Title	Clear Aligner Therapy Results in Less Favorable Outcomes for Maxillary Expansion in Mixed Dentition Patients as Compared to Traditional Rapid Maxillary Expanders
Clinical Question	What is the efficacy of clear aligner therapy (CAT) compared to tooth-borne Hyrax-type rapid maxillary expanders (RME) during treatment of maxillary transverse deficiency in mixed dentition patients (6-12 years old)?
Clinical Bottom Line	With evolving clear aligner technology, new products for palatal expansion have emerged, warranting evaluation of their clinical usefulness for patients. Clear aligner therapy (CAT), when compared to traditional rapid maxillary expanders (RME), showed less favorable outcomes in terms of maxillary expansion for early and mixed dentition patients. These findings underscore the importance of practitioners exercising careful discretion when selecting between CAT and RME, considering factors such as patient age, severity of maxillary constriction, and long-term stability goals. While CAT offers aesthetic advantages, clinicians must balance patient preferences with the clinical necessity for effective maxillary expansion, potentially considering hybrid approaches in complex cases to optimize treatment outcomes.
Best Evidence
PubMed ID Author / Year Patient Group Study type (level of evidence) 39066746 Bruni/2024 41 mixed dentition patients Randomized Controlled Trial Key results The study compares the effectiveness of clear aligner therapy (CAT) and rapid palatal expanders (RME) in treating posterior transverse discrepancies (interarch discrepancy of ≤6mm) in mixed dentition patients. It found that both treatments significantly improved palatal volume and surface area, but RME showed a greater increase in palatal volume (532.01 ± 540.52 mm³) compared to aligners (243.95 ± 473.24 mm³), although this difference wasn't statistically significant (P=0.084). The only significant difference was in intermolar width at the gingival level, favoring RME. Overall, RME appeared to yield better outcomes, suggesting its superiority for achieving desired palatal changes in young patients. 39230021 Torbaty/2024 80 mixed dentition patients and 40 controls Retrospective cohort study - Level 3 Key results Cases came from the American Association of Orthodontists Foundation Craniofacial Growth Legacy Collection. The study compared vertical and transverse changes in mixed dentition patients treated with the Invisalign First System (IFS), Hyrax expander, and a control group. Regarding vertical changes, both the control and IFS groups showed similar reductions in mandibular plane angle (SNMPA decreased by -0.73 ± 0.51° in IFS), while the Hyrax group showed no significant changes. However, these differences among the three groups did not reach statistical significance (P=.06). In terms of transverse changes, the Hyrax group demonstrated significantly greater expansion in maxillary intermolar width compared to the IFS group (4.4 mm vs 2.5 mm). Maxillary expansion efficiency using IFS ranged from 52.3% to 76.87%, suggesting it can be effective for mild arch width deficiencies.
Evidence Search	Evidence Search("clear aligners" OR "Invisalign" OR "Invisalign first" OR "Invisalign palatal expander") AND ("RPE" OR "palatal expanders" OR "palatal expander" OR "Hyrax") AND ("mixed dentition" OR "adolescent" OR "orthodontic patients" OR "children")
Comments on The Evidence	The randomized controlled trial by Bruni et al. compares clear aligner expanders to rapid palatal expanders (RPE) in mixed dentition patients, showcasing several strengths in design and execution. It features a clear research question and included 41 patients (19 in the clear aligner group and 20 in the RPE group), with a low dropout rate of two participants from an initial sample of 43, enhancing validity. Treatment duration was standardized at 8 months for both groups, and validated measurement techniques assessed multiple outcomes related to palatal expansion. The study found minimal differences between the two methods for most outcomes, with the only statistically significant difference being in intermolar width at the gingival level (3.87 mm for RPE vs. 1.58 mm for clear aligners). However, limitations such as a small sample size, lack of assessment of skeletal changes, and a short follow-up period restrict the conclusions. There was a moderate effect size (d = 0.57) for the difference in palatal volume changes, suggesting a meaningful but not statistically significant difference. The effect size was lower than the expected effect size of 1.0, which indicates the need for larger sample sizes in future studies. In addition, the study mentions a risk of bias due to the short recruitment period of >6 months which could lead to confounding results due to physiological growth expected in this demographic and a lack of long-term follow-up to monitor relapse. The retrospective cohort study by Moravedje Torbaty et al. examined vertical and transverse changes in mixed dentition patients treated with the Invisalign First System (IFS) compared to those treated with Hyrax expanders. This study included 80 well-matched patients but may be subject to selection bias due to its retrospective design. The follow-up period was limited (mean 1.19-1.32 years), which may restrict long-term effect assessments. Despite these limitations, the inclusion of a control group strengthens the analysis by allowing comparisons with normal growth changes. Both studies provide valuable insights into the comparative effectiveness of clear aligners and rapid palatal expanders in mixed dentition patients with mild to moderate expansion needs. While RPE appears to offer greater skeletal expansion at the gingival level, clear aligners may provide advantages in terms of patient comfort and aesthetics. Further research with larger sample sizes and longer follow-up periods is essential to better understand the long-term efficacy and stability of these treatment modalities.
Applicability	The studies by Bruni et al. and Moravedje Torbaty et al. included mixed dentition patients requiring maxillary expansion, making their findings relevant for children and adolescents with transverse maxillary deficiency. Bruni's randomized controlled trial compared clear aligner expanders to rapid palatal expanders, while Moravedje Torbaty's retrospective study examined the Invisalign First System against Hyrax expanders. These insights are valuable for orthodontists but may be limited by small sample sizes, short follow-up periods, and lack of long-term stability assessment. The choice between clear aligners and traditional expanders may also depend on patient compliance, aesthetic preferences, and cost considerations. Clinicians should weigh individual factors, such as the severity of the deficiency and skeletal maturity, when selecting the most appropriate treatment method.
Specialty	(Orthodontics)
Keywords	clear aligners, Invisalign, Invisalign first, Invisalign palatal expander, RPE, palatal expanders, Hyrax, mixed dentition, orthodontics
ID#	3564
Date of submission	10/18/2024
E-mail	moreyj@livemail.uthscsa.edu
Author	Justin Morey
Co-author(s)	Nika Rezaeikalantari
Co-author(s) e-mail	rezaeikalant@livemail.uthscsa.edu
Faculty mentor	Dr. Karakousoglou
Faculty mentor e-mail	karakousoglo@uthscsa.edu
Basic Science Rationale (Mechanisms that may account for and/or explain the clinical question, i.e. is the answer to the clinical question consistent with basic biological, physical and/or behavioral science principles, laws and research?) None available
Comments and Evidence-Based Updates on the CAT (FOR PRACTICING DENTISTS', FACULTY, RESIDENTS and/or STUDENTS COMMENTS ON PUBLISHED CATs) None available