Clinical Study Comparing Dental Plaque and Gingivitis Reduction After Using One of Three Oral Hygiene Multi-component Regimens (Using of a Manual Toothbrush, a Toothpaste and a Mouthwash): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical Study Comparing Dental Plaque and Gingivitis Reduction After Using One of Three Oral Hygiene Multi-component Regimens (Using of a Manual Toothbrush, a Toothpaste and a Mouthwash) (NCT02366689), a randomized phase 4 study. The primary outcome is Dental Plaque Scores.

2. Clinical Question

The clinical question is therefore broader than the specific numerical comparison that can be interpreted from the listed primary measure. The record identifies dental plaque and gingivitis as the conditions of interest and gives a longitudinal objective, but its primary outcome entry is explicitly timed at baseline. Baseline scores describe the condition before the assigned regimen could produce a follow-up change. They can characterize starting values and possible differences between randomized groups, but they are not themselves measures of reduction.

The listed comparisons contrast mean baseline plaque scores for the toothpaste regimen against each of the two toothpaste-and-mouthwash regimens. They do not report a change from baseline, a later score, or a contrast in change between regimens. Thus the posted values support a description of baseline group scores and the registry's reported overall analysis, not a conclusion about comparative plaque reduction during use. Follow-up endpoint results and the details needed to interpret the broader gingivitis question are not reported in the registry record.

3. Trial Design

The record identifies NCT02366689 as a completed Phase 4 study sponsored by Colgate Palmolive. It began in 2014-06, with primary completion in 2014-12. The listed enrollment is 179. The trial is described as randomized, triple-masked and parallel-group, with three oral-hygiene regimens.

One group used a manual toothbrush and triclosan/fluoride toothpaste. A second used a manual toothbrush, stannous fluoride toothpaste and cetylpyridinium chloride mouthwash. The third used a manual toothbrush, fluoride-only toothpaste and fluoride-only mouthwash. The registry record does not report further details about the randomization process, the specific parties masked, or how masking was maintained.

The posted baseline plaque summaries list 60 participants in the toothpaste group, 58 in the toothpaste-plus-mouthwash group and 61 in the fluoride-only toothpaste-plus-mouthwash group. These are the group counts attached to the listed baseline measure; they should not be assumed to describe every analysis population or every follow-up. The registry record does not report the analysis-population definitions or the amount of follow-up data available for each outcome.

The study objective refers to evaluating plaque and gingivitis over three and six months of assigned product use. The primary outcome entry is instead a baseline dental plaque score. Although the record lists six outcome measures and six analyses, it does not provide secondary results in the posted information. The registry record does not report the trial's original sample-size justification, detailed analysis plan, follow-up results, or the handling of participants with missing outcome data. Consequently, design features can be described, but the evidence available for interpreting treatment-period effects is limited.

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: No washout or pre-assignment phase

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 Dental Plaque Scores, measured over Baseline.

The listed primary endpoint is a mean dental plaque score at baseline, measured with the Quigley-Hein Index as modified by Turesky. The scale runs from 0 to 5. A score of 0 means no plaque; increasing values describe progressively more plaque on the tooth surface, with 5 indicating plaque covering two-thirds or more of the crown.

This index turns an observed plaque distribution into a continuous numerical measure. Reporting a group mean gives a concise description of the average score, while the standard deviation describes how spread out individual scores are around that average. These summaries help characterize the groups and form the basis of the posted mean comparisons.

Plaque scoring is relevant to the study objective because the objective concerns reducing established plaque. Timing is crucial, however: the listed primary measure is explicitly at baseline. A baseline score records starting status; it does not measure a reduction after product use. Assessing reduction would require a follow-up score or a defined change-from-baseline outcome, together with an analysis comparing regimens over time. Such primary follow-up results are not reported in the registry record. The posted baseline endpoint therefore describes initial plaque levels and cannot, by itself, establish how the regimens affected plaque or gingivitis during the study.

