Plasma of Argon Cleaning on Implant Abutments: 5-year Results of a Randomized Clinical Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Plasma of Argon Cleaning on Implant Abutments: 5-year Results of a Randomized Clinical Trial (NCT02552810), a randomized na study. The primary outcome is Success Rate of the Implants and Prostheses (Participants)..

2. Clinical Question

3. Trial Design

This was a randomized, double-masked, parallel-group clinical trial listed as completed. It compared plasma of argon cleaning of implant abutments with steam cleaning. The registry record lists enrollment of 30 and describes the study population as patients with a history of periodontal disease and thin biotype. The official title also identifies the five-year post-loading assessment. The record gives a start date of 2010-01 and a primary completion date of 2010-09.

The study addressed whether the cleaning protocol was associated with radiographic bone changes around customized, platform-switched abutments placed according to the one-abutment-one-time protocol. The registry’s primary outcome, however, was the success rate of implants and prostheses among participants during all follow-up, with a five-year timeframe. Additional outcomes covered marginal bone level changes, esthetic measurements, plaque index, bleeding on probing, and biological or technical complications.

Both groups are reported with 15.0 participants for the primary outcome. The record reports 100.0% success in each group. It does not describe the randomization sequence, allocation concealment, the details of masking, adherence to the assigned cleaning protocol, or the handling of participants who might not have completed follow-up. Those details are not reported in the registry record. The listed design features alone therefore do not establish how these aspects were carried out.

The record identifies the University of Valencia as sponsor and lists the phase as not applicable. It does not report a sample-size justification or a detailed statistical analysis plan. The study’s short enrollment interval and long-term outcome timeframe are part of the registry information, but they do not establish how follow-up was organized or how outcomes were assessed at each visit.

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 Success Rate of the Implants and Prostheses (Participants)., measured over During all the follow-up (5 years).

The primary endpoint was the success rate of implants and prostheses among participants during all follow-up, with the timeframe specified as five years. It was expressed as a percentage of participants. The registry defines implant failure using clinical, radiographic, and mechanical criteria: mobility or signs such as radiolucency, progressive marginal bone loss, or infection, as well as a mechanical complication that rendered the implant unusable. Prosthesis failure was defined as the need to replace it with an alternative prosthesis.

This endpoint combines implant and prosthesis status into a clinically interpretable success measure. It aims to capture failures that could arise through more than one route, rather than relying only on a radiographic measurement. The criteria also make clear that a mechanically stable implant could still count as a failure if a complication made it unusable.

The registry reports 100.0% success in both cleaning groups. The equal reported percentages describe the observed result in the participants represented in the outcome data; they do not demonstrate that the protocols are equivalent in the broader population. With no failures reported, this endpoint offers little information about how the groups might differ in settings where failures occur. The record does not report a separate outcome estimate for implants versus prostheses or explain how any participant-level outcome was formed when both were considered.

7. Results Posted in the Registry

• Steam Clean: 100.0% (15/15) versus 100.0% (15/15) on control; risk difference 0.0 percentage points (95% CI 0.0 to 0.0), risk ratio 1.00 (1.00–1.00); unadjusted two-proportion z-test p = n/a.

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.

Peri-implant Marginal Bone Level Changes (Express in mm).

• 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:
  • Steam Clean: mean 0.65 versus 0.21 on control; difference 0.44 (95% CI 0.23 to 0.65), standardized effect d = 1.49; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Steam Clean than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Percentage of Patients With Plaque Index

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Steam Clean: 13.3% (2/15) versus 13.3% (2/15) on control; risk difference 0.0 percentage points (95% CI -24.3 to 24.3), risk ratio 1.00 (0.16–6.20); unadjusted two-proportion z-test p = 1.000.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Steam Clean and the control. The interval gives the range of effects that remain compatible with the data.

