INTRODUCTION: Maxillary transverse deficiency (MTD) is a common craniofacial condition associated with posterior crossbite, dental crowding, and compromised respiratory function. This study aimed to evaluate whether the Invisalign Palatal Expander (IPE) can induce midpalatal suture opening and occlusal changes, and to compare these outcomes with those obtained using conventional rapid palatal expansion (RPE).
MATERIALS AND METHODS: Thirty subjects (14 females, 16 males; aged 6-18 years) with mixed dentition were enrolled and divided into two groups: 15 treated with IPE and 15 with RPE. Radiographic images and digital dental models were analyzed before (T0) and after treatment (T1) to assess skeletal and occlusal changes, including midpalatal suture opening and transverse arch dimensions. Molar tipping and palatal depth were also measured. Patient-reported side effects during the first month of treatment were evaluated using a questionnaire addressing bulkiness, tongue impression, dysphonia, dysphagia, and gag reflex, scored on a 1-5 scale. Inclusion criteria comprised mixed dentition, erupted first molars, deciduous fourth/fifth teeth or erupting premolars, and complete diagnostic records. Exclusion criteria included previous orthodontic treatment, craniofacial anomalies, extraction therapy, allergies, hereditary angioedema, or active caries.
RESULTS: No significant differences were found between groups in the number of activations, radiographic outcomes, or theoretical expansion, indicating comparable skeletal effects. Midpalatal suture opening was achieved in all patients. Baseline occlusal conditions were similar between groups. After normalization for the number of activations, statistically significant differences were observed for arch depth, canine gingival width, canine dental width, and arch perimeter, all of which were greater in the RPE group (p < 0.05). No significant differences were found in intermolar angle or palatal depth changes. Questionnaire analysis revealed no significant differences in reported side effects between groups.
CONCLUSIONS: The Invisalign Palatal Expander effectively produced transverse maxillary expansion with midpalatal suture opening, yielding skeletal and occlusal outcomes comparable to those of the Hyrax expander. Although the amount of expansion was slightly lower, the IPE demonstrated more controlled and predictable results, supporting its use as a valid alternative in mixed dentition and as a step toward fully digital orthodontic protocols.
Midpalatal suture opening was achieved in all patients.
direct within-sample observation from a small non-randomized pilot using corrected occlusal radiographs
The observed outcomes were largely comparable to those achieved with rapid maxillary expansion using a Hyrax expander for most occlusal parameters and for all radiographic parameters evaluated.
comparability inferred from underpowered null tests in uncontrolled, imbalanced treatment groups
Although the amount of expansion was slightly lower, the IPE demonstrated more controlled and predictable results, supporting its use as a valid alternative in mixed dentition
predictability and clinical validity exceed what confidence-interval width and a 30-patient pilot establish
Derived from the full evaluation — not a separate score.
Strengths
Occlusal radiographs showed midpalatal suture opening in the analyzed patients, supplying initial clinical evidence for a newly introduced removable expander.
↳ Results, Radiographic Analysis; Discussion, midpalatal-suture paragraphs
Radiographic measurements were corrected against the actual size of tooth 2.1, while digital models supplied the anatomical reference and occlusal measurements.
↳ Materials and Methods, Study Design
The Discussion connects small sample size, immediate follow-up, and absent three-dimensional imaging to limits on power, generalizability, stability, and spatial skeletal characterization.
↳ Discussion, limitations paragraph
Limitations
Treatment allocation is not described, and the Hyrax and IPE groups have markedly different sex distributions without adjustment, matching, or sensitivity analysis.
↳ Materials and Methods, Sample and Study Design; Results, opening paragraphs
The paper interprets non-significant differences as comparable outcomes despite analyzing 30 participants when its own calculation specifies 56 for 80% power.
↳ Abstract, Results and Conclusions; Sample Size
The limitations section discusses sample size, follow-up, imaging, and pain assessment but does not trace the undisclosed allocation process or sex imbalance through the head-to-head interpretation.
↳ Results, opening paragraphs; Discussion, limitations paragraph
The paper contributes initial clinical evidence that IPE can produce radiographically observed midpalatal suture opening, supported by proportional image correction and high reported inter-observer agreement. Its head-to-head interpretation is much less secure because treatment allocation is unstated and the final groups differ markedly in sex composition without adjustment. The reported power calculation requires 56 participants, so non-significant tests among 30 participants do not establish equivalence or predictability. The limitations discussion is otherwise substantive, but omitting allocation and baseline imbalance materially narrows the defensible comparative conclusion.
Nabu’s assessment, alongside the field’s view.
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Limited2.8
Confidence highThe study provides initial direct evidence that IPE can produce radiographically observable midpalatal suture opening and compares it with Hyrax. The advance remains preliminary because the analyzed sample is below the stated power requirement and does not establish equivalence.
“Midpalatal suture opening was achieved in all patients.”
Pre/post imaging, proportional radiographic correction, digital-model measurements, and inter-observer assessment support measurement execution. Undisclosed allocation, unadjusted sex and age imbalance, and unexplored differential exclusions leave the primary group comparison without a credible confounding strategy.
“Participants were divided into two groups of 15: the Hyrax group (10 females, 5 males) and the IPE group (4 females, 11 males).”
The methods, outcomes, and discussion follow a traceable structure, but headline wording treats underpowered null tests as comparability and presents IPE as a valid alternative. The Conclusions are more cautious than the Abstract, creating calibration drift in the central message.
“supporting its use as a valid alternative in mixed dentition”
The Discussion compares measured parameters with relevant expansion literature and traces several limitations to power, generalizability, stability, and imaging resolution. It does not acknowledge the undisclosed allocation process or marked sex imbalance when attributing between-group differences to the appliances.
“the differences observed at the end of treatment can be attributed primarily to the effects of the appliances used.”
Lower confidence on Contribution, Positioning — domain match limited.
Caveats4 of 4 checks
The reported observations are broadly coherent, but the comparative interpretation is less secure than the numerical presentation suggests. Baseline imbalance, inadequate power for null comparisons, and an unresolved citation placeholder warrant caution.
Ethics approval and parental informed consent are declared. The supplied text contains no author-level conflict-of-interest statement despite evaluating a named commercial device; unavailable supplementary files remain an assessability gap rather than a conduct concern.
Flags: 2 declared / 5 total
39 of 39 checkable references verified
42 references in manuscript 3 have no canonical index record — counted, but not index-checkable 1 reference confirmed by manual review
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No retraction or expression of concern found in Crossref (includes Retraction Watch).
Sources: Crossref (incl. Retraction Watch) ✓
Where this paper’s evidence sits on the path from initial observation to real-world use.
The device was tested in treated patients under a clinical protocol, placing the work beyond laboratory characterization. The small uncontrolled pilot does not yet provide deployment-ready comparative-effectiveness evidence.
“the study can be considered a pilot.”
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