7. Results Posted in the Registry

• Toothpaste + Mouthwash: mean 3.22 versus 3.33 on control; difference -0.11 (95% CI -0.21 to -0.01), standardized effect d = -0.40; z-test p = 0.030.
• Fluoride Only Toothpaste + Mouthwash: mean 3.34 versus 3.33 on control; difference 0.01 (95% CI -0.09 to 0.11), standardized effect d = 0.04; z-test p = 0.839.

8. Statistical Interpretation

9. Statistical Methods Explained

The outcome is continuous: it is a numerical score on a bounded plaque index rather than a count of events or a time until an event. The record summarizes each group with a mean and standard deviation. A mean describes the group's average score; the standard deviation describes variation among scores within the group. These answer different questions and should not be read as interchangeable measures of uncertainty.

What does a mean difference describe?

A mean difference subtracts one group's mean from another group's mean. The posted pairwise contrasts use the toothpaste group as the reference. A negative estimate indicates a lower listed mean in the named comparison group; a positive estimate indicates a higher listed mean. The estimate of -0.11 for toothpaste plus mouthwash and the estimate of 0.01 for fluoride-only toothpaste plus mouthwash refer to baseline plaque scores. Their signs and sizes describe those baseline contrasts only.

A mean difference is expressed in the original score units, which makes its scale directly interpretable against the 0-to-5 index. It does not tell whether a difference matters clinically. That judgment requires relevant clinical context, which the registry record does not report. Nor does the baseline mean difference represent a treatment effect: a treatment effect would require a suitable outcome measured after assignment, such as follow-up scores or a prespecified change analysis.

What does a confidence interval add?

A confidence interval expresses uncertainty around an estimate under the assumptions of the method used to construct it. It gives a range of values compatible with the observed data and analysis procedure; it is not a guarantee that the true value lies within that particular interval. For the first recalculated contrast, the interval excludes zero. For the second, it includes zero. These features help describe the precision of the pairwise estimates, but they do not turn baseline contrasts into evidence about later change.

When an interval includes zero, the data do not clearly distinguish a positive from a negative difference at the corresponding confidence level. This does not prove that the groups are identical. When an interval excludes zero, the estimate is statistically distinguishable from zero under the method's assumptions, but that alone does not establish importance or causality. Interpretation also depends on timing, outcome definition, analysis choices and the extent of missing information.

How should p-values be read?

The unadjusted p-values attached to the recalculated pairwise contrasts are 0.03 and 0.839. A p-value describes how unusual the observed result, or a more extreme result, would be under a specified null hypothesis and model assumptions. It is not the probability that the null hypothesis is true, and it does not measure the probability that a regimen works. The word “unadjusted” matters: the record does not report a multiplicity adjustment for these recalculations.

The sponsor's reported ANOVA p-value is 0.04. ANOVA is a method for testing whether there is evidence of differences among group means in an overall comparison. It does not, by itself, identify which groups differ or quantify a particular pairwise contrast. The registry record does not provide enough detail to reconstruct the sponsor's ANOVA or determine how it relates to every other analysis. The sponsor's own analysis takes precedence over the simple recalculations when the results differ.

Why does over-dispersion matter?

Over-dispersion is a general concern when data vary more than a statistical model assumes. It is especially relevant to counts or event data, where a model that expects limited variability can understate uncertainty if observations are more variable than expected. This endpoint is a continuous plaque score summarized by a mean and standard deviation, not a count outcome. The registry record does not report an over-dispersion assessment or a model for repeated follow-up scores. General consideration of over-dispersion does not resolve the more basic limitation that the posted primary score is at baseline.

What can be inferred from the listed design?

Randomized allocation is intended to reduce systematic differences between groups at entry, while masking can reduce some forms of bias during conduct or assessment. The record labels the study randomized and triple-masked, but does not report the allocation procedure or identify the masked parties. A parallel design assigns participants to a regimen and compares groups rather than having each participant receive every regimen. These design labels describe intended features; they do not replace information about the actual analysis population, adherence, missing data, or follow-up outcomes.