Percentage of Patients With Bleeding on Probing

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Steam Clean: 20.0% (3/15) versus 6.7% (1/15) on control; risk difference 13.3 percentage points (95% CI -10.5 to 37.2), risk ratio 3.00 (0.35–25.68); unadjusted two-proportion z-test p = 0.283.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Steam Clean and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes cover different dimensions: marginal bone level, plaque index, bleeding on probing, esthetic changes, and biological or technical complications. The results available in the registry include the bone-level measure and the two oral-health percentages. The outcome descriptions also list esthetic measures and complications, but their results are not reported in the registry record.

Across the reported secondary outcomes, the pattern is not uniform in the type of measure: one is a continuous average, while the others are percentages based on relatively few events. The posted estimates therefore have different interpretations and precision. The binary outcomes have intervals that include no difference and allow for effects in either direction. The bone-level contrast is more clearly separated from zero in its unadjusted calculation, but its clinical importance cannot be determined from statistical evidence alone. This broad pattern does not alter the primary result: both groups have the same reported success percentage, with no primary failures recorded.

Secondary outcomes can provide context about related aspects of an intervention, but they do not replace the primary endpoint. They may also be exploratory, particularly when several outcomes are tested. In general, unadjusted analyses do not control the increased chance of a nominally notable result across multiple comparisons. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or which analyses were prespecified. Consequently, a nominal p-value for an individual secondary measure carries less weight than a result supported by a prespecified analysis and a transparent plan for multiple testing.

These limitations do not make secondary outcomes uninformative. They indicate that the estimates are signals to interpret alongside their uncertainty, the study design, and the incomplete reporting. The record does not support a single overall conclusion that all secondary measures favor one cleaning approach.

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

• Any Biological or Technical Complications.
• Peri-implant Marginal Bone Level Changes (Express in mm).
• Esthetic Parameters Measured as the Changes in Mesial and Distal Papilla Height (PH) and Buccal Peri-implant Mucosa Changes at the Zenith (REC), Expressed in mm.
• Percentage of Patients With Plaque Index
• Percentage of Patients With Bleeding on Probing

9. Statistical Interpretation

10. Statistical Methods Explained

The trial is described as randomized, double-masked, and parallel-group. Randomization is intended, in general, to reduce systematic differences between groups at the start of a study. Masking is intended, in general, to limit the influence of expectations on care or outcome assessment. These design labels do not disclose the implementation details; the randomization procedure, allocation concealment, and masking arrangements are not reported in the registry record.

What does the primary comparison estimate?

The primary outcome is a binary success classification expressed as a percentage of participants. A risk difference compares the event proportions between groups by subtraction. In this trial, the posted success percentages are 100.0% in both groups, and the simple unadjusted re-calculation gives a risk difference of 0.0. Since the endpoint is success, a difference would describe a difference in the percentage meeting the success definition; interpretation should keep the endpoint’s direction in view.

The calculation is unadjusted: it uses the posted group summaries and does not account for covariates or other design features. No adjusted primary estimate is reported in the registry record. The confidence interval for the recalculated primary comparison is 0.0 to 0.0, but the absence of observed failures means that this calculation cannot communicate the uncertainty that would be relevant to future populations in a meaningful way. It should not be treated as proof that the true difference is exactly zero.

How should the reported test be understood?

The registry lists a Wilcoxon (Mann-Whitney) method and p < 0.05 for an analysis categorized as non-inferiority or equivalence. In general, the Mann-Whitney test compares the distributions of observations between groups; it is not ordinarily a direct comparison of two binary percentages. The record does not say which outcome was tested, how the test was applied, what margin defined non-inferiority or equivalence, or what estimate and interval accompanied the test. Those omissions prevent a reliable interpretation of the reported p-value in relation to the primary success result.

In general, a non-inferiority analysis asks whether an intervention is not worse than a comparator by more than a prespecified margin; an equivalence analysis asks whether a difference lies within a prespecified range. The margin is essential to these conclusions. A small p-value by itself does not establish either conclusion. The margin, underlying estimate, and detailed analysis are not reported in the registry record.

What do the secondary analyses add?

