with or without stabilization splint (SS) therapy. Study Design. This retrospective study of 57 OA patients included 18 patients who had undergone SS therapy (SS group), compared with 39 patients that had not received SS therapy (non-SS group). To evaluate osseous changes on the condylar bone formation and cortical thickening, pre- and post-treatment cone beam computed tomography images of each patient were superimposed using voxel registration. Results. The SS group exhibited a higher ratio of bone formation in the anterior division of the condyle; the non-SS group exhibited mostly no change. The SS group was found to have higher frequencies of cortical thickening in the anteromedial, anterior-intermediate, anterolateral, posteromedial, and posterior-intermediate sections than the non-SS group. Conclusions. SS therapy in temporomandibular joint osteoarthritis induced favorable bone remodeling in the anterior division of the condylar head. (Oral Surg Oral Med Oral Pathol Oral Radiol 2014;118:363-370)
Signs and symptoms of temporomandibular joint (TMJ) arthralgia often are attributable to TMJ osteoarthritis (OA), a severe form of TMJ disorder marked by degenerative osseous changes accompanied by secondary inflammation.1 The main cause of TMJ OA is excessive overloading of the articulation surpassing physiologic tolerance. This overload of the joint leads to the degenerative change of the articular surface of the mandibular condyle and subsequent cortical destruction.2 Resultant gross morphologic changes, such as deviation in form, disk displacement, adhesions, and osteoarthritic processes, can occur with or without the experience of pain or dysfunction.3 As the conservative approach to TMJ OA, the therapeutic protocol of physiotherapy, medication, occlusal appliance therapy, and intra-articular injection is well established.4-6 Among these, the stabilization splint (SS) has been clinically confirmed to effectively protect the TMJ against unintentional overloading and relieve excessive muscular tension while preventing sprain in the mandibular condyle in the case of bruxism.2 Kuttila et al.7 reported that the use of SS improved the clinical a Department of Oral Medicine, School of Dentistry, Pusan National University, Busan, South Korea. b Department of Orthodontics, Pusan National University, Biomedical research institute, Pusan National University Hospital, Busan, South Korea. c Department of Oral & Maxillofacial Surgery, Pusan National University Hospital, Busan, South Korea. d Department of Orthodontics, Center for Advanced Dental Education, Saint Louis University, St Louis, MO, USA. Received for publication Jan 23, 2014; returned for revision Apr 3, 2014; accepted for publication May 22, 2014. Ó 2014 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.oooo.2014.05.022
symptoms of severe TMJ arthralgia, and Al-Ani et al.8 reported its positive effect of alleviating pain related to TMJ disorder. However, its effect on OA has not been fully investigated despite the increasing clinical need for more research regarding the effects of SS in cases of OA. Moreover, considering that TMJ OA is diagnosed based on signs and symptoms, as well as subsequent clinical tests for the condition and radiographic evidence of degenerative osseous changes in the condylar heads,2 the radiographic changes from SS should also be confirmed. Among the pertinent radiographic studies, Lee et al. investigated 54 OA-affected TMJs in a 1-year follow-up study to evaluate longitudinal radiographic changes in relation to clinical signs and symptoms based on conventional computed tomography (CT) images of TMJ OA.9 Liu et al.10 reported a “double contour” appearance in the medial and intermediate segments of the condyle when an anterior repositioning splint (ARS) was applied using CT images. Therefore, the purpose of this study was to evaluate the effects of sectional osseous changes arising from SS treatment for patients with TMJ OA, specifically regarding condylar bone formation and cortical thickening. The specific aims of the study were (1) to
Statement of Clinical Relevance The observed changes in the radiographic appearance of the condyle suggest that stabilization splint therapy in temporomandibular joint osteoarthritis could induce favorable bone remodeling in the anterior division of the condylar head with degenerative condylar changes. 363
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investigate osseous changes in articular surface bone and cortical bone thickness, and (2) to compare two patient groups that respectively had and had not undergone SS therapy.
Table I. Study variables’ baseline characteristics
MATERIALS AND METHODS Study design and population We developed a case-control study and enrolled a sample of TMJ OA patients from among the population of patients presenting, for TMJ disorder, to Pusan National University Hospital, Department of Oral Medicine, between 2009 and 2012. The inclusion criteria were based on signs and symptoms, subsequent clinical tests for TMJ OA, and panoramic and cervicocranial radiographs. In all of the cases of diagnosed TMJ OA, cone beam CT (CBCT; Zenith 3-D; Vatech Co., Seoul, Korea) was used to confirm osseous change in the condylar surface, satisfying the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD).11 In addition to TMJ OA patients who were diagnosed based on the RDC/TMD, patients who had shown symptoms of TMJ OA without definitive RDC/TMD-indicated radiologic evidence of it and had been following the pertinent clinical treatment protocol were also included under the “TMJ OA” diagnosis. Patients whose treatment plans included maxillary SS therapy were designated the SS group, and patients who had been treated with the same conventional therapeutic protocol of TMJ OA as the SS group with the exception of SS therapy were designated the non-SS group. This study was reviewed and approved by the Institutional Review Board of Pusan National University Hospital (E-2012056).
All patients 57 (100.0) 18 (31.6) Gender Female 48 (84.2) 14 (77.8) Male 9 (15.8) 4 (22.2) Signs & symptoms* Pain 4.0 2.2 Noise 4.2 2.6 LOM 2.8 3.0 MCO (mm) 42.8 9.7
Study variables The predictor variable was SS treatment or non-SS treatment. In this study, based on the clinical examination results and radiographic findings, SS therapy was recommended to all of the participating patients for their TMJ OA. Patients decided whether or not to undergo the recommended SS therapy. All of the patients in the SS and non-SS groups also received physical and cognitive behavior therapy. At the first clinical exam, pain, noise, limitation of mouth opening (LOM), and maximum comfortable opening (MCO) were recorded for all patients. They were asked to rate their TMJ pain, noise, and LOM on a numerical rating scale of 0 to 10, where 0 represented “no unpleasantness at all” and 10 represented “the most unpleasantness imaginable.” The MCO was measured between the upper and lower incisors in millimeters (Table I). The SSs were fabricated in acrylic resin of 2 mm thickness at the molar area and covered all of the maxillary teeth. Based on a maximum intercuspation record, the occlusion was provided to create uniform points of contact for the centric cusps against the splint on all occluding teeth (Figure 1).
