Instant and Lasting Relief Effects of Strontium Chloride/Potassium Nitrate Dentifrice on Dentin Hypersensitivity: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Instant and Lasting Relief Effects of Strontium Chloride/Potassium Nitrate Dentifrice on Dentin Hypersensitivity (NCT01426360), a randomized na study. The primary outcome is Tactile Hypersensitivity Scores Immediately After Topical Dentifrice Use.

2. Clinical Question

The trial asked whether tactile hypersensitivity scores immediately after dentifrice use differed between a dentifrice containing strontium chloride and potassium nitrate and a control dentifrice. The registry describes the study as randomized, double-blind, and parallel-group.

3. Trial Design

The registry describes a randomized, double-blind, parallel-group clinical trial of two dentifrices for dentine hypersensitivity. One group received the dentifrice containing 2% strontium chloride and 5% potassium nitrate; the other received the control dentifrice. The control was described as having the same ingredients apart from those two substances. The trial status is completed.

Enrollment was 79. The posted primary outcome results include 38 participants in the strontium chloride/potassium nitrate group and 41 in the control group. These are the group sizes attached to this outcome, and the registry does not describe whether every enrolled participant contributed to every outcome. The allocation method is listed as randomized, but details about sequence generation, concealment, or stratification are not reported in the registry record.

Masking is listed as double. The record does not say which people were masked, how masking was maintained, or whether masking was assessed. Parallel-group means each group received its assigned dentifrice rather than being described as a crossover comparison; further details about treatment duration and follow-up are not reported in the registry record.

The study start and primary completion are both listed as 2011-09. The record lists no trial phase beyond NA. Its brief summary states that the objective was to compare instant and lasting relief, but the posted primary endpoint concerns tactile hypersensitivity scores immediately after use. The registry lists four outcome measures, while the displayed result analyzed is the primary endpoint. Further protocol details and the trial’s original design assumptions are not reported in the registry record.

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.

Overall Study

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 Tactile Hypersensitivity Scores Immediately After Topical Dentifrice Use, measured over immediately after dentifrice use.

The primary endpoint is the tactile hypersensitivity score measured immediately after dentifrice use. The unit is grams, and the registry reports the group results as means with standard deviations. The score is based on the force applied to exposed dentin before the participant indicates discomfort, subject to a maximum force of 50 grams. As described in the record, the force was applied with an electronic force-sensing probe and a #19 explorer tip. The probe began at 10 grams, and subsequent passes increased force in increments of 10 grams.

This measure provides a quantified way to assess the tactile response to a stimulus. A higher score means that a greater force was applied before discomfort was indicated, within the described measurement procedure. That makes the score a measure of response to this particular tactile test; it is not a direct measure of every aspect of dentine hypersensitivity or of lasting relief.

The immediate timing is important. Although the trial objective refers to both instant and lasting relief, the primary result is specifically measured immediately after use. Longer-term effects, changes over time, and patient-reported outcomes are not described by this endpoint. The registry does not report further validation details, the reliability of repeated measurements, or a clinically important threshold for interpreting score differences.

7. Results Posted in the Registry

• Strontium Chloride/Potassium Nitrate Dentifrice: mean 19.47 versus 14.27 on control; difference 5.20 (95% CI 0.21 to 10.19), standardized effect d = 0.47; z-test p = 0.041.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: it is a numerical score measured in grams. The registry reports the mean and standard deviation in each group, then reports an unadjusted mean difference. These statistics describe different features of the result. The mean gives the average score in a group, while the standard deviation describes how dispersed individual scores are around that average. The difference in means summarizes the contrast between the group averages.

What does the mean difference express?

The reported mean difference is 5.2 grams, comparing the strontium chloride/potassium nitrate group with the control. Its positive direction reflects a higher group mean in the intervention group. Since the endpoint records the force applied before discomfort is indicated, a higher score corresponds to a higher force in this particular test. This interpretation does not by itself establish the clinical importance of the score difference. The registry does not report a threshold for a clinically important difference.

An unadjusted comparison uses the reported group outcomes without accounting for additional variables in a statistical model. The registry provides no analysis entries and does not describe covariate adjustment. It is therefore appropriate to characterize the posted comparison as unadjusted, rather than infer that it controlled for baseline scores or other characteristics. Whether a particular analysis was prespecified is not reported in the registry record.

