CASE REPORT Orthodontic treatment and masticatory muscle exercises to correct a Class I open bite in an adult patient Carrie A. Lindsey, DDS, MS,a and Jeryl D. English, DDS, MSb Dallas, Tex iagnosing and treating an open bite malocclusion in an adult is a challenge for the clinical orthodontist. Patients with skeletal vertical growth patterns, typical of open bite malocclusions, exhibit common morphological and functional characteristics, including long anterior face height,1-3 short posterior face height,1,2 large mandibular plane and gonial angles,1,2,4 increased dentoalveolar height,4 marked antegonial notching,5 downward tipping to the posterior maxilla,5,6 and anterior open bite. Functionally, hyperdivergent patients typically have weak bite forces,7,8 and smaller,9-11 less efficient12 muscles. Control of the vertical dimension by intruding both maxillary and mandibular molars and facilitating counterclockwise rotation of the mandible is key to managing open bite malocclusion. Some studies have shown morphological improvements in children with open bites who do chewing exercises,12,13 and others have demonstrated significant forward mandibular autorotation.8,14 In this case report, we discuss open bite treatment that included a combination of anterior vertical elastics to extrude the maxillary and mandibular incisors and clenching exercises to intrude the maxillary and mandibular molars. D HISTORY AND ETIOLOGY The patient was a healthy, 40-year-old woman referred to the Department of Orthodontics clinic by the From the Department of Orthodontics, Baylor College of Dentistry, Dallas, Tex. a Graduate student. b Formerly Clinic Director; Graduate Program Director. Presented at the May 2001 meeting of the American Association of Orthodontists, Toronto, Ontario, Canada. Am J Orthod Dentofacial Orthop 2003;124:91-8 Reprint requested to: Dr Jeryl D. English, Department of Orthodontics, Chairman and Graduate Program Director, University of Texas Health Science Center at Houston, Dental Branch, 6516 M. D. Anderson Blvd, #370, Houston, TX 77030; e-mail, jeryl.d.english@uth.tmc.edu. Submitted, May 2002; revised and accepted, November 2002 Copyright © 2003 by the American Association of Orthodontists. 0889-5406/2003/$30.00 ⫹ 0 doi:10.1016/S0889-5406(03)00308-1 Department of Oral Surgery at Baylor College of Dentistry for combined surgical-orthodontic treatment to correct her open bite. Her medical history included a rhinoplasty in 1986, a past history of bulimia, and a penicillin allergy. Her daily medications included birth control pills, melatonin (as a sleep aid), and Excedrin (for daily sinus headaches and temporomandibular joint [TMJ] pain). The patient reported undergoing previous comprehensive orthodontic therapy in 1972 and said that her bite had been opening over the last 10 years. She reported wearing numerous occlusal splints in attempt to control TMJ pain. Radiographs of her mandibular condyles did not indicate that a resorptive process was responsible for the bite opening. It was speculated that the bite splints did not extend to the second molars, and this resulted in supereruption and progressive bite opening. The patient reported severe TMJ pain on the right side when biting, but her range of motion during a clinical examination was normal. The right maxillary and mandibular second molars were the only teeth in occlusion, and the forces of mastication concentrated on these teeth probably contributed to the reported TMJ pain. DIAGNOSIS A Class I open bite was diagnosed. Facial analysis showed a leptoprosopic facial form, a mild deviation of the nose to the right, a long lower face height, a deficient gingival display, a convex overall profile, and a prominent chin (Fig 1). Dentally, the open bite was 8 mm, and the overjet was 2 to 3 mm (Figs 2 and 3). There was no crowding in the maxillary arch and only about 1 mm of crowding in the mandibular arch. The mandibular arch had a reverse curve of Spee of approximately 4 mm. Because of the mildly small maxillary lateral incisors, a Bolton discrepancy of 1.6 mm anterior mandibular excess existed. Mild gingival recession and multiple cervical enamel lesions were present. Probing depths around the molars were 5 mm, and horizontal bone loss was evident on the radiographs (Fig 4), although oral hygiene was excellent, with no signs of active inflammation. Cephalometric analysis 91 92 Lindsey and English American Journal of Orthodontics and Dentofacial Orthopedics July 2003 Fig 1. Pretreatment facial photographs. Fig 2. Pretreatment intraoral photographs. showed a Class II skeletal tendency with an ANB angle of 4° due mostly to clockwise mandibular rotation resulting from second molar supereruption (Fig 