SS therapy Variable
Group size (%)
Presence Absence (SS group) (Non-SS group) P value 39 (68.4) 34 (87.2) 5 (12.8)
.366
3.2 2.2 3.3 2.0 2.3 2.6 43.4 8.4
.491 .649 .305 .580
SS, stabilization splint; LOM, limitation of mouth opening; MCO, maximum comfortable opening. P values higher than .05 indicate no statistically significant difference between the SS and non-SS groups at the 95% confidence level. *LOM was assigned the numerical rating scale from 0 to 10. MCO is given in millimeters.
The outcome variables were sectional osseous changes to the condylar surfaces, specifically the following categorical variables: condylar bone formation and cortical thickening. CBCT images were obtained at the initial clinical examination and at the end of treatment. The comparison of images obtained at these 2 time points revealed improved signs and symptoms. Preparatory to an evaluation of osseous changes in condylar heads,12 pretreatment (T0) and post-treatment (T1, 10.9 4.4 months after initial treatment) CBCT images from each patient were superimposed using voxel registration (Figure 2). The voxel registration areas were the neck of the condyle, the mandibular notch, and the posterior ramal area.13 For area-specific evaluation, the superimposed condylar heads were divided by a plane parallel to the axis of the neck of the condyle and passing through both the median and lateral poles to form anterior and posterior divisions; each division was isometrically partitioned into lateral, intermediate, and medial segments, thereby delineating the anterolateral (AL), anterior-intermediate (AI), anteromedial (AM), posterolateral (PL), posterior-intermediate (PI), and posteromedial (PM) sections in the head of the condyle (Figure 3). For each section, the osseous change was evaluated with respect to (1) articular surface bone changes at T1 relative to the T0 baseline (visibly apparent increase in the volume ¼ “bone formation”; visibly apparent decrease in the volume ¼ “bone loss”; no apparent change in the volume ¼ “no change”); and (2) cortical thickness (visibly apparent cortical thickening ¼ “cortical thickening”; visibly apparent cortical thinning ¼ “cortical thinning”; no evident change ¼ “no change”) (Figures 4 and 5). All of the radiographic interpretations were based on visual evaluation and not metrically quantified. For the purposes of CBCT image superimposition and
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Fig. 1. Stabilization splint (A) and intraoral photo (B). The stabilization splints were fabricated in acrylic resin; they were 2 mm thick at the molar area and covered all of the maxillary teeth. Based on a maximum intercuspation record, the occlusion was provided to create uniform points of contact for the centric cusps against the splint on all occluding teeth.
Fig. 2. The superimposition method for condylar assessment. Rectangles denote the registration area, which includes the condylar neck and posterior ramal area.
interpretation, the CBCT data were reformatted using 3-dimensional (3-D) imaging software (Ondemand 3-D; Cybermed Co., Seoul, Korea) set to the following parameters: field of view: 20 19 cm; tube voltage: 110 kVp; tube current: 4.0 mA; scan time: 24 seconds. All of the interpretations were made under the same graphic conditions. Statistical analysis The radiographic evaluation data were summarized in the form of descriptive statistics regarding the frequencies and percentages of the categorical variables representing the manifested osseous changes. A statistical analysis based on the chi-squared test was performed using SPSS (ver. 18.0 for Windows; SPSS Inc., Chicago, IL, USA) to compare the differences in the
patients’ demographic and clinical characteristics across subgroups. The statistical significance was evaluated based on a P value of .05. To address the issue of multiple comparison, the Bonferroni method was used with an adjusted a of 0.0083 ¼ 0.05/6. Two separate radiographic evaluations for reproducibility of superimposition, using Cohen’s kappa index (k) for surface bone volume and cortical thickness, were re-performed 2 weeks after the initial examination. The intra- and inter-investigator agreements were 0.81 and 0.72, respectively.
RESULTS We compared 18 patients in the SS group (4 men and 14 women; average age: 30.7 years, range: 21-59 years) with 39 patients in the non-SS (no splint) group (5 men
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Fig. 3. The 6 sections of the mandibular-condylar head, as viewed from the (A) anterior aspect, (B) superior aspect, and (C) posterior aspect. AL, anterolateral; AI, anterior-intermediate; AM, anteromedial; PL, posterolateral; PI, posterior-intermediate; PM, posteromedial.
Fig. 4. Radiographic image interpretation: bone formation and resorption.
and 34 women; average age: 30.6 years, range: 19-60 years) (Table I). The CBCT radiographic interpretation of osseous change revealed no statistically significant demographic difference between the SS and non-SS groups. Based on the clinical and radiographic CBCT findings at the initial examination (pretreatment image, T0), SS therapy was recommended to all of the participating patients for their TMJ OA. Patients decided whether or not to undergo the recommended SS therapy. All the patients in the SS and non-SS groups also received physical and cognitive behavior therapy. Post-treatment CBCT images were obtained at the end of treatment (T1, 10.9 4.4 months after initial treatment) and revealed improved signs and symptoms. Regarding changes in the condylar surface bone from T0 to T1, greater proportions of the SS group exhibited bone formation in the anterior sections (AM: 66.7%, AI: 63.9%, AL: 50%) than in the posterior sections (Tables II and III). Moreover, consistently in every section, markedly fewer patients in the SS group than the non-SS group exhibited bone destruction (Table II). Meanwhile, the majority of the non-SS group exhibited
“no change” regarding condylar surface bone formation in every section (AM: 64.1%, AI: 61.5%, AL: 67.9%, PM: 76.9%, PI: 80.8%, PL: 88.5%), demonstrating statistically significant differences from the SS group (P < .0001 for all; Tables II and IV. During the evaluation of post-treatment cortical changes, an intergroup disparity was likewise apparent (P < .0001; Table V): The SS group exhibited a higher frequency of cortical thickening in most of the anterior and posterior sections (AM: 86.1%, AI: 83.3%, AL: 72.0%, PM: 52.8%, PI: 50%) except for the PL section (Tables V and VI): in the non-SS group, “no change” prevailed in every section (AM: 46.2%, AI: 41.0%, AL: 57.7%, PM: 69.2%, PI: 71.8%, PL: 82.1%) (Tables V and VII). The frequency of cortical destruction was also significantly lower in the SS group than in the non-SS group (Table V).
DISCUSSION The purpose of this study was to evaluate the sectional osseous changes affected by SS treatment of patients with TMJ OA, specifically as manifested in condylar bone formation and cortical thickening. The specific
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Fig. 5. Radiographic image interpretation: cortical thickening and resorption.
