Nonsurgical treatment of an adult with a skeletal Class II gummy smile using zygomatic temporary anchorage devices and improved superelastic nickel-titanium alloy wires

Patients with a severe gummy smile and a skeletal Class II profile are difficult to treat. This case report describes an effective treatment alternative for improving a gummy smile in a patient with a severe Class II molar relationship, severe crowding, and lip protrusion using zygomatic anchorage devices and improved superelastic nickel-titanium wires. A 36-year-old woman had an excessive overjet and a deep overbite with a bilateral Angle Class II molar relationship. The cephalometric analysis demonstrated a Class II skeletal relationship (ANB, 9.5°), retroclination of the mandible (FMA, 38.4°), and severe labial inclination of the mandibular incisors (IMPA, 101.9°). The main treatment objectives included normalizing the overjet and overbite, improving the gummy smile, and establishing a satisfactory occlusion. During treatment with fixed appliances, intrusion of the total maxillary dentition using skeletal anchorage and elimination of the bimaxillary protrusion were achieved. Improvement of the lateral profile and gummy smile enhanced facial esthetics. Intrusion and distalization of the maxillary dentition with skeletal anchorage and improved superelastic nickel-titanium wires provided a satisfactory dental occlusion, esthetic improvement, and adequate function. This approach should be considered as an alternative treatment option to orthognathic surgery for adults with high-angle skeletal Class II malocclusion and a gummy smile.

Highlights

  • We treated a skeletal Class II gummy smile case with distalization and intrusion of maxillary dentition.

  • We used superelastic wires as working wires for the entire treatment.

  • Treatment provided dramatic improvement in esthetics without apparent root resorption.

  • This patient showed long-term stability after active treatment.

An Angle Class II malocclusion in an adult with a skeletal Class II profile, especially with maxillary vertical excess, is a difficult problem for orthodontists to correct. This is because the clockwise rotation of the mandible secondary to distalization of the maxillary molars for correction of the molar relationship confounds the skeletal discrepancy and sometimes exacerbates the facial profile. Moreover, in patients with severe gingival exposure due to excessive vertical growth of the maxilla, it would be esthetically inappropriate to simply depress the maxillary anterior teeth because this procedure worsens the smile arc. Therefore, it is desirable to depress the whole maxillary arch. However, it is difficult to accomplish using conventional mechanics.

Therefore, the most effective treatment option for patients who wish to eliminate their gummy smile requires an orthognathic (surgical) approach. Because some patients are reluctant to undergo surgery, there is a clear need for a new orthodontic treatment for patients with a deepbite and a gummy smile caused by maxillary vertical excess. Such a treatment should effectively intrude the maxillary dentition and eliminate the gummy smile without surgical intervention.

A skeletal anchorage system was recently developed to correct severe malocclusions. Use of this system allows for distal movement of the maxillary molars without unfavorable side effects. Additionally, some reports have described the successful use of temporary anchorage devices to intrude the posterior teeth in both arches and decrease the facial height in adults with a skeletal Class II malocclusion and an open bite.

However, depression of the maxillary molars worsens the deepbite in skeletal Class II patients with the gummy smile. This may be related to the lack of case reports of nonsurgical treatment of skeletal Class II adults with a gummy smile. This case report describes an effective alternative to improve a gummy smile in a patient with a severe Class II molar relationship, severe crowding, and lip protrusion using zygomatic temporary anchorage devices.

Diagnosis and etiology

A 36-year-old Japanese woman came with a Class II malocclusion and a severe high-angle skeletal Class II profile, lip protrusion, and a gummy smile ( Fig 1 ). She had lost the maxillary right lateral incisor secondary to trauma. She complained about her gummy smile, difficulty with lip closure, and crowding. Pretreatment facial photographs showed a convex profile, protrusion of both lips, hyperactivity of the mentalis muscle, and an excessive display of her maxillary gingiva in the incisor region. Model analysis showed bilateral full Class II molar and canine relationships with overjet of 8.5 mm, overbite of 4.5 mm, arch length discrepancies of −7.5 mm on the maxillary arch and −9.4 mm on the mandibular arch, and a midline shift of the maxillary arch ( Fig 2 ).

Fig 1
Pretreatment facial and intraoral photographs.

Fig 2
Pretreatment dental casts.

A panoramic radiograph showed a horizontally impacted left third molar in the mandible, a missing maxillary right lateral incisor, root canal treatments involving the right canine and central incisors in the maxillary arch, and a slight horizontal resorption of the alveolar bone ( Fig 3 ).

Fig 3
Pretreatment panoramic and lateral cephalometric radiographs and cephalometric analysis with a Japanese normal profilograph.

Initial lateral and posteroanterior cephalometric radiographs were taken in centric occlusion with closed lips. The cephalometric analysis demonstrated a Class II skeletal relationship (ANB angle, 9.5°), retroclination of the mandible (FMA, 38.4°), large lower facial height due to the maxillary excess, and severe labial inclination of the mandibular incisors (IMPA, 101.9°).

