CRANIOMAXILLOFACIAL DEFORMITIES/COSMETIC SURGERY

Digital Occlusal Splint for Condylar Reconstruction in Children With Temporomandibular Joint Ankylosis Chuan Lu, DDS,* Dong Huang, DDS,y Dongmei He, DDS, MD,z Chi Yang, DDS, MD,x and Jianbing Yuank Purpose:

A costochondral graft (CCG) is usually used for condylar reconstruction in children with temporomandibular joint (TMJ) ankylosis. The aim of the present study was to introduce the application of a digital occlusal splint (DOS) in the assistance of CCG to treat ankylosis and mandibular deviation simultaneously.

Materials and Methods:

We designed and implemented a retrospective cohort study and enrolled a sample of growing pediatric patients with unilateral TMJ ankylosis and mandibular deviation who were treated for CCG at our department. The predictor variable was preoperative three-dimensional treatment planning and splint construction (DOS) compared with intraoperative treatment planning and splint fabrication (conventional occlusal splint [COS]). The primary outcome variables were the postoperative ramus height and chin deviation correction measured using Proplan CMF, version 1.3 software. The secondary outcome variable was the treatment time. Data from the 2 methods were compared using the Statistical Package for Social Sciences software package, version 13.0.

Results:

A total of 8 children, 4 with a COS and 4 with a DOS were included in the present study. The treatment time was significantly longer in the COS group (mean 9.625 hours) than in the DOS group (mean 6.75 hours). The ramus height and chin deviation correction after surgery were more accurate in the DOS group (mean 2.09 mm and 1.29 , respectively) than in the COS group (mean 5.44 mm and 3.27 , respectively) but without significance (P > .05).

Conclusions: The preoperative fabrication of DOSs compared with the intraoperative fabrication of COSs resulted in a shorter treatment time and improved mandibular deviation correction in the treatment of children with unilateral TMJ ankylosis. Ó 2014 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg -:1-9, 2014

Temporomandibular joint (TMJ) ankylosis is a severe disease that destroys the normal TMJ structure, causes

restricted mouth opening, and affects the daily functions of speech, mastication, and oral hygiene. In a

*Resident, Department of Oral Surgery, Ninth People’s Hospital,

08DZ2271100, 13XD1402300); the Health and Welfare Industry,

Shanghai Jiao Tong University School of Medicine, Key Laboratory

Research and Special Project Funding; the Program for Innovative

of Stomatology, Shanghai, China.

Research Team of Shanghai Municipal Education Commission; the

yResident, Department of Oral Surgery, Ninth People’s Hospital,

Scientific Research Foundation for Returned Overseas Chinese

Shanghai Jiao Tong University School of Medicine, Key Laboratory of Stomatology, Shanghai, China.

Scholars, and the State Education Ministry. Drs Lu and Huang contributed equally to this study.

zAssociate Professor, Department of Oral Surgery, Ninth People’s

Address correspondence and reprint requests to Dr He: Depart-

Hospital, Shanghai Jiao Tong University School of Medicine, Key

ment of Oral and Maxillofacial Surgery, Shanghai Ninth People’s Hos-

Laboratory of Stomatology, Shanghai, China.

pital, Shanghai Jiao Tong University School of Medicine, 639 Zhi Zao

xProfessor, Department of Oral Surgery, Ninth People’s Hospital,

Ju Road, Shanghai 200011, China; e-mail: dongmeihe119@yahoo

Shanghai Jiao Tong University School of Medicine, Key Laboratory of

.com

Stomatology, Shanghai, China.

Received September 20 2013

kEngineer, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China.

