Facial improvement after mandibular midline distraction and surgically assisted rapid maxillary expansion

This case report describes the retreatment of a 49-year-old woman with severe crowding in the mandibular incisor region and tapered maxillary and mandibular arches. Treatment consisted of mandibular midline distraction and surgically assisted rapid maxillary expansion to increase arch length. The need for proper presurgical orthodontics is described, and the complications during treatment are discussed. The results of treatment, including the superimposition of 3-dimensional facial scans, are presented. The treatment approach we used is typically indicated for patients with previous extractions of all first premolars who develop significant crowding after treatment. Surgical planning in 3 dimensions and the use of a 3-dimensional designed surgical osteotomy guiding wafer should improve the predictability of this treatment approach.

Highlights

  • A 49-year-old woman had severe crowding crowding, tapered arches, previous extractions.

  • She was treated with mandibular midline distraction and surgically assisted RME.

  • 3D surgical planning and osteotomy guiding wafer improved the predictability of surgery.

In the second part of the last century, orthodontic treatment including extractions of all first premolars was a common treatment approach. Unfortunately, orthodontic treatment results can be unstable in extraction as well as nonextraction patients. Relapse, unfavorable growth, and physiologic recovery after treatment may result in significant changes in tooth position. Development of crowding after orthodontic treatment is observed in treated patients as well as in untreated adults. Because of patients’ desire to have a perfect dentition throughout life, those who were treated with orthodontic appliances decades ago now ask for orthodontic retreatment. Previous extractions can reduce the number of treatment options and make orthodontic retreatment complicated and challenging.

This case report describes the retreatment of a healthy 49-year-old woman at Radboud Medical Centre in The Netherlands 35 years after her initial orthodontic treatment. Then, all first premolars were extracted, and she was treated with fixed appliances. This initial treatment ended prematurely, and no retention was provided because her orthodontist suddenly died. The patient complained about her crooked front teeth, prominent maxillary incisors, incompetent lip closure, and mentalis habit. The selected plan for her retreatment included surgically assisted rapid maxillary expansion (SARME) and mandibular midline distraction (MMD). After jaw distraction, the dental crowding in the maxillary and mandibular arches as well as the tapered arch form were corrected with fixed appliances. A Class I molar and canine occlusion with proper overjet and overbite was achieved. The lip incompetence, mentalis habit, and facial profile were significantly improved. In this article, the treatment outcome, including superimposition of 3-dimensional (3D) facial stereophotogrammetric images, is presented. Treatment results and some complications during treatment are discussed. See Supplemental Materials for a short video presentation about this study.

Diagnosis and etiology

The clinical evaluation of the patient’s profile showed a Class II profile with a hyperdivergent vertical skeletal pattern, reduced chin prominence, incompetent lips at rest, and a mentalis habit ( Fig 1 ). Overjet and overbite of 4 mm were measured. The occlusion of the canines and molars was a half-cusp Class II relationship at the right side and a quarter-cusp Class II relationship at the left side. Moderate crowding in the maxillary front teeth (4 mm) and severe crowding in the mandibular front teeth (6 mm) was found. There was no tooth-size discrepancy, and the maxillary and mandibular arch midlines were coordinated.

Fig 1
Pretreatment photographs.

Because the first premolars had been extracted during the initial orthodontic treatment, only 4 second premolars were present. All molars and premolars contained well-functioning amalgam or composite resin restorations ( Fig 1 ). The dental arch forms in the maxilla and the mandible were tapered ( Fig 2 ). The third molars were absent on the panoramic radiograph. Cephalometric analysis of the head plate showed an SNA angle of 84° and an ANB angle of 6°, indicating a mild Class II jaw relationship and a hyperdivergent vertical skeletal and dentoalveolar pattern. Proclination of the maxillary and mandibular incisors and protrusion of the upper and lower lips were noticed ( Fig 3 ).

Fig 2
Pretreatment dental models.

Fig 3
Pretreatment radiographs and cephalometric analysis.

A backward slanting profile, reduced chin prominence, lip incompetence, and mentalis habit corresponded with the patient’s hyperdivergent vertical skeletal pattern. The Class II jaw relationship and Class II malocclusion corresponded with the tapered dental arch form in the maxilla. It can be speculated that a combination of insufficient lip closure, relapse, and physiologic mesial drift resulted in the proclination of the mandibular incisors and severe incisal crowding.

Treatment objectives

The treatment objectives for this patient were the following.

  • 1.

    Correction of the crowding in the maxillary and mandibular arches and modification of the tapered arch forms.

  • 2.

    Retraction of the maxillary incisors, reduction of overjet and overbite, and correction of the Class II molar and canine occlusion.

  • 3.

    Functional correction, competent lips, reduction of the mentalis habit, and improvement of the profile and smile esthetics.

Treatment objectives

The treatment objectives for this patient were the following.

  • 1.

    Correction of the crowding in the maxillary and mandibular arches and modification of the tapered arch forms.

  • 2.

