Clear Aligners Paired With Skeletal Expansion Treat Narrow Palates in Adults

Orthodontists in a newly published case series report that combining Invisalign clear aligners with three different maxillary expansion protocols produced the planned orthodontic outcomes in three adult patients with transverse maxillary deficiency. The series, published on 3 June 2026 in the open-access journal Digital and Aligner Orthodontics, describes one patient treated after miniscrew-assisted slow palatal expansion, one after surgically assisted rapid palatal expansion, and one after surgical expansion performed during a full Le Fort I osteotomy. The authors, Waddah Sabouni and Heba M Al-Ibrahim, argue that precise diagnosis, appropriate expander selection and correct activation protocols were crucial to the success of each case.

Maxillary constriction, a narrowing of the upper jaw in the transverse dimension, is among the most common problems orthodontists face. In children, a narrow maxilla can often be corrected with dentoalveolar or skeletal expansion, depending on the type and severity of the constriction. In young and adult patients, however, the midpalatal suture gradually interdigitates after puberty, making expansion more difficult. The authors emphasize that the timing of suture fusion varies considerably between individuals, with research indicating that the stages of midpalatal suture development are not strictly linked to chronological age, so suture maturation should be assessed individually before expansion, especially in late adolescents and young adults, to minimize the risk of expansion failure or unnecessary surgery.

The treatment options available to adults fall into several categories. Slow maxillary expansion applies constant, light physiological forces over a relatively long period, with minimal pressure on the teeth; it primarily induces dentoalveolar changes but also produces some skeletal changes, and it is reported to improve patient acceptance and post-expansion stability. Rapid maxillary expansion aims to separate the midpalatal suture within a short period using heavier forces, but it carries disadvantages including pain, a higher possibility of relapse, and the inability to open the suture in many cases. When the suture is fused, surgically assisted rapid maxillary expansion, or SARPE, has become a popular and accepted method in young and adult patients requiring skeletal expansion, and recent research has also demonstrated the effectiveness of bone-borne expansion in non-growing patients.

Clear aligners have grown in popularity because patients seeking comfortable and esthetic orthodontic treatment increasingly choose them. Dental arch expansion is achievable with aligner therapy, but previous findings indicate that expansion is greater at the cusp tips than at the gingival margins, meaning aligner-induced arch expansion results mainly from dentoalveolar tipping rather than bodily movement. A recent systematic review cited in the paper indicates that maxillary expansion achieved with clear aligners is predominantly dentoalveolar, occurring mainly through buccal tipping of the posterior teeth, and that virtual treatment setups frequently overestimate the extent of expansion compared with actual clinical results. Excessive buccal tipping may lead to gingival recession, increased vertical dimension and occlusal interferences, and adverse effects such as dehiscences, fenestrations and reduced buccal alveolar bone thickness have been observed in many cases following upper jaw expansion.

Because of these biomechanical limitations, the authors note that transverse expansion with clear aligners should typically be limited to around 2 to 3 mm per quadrant to promote long-term stability and reduce the risk of periodontal problems. In cases requiring greater expansion, adjunctive skeletal techniques should be integrated with aligner therapy. The number of published papers on clear aligners assisted by other expansion techniques remains low, however, with most scientific evidence focused on traditional expanders or fixed appliances, which the authors identify as the rationale for documenting these three cases.

The first case involved a 35-year-old man who presented with anterior open bite, maxillary constriction and dental crowding of roughly 9 mm in the upper jaw and 6 mm in the lower jaw, along with crossbites affecting molars, premolars and lateral incisors. The team chose Invisalign aligners combined with miniscrew-assisted slow palatal expansion, or MASPE, using a custom-designed bone-borne palatal expander supported by four miniscrews placed in the hard palate. The slow expansion protocol applied one activation every three days for two months, producing a total of 5 mm of expansion. Post-expansion CBCT imaging revealed the palatal expansion without loss of bony support around the teeth. Because the expander was bone-borne and did not interfere with tooth movement, aligner treatment could begin with the first aligner, and the expander remained in place for six months after expansion.