For continuous marginal bone change, the registry reports group means and standard deviations at five years, and a mean difference with a confidence interval. A mean difference describes the contrast between group averages. A standard deviation describes variability among observations, while a confidence interval expresses the uncertainty around an estimated contrast under the assumptions of the calculation. The unadjusted p-value is a separate summary of compatibility with a null hypothesis; it does not quantify the size or clinical importance of the difference.

For plaque index and bleeding on probing, the outcomes are reported as percentages. Their recalculated risk differences compare group proportions. With few events, such estimates can be imprecise: a change in a small number of observations can materially affect the estimated proportions. The broad intervals for these outcomes reflect substantial uncertainty. The estimates and p-values are unadjusted; the registry does not report a multiplicity correction.

General statistical practice treats a collection of unadjusted secondary tests cautiously because testing multiple outcomes increases the chance of obtaining a nominally notable result even when there is no true difference. A prespecified outcome hierarchy or adjustment strategy can help address that issue, but neither is reported in the registry record.

What do planning illustrations mean?

The planning illustrations use the observed effect as a reference and show hypothetical participants per arm for stated fractions of that effect, under a two-sided significance level of 0.05, equal allocation, and a normal approximation. In general, such calculations ask how large a future study might need to be to detect an assumed effect with a chosen power under stated assumptions. They are not the observed power of this trial, and they are not evidence that the original trial was designed around those effects. The original sample-size justification is not reported in the registry record.

These planning values are especially sensitive to the observed effect used as their starting point. If a small study produces an unstable estimate, calculations based on that estimate can also be unstable. The illustrations are therefore scenario-specific rather than a definitive sample-size recommendation. No additional assumptions about attrition, eligibility, or analysis populations should be inferred from them.

11. Confidence Intervals and Precision

The primary outcome has no observed failures in either group: the reported success rate is 100.0% in each. The simple unadjusted risk-difference re-calculation is 0.0, with a confidence interval from 0.0 to 0.0. That interval is a feature of the calculation with identical all-success summaries, not a realistic indication that the population difference is known without uncertainty. When an outcome is at a boundary, ordinary summary-based calculations can fail to convey the uncertainty that would arise in repeated samples.

For the secondary continuous outcome, mean marginal bone change is 0.21 mm in the plasma of argon group and 0.65 mm in the steam-clean group. The reported mean difference is 0.44 mm, with a confidence interval from 0.229 to 0.651. The interval lies on one side of zero, while the unadjusted p-value is < 0.001. These are statistical summaries of the observed contrast; they do not by themselves establish the clinical importance of that difference. A threshold for clinical importance is not reported in the registry record.

For plaque index, the reported percentages are 13.3% in each group; the risk-difference interval extends from -0.243 to 0.243. For bleeding on probing, the percentages are 6.6% and 20.0%, with a risk-difference interval from -0.105 to 0.372. These intervals include zero and also span values in either direction. In general, a confidence interval describes a range of estimates compatible with the data under the method’s assumptions; it is not a probability statement that the true effect lies in that particular interval.

The relatively small group summaries and few events for these binary outcomes mean that estimates can be imprecise. The registry does not report confidence intervals for the sponsor’s primary analysis, nor the method or assumptions for that analysis. The recalculated intervals are unadjusted and should not be confused with an analysis accounting for covariates, repeated measurements, or multiplicity.

12. Analyses Reported by the Sponsor

The registry lists the sponsor-reported analysis as a Wilcoxon (Mann-Whitney) test with p < 0.05, classified as a non-inferiority-or-equivalence analysis. It does not give an effect estimate, confidence interval, margin, or a clear statement of which outcome was analyzed. As a result, the reported test cannot be directly reconciled with the primary outcome summaries, which show 100.0% success in both groups.

The simple unadjusted re-calculation of the primary percentages gives a risk difference of 0.0 and a confidence interval from 0.0 to 0.0. This calculation is based only on the posted summaries and is not a substitute for a fully specified sponsor analysis. The registry record does not flag a discrepancy between the sponsor result and the recalculation. Even so, the missing details mean the sponsor’s p-value should not be read as evidence that the two groups are equivalent or non-inferior: such a conclusion requires an interpretable estimate and a prespecified margin, neither of which is reported in the registry record.

