Narrow palate. Transversal maxillary hypoplasia.

Jaw problems can be located on one of three planes: sagittal, vertical or transversal. In general, we find problems in a combination of the three. Transversal offset of the jaw is commonly associated with mandibular hypoplasia, maxillary hypoplasia or open bite. It is less common to find purely transversal problems, whether unilateral or bilateral.

Transversal maxillary problems normally result from problems in development, hereditary conditions or bad habits (excessive thumb sucking or atypical swallowing).

Diagnosis must be done clinically and with x-rays. The doctor must assess whether the transversal problem causes a uni or bilateral cross-bite, whether it is functional, dental or skeletal, or a combination. For skeletal cross-bites, the doctor must determine whether it is a problem of a narrow upper jaw and a normal lower jaw, a normal upper jaw and a wide lower jaw, or a narrow upper jaw and a wide lower jaw, in order to determine which arch must be treated.

For the assessment, a frontal x-ray must be done. Following Ricketts’ cephalometry analysis, we measure:

  • Effective mandibular width.

  • Effective maxillary width.

  • Difference between upper and lower jaw.

  • Index of difference between upper and lower jaw.

This way, we can find out whether it is a problem of the upper jaw or the lower jaw and whether it is best to treat it with surgery or orthodontics.

It is currently best to do a cone beam scan to study transversal issues.

Before treating a patient with a transversal maxillary condition, it is important to know how old the patient is and to what extent their maxillofacial sutures have ossified. The magnitude of the transversal problem must be quantified and corroborated with x-rays to study the patient’s periodontal state.

Transversal problems are more complicated to diagnose than vertical and sagittal, as the aesthetic impact is less obvious. With a vertical problem, the patient has a very clear gummy smile. In patients with sagittal anomalies, we can see exaggerated projection of the chin. The aesthetic changes observed in patients with purely transversal maxillary problems are limited to orifices and a narrow nasal base.

Methods used to correct transversal problems

  • Orthopaedic maxillary expansion
  • Coronal inclination
  • Mandibular narrowing
  • Surgical maxillary expansion, whether with SARPE (Surgically Assisted Rapid Palatal Expansion) or segmental LeFort I osteotomy

One method or the other will be chosen, depending on the scope of the problem, patient’s age and periodontal state.

Orthopaedic maxillary expansion is done in patients under 18 who need expansion of 4 mm or more. In older patients, it creates excessive inclination of the molars towards the vestibular, with the associated periodontal problems and tendency to relapse. With orthopaedic maxillary expansion, the canine area is expanded more than the molar (3:2) and includes skeletal changes (opening the suture), dental changes (inclination) and alveolar changes (remodelling). We recommend overexpansion of nearly 50% due to the huge potential for relapse with this treatment.

The transversal discrepancy is corrected with dental inclination and dento-alveolar remodelling in patients needing expansion

Surgical maxillary expansion is used when the transversal discrepancy is >5  mm. We also recommend surgical maxillary expansion if orthodontic/orthopaedic treatment has failed. Patients with extremely thin gum tissue or receding gums at the canines and premolars, and patients under 15.

It has been proven that surgical treatment is more stable and yields better results than orthodontic treatment in patients with transversal maxillary problems.

The two most common methods used for a transversal maxillary expansion are SARPE (Surgically Assisted Rapid Palatal Expansion) and segmental LeFort I osteotomy.

SARPE is indicated for:

  • Failed orthodontic treatment.

  • Transversal maxillary problem in adult patients >5 mm.

  • Difference >7 mm.

  • Adult patients with narrow upper jaw and wide lower jaw. Most transversal discrepancies present with a narrow upper jaw and sharp, pronounced arches at the canine level. For functional occlusion, the intercanine distance must be increased and the incisive sector retracted for a more elliptical arch shape. The interdental periodontal problems as a result of SARPE are minimal and there is no need for distalisation of the canines, as is the case with segmental LeFort I osteotomy.

  • Patients with oseo-dental and incisor discrepancy are also good candidates for SARPE, as the LeFort I osteotomy would require cutting the anterior segment leaving them vulnerable to a possible change in incisor position.

It must be taken into account that patients with maxillary tori must have them removed surgically (4-6 months beforehand or as part of the same surgery) and they must be considered when establishing the treatment protocol. If, in addition to the SARPE, any other surgery is necessary for vertical or sagittal problems, the osteotomies must be done at the same level as those planned for the next surgery to ensure the bone is intact for anchoring the tiny plates or screws.

Even though the surgically assisted rapid palatal expansion is more stable, there are cases that call for a segmental LeFort I osteotomy. In patients who need maxillary expansion associated with another sagittal or vertical problem. This is also the surgery of choice in cases with a discrepancy >7  mm who also need surgical levelling of the Spee curve.

If we want greater expansion at the canine level, we will do an SARPE; if we want greater expansion at the molar level, the best choice is the segmental LeFort osteotomy. Treatment with SARPE is faster and can prevent the need for extractions in arches with oseo-dental discrepancies. For patients that will be undergoing a LeFort treatment, an orthodontic levelling must be done beforehand and extractions in the case of negative discrepancies.

Each patient must be studied carefully to know exactly how much expansion we need. It is important to eliminate mandibular dento-alveolar compensations as they could mask proper maxillary expansion.

We must remember that, when operating on the maxillary area, we are altering the proportions of the middle third of the face, including the distance between the nose and its tips, the width of the base and the naso-labial angle.

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