Mandibular midline distraction using a simple device

Mandibular midline distraction using a simple device Sina Uckan, DDS, PhD,a Nurhan Guler, DDS, PhD,b Ayca Arman, DDS, PhD,c and Necip Mutlu, DDS, PhD,d Ankara, Istanbul, and Konya, Turkey BASKENT UNIVERSITY, YEDITEPE UNIVERSITY, AND SELCUK UNIVERSITY FACULTY OF DENTISTRY

Objective. Mandibular midline distraction osteogenesis represents a new option for creation of intra-arch space in the mandibular arch. The aim of this paper is to introduce a simple device (hyrax expander) and method for mandibular midline distraction. Study design. The sample consisted of 24 patients (mean age: 18.07 years) treated with mandibular midline distraction. Hyrax expanders were used as symphyseal distractors, and distraction procedure was carried out with a rate of 1 mm and rhythm of twice daily. Results. Mandibular midline distraction was completed successfully in all patients and the distraction amount was 7.01 mm. No major complication other than mild mucosal irritation and gingival recession was observed. Conclusion. The presented method is a viable option for mandibular midline distraction osteogenesis. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;101:711-7)

Transverse maxillary or mandibular deficiency and crowding of the anterior teeth are problems shared by most orthodontic patients. Both nonsurgical and surgically assisted rapid maxillary expansion are considered viable options for creating additional space in the maxillary dental arch.1-3 In contrast, use of orthodontic mandibular arch expansion techniques has been limited owing to the high risk of relapse when mandibular intercanine width is increased by orthodontic means.4,5 Therefore, most patients with transverse mandibular deficiency and dental crowding are treated with extractions or interproximal reduction of teeth instead of methods that do not involve extraction which might provide a better esthetic outcome. Symphyseal mandibular osteotomy has been proposed as a solution for correcting transverse mandibular deficiency; however, this technique has not been widely accepted owing to risk of periodontal problems, lack of adequate rigid fixation, requirement for graft use, and high risk of relapse.6 Mandibular widening by distraction osteogenesis (DO), a relatively new procedure, offers another treatment option for the orthodontist. Guerrero7 pioneered

a

Professor, Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Baskent University. b Associate Professor, Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Yeditepe University. c Assistant Professor, Deparment of Ortodontics, Faculty of Dentistry, Baskent University. d Associate Professor, Deparment of Oral and Maxillofacial Surgery, Selcuk University Faculty of Dentistry (deceased). Received for publication Apr 1, 2005; returned for revision May 12, 2005; accepted for publication Jun 10, 2005. 1079-2104/$ - see front matter Ó 2006 Mosby, Inc. All rights reserved. doi:10.1016/j.tripleo.2005.06.030

the use of rapid surgical mandibular expansion for correcting mandibular transverse discrepancies. Later work by Guerrero and coworkers8 showed that mandibular symphyseal DO, using both tooth-borne and bone-borne expansion devices, is an effective surgical alternative to orthognathic surgery in the treatment of transverse mandibular deficiency. Animal research has shown that bone segment movement and dental tipping are disproportional; specifically, that teeth move roughly twice as much as bone segments when tooth-borne DO devices are used.9,10 In this article, we introduce a simple device for mandibular midline DO in patients with transverse mandibular deficiency. PATIENTS AND METHODS To date, we have used this new method in 24 patients (mean age 18.07 years) with mandibular arch length deficiency (1 case is detailed below) (Fig. 1, A). The surgical procedure for mandibular symphyseal DO was the one described by Guerrero et al.8 Operations were performed by the 2 surgeons, with the patient under local anesthesia and sedation. First, a horizontal incision was made from the mucogingival reflection extending from the right mandibular canine to the left mandibular canine. A full-thickness mucoperiosteal flap was elevated inferiorly, and the symphysis was completely degloved, including the inferior border. At the midline, a tunnel was made beneath the attached gingiva, extending to the gingival margin. Then an osteotomy was performed between the central incisors using a bone bur and reciprocating saw (Fig. 1, B). No parasagittal cuts were made in any of the cases. The device is a hybrid distractor that consists of 4 arms (hyrax type expander). The end of each arm is bent to form a loop to allow attachment of wires and screws (Fig. 1, A). Each superior 711

