Efficacy of Amoxicillin-metronidazole Compared to Clindamycin in Patients With Periodontitis and Diabetes: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy of Amoxicillin-metronidazole Compared to Clindamycin in Patients With Periodontitis and Diabetes (NCT03374176), a randomized phase 3 study. The primary outcome is Probing Depth.

2. Clinical Question

The trial summary describes a randomized clinical trial of antibiotic regimens used during non-surgical treatment. It frames the comparison against uncertainty about systemic antibiotic use in patients with diabetes; the posted results address the recorded trial comparison, not every possible antibiotic regimen or every patient with diabetes.

The primary endpoint is a continuous measure reported as a mean in millimeters. The registry also lists sites with plaques and sites with bleeding on probing as secondary outcomes. The summary describes a 24-months follow-up, while the primary endpoint and posted secondary outcomes have a 7 days timeframe. Those time references describe different elements of the record and should not be treated as interchangeable.

3. Trial Design

The registry identifies this as a phase 3, randomized, parallel-group trial, with completed status. It records enrollment of 42. The summary says patients were randomly assigned to amoxicillin/metronidazole or clindamycin and describes a 24-months follow-up. Both arm descriptions specify capsules taken tid during 7 days, with placebo included in the clindamycin arm.

The registry lists masking as triple, whereas the study summary calls the trial double-blind. The record does not explain the difference between those descriptions, so the masking arrangement cannot be characterized more precisely from the registry record. Random allocation and parallel groups mean the treatment arms were compared as separate groups rather than in a crossover sequence; that is a general description of the recorded design.

The registry records a start of 2014-03 and primary completion of 2016-07. It names Centro Universitario de Tonalá as sponsor. The summary reports clinical assessments of probing depth, bleeding at the probe and plaque index before and after pharmacological treatment. The posted primary endpoint result, however, is explicitly identified with a 7 days timeframe. The record does not provide further detail explaining the timing of each assessment in relation to the longer follow-up described in the summary.

The study summary says within-group differences were assessed with the Wilcoxon rank test and between-group differences with the Mann-Whitney test. It also says sex, bacterial plaque and bleeding to the sounding were summarized using proportions and analyzed with the chi-square method. These are descriptions in the summary; complete protocol details, analysis populations and the original statistical analysis plan 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 radiographic examination was undertaken using either periapical films or a pantomogram. Periodontal therapy was initiated within 1month of the baseline screening examination.

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 Probing Depth, measured over 7 days.

The primary endpoint is probing depth, reported in millimeters as a mean with standard deviation at 7 days. The summary describes probing depth as one of the clinical determinations used to assess the extent and severity of periodontitis, while the endpoint description identifies it as the size of the periodontal pocket. It is therefore a clinical measure of pocket depth rather than a patient-reported outcome or a count of participants experiencing an event.

In general, continuous measurements retain the amount of variation in a measurement rather than reducing the result to categories. A mean provides a group-level center, and a standard deviation describes the spread of individual measurements around that center. For clinical interpretation, the measurement’s meaning and timing matter: probing depth is a periodontal measure, and the posted endpoint is assessed at 7 days. The record does not give a threshold defining a clinically important difference, so statistical estimates alone cannot establish whether a particular difference would be important to patients or clinicians.

The study summary mentions assessments before and after pharmacological treatment, but the posted primary result is a group comparison at the stated 7 days timeframe. The registry does not provide a more detailed endpoint definition, such as a site-level aggregation rule or a prespecified clinically meaningful change. Those details are not reported in the registry record.

7. Results Posted in the Registry

• Clindamycin: mean 0.50 versus 0.44 on control; difference 0.06 (95% CI -0.08 to 0.20), standardized effect d = 0.27; z-test p = 0.389.

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.

Sites With Plaques

• 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:
  • Clindamycin: mean 15.80 versus 17.60 on control; difference -1.80 (95% CI -8.92 to 5.32), standardized effect d = -0.15; z-test p = 0.620.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Clindamycin and the control. The interval gives the range of effects that remain compatible with the data.

