Effect of Two Toothpastes on Bacteria in Saliva: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of Two Toothpastes on Bacteria in Saliva (NCT03587428), a randomized na study. The primary outcome is Change From Baseline in Area Under the Curve Between 0 and 2 Hours (AUC [0-2] Hours) for Total Viable Counts (TVCs) of Bacteria in Saliva Using Traditional Plating Technique.

2. Clinical Question

The study focused on an early, defined period after product use, rather than on longer-term oral-health outcomes. Its stated purpose was to investigate the ability of the two zinc-containing formulations to reduce the level of bacteria in saliva during the two-hour period after use, compared with water alone. That description identifies the research question; it does not establish what the observed results were.

The registry lists four outcome measures in total. In addition to the primary measure, the listed secondary measures concern the live-to-dead bacteria ratio and log10-transformed total viable bacterial count. The record does not report the numerical findings for those measures or the specific treatment comparisons made for each one.

3. Trial Design

The registry describes this as a randomized, double-blind, crossover study with enrollment of 15 participants. It is marked completed. The study start date is 2014-11-04, and the primary completion date is 2014-11-27. The sponsor is GlaxoSmithKline.

In a crossover design, participants receive more than one study condition, so comparisons can be made within the same participant as well as across treatment conditions. This is a general feature of the design, not a statement about the exact sequence or analysis used in this study. The registry identifies the model as crossover and lists three conditions: Zinc-A toothpaste, Zinc-B toothpaste, and mineral water. It does not report the treatment sequence, how sequence allocation was carried out, or whether there was a washout period between conditions.

Randomization is recorded, and masking is recorded as double. These labels indicate that the registry classifies the study as randomized and double-masked, but it does not identify which people were masked or explain how masking was maintained. The record also does not describe the allocation procedure, concealment, or whether masking was assessed.

The primary outcome was a continuous measure of change from baseline in a log-transformed bacterial-count measure derived from observations over 0 to 2 hours. The registry identifies the efficacy analysis as using the ITT population. It does not report the number of participants contributing data to each treatment condition, whether all enrolled participants completed every condition, or how incomplete measurements were handled.

The registry lists the study phase as NA. It gives Oral Health as the condition and describes the study as an investigation of two zinc-containing toothpaste formulations and mineral water. Further protocol details, including eligibility criteria, study setting, and the operational procedures for treatment administration and saliva collection, 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.

Before assignment: A total of 16 participants were screened, out of which 1 did not met the study criteria. Total of 15 participants were randomized to study treatments.

Period 1

Period 2

Period 3

Analysis population for the primary outcome, as defined in the registry: The efficacy analysis was performed on Intent to Treat (ITT) population.

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.

Population: All participants completed the study and were included in the safety and intent-to-treat (ITT) populations. All efficacy analyses were conducted on the ITT population.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline in Area Under the Curve Between 0 and 2 Hours (AUC [0-2] Hours) for Total Viable Counts (TVCs) of Bacteria in Saliva Using Traditional Plating Technique, measured over Change from baseline in log10-transformed AUC 0-2hr.

The primary endpoint is the change from baseline in the area under the curve from 0 to 2 hours for total viable counts of bacteria in saliva, measured using traditional plating. The registry describes the bacterial counts as anaerobic total viable counts and gives the unit as Log10 (cells/ml). The reported summary type is a mean, with standard deviation as the dispersion measure, but the registry record does not report the group means or standard deviations.

The description explains that measurements were logged and analyzed by change in log, then combined across the 0-to-2-hour period using the trapezoidal rule. The resulting AUC measure was divided by 2 hours to remove the time unit and then logged to calculate the bacteria count. In general, an area-under-the-curve summary can represent measurements across a period rather than relying on a single time point. The record characterizes this endpoint as a summary of change from baseline over the specified period.

Using a log-transformed count is a way to express bacterial measurements on a transformed scale. The endpoint is therefore not a direct count of individual bacteria and should be interpreted in its stated log-scale units. Its inclusion gives the study a defined measure for comparing the short-term bacterial-count profile across conditions. The registry does not report the values needed to describe the observed magnitude, direction, or precision of any treatment contrast.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized, double-blind crossover study. In general, randomization is used to reduce systematic differences in treatment assignment, while masking is intended to limit the influence of knowledge about assigned treatment. A crossover design compares multiple conditions in the same participants, which can account for stable differences between individuals when the analysis is appropriately specified. These are general explanations of the design terms; the registry does not report the randomization procedure, who was masked, or the exact analysis model.

What does the primary endpoint summarize?

The primary measure summarizes change from baseline in total viable bacterial counts across the period from 0 to 2 hours. The registry states that traditional plating was used and that the endpoint concerns anaerobic bacteria. Measurements were logged, expressed as change in log, combined across time using the trapezoidal rule, divided by 2 hours, and logged to calculate the bacterial count. This construction is intended to summarize the measured profile across the specified interval rather than report only one post-treatment time point. It is expressed in Log10 (cells/ml).