Ó 2014 American Association of Oral and Maxillofacial Surgeons

Accepted December 27 2013

The present work was supported by the National Natural Science

0278-2391/14/00069-X$36.00/0

Foundation of China (grant 81070848); the Research Fund of Sci-

http://dx.doi.org/10.1016/j.joms.2013.12.033

ence and Technology Commission of Shanghai Municipality (grants

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DIGITAL OCCLUSAL SPLINT FOR CONDYLAR RECONSTRUCTION IN CHILDREN

growing child, it affects the development of the mandible, resulting in facial deformity, malocclusion, and obstructive sleep apnea-hypopnea syndrome. According to our previous study,1 for the type of ankylosis without a residual condyle displaced medially, reconstruction of the ramus–condyle unit (RCU) is needed. A number of different methods are available to reconstruct the RCU, including distraction osteogenesis (DO) or costochondral graft (CCG) placement, reported by Kaban et al2 in 2009 for children. However, few have reported on the use of the occlusal splint as a navigation guide to correct the associated mandibular asymmetry. Our protocol to treat TMJ ankylosis with jaw bone deformities in children has been to remove the bony fusion first and then use the CCG to restore the ramus height and correct the chin deviation. An occlusal splint is needed to reposition the mandible in the ideal position by intermaxillary fixation (IMF) during bone grafting. Because the ankylosis patient usually has restricted mouth opening, an occlusal impression cannot be taken before surgery. It must occur during surgery after joint fusion release, then the impression of the teeth can be taken, and the positioning splint can be fabricated. It takes time and the accuracy is not guaranteed. To solve these problems, we used computer-assisted techniques (CAS) to measure the deformities and simulate the mandible rotation along the unaffected condyle to correct the chin point. A wafer was then designed between the upper and lower teeth and manufactured using rapid prototyping technology. This was termed a ‘‘digital occlusal splint’’ (DOS). The purpose of the present study was to report the preliminary application of DOS in the treatment of children with unilateral TMJ ankylosis. We hypothesized that the preoperative fabrication of DOS compared with the intraoperative fabrication of the splint (conversional occlusal splint [COS]) could save treatment time and improve the accuracy of mandibular deviation correction. The specific aims of the present study were to compare preoperative digital planning and fabrication of a DOS as a navigation guide to intraoperative assessment and management of the skeletal deformity.

Materials and Methods STUDY DESIGN

To address our research purpose, we designed and implemented a retrospective study that was approved by the local ethics board of the hospital. The study population included of all children presenting with unilateral TMJ ankylosis at our department for evaluation and management of chin deviation from January 2008 to December 2012 (Fig 1). To be included in

FIGURE 1. Female patient, age 3 years, with a mouth opening limitation for 2 years after a fall. (Permission provided by the child’s parents.) Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

the study sample, the patients had to have been treated with a CCG to reconstruct 1 RCU using either a COS or DOS and treated by 1 surgeon. The patients were excluded as study subjects if 2 RCUs had been reconstructed with CCG. VARIABLES

The predictor variable was preoperative 3-dimensional (3D) treatment planning and splint construction (DOS) compared with intraoperative treatment planning and splint fabrication (COS). The primary outcome variables were the postoperative ramus height and chin deviation correction. The secondary outcome variable was the treatment time (preoperative design plus intraoperative time in the DOS group and intraoperative time alone in the COS group). DATA COLLECTION METHODS

DOS Design and Manufacture The patients’ preoperative computed tomography (CT) scans were stored (layer thick 0.625 mm) on a disc as Digital Imaging and Communications in Medicine and then imported into the computer to perform the 3D reconstruction using ProPlan CMF, version 1.3 (Materialise Medical, Leuven, Belgium), software. After

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LU ET AL

defining the facial midline and Frankfort plane, the heights of the bilateral ramus (distance between the gonion and condylion) and chin deviation (distance and angle between the gnathion and sagittal plane) were measured (Fig 2). Using the software, the maxilla

and mandible were easily separated, an osteotomy of the affected TMJ was simulated, and the osteotomy depth was measured (Fig 3). After the osteotomy, the mandible was relocated to eliminate the chin deviation by rotating along the unaffected TMJ condylion. This

FIGURE 2. Three-dimensional (3D) measurement of preoperative computed tomography scan. A, Frontal view showing chin deviation to the left. B, Lateral view showing temporomandibular joint bony fusion and shortened mandibular ramus. ANS, anterior nasalspine; Ba, basion; CoL, condyle left; CoR, condyle right; Gn, gnathion; GoL, gonion left; GoR, gonion right; Mid Po, middle point of left and right porion; MoL, molar left; MoR, molar right; N, nasion; OrL, orbitale left; OrR, orbitale right; PoL, porion left; PoR, porion right. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