Table II. Comparison of osseous change of condylar-articular surface between SS and non-SS groups SS therapy Sections Anteromedial
Anterior-intermediate
Anterolateral
Posteromedial
Posterior-intermediate
Posterolateral
Condyle surface change at T1 from baseline at T0 Bone loss No change Bone formation Bone loss No change Bone formation Bone loss No change Bone formation Bone loss No change Bone formation Bone loss No change Bone formation Bone loss No change Bone formation
Presence (SS group) (n ¼ 36) 0 12 24 3 10 23 0 18 18 2 20 14 2 25 9 1 27 8
(0.0) (33.3) (66.7) (8.3) (27.8) (63.9) (0.0) (50.0) (50.0) (5.6) (55.6) (38.9) (5.6) (69.4) (25.0) (2.8) (75.0) (22.2)
Absence (Non-SS group) (n ¼ 78) 24 50 4 27 48 3 22 53 3 16 60 2 14 63 1 9 69 0
(30.8) (64.1) (5.1) (34.6) (61.5) (3.8) (28.2) (67.9) (3.8) (20.5) (76.9) (2.6) (17.9) (80.8) (1.3) (11.5) (88.5) (0.0)
P value* <.0001 <.0001 <.0001 <.0001 <.0001 <.0001
*P values less than .0001 indicate a statistically significant intergroup disparity at the 99.99% confidence level.
aims of the study were to investigate osseous changes in articular surface bone and cortical bone thickness and to compare the presence and absence of SS therapy in 2 patient groups. Based on the (pre- and post-treatment) CBCT image superimposition method, the results indicated that SS therapy induced favorable bone remodeling in the anterior division of the condylar head. Indeed, the key finding of the present study was that condylar bone formation and cortical thickening occurred predominantly in the anterior division of the condylar head. Regarding post-treatment condylar bone changes, a greater proportion of the SS group exhibited bone formation in the anterior division than in the posterior
division, whereas the majority of non-SS patients exhibited no change. Regarding cortical changes, cortical thickening was more frequent in the anteromedial, anterior-intermediate, anterolateral, posteromedial, and posterior-intermediate sections of the SS group than the non-SS group. The observation of this study, that articular surface bone formation and cortical thickening in the SS group predominantly occurred in the AM and AI sections within the anterior division (Tables II and V), is comparable to the findings of Liu et al.,10 who reported a “double contour” appearance in the medial and intermediate segments of the condyle when ARS was applied. They observed osseous changes in the medial
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Table III Comparison of surface bone change among 6 sections in SS group according to the number of the corresponding condyles (%) Location Surface bone change Bone loss No change Bone formation
AM
AI
AL
PM
PI
PL
P value
0 (0.0) 12 (33.3) 24 (66.7)
3 (8.3) 10 (27.8) 23 (63.9)
0 (0.0) 18 (50.0) 18 (50.0)
2 (5.6) 20 (55.6) 14 (38.9)
2 (5.6) 25 (69.4) 9 (25.0)
1 (2.8) 27 (75.0) 8 (22.2)
< .0001*
AM, anteromedial; AI, anterior-intermediate; AL, anterolateral; PM, posteromedial; PI, posterior-intermediate; PL, posterolateral; SS, stabilization splint. *P values less than .0001 indicate a statistically significant variation of surface bone change among the 6 sections at the 99.99% confidence level.
Table IV Comparison of surface bone change among 6 sections in non-SS group according to the number of the corresponding condyles (%) Location Bone change
AM
AI
AL
PM
PI
PL
P value
Bone loss No change Bone formation
24 (30.8) 50 (64.1) 4 (5.1)
27 (34.6) 48 (61.5) 3 (3.8)
22 (28.2) 53 (67.9) 3 (3.8)
16 (20.5) 60 (76.9) 2 (2.6)
14 (17.9) 63 (80.8) 1 (1.3)
9 (11.5) 69 (88.5) 0 (0.0)
.010*
AM, anteromedial; AI, anterior-intermediate; AL, anterolateral; PM, posteromedial; PI, posterior-intermediate; PL, posterolateral; SS, stabilization splint. *P values at .01 indicate a statistically significant variation of surface bone change among the 6 sections at the 99% confidence level.
Table V Comparison of cortical change between SS and non-SS groups SS therapy Sections Anteromedial
Anterior-intermediate
Anterolateral
Posteromedial
Posterior-intermediate
Posterolateral
Cortical change from baseline Cortical thinning No change Cortical thickening Cortical thinning No change Cortical thickening Cortical thinning No change Cortical thickening Cortical thinning No change Cortical thickening Cortical thinning No change Cortical thickening Cortical thinning No change Cortical thickening
Presence (n ¼ 36, %) 0 5 31 0 6 30 0 10 26 0 17 19 0 18 18 0 21 15
(0.0) (13.9) (86.1) (0.0) (16.7) (83.3) (0.0) (27.8) (72.2) (0.0) (47.2) (52.8) (0.0) (50.0) (50.0) (0.0) (58.3) (41.7)
Absence (n ¼ 78, %) 17 36 25 20 32 26 13 45 20 11 54 13 12 56 10 7 64 7
(21.8) (46.2) (32.1) (25.6) (41.0) (33.3) (16.7) (57.7) (25.6) (14.1) (69.2) (16.7) (15.4) (71.8) (12.8) (9.0) (82.1) (9.0)
P value* <.0001 <.0001 <.0001 <.0001 <.0001 <.0001
*P values less than .0001 indicate a statistically significant intergroup disparity at the 99.99% confidence level.
and middle (rather than the lateral) parts of the condyle in 80% of patients diagnosed with anterior disk displacement after ARS therapy. Previous studies had presumed that the appearance of such a double contour represented periosteal bone formation in the posterior division of the condyle resulting from the release of pressure in the articular fossa.10,14 They inferred that the ARS induced forward and downward mandibular repositioning, thus reducing mechanical loadings when the condyle compressed the retrodiscal tissues, leading
to bone remodeling of the posterior division of the condyle and manifesting as the double contour. In our study, in which the SS was applied, cortical thickening comparable to the ARS’ double contour was observed in 86.1% of the condyles in the anteromedial section and 83.3% of those in the anterior-intermediate section. However, although the results for the SS were consistent with the previous ARS findings in the medial and intermediate segments where such remodeling was observed, they differed in that the remodeling was more
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Table VI. Comparison of cortical change among locations in SS group according to the number of the corresponding condyles (%) Location Cortical change
AM
AI
AL
PM
PI
PL
P value
Cortical thinning No change Cortical thickening
0 (0.0) 5 (13.9) 31 (86.1)
0 (0.0) 6 (16.7) 30 (83.3)
0 (0.0) 10 (27.8) 26 (72.2)
0 (0.0) 17 (47.2) 19 (52.8)
0 (0.0) 18 (50.0) 18 (50.0)
0 (0.0) 21 (58.3) 15 (41.7)
<.0001*
AM, anteromedial; AI, anterior-intermediate; AL, anterolateral; PM, posteromedial; PI, posterior-intermediate; PL, posterolateral; SS, stabilization splint. *P values less than .0001 indicate a statistically significant variation of cortical change among the 6 sections at the 99.99% confidence level.