What does a confidence interval contribute?

A confidence interval gives a range of values compatible with the data under the method’s assumptions and communicates uncertainty about the estimated difference. The reported interval has a positive lower limit and an upper limit of 10.19 grams. Because the lower limit is above zero, the reported interval does not include a zero difference. The interval nevertheless spans multiple possible magnitudes, so the point estimate should not be read as the only plausible value. General explanation: a confidence interval is not a guarantee that the true value lies in its particular range, and it does not account for biases or analysis choices that are not reflected in the model.

How should the p-value be read?

The unadjusted p-value is 0.041. General explanation: a p-value measures how unusual results at least as incompatible with a specified null hypothesis would be if that null hypothesis and the statistical model were correct. It is not the probability that the null hypothesis is true, the probability that the findings are due to chance, or a measure of effect size. It should be read alongside the estimated difference and its confidence interval. The registry does not report whether the p-value was adjusted for multiple outcome measures or comparisons.

Why do the standard deviations matter?

The intervention group’s standard deviation is 14.69 grams and the control group’s is 5.76 grams. The groups therefore show different reported amounts of spread. General explanation: variation matters because the uncertainty around a group comparison depends not only on the difference between means but also on how variable individual observations are and how many observations contribute. When variability is large relative to the mean difference, estimates can be less precise. A mean and standard deviation do not reveal the full shape of the data, so they cannot show whether scores were symmetric, clustered, or affected by extreme values.

Over-dispersion is a general concern when observed variability is greater than a statistical model expects. If that occurs and is not accounted for, standard errors and confidence intervals can be misleading. The posted means and standard deviations alone do not establish whether over-dispersion was present or whether an analysis adjusted for it. The record does not report distributional checks, model diagnostics, or any alternative analysis.

What can be concluded from the analysis description?

The available results support a descriptive comparison of the two group means and the posted unadjusted inference. They do not show what model generated the inference, whether assumptions were assessed, or how missing observations were handled. The registry lists no analyses and does not include a detailed statistical plan. These omissions limit evaluation of the analysis process, even though the principal result and its uncertainty are reported.

The outcome is measured immediately after dentifrice use, so this analysis does not answer the full question of whether scores differ over time. Nor does a mean comparison describe individual responses or establish a lasting effect. General explanation: statistical significance and clinical relevance are separate ideas. The p-value addresses evidence against a specified null under assumptions, whereas practical importance requires context, including a meaningful threshold and the consequences of the measured difference. Such a threshold is not reported in the registry record.

10. Confidence Intervals and Precision

The estimated mean difference is 5.2 grams. Its reported confidence interval has a positive lower limit and an upper limit of 10.19 grams. The fact that the interval does not cross zero is consistent with the unadjusted p-value of 0.041, but the interval is more informative than a thresholded p-value alone because it displays a range of effect sizes compatible with the analysis.

The interval indicates uncertainty about the magnitude of the difference. It does not support treating 5.2 grams as an exact or universally applicable effect. The registry’s group means are 19.47 grams and 14.27 grams, and the reported standard deviations are 14.69 grams and 5.76 grams, respectively. The greater spread in the intervention group is relevant context for the variability of the observations. The posted summaries do not provide the individual scores or their distribution.

Confidence intervals are conditional on the method and assumptions used to calculate them. The registry does not report a statistical analysis plan, diagnostic checks, handling of missing observations, or adjustments for multiple outcomes. Accordingly, the interval describes uncertainty represented by the posted comparison, not every potential source of uncertainty or bias. The record also does not provide a clinically important difference threshold, so the interval cannot determine whether its possible values would be considered practically important.

The result applies to the immediate tactile score as described. Its precision does not extend to lasting relief, other outcome measures, or populations not characterized in the record. No secondary results are posted, and further information about outcome completion is not reported in the registry record.

11. 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, not total events. They are illustrations based on the observed effect, rather than the trial’s original sample-size plan. The registry’s planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set at the stated fraction of the observed effect.

For planning at 100% of the observed effect, the figures are 71 participants per arm for 80% power and 94 participants per arm for 90% power. At 75% of the observed effect, they are 125 participants per arm for 80% power and 168 participants per arm for 90% power. At 50% of the observed effect, they are 281 participants per arm for 80% power and 376 participants per arm for 90% power.