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DIGITAL OCCLUSAL SPLINT FOR CONDYLAR RECONSTRUCTION IN CHILDREN

FIGURE 3. The dimension of bony fusion was 17.63 mm using 3-dimensional measurement. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

should be within the rotation ability of the condyle, which should be no more than 10 (Fig 4). CCG was used to reconstruct the affected ramus. A wafer was designed between the upper and lower teeth gap as DOS (Fig 5A), which was a navigation guide for the bone graft to correct the mandibular asymmetry. The last step was to export the relocated 3D image in stl format and manufacture the DOS using rapid prototyping technology (Fig 5B). COS Design and Manufacture The COS was made during surgery after bony fusion removal. The teeth impression was taken, and a dental cast was made when the mouth could be opened normally. The mandible was moved to the unaffected side to correct the chin deviation. Wax was put in the gap between the maxillary and mandibular teeth on the affected side to help reposition the mandible. The occlusion was transferred to the dental articulator, and the COS was then made as described by Behnia et al.3 SURGICAL PROCEDURES

All patients in the 2 groups underwent TMJ reconstruction with CCG surgery treated by 1 surgeon. The bony fusion was exposed by preauricular incision. After removal of the bony fusion, the coronoid process, and releasing the masticatory muscle, the mouth opening should be at least 35 mm. The mandible was then rotated along the unaffected condyle to correct the chin deviation (Fig 6A). The DOS or COS was used to keep an open bite on the affected side for

IMF (Fig 7A). The CCG was grafted to reconstruct the ramus condyle unit with 1 titanium plate and at least 3 bicortical screws for fixation (Fig 6B). A plastic splint with clasps was made for long-term wearing in both DOS and COS groups after surgery. The splint was ground gradually to stimulate growth of the maxilla on the affected side.

STATISTICAL ANALYSIS

The clinical and imaging evaluations were performed within 1 week after surgery. The clinical evaluation included chin deviation. CT was used for imaging evaluation. Using the ProPlan CMF, version 1.3, software to process the CT data, 3 variables were measured in both DOS and COS groups before and after surgery: chin deviation (the distance between the gnathion and sagittal plane), the angle of the deviation (the angle between the nasion–gnathion line and the facial midline), and the bilateral ramus heights (the distance between the gonion and condylion). The chin deviation and ramus height differences after surgery in the DOS and COS groups were compared for accuracy. The treatment time of the 2 groups was analyzed using the Statistical Package for Social Sciences software package, version 13.0 (SPSS, Chicago, IL) and the Student t test. Data on the chin deviation and bilateral ramus heights measured from CT scanning in both DOS and COS groups before and after surgery were compared using the paired t test. The postoperative results were compared between the DOS and COS

LU ET AL

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FIGURE 4. Preoperative design imitating bony fusion removal and mandible correction. A, Frontal view showed mandible correction. B, Lateral view showed ramus elongation. ANS, anterior nasalspine; Ba, basion; CoL, condyle left; CoR, condyle right; Gn, gnathion; GoL, gonion left; GoR, gonion right; Mid Po, middle point of left and right porion; MoL, molar left; MoR, molar right; N, nasion; OrL, orbitale left; OrR, orbitale right; PoL, porion left; PoR, porion right. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

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DIGITAL OCCLUSAL SPLINT FOR CONDYLAR RECONSTRUCTION IN CHILDREN

FIGURE 5. Digital occlusal splint. A, Design. B, Occlusal splint from 3-dimensional print. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

groups using 1-way analysis of variance. An a level of #0.05 was considered significant.

Results A total of 8 children who had unilateral TMJ ankylosis with mandibular deviation were included in the

study. Of the 8 children, 5 were boys and 3 were girls, with a mean age of 5.5 years (range 3 to 8). Of the 8 patients, 4 had a DOS made using the computer-aided design/computer-aided manufacturing technique to guide the bone graft, and 4 had the COS made during surgery after bony fusion removal. Their general information and operative time are listed in Table 1.