Table VII. Comparison of cortical change among locations in non-SS group according to the number of the corresponding condyles (%) Location Cortical change
AM
AI
AL
PM
PI
PL
P value
Cortical thinning No change Cortical thickening
17 (21.8) 36 (46.2) 25 (32.1)
20 (25.6) 32 (41.0) 26 (33.3)
13 (16.7) 45 (57.7) 20 (25.6)
11 (14.1) 54 (69.2) 13 (16.7)
12 (15.4) 56 (71.8) 10 (12.8)
7 (9.0) 64 (82.1) 7 (9.0)
<.0001*
AM, anteromedial; AI, anterior-intermediate; AL, anterolateral; PM, posteromedial; PI, posterior-intermediate; PL, posterolateral; SS, stabilization splint. *P values less than .0001 indicate a statistically significant variation of cortical change among the 6 sections at the 99.99% confidence level.
apparent in the anterior division than in the posterior division (Table VI); this finding is related to the SS function of releasing mechanical loadings that tend to focalize on the anterior division of the upper condylar surface,15 which is located more anteriorly than the ARS. Also, as Ko et al.16 reported, thickening of the cortex is presumably a response of the subchondral cortical bone to a nonpathologic level of pressure; this supports the idea that cortical thickening can be considered radiographic evidence of the efficacy of treatment with respect to the release of pathologic mechanical overloading. For more accurate pre- to post-treatment comparison of the condylar heads, we used CBCT and the CBCT superimposition method. The superimposition method was introduced by Park et al. to investigate postoperative changes in the condylar head after orthognathic surgery.13 They used the mutual information registration method to evaluate condylar head remodeling at a reduced risk of operator error, and recommended ramus regions, including the condylar neck and the posterior ramal area above the lingula of the mandible, for stable registration.15 In our study, to improve the assessment of changes to the condylar head after conservative treatment with and without the SS, we applied the sub-voxel accuracy for superimposition and image interpretation method. CBCT images were obtained before treatment and 10.9 4.4 months after treatment. This is a reasonable interval in which to compare osseous changes in the condyle because a double contour after ARS therapy has been observed
within 6 months of treatment.10 However, 3-D surfacerendering image superimposition regarding the 3-D shape of the condylar head should follow, in order to provide a better understanding of the post-treatment condylar change after SS therapy.17 The present study is exploratory in that we examined the effects of SS with respect to the radiographic change of the condyle. However, as a limitation of this study, the symptomatic improvement of the study participants was not considered, although it is a significant factor in evaluations of the treatment effects of most TMJ diseases. In addition, we did not perform Wilkes staging18 on the clinical and radiographic state of TMJs of study participants. Our observation that a non-SS group member exhibited no radiographic improvement does not necessarily mean that there has been no symptomatic improvement. Several studies have reported the discrepancy between clinical signs and symptoms and morphologic change in TMJ OA.19-22 Accordingly, to further evaluate whether SS has a therapeutic effect, an evaluation of symptomatic patients should be both qualitative and quantitative in scope and should include magnetic resonance imaging evaluation and specific relationships to Wilkes Stage.18
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ORAL AND MAXILLOFACIAL RADIOLOGY 370 Ok et al. 3. Pereira FJ Jr, Lundh H, Westesson PL, Carlsson LE. Clinical findings related to morphologic changes in TMJ autopsy specimens. Oral Surg Oral Med Oral Pathol. 1994;78:288-295. 4. Machon V, Hirjak D, Lukas J. Therapy of the osteoarthritis of the temporomandibular joint. J Craniomaxillofac Surg. 2011;39: 127-130. 5. Manfredini D, Guarda-Nardini L, Ferronato G. Single-needle temporomandibular joint arthrocentesis with hyaluronic acid injections. Preliminary data after a five-injection protocol. Minerva Stomatol. 2009;58:471-478. 6. Mejersjö C, Wenneberg B. Diclofenac sodium and occlusal splint therapy in TMJ osteoarthritis: a randomized controlled trial. J Oral Rehabil. 2008;35:729-738. 7. Kuttila M, Le Bell Y, Savolainen-Niemi E, Kuttila S, Alanen P. Efficiency of occlusal appliance therapy in secondary otalgia and temporomandibular disorders. Acta Odontol Scand. 2002;60: 248-254. 8. Al-Ani MZ, Davies SJ, Gray RJ, Sloan P, Glenny A. Stabilisation splint therapy for temporomandibular pain dysfunction syndrome. Cochrane Database Syst Rev. 2004;1:CD002778. 9. Lee JY, Kim DJ, Lee SG, Chung JW. A longitudinal study on the osteoarthritic change of the temporomandibular joint based on 1year follow-up computed tomography. J Craniomaxillofac Surg. 2012;40:e223-e228. 10. Liu MQ, Chen HM, Yap AU, Fu KY. Condylar remodeling accompanying splint therapy: A cone-beam computerized tomography study of patients with temporomandibular joint disk displacement. Oral Surg Oral Med Oral Pathol Oral Radiol. 2012;114:259-265. 11. Dworkin SF, LeResche L. Research diagnostic criteria for temporomandibular disorders: Review, criteria, examinations and specifications, critique. J Craniomandib Disord. 1992;6:301-355. 12. Rohlin M, Akerman S, Kopp S. Tomography as an aid to detect macroscopic changes of the temporomandibular joint. An autopsy study of the aged. Acta Odontol Scand. 1986;44:131-140. 13. Park SB, Yang YM, Kim YI, Cho BH, Jung YH, Hwang DS. Effect of bimaxillary surgery on adaptive condylar head remodeling: Metric analysis and image interpretation using cone-beam computed tomography volume superimposition. J Oral Maxillofac Surg. 2012;70:1951-1959. 14. Suei Y, Tanimoto K, Ogawa I, Wada T. Formation of double contour in the human mandibular condyle. A case report. Oral Surg Oral Med Oral Pathol. 1994;77:327-330.
