Evaluation of the Effect of Three Types of Rapid Maxillary Expanders (Conventional, Hybrid and MSE): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of the Effect of Three Types of Rapid Maxillary Expanders (Conventional, Hybrid and MSE) (NCT05446714), a randomized na study. The primary outcome is Molar Distance:.

2. Clinical Question

3. Trial Design

The registry describes a randomized, parallel-group clinical trial with quadruple masking. It lists the phase as NA and the planned enrollment as 54. The three groups are Conventional Hyrax, Hybrid Hyrax, and Maxillary Skeletal Expander. Arm-level primary outcome summaries are listed for 15 participants in the Conventional Hyrax group, 15 in the Hybrid Hyrax group, and 16 in the Maxillary Skeletal Expander group. These posted outcome counts should not be treated as a complete account of participant flow: the numbers screened, randomized, treated, and included in each analysis, along with reasons for any exclusions, are not reported in the registry record.

The study aim is to compare radiographic morphometric changes in the nasal airway after use of the three rapid maxillary expansion approaches, using CBCT. The registry also lists molar inclination, maxillary width, and the temporomandibular joint as secondary outcomes. The primary endpoint is molar distance at 6 months. Details of the allocation sequence, concealment, implementation of masking, and any procedures used to protect masking are not reported in the registry record. The registry status is active, not recruiting. The recorded study start is 2022-04-30 and the primary completion date is 2023-11-19.

Although randomized parallel allocation and quadruple masking are identified in the record, those labels alone do not establish how the procedures were carried out or whether masking was maintained. No trial protocol, original statistical analysis plan, or participant-flow description is reported in the registry record. Accordingly, the available statistical reading is limited to the posted group summaries and the comparisons calculated from those summaries; it cannot establish whether those calculations match a prespecified analysis plan.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: * Patients suffering maxillary collapse with a skeletal background * Patients with unilateral or bilateral posterior crossbite. * Patients with reduced or average anterior face height. * Patients with no periodontal disease. * Patients with good oral hygiene and general health.6- No systemic diseases that may affect bone quality or interfere with orthodontic treatment. * Patients with erupted maxillary permanent first molars and premolars.

Overall Study

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Molar Distance:, measured over 6 months.

The primary endpoint is molar distance, measured in mm at 6 months. It is defined as the distance from the mesiolingual cusp of the upper first molar on one side to the mesiolingual cusp of the upper first molar on the other side, using CBCT measurement software. The registry describes the endpoint as a mean with standard deviation. The groups' reported means are 43.55 for Conventional Hyrax, 44.79 for Hybrid Hyrax, and 42.14 for Maxillary Skeletal Expander.

This measurement is used as a radiographic indicator of transverse change associated with maxillary expansion. Because it measures the distance between dental landmarks, it is not itself a direct measure of nasal airway function, breathing symptoms, or patient experience. The study's stated aim also refers to airway morphometric changes, but the primary endpoint listed in the record is molar distance. The relationship between this primary measure and any airway-specific measurement is not described in the registry record.

A mean conveys the group's central value, while the standard deviation describes the spread of individual measurements around that mean. Those summaries provide a basis for comparing the groups, but do not show the full distribution of measurements or individual changes from baseline. Baseline endpoint values, the timing of any baseline CBCT, and whether the primary analysis uses change from baseline or the 6-month measurements alone are not reported in the registry record. These details matter when interpreting what the between-group mean differences represent.

7. Results Posted in the Registry

• Hybrid Hyrax: mean 44.79 versus 43.55 on control; difference 1.24 (95% CI -1.14 to 3.62), standardized effect d = 0.37; z-test p = 0.307.
• Maxillary Skeletal Expander: mean 42.14 versus 43.55 on control; difference -1.41 (95% CI -3.29 to 0.47), standardized effect d = -0.52; z-test p = 0.141.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Molar Inclination

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Hybrid Hyrax: mean 4.85 versus 5.66 on control; difference -0.81 (95% CI -2.12 to 0.50), standardized effect d = -0.44; z-test p = 0.226.
  • Maxillary Skeletal Expander: mean 2.08 versus 5.66 on control; difference -3.58 (95% CI -4.58 to -2.58), standardized effect d = -2.54; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Hybrid Hyrax and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Maxillary Skeletal Expander than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary outcomes provide related anatomical context but do not directly answer the primary molar-distance question. Molar inclination, maxillary width, and temporomandibular joint measures are listed as secondary outcomes. Numerical arm summaries are available for molar inclination; numerical results for maxillary width and the temporomandibular joint are not reported in the registry record. The available evidence across the full set of named secondary outcomes is therefore incomplete.

