Miniscrew mechanics for molar distalization and incisor intrusion in a patient with a Class II brachyfacial pattern and gummy smile

A gummy smile is one of the most problematic characteristics in patients with a Class II Division 2 malocclusion, and the correction of vertical position and incisor torque is often challenging for the orthodontist. This case report describes the orthodontic treatment of a 31-year-old woman, assisted by miniscrew mechanics for maxillary arch distalization and correction of a gummy smile with a brachyfacial pattern. Two different mechanics were used. Miniscrews were placed in both maxillary tuberosities, and the maxillary arch was successfully distalized, correcting the Class II relationship. Interradicular miniscrews were placed for maxillary and mandibular incisor intrusion to correct the gummy smile, overbite, and torque. Finally, periodontal surgery was performed to lengthen the maxillary incisor crowns. Satisfactory smile esthetics and good occlusion were achieved. Follow-up after 24 months confirmed that the outcome was stable.

Highlights

  • The diagnosis of gummy smile etiology is crucial for accurate treatment planning.

  • Adequate vertical position and torque of incisors provide good stability.

  • Miniscrews facilitate the correction of Class II and incisor overeruption.

  • Gingivectomy improves smile esthetics when the altered passive eruption is diagnosed.

One of the most challenging objectives in the treatment of patients with Class II Division 2 malocclusion is to correct the vertical position and maxillary incisor torque. In these patients, the retroclination of the maxillary incisors is a consequence of the high pressure exerted by the lower lip, making intrusion and torque important treatment goals, together with their long-term stability.

In addition, some of these patients present excessive gingival display, resulting in a gummy smile and the consequent poor esthetics. For these patients, diagnosis and treatment planning must fulfill both orthodontic objectives and the patient’s expectations.

The decision to treat this vertical malocclusion with either orthodontics alone or in combination with orthognathic surgery will depend on the etiology and severity of the problem along with other individual factors. Orthognathic surgery is a common approach when the cause is anterior maxillary excess, with LeFort I osteotomy being the most common procedure. When surgical treatment is not an option because of the patient’s unwillingness to undergo the procedure, or when there is no skeletal maxillary vertical excess, the use of miniscrews should be considered as this offers an effective method for attaining maxillary incisor intrusion and so correction of the gummy smile.

Miniscrews offer the advantages of immediate loading, multiple placement sites, relatively simple placement and removal, and minimal expense. , When placing miniscrews in the anterior interradicular areas, in combination with appropriate orthodontic mechanics, the intrusion of maxillary and mandibular incisors can be achieved, improving overbite. ,

In addition, mechanics for maxillary molar distalization to correct a Class II malocclusion can be simplified by placing miniscrews in the maxillary tuberosity. Although this area is not ideal because of poor bone quality, the implementation of proper placement protocols and biomechanical design can lead to outstanding results.

If there is a deficiency in the upper lip length, cosmetic techniques such as lip repositioning can obtain good results in terms of gingival display, although this treatment might show some relapse.

When the patient presents reduced maxillary central incisor crown height because of altered passive eruption, periodontal surgery can be performed to lengthen the incisors’ clinical crowns, which will improve the gum-teeth relationship.

This case report describes the nonsurgical orthodontic correction of a brachyfacial pattern with Class II Division 2 malocclusion and excessive gingival display treated with miniscrews for maxillary and mandibular incisor intrusion, and molar distalization to provide adequate vertical position and incisor torque. Treatment enhanced smile esthetics and provided good long-term stability.

Diagnosis and etiology

A 31-year-old woman complaining of a gummy smile and maxillary incisor crowding visited the clinic seeking orthodontic treatment.

The frontal facial photograph shows a gingival display of 4-5 mm. The maxillary incisal exposure at rest was slightly excessive. The patient’s facial profile was convex, and the upper lip appeared protruded. There was scarce chin projection, and her mentolabial angle was obtuse ( Fig 1 ). The upper lip length was within the normal range, measuring 22 mm from subnasale to stomion, although there was an alteration in lip mobility; the excessive difference between the position of the patient’s upper lip at rest and full smile indicated upper lip hypermobility.

Fig 1
Pretreatment facial and intraoral photographs.

Intraoral photographs and study models show an incomplete molar and canine Angle Class II relationship. The overjet and overbite were 3.6 mm and 7.3 mm, respectively. Mandibular dentition showed an excessive curve of Spee because of the overeruption of the mandibular incisors. The maxillary dental midline was deviated to the right concerning the facial midline, whereas the mandibular dental midline was centered concerning the mandible, so maxillary and mandibular dental midlines did not match. The arch discrepancy index was −7.1 mm and −3.5 mm for the maxillary and mandibular arches, respectively. The maxillary central incisor crown height was short (7.9 mm), and the 4 maxillary incisors presented altered passive eruption ( Figs 1 and 2 ). The patient’s periodontal examination indicated good periodontal conditions.

Fig 2
Pretreatment study models.

