Nonsurgical treatment of an adult with skeletal Class III malocclusion, anterior crossbite, and an impacted canine

Class III malocclusion presents some complexity in terms of diagnosis and treatment and affects not only the jaws but the whole craniofacial complex. Besides, functional forward displacement of the mandible may be diagnosed in a patient presenting Class III malocclusion, as the 2 entities are not incompatible or mutually exclusive. This case report describes the multidisciplinary, nonsurgical, orthodontic treatment of an adult patient with a skeletal Class III malocclusion, anterior crossbite, and a palatally impacted canine, treated with fixed appliances and skeletal anchorage. To upright the mandibular molars, distalize the whole mandibular arch, and avoid excessive inclination of maxillary incisors to improve dentofacial esthetics, miniscrews were placed in the retromolar area. The treatment results were very satisfactory and remained stable after a reasonable retention period.

Highlights

  • Class III malocclusion presents some complexity in terms of diagnosis and treatment.

  • Adequate incisor torque is crucial to improve esthetics in Class III malocclusions.

  • Microscrews were used to distalize the whole mandibular arch.

  • Spontaneous eruption can be performed in adult patients with superficial canines.

Class III malocclusion has a prevalence ranging between 1% and 19% worldwide, and between 1% and 5% among Caucasians. The skeletal causes of Class III malocclusion are maxillary hypoplasia, mandibular hyperplasia, or a combination of both, and for dentition, Class III malocclusion involves proclination of the maxillary incisors and retroclination of the mandibular teeth, which then seek dentoalveolar compensation. This malocclusion is of the most complex to diagnose and treat as it affects not only the jaws but the whole craniofacial complex. ,

Pseudo-Class III malocclusion is characterized by the presence of an anterior crossbite due to a forward functional displacement of the mandible. When the patient is brought to a central relation, edge-to-edge bite is frequent, but the patient displaces the mandible forwards, seeking adequate occlusion in the posterior regions.

With regard to treatment options for adult patients with Class III malocclusion, orthognathic surgery or dentoalveolar compensation may be considered. The choice of treatment approach is a decision that should be made by the patient under the guidance of the orthodontist and maxillofacial surgeon, and depending on the severity of the skeletal anomaly, the amount of negative overjet, incisor inclination, and dentoalveolar esthetics.

Miniscrews present many advantages as they can be safely placed in many locations, can be loaded immediately, are easy to place and remove, and are reasonably economical. , The conventional mechanics involved in distalizing the mandibular arch are never straightforward, but the skeletal anchorage provided by miniscrews has greatly simplified the process.

The prevalence of maxillary canine impaction is 1.7%, with a third of the teeth located buccally and two thirds palatally. Its treatment requires cooperation between the surgeon and orthodontist. Choosing the correct exposure technique will simplify the eruption process and will achieve a predictable and esthetically acceptable outcome.

In closed surgical exposure, orthodontic traction is performed immediately after surgery. In open exposure, traction is performed after the canine has erupted freely in the palate. With both techniques, a first surgical phase approaches the canine, freeing it from the bone around its coronal portion. Open exposure of palatally impacted canines with spontaneous eruption offers certain advantages, such as less post-reexposure, a shorter treatment time, and better hygiene maintenance during treatment.

This case report describes the multidisciplinary, nonsurgical orthodontic treatment of an adult patient with a skeletal Class III, anterior crossbite, and a palatally impacted canine, treated with fixed appliances and skeletal anchorage to distalize the whole mandibular arch, prevent excessive proclination of the maxillary incisors, and so improve dentofacial esthetics.

Diagnosis and etiology

This case report describes a 34-year-old male who came to the clinic for (in his own words) the following reason: “I have a tooth in my palate, and I don’t like the gap.” He did not mention his anterior crossbite at all and said it did not concern him “in the slightest.”

Facial photographs showed a well-proportioned face, symmetrical, with a slightly enlarged lower third. The patient’s smile exposed almost all the maxillary incisors without any gum. The facial profile was straight, observing a mesofacial-type patient with a slightly everted lower lip. Slight malar projection was also noted, a common finding in patients with maxillary hypoplasia ( Fig 1 ).

Fig 1
Pretreatment facial and intraoral photographs.

Intraoral photographs and study models showed a bilateral Class III molar relationship with retroclined mandibular incisors and proclined maxillary incisors. In addition, the patient presented posterior crossbite in the premolar area, and complete anterior crossbite, as well as increased overbite (4 mm). Both the maxillary and mandibular dental midlines were centered in relation to each other and the face. There was a mild tooth size-arch length discrepancy in the maxillary anterior arch (−3 mm) and moderate discrepancy in the mandibular arch (−4 mm). The maxillary incisors presented some wear derived from the crossbite, whereas the mandibular incisors showed no wear. The maxillary right canine was palatally impacted, and the maxillary left second premolar had been extracted because of caries ( Figs 1-3 ). Periodontal assessment observed that the patient initially presented poor oral hygiene, with active periodontitis, 4 mm pockets in the posterior regions, and 24% bleeding, which improved significantly after periodontal treatment.

Fig 2
Pretreatment study models.

Fig 3
Pretreatment lateral cephalogram and cephalometric tracing (A) , panoramic radiograph (B), and cone-beam computed tomography reconstruction (C) .

