CE Eligible Article The Why’s & How’s of PEDIATRIC TRANSVERSE Part I: Ages 3 to 5 DEVELOPMENT By Jeffrey Dahm, DDS, and Ross Johnson, DDS, MSD P rior to the mid-19th century, irregularities of the teeth and jaws were primarily concerned with the alignment of teeth. 1 In 1860, Emerson Angell became the first to successfully open the midpalatal suture. 2 Ever since, the profession has been attempting to open midpalatal sutures, expand arches and increase arch length with a menagerie of appliances. Regardless, the traditional indica-tion for maxillary expansion remains the same: a posterior crossbite/narrow palatal vault. 3 This indication, while valid, misses so many other aspects of an underlying need for maxillary skeletal expansion that can be appar-ent when looking at the same skeletal structures with CBCT. The purpose of this article is to discuss why we skeletally expand in patients who do not have posterior crossbite, how that expansion can be accomplished, and what the skeleton looks like after expansion. Our focus in this article will be on children 3 to 5 years old. lar advancement procedures with functional appliance ther-apy or mandibular advance-ment surgery. 4. Address a dysfunctional pterygomasseteric sling. In summary, the goals of maxillary skeletal expansion include optimiza-tion of the airway to help patients with sleep-disordered breathing. Many techniques and appliances have been used for dental arch expansion, with various proposed protocols, and it is important for the practitioner to understand the biomechanical effects of these appliances for patients of all ages. There are two major divisions of expansion appliances: fixed appli-ances and removable appliances. Fixed appliances include: • Fixed braces with archwires. • Fixed appliances with dental anchorage, such as banded rapid palatal expansion (RPE) with Hyrax screw or fixed spring activated appliances, such as NPE or Quad Helix. • Hybrid anchorage appliances, such as MARPE with cemented bands. • Solely skeletally anchored expansion appliances, such as MSE or custom MARPE without bands to fixate the appliance to the dentition. Removable appliances include: • Acrylic and wire appliances, such as Schwarz expanders and all variants of the design. • Aligner appliances. Biomechanical Effects of Transverse Expansion Appliances When evaluating movements achieved with dental expansion appliances, several types of move-ment are possible: 1. Dental tipping. 2. Tipping of the dental-alveolar structures. 3. Transverse movement of the roots through the alveolar bone and/or buccal plate. 4. In the maxillary arch, midpalatal suture separation with transverse skeletal devel-opment of the dental arch and the apical base zone of the maxilla which houses the nasal airway. Historically, traditional RPE devices were placed in adolescent patients with bands on the first molars and first bicuspids. These were activated 1 to 2 times per day until the desired arch width was achieved. In mixed dentition, these appliances achieve reliable palatal suture separation; however, by the mid-teens, the appli-ances achieve midpalatal suture sepa-ration in up to 50% of patients. The remaining patients experience a fail-ure of midpalatal suture separation and expansion based only on dental tipping, dental-alveolar tipping, and tooth movement through the alveolar bone and cortical plate. Patients treated with RPE neverthe-less often report improved nasal breathing, but this can occur at the expense of the supporting periodon-tium, potentially leading to fenestra-tions and dehiscence of the buccal cortical plate. The anterior zone of Keys to Understanding The goals of maxillary skeletal expansion have extended beyond correction of posterior crossbite in our current era of maxillofacial ortho-pedics. Now, the intent of maxillary expansion is to: 1. Increase the transverse width of the nasal cavity and mid-face. 2. Increase tongue room for proper positioning of the tongue. 3. Correct upper to lower trans-verse dental arch width discrep-ancies to allow future mandibu-26 Summer 2026 JAOS
Journal of the American Orthodontic Society Summer 2026: Page 26