Cephalometric analysis ( Fig 3 , A and B ; Table ) showed a skeletal Class II (ANB, 5.6°) with a severe brachyfacial pattern (facial axis, 94.3°; FMA, 25.1°; lower lower facial height, 71.6 mm). The maxillary and mandibular incisors were lingually inclined (PP-U1, 91°; IMPA, 76.1°), and as a result, the interincisal angle was increased (164.1°).

Fig 3
Pretreatment records: A, lateral cephalogram; B, cephalometric tracing; C, panoramic radiograph.

Table
Pretreatment, posttreatment, and postretention cephalometric summary
Cephalometric analysis Pretreatment Posttreatment Postretention
SNA angle (°) 83.1 82.9 83.0
SNB angle (°) 77.5 78.3 78.1
ANB angle (°) 5.6 4.6 4.5
Wits appraisal (mm) 4.7 0.2 0.0
U1-palatal plane (°) 91.0 109.7 110.0
IMPA (L1-Mp) (°) 76.1 96.5 96.5
Interincisal angle (°) 164.1 128.3 128.0
Overjet (mm) 3.6 2.2 2.2
Overbite (mm) 7.3 1.0 1.1
Facial axis (NaBa-PtGn) (°) 94.3 96.3 96.0
FMA (Mp-FH) (°) 25.1 23.0 23.0
Upper facial height (N-ANS) (mm) 48.0 48.0 48.0
Lower facial height (ANS-Me) (mm) 71.6 70.0 70.2
Mandibular length (Go-Gn) (mm) 76.0 76.0 76.0
Upper lip length (Sn-StSup) (mm) 22.3 22.0 22.1

The third molars had already been extracted by the oral surgeon at an earlier date ( Fig 3 , C ).

Based on these findings, the patient was diagnosed as presenting a brachyfacial pattern with skeletal and dental Class II Division 2, excessive overbite and overjet, increased curve of Spee, and excessive gingival display with an altered passive eruption of the maxillary incisors. Periodontal health was good.

Treatment objectives

The treatment plan focused on achieving optimal overjet and overbite, incisor torque, and on improving the gummy smile to provide adequate esthetics, function, and long-term stability, in the shortest possible treatment duration, without any need for patient compliance.

Treatment objectives were (1) to establish a skeletal and dental Angle Class I relationship, (2) to flatten the curve of Spee to achieve a harmonious smile, (3) to reduce the gummy smile aiming at a more attractive smile, (4) to obtain adequate incisor torque, and (5) to attain a balanced facial profile.

Treatment alternatives

The orthognathic surgical approach, such as LeFort impaction, was not considered in this patient, because the gummy smile was not due to anterior vertical maxillary excess.

Orthodontic treatment options involving extraction and nonextraction can be contemplated for Class II Division 2 malocclusion in an adult presenting negative arch discrepancy. To avoid extractions, effective molar distalization may be performed. However, when no distalization is desired or cannot be performed because of the presence of third molars, maxillary premolar extractions must be carried out to avoid excessive proinclination of the maxillary incisors, leaving a molar Class II and canine Class I malocclusion. The patient did not want any premolar extraction, and because third molars were not present, a non-extraction treatment was chosen.

Miniscrews may be used to correct a gummy smile successfully, and to flatten the curve of Spee. Conventional orthodontic methods, such as intrusion arches, utility arches, extraoral appliances, or rubber bands, can lead to undesirable side effects and also depend on patient cooperation. These unwanted side effects are extrusion and flaring of the posterior teeth, and the clockwise rotation of the mandible caused by the extrusion of the posterior teeth, which will worsen the Class II convex profile in many patients and also lead to an increase in the incidence of relapse in adults. ,

Maxillary central incisor crown height was short due to maxillary incisor altered passive eruption, so maxillary incisor periodontal surgery was planned. Because maxillary central incisor anatomy was appropriate, composite restorations were not a good option.

Finally, because of the hypermobility of the upper lip, the possibility of Botox or lip repositioning procedures were considered and proposed to the patient. Nevertheless, these treatments are not always stable. In the end, these procedures were not necessary because, after orthodontic treatment, the correction of the gingival smile was satisfactory.

Treatment progress

A 0.022 × 0.028-in slot preadjusted edgewise-ceramic appliance was placed on the maxillary arch (Clarity Advanced; 3M Unitek, Monrovia, Calif) because of patient preferences, whereas 0.022 × 0.028-in slot metal appliance system (Victory Series; 3M Unitek) was used on the mandibular arch. MBT prescription was chosen for both maxillary and mandibular bracket appliances.

The treatment plan was developed in 2 stages. The initial phase involved the insertion of a miniscrew into each maxillary tuberosity to correct the Class II malocclusion (length, 12 mm; diameter, 2 mm; Jeil Medical Corporation, Seoul, Korea) ( Fig 4 , A and B ). These screws were inserted under local anesthesia at the start of treatment. Figure 4 , C shows the diastema produced by the distalization effect of the miniscrews. After 6 months, a Class I relationship was achieved, so the miniscrews were removed.

Aug 20, 2020 | Posted by in Orthodontics | Comments Off on Miniscrew mechanics for molar distalization and incisor intrusion in a patient with a Class II brachyfacial pattern and gummy smile
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