    Retraction of the maxillary incisors, reduction of overjet and overbite, and correction of the Class II molar and canine occlusion.

  • 3.

    Functional correction, competent lips, reduction of the mentalis habit, and improvement of the profile and smile esthetics.

Treatment alternatives

Correction of the crowding in the mandibular front region required at least 6 mm of space. Extraction of the left and right second premolars would create approximately 14 mm of space. Reciprocal closure of the extraction diastemas could then be used to solve the mandibular incisor crowding. Extractions of the remaining mandibular premolars would result in a first molar positioned directly next to the canine, and this would lead to a suboptimal occlusion and less optimal dental esthetics. As an alternative, extraction of 1 mandibular central incisor was considered. Approximately 5 to 6 mm of space would then be available. Some interproximal enamel reduction of the mandibular incisors would be needed to create some extra space to solve the crowding and protrusion of the incisors. Extraction of a mandibular incisor would cause a tooth-size discrepancy of ±5 mm. It would not be possible to correct this by interproximal enamel reduction of the maxillary incisors only. Excessive enamel reduction of the maxillary incisors would also reduce the esthetics of the crowns, so it was concluded that, after extraction of a mandibular incisor and correction of the Class II occlusion into a Class I relationship, an increased overjet and protrusion of the maxillary incisors would remain.

The moderate crowding in the maxillary arch could theoretically be solved by proclination of the front teeth and some interproximal enamel reduction. But proclination of the maxillary incisors would increase the protrusion of the incisors and overjet. Moreover, the arch forms would then become more tapered, and this incisor protrusion would increase the lip incompetence and mentalis habit. Sufficient space for alignment and retraction of the maxillary incisors could be obtained by extraction of the 2 maxillary premolars. As for the mandible, extraction of the premolars was rejected as a treatment option because this would compromise both the occlusion and the dental esthetics.

As an alternative treatment approach, it is possible to distalize the maxillary molars and retract the maxillary front teeth with temporary anchorage devices such as zygoma anchors to obtain a normal overjet and a Class I molar and canine relationship. As an alternative for zygoma anchors, a palatally located temporary anchorage device could be used for distalization of the molars and retraction of the maxillary arch. A disadvantage of these treatment options is that the narrow maxilla and mandible would not be corrected. Because of the disadvantages of these treatment options, a nonextraction treatment plan was chosen.

Treatment plan

For this patient, surgically assisted distraction of the maxilla and the mandible were used to expand the maxilla and the mandible, enable expansion of both dental arches, solve the incisal crowding, and retract the maxillary front teeth to reduce the overjet. A surgically assisted MMD procedure combined with a SARME procedure were performed. Expansion of both arches was achieved by activation of 2 custom-made tooth-borne hyrax expanders. According to the panoramic radiograph, limited space was available between the roots of the mandibular central incisors. Therefore, the angulation and position of the central incisors was changed before the start of surgery with partial fixed orthodontic appliances to create sufficient space for the planned mandibular midline osteotomy. After surgical expansion of both the maxilla and the mandible, fixed appliances were used to align the dentition. Class II elastics were needed to correct the occlusion. Canine-to-canine fixed retainers (C-C bar) were placed in the maxillary and mandibular front regions for permanent retention. A removable retainer (Hawley) was required at night to retain the width of the maxillary arch.

Treatment progress

Three months before the mandibular midline osteotomy, preadjusted self-ligating brackets (0.018 × 0.025-in slot size) with an interactive clip (In-Ovation R; Dentsply GAC, Islandia, NY) were bonded onto the buccal surfaces of the mandibular incisors. The brackets were placed in a disto-angulated position to create some distal tip of the roots of the mandibular central incisors. An 0.018 × 0.018-in nickel-titanium archwire (Dentsply GAC) with a push coil between the mandibular left and right central incisors was placed. A cone-beam computed tomography radiograph (CBCT), taken 2 weeks before surgery, indicated that just enough interdental space in the region of the planned mandibular midline osteotomy was available. Notably, the axial slices of the CBCT demonstrated some mesiobuccal rotation of the mandibular central incisors ( Fig 4 ).

Fig 4
CBCT images 2 weeks before surgery. Yellow arrow , Marginal interdental space between the roots of the mandibular central incisors at the lingual side due to some mesiobuccal rotation.

Three weeks before surgery, the maxillary and mandibular molars and premolars were separated with separation elastics. Bands were fitted for the maxillary and mandibular expansion devices, and impressions were taken with the bands in situ. Both hyrax expanders were manufactured on plaster casts in the laboratory of Radboud University Medical Centre. A conventional hyrax design with bands on both premolars and second molars with a 9-mm expansion screw for the maxillary arch was fabricated. Because of the tapered form of the mandibular arch and the small intercanine width, insufficient space was available to position a large expansion screw. Therefore, a screw with a limited expansion range of 7 mm was selected and soldered in a more occlusal position. One day before surgery, the brackets at the mandibular incisors were removed, and both hyrax expanders were placed ( Fig 5 ).

Fig 5
Intraoral photographs 1 day before surgery. Brackets were removed, and both hyrax expanders were placed.