In the molar-inclination summaries, the comparison with Conventional Hyrax is less clearly separated for Hybrid Hyrax than for Maxillary Skeletal Expander. This pattern differs from the primary molar-distance comparisons, where both comparisons have intervals that include zero. That contrast illustrates why outcomes should be interpreted individually: measures of molar distance and inclination capture different features, and a pattern in one does not establish the same pattern in another. The registry record does not report a prespecified relationship among these measures or a single combined outcome.

Secondary findings generally carry less weight than the primary endpoint when they were not the main basis for the trial question, especially when the record does not report a hierarchy, adjustment plan, or prespecified analysis for multiple outcomes. Repeated testing can make some results appear notable by chance. The molar-inclination estimates are unadjusted, and the registry record does not report whether multiplicity was addressed. They should therefore be treated as exploratory context rather than as definitive confirmation of the primary result.

For secondary interpretation, the important point is not to select a single striking estimate in isolation. The measurement definitions, missing results, analysis procedures, and multiplicity plan all affect how much weight any secondary pattern can bear. In particular, no conclusion about maxillary width or temporomandibular joint outcomes can be drawn from their names alone. Their numerical results and detailed definitions are not reported in the registry record.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Molar Inclination
• Maxillary Width
• Temporomandibular Joint

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: it is a distance measured in mm. For a continuous outcome, a group mean summarizes the central location of measurements, while the standard deviation describes how dispersed those measurements are around the mean. The registry reports both for each arm. These summaries are useful for an initial comparison, but do not show the shape of the data, possible outliers, or how much each participant changed from baseline.

What does a mean difference represent?

A mean difference subtracts the reference group's mean from the comparison group's mean. Here, Conventional Hyrax is the reference. A positive estimate means the comparison group's posted mean is higher; a negative estimate means it is lower. For the primary outcome, the Hybrid Hyrax estimate is 1.24 mm, while the Maxillary Skeletal Expander estimate is -1.41 mm. The signs describe the direction relative to the Conventional Hyrax mean. They do not, by themselves, indicate clinical importance or establish a causal effect.

The comparisons are recalculated, unadjusted comparisons based on the arm-level summaries. An unadjusted comparison does not account for covariates or any multiplicity adjustment. The registry record does not report the original statistical model, any covariate adjustment, or a sponsor-reported analysis of these primary comparisons. Thus, these estimates provide a transparent comparison of the posted means, but cannot confirm what analysis the trial intended to use.

How should the confidence intervals be read?

A confidence interval describes the range of estimates compatible with the data under the calculation's assumptions. A narrow interval indicates greater precision; a wide interval indicates that the estimate remains uncertain over a broader range. For a mean difference, an interval spanning zero includes the possibility that the groups have the same mean, as well as possible differences in either direction. Both posted primary intervals include zero. This does not prove equality; it means the data do not narrowly locate the difference on one side of zero.

The interval and the p-value answer related but not identical questions. A p-value measures how unusual the observed data, or more extreme data, would be under a null model of no difference, given the calculation's assumptions. It does not give the probability that the null hypothesis is true, and it does not quantify the size or importance of the difference. The posted primary p-values are unadjusted. The registry record does not report whether a different significance threshold or multiplicity adjustment was prespecified.

What can be learned from the standard deviations?

The arm-level standard deviations indicate that individual measurements vary within each group. When measurements are variable relative to the difference in group means, the group contrast is estimated less precisely. The posted comparisons use pooled standard deviations as part of their recalculation. Pooling represents a common estimate of within-group variability for the two groups in a contrast. It is a calculation choice, not evidence that the actual variability is identical across groups. Whether the assumptions behind this approach were checked is not reported in the registry record.

Over-dispersion is a general concern when variability is greater than the statistical model anticipates. If the model understates variability, standard errors may be too small and intervals may be too narrow; if it overstates variability, estimates may be less precise than necessary. The available summaries do not permit a detailed assessment of distributional shape, outliers, or whether the assumptions behind the recalculations are suitable. A plot or participant-level analysis could provide additional information, but such information is not reported in the registry record.