The posted recalculations are simple, unadjusted comparisons derived from the displayed summary statistics. They do not incorporate covariates, repeated observations, or any adjustment that may have been used in the sponsor's analysis. The record does not report enough detail to assess such adjustments or to verify the precise analysis populations. Accordingly, the recalculations are a transparent way to describe the posted baseline summaries, not a substitute for the sponsor's complete statistical analysis.

10. Confidence Intervals and Precision

The baseline group means are reported to two decimal places, and their standard deviations are also reported to two decimal places. The mean differences are -0.11 for toothpaste plus mouthwash versus toothpaste, and 0.01 for fluoride-only toothpaste plus mouthwash versus toothpaste. These estimates are small on the 0-to-5 plaque scale, but their clinical importance cannot be determined from the registry information alone.

The confidence interval for the first recalculated difference excludes zero. This indicates that, under the unadjusted comparison's assumptions, the estimated baseline difference is not centered on a range that includes no difference. The interval for the second contrast includes zero, so the posted data do not clearly distinguish that baseline contrast from zero. Neither interval describes a treatment-period effect, because both comparisons are based on the listed baseline measure.

Precision depends on the amount of variation in scores and the number of observations contributing to an estimate. The group standard deviations are similar in the posted summaries, while the listed group counts are 60, 58 and 61. The registry record does not report whether all enrolled participants contributed to each analysis or whether any outcome data were missing. The reported intervals therefore cannot, on their own, show how missingness or analysis-population choices may have affected precision.

Statistical precision is not the same as clinical importance. A narrow interval can still surround a difference too small to matter, while a wider interval may leave meaningful possibilities unresolved. For these baseline results, the central interpretive issue is timing: even precise estimates of starting scores do not establish differences in change after assigned use. Follow-up estimates and their uncertainty are 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 sample-size figures are planning illustrations based on the observed pairwise effects, not the trial's original design calculation. Because these are continuous-outcome comparisons rather than time-to-event outcomes, the figures are participants per arm, not total event counts. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The calculation considers detecting 100%, 75% or 50% of the observed effect.

The 80% power column gives the number of participants per arm that the planning calculation indicates would be needed for an 80% chance of detecting the chosen effect under those assumptions, if that effect were real. The 90% power column gives the corresponding per-arm planning number for a 90% chance. These are design probabilities under a specified model and effect, not probabilities that a result is true. This is not observed power.

For the baseline comparison of toothpaste plus mouthwash with toothpaste, planning for 100% of the observed effect gives 99 participants per arm for 80% power and 132 per arm for 90% power. Planning for 75% of that observed effect gives 175 and 234 per arm, respectively; planning for 50% gives 393 and 526. The second comparison has a very small observed difference: the corresponding figures for 100% of that effect are 11,453 and 15,332 participants per arm. The figures grow for smaller fractions of that effect.

The same pattern applies generally: a smaller target effect is harder to distinguish from random variation and therefore requires more participants under otherwise unchanged assumptions. These calculations use the observed baseline contrasts, so they should not be taken as a prescription for a future study or as evidence about the sample size needed for a follow-up treatment effect. The trial's own original sample-size assumptions and 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 = -0.110; pooled standard deviation σ = 0.275.
2. n = 2 × (1.96 + 0.842)² × 0.275² / -0.110² = 98.2, rounded up to 99 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 <- -0.11                      # observed difference in means
sigma <- 0.275131629939386                     # 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(2366689)
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 = 99 (80% power), 132 (90% power)
 75% of observed effect: n per arm = 175 (80% power), 234 (90% power)
 50% of observed effect: n per arm = 393 (80% power), 526 (90% power)
power.t.test: 99.2 
Simulated power at n = 99 per arm: 0.804 (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. Analyses Reported by the Sponsor

The registry reports the sponsor's overall ANOVA result across the three groups as p = 0.04. The posted recalculations are different in scope: each is an unadjusted pairwise comparison of baseline means, one comparing toothpaste plus mouthwash with toothpaste and the other comparing fluoride-only toothpaste plus mouthwash with toothpaste. They yield p-values of 0.03 and 0.839, respectively.

