A 13-year-old growing female patient presented with hemimandibular hyperplasia of the right side, Class III hypodivergent skeletal pattern, and severe facial asymmetry. Corrective surgery was deferred until her growth had been completed. When the patient was 16 years old, a low condylectomy was performed on the hyperplastic side of her mandible to prevent its progressive condylar hyperplasia, while simultaneous orthodontic camouflage treatment was performed with the intrusion of the maxillary right posterior teeth using temporary skeletal anchorage devices without additional orthognathic surgery. A low condylectomy caused anterior and lateral open bite after the downward and backward movement of the chin, which improved Class III appearance. The intrusion of the maxillary right posterior teeth followed by compensating extrusion of the mandibular posterior teeth contributed to improve the patient’s facial asymmetry with correction of the transverse occlusal plane and lip canting. After 30 months of treatment, an acceptable esthetic outcome and functional occlusion were achieved. The treatment results were well maintained for 1-year retention.
Highlights
- •
A growing patient had Class III malocclusion and hemimandibular hyperplasia.
- •
A low condylectomy was performed to correct the mandibular asymmetry and protrusion.
- •
Maxillary right posterior teeth were intruded with temporary skeletal anchorage devices.
- •
Facial asymmetry and mandibular protrusion were improved and stable after 1 year.
- •
Functional adaptation and remodeling of the temporomandibular joint were achieved.
Hemimandibular hyperplasia (HH) is a developmental anomaly classified as type 2 condylar hyperplasia (CH). Hyperplasia of the condyle has been differentiated into 3 categories: HH, hemimandibular elongation, and hybrid forms. Although CH can progress into HH or hemimandibular elongation, there should be a differentiation between them.
HH is characterized by a 3-dimensional and unilateral enlargement of the mandible, which ends at the midline of the symphysis. HH usually begins during a growth stage; thereby, compensatory vertical overdevelopment of the maxilla follows the downward growth of the mandible on the affected side, causing facial asymmetry, a tilted occlusal plane, and asymmetrical mandibular border. , , The etiology of HH is not clear, but hormonal influences, heredity, hypervascularity, arthrosis, infection, or trauma have been considered as causative factors which produce hypertrophic activities of a unilateral condyle. , ,
HH is corrected primarily with surgical procedures, including 2-jaw surgery, preserving the hypertrophic condyle when the growth activity of the condyle ceases. , , However, a mandibular condylectomy should be considered at the same time depending on the severity and status of condylar growth, even in adult patients. , In addition, contouring surgical procedures such as mandibuloplasty, genioplasty, osteotomy, or ostectomy might be necessary when the size and shape of the mandibular right and left borders are significantly different. ,
In most patients, a condylectomy is performed after growth has ceased. However, HH patients tend to grow longer and exhibit latent growth. Therefore, an early condylectomy should be considered to prevent too much progress of unilateral hypertrophy when there is a severe abnormal condylar activity. Unilateral abnormal condylar activity can be detected by bone scintigraphy, but this should not be considered as an absolute determinant for performing condylectomy because its specificity has been reported not adequate to evaluate those activities. , ,
There are several types of condylectomy; the best option depends on the vertical position of the resection, which is determined by the severity of the condylar deformation and mandibular asymmetry. , A low condylectomy is recommended rather than condylar shaving or high condylectomy when the asymmetric mandibular deformation is severe. , , Some studies reported complications after a condylectomy such as anterior open bite, lateral precontact, deviation toward the corrected side on mouth opening, temporomandibular joint (TMJ) ankylosis, and loss of lateral excursion on the operated side. , , , However, an acceptable articular function can be maintained after condylectomy if the operation is followed by a successful functional rehabilitation.
The present case report describes the treatment of a patient with HH with a low condylectomy followed by intrusion of the maxillary posterior teeth with a miniplate on the affected side and extrusion of the other posterior teeth without additional orthognathic surgery.
Diagnosis and etiology
A 13-year-old growing female patient presented with a chief complaint of mandibular asymmetry. She showed severe hyperplasia of the right side of her face with canting of the transverse occlusal plane and lips drooping toward the right side. She had an increased vertical height of the middle and lower third of the face on the affected side, with a deviation of the chin toward the unaffected side, and she had an open bite in the right canine and premolar area, but not severe because of the compensatory downward growth of her maxilla after vertical hypertrophy of the mandible on the affected side. She showed a rotated and tilted occlusion including the anterior teeth and displacement of the midline of her mandibular dental arch toward the affected side. Intraorally, she also showed a different gingival height on the maxillary central incisors, and her anterior gingival contour was not ideal. She had a 10% overbite and 1-mm overjet. Her maxillary right lateral incisor showed a crossbite, and her maxillary right side was slightly constricted compared with the contralateral side, but any functional shift was not detected when her mandible was guided into centric relation ( Fig 1 ). She had no specific medical and dental history to report.
Radiographs showed a unilateral enlargement of her mandible in all dimensions ending at the midsymphysis, followed by the downwards growth of her maxilla, including her maxillary sinus, which caused a canting of her maxilla. Her inferior alveolar nerve canal is more displaced to the lower border of her mandible on the affected side than on the contralateral side. She was still growing at stage 8 of the skeletal maturation index (SMI) ( Figs 2 and 3 ). She was diagnosed as having HH, Class III hypodivergent skeletal pattern, and severe facial asymmetry, but corrective surgery was deferred until she stops growing.