Sites With Bleeding on Probing

• 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:
  • Clindamycin: mean 22.10 versus 16.10 on control; difference 6.00 (95% CI -1.31 to 13.31), standardized effect d = 0.50; z-test p = 0.108.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Clindamycin and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes address related clinical features but do not measure exactly the same thing as probing depth. Sites with plaques and sites with bleeding on probing describe additional periodontal findings. Across these outcomes, the estimated group differences point in different directions, and the unadjusted intervals include no difference. This does not form a consistent pattern of clearly separated group results alongside the primary estimate.

That overall pattern should be read as exploratory rather than as independent confirmation of the primary result. Secondary measures can add context about the clinical picture, but they do not replace the primary endpoint or resolve uncertainty in its estimate. The registry identifies three secondary outcomes, while the record does not report a prespecified hierarchy or a plan for interpreting them jointly.

In general, testing several outcomes creates more opportunities for a nominally notable result to occur by chance. If results are interpreted without accounting for the number of comparisons, their evidential weight can be overstated. The registry record does not say whether multiplicity adjustments were planned or applied. The secondary comparisons are therefore best interpreted cautiously, especially because their estimates are unadjusted and their intervals do not exclude no difference.

The registry lists total count of all teeth lost across all participants as another secondary outcome, but no corresponding result is posted in the secondary outcome results summarized by this record. Its result and analysis are not reported in the registry record. It cannot contribute to the interpretation of the observed secondary pattern without those data.

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

• Sites With Plaques
• Sites With Bleeding on Probing
• Total Count of All Teeth Lost Across All Participants

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: probing depth is reported as a mean and standard deviation. A mean difference compares the group averages on the original measurement scale. Here, the comparison is expressed as clindamycin minus AMX-MET, so a positive estimate means the reported group mean is numerically higher in the clindamycin arm. This direction is a matter of how the contrast is defined; it does not by itself establish clinical benefit or harm.

What does a confidence interval describe?

In general, a confidence interval gives a range of values compatible with the observed data under a specified statistical procedure and its assumptions. It conveys uncertainty in an estimate, rather than measuring the spread of individual participant observations. A confidence interval that crosses zero for a mean difference includes no difference as one value compatible with the data. It may also include differences in either direction. That is why the point estimate alone should not be read as a definitive finding.

The recalculation uses posted arm-level means, standard deviations and group sizes to estimate an unadjusted difference and its uncertainty. It is a simple comparison of summary statistics, not a reconstruction of participant-level data. It does not adjust for covariates, account for any matching or clustering not described in the record, or reproduce every possible feature of the trial’s original analysis. Such details are not reported in the registry record.

Why can analysis methods give different answers?

The summary describes a Mann-Whitney test for between-group differences, while the simple re-calculation uses a mean difference and a confidence interval based on arm-level summary statistics. These methods do not necessarily test the same quantity in the same way. The Mann-Whitney procedure is rank-based: in general, it compares the ordering of observations between groups, rather than directly estimating the difference between arithmetic means. A result reported as a net mean difference alongside that procedure needs additional definition to understand exactly how the quantity was obtained.

The registry does not give the sponsor analysis confidence interval, the equivalence margin, or further detail on how the “Mean Difference (Net)” was calculated. Consequently, the reported p-value and the recalculated mean-difference interval cannot be treated as two versions of one identical analysis. The study summary says a Wilcoxon rank test was used for intra-group differences and a Mann-Whitney test for inter-group differences; it does not supply a full analysis plan or the assumptions and implementation details for each test.

Why does variation matter?

Standard deviations describe variation among the observations within each arm. When measurements vary substantially, a group mean may be estimated less precisely than when observations are more tightly grouped, all else being equal. In general, the standard error reflects uncertainty in an estimated mean or contrast and is influenced by both variability and sample size. The reported standard deviations are not confidence limits, and they should not be read as the range containing every participant’s measurement.

Some outcomes in clinical research can be over-dispersed: their variability exceeds what a simple probability model would expect. In general, ignoring over-dispersion can make uncertainty look too small. The posted primary outcome is continuous and summarized by means and standard deviations; the registry does not report a model-based over-dispersion assessment for it. It would be inappropriate to infer that such a problem was present or absent from the summaries alone.

What does the p-value mean?

In general, a p-value describes how unusual data at least as incompatible with a specified null model would be if that model and the test assumptions held. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. The recalculated unadjusted p-value of 0.389 is associated with the simple mean comparison. The sponsor-reported p-value of <0.05 belongs to the analysis labelled equivalence. Since those analyses differ, each p-value must be interpreted in the context of its own method and target.