Mandibular movement and surface electromyographic activities of the masticatory muscles, such as the masseter, anterior temporalis, posterior temporalis, and anterior digastric muscles, were recorded before the orthodontic treatment to assess stomatognathic function ( Fig 4 ).

Fig 4
Pretreatment mandibular kinesiographs and surface electromyographs: A, wide opening and closing movements of the mandible; B, lateral and forward border movements of the mandible; C, electromyographs of the masticatory muscles at maximum voluntary clenching: RTA , right anterior temporalis muscle; LTA , left anterior temporalis muscle; RTP , right posterior temporalis muscle; LTP , left posterior temporalis muscle; RM , right masseter muscle; LM , left masseter muscle; RD , right anterior digastric muscle; LD , left anterior digastric muscle.

Treatment objectives

The main treatment objectives were to normalize overjet and overbite, improve the gummy smile, and establish satisfactory occlusion with stable posterior support. Figure 5 shows the treatment goal based on the cephalometric prediction. In reference to this treatment goal, we planned intrusion of the maxillary central incisors and first molars by 3.2 and 3.0 mm, respectively. Additionally, a 3.0-mm distalization of the maxillary molars was required to correct the Class II dentition.

Fig 5
Treatment goal: paper prediction with cephalometric tracing.

Additional treatment objectives included establishment of total intrusion of maxillary arch for the appropriate gingival display, distalization of the maxillary molars to create a Class I molar relationship using skeletal anchorage, correction of the bimaxillary protrusion, and relief of the severe crowding with extraction of the maxillary left first premolar and bilateral mandibular second premolars.

Zygomatic anchorage plates were used to achieve absolute anchorage for distalization and intrusion of the maxillary dentition.

Treatment objectives

The main treatment objectives were to normalize overjet and overbite, improve the gummy smile, and establish satisfactory occlusion with stable posterior support. Figure 5 shows the treatment goal based on the cephalometric prediction. In reference to this treatment goal, we planned intrusion of the maxillary central incisors and first molars by 3.2 and 3.0 mm, respectively. Additionally, a 3.0-mm distalization of the maxillary molars was required to correct the Class II dentition.

Fig 5
Treatment goal: paper prediction with cephalometric tracing.

Additional treatment objectives included establishment of total intrusion of maxillary arch for the appropriate gingival display, distalization of the maxillary molars to create a Class I molar relationship using skeletal anchorage, correction of the bimaxillary protrusion, and relief of the severe crowding with extraction of the maxillary left first premolar and bilateral mandibular second premolars.

Zygomatic anchorage plates were used to achieve absolute anchorage for distalization and intrusion of the maxillary dentition.

Treatment alternatives

Three treatment alternatives were presented to the patient.

  • 1.

    Orthognathic surgery was the first option for correction of her gummy smile, which was mainly caused by a skeletal factor: ie, maxillary vertical excess. Orthognathic surgery could be used to impact and retrude the maxillary dentoalveolar segment, thus improving the skeletal anteroposterior discrepancy and obviating the gummy smile.

  • 2.

    The second approach was to reduce the maxillary protrusion and relieve the severe crowding with extraction of the maxillary left first premolar and mandibular right central incisor, resulting in a Class II molar relationship. The disadvantage was little improvement in the facial profile because the proclination of the mandibularr incisors would remain with extraction of only the mandibular incisor.

  • 3.

    The third option was to extract the maxillary first premolar and the mandibular second premolars and apply 2 miniplate anchorages for correction of the Class II molar relationships, as well as perform total intrusion and distalization of the maxillary arch for reduction of the lip protrusion and improvement of the gummy smile.

After we discussed the treatment alternatives with the patient, she was reluctant to undergo surgery and elected the third option for improvement of her facial profile and occlusion.

Treatment progress

Before orthodontic treatment, the mandibular left third molar was extracted. The 0.022-in preadjusted brackets were bonded to the maxillary lateral teeth excluding the second premolars, and improved superelastic nickel-titanium alloy archwires were used for initial leveling and aligning ( Fig 6 , A ). Crimpable hooks were attached at the midpoint between the first premolars and first molars bilaterally. One month after the start of treatment, an oral surgeon placed Y-shaped titanium anchor plates (Super Mini Anchorage Plates; Dentsply Sankin, Tokyo, Japan) on the bilateral maxillary zygomatic processes through the buccal mucosa under local anesthesia. The head parts of the miniplates were intraorally exposed and positioned between the maxillary second premolars and first molars outside the dental arch at the same height as the center of resistance of the maxillary dentition. The 0.018 × 0.025-in improved superelastic nickel-titanium alloy wires were used as the working wires ( Fig 6 , B ).

Dec 12, 2018 | Posted by in Orthodontics | Comments Off on Nonsurgical treatment of an adult with a skeletal Class II gummy smile using zygomatic temporary anchorage devices and improved superelastic nickel-titanium alloy wires
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