OOOO September 2014 15. Ueki K, Nakagawa K, Takatsuka S, Yamamoto E, Laskin DM. Comparison of the stress direction on the TMJ in patients with class I, II, and III skeletal relationships. Orthod Craniofac Res. 2008;11:43-50. 16. Ko FC, Dragomir C, Plumb DA, et al. In vivo cyclic compression causes cartilage deformation and subchondral bone changes in mouse tibiae. Arthritis Rheum. 2013;65:1569-1578. 17. Cevidanes LH, Hajati AK, Paniagua B, et al. Quantification of condylar resorption in temporomandibular joint osteoarthritis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010;110: 110-117. 18. Wilkes CH. Internal derangements of the temporomandibular joint. Pathologic variations. Arch Otolaryngol Head Neck Surg. 1989;115:469-477. 19. Look JO, Schiffman EL, Truelove EL, Ahmad M. Reliability and validity of Axis I of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) with proposed revisions. J Oral Rehabil. 2010;37:744-759. 20. Wiese M, Svensson P, Bakke M, et al. Association between temporomandibular joint symptoms, signs, and clinical diagnosis using the RDC/TMD and radiographic findings in temporomandibular joint tomograms. J Orofac Pain. 2008;22:239-251. 21. Schiffman EL, Ohrbach R, Truelove EL, et al. The Research Diagnostic Criteria for Temporomandibular Disorders. V: Methods used to establish and validate revised Axis I diagnostic algorithms. J Orofac Pain. 2010;24:63-78. 22. Johnston CD, Gleadhill IC, Cinnamond MJ, Peden WM. Oral appliances for the management of severe snoring: a randomized controlled trial. Eur J Orthod. 2001;23:127-134.
Reprint requests: Yong-Il Kim, PhD Assistant professor Department of Orthodontics, School of Dentistry Pusan National University, Biomedical Research Institute Pusan National University Hospital, Dental Research Institute Pusan National University Dental Hospital Gudeokro 137 Seogu, Busan South Korea 602-739 [email protected]
Anterior condylar remodeling observed in stabilization splint therapy for temporomandibular joint osteoarthritis Soo-Min Ok, PhD,a Jihyun Lee,b Yong-Il Kim, PhD,b Jae-Yeol Lee, PhD,c Ki Beom Kim, DDS, MSD, PhD,d and Sung-Hee Jeong, PhDa Pusan National University, Busan, South Korea; and Saint Louis University, St Louis, MO, USA
Objective. To comparatively evaluate condylar surface bone formation and cortical thickening in patients with temporomandibular joint osteoarthritis, with or without stabilization splint (SS) therapy. Study Design. This retrospective study of 57 OA patients included 18 patients who had undergone SS therapy (SS group), compared with 39 patients that had not received SS therapy (non-SS group). To evaluate osseous changes on the condylar bone formation and cortical thickening, pre- and post-treatment cone beam computed tomography images of each patient were superimposed using voxel registration. Results. The SS group exhibited a higher ratio of bone formation in the anterior division of the condyle; the non-SS group exhibited mostly no change. The SS group was found to have higher frequencies of cortical thickening in the anteromedial, anterior-intermediate, anterolateral, posteromedial, and posterior-intermediate sections than the non-SS group. Conclusions. SS therapy in temporomandibular joint osteoarthritis induced favorable bone remodeling in the anterior division of the condylar head. (Oral Surg Oral Med Oral Pathol Oral Radiol 2014;118:363-370)
Signs and symptoms of temporomandibular joint (TMJ) arthralgia often are attributable to TMJ osteoarthritis (OA), a severe form of TMJ disorder marked by degenerative osseous changes accompanied by secondary inflammation.1 The main cause of TMJ OA is excessive overloading of the articulation surpassing physiologic tolerance. This overload of the joint leads to the degenerative change of the articular surface of the mandibular condyle and subsequent cortical destruction.2 Resultant gross morphologic changes, such as deviation in form, disk displacement, adhesions, and osteoarthritic processes, can occur with or without the experience of pain or dysfunction.3 As the conservative approach to TMJ OA, the therapeutic protocol of physiotherapy, medication, occlusal appliance therapy, and intra-articular injection is well established.4-6 Among these, the stabilization splint (SS) has been clinically confirmed to effectively protect the TMJ against unintentional overloading and relieve excessive muscular tension while preventing sprain in the mandibular condyle in the case of bruxism.2 Kuttila et al.7 reported that the use of SS improved the clinical a Department of Oral Medicine, School of Dentistry, Pusan National University, Busan, South Korea. b Department of Orthodontics, Pusan National University, Biomedical research institute, Pusan National University Hospital, Busan, South Korea. c Department of Oral & Maxillofacial Surgery, Pusan National University Hospital, Busan, South Korea. d Department of Orthodontics, Center for Advanced Dental Education, Saint Louis University, St Louis, MO, USA. Received for publication Jan 23, 2014; returned for revision Apr 3, 2014; accepted for publication May 22, 2014. Ó 2014 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.oooo.2014.05.022
symptoms of severe TMJ arthralgia, and Al-Ani et al.8 reported its positive effect of alleviating pain related to TMJ disorder. However, its effect on OA has not been fully investigated despite the increasing clinical need for more research regarding the effects of SS in cases of OA. Moreover, considering that TMJ OA is diagnosed based on signs and symptoms, as well as subsequent clinical tests for the condition and radiographic evidence of degenerative osseous changes in the condylar heads,2 the radiographic changes from SS should also be confirmed. Among the pertinent radiographic studies, Lee et al. investigated 54 OA-affected TMJs in a 1-year follow-up study to evaluate longitudinal radiographic changes in relation to clinical signs and symptoms based on conventional computed tomography (CT) images of TMJ OA.9 Liu et al.10 reported a “double contour” appearance in the medial and intermediate segments of the condyle when an anterior repositioning splint (ARS) was applied using CT images. Therefore, the purpose of this study was to evaluate the effects of sectional osseous changes arising from SS treatment for patients with TMJ OA, specifically regarding condylar bone formation and cortical thickening. The specific aims of the study were (1) to
Statement of Clinical Relevance The observed changes in the radiographic appearance of the condyle suggest that stabilization splint therapy in temporomandibular joint osteoarthritis could induce favorable bone remodeling in the anterior division of the condylar head with degenerative condylar changes. 363
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investigate osseous changes in articular surface bone and cortical bone thickness, and (2) to compare two patient groups that respectively had and had not undergone SS therapy.