5, Table). Both maxillary and mandibular incisors were mildly upright. TREATMENT PLAN The initial plan consisted of combined orthodontic treatment and orthognathic surgery to correct the open bite malocclusion. Both arches were to be banded or bonded from second molar to second molar with 0.022 ⫻ 0.028-in appliances. With continuous archwires, leveling and alignment would be accomplished in preparation for orthognathic surgery. A segmental Le Fort I maxillary surgery and a bilateral sagittal split osteotomy mandibular advancement (as needed) were planned to close the open bite. After surgery, the occlusion would be detailed and finished. A bonded retainer from canine to canine would be used for retention in the mandible, with a Hawley wrap-around retainer in the maxilla. TREATMENT OBJECTIVES Treatment objectives for the maxilla included maintaining the anteroposterior and transverse dimensions, Lindsey and English 93 American Journal of Orthodontics and Dentofacial Orthopedics Volume 124, Number 1 Fig 3. Pretreatment study models. Fig 4. Pretreatment panoramic radiograph. altering the vertical position through posterior impaction, and repositioning the anterior teeth downward to close the bite and increase incisor show at rest and during smiling. The arch would be leveled by intruding the second molars. Because the patient did not want to restore the narrow lateral incisors, the anteroposterior incisor angulation would be maintained in the mildly upright pretreatment positions. Objectives for the mandible included maintaining the transverse dimension, decreasing the mandibular plane angle, and reducing the lower vertical excess through autorotation during segmental maxillary surgery. The anteroposterior position of the mandible would be coordinated with that of the maxilla during surgery. The anteroposterior and transverse dimensions Fig 5. Pretreatment cephalometric tracing. of the mandibular dentition would be maintained and the reverse curve of Spee leveled through a combination of second molar intrusion and incisor extrusion. Overall goals for the occlusion were to establish a Class I molar and canine relationship with ideal overjet 94 Lindsey and English Table. American Journal of Orthodontics and Dentofacial Orthopedics July 2003 Cephalometric summary Area of study Measurement Norms A B Cranial base N-S-Ba angle S-N SNA angle Maxillary depth SNB angle Facial angle ANB angle N-ANS ANS-Me N-Me FMA angle Interincisal angle U1/SN L1/Go-Me L1/N-B Nasolabial angle 130° 69 mm 82° 90° 79° 86° 3° 50 mm 62 mm 118 mm 23° 134° 103° 95° 4 mm 112° 122° 66 mm 80° 90° 76° 87° 4° 51 mm 75 mm 125 mm 27° 134° 99° 88° 4 mm 111° 123° 66 mm 81° 92° 77° 88° 4° 51 mm 69 mm 119 mm 23° 142° 93° 86° 4 mm 117° Maxilla to cranial base Mandible to cranial base Maxillomandibular relationships Vertical height Maxillary and mandibular incisor position Soft tissue and over bite, and to establish centric occlusion coincident with centric relation and a mutually protected occlusion. Decreasing the long lower face height would improve facial balance for this patient and result in some esthetic improvement. TREATMENT PROGRESS The maxillary and mandibular arches were banded and bonded with .022 ⫻ .028-in MBT (3M Unitek, Monrovia, Calif) appliances, and continuous .016-in nickel-titanium archwires were placed. After initial alignment was obtained, continuous .018 ⫻ .025-in BioForce nickel-titanium (GAC, Bohemia, NY) wires were placed for 4 months to continue alignment and begin leveling. As the initial period of leveling began, the patient was instructed to squeeze her teeth together to aid in intruding the second molars. She was extremely compliant with this exercise because she was motivated to speed the treatment process along. Six months into treatment, continuous .019 ⫻ .025-in stainless steel archwires were placed, and the leveling of the arches continued. By about 10 months into treatment, the leveling process had significantly reduced the open bite to approximately 2 mm. Because good progress had been made in closing the bite through orthodontic leveling alone, it was decided to attempt to complete the treatment nonsurgically. A reverse curve of Spee was added to the maxillary archwire and an accentuated curve of Spee was added to the mandibular archwire to continue closing the bite. At the same time, bilateral trapezoid elastics from the maxillary laterals and canines to the mandibular first premolars, canines, and A to B difference 1° 0 mm 1° 2° 1° 1° 0° 0 mm ⫺6 mm ⫺6 mm ⫺4° ⫺8° ⫺6° ⫺2° 0 mm ⫺6° laterals were initiated (3⁄16-in, 6 oz, Ormco, Orange, Calif). Throughout treatment, the patient continued with the squeezing exercise. After 1 month of elastic wear with the curved