What is the distinction between the primary and secondary outcomes?

The primary endpoint is molar distance at 6 months. The record also identifies molar inclination, maxillary width, and temporomandibular joint outcomes as secondary. Secondary outcomes can add context about related anatomical measurements, but they do not replace the primary endpoint. When several outcomes or comparisons are examined, the chance of finding at least one apparently unusual result can increase. Without a reported plan for prioritizing or adjusting secondary analyses, isolated secondary p-values deserve more cautious interpretation.

The secondary summaries identify molar inclination as a continuous measure at 6 months. Numerical arm summaries are available for that outcome, while numerical results for maxillary width and temporomandibular joint outcomes are not reported in the registry record. The exact operational definitions and analysis procedures for these secondary outcomes are also not reported. Their names alone do not establish how they were measured or whether higher values represent a favorable or unfavorable change.

What do the planning illustrations mean?

The sample-size illustrations use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. They consider effects at 100%, 75%, and 50% of the observed effect. Smaller target effects require more participants for the same stated power under those assumptions. These are planning illustrations based on observed effects, not the trial's original design calculation. The original sample-size justification, chosen target effect, and assumptions are not reported in the registry record.

Power is the probability that a planned statistical procedure will detect an effect of a specified size under its assumptions. The 80% and 90% columns describe planning targets for detecting the stated effect size; they are not evidence about the probability that the current trial found a true effect. The registry record reports no interim analyses, no formal analysis plan, and no participant-level data. Such details cannot be inferred from the arm summaries or the planning calculations.

11. Confidence Intervals and Precision

Precision concerns how tightly the available data locate a between-group estimate. For the primary Hybrid Hyrax comparison, the mean difference is 1.24 mm, and the 95% confidence interval runs from -1.14 to 3.62. This interval spans zero, values favoring a lower mean in the Hybrid Hyrax group, and values favoring a higher mean. The estimate's positive direction is therefore not firmly established by the interval.

For Maxillary Skeletal Expander compared with Conventional Hyrax, the estimated mean difference is -1.41 mm. Its 95% confidence interval extends from -3.289 to above zero, and therefore also includes the possibility of no mean difference and differences in either direction. The unadjusted p-value is 0.141. Together, the point estimate, interval, and p-value describe an uncertain contrast rather than a precise estimate of a single direction or magnitude.

The intervals are important because a point estimate alone can appear more conclusive than the data support. The observed arm counts for the primary outcome are 15, 15, and 16. The standard deviations also indicate variation among individual measurements. Both the amount of within-group variation and the number of observations influence the precision of a mean difference. The registry record does not provide participant-level measurements, baseline-adjusted estimates, or information about missing outcomes that would permit a more complete precision assessment.

Statistical compatibility with zero should not be mistaken for proof that the groups are equivalent. Equivalence or non-inferiority requires a specified margin and an appropriate analysis; such a margin and analysis are not reported in the registry record. Nor does an interval alone identify what difference would matter clinically: a threshold for a meaningful molar-distance change is not reported in the registry record. The intervals therefore describe statistical uncertainty, while clinical importance remains unresolved.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm for 80% power and participants per arm for 90% power. These comparisons are not event counts: the outcome is continuous, so the displayed quantities refer to people in each of the two arms being compared. They are not total sample sizes across the arms. The separate instruction about total events applies to time-to-event planning calculations, which are not the calculations described for these continuous outcomes.

The illustrations assume a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each calculation uses a target effect equal to 100%, 75%, or 50% of the observed effect for the relevant comparison. For example, the row planning for 75% of the observed effect asks how many participants per arm would be needed to detect a smaller target than the full observed effect under the stated assumptions. Smaller effects need more participants to achieve the same power target.

The 80% power column gives the per-arm planning count for a procedure intended to have an 80% chance of detecting the chosen target effect if that effect is real and the assumptions hold. The 90% column uses a higher detection probability target and consequently can require more participants. These figures are planning illustrations based on the observed effect, not the trial's original design calculation. The trial's own sample-size justification and design assumptions are not reported in the registry record. This is not observed power.