The aligner phase for this patient consisted of one main phase of thirty-eight aligners for both arches and a refinement phase of twenty-one additional aligners, with vertical elastics introduced bilaterally during refinement to aid occlusal settling. Post-treatment records showed notable improvement, including significant correction of the anterior open bite and improved dental alignment, but the open bite was not completely closed, and some root resorption was noted on the post-treatment panoramic radiograph. Superimposition showed maxillary expansion in both anteroposterior and transverse directions, and overall active treatment time was 13.5 months. The authors state that the miniscrew-assisted slow expander, in combination with Invisalign, enabled non-surgical correction of the transverse deficiency and crossbites without harmful effects on the periodontium, results they argue could not have been attained with clear aligners alone.

The second case involved a 25-year-old man with maxillary constriction, anterior and posterior crossbites, and severe crowding in both arches. Treatment consisted of SARPE followed by Invisalign aligners. The patient underwent a one-hour surgical procedure under general anesthesia in which a Le Fort I osteotomy was applied without separation of the pterygomaxillary junction, according to the Betts technique. A transpalatal distractor was placed at the level of the upper premolars, and expansion of 0.3 mm per day began one week after surgery, achieving approximately 6 mm of total expansion after twenty expansion days. Post-expansion CBCT again showed expansion without loss of bony support. The aligner treatment ran through one main phase and four refinement phases, using sixty-seven upper and lower aligners worn 22 hours daily and changed every seven days, supplemented by class II, vertical, cross and triangular elastics and, in the third phase, a sectional fixed appliance on three lower teeth. Total active treatment time was 35.9 months, culminating in what the authors describe as satisfactory clinical outcomes.

The third case, another 25-year-old man with maxillary constriction, crowding and a Class III molar relationship bilaterally, required surgical expansion rather than SARPE alone, because the surgeon needed to perform a full Le Fort I osteotomy to achieve maxillary intrusion and surgical expansion simultaneously. A 3D-printed bonded Hyrax expander was applied the day before surgery at the level of the first and second molars, where more expansion was needed, and the surgeon performed the required 5 mm expansion during the operation. The aligner treatment covered the posterior teeth and portions of the expander, with no intention to move the posterior teeth or alter the surgical expansion, and the expander stayed in place for six months. Treatment was completed in one main phase and four refinement phases using twenty-four upper and lower aligners with class II and vertical elastics, achieving all treatment objectives in 19 months of active treatment, according to the authors.

The authors conclude that the case series illustrates the clinical viability of combining skeletal expansion methods with clear aligner therapy to treat maxillary transverse deficiency in adults, and that the integrated approach can enhance treatment efficiency and extend aligner-based orthodontics beyond the biomechanical limits of clear aligners alone. They caution, however, that outcomes depend greatly on proper case selection, biomechanical planning and patient compliance, and they stress that further research is necessary to validate these results across diverse patient populations, confirm their clinical importance and establish their generalizability. As a case series of three patients, the report documents individual clinical decision-making and observed outcomes rather than controlled evidence of efficacy, and the authors note that anterior open-bite correction in adults remains challenging due to limitations in vertical control and the reduced efficiency of extrusion movements with clear aligners, often requiring overcorrection or auxiliary mechanics.

Subject of Research: Combining Invisalign clear aligner therapy with different maxillary expansion protocols to treat transverse maxillary deficiency in adults

Article Title: Incorporation of Invisalign system with different maxillary expansion principles and protocols in adult patients: a case series

Article References: Sabouni, W., & Al-Ibrahim, H. M. (2026). Incorporation of Invisalign system with different maxillary expansion principles and protocols in adult patients: a case series. Digital and Aligner Orthodontics, 1(1), Article 3. https://doi.org/10.1007/s44525-026-00005-5

Image Credits: AI Generated

DOI: 10.1007/s44525-026-00005-5

Keywords: clear aligners, Invisalign, maxillary expansion, maxillary constriction, SARPE, miniscrew-assisted slow palatal expansion, orthodontics, midpalatal suture, Le Fort I osteotomy, adult patients, case series, dentoalveolar tipping