Cephalometric analysis identified a skeletal Class III (ANB −4.3°; Wits −10.2 mm) with a meso-face (facial axis = 91.0°; FMA = 17.1°; anterior face height = 116.6 mm). The maxillary and mandibular incisors were retroclined (SN-U1 = 101.2°; IMPA = 86.0°) ( Fig 3 , A ; Table ).

Table
Norm, pretreatment, posttreatment and postretention cephalometric summary
Measurement Norm Pretreatment Posttreatment Postretention
SNA angle (°) 82.0 85.9 85.9 85.9
SNB angle (°) 80.0 90.2 87.9 87.9
ANB angle (°) 2.0 −4.3 −2.0 −2.0
Wits appraisal (mm) 0.0 −10.2 −6.1 −6.5
SN-U1 (°) 103.0 101.2 120.0 119.0
IMPA (L1-Mp) (°) 95.0 86.0 84.0 84.0
Interincisal angle (°) 130.0 136.7 130.2 130.5
Overjet (mm) 2.5 −3.9 1.4 1.3
Overbite (mm) 2.5 5.1 0.2 10.2
Facial axis (NaBa-PtGn) (°) 90.0 91.0 89.0 89.0
FMA (MP-FH) (°) 25.0 17.1 21.7 21.5
Occlusal plane angle (SN-OP) (°) 14.0 7.0 9.2 9.0
Total anterior facial height (N-Me) (mm) 110.0 117.4 120.1 120.2
Upper anterior facial height (N-ANS) (mm) 50.0 52.1 49.9 50.0
Lower anterior facial height (ANS-Me) (mm) 66.0 65.3 69.2 69.1
Mandibular length (Go-Gn) (mm) 78.0 79.5 79.4 79.5
Upper lip-E line (mm) −8.0 −9.0 −9.4 −9.3
Lower lip-E line (mm) −2.0 −5.5 −5.5 −5.5

Functional analysis observed that in centric relation, the patient reduced the anterior crossbite, reaching slight incisal edge-to-edge contact ( Fig 4 ). No lateral shift was observed.

Fig 4
Patient’s occlusion in central relation.

A panoramic radiograph showed an impacted maxillary right canine, and the absence of the maxillary left second premolar. Both left third molars were impacted ( Fig 3 , B ).

Cone-beam computed tomography images showed the superficial palatally impacted position of the maxillary right canine, this being a favorable position for traction ( Fig 3 , C ).

The mandibular third molars and maxillary right third molar were extracted before treatment because of caries and periodontal reasons.

On the basis of these findings, the patient was diagnosed with skeletal Class III of maxillary origin, anterior crossbite with functional component and posterior crossbite, augmented overbite, and a palatally impacted maxillary right canine.

Treatment objectives

The treatment objectives were to expose the palatally impacted canine, establish a dental and skeletal Class I relationship, obtain adequate overjet and overbite, as well as maxillary and mandibular incisor torque, and correct facial harmony and esthetics.

Treatment alternatives

The first treatment option considered was a surgical approach using LeFort I advancement, but this was rejected by the patient. In skeletal malocclusions, orthognathic surgery should be explained to the patient as a first alternative; however, when facial esthetics are not conditioned by the malocclusion or the patient is not particularly concerned with esthetics, it is common for the patient to reject surgery.

To correct the sagittal problem, we considered treatments both with and without extractions. To avoid extractions, bearing in mind that the third molars had already been extracted, we performed distalization of the mandibular arch with miniscrews, placed distally to the mandibular second molars. This approach allowed the amount of distalization and anchorage to be better controlled.

Open exposure was performed to correct the impacted maxillary canine, allowing its spontaneous eruption. Traditionally, exposure and immediate traction are only possible in patients in growth. Open exposure can only be performed in adult patients when the canine is positioned superficially, after which the canine will erupt spontaneously in due course.

Because of the dental wear, the patient had suffered, the possibility of reconstructing the 4 maxillary incisors was considered, as well as reducing the mamelons of the mandibular incisors, which had not suffered any wear as a result of anterior crossbite.

Because of the state of the maxillary right second premolar, placement of a provisional crown was discussed, but this was rejected by the patient because of cost; this was to be restored with a zirconia crown after orthodontic treatment. It was decided to replace the missing maxillary left second premolar with an implant or bridge after orthodontic treatment.

Treatment progress

First, exposure surgery of the maxillary right canine was performed, eliminating all the tissue surrounding the crown and placing provisional cement (Fermin; Detax, Ettlingen, Germany) to prevent the open exposure from closing. Three months later, the canine erupted spontaneously. At this point, composite stops were placed on the maxillary first molars to open the bite and avoid debonding of the maxillary anterior brackets. Then, Tip-Edge Plus 0.022 × 0.028-in brackets (TP Orthodontics Inc, La Porte, Ind) were bonded on the maxillary arch. Because of the favorable position of the canine, direct traction to a nickel-titanium (NiTi) 0.016-in archwire was applied using transparent elastics (ODP, Vista, Calif) applying very soft forces. Afterward, a 0.016 × 0.022-in NiTi archwire was used to bring the canine into the arch ( Fig 5 ).

Apr 19, 2021 | Posted by in Orthodontics | Comments Off on Nonsurgical treatment of an adult with skeletal Class III malocclusion, anterior crossbite, and an impacted canine
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