At the age of 16 years, she looked similar to her appearance when she was 13 years old, but the elongation of the right side of her face was more severe with canting of her transverse occlusal plane, her lips drooped toward the right side, and her open bite had worsened in the right canine and premolar area. The bone scintigraphy showed she had an abnormal condylar activity on the right TMJ even though her SMI indicated stage 11, which presented the completion of her growth ( Figs 4-7 ; Supplementary Fig 1 ).
Treatment objectives
The treatment objectives for this patient were to (1) correct her facial asymmetry and simultaneously stop any active condylar growth, (2) establish a functional occlusion, and (3) improve her facial appearance.
Treatment alternatives
Two treatment alternatives were discussed. The first option was to perform a condylectomy to eliminate any further CH plus simultaneous orthognathic surgery with additional contouring surgical procedures. The second option was to perform a relatively less invasive surgical procedure, including a condylectomy followed by orthodontic camouflage treatment. The tilted maxillary occlusal plane could be corrected by a selective molar intrusion using temporary skeletal anchorage devices instead of orthognathic surgery. With this option, it will not be possible to achieve an ideal correction of facial asymmetry, but it would be advantageous in terms of cost and safety. The patient and her parents chose the second option.
Treatment progress
For the patient’s treatment, 0.022 × 0.028-in standard edgewise appliances with a 0.014-in nickel-titanium archwire followed by a 0.018-in stainless steel archwire were placed in both arches to level and align the dentition. Transpalatal arch and lingual arch were attached to the maxillary and mandibular first molars, respectively, to support cross-arch stability. After 2 months of leveling, a low condylectomy with access in the pretragus area was performed on the mandibular right condyle, and the surgically excised tissue was sent for a histopathological examination. The specimen consisted of a resected condyle (2.9 cm in height and 1.9 cm in width) that showed CH with destroyed cartilage along with a broadening of the subchondral layer of bone. Simultaneously, an I-shaped miniplate (Jin Biomed Co, Bucheon, South Korea) fixed by 2 mini-implants (1.5 mm in diameter, 4 mm in length) was placed in the right infrazygomatic crest area for the intrusion of the maxillary right posterior teeth. A severe open bite occurred except in the area of the right posterior teeth because of the displacement of the mandible, but no elastics were used to close the open bite for spontaneous adaptation of the mandibular right condyle without extrusion of the mandibular right posterior teeth. Two months after the condylectomy, the occlusion was still unstable because the condyle did not adapt. The intrusion of the maxillary right posterior teeth was maintained using elastic threads. Seven months after the condylectomy, the open bite was reduced throughout the entire arch. Cross elastics were used between the maxillary left and mandibular right canines, whereas up and down elastics were used between the maxillary and mandibular left canines to extrude the left dentition and, thus, correct the canting. Nine months after the condylectomy, the canting of the maxillary transverse occlusal plane was corrected. A mini-implant was placed between the maxillary right canine and first premolar to maintain the vertical position of the maxillary right dentition, whereas up and down elastics were applied to extrude the mandibular right dentition. Eleven months after the condylectomy, the open bite was significantly reduced, and 21 months after the condylectomy, up and down elastics were applied on both sides for better interdigitation ( Supplementary Figs 2-4 ).
Twenty-eight months after the condylectomy, brackets and bands were removed, and fixed retainers were bonded on the maxillary and mandibular anterior teeth. The total treatment time was 30 months. After that, circumferential retainers were delivered on both arches. A biteplate was added to the retainer in the maxillary right posterior area for 3 months to minimize any relapse of the intruded maxillary right posterior teeth. After a 3-month retention period, the biteplate on the retainer was removed to prevent further extrusion of the contralateral posterior teeth ( Fig 8 ).
Treatment results
Posttreatment photographs, casts, and radiographs showed normal occlusal relationships and acceptable facial symmetry with correction of the canted transverse occlusal plane and physiological bone remodeling of the condylar head on the operated side ( Figs 8-10 ). The low condylectomy followed by the intrusion of the maxillary right posterior teeth successfully corrected the facial and dental asymmetry and mandibular protrusion. However, we could not improve her overbite and overjet because of the considerable amount of downward and backward rotation of the mandible after condylectomy. After treatment, she was recommended for a periodontal consultation to improve the maxillary anterior gingival contour, but she declined. In a lateral cephalometric superimposition, the mandible showed significant growth between T1 and T2, especially on the right side during the follow-up period. After the condylectomy, the mandible moved downward and backward and rotated clockwise. In addition, in a superimposition from the cone-beam computed tomography reconstructed posteroanterior images, the mandible showed clockwise rotation from T2 to T4, and the transverse occlusal plane was almost parallel to the interpupillary line at T4 ( Fig 11 ). The patient’s temporomandibular function was not disturbed, and there was no significant relapse after 1 year of retention ( Figs 12 and 13 ).
The ANB increased from 0.1° to 2.5°, mainly by the downward and backward movement of the mandible. The Frankfort-mandibular plane angle increased with clockwise rotation of the mandible, especially on the right side. The Z angle improved from 82° to 75°. The dentoalveolar height increased except on the maxillary right first molar, where it decreased because of intrusion resulting from the miniplate ( Table I ). The medial inclination of the ramal plane increased on the left side but decreased on the right side, whereas all other measurements influencing facial asymmetry indicated that the asymmetry was reduced by condylectomy and intrusion of her maxillary right molars ( Fig 14 ; Table II ).