An overall ANOVA and separate pairwise tests answer different questions. An overall test assesses evidence of differences among the group means collectively; a pairwise test assesses a particular contrast. The registry record does not include the sponsor's ANOVA estimate, confidence interval, detailed model, or analysis-population description. It is therefore not possible to reconstruct its result or determine all reasons for the difference from the pairwise recalculations.

The recalculations are simple and unadjusted, based on the posted group summaries. The record flags a discrepancy, so the sponsor's own analysis takes precedence. This does not make the baseline timing limitation disappear: the listed primary score is at baseline, and the reported overall result cannot be interpreted as a comparison of reductions during product use. Follow-up analysis details are not reported in the registry record.

14. Multiplicity, Missing Data and Analysis Populations

The record lists six outcome measures and six analyses, but the posted information includes no secondary outcome results. The primary measure is baseline dental plaque score. The registry's overall ANOVA result concerns the three groups, while the two recalculated pairwise contrasts are additional comparisons. Testing multiple outcomes or contrasts raises a general multiplicity concern: when many hypotheses are tested, the chance of at least one apparently unusual result can increase. The registry record does not report whether the sponsor adjusted for multiplicity, specified a testing hierarchy, or designated which comparisons were confirmatory.

The pairwise recalculated p-values are explicitly unadjusted. They should therefore be read as results for their individual comparisons, not as multiplicity-controlled evidence across all outcomes and analyses. The sponsor's reported ANOVA is the analysis to prioritize where the record identifies a discrepancy, but the available entry does not provide enough detail to assess the overall analysis strategy. Whether the overall test was intended as a primary test or how subsequent contrasts were handled is not reported in the registry record.

Missing-data handling is also not reported. The listed baseline group counts are 60, 58 and 61, while the study enrollment is 179. These figures describe the registry entries and should not be assumed to establish which participants contributed to every outcome or follow-up. The record does not report missing outcome counts, reasons for missingness, imputation methods, or sensitivity analyses.

Analysis populations are not defined in the posted information. The registry record does not report whether analyses followed an intention-to-treat principle, used a per-protocol population, or applied another rule. It also does not report how adherence or departures from assigned products were handled. These omissions limit assessment of bias and reproducibility, especially for the study objective's follow-up period. They do not alter the plain reading of the listed endpoint: it is a baseline score, not a follow-up change measure.

15. 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 0% reporting threshold.

The registry lists zero serious adverse events in each of the three groups: the toothpaste group, the toothpaste-plus-mouthwash group, and the fluoride-only toothpaste-plus-mouthwash group. The corresponding numbers at risk are 60, 58 and 61. No serious adverse event terms are listed. These entries describe what the registry reports for the recorded serious-event category.

The record also lists zero other adverse events in each group, with the same group counts at risk. Death counts are not reported in the registry record. A zero recorded count is not proof that no event occurred outside the recorded data or reporting period, and these entries do not provide detail about event definitions, surveillance, timing, severity grading or causal assessment.

Safety findings should be considered alongside the available follow-up and reporting information. The registry record does not provide a fuller account of adverse-event collection or explain whether all participants were assessed for the same duration. These figures therefore describe the posted event counts; they do not establish a comprehensive safety profile or support medical advice.

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

The posted result supports a limited statistical description: the three groups had baseline mean plaque scores of 3.33, 3.22 and 3.34. The registry reports an overall ANOVA p-value of 0.04, and simple unadjusted recalculations give pairwise baseline differences of -0.11 and 0.01. The sponsor's reported analysis takes precedence over the recalculations where they differ.

These results do not show how much plaque changed after participants began using their assigned regimens. The primary measure is expressly timed at baseline, whereas the study objective refers to reduction over three and six months. A baseline difference is not a treatment effect, and the overall ANOVA result cannot be read as proof that a regimen reduced plaque or gingivitis. Follow-up outcome values and analyses are not reported in the registry record.

The results also do not establish whether any numerical difference is clinically meaningful. The plaque score is on a 0-to-5 scale, but the record does not report a threshold for an important difference. Statistical evidence, clinical relevance and treatment benefit are distinct questions. The available p-values address statistical compatibility with specified comparisons, not whether a difference matters to participants.