The displayed figures are sensitive to the observed effect: a large observed contrast can produce a smaller illustrative count, while a more modest target effect requires more participants. They should not be read as evidence that the current trial had adequate power, nor as a retrospective verdict on the result. The estimates come from small observed groups and may not represent a stable effect size for planning another study. The illustrations also do not account for any assumptions beyond those stated in the registry record.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 1.240; pooled standard deviation σ = 3.325.
2. n = 2 × (1.96 + 0.842)² × 3.325² / 1.240² = 112.9, rounded up to 113 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 1.24                      # observed difference in means
sigma <- 3.32519172379579                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(5446714)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 113 (80% power), 152 (90% power)
 75% of observed effect: n per arm = 201 (80% power), 269 (90% power)
 50% of observed effect: n per arm = 452 (80% power), 605 (90% power)
power.t.test: 113.9 
Simulated power at n = 113 per arm: 0.793 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome and multiple secondary outcomes, and the posted results include more than one comparison against Conventional Hyrax. Testing several outcomes or contrasts increases the chance that at least one result will appear statistically unusual even when there is no real difference. Methods for controlling this multiplicity—such as designating a hierarchy of tests or adjusting the inferential threshold—are not reported in the registry record. The posted p-values are unadjusted, so they should not be treated as if they account for all outcomes and comparisons.

The record also does not report a complete statistical analysis plan. In particular, it does not describe a prespecified model, covariate adjustment, missing-data procedure, or whether the primary analysis was intended to follow randomized assignment. Whether the analyses used all randomized participants, only participants with observed measurements, or another analysis population is not reported in the registry record. The population field for the primary measure is blank, and eligibility criteria are not described in detail.

Missing data can affect a comparison if outcome availability differs across groups or is related to participants' measurements. Without the number of participants with a measured endpoint in each arm at the relevant time, reasons for missing measurements, and the handling method, the direction or size of any such effect cannot be assessed. The posted arm counts describe the summaries, but they do not establish why those counts differ from planned enrollment or whether any observations were excluded.

These omissions do not demonstrate that the trial failed to address multiplicity or missing data in its conduct. They mean only that those procedures are not reported in the registry record. The recalculated comparisons are therefore best treated as unadjusted summaries with uncertainty, rather than as a complete reconstruction of the trial's intended inferential framework.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: metabolism (5.6%).

The adverse-event record lists 18 participants at risk in each group for serious adverse events and for other adverse events. It lists 1 participant affected by a serious adverse event in each group. For other adverse events, the recorded affected counts are 1 in Conventional Hyrax, 1 in Hybrid Hyrax, and 2 in Maxillary Skeletal Expander. The serious-event term listed most often is “metabolism,” at 5.6%.

The record also lists death counts of 15, 15, and 16 for Conventional Hyrax, Hybrid Hyrax, and Maxillary Skeletal Expander, respectively. The meaning and basis of these entries are not explained in the registry record, so they should not be interpreted as a verified account of deaths or reconciled with other counts. The adverse-event groups list 18 at risk per arm, while primary outcome summaries list 15, 15, and 16 participants; the reason for this difference is not reported in the registry record.

These entries are counts, not a complete safety analysis. Definitions, event timing, severity grading, relatedness assessments, and statistical comparisons are not reported in the registry record. The figures should be read as recorded adverse-event information, without inferring comparative safety or attributing events to a device.

16. What the Result Does, and Does Not, Mean

The posted primary endpoint results describe differences in mean molar distance at 6 months among three rapid maxillary expander groups. Relative to Conventional Hyrax, the Hybrid Hyrax estimate is 1.24 mm higher, while the Maxillary Skeletal Expander estimate is 1.41 mm lower. Both confidence intervals include zero, and both unadjusted p-values are above 0.05. The data therefore leave uncertainty about whether either comparison represents a true difference in the population, as well as about the size and direction of any difference.

This does not establish that the devices are equivalent. Equivalence requires a defined margin and an analysis designed to assess whether differences are sufficiently small; neither is reported in the registry record. Conversely, the estimates do not establish a reliable difference simply because their point estimates are not zero. The intervals are broad enough to include both directions for the primary comparisons.