OOOOE June 2006

712 Uckan et al.

Table I. Mean age of the patients, distraction protocole, amount of distraction achieved, and length of the treatment Mean age (years) (mean 6 SD)

Distraction rate and Latency rhythm

18.07 5-7 1 mm/day 2 3 6 3.11 days 0.5 mm

Length Amount of of the distraction treatment Consolida(mm) (months) tion (mean (mean time 6 SD) 6 SD) 2.5 months

7.01 6 1.54

14 6 7.3

Table II. Summary of cephalometric measurements for the reported case Pretreatment Skeletal measurements SNA N perp to A Co-A (eff max length) SNB N perp to B Po-NB Go-Gn (eff mand length) ANB Witts appraisal Go-Gn/S-N ANS-Me Gonial angle Dentoalveolar measurements U1-NA U1/PP L1-NB L1/ML U1/L1 Overjet Overbite Soft tissue measurements UL-E line LL-E line Ns/Sn/Pgs

Fig. 1. The modified hyrax screw and the osteotomy design.

arm of the distractor device was ligatured to a canine and the device fixed in position by inserting standard 2.0 bicortical titanium screws (13 mm length) through the loops of the inferior arms and prepared screw holes prior to the final osteotomy (Fig. 1, C). After a 5-day latency period, the distraction procedure was carried out with a rate of 1 mm and rhythm of twice daily. RESULTS Midline distraction was achieved and arch length discrepency was eliminated without extractions in all patients. The mean distraction amount was

Posttreatment

82 8 4 mm 85 mm 78 8 15 mm 1,5 mm 109 mm 48 4 mm 31 8 68 mm 121 8

85 8 6 mm 93 mm 82.5 8 20 mm 3 mm 120 mm 2,5 8 1 mm 23 8 77 mm 125 8

31/12,5 mm 119 8 32/9 mm 102 8 115 8 8,5 mm 6,7 mm

31/11 mm 116 8 31/9 mm 102 8 115 8 3 mm 3 mm

6,5 mm 11 mm 157 8

1 mm 6 mm 164 8

approximately 7 mm. Distraction protocol and length of the treatment are given in Table I. There were no major complications during distraction, consolidation period, and follow-up. Mild irritation of the lower lip or alveolar mucosa or both, depending on the distractor-bone distance from the bone, was observed nearly in all patients and was not clinically remarkable. Gingival recession was observed in 4 patients. No temporomandibular dysfunction (TMD) symptoms were noted in any of the patients during and after the treatment period. REPRESENTATIVE CASE PRESENTATION One of the patients was a 13-year-old boy who was in the MP3 stage of pubertal growth. In the predistraction

OOOOE Volume 101, Number 6

Uckan et al. 713

Fig. 2. Extraoral and intraoral photographs and panoramic radiographs of the patient before treatment.

orthodontic phase, a 1-1.5 mm gap was created between the central incisors. Operations mentioned above were performed by the same surgeon under local anesthesia and sedation. Clinical examination revealed normal jaw function with no signs of temporomandibular dysfunction. The soft-tissue profile was convex and there was lip incompetence. The patient exhibited a skeletal class I, dental class II relationship with a narrow mandibular arch, buccal nonocclusion, 8.5 mm overjet, 6.7 mm overbite, and protrusive upper and lower incisors. The maxillary and mandibular arch length discrepancies were 2.5 mm and 9 mm, respectively. There were profound caries in the maxillary right first molar, and the maxillary left premolar had been extracted. The mandibular right second premolar was impacted (Fig. 2, Table II). The treatment plan was to extract the maxillary right first molar and close the extraction spaces using moderate anchorage. Mandibular midline distraction was planned to address the mandibular crowding and buccal nonocclusion. The patient’s upper

first molars were extracted and both arches were bonded. The maxillary extraction spaces were closed using Ni-Ti coil springs. The brackets on the lower central incisors were positioned such that the roots would be shifted away from the osteotomy line. Six months after placement of the coil springs, the distraction device was placed for mandibular midline DO following the steps detailed above. After a 5-day latency period, the distraction process was started at rate 1 mm and rhythm twice daily. The mandible was widened approximately 8 mm (Fig. 3). After a consolidation phase of 12 weeks, postdistraction orthodontic treatment was initiated. The passive coil spring between the lower central incisors was shortened and the push coil-spring between the mandibular right first molar and first premolar was activated to create space for the second premolar. The postdistraction phase of treatment lasted 14 months, making a total treatment time of 21 months. By the end of treatment, the patient’s mandibular interpremolar width had increased from 25.2 mm to

714 Uckan et al.

OOOOE June 2006

Fig. 3. Extraoral and intraoral photographs and panoramic radiographs of the patient after mandibular midline distraction.