The record identifies randomization and triple masking, which are relevant design features, but the available details do not permit a full assessment of how those procedures were implemented or how missing data were handled. The reported zero adverse-event counts should likewise be interpreted as registry entries, not as proof of an absence of risk. Overall, the information permits interpretation of baseline plaque summaries and the registry's reported analysis, but not a conclusion about comparative reduction during product use.

17. Why This Trial Matters Statistically

This trial illustrates why outcome timing is essential to statistical interpretation. A study objective can describe a follow-up question, while a particular outcome entry may report only a baseline measurement. Means, confidence intervals and p-values can be calculated for baseline scores, but those statistics do not answer a question about change unless the analyzed outcome actually represents change or follow-up status.

It also illustrates the difference between an overall test and pairwise contrasts. The registry's ANOVA result addresses the groups collectively, while the recalculated comparisons focus on individual group contrasts. Those tests need not yield the same p-value because they do not pose identical questions or necessarily use identical methods. Clear reporting of estimates, uncertainty, model details and analysis populations is important for understanding how results relate.

The baseline summaries show that observed group means need not be identical even in a randomized study. Randomization is intended to balance groups on average, not to guarantee identical measured starting values in every trial. Examining baseline data can describe the realized groups, but an observed baseline difference should not be mistaken for an effect of assigned treatment.

Finally, the record shows why numerical significance and practical interpretation should remain separate. A p-value does not convey the magnitude or clinical importance of a difference, and a planning calculation based on an observed effect does not establish the design adequacy of the original trial. The limited outcome reporting makes these distinctions especially important: the posted information can be statistically described, yet it does not resolve the study's broader follow-up question.

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.

The main trial-specific limitation is the mismatch between the stated objective and the timing of the listed primary endpoint. The objective concerns reductions in plaque and gingivitis over three and six months, but the primary measure is a baseline plaque score. No follow-up plaque or gingivitis estimates are reported in the registry information. This prevents interpretation of the posted numbers as treatment-period changes.

The reported statistical detail is limited. The sponsor's ANOVA entry gives a p-value but no estimate, confidence interval, degrees of freedom or fuller model description. The pairwise values are unadjusted recalculations from summary statistics and do not reproduce the sponsor's own analysis. The discrepancy is flagged, so the sponsor analysis takes precedence, but the record does not provide enough detail to examine the difference.

Participant characteristics, eligibility criteria, randomization procedures, masking details, adherence, missing-data methods and analysis-population definitions are not reported in the information available. The group counts attached to the baseline measure do not establish the numbers analyzed at later time points. Multiplicity procedures for the listed outcomes and analyses are also not reported.

The record lists zero serious and zero other adverse events in each group, but provides no fuller account of collection methods or event follow-up. Death counts are not reported in the registry record. These limitations mean that the registry entries should be read as the reported summaries, not as a complete account of efficacy, safety or trial conduct.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Clinical Study Comparing Dental Plaque and Gingivitis Reduction After Using One of Three Oral Hygiene Multi-component Regimens (Using of a Manual Toothbrush, a Toothpaste and a Mouthwash) — NCT02366689.
• Registry record last updated 2016-03-30; status last verified 2015-02.
• Results first posted 2016-03-30.
• 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

NCT02366689 is a completed, randomized, triple-masked, parallel Phase 4 study sponsored by Colgate Palmolive. The listed enrollment is 179. It compared three oral-hygiene regimens, and its objective referred to plaque and gingivitis reduction over three and six months.

The listed primary outcome is mean dental plaque score at baseline on the Quigley-Hein Index, Turesky modification. The group means were 3.33, 3.22 and 3.34. The registry reports an overall ANOVA p-value of 0.04. Unadjusted recalculations compare baseline means; the sponsor's own analysis takes precedence where results differ.

Because the primary measure is baseline, these entries do not establish comparative reduction during product use. Follow-up results, detailed analysis methods, missing-data handling and original sample-size justification are not reported in the registry record. The adverse-event entries list zero serious and zero other events in each group; death counts are not reported.