Table I. Study variables’ baseline characteristics
MATERIALS AND METHODS Study design and population We developed a case-control study and enrolled a sample of TMJ OA patients from among the population of patients presenting, for TMJ disorder, to Pusan National University Hospital, Department of Oral Medicine, between 2009 and 2012. The inclusion criteria were based on signs and symptoms, subsequent clinical tests for TMJ OA, and panoramic and cervicocranial radiographs. In all of the cases of diagnosed TMJ OA, cone beam CT (CBCT; Zenith 3-D; Vatech Co., Seoul, Korea) was used to confirm osseous change in the condylar surface, satisfying the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD).11 In addition to TMJ OA patients who were diagnosed based on the RDC/TMD, patients who had shown symptoms of TMJ OA without definitive RDC/TMD-indicated radiologic evidence of it and had been following the pertinent clinical treatment protocol were also included under the “TMJ OA” diagnosis. Patients whose treatment plans included maxillary SS therapy were designated the SS group, and patients who had been treated with the same conventional therapeutic protocol of TMJ OA as the SS group with the exception of SS therapy were designated the non-SS group. This study was reviewed and approved by the Institutional Review Board of Pusan National University Hospital (E-2012056).
All patients 57 (100.0) 18 (31.6) Gender Female 48 (84.2) 14 (77.8) Male 9 (15.8) 4 (22.2) Signs & symptoms* Pain 4.0 2.2 Noise 4.2 2.6 LOM 2.8 3.0 MCO (mm) 42.8 9.7
Study variables The predictor variable was SS treatment or non-SS treatment. In this study, based on the clinical examination results and radiographic findings, SS therapy was recommended to all of the participating patients for their TMJ OA. Patients decided whether or not to undergo the recommended SS therapy. All of the patients in the SS and non-SS groups also received physical and cognitive behavior therapy. At the first clinical exam, pain, noise, limitation of mouth opening (LOM), and maximum comfortable opening (MCO) were recorded for all patients. They were asked to rate their TMJ pain, noise, and LOM on a numerical rating scale of 0 to 10, where 0 represented “no unpleasantness at all” and 10 represented “the most unpleasantness imaginable.” The MCO was measured between the upper and lower incisors in millimeters (Table I). The SSs were fabricated in acrylic resin of 2 mm thickness at the molar area and covered all of the maxillary teeth. Based on a maximum intercuspation record, the occlusion was provided to create uniform points of contact for the centric cusps against the splint on all occluding teeth (Figure 1).
SS therapy Variable
Group size (%)
Presence Absence (SS group) (Non-SS group) P value 39 (68.4) 34 (87.2) 5 (12.8)
.366
3.2 2.2 3.3 2.0 2.3 2.6 43.4 8.4
.491 .649 .305 .580
SS, stabilization splint; LOM, limitation of mouth opening; MCO, maximum comfortable opening. P values higher than .05 indicate no statistically significant difference between the SS and non-SS groups at the 95% confidence level. *LOM was assigned the numerical rating scale from 0 to 10. MCO is given in millimeters.
The outcome variables were sectional osseous changes to the condylar surfaces, specifically the following categorical variables: condylar bone formation and cortical thickening. CBCT images were obtained at the initial clinical examination and at the end of treatment. The comparison of images obtained at these 2 time points revealed improved signs and symptoms. Preparatory to an evaluation of osseous changes in condylar heads,12 pretreatment (T0) and post-treatment (T1, 10.9 4.4 months after initial treatment) CBCT images from each patient were superimposed using voxel registration (Figure 2). The voxel registration areas were the neck of the condyle, the mandibular notch, and the posterior ramal area.13 For area-specific evaluation, the superimposed condylar heads were divided by a plane parallel to the axis of the neck of the condyle and passing through both the median and lateral poles to form anterior and posterior divisions; each division was isometrically partitioned into lateral, intermediate, and medial segments, thereby delineating the anterolateral (AL), anterior-intermediate (AI), anteromedial (AM), posterolateral (PL), posterior-intermediate (PI), and posteromedial (PM) sections in the head of the condyle (Figure 3). For each section, the osseous change was evaluated with respect to (1) articular surface bone changes at T1 relative to the T0 baseline (visibly apparent increase in the volume ¼ “bone formation”; visibly apparent decrease in the volume ¼ “bone loss”; no apparent change in the volume ¼ “no change”); and (2) cortical thickness (visibly apparent cortical thickening ¼ “cortical thickening”; visibly apparent cortical thinning ¼ “cortical thinning”; no evident change ¼ “no change”) (Figures 4 and 5). All of the radiographic interpretations were based on visual evaluation and not metrically quantified. For the purposes of CBCT image superimposition and
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Fig. 1. Stabilization splint (A) and intraoral photo (B). The stabilization splints were fabricated in acrylic resin; they were 2 mm thick at the molar area and covered all of the maxillary teeth. Based on a maximum intercuspation record, the occlusion was provided to create uniform points of contact for the centric cusps against the splint on all occluding teeth.
Fig. 2. The superimposition method for condylar assessment. Rectangles denote the registration area, which includes the condylar neck and posterior ramal area.
interpretation, the CBCT data were reformatted using 3-dimensional (3-D) imaging software (Ondemand 3-D; Cybermed Co., Seoul, Korea) set to the following parameters: field of view: 20 19 cm; tube voltage: 110 kVp; tube current: 4.0 mA; scan time: 24 seconds. All of the interpretations were made under the same graphic conditions. Statistical analysis The radiographic evaluation data were summarized in the form of descriptive statistics regarding the frequencies and percentages of the categorical variables representing the manifested osseous changes. A statistical analysis based on the chi-squared test was performed using SPSS (ver. 18.0 for Windows; SPSS Inc., Chicago, IL, USA) to compare the differences in the
patients’ demographic and clinical characteristics across subgroups. The statistical significance was evaluated based on a P value of .05. To address the issue of multiple comparison, the Bonferroni method was used with an adjusted a of 0.0083 ¼ 0.05/6. Two separate radiographic evaluations for reproducibility of superimposition, using Cohen’s kappa index (k) for surface bone volume and cortical thickness, were re-performed 2 weeks after the initial examination. The intra- and inter-investigator agreements were 0.81 and 0.72, respectively.
RESULTS We compared 18 patients in the SS group (4 men and 14 women; average age: 30.7 years, range: 21-59 years) with 39 patients in the non-SS (no splint) group (5 men
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Fig. 3. The 6 sections of the mandibular-condylar head, as viewed from the (A) anterior aspect, (B) superior aspect, and (C) posterior aspect. AL, anterolateral; AI, anterior-intermediate; AM, anteromedial; PL, posterolateral; PI, posterior-intermediate; PM, posteromedial.