Both surgical procedures were performed under general anesthesia. Surgery started with the usual SARME procedure as described elsewhere. The mandibular midline osteotomy procedure was then started. A round bur was used to drill pilot holes in the buccal cortical bone between the roots of the mandibular central incisors in a vertical line, toward the lower border. An oscillating saw was used to make a vertical bone cut starting at the apical area of the incisors, through the symphysis down to the mandibular lower border. Finally, a small osteotome was used to perform a complete osteotomy of the interdental bone and lingual cortex ( Fig 6 , A ). The effect of activation of the expansion screws of both hyrax expanders was tested during surgery. Activation of the screws caused proper expansion of the maxilla and the mandible. After testing, both expansion screws were deactivated, and the wound was sutured. The total surgical procedure took approximately 55 minutes: 40 minutes for the SARME and 15 minutes for the MMD. After surgery, the location and direction of the midline cuts in the maxilla and the mandible were checked with radiographs ( Fig 6 , B ). The patient stayed 1 night in the hospital and was discharged the next morning.

Fig 6
A, Intraoral photographs during surgery; B, radiographs just after surgery.

After surgery, a latency period was maintained to allow for some callus formation. Activation of the osteodistraction devices was started during the control visit 9 days after surgery. The patient was instructed to activate the devices twice a day. This activation created a daily expansion of the jaws of 0.5 mm. Approximately 9 mm of expansion in the maxillary arch and 6 mm in the mandibular arch were planned. The amounts of expansion were clinically evaluated in the orthodontic office at days 3, 5, 10, and 18 after the start of the expansion procedure. Sufficient expansion of the jaws was obtained after 18 days, and the spacing between the maxillary central and mandibular central incisors was evident. Notably, approximately 8 mm of space between the maxillary central incisors and 6 mm space between the mandibular central incisors were obtained ( Fig 7 ). This difference in space can be explained because the patient stopped the activation of the expansion device in the mandible after 13 days, because she had experienced some high resistance during activation of the screw. Eventually, both expansion screws were locked with composite to prevent their deactivation.

Fig 7
Photographs after 18 days of active expansion. Radiographs of root canal treatment.

The clinical status was evaluated 3 days after the active expansion. It was then noticed, the crown of the mandibular left central incisor showed a grey discoloration that was not observed earlier. The sensitivity of the tooth was tested with cold spray, and the pulpal reaction was negative. Iatrogenic trauma of the mandibular incisor was confirmed by a periapical radiograph. A small round perforation in the middle of the incisal root was observed that could have happened during predrilling of the osteotomy line. This finding was discussed with the Department of Endodontology of Radboud University Medical Centre, and root canal treatment of the tooth was advised. The patient was referred to her dentist, and the root canal treatment was performed ( Fig 7 , B ). Regular follow-up of the clinical situation of the mandibular left central incisor was performed by the endodontist at Radboud Medical Centre.

Eight weeks after the last activation of the expansion devices, preadjusted self-ligating brackets (0.018 × 0.025-in slot) with an interactive clip (In-Ovation R; Dentsply GAC) were placed in the maxillary and mandibular front regions. Alignment was started with a 0.014-in nickel-titanium archwire (Dentsply GAC). Both hyrax expanders were removed after 3 months. Subsequently, the premolars were bonded with preadjusted self-ligating brackets (0.018 × 0.025-in slot size) with an interactive slot (In-Ovation R; Dentsply GAC). Fixed retention of the expansion of the arch with a transpalatal arch in the maxilla was planned. However, the patient preferred treatment without bands and transpalatal arch slots, because of irritation of the gingiva in the molar region. The molars were bonded, and a 0.016-in nickel-titanium archwire (Dentsply GAC) was placed for alignment of both arches. A removable appliance was used to retain the width of the maxillary arch. The patient was instructed to wear the appliance only at night. In the mandibular arch, no removable retention device was placed. After alignment with 0.018 × 0.018-in nickel-titanium archwires for 7 weeks, 0.016 × 0.022-in stainless steel wires (Dentsply GAC) with an overcorrected arch width were placed in the maxillary and mandibular dentitions to prevent relapse of the expansion. The use of the removable retainer was stopped. Intrusion steps for the maxillary and mandibular molars were placed, and Class II elastic traction (¼ in, 3.5 oz) was used to obtain good interdigitation of the posterior teeth. Because the patient complained about the black triangles in the maxillary front teeth, interproximal enamel reduction was performed, and the residual spaces were closed with power chain ( Fig 8 , A ). A panoramic radiograph was taken 9 months after surgery to evaluate the length and angulation of the roots. On this radiograph, no evident root resorption was observed, and the angulation of the roots was sufficiently corrected ( Fig 8 , B ). It was decided that the treatment goals where established, and active treatment could be completed. Total active treatment time for this patient was 1 year 7 months.

Dec 19, 2018 | Posted by in Orthodontics | Comments Off on Facial improvement after mandibular midline distraction and surgically assisted rapid maxillary expansion
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