Orthodontic treatment of gummy smile by maxillary total intrusion with a midpalatal absolute anchorage system

Abstract

This article describes the orthodontic treatment of a 31-year-old Korean female patient with gummy smile and crowding. The patient showed excessive gingival display in both the anterior and posterior areas and a large difference in gingival heights between the anterior and posterior teeth in the maxilla. To correct the gummy smile, we elected to intrude the entire maxillary dentition instead of focusing only on the maxillary anterior teeth. Alignment and leveling were performed, and a midpalatal absolute anchorage system as well as a modified lingual arch was designed to achieve posterosuperior movement of the entire upper dentition. The active treatment period was 18 months. The gummy smile and crowding were corrected, and the results were stable at 21 months post-treatment.

Keywords: Adult treatment; Lingual; Orthodontic mini-implant.

Figure 1

Pretreatment facial and intraoral photographs.

Figure 2

Pretreatment dental casts.

Figure 3

Pretreatment cephalometric and panoramic radiographs.

Figure 4

Photographs of bite opening before (A) and after (B) intrusion of the six mandibular anterior teeth.

Figure 5

Modified intrusive mechanics in the lingual segmented-arch technique. In the occlusal slots of the anterior and posterior lingual brackets, 0.018- × 0.018-inch stainless steel segmental wires were engaged. Additionally, 0.017- × 0.025-inch titanium-molybdenum-aluminum intrusion springs were engaged in the inner lingual slots of the first molar brackets and hooked to the anterior segment between the lateral incisors and canines to intrude the six mandibular anterior teeth. IS, Intrusive spring; AS, anterior segment; PS, posterior segment; BSS, buccal stabilizing segment.

Figure 6

Midpalatal absolute anchorage system for postero-superior movement of the maxillary dentition. A, Orthodontic force was applied postero-superiorly to the maxillary arch by attaching power chains from the hooks of the power arm to the spurs on the modified lingual arch; B, close-up view. SMS, Safe-multifunctional-solid screw; M-LA, modified lingual arch; PA, power arm; PC, power chain.

Figure 7

Dimensions of the safe-multifunctional-solid (SMS) screw implant. The SMS screw has a hexagonal head with two cross-shaped 0.032- × 0.032-inch slots. Its diameter is 2 mm and the available lengths are 4 and 5 mm, which can be varied depending on the thickness of the mucosa in the insertion area.

Figure 8

Posttreatment facial and intraoral photographs.

Figure 9

Before (A) and after (B) postero-superior movement of the maxillary dentition. Gummy smile was improved because of the postero-superior movement of the maxillary dentition. Note the decreased distance from the hooks of the power arm to the spurs on the modified lingual arch.

Figure 10

Posttreatment dental casts.

Figure 11

Pretreatment and posttreatment cephalometric superimposition. A, Overall superimposition on the Sella-Nasion plane at Sella; B, regional superimpositions on the palatal plane at ANS and on the mandibular plane at Menton.

Figure 12

Posttreatment cephalometric and panoramic radiographs.

Figure 13

Facial and intraoral photographs 21 months into retention.

Figure 14

Dental casts 21 months into retention.

Figure 15

Posttreatment and 21-month retention cephalometric superimposition. A, Overall superimposition on the Sella-Nasion plane at Sella; B, regional superimpositions on the palatal plane at ANS and on the mandibular plane at Menton.

Figure 16

Cephalometric radiograph taken after the midpalatal absolute anchorage system was placed in situ. CR, Collective center of resistance of the maxillary dentition; LAIF1, the line of action of the postero-superior orthodontic force distal to the center of resistance of the maxillary arch; LAIF2, the line of action of the postero-superior orthodontic force mesial to the center of resistance of the maxillary arch.

Figure 17

The effect of bracket position and location of the point of force application on tooth movement. In the labial system, the intrusive force against the incisors is applied anterior to the center of resistance and therefore the incisors tend to tip forward as they intrude. Lingual intrusive force is applied close to the center of resistance of the incisors and the incisors are well intruded with little flaring. The possibility of flaring of the incisors is lower with lingual than labial mechanisms. CR, Center of resistance; Fa, labial intrusive force; Fb, lingual intrusive force; m and M, moment.