36.8 mm, the mandibular crowding had been eliminated (no extractions necessary), and incisors were less protrusive. A favorable occlusal outcome was achieved with acceptable interdigitation, and the patient’s soft-tissue profile was more balanced (Figs. 4 and 5). The patient had no symptoms of temporomandibular dysfunction at the end of active treatment. Hawley retainers were applied for retention. DISCUSSION Mandibular symphyseal DO can be performed to increase the transverse dimension of the mandibular basal bone if the aim is to correct arch length deficiency by expanding the basal bone.8,9,11 Arch wire expansion, Schwarz plates, and proclination can all produce alveolar expansion; however, studies suggest that this mode of expansion has limited long-term stability and can cause undesirable side effects.12,13

Distraction is particularly effective at resolving anterior crowding because the osteotomy is very close to the space deficiency. The location and orientation of the distraction force are of fundamental importance because they can influence the shape of the distraction gap. Theoretically, if the force is applied near the center of resistance of the mandible, the distraction will result in pure translation of the segments, and the distraction gap will have parallel margins. However, if the force is applied above the center of resistance, each segment may rotate, resulting in a disproportionally larger gap in the dentoalveolar area than in the basal area.9,10 Studies have indicated that tooth movement through regenerate occurs faster than movement through normal host bone. One of the disadvantages of appliances that are strictly tooth borne is that they produce a V-shaped regenerate that may be unstable and prone to relapse. As noted, animal studies have shown that movement

OOOOE Volume 101, Number 6

Uckan et al. 715

Fig. 4. Extraoral and intraoral photographs and panoramic radiographs of the patient after all phases of treatment.

of bone segments and dental tipping do not match; that is, teeth moved approximately twice as far as bone segments when tooth-borne DO devices were used.14 Del Santo et al.15 evaluated the effects of mandibular symphyseal DO by tooth-borne expansion device in 20 nonsyndromic patients. They concluded that the expansion potentially produced the disproportionate distraction patterns, and they observed postsurgical proclination of the mandibular incisors. Bone-borne devices for mandibular widening produce a parallel regenerate and proportional widening of the dento-osseous segments. Procedures in mandibular basal bone is expanded in proportion to alveolar bone are believed to provide greater stability. One of the most important potential side effects of mandibular DO is alteration of temporomandibular joint function. Harper et al.16 studied the impact of a tooth-borne appliance for mandibular symphyseal DO in monkey’s mandibular condyle. They found that the

histologic changes in the condyles were minor, limited to atypical morphology. Using computer modeling, Samchukov and colleagues17 showed lateral rotational movement of the condyles subsequent to mandibular widening, and reported 0.34-degree condylar rotation for every 1 mm of widening at the mandibular midline. Results of 24 patients treated with this new device for mandibular widening are similar to those noted in other short- and long-term studies,8,11,18-21 and all patients had no temporomandibular joint symptoms after DO. Fortunately, the human temporomandibular condyle is known to have some degree of physiologic adaptability. CONCLUSIONS The outcomes and advantages of this new device may be summarized as follows. 1. No loss of crestal bone height or loss of tooth vitality.

716 Uckan et al.

OOOOE June 2006

Fig. 5. Pretreatment and posttreatment cephalometric radiographs and superimpositions of the case based on the structural method of Bjo¨rk.

2. To avoid damaging anatomic structures the long arms of the distractor can be easily adapted during the surgical procedure. 3. No specific instrument other than orthodontic pliers is required to modify the device. 4. The hybrid form of the distractor ensures that the edges of the symphyseal distraction gap will be parallel. 5. The device is cheap and can be easily applied in an office setting. REFERENCES 1. Wertz R, Dreskin M. Midpalatal suture opening: a normative study. Am J Orthod 1977;71:367-81. 2. Bell WH, Epker BN. Surgical orthodontic expansion of the maxilla. Am J Orthod 1976;70:517-28. 3. Handelman CS, Wang L, BeGole EA, Haas AJ. Nonsurgical rapid maxillary expansion in adults: report on 47 cases using the Haas expander. Angle Orthod 2000;70:129-14. 4. Reidel RA. A review of the retention problem. Angle Orthod 1960;30:179-94.