In plain terms, the 80% power column gives the planned per-arm sample size associated with an 80% chance of detecting the specified effect under the stated assumptions, if that effect is present and the assumptions hold. The 90% column uses a higher target chance of detecting it. Smaller effects require more participants to detect under the same assumptions, which is why the planning figures rise as the fraction of the observed effect falls. A curve representing these planning values illustrates that same relationship.

These are planning illustrations, not observed power. They use an effect estimated from this trial, so they should not be interpreted as evidence about the trial’s original design or as a guarantee of what a future study would achieve. The trial’s own design assumptions and sample-size justification are not reported in the registry record.

12. 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 = 5.200; pooled standard deviation σ = 10.997.
2. n = 2 × (1.96 + 0.842)² × 10.997² / 5.200² = 70.2, rounded up to 71 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 <- 5.2                      # observed difference in means
sigma <- 10.9967880198377                     # 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(1426360)
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 = 71 (80% power), 94 (90% power)
 75% of observed effect: n per arm = 125 (80% power), 168 (90% power)
 50% of observed effect: n per arm = 281 (80% power), 376 (90% power)
power.t.test: 71.2 
Simulated power at n = 71 per arm: 0.799 (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.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures, but the primary endpoint described in this analysis is the immediate tactile hypersensitivity score. No secondary results are posted. The record does not report how many comparisons were planned, whether outcomes had a prespecified hierarchy, or whether any adjustment was made for testing multiple outcomes. The unadjusted p-value of 0.041 should therefore be read as the reported result for this comparison, not as an explicitly multiplicity-adjusted finding.

General explanation: when multiple hypotheses are tested, the chance of obtaining at least one apparently unusual result can increase. Statistical approaches can address that issue, but the registry does not describe whether any such approach was planned or used. It would be inappropriate to infer either that adjustment was necessary or that it was performed.

The record lists no analysis entries. It does not report the statistical analysis plan, the analysis population, or whether the primary comparison followed an intention-to-treat, per-protocol, or other approach. The group counts attached to the primary outcome are 38 and 41, but the registry does not explain how participants with missing measurements were handled or whether any enrolled participants were excluded from this outcome analysis.

Missing-data methods can affect both estimates and uncertainty, particularly if the probability of missingness is related to outcomes or group assignment. General explanation: complete-case analysis, imputation, and other methods rely on different assumptions. The registry does not report which, if any, was used. It also does not describe protocol deviations, withdrawals, or outcome completion by group. Consequently, the posted result can be interpreted as the reported comparison, while its sensitivity to missing observations and analysis-population choices cannot be assessed from the registry record.

The summary refers to instant and lasting relief, but the primary endpoint is immediate and the record posts no secondary results. The relationship between the full set of outcomes and the reported analysis is not reported in the registry record.

14. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 1% reporting threshold.

The registry reports zero serious adverse events among 38 participants at risk in the strontium chloride/potassium nitrate group and zero among 41 participants at risk in the control group. It also reports zero other adverse events among the participants at risk in each group. These are the posted counts for the trial record.

These figures describe what was recorded, not proof that no adverse events occurred outside the registry’s reporting categories or observation period. The record does not report the duration of safety monitoring, how events were solicited or classified, or the criteria used to judge seriousness or attribution. The death fields are not reported in the registry record; no conclusion about deaths should be drawn from a blank value.

Zero reported events in the registry does not establish that an intervention has no risk. It also does not establish equivalence between the dentifrices for safety. The posted safety counts should be interpreted in the context of this trial’s reported group sizes and the missing details about monitoring and event ascertainment.

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

The posted primary result shows a higher mean immediate tactile hypersensitivity score in the strontium chloride/potassium nitrate group than in the control group: 19.47 grams compared with 14.27 grams. The reported unadjusted mean difference is 5.2 grams, and the confidence interval has a positive lower limit and extends to 10.19 grams. The score reflects the force applied before discomfort was indicated in the specified probe procedure.

This describes a group-average difference on one immediate measurement. It does not show that every participant experienced a higher score, identify how many people improved, or establish the importance of the difference to participants. The registry does not report a threshold for a clinically important change or details of the score distribution. The standard deviations show that individual scores varied within both groups, particularly in the intervention group.