FIGURE 6. Intraoperative imaging. A, Bony fusion removal. B, Costochondral graft. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

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FIGURE 7. A, Digital occlusal splint wearing during surgery. B, Resin occlusal splint postoperatively. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

DOSs worked successfully during surgery, fitting the upper and lower teeth perfectly, without any interference or deformation. The DOS and COS patients all recovered with a symmetric face (Figs 8, 9). A group t test showed that the treatment time was longer in the COS group (mean 9.625 hours) than that in the DOS group (mean 6.75 hours) (P < .05; Table 2). A statistical significance was found in the height of the ramus, deviation of the chin, and angle of the deviation before and after surgery in both DOS and COS groups (P < .05; Table 3). There were no significant deformity differences between DOS and COS groups preoperatively (P >.05; Table 4). The correction of the ramus height and chin deviation postoperatively was more accurate in the DOS group (mean 1.85 mm, 2.09 mm and 1.29 ) than that in the COS group (mean 4.25

Table 1. GENERAL PATIENT INFORMATION

Study Variable Total patients (n) Male patients (n) Age (yr) Range Mean History (yr) Range Mean Affected joint side (n) Left Right Type of occlusal splint (n) DOS COS

Value 8 5 3-8 5.5 1-6 3 6 2 4 4

Abbreviations: COS, conventional occlusal splint; DOS, digital occlusal splint; TMJ, temporomandibular joint. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

mm, 5.44 mm and 3.27 ) but without significance (P > .05; Table 5).

Discussion We have presented our experience using DOS by CAS as a guide for CCG to manage mandibular asymmetry and evaluated its effects. Thus, the treatment time was considerably reduced, and the correction of the chin deviation was more accurate than with the COS. Children with TMJ ankylosis often also have jaw bone deformities because of bone growth restriction. The treatment usually includes 2 stages: the first stage, ankylosis release; and the second stage, to correct the jaw bone deformity when the growth has finished. We believe if the 2 stages can be combined into 1 operation, it will shorten the treatment time and lower the cost to the patients. This will also mitigate the adverse effects on the patients’ physical and mental development. We have used CCG for condylar reconstruction, because it can both reconstruct the TMJ and immediately lengthen the affected mandibular ramus. DO is another method to reconstruct the ramus condyle unit.3 We have preferred CCG because 1) it is biologically similar to the condyle; 2) it has good growth potential for children; 3) it contains enough bone, which can offset the insufficient ramus heights; and 4) 1 procedure will be sufficient, with no need for a secondary surgery. Finally, the operative time is short and the cost of the treatment inexpensive. Although reports have stated that the CCG has the potential to overgrow, studies have shown that keeping an appropriate amount of cartilage (approximately 5 mm) can reduce that probability.4 To avoid CCG absorption after grafting, it is necessary to use an aseptic technique and stable fixation (1 titanium plate and at least 3 bicortical screws)5 and reduce the interval between separation and grafting.

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DIGITAL OCCLUSAL SPLINT FOR CONDYLAR RECONSTRUCTION IN CHILDREN

FIGURE 8. Postoperative computed tomography scan. A, Chin correction. B, Ramus height resorted by costochondral graft. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

In the present study, using a DOS can solve the problem of not being able to acquire dental impressions and casts before surgery owing to the restricted mouth

opening caused by TMJ ankylosis. Only 1 hour is required to perform preoperative planning using CAS. Surgeons no longer need to spend at least 2 hours during surgery waiting for splint fabrication. Moreover, using 3D measurements of the whole skull, not only the alveolar bone, the position of the mandible can be rotated more accurately than using 2-dimensional measurements.6 However, CT is less accurate for reflecting the specific features of the teeth compared with the plaster model. The teeth outline on the CT scan will usually not be clear and has often been magnified with some artifacts. It can often be very difficult to segment the upper and lower teeth because of the tight bite. Thus, how to improve the accuracy of DOS will be very important. By adjusting the CT threshold, the size of the teeth can be controlled to normal. In the future, a combination of the data using a laser scan of the teeth could improve the accuracy of the DOS. Currently, it has only been used to ascertain the position of the jaw and assist bone grafting during surgery. Table 2. OPERATIVE TIME FOR BOTH GROUPS

Occlusal Splint DOS COS

Mean Treatment Time (h)

P Value

6.75 9.625

.0027

FIGURE 9. Postoperative photographs showing corrected chin deviation. (Permission provided by the child’s parents.)