In general, the trapezoidal rule approximates the area under a curve by connecting observed time-point measurements with straight lines and summing the resulting areas. The registry record does not list the individual collection times beyond the stated interval endpoints, the observed measurements, or the calculation values for any participant. It therefore does not allow independent review of the endpoint calculation.

Why use a logarithmic scale?

In general, logarithmic transformation can make a wide range of count values easier to analyze and can change how differences are interpreted. A difference on a log scale is not the same thing as a difference in the original count scale. The registry specifies a log10-transformed measure and its unit, but does not report the numerical estimates needed to interpret the size of any contrast. No conversion to an original-scale effect is reported.

Over-dispersion is a general concern when count data vary more than a simple statistical model expects. A model that does not account for the actual variability can give uncertainty estimates that are too narrow or otherwise poorly calibrated. The primary endpoint is described as a mean of a continuous log-transformed measure, not as a count-model parameter. The registry record does not report a model diagnosis or an assessment of over-dispersion, so it is not possible to say whether that issue was evaluated or relevant to the analysis used.

How should the crossover design be understood?

In general, crossover studies can improve efficiency when within-participant measurements are correlated, because each participant contributes information under more than one condition. Valid interpretation also depends on design and analysis details, including treatment order, possible period effects, and whether effects from one condition carry into a later condition. These issues are especially relevant to deciding how within-person comparisons should be estimated. The registry record does not report the sequence, period structure, washout, carryover assessment, or statistical model, so the handling of these considerations is unknown.

What do the summary and planning methods mean?

The registry identifies the primary measure as a mean with standard deviation. In general, the mean describes the average on the analyzed scale, while the standard deviation describes variation among measurements on that scale. Neither is an estimate of uncertainty in a treatment contrast by itself. A confidence interval for a contrast would also depend on the sample size, variability, design, and analysis. The registry does not report the outcome summaries or confidence intervals.

The registry describes a sample-size planning illustration based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; it also describes planning for stated fractions of the observed effect. These are planning assumptions, not a report of the trial's design justification. The numerical planning results are not reported in the registry record. A planning illustration is not observed power and does not establish the probability that the study detected an effect.

The record does not report the test statistic, model specification, confidence level, method for calculating standard errors, or whether adjustment for multiple comparisons was used. These omissions prevent a fuller assessment of the statistical analysis. The available method description supports identifying the endpoint construction and broad design, but not reconstructing the analysis or verifying the results.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures, including the primary measure and secondary measures concerning live-to-dead bacteria ratios and total viable bacterial counts. It also lists two analyses. The record does not explain how the two analyses relate to the outcome measures, which treatment contrasts were planned, or whether the primary outcome was analyzed at more than one time point or in multiple ways.

In general, testing several outcomes or contrasts can increase the chance that at least one result appears notable by chance. Statistical plans may address this through a prespecified hierarchy or adjustment, among other approaches. The registry record does not report whether any multiplicity strategy was planned or used. Because numerical outcome results are not reported either, the impact of multiplicity cannot be assessed.

The efficacy analysis population is identified as ITT. The record does not say how ITT was defined for this crossover study, which participants or measurements were included in the final analyses, or whether any exclusions occurred after enrollment. It also does not report missing-data amounts, reasons for missingness, imputation, sensitivity analyses, or other methods for incomplete observations.

These omissions matter because missing measurements and repeated treatment periods can affect the analysis and interpretation. In general, an ITT label alone does not explain how missing outcomes were handled or whether all randomized participants contributed data to each comparison. The registry record does not report these details, so the completeness and robustness of the efficacy analyses cannot be evaluated from the record.

11. 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 1% reporting threshold.

The registry lists three adverse-event groups: Zinc-A Toothpaste, Zinc-B Toothpaste, and Mineral Water. For each group, 15 participants are listed as at risk for serious adverse events and 0 as affected; the figures for other adverse events also list 15 at risk and 0 affected. Deaths are recorded as 0 in each group.

These figures are counts in the registry's adverse-event record. They indicate that no serious adverse events, other adverse events, or deaths were recorded in the listed groups. They do not establish that no events could occur, and they do not describe the nature, timing, or severity of any events beyond the categories shown. The record does not provide additional safety details or explain how adverse events were collected and monitored.

The study is described as crossover, but the adverse-event groups list the same at-risk count for each condition. These figures should be read as the registry's displayed group-level counts, not as a basis for reconstructing individual exposure periods or comparing event rates. No further details about the safety analysis population or exposure duration are reported in the registry record.

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

The registry record establishes that a randomized, double-blind crossover study evaluated two zinc-containing toothpaste formulations and mineral water in relation to bacterial measures in saliva. It describes a primary endpoint based on change from baseline in a log-transformed AUC summary of total viable bacterial counts over 0 to 2 hours. It also identifies secondary outcomes concerning bacterial viability and counts.