The sponsor-reported analysis and the simple re-calculation answer questions that cannot be assumed to be the same. The former is incompletely described; the latter describes the observed binary summaries without adjustment. Neither should be extended beyond the information each contains. No claim about a treatment effect can be established from the p-value alone.

13. Multiplicity, Missing Data and Analysis Populations

The registry record does not report whether the primary analysis followed an intention-to-treat, per-protocol, or other analysis population. It also does not state how missing outcome data were handled, whether all randomized participants completed five-year follow-up, or whether any participants were excluded from particular analyses. These details matter because an outcome summary may depend on who was included and how missing observations were treated. No assumptions about completeness or exclusions can be made from the reported group summaries alone.

The primary outcome is described for five years, and implant stability is said to have been assessed at initial loading and following 3 years of application with prostheses removed. The record does not give a fuller schedule of assessments or explain which assessment time point determined the final success classification. It also does not report whether outcome assessors were masked or how disagreements in classification were resolved.

Several secondary outcomes are listed, and unadjusted results are available for some of them. The registry record does not report a plan for controlling multiplicity, a hierarchy of endpoints, or whether the secondary analyses were prespecified. In general, examining multiple outcomes without adjustment can make isolated nominal findings less persuasive because the chance of at least one apparently notable result rises across a collection of tests. This concern does not show that any finding is false; it is a reason to interpret secondary p-values cautiously.

The original sample-size justification, assumptions about the expected effect, and any planned interim analyses are not reported in the registry record. There is also no reported explanation of how the sponsor’s non-inferiority-or-equivalence label relates to its test or what margin was used. The available planning illustrations are based on observed effects and stated assumptions, not a record of the trial’s original design rationale. Without the missing analysis details, the registry results cannot establish whether the reported analyses followed a prespecified statistical plan.

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 0% reporting threshold.

The adverse-event record lists zero serious events affecting participants at risk in each group. It also lists zero other events affecting participants at risk in each group. Death counts are not reported in the registry record. These entries describe what is recorded for the groups; they do not establish that no events occurred outside the categories or definitions captured by the registry.

In general, an absence of recorded events in a small study does not show that an intervention carries no risk. The study’s group summaries provide limited ability to detect uncommon harms, and the registry does not provide event descriptions, severity details beyond the serious-event classification, timing, or attribution assessments. The absence of serious events should therefore be read as a feature of the recorded follow-up, not as a guarantee of safety or a comparison proving one cleaning approach safer than the other.

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

The main result is straightforward at the level of the observed primary outcome: the registry reports 100.0% implant and prosthesis success in both the plasma of argon and steam-clean groups during the five-year timeframe. The posted group summaries show no observed difference in this measure. That result is relevant to the study’s stated question, but it does not establish that the underlying effects are identical.

In general, a study with no observed failures in either group cannot estimate how the groups compare when failures occur. Its observed percentages may look identical while uncertainty about future participants remains. The recalculated zero difference and zero-width interval should be understood in that context, rather than as proof of exact equivalence. A valid equivalence or non-inferiority conclusion requires a defined margin and an analysis that can be interpreted against that margin; those details are not reported in the registry record.

The secondary findings describe other outcomes, including bone-level change and oral-health measures. They may help characterize the study’s observations, but they do not establish an overall treatment effect or replace the primary outcome. The record does not report results for every listed secondary measure, and it does not provide a reported strategy for multiple comparisons. Statistical differences in a secondary endpoint, where observed, are not by themselves evidence of clinical importance.

The record also leaves important uncertainties about follow-up completeness, missing data, analysis populations, and outcome assessment. Those gaps limit how confidently the observed percentages can be generalized. The results apply to the participants and procedures represented in the registry, not automatically to other populations, abutment protocols, or clinical settings.