The measured endpoint is a radiographic distance between molar landmarks. It does not directly measure nasal airflow, obstruction symptoms, quality of life, or patient preference. Although the study aim includes nasal airway morphometric changes, the primary endpoint listed is molar distance. Conclusions about airway function or symptoms cannot be drawn from this primary measure alone. The registry's listed secondary outcomes may add anatomical information, but detailed numerical results for maxillary width and temporomandibular joint outcomes are not reported in the registry record.

The posted figures also do not establish how the results would apply to every adolescent or clinical setting. Eligibility criteria, baseline characteristics, implementation details, and the handling of missing data are not reported in the registry record. The study is recorded as randomized, but its allocation and masking procedures are not described in enough detail to assess their implementation from the registry record alone. These results should therefore be read as a limited comparison of the available radiographic summaries, not as a comprehensive evaluation of clinical benefit or harm.

17. Why This Trial Matters Statistically

This trial raises a statistical question that arises in device comparisons: how much information can be obtained from several arms when the main outcomes are continuous anatomical measurements? A randomized parallel design can support between-group comparisons, while the mean differences and confidence intervals describe both the estimated direction and the uncertainty. In this record, the primary comparisons have point estimates on opposite sides of the Conventional Hyrax mean, but the intervals include zero. That combination makes the uncertainty itself central to interpretation.

The record also illustrates why a result should not be reduced to a p-value. The interval communicates a range of compatible differences, while the p-value summarizes evidence against a null model under the calculation's assumptions. Neither establishes clinical importance, equivalence, or a direct airway benefit. A clear interpretation depends on matching the statistical endpoint to the clinical question and distinguishing an anatomical surrogate measurement from patient-facing outcomes.

Finally, the trial highlights the importance of a reported analysis plan. The registry identifies multiple outcomes and comparisons, but does not report multiplicity procedures, missing-data methods, or the original sample-size justification. Those details help readers understand which results were prioritized, how uncertainty was handled, and whether the observed analyses were planned. Their absence does not invalidate the posted summaries, but it limits the strength and scope of conclusions that can be drawn from them.

18. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Important limitations specific to interpretation of this trial arise from the information recorded about its outcomes and analyses. The primary endpoint is a single radiographic distance measured at 6 months, while the stated study aim concerns nasal airway morphometric changes. The registry record does not report how this dental landmark measure relates to a specific airway measure, nor does it list direct airflow or symptom outcomes among the detailed numerical results. This limits conclusions about the broader airway question.

The primary outcome summaries are based on 15, 15, and 16 participants across the three groups, compared with planned enrollment of 54. Participant flow and reasons for the difference between planned enrollment and outcome counts are not reported in the registry record. Baseline values, missing measurements, and the analysis population are also not described. Without that information, it is not possible to determine whether the posted groups remained comparable on the endpoint or how missing data may affect the estimates.

The record does not report a full statistical analysis plan, adjustment for multiple outcomes, a clinically meaningful difference threshold, or the trial's original sample-size justification. The unadjusted recalculated contrasts and the planning illustrations cannot fill those gaps. The secondary outcome list includes maxillary width and temporomandibular joint measures, but numerical results for them are not reported in the registry record. The safety entries also include death counts whose meaning is not explained. These limitations constrain how broadly the posted statistical evidence can be interpreted.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Evaluation of the Effect of Three Types of Rapid Maxillary Expanders (Conventional, Hybrid and MSE) — NCT05446714.
• Registry record last updated 2025-04-25; status last verified 2025-04.
• Results first posted 2025-04-25.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

22. Record Summary

NCT05446714 is a randomized, parallel-group trial comparing Conventional Hyrax, Hybrid Hyrax, and Maxillary Skeletal Expander approaches. The registry lists quadruple masking, planned enrollment of 54, and an adolescent CBCT study of maxillary expansion. The primary outcome is mean molar distance in mm at 6 months.

Compared with Conventional Hyrax, the posted mean differences are 1.24 mm for Hybrid Hyrax and -1.41 mm for Maxillary Skeletal Expander. Both primary confidence intervals include zero, and the unadjusted p-values are 0.307 and 0.141. The estimates are uncertain and do not establish equivalence or a clear difference. The registry also lists molar inclination, maxillary width, and temporomandibular joint outcomes; detailed numerical results are not reported for all of these outcomes.

The registry status is active, not recruiting. The original analysis plan, missing-data methods, multiplicity approach, and original sample-size justification are not reported in the registry record.