The result does not establish lasting relief. Although the stated objective refers to instant and lasting relief, the primary endpoint is assessed immediately after dentifrice use, and no secondary results are posted in the registry record. It also does not answer whether the result persists, whether it generalizes to other measurements, or what happens with different patterns of use.

The unadjusted p-value is 0.041, but this should not be read as the probability that the finding is due to chance or as a measure of clinical benefit. The record does not report a full statistical plan, missing-data methods, analysis populations, or multiplicity procedures. These omissions limit how fully the result can be evaluated. The posted data support describing the observed immediate comparison and its reported uncertainty, without extending that interpretation to unreported outcomes or making a treatment recommendation.

16. Why This Trial Matters Statistically

This trial illustrates why a numerical treatment comparison needs to be read together with the measurement that generated it. The primary endpoint is not a broad symptom scale in the record; it is force, measured in grams, at the point a participant indicates discomfort during a standardized tactile test. Understanding the endpoint clarifies what a higher mean represents and what the score does not capture.

It also demonstrates the value of reporting both group means and their variability. The means differ by the reported 5.2 grams, while the group standard deviations differ notably in size. A point estimate alone can obscure how much individual scores vary. The confidence interval adds information about uncertainty around the comparison, while the p-value alone cannot communicate the range of plausible effect magnitudes.

Another statistical issue is the gap between the trial objective and the posted primary result. The objective mentions instant and lasting relief, but the primary endpoint is immediate, and secondary results are not posted. This distinction matters because outcome timing defines the question an analysis answers. Evidence about an immediate response does not automatically answer a question about persistence.

Finally, planning calculations based on the observed effect show how required sample sizes change when the target effect is smaller. Such illustrations can help readers understand the relationship between effect size and study size, but they cannot reconstruct the original design rationale, which is not reported in the registry record. Overall, the trial is a useful example of interpreting an unadjusted continuous-outcome comparison while keeping measurement, precision, multiplicity, and reporting limitations in view.

17. 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.

The registry record leaves important design and analysis details unspecified. It identifies the study as randomized and double-blind, but does not report the randomization sequence method, allocation concealment, who was masked, or how masking was maintained. It also does not provide detailed participant eligibility criteria or baseline characteristics, limiting assessment of how the outcome groups compare before treatment.

The primary outcome is an immediate tactile score. The record does not report measurement reliability, repeat testing, or a clinically important threshold. Although the stated objective includes lasting relief, no secondary results are posted, so the immediate result cannot address longer-term outcomes. The record lists four outcome measures but does not provide their full relationship to the primary result or explain whether there were additional planned comparisons.

The posted result includes group means, standard deviations, a confidence interval, and an unadjusted p-value, but the registry lists no analysis entries. The method used to calculate the inference, model checks, handling of missing data, and analysis population are not reported in the registry record. The record also does not state whether the statistical analysis was prespecified or adjusted for multiple comparisons.

Safety reporting is limited to the posted event counts. Monitoring duration and event ascertainment methods are not reported, and deaths are not reported in the registry record. Finally, the trial’s original sample-size assumptions and justification are not reported. The planning illustrations based on the observed effect should not be mistaken for the original design plan.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Instant and Lasting Relief Effects of Strontium Chloride/Potassium Nitrate Dentifrice on Dentin Hypersensitivity — NCT01426360.
• Registry record last updated 2011-12-19; status last verified 2011-11.
• Results first posted 2011-12-19.
• 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.

21. Record Summary

The completed study is listed as a randomized, double-blind, parallel-group clinical trial of dentifrices for dentine hypersensitivity. Enrollment was 79, and the record lists Sun Yat-sen University as sponsor. The study start and primary completion are both recorded as 2011-09.

The primary endpoint is tactile hypersensitivity score in grams, measured immediately after dentifrice use. The mean was 19.47 grams in the strontium chloride/potassium nitrate group and 14.27 grams in the control group. The reported unadjusted mean difference is 5.2 grams, with a confidence interval whose lower limit is positive and upper limit is 10.19 grams; the unadjusted p-value is 0.041.

The registry lists four outcome measures but posts no secondary results and no analysis entries. It reports zero serious and zero other adverse events in both groups. Further statistical-plan, missing-data, and safety-monitoring details are not reported in the registry record.