Abbreviations: COS, conventional occlusal splint; DOS, digital occlusal splint.

Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

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Table 3. CEPHALOMETRIC CT MEASUREMENTS FOR BOTH GROUPS

Occlusal Splint DOS Ramus height difference (mm) Distance of chin deviation from FM (mm) Angle of chin deviation from FM ( ) COS Ramus height difference (mm) Distance of chin deviation from FM (mm) Angle of chin deviation from FM ( )

Table 5. POSTOPERATIVE MANDIBULAR EFFECTS

Occlusal Splint

P Preoperatively Postoperatively Value

7.74

1.85

.0106

7.94

2.09

.0184

5.10

1.29

.019

Cephalometric Measurement

COS

DOS

P Value

Ramus height difference (mm) Distance of chin deviation from FM (mm) Angle of chin deviation from FM ( )

4.25 5.44

1.85 2.09

.2869 .6664

3.27

1.29

.0588

Abbreviations: COS, conventional occlusal splint; DOS, digital occlusal splint; FM, facial midline. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

14.28

4.25

.0253

12.50

5.44

.0021

8.13

3.27

.0039

Abbreviations: COS, conventional occlusal splint; CT, computed tomography; DOS, digital occlusal splint; FM, facial midline. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

Postoperatively, a plastic splint with clasps can be made for long-term wearing to improve the accuracy and stability of the occlusion and graft. The maxilla can be stimulated to grow downward to eliminate

Table 4. PREOPERATIVE MANDIBULAR DEFORMITIES OF BOTH GROUPS

Occlusal Splint Cephalometric Measurement

COS

DOS

P Value

Ramus height difference (mm) Distance of chin deviation from FM (mm) Angle of chin deviation from FM ( )

14.28 12.50

7.74 7.94

.1806 .0537

8.13

5.10

.0561

Abbreviations: COS, conventional occlusal splint; DOS, digital occlusal splint; FM, facial midline. Lu et al. Digital Occlusal Splint for Condylar Reconstruction in Children. J Oral Maxillofac Surg 2014.

the open bite on the affected side by grinding the splint regularly.7,8 In conclusion, the preoperative fabrication of the DOS compared with intraoperative fabrication of the COS results in a shorter treatment time and improved mandibular deviation correction in the treatment of children with unilateral TMJ ankylosis. This method has good prospects for clinical application.

References 1. He D, Yang C, Chen M, et al: Traumatic temporomandibular joint ankylosis: Our classification and treatment experience. J Oral Maxillofac Surg 69:1600, 2011 2. Kaban LB, Bouchard C, Troulis MJ: A protocol for management of temporomandibular joint ankylosis in children. J Oral Maxillofac Surg 67:1966, 2009 3. Behnia H, Motamedi MH, Tehranchi A: Use of activator appliances in pediatric patients treated with costochondral grafts for temporomandibular joint ankylosis: Analysis of 13 cases. J Oral Maxillofac Surg 55:1408, 1997 4. Perrott DH, Umeda H, Kaban LB: Costochondral graft construction/reconstruction of the ramus/condyle unit: Longterm follow-up. Int J Oral Maxillofac Surg 23(6 Pt 1):321, 1994 5. Qiu YT, Yang C, Chen MJ: Endoscopically assisted reconstruction of the mandibular condyle with a costochondral graft through a modified preauricular approach. Br J Oral Maxillofac Surg 48: 443, 2010 6. Gateno J, Xia JJ, Teichgraeber JF, et al: Clinical feasibility of computer-aided surgical simulation (CASS) in the treatment of complex craniomaxillofacial deformities. J Oral Maxillofac Surg 65:728, 2007 7. Kaban LB, Padwa BL, Mulliken JB: Surgical correction of mandibular hypoplasia in hemifacial microsomia: The case for treatment in early childhood. J Oral Maxillofac Surg 56: 628, 1998 8. Padwa BL, Mulliken JB, Maghen A, et al: Midfacial growth after costochondral graft construction of the mandibular ramus in hemifacial microsomia. J Oral Maxillofac Surg 56: 122, 1998