Transversal Extension of the Upper Jaw

Transversal expansion of the upper jaw refers to all orthodontic treatment measures that promote the width growth of the upper jaw. Causative factors for a maxilla restrained in transversal development include quite a few, such as:

A too narrow upper jaw can result in a narrowing of the upper teeth on the one hand, but also affect the position of the teeth in the lower jaw and its position. Comparable to a too narrow shoe, in which the foot can not slide all the way forward, a normally developed lower jaw in width growth is held in a forced recession when the upper jaw is transversely narrowed. If the mandible positions itself correctly, this results in a unilateral or bilateral crossbite in the posterior region, with the buccal (outer) cusps of the lower teeth reaching over the upper buccal cusps. Both a mandibular recession and a crossbite have, in turn, an unfavorable effect on the development of the jaw bones during the child’s growth phases, because skeletal fixation of the tooth malocclusions can occur. Asymmetries can develop, even the statics of the cervical spine and the entire holding apparatus can be disturbed. Thus, the lack of transversal development of the maxilla has far-reaching consequences.

Indications (areas of application)

Based on these considerations, the following indications for transverse expansion of the maxilla are given:

  • Maxillary micrognathia (too small upper jaw).
  • Mandibular macrognathia (too large lower jaw).
  • Narrowness in the upper dental arch with a normally developed lower jaw.
  • Forced recession of the mandible
  • Crossbite unilateral or bilateral
  • Lateral forced bite

The procedures

The goal of transversal expansion is to achieve a maxillary arch that is matched in skeletal width to the mandibular arch. In simple cases, the treatment goal can be achieved with removable appliances, while more restrained width growth requires fixed appliances, accompanied by surgical procedures in extreme cases. Removable appliances:

  • Active plate with transversal screw, which is regularly activated by the patient himself.
  • Removable transpalatal arch: Application only possible in deep bite, as the first molars are tilted buccally (outward) and the front opens slightly. The primary objective of the arch is the correct positioning of the first molars.

Fixed appliances:

  • Fixed transpalatal arch: like the removable transpalatal arch, serves to position the first molar (molar) and increase the transversal dimension (width) of the maxilla; is worn permanently via cemented molar bands and is a better fit than its removable counterpart.
  • Quadhelix: a wire framework running transversely (across) the palate is attached to the six-year molars (the first large permanent molars) with metal bands; the design has four coils and is activated by the orthodontist during check-up sessions. In this process, the dental arch can be expanded to different degrees in the anterior (front) and posterior (back) parts. In addition, the right and left sides of the dental arch can be affected to different degrees. In very young patients with barely fused palatal suture, the quadhelix has a palatal widening effect.
  • Palatal suture expansion (GNE): in unilateral or bilateral crossbite, in extreme cases already from the age of 4 until adulthood, as long as the sutura palatina media (palatal suture) is not yet completely ossified. The so-called Hyrax appliance transmits the force of a special screw via wire stiffeners to metal bands cemented to both sides of the first premolars and first molars. As a result of the force, the bony palatal segments connected via the suture separate, while the mucosal covering remains intact. The typical sign of a successful GNE is the diastema (gap) that develops between the two central incisors, which subsequently closes by itself through connective tissue traction or is otherwise treated.The palatal suture is ossified again after about three months.

Surgical support:

  • An ossified palatal suture must be surgically weakened before expansion, as the otherwise too stable bony interlocking of the palatal segments prevents separation. Surgical pretreatment of the GNE must usually be performed in adults.
  • Distraction osteogenesis: if the maxillary teeth cannot be expected to bear the load of a hyrax appliance for GNE, then so-called transpalatal distractors (TPD) are used, either self-fixing or with the help of osteosynthesis screws (screws used to join bone fragments) on the hard palate. The force acting via distractors attaches directly to the bone and thus has its center of force closer to the base of the maxilla and the floor of the nose than the force of the hyrax screw, which attaches to the tooth crowns. This eliminates tooth tilting, and also expands the stable bone at the base of the upper jaw, which results in a comparatively better recurrence prophylaxis (prevention against re-development into a narrow jaw) after a three- to four-month wearing period.

Further notes

  • Neither palatal expansion, surgically assisted palatal expansion, nor maxillomandibular repositioning osteotomy is indicated in the treatment of obstructive sleep apnea (no robust evidence).