Although diverse surgical techniques for TMJ ankylosis have been described by many expert surgeons, satisfactory restorations of mouth opening with acceptable functions are very difficult due to many unexpected factors. Thus, clinical studies and outcome evaluations of surgical techniques for TMJ ankylosis are important [8, 9]. In this clinical study, nine TMJ ankylosis patients with different etiologies were comfortable while moving their mandible according to their IOS’s guiding plane and impingement, and they showed satisfactory results, with MMO of more than 35 mm after a follow-up period of more than 6 years.
The choice of TMJ ankylosis management counts on many consideration factors including the patient’s age with growth spurts, systemic conditions related to previous infections or autonomic immune disease, and surgeon’s experiences for selection of interpositional grafting materials [9]. Simple excision or resection, gap arthroplasty with or without interposition materials, and whole joint replacement with autogenous or alloplastic substitutes are the frequently used surgical techniques. In spite of having the benefits of simplicity and short operation time, gap arthroplasty has some disadvantages, such as pseudo-articulation with a short ramus, removal failure of previous bony pathology, and a high risk of re-ankylosis. Moreover, it has also several potential complications, including postoperative open bite, deviated occlusion with posterior premature contact, and suboptimal mouth opening [8,9,10,11]. Recurrence or re-ankylosis is also the main complication of TMJ ankylosis management; thus, any interpositional substitutes such as autogenous temporal fascia or alloplastic silicone material at the joint resection site have been a basic concept of maintaining the interarticular space for the recurrence prevention. Until recently, several substances have been recommended as potential interpositional materials for placement into the surgically created interarticular gap, such as temporal myofascia. These interpositional materials create some fibrotic space to maintain sufficient space for the resected neo-condylar head to freely function during rotation and translation. However, some authors [2, 12] reported that a wider resected bony gap is more important than any interpositional substitutes used and most of re-ankylosis could occur due to incomplete resection of ankylosed bony or fibrotic tissues. Our focus in this clinical study was also on the radical resection of ankylotic tissues to prevent recurrence.
Danda and Chinnaswami [9] reported no significant different outcomes whether in interpositional arthroplasty or only gap arthroplasty in their 16 TMJ ankylosis cases, and Vasconcelos et al. [10] and Roychoudhury et al. [13] also reported good results of gap arthroplasty only each in their 8 cases and 50 cases, respectively. In our study, gap arthroplasty without an interpositional graft was performed in a total of nine patients, and we used an IOS for keeping the interarticular space instead of any interpositional substance with satisfactory results; the MMO was greater than 35 mm during the follow-up period (Table 1).
Previously, many surgeons used to neglect the importance of coronoidectomy in the TMJ ankylosis management, but coronoid process removal on both sides is one of the essential procedures due to the releasing effects of contracted temporal muscle and limited jaw movements [2]. If there is any lack of opening during operation, any slight fibrosis or contraction of the contralateral temporal muscle could be released by coronoidectomy together [13]. Thus, if a MMO value less than 25 mm is observed during operation, the contralateral joint and/or coronoid process with temporalis musculature should be released according to the nature of the opening limitation. We executed coronoidectomy in all our patients as the essential procedure for better results, ipsilateral in three patients and bilateral coronoidectomies in six patients (Table 1). Elongated stylohyoid ligament calcification can cause additional mouth opening limitation and severe neck pain. In our Eagle’s syndrome patient (patient number 9), both stylohyoidectomy with coronoidectomy were very helpful for mouth opening and normal mandibular movement [14]. For successful surgical results, at least 35-mm passive MMO should be acquired in the successful surgical results; therefore, complete resection of ankylosed mass with accompanying coronoidectomy is essential.
Immediate physiotherapy for TMJ patients is very important to prevent adhesion and subsequent re-ankylosis [12]. Roychoudhury et al. [13] showed the importance of postoperative physiotherapy for the prevention of re-ankylosis and for building muscular strength and bulk. Especially, increased mouth opening exercises should protract all the restricted masticatory muscles for re-adaptations of their previous inactive muscle tensions [15]. Furthermore, early mouth opening exercises could help the surgically established joint space become physiologically reorganized, so we used IOS to create and maintain this reorganized joint space.
We used IOSs to aide a patient’s active mouth opening exercises and to guide the opening path and memorial exercises as early as possible after operation and upon patient recovery from general anesthesia. Education regarding mouth opening and closing according to the intercuspation of IOS was continued at every follow-up in outclinic. In general, TMJ splint management could provide stability in his or her own occlusion to individual patient by offering a new position for the masticatory muscles and TMJ [16]. Compared with the conventional occlusal splint, this IOS could be thought as one of the thickened centric occlusion-guided splints. A thickness could be determined as postoperative mouth opening status of each patient, but at least 3.0 mm on both anterior and posterior teeth. Stable occlusion is essential for the adaptable position of the mandible and restoration of normal jaw functions by avoiding any neuromuscular imbalance in TMJ splint management. Therefore, IOSs used in physiotherapy after TMJ ankylosis operation relax previously contraction-related muscles and provide occlusal stabilization, thereby maintaining the stability of a newly organized gap in the TMJ (Fig. 7).
Mandibular opening induced by IOS thickness is accompanied by an increase in the joint space, and this space is expected to prevent any relapse potential. Ettlin et al. [17] reported that disc space could be increased on using a 3-mm-thick occlusal splint. By mouth closing and sliding mandible exercises with occlusal splint, a new oriented condyle-fossa relationship would be made without an intentional trial. Liu et al. [18] reported that the occlusal splint is useful in the mandibular condyle fracture child for good remodeling and keeping growth potentials. Additional protection disc space from secondary irritation could be acquired by shifting the condyle to lower location with the occlusal splint. Like these previous reports, IOS would change the condyle-fossa relationship, which could prevent re-attachment and help the resected surface of the condyle and fossa to be reorganized after surgical interventions. One patient showed the potential capacity of these splints to cause anterior open bite, as reported occasionally in the literature [19, 20]. Partially covering splints have been reported to induce occlusal modifications, including anterior open bite [21]. However, the patients in this study wore splints that covered all occlusal surfaces. Thus, these alterations are more likely due to positional changes in the condyle and fossa [22] as a possible consequence of the change in masticatory muscle activity [23], different distribution of occlusal load, or modifications in the vertical dimension [24, 25].
Consequently, postoperative active mouth opening and closing exercises are necessary for avoiding recurrent re-ankylosis. Furthermore, the use of an IOS is effective for guidance of comfortable mouth closing movements during active physiotherapy. After physiotherapy, new fibrous tissue might be formed at the gap space between resected condylar head and previously ankylosed temporal fossa through physiological adaptation. IOS acts as a guide for mouth opening exercises, enables more comfortable mandibular movement, and facilitates occlusal stabilization, thereby helping active postoperative physiotherapy.