The summary states that a P-value of <0.05 (two tailed) was considered statistically significant. It does not explain how that threshold was applied across all outcomes or whether any adjustments for multiple testing were planned. A threshold cannot replace the effect estimate and its uncertainty: the direction, magnitude, clinical relevance and precision all matter.

What can be concluded from summaries?

Arm-level summaries allow a transparent, unadjusted comparison, but they do not support every analysis that participant-level data would permit. They cannot show the distribution’s shape, identify outliers, describe correlations among repeated measurements, or verify how missing observations were handled. The record does not report participant-level data or enough methodological detail to resolve those questions. The re-calculation is therefore best read as a distinct, simple statistical comparison of the posted summaries, alongside—not in place of—the registry’s own reported analysis.

11. Confidence Intervals and Precision

The recalculated mean difference for probing depth is 0.06 mm, with a confidence interval from -0.076 to 0.197. This interval includes zero, so the data are compatible with no mean difference as well as with differences on either side of zero under the unadjusted calculation. The estimate is therefore not precise enough to fix the direction of the underlying group difference with confidence.

In general, interval width reflects statistical precision: narrower intervals indicate less uncertainty about the estimated contrast, while wider intervals indicate more. A confidence interval is not a guarantee that the true value lies within its endpoints, and it is not a range of individual participants’ probing depths. Its interpretation depends on the calculation and assumptions used. Here, the interval is from the simple unadjusted re-calculation of the posted summary statistics, not the sponsor’s reported analysis.

The registry’s own analysis lists a net mean difference of 0.05 and p <0.05 but gives no confidence interval. Without interval estimates and an equivalence margin for that analysis, its precision and equivalence criterion cannot be evaluated from the registry record. The re-calculated interval and sponsor-reported result therefore convey different information.

Precision is also distinct from clinical importance. The record does not define a clinically meaningful difference in probing depth, so the interval cannot be compared with a prespecified clinical threshold. It indicates statistical uncertainty in the estimated difference, not whether any compatible difference would matter in practice.

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, not total participants and not total events. The posted planning illustration uses the observed effect as its starting point and considers planning for 100%, 75% and 50% of that effect. It assumes a two-sided significance level of 0.05, equal allocation between the two arms and a normal approximation. These assumptions describe the illustration, not the original trial design.

The 80% power column describes the number of participants per arm that the illustration estimates would be needed to have an 80% chance of detecting the specified effect under its assumptions, if that effect were the true one. The 90% power column applies the same idea at a higher chance of detection. Higher target power generally requires more participants for a given effect. Planning for smaller effects requires more participants, because smaller differences are harder to distinguish from random variation.

For the primary endpoint, the illustration gives 222 participants per arm for 80% power and 298 participants per arm for 90% power when planning for 100% of the observed effect. For 75% of the observed effect, the corresponding figures are 395 and 529 participants per arm; for 50%, they are 888 and 1,189 participants per arm. These are planning illustrations, not a description of the enrolled group sizes or of what the trial achieved.

This is not observed power. It does not tell whether the completed trial had a particular probability of finding a result after the outcome was observed. The original sample-size justification and its planning assumptions are not reported in the registry record. The calculation is based on the observed effect, so it should be treated as a forward-looking illustration rather than evidence about the trial’s design rationale.

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 = 0.060; pooled standard deviation σ = 0.226.
2. n = 2 × (1.96 + 0.842)² × 0.226² / 0.060² = 221.9, rounded up to 222 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 <- 0.06                      # observed difference in means
sigma <- 0.22561028345357                     # 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(3374176)
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 = 222 (80% power), 298 (90% power)
 75% of observed effect: n per arm = 395 (80% power), 529 (90% power)
 50% of observed effect: n per arm = 888 (80% power), 1,189 (90% power)
power.t.test: 222.9 
Simulated power at n = 222 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.

14. Analyses Reported by the Sponsor

The registry reports a sponsor analysis using Wilcoxon (Mann-Whitney), with a “Mean Difference (Net)” of 0.05, p <0.05, and analysis type “equivalence.” The result is presented without confidence limits. Separately, the simple unadjusted re-calculation from the posted arm means and standard deviations gives a mean difference of 0.06 mm, a confidence interval that crosses zero, and p = 0.389.