It does not report numerical primary or secondary outcome results. There are no treatment-group estimates, contrasts, confidence intervals, or p-values in the registry record. As a result, the record does not show how the bacterial measures changed under each condition, how the conditions compared, or how precisely any difference was estimated. It cannot support a conclusion about the direction, magnitude, or statistical uncertainty of a treatment effect.

The study's endpoint is a short-term measure of viable bacteria in saliva. In general, a measure of this kind describes only the outcome and period that were assessed. It does not by itself answer questions about longer-term outcomes or other aspects of oral health. The record does not report such outcomes.

The adverse-event figures list 0 serious adverse events, 0 other adverse events, and 0 deaths in each of the three groups, with 15 at risk in each category per group. These are the recorded counts and should not be extended into broader claims about safety beyond the study record.

The registry contains useful information about the study question, design labels, endpoint construction, analysis population, and recorded adverse events. Important information for interpreting efficacy—including the actual outcome findings, analysis model, missing-data handling, and multiplicity approach—is not reported in the registry record. The appropriate reading is therefore descriptive: the study was conducted to examine a defined short-term outcome, while the posted record does not present the numerical evidence needed to assess its findings.

13. Why This Trial Matters Statistically

This study illustrates how a statistical endpoint can turn repeated measurements over a short period into one summary for analysis. The primary outcome is not a single bacterial count at one time point; it is described as a change-from-baseline AUC measure over 0 to 2 hours, constructed from log-transformed measurements. Understanding that construction is important because the result would be interpreted on the stated log scale and over the stated interval.

The crossover design also highlights the role of within-participant comparisons. In general, these designs can account for stable participant-level differences, but interpretation depends on treatment order, period effects, carryover, and the analysis model. The registry identifies the design but does not report the details needed to evaluate how those issues were handled. That distinction shows why a design label alone is not a complete statistical methods description.

The record also demonstrates why endpoint definitions and outcome results must be read separately. A detailed endpoint description clarifies what was intended to be measured, but does not reveal the observed effect or its uncertainty. Here, the registry describes the primary measure and summary type while omitting numerical results, so the treatment comparisons cannot be assessed.

Finally, the listed sample-size approach is explicitly a planning illustration based on an observed effect, rather than a report of the trial's own design justification. General planning calculations are useful for considering future studies, but they are not evidence that the present study had a particular probability of detecting an effect. The record's distinction between planning and observed results is statistically important, especially when the reported enrollment is 15 and outcome estimates are unavailable.

14. 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.

A central limitation of the registry record is the absence of numerical efficacy results. It describes the primary endpoint, but does not report treatment-group means, standard deviations, contrasts, confidence intervals, or p-values. This prevents assessment of effect direction, magnitude, and precision.

The crossover design is identified, but key details are not reported: treatment sequence, period structure, washout, carryover assessment, and the model used to account for repeated conditions. These omissions make it difficult to judge whether the statistical approach matched the design. The record also does not describe randomization procedures or who was masked.

The registry names the ITT population but does not explain how it was defined or how incomplete data were handled. It does not report participant flow by treatment condition, the completeness of measurements, reasons for missingness, or sensitivity analyses. With enrollment of 15, the absence of these details limits evaluation of the analysis population and the stability of estimates; no numerical precision can be inferred from enrollment alone.

The listed outcomes include several bacterial measures, but the registry does not explain the relationship between the four outcome measures and two analyses, identify all planned comparisons, or report a multiplicity strategy. It also does not provide the participant-level measurements or enough calculation detail to independently reproduce the AUC endpoint.

Finally, the endpoint concerns a short-term saliva measure over 0 to 2 hours. The registry does not report longer-term outcomes or additional oral-health measures. These are limitations of the available record and the scope of the described endpoint, not evidence for or against any treatment effect.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effect of Two Toothpastes on Bacteria in Saliva — NCT03587428.
• Registry record last updated 2019-07-15; status last verified 2019-04.
• Results first posted 2019-07-15.
• 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.

18. Record Summary

The completed study, NCT03587428, is titled “Effect of Two Toothpastes on Bacteria in Saliva.” The registry describes a randomized, double-blind crossover study sponsored by GlaxoSmithKline, with enrollment of 15 and a study start date of 2014-11-04. The primary completion date is 2014-11-27.

The study compared Zinc-A toothpaste and Zinc-B toothpaste, each administered as a slurry, with mineral water. Its primary outcome was change from baseline in a log-transformed AUC measure of total viable bacterial counts in saliva over 0 to 2 hours, assessed using traditional plating. The efficacy analysis population is identified as ITT.

The registry lists four outcome measures and two analyses, but does not report numerical efficacy findings or details of the statistical model, missing-data handling, or multiplicity approach. The adverse-event record lists 0 serious adverse events, 0 other adverse events, and 0 deaths in each group, with 15 at risk for each category per group.