Thus, the most defensible reading is that no primary failures were recorded in either group in the posted summaries. The result is not evidence that the protocols are interchangeable, that either prevents failure, or that one is preferable. It is a description of the recorded trial outcomes whose precision and interpretation are constrained by the small group summaries and incomplete statistical reporting.

16. Why This Trial Matters Statistically

This trial is statistically interesting because its primary outcome is at a boundary: every participant represented in each group is reported as having a successful implant and prosthesis. Such a pattern can be reassuring as a description of the observed sample, but it poses a challenge for comparative inference. With no failures in either group, the data do not reveal how failure rates might differ in a larger or different population.

The case also illustrates why the method and estimand must match the outcome. The primary result is a binary success percentage, while the registry’s reported test is a Wilcoxon (Mann-Whitney) analysis categorized as non-inferiority or equivalence. Without a clear link between the test and the endpoint, an estimate, and a margin, the p-value cannot support a transparent claim about the primary comparison. Statistical labels alone do not make an analysis interpretable.

The secondary outcomes show a complementary issue: different outcome types yield different kinds of estimates and uncertainty. A mean difference in bone change and risk differences for binary indicators cannot be treated as interchangeable. The intervals and event counts matter, as does the possibility of multiple testing. The registry’s incomplete reporting of some listed outcomes further limits synthesis.

For clinical researchers, the record emphasizes the value of reporting the analysis population, missing-data approach, outcome-specific estimates, confidence intervals, prespecified margins, and multiplicity plan. Without these elements, readers can still describe the posted results, but should be cautious about claims that go beyond the observed summaries. The statistical lesson is not that a null difference proves sameness; it is that evidence of similarity requires a design and analysis capable of addressing similarity directly.

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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

Several limitations are specific to the information available for this trial. The primary outcome has a ceiling pattern, with 100.0% success reported in each group and no failures recorded. This leaves little information for estimating a comparative failure effect, despite the equal percentages. The simple recalculated interval of 0.0 to 0.0 should not be interpreted as genuine certainty about the population difference.

The sponsor-reported analysis is difficult to interpret alongside the primary endpoint. The registry gives a Wilcoxon (Mann-Whitney) method and p < 0.05, but does not identify the tested outcome, provide an estimate or confidence interval, or state a non-inferiority or equivalence margin. The registry does not flag a discrepancy, but the available detail is insufficient to understand what conclusion the analysis was intended to support.

The group summaries are small, and some secondary binary measures have few recorded events. Their unadjusted estimates are consequently uncertain. The registry does not report adjustment for multiple testing, an outcome hierarchy, or whether the secondary analyses were prespecified. Results for listed complication and esthetic outcomes are not reported in the registry record.

Further limitations include missing information about follow-up completion, missing observations, the analysis population, allocation concealment, the details of masking, and outcome-assessment procedures. The record does not provide participant characteristics beyond the population description or a sample-size justification. These omissions make it difficult to assess risk of bias, generalizability, and whether the reported analyses followed a planned statistical approach. They do not demonstrate that a particular problem occurred, but they constrain interpretation of the registry results.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Plasma of Argon Cleaning on Implant Abutments: 5-year Results of a Randomized Clinical Trial — NCT02552810.
• Registry record last updated 2016-06-17; status last verified 2016-05.
• Results first posted 2016-06-17.
• 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 registry describes a completed, randomized, double-masked, parallel-group trial of plasma of argon versus steam cleaning of implant abutments in patients with a history of periodontal disease and thin biotype. Enrollment is listed as 30. The primary outcome was implant and prosthesis success during five years of follow-up.

Reported primary success was 100.0% in each group, with no observed primary failures in the posted summaries. A simple unadjusted re-calculation gives a risk difference of 0.0 and a confidence interval from 0.0 to 0.0; this does not establish equivalence. The registry also lists a Wilcoxon (Mann-Whitney) analysis with p < 0.05, but does not provide the details needed to interpret it against the primary outcome or a non-inferiority or equivalence margin.

Some secondary outcome results are reported, while results for other listed outcomes and important details about missing data, analysis populations, multiplicity, and sample-size justification are not reported in the registry record.