These results are not identical analyses. The sponsor’s reported procedure is rank-based according to its stated method, while the re-calculation compares the arithmetic means from summary statistics. They also differ in the reported target and in the information available about uncertainty. A p-value from one procedure should not be directly substituted for the estimate and interval from another.

The registry labels the sponsor analysis as equivalence, but does not report the equivalence margin or a confidence interval for it. Without those elements, readers cannot assess the equivalence criterion in detail from the registry record. The simple re-calculation is not a correction to the sponsor analysis and does not reproduce its method. It offers a separate view of the posted summaries; the registry’s reported result remains the study’s own analysis, with the stated limitations in available detail.

15. Multiplicity, Missing Data and Analysis Populations

The study summary describes a primary endpoint and several clinical assessments, and the registry lists three secondary outcomes. When multiple outcomes or comparisons are tested, the chance of obtaining at least one apparently notable result can increase. In general, multiplicity procedures can control that risk, but they may also affect precision or the interpretation of individual tests. The registry record does not report whether a multiplicity plan was specified, whether secondary results were adjusted, or how the primary and secondary endpoints were ordered for confirmatory interpretation.

The summary reports a significance threshold of P-value <0.05 (two tailed), but it does not state whether that threshold applied separately to each test or as part of a broader strategy. The reported sponsor result is labelled equivalence, but the record does not give the equivalence margin, a confidence interval, or a detailed account of the analysis plan. Those omissions limit evaluation of the sponsor’s equivalence claim and of how it relates to other comparisons.

Missing-data handling is not reported in the registry record. The record does not state how many observations were available for each analysis, whether all randomized participants were analyzed, or how missing measurements were treated. It also does not identify an intention-to-treat, per-protocol or other analysis population. Without these details, readers cannot determine whether the posted group sizes reflect every randomized participant at the endpoint or whether exclusions or incomplete follow-up affected the estimates.

The summary describes a 24-months follow-up, but the primary endpoint result is assigned a 7 days timeframe. The record does not give enough detail to establish how later observations relate to the posted endpoint, or whether repeated measurements were modeled. The registry record also does not report the original sample-size rationale, interim analysis procedures, prespecified subgroup analyses or a complete statistical analysis plan. These are uncertainties about documentation, not evidence that any particular procedure was or was not used.

16. 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 0% reporting threshold.

The registry’s adverse-event entries record zero serious adverse events, zero other adverse events and zero deaths in each treatment arm. The figures describe what was entered in the registry for the groups at risk; they do not establish that no participant experienced any event outside the recorded categories, nor do they show that the regimens have identical safety profiles.

In general, a zero count in a trial does not prove that an event is impossible or that the underlying risk is zero. Safety estimates depend on the number of participants observed, the duration and completeness of follow-up, how events were defined and how they were collected. The registry record gives the arm-level at-risk and affected counts, but the adverse-event details needed to assess event definitions, ascertainment and the timing of observation are not reported in the registry record.

The trial summary describes follow-up of 24-months, whereas the primary endpoint is listed at 7 days. The adverse-event entries do not specify a timeframe in the record presented. The zero counts should therefore be interpreted as registry-reported figures, not as a comprehensive account of all possible harms or as a comparison capable of ruling out meaningful differences in safety.

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

The posted results describe a randomized comparison of two antibiotic regimens given during non-surgical treatment of periodontitis in patients with type 2 diabetes. For probing depth at 7 days, the group means are close in the posted summaries, and the simple unadjusted mean-difference interval includes zero. This means the re-calculation does not establish a clear difference in that measure; it does not show that the treatments are identical.

The registry also reports a sponsor analysis labelled equivalence with p <0.05. Its reported method and target differ from those of the unadjusted mean comparison, and the record does not give the equivalence margin or confidence interval needed to assess the equivalence criterion. The sponsor result should be understood as a separate reported analysis, not as a substitute for the re-calculation or a basis for claiming that all clinically relevant differences have been ruled out.

The record does not define a clinically important probing-depth difference. Statistical uncertainty and clinical importance are distinct: a statistically compatible range cannot be judged against a clinical threshold that is not reported. The secondary results provide additional periodontal measures, but their unadjusted nature and the lack of a reported multiplicity plan make them less persuasive as stand-alone evidence.