archwires in place, the open bite was reduced to 0 mm. An .018 ⫻ .025-in D-Rect (Ormco) stainless steel archwire was placed in the maxillary arch to facilitate extrusion of the maxillary anterior teeth to improve incisor show on smiling. Fulltime elastic wear continued for 4 months, tapered to night only for 1 month, and then stopped. The upper archwire was sectioned, and finishing elastics (3⁄4-in, 2 oz) were used for approximately 5 weeks. Appliances were removed, and retainers were delivered. Cooperation was excellent, and the patient reported no TMJ problems during treatment. TREATMENT RESULTS Facial esthetics and balance were improved by decreasing lower face height through mandibular autorotation (Figs 6-11). The maxillary incisors were retroclined and retruded as the anterior open bite was closed. The maxillary second molar was intruded approximately 2 mm. The transverse was maintained, and, other than the mild incisor retrusion, the anteroposterior dental positions were maintained. The anteroposterior position of the mandibular molars was maintained while the incisors were retroclined 2°. The transverse dimension was maintained. In the vertical dimension, the second molar was intruded about 1 mm and the incisors extruded about 2.5 mm as the reverse curve of Spee was leveled. Class I molar and canine relationships with ideal overjet and overbite were established. Centric occlusion was established to be coincident with Lindsey and English 95 American Journal of Orthodontics and Dentofacial Orthopedics Volume 124, Number 1 Fig 6. Posttreatment facial photographs. Fig 7. Posttreatment intraoral photographs. centric relation, and a mutually protected occlusion was designed. Transverse and vertical dimensions were maintained in the maxilla. A-point came forward about 1° as the maxillary incisors were uprighted. The transverse dimension was maintained in the mandible, and the mandibular plane angle decreased 4° as the mandible rotated counterclockwise after intrusion of the maxillary and mandibular second molars. Lower face height decreased 6 mm to a more balanced relationship. The anteroposterior positions of B-point and pogonion advanced about 1° as the mandible autorotated forward. FINAL EVALUATION The final outcome of the treatment is a great improvement in function and esthetics, but stability of the open bite closure is questionable. If the etiology of the open bite was molar supereruption during years of wearing poorly constructed splints, the result might remain fairly stable. The main reason this patient could be treated nonsurgically was her excellent compliance. She wore the elastics full time, and she performed the squeezing exercises daily, enabling the orthodontic intrusion of the second molars. 96 Lindsey and English American Journal of Orthodontics and Dentofacial Orthopedics July 2003 Fig 8. Posttreatment study models. Fig 9. Posttreatment panoramic radiograph. DISCUSSION The difficulty of managing anterior open bite malocclusions is not only in obtaining the correct diagnosis, but also in treating the case to a successful facial and dental result. The orthodontist’s challenge is to minimize molar extrusion during treatment to prevent downward and backward mandibular rotation. Faced with the limitations that routine orthodontic treatment modalities present, most orthodontists would agree that a skeletal hyperdivergent open bite malocclusion in an adult is ideally corrected with combined orthodontic treatment and orthognathic surgery. The most common surgical procedure is a LeFort I osteotomy, which allows impaction of the posterior maxilla and autorotation of the mandible.15 This patient was Fig 10. Posttreatment cephalometric tracing. hesitant to consent to the orthognathic surgical plan because of the additional expense and risks of surgery. The advantages of the orthognathic surgical option are that the overbite can be overcorrected and relapse is less than with a nonsurgical approach.16 Lindsey and English 97 American Journal of Orthodontics and Dentofacial Orthopedics Volume 124, Number 1 Fig 11. Superimposed cephalometric tracings. Nonsurgical options for correcting open bite malocclusions include anterior vertical elastics, posterior bite blocks (active and passive), high-pull headgear, vertical pull chincups, and microimplants. Nonsurgical options usually require longer treatment time and more patient compliance. A common nonsurgical treatment option would be to use anterior vertical elastics to extrude the maxillary and mandibular incisors and close the anterior open bite. This procedure would be appropriate if the open bite was due to vertical underdevelopment of the anterior dentoalveolar processes. However, studies have