Fig. 4. Radiographic image interpretation: bone formation and resorption.
and 34 women; average age: 30.6 years, range: 19-60 years) (Table I). The CBCT radiographic interpretation of osseous change revealed no statistically significant demographic difference between the SS and non-SS groups. Based on the clinical and radiographic CBCT findings at the initial examination (pretreatment image, T0), SS therapy was recommended to all of the participating patients for their TMJ OA. Patients decided whether or not to undergo the recommended SS therapy. All the patients in the SS and non-SS groups also received physical and cognitive behavior therapy. Post-treatment CBCT images were obtained at the end of treatment (T1, 10.9 4.4 months after initial treatment) and revealed improved signs and symptoms. Regarding changes in the condylar surface bone from T0 to T1, greater proportions of the SS group exhibited bone formation in the anterior sections (AM: 66.7%, AI: 63.9%, AL: 50%) than in the posterior sections (Tables II and III). Moreover, consistently in every section, markedly fewer patients in the SS group than the non-SS group exhibited bone destruction (Table II). Meanwhile, the majority of the non-SS group exhibited
“no change” regarding condylar surface bone formation in every section (AM: 64.1%, AI: 61.5%, AL: 67.9%, PM: 76.9%, PI: 80.8%, PL: 88.5%), demonstrating statistically significant differences from the SS group (P < .0001 for all; Tables II and IV. During the evaluation of post-treatment cortical changes, an intergroup disparity was likewise apparent (P < .0001; Table V): The SS group exhibited a higher frequency of cortical thickening in most of the anterior and posterior sections (AM: 86.1%, AI: 83.3%, AL: 72.0%, PM: 52.8%, PI: 50%) except for the PL section (Tables V and VI): in the non-SS group, “no change” prevailed in every section (AM: 46.2%, AI: 41.0%, AL: 57.7%, PM: 69.2%, PI: 71.8%, PL: 82.1%) (Tables V and VII). The frequency of cortical destruction was also significantly lower in the SS group than in the non-SS group (Table V).
DISCUSSION The purpose of this study was to evaluate the sectional osseous changes affected by SS treatment of patients with TMJ OA, specifically as manifested in condylar bone formation and cortical thickening. The specific
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Fig. 5. Radiographic image interpretation: cortical thickening and resorption.
Table II. Comparison of osseous change of condylar-articular surface between SS and non-SS groups SS therapy Sections Anteromedial
Anterior-intermediate
Anterolateral
Posteromedial
Posterior-intermediate
Posterolateral
Condyle surface change at T1 from baseline at T0 Bone loss No change Bone formation Bone loss No change Bone formation Bone loss No change Bone formation Bone loss No change Bone formation Bone loss No change Bone formation Bone loss No change Bone formation
Presence (SS group) (n ¼ 36) 0 12 24 3 10 23 0 18 18 2 20 14 2 25 9 1 27 8
(0.0) (33.3) (66.7) (8.3) (27.8) (63.9) (0.0) (50.0) (50.0) (5.6) (55.6) (38.9) (5.6) (69.4) (25.0) (2.8) (75.0) (22.2)
Absence (Non-SS group) (n ¼ 78) 24 50 4 27 48 3 22 53 3 16 60 2 14 63 1 9 69 0
(30.8) (64.1) (5.1) (34.6) (61.5) (3.8) (28.2) (67.9) (3.8) (20.5) (76.9) (2.6) (17.9) (80.8) (1.3) (11.5) (88.5) (0.0)
P value* <.0001 <.0001 <.0001 <.0001 <.0001 <.0001
*P values less than .0001 indicate a statistically significant intergroup disparity at the 99.99% confidence level.
aims of the study were to investigate osseous changes in articular surface bone and cortical bone thickness and to compare the presence and absence of SS therapy in 2 patient groups. Based on the (pre- and post-treatment) CBCT image superimposition method, the results indicated that SS therapy induced favorable bone remodeling in the anterior division of the condylar head. Indeed, the key finding of the present study was that condylar bone formation and cortical thickening occurred predominantly in the anterior division of the condylar head. Regarding post-treatment condylar bone changes, a greater proportion of the SS group exhibited bone formation in the anterior division than in the posterior
division, whereas the majority of non-SS patients exhibited no change. Regarding cortical changes, cortical thickening was more frequent in the anteromedial, anterior-intermediate, anterolateral, posteromedial, and posterior-intermediate sections of the SS group than the non-SS group. The observation of this study, that articular surface bone formation and cortical thickening in the SS group predominantly occurred in the AM and AI sections within the anterior division (Tables II and V), is comparable to the findings of Liu et al.,10 who reported a “double contour” appearance in the medial and intermediate segments of the condyle when ARS was applied. They observed osseous changes in the medial
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Table III Comparison of surface bone change among 6 sections in SS group according to the number of the corresponding condyles (%) Location Surface bone change Bone loss No change Bone formation
AM
AI
AL
PM
PI
PL
P value
0 (0.0) 12 (33.3) 24 (66.7)
3 (8.3) 10 (27.8) 23 (63.9)
0 (0.0) 18 (50.0) 18 (50.0)
2 (5.6) 20 (55.6) 14 (38.9)
2 (5.6) 25 (69.4) 9 (25.0)
1 (2.8) 27 (75.0) 8 (22.2)
< .0001*
AM, anteromedial; AI, anterior-intermediate; AL, anterolateral; PM, posteromedial; PI, posterior-intermediate; PL, posterolateral; SS, stabilization splint. *P values less than .0001 indicate a statistically significant variation of surface bone change among the 6 sections at the 99.99% confidence level.
Table IV Comparison of surface bone change among 6 sections in non-SS group according to the number of the corresponding condyles (%) Location Bone change
AM
AI
AL
PM
PI
PL
P value
Bone loss No change Bone formation
24 (30.8) 50 (64.1) 4 (5.1)
27 (34.6) 48 (61.5) 3 (3.8)
22 (28.2) 53 (67.9) 3 (3.8)
16 (20.5) 60 (76.9) 2 (2.6)
14 (17.9) 63 (80.8) 1 (1.3)
9 (11.5) 69 (88.5) 0 (0.0)
.010*
AM, anteromedial; AI, anterior-intermediate; AL, anterolateral; PM, posteromedial; PI, posterior-intermediate; PL, posterolateral; SS, stabilization splint. *P values at .01 indicate a statistically significant variation of surface bone change among the 6 sections at the 99% confidence level.