5. Profitt WR, Ackerman JL. Diagnosis and treatment planning in orthodontics. In: Graber TM, Vanarsdall RL, editors. Orthodontics: current principles and techniques. 2nd ed. Philadelphia: MosbyeYear Book; 1994. p. 3-95. 6. Guerrero C, Contasti G. Transverse (horizontal) mandibular deficiency. In: Bell WH, editor. Modern practice in orthognathic and reconstructive surgery. Philadelphia: Saunders; 1992. p. 2383-97. 7. Guerrero CA. Rapid mandibular expansion. Rev Venez Orthod 1990;48:1-4. 8. Guerrero CA, Bell WH, Contasti GI, Rodriguez AM. Mandibular widening by intraoral distraction osteogenesis. Br J Oral Maxillofac Surg 1997;35:383-92. 9. Bell WH, Harper RP, Gonzalez M, Cherkashin AM, Samchukov ML. Distraction osteogenesis to widen the mandible. Br J Oral Maxillofac Surg 1997;35:11-9. 10. Hollis BJ, Block MS, Gardiner D, Chang A. An experimental study of mandibular arch widening in the dog using distraction osteogenesis. J Oral Maxillofac Surg 1998;56:330-8. 11. Weil TS, Van Sickels JE, Payne CJ. Distraction osteogenesis for correction of transverse mandibular deficiency: a preliminary report. J Oral Maxillofac Surg 1997;55:953-60. ˚ rtun J. An evaluation of changes in 12. Little RM, Riedel RA, A mandibular anterior alignment from 10 to 20 years postretention. Am J Orthod Dentofacial Orthop 1988;93:423-8. 13. Sadowsky C, Sakals EI. Long-term assessment of orthodontic relapse. Am J Orthod 1982;82:456-63.

OOOOE Volume 101, Number 6 14. Bell WH, Gonzalez M, Samchukov ML, Guerrero CA. Intraoral widening and lengthening of the mandible in baboons by distraction osteogenesis. J Oral Maxillofac Surg 1999;57: 548-62. 15. Del Santo M, Guerrero CA, Buschang PH, English JD, Samchukov ML. Long-term skeletal and dental effects of mandibular symphyseal distraction osteogenesis. Am J Orthod Dentofacial Orthop 2000;118:485-93. 16. Harper RP, Bell WH, Hinton RJ, Browne R, Cherkashin AM, Samchukov ML. Reactive changes in the temporomandibular joint after mandibular midline osteodistraction. Br J Oral Maxillofac Surg 1997;35:20-5. 17. Samchukov ML, Cope JB, Harper RP, Ross JD. Biomechanical considerations of mandibular lengthening and widening by gradual distraction using a computer model. J Oral Maxillofac Surg 1998;56:51-9. 18. Kewitt GF, Van Sickels JE. Long-term effect of mandibular midline distraction osteogenesis on the status of the temporomandibular joint, teeth, periodontal structures, and neurosensory function. J Oral Maxillofac Surg 1999;57:1419-25.

Uckan et al. 717 19. Braun S, Bottrel A, Legan HL. Condylar displacement related to mandibular symhyseal distraction. Am J Orthop Dentofacial Orthop 2002;121:162-5. 20. Orhan M, Malkoc S, Usumez S, Uckan S. Mandibular symphyseal distraction and its geometrical evaluation: report of a case. Angle Orthod 2003;73:194-200. 21. Basciftci FA, Korkmaz HH, Iseri H, Malkoc S. Biomechanical evaluation of mandibular midline distraction osteogenesis by using the finite element method. Am J Orthod Dentofacial Orthop 2004;125:706-15. Reprint requests: Nurhan Guler, DDS, PhD Disx Hekimligi Fakultesi ¨ niversitesi Yeditepe U Bagdat cad. No:238 Goztepe Istanbul Turkey [email protected]