indicated that skeletal open bites often show maxillary incisor supereruption.1,2,17,18 Further eruption of the incisors by using vertical elastics elongates the anterior teeth beyond the limits of stability, resulting in relapse. Rather than closing the anterior open bite by extruding the anterior dentoalveolar complex, Subtelny and Sakuda17 indicated that these cases would benefit more from intrusion of the maxillary and mandibular molars. Posterior bite blocks containing repelling magnets have been proposed as a treatment modality for anterior open bites.19,20 Dellinger19 described the active vertical corrector as a removable or fixed orthodontic appliance designed to reciprocally intrude the posterior teeth. By intruding the posterior teeth, the mandible autorotates in an upward and forward direction. This form of treatment is advantageous because it corrects the anterior open bite and simultaneously reduces the total anterior facial height. However, an adverse side effect is the creation of a buccal crossbite due to the repelling forces of the magnets during lateral excursions. Kuster and Ingervall21 used spring-loaded bite-blocks to avoid the undesirable lateral effects of repelling magnets. They found no evidence of posterior teeth intrusion. Kiliaridis22 compared the treatment effects of plain posterior bite blocks with posterior repelling magnet splints. He demonstrated significant intrusion of posterior teeth and no transverse problems with the plain posterior bite blocks. A vertical-pull chincup has been successfully used with conventional orthodontic appliances for correcting open bite malocclusion.23-25 The chincup controls the excessive lower anterior facial height and helps to prevent extrusion of the posterior teeth. Sankey et al26 also showed positive treatment results using a chincup in conjunction with a bonded palatal expander. They demonstrated relative intrusion of the maxillary molars, vertical control of the mandibular molars, and increased eruption of the maxillary incisors that contributed to improvements in overbite. The high-pull headgear appliance is another extraoral device used to intrude the maxilla. 27-31 Its use is limited because its forces are applied to the maxilla, with no direct treatment effects on the mandible’s shape or growth. Microimplants have recently been used to intrude molars32,33 with conventional orthodontic appliances. According to initial reports, microimplants are much less expensive than traditional osseointegrated implants and will simplify treatment mechanics. The obvious disadvantages are that they require a surgical procedure for placement and removal after treatment. Finally, all of the previous treatment modalities for correcting anterior open bite malocclusion have focused on intruding posterior teeth and facilitating autorotation of the mandible. However, if one considers that craniofacial morphology can be influenced by the size, shape, and function of the masticatory muscles, then perhaps strengthening the muscles would produce an adjunctive treatment modality to correct open bite malocclusions. It has been a common finding that the elevator muscles of the mandible influence the transverse and vertical dimensions of the face.34-36 Numerous studies demonstrate that strength training of masticatory muscles can influence morphology.37-40 In a prospective study of early open bite treatment, English41 demonstrated that light masticatory exercise combined with high-pull headgear produced significant reductions in the ANB and gonial angles and reduced mandibular autorotation by 2.2°. CONCLUSIONS Masticatory exercise was an important adjunctive treatment in correcting an open bite malocclusion in an extremely compliant adult patient. Additionally, the patient had infraeruption of the maxillary incisors, and thus we were able to extrude them to provide a more 98 Lindsey and English American Journal of Orthodontics and Dentofacial Orthopedics July 2003 esthetic incisor display. At a retention check 14 months after removing the appliances, the occlusion appeared stable. However, long-term verification will be needed because open bite malocclusions tend to relapse more than most other types of malocclusions. Perhaps strengthening of the masticatory musculature through clenching exercises will also help to prevent open bite relapse. appliance on the dentofacial complex. Am J Orthod 1989;95: 467-78. Kuster R, Ingervall B. The effect of treatment of skeletal open bite with two types of bite-blocks. Eur J Othod 1992;14:489-99. Kiliaridis S, Egermark I, Thilander B. Anterior open bite treatment with magnets. Eur Orthod Soc 1990;12:447-57. Pearson L. 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