Table V Comparison of cortical change between SS and non-SS groups SS therapy Sections Anteromedial
Anterior-intermediate
Anterolateral
Posteromedial
Posterior-intermediate
Posterolateral
Cortical change from baseline Cortical thinning No change Cortical thickening Cortical thinning No change Cortical thickening Cortical thinning No change Cortical thickening Cortical thinning No change Cortical thickening Cortical thinning No change Cortical thickening Cortical thinning No change Cortical thickening
Presence (n ¼ 36, %) 0 5 31 0 6 30 0 10 26 0 17 19 0 18 18 0 21 15
(0.0) (13.9) (86.1) (0.0) (16.7) (83.3) (0.0) (27.8) (72.2) (0.0) (47.2) (52.8) (0.0) (50.0) (50.0) (0.0) (58.3) (41.7)
Absence (n ¼ 78, %) 17 36 25 20 32 26 13 45 20 11 54 13 12 56 10 7 64 7
(21.8) (46.2) (32.1) (25.6) (41.0) (33.3) (16.7) (57.7) (25.6) (14.1) (69.2) (16.7) (15.4) (71.8) (12.8) (9.0) (82.1) (9.0)
P value* <.0001 <.0001 <.0001 <.0001 <.0001 <.0001
*P values less than .0001 indicate a statistically significant intergroup disparity at the 99.99% confidence level.
and middle (rather than the lateral) parts of the condyle in 80% of patients diagnosed with anterior disk displacement after ARS therapy. Previous studies had presumed that the appearance of such a double contour represented periosteal bone formation in the posterior division of the condyle resulting from the release of pressure in the articular fossa.10,14 They inferred that the ARS induced forward and downward mandibular repositioning, thus reducing mechanical loadings when the condyle compressed the retrodiscal tissues, leading
to bone remodeling of the posterior division of the condyle and manifesting as the double contour. In our study, in which the SS was applied, cortical thickening comparable to the ARS’ double contour was observed in 86.1% of the condyles in the anteromedial section and 83.3% of those in the anterior-intermediate section. However, although the results for the SS were consistent with the previous ARS findings in the medial and intermediate segments where such remodeling was observed, they differed in that the remodeling was more
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Table VI. Comparison of cortical change among locations in SS group according to the number of the corresponding condyles (%) Location Cortical change
AM
AI
AL
PM
PI
PL
P value
Cortical thinning No change Cortical thickening
0 (0.0) 5 (13.9) 31 (86.1)
0 (0.0) 6 (16.7) 30 (83.3)
0 (0.0) 10 (27.8) 26 (72.2)
0 (0.0) 17 (47.2) 19 (52.8)
0 (0.0) 18 (50.0) 18 (50.0)
0 (0.0) 21 (58.3) 15 (41.7)
<.0001*
AM, anteromedial; AI, anterior-intermediate; AL, anterolateral; PM, posteromedial; PI, posterior-intermediate; PL, posterolateral; SS, stabilization splint. *P values less than .0001 indicate a statistically significant variation of cortical change among the 6 sections at the 99.99% confidence level.
Table VII. Comparison of cortical change among locations in non-SS group according to the number of the corresponding condyles (%) Location Cortical change
AM
AI
AL
PM
PI
PL
P value
Cortical thinning No change Cortical thickening
17 (21.8) 36 (46.2) 25 (32.1)
20 (25.6) 32 (41.0) 26 (33.3)
13 (16.7) 45 (57.7) 20 (25.6)
11 (14.1) 54 (69.2) 13 (16.7)
12 (15.4) 56 (71.8) 10 (12.8)
7 (9.0) 64 (82.1) 7 (9.0)
<.0001*
AM, anteromedial; AI, anterior-intermediate; AL, anterolateral; PM, posteromedial; PI, posterior-intermediate; PL, posterolateral; SS, stabilization splint. *P values less than .0001 indicate a statistically significant variation of cortical change among the 6 sections at the 99.99% confidence level.
apparent in the anterior division than in the posterior division (Table VI); this finding is related to the SS function of releasing mechanical loadings that tend to focalize on the anterior division of the upper condylar surface,15 which is located more anteriorly than the ARS. Also, as Ko et al.16 reported, thickening of the cortex is presumably a response of the subchondral cortical bone to a nonpathologic level of pressure; this supports the idea that cortical thickening can be considered radiographic evidence of the efficacy of treatment with respect to the release of pathologic mechanical overloading. For more accurate pre- to post-treatment comparison of the condylar heads, we used CBCT and the CBCT superimposition method. The superimposition method was introduced by Park et al. to investigate postoperative changes in the condylar head after orthognathic surgery.13 They used the mutual information registration method to evaluate condylar head remodeling at a reduced risk of operator error, and recommended ramus regions, including the condylar neck and the posterior ramal area above the lingula of the mandible, for stable registration.15 In our study, to improve the assessment of changes to the condylar head after conservative treatment with and without the SS, we applied the sub-voxel accuracy for superimposition and image interpretation method. CBCT images were obtained before treatment and 10.9 4.4 months after treatment. This is a reasonable interval in which to compare osseous changes in the condyle because a double contour after ARS therapy has been observed
within 6 months of treatment.10 However, 3-D surfacerendering image superimposition regarding the 3-D shape of the condylar head should follow, in order to provide a better understanding of the post-treatment condylar change after SS therapy.17 The present study is exploratory in that we examined the effects of SS with respect to the radiographic change of the condyle. However, as a limitation of this study, the symptomatic improvement of the study participants was not considered, although it is a significant factor in evaluations of the treatment effects of most TMJ diseases. In addition, we did not perform Wilkes staging18 on the clinical and radiographic state of TMJs of study participants. Our observation that a non-SS group member exhibited no radiographic improvement does not necessarily mean that there has been no symptomatic improvement. Several studies have reported the discrepancy between clinical signs and symptoms and morphologic change in TMJ OA.19-22 Accordingly, to further evaluate whether SS has a therapeutic effect, an evaluation of symptomatic patients should be both qualitative and quantitative in scope and should include magnetic resonance imaging evaluation and specific relationships to Wilkes Stage.18
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Reprint requests: Yong-Il Kim, PhD Assistant professor Department of Orthodontics, School of Dentistry Pusan National University, Biomedical Research Institute Pusan National University Hospital, Dental Research Institute Pusan National University Dental Hospital Gudeokro 137 Seogu, Busan South Korea 602-739 [email protected]