These findings do not establish a result for other populations, treatment schedules, endpoints or follow-up periods. The summary describes a longer follow-up, but the posted primary endpoint is at 7 days. The registry record does not provide sufficient analysis details to resolve all aspects of that timing, missing data or the sponsor’s equivalence procedure. Interpretation should remain limited to the recorded measures and analyses.

No treatment recommendation follows from these statistical results. They are a description of the posted evidence and its uncertainty, not a determination that one regimen should be selected or that either regimen is effective or ineffective in general.

18. Why This Trial Matters Statistically

This trial illustrates why the analysis label and the estimand—the quantity an analysis is intended to compare—matter as much as a p-value. The sponsor-reported rank-based analysis is labelled equivalence, while the transparent re-calculation estimates an unadjusted difference between arithmetic means. They answer questions in different ways, and the registry record does not provide enough detail to connect them fully.

It also illustrates the importance of reporting uncertainty. The recalculated interval crosses zero, which communicates that the posted summaries do not pin down the direction of the mean difference. A p-value alone cannot convey the range of compatible values or whether those values would be clinically important. The lack of an interval and equivalence margin for the sponsor’s analysis leaves a separate gap in interpretation.

Planning figures based on the observed effect show how strongly sample-size needs depend on the effect size a future study aims to detect. Smaller target differences require more participants per arm under the stated planning assumptions. These figures are not a retrospective score for the completed trial and do not reveal the original design rationale.

Finally, the record juxtaposes a 7 days primary endpoint with a summary describing 24-months follow-up, lists different masking descriptions, and does not report missing-data or multiplicity procedures. Such documentation distinctions are not minor statistical details: they affect what readers can verify and how broadly a result can be interpreted. Clear specification of estimands, timepoints, analysis populations, uncertainty and equivalence margins would make the evidence easier to assess.

19. 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 several trial-specific uncertainties. The summary describes double-blinding, while the registry lists triple masking; it does not explain how those descriptions correspond. The summary also describes a 24-months follow-up, but the posted primary and secondary outcome timeframes are 7 days. The relation between these timing descriptions is not reported in the registry record.

The sponsor analysis is labelled equivalence, but the registry does not give the equivalence margin, confidence interval or a detailed definition of the reported net mean difference. The simple re-calculation uses group summaries and cannot reproduce participant-level analyses, adjust for covariates, examine distributional features or verify the sponsor’s procedure. The posted information therefore supports a limited unadjusted comparison alongside the reported analysis, not a complete reanalysis of the trial.

The record does not report the analysis population, missing-data handling, complete outcome-specific denominators, or a multiplicity strategy. It also does not report a clinically important probing-depth threshold. These omissions limit assessment of selection, precision, statistical error across multiple comparisons and clinical relevance. The registry lists tooth loss as a secondary outcome but does not post its result in the recorded secondary findings.

Finally, the posted group sizes are small relative to the planning illustrations based on the observed effect, but those illustrations are not the original design calculation and should not be used to infer the investigators’ rationale. The original sample-size assumptions are not reported in the registry record. These limitations concern the scope and detail of the available record; they do not establish that an unreported procedure was omitted from the conduct of the trial.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Efficacy of Amoxicillin-metronidazole Compared to Clindamycin in Patients With Periodontitis and Diabetes — NCT03374176.
• Registry record last updated 2020-09-16; status last verified 2020-09.
• Results first posted 2020-06-23.
• 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.

23. Record Summary

NCT03374176 is a completed randomized, parallel-group phase 3 trial sponsored by Centro Universitario de Tonalá. It compared amoxicillin 500 mg plus metronidazole 250 mg with clindamycin 300 mg plus placebo in patients with periodontitis and type 2 diabetes. The registry records enrollment of 42 and a primary outcome of probing depth at 7 days.

The unadjusted re-calculation gives a mean difference of 0.06 mm and an interval that crosses zero. The registry separately reports a Wilcoxon (Mann-Whitney) analysis labelled equivalence, with a net mean difference of 0.05 and p <0.05. The record does not provide the equivalence margin or confidence interval needed to assess that analysis in detail. Secondary results are unadjusted, and multiplicity, missing-data and analysis-population procedures are not reported in the registry record.