NCCL Direct Composite Restoration Performance With Self-Etch and Multimode Adhesives: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for NCCL Direct Composite Restoration Performance With Self-Etch and Multimode Adhesives (NCT02698371), a randomized na study. The primary outcome is Esthetic, Functional and Biological Clinical Performance Adhesive/Adhesion Mode of NCCLs Restoration, Graded on a 5-point Scale, Using FDI Criteria at 24 Month Follow-up Recall.

2. Clinical Question

3. Trial Design

This was a randomized, triple-masked, factorial trial listed as completed. The registry records an enrollment of 38 and gives the condition as dental adhesives/restorations performance. The start is recorded as 2015-11, and primary completion as 2018-05. The stated clinical follow-up for the primary endpoint was 24 months. The record does not describe how masking was implemented or identify which trial roles were masked.

Six treatment arms are named. FBDC was applied in self-etch mode, either without the listed enamel pre-etching condition or with enamel pre-etching. FBU and ADU each had etch-and-rinse and self-etch arms. The record also describes procedure details, including phosphoric-acid etching in the enamel-pre-etching and etch-and-rinse approaches. These arm descriptions establish the strategies listed for comparison, but do not explain the factorial structure in detail or specify the primary contrasts.

The primary assessment used FDI criteria and counted NCCL restorations in performance categories. The primary population is described as per protocol, involving participants completing the study and restorations observed at the 24-month recall. The record says each participant could be enrolled in several arms and receive 1 to 6 restorations. This makes clear that the restoration-level endpoint should not automatically be interpreted as a participant-level outcome.

The registry lists 19 outcome measures and 69 analyses. It does not report the randomization procedure, allocation concealment, masking details, or the intended handling of dependence among multiple restorations from a participant. A detailed protocol, statistical analysis plan, and sample-size justification 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: 54 participants were screened. Of those, 38 participants met inclusion criteria and were enrolled.

All Participants Flow

Reasons for not completing this period:

FBDC-SE (G1; Control) Arm/Group Flow

Reasons for not completing this period:

FBDC-SE-EE (G2; Control ) Arm/Group Flow

Reasons for not completing this period:

FBU-ER (G3) Arm/Group Flow

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Per protocol analysis Population, defined as participants completing (each one enrolled in several arms and received 1 to 6 restorations), and NCCLs restorations observed, using FDI criteria, at 24 month recall.

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: Each participant is enrolled in several Arms/Groups and received 1 to 6 NCCLs restorations; The allocation of the arm/group (G1, G2, G3, G4, G5, G6) to each NCCLs of each participant was performed ensuring that the distribution of the arms/groups was not repeated in the same participant.

6. Primary Endpoint

The registry lists the primary outcome as Esthetic, Functional and Biological Clinical Performance Adhesive/Adhesion Mode of NCCLs Restoration, Graded on a 5-point Scale, Using FDI Criteria at 24 Month Follow-up Recall, measured over 24 months.

The primary endpoint is the number of NCCL restorations rated for esthetic, functional, and biological clinical performance at the 24-month follow-up. Ratings use a five-point FDI scale. The record defines scores 1 through 4 as performance ranging from clinically excellent or very good to clinically sufficient or satisfactory; score 5 means clinically poor, with replacement necessary. The endpoint is expressed as a count of restorations in the described performance categories, not as a participant-level measure.

A clinical rating scale allows several aspects of restoration performance to be assessed in a structured way. The endpoint brings esthetic, functional, and biological properties into the trial’s stated assessment, while retaining ordered categories that distinguish stronger ratings from poor performance. An ordered scale is not automatically an equal-interval measurement: the distance between adjacent categories need not represent the same change in clinical status. Counts by category therefore retain information that would be lost by treating the score as an ordinary continuous measure without justification.

The registry states that restorations not observed because retention or marginal integrity was lost were marked missing for other categories. That distinction matters: a missing rating is not itself a rating of poor performance, although the reason for missingness may be clinically relevant. The record does not give category counts, denominators, estimates, or uncertainty for the primary endpoint. Consequently, the outcome description alone does not show how ratings were distributed across the six arms.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the study as randomized, triple-masked, and factorial, but it does not report a detailed analysis plan. The following statistical concepts explain how trial design and outcome structure affect interpretation; they are general explanations, not claims about methods used in this trial unless explicitly stated in the registry record.

What does randomization contribute?

In general, randomization assigns treatment strategies by chance to reduce systematic differences between groups at the start of a trial. It supports a fair comparison when allocation is implemented as planned and outcomes are analyzed in a way that preserves the randomized comparison. A label of randomized does not, on its own, establish how the allocation sequence was generated, whether allocation was concealed, or whether all participants were analyzed according to assignment. Those details are not reported in the registry record.

The six listed arms represent distinct adhesive and application strategies: two FBDC conditions, two FBU modes, and two ADU modes. The factorial label ordinarily refers to studying multiple treatment factors within one design, which can support assessment of effects associated with those factors and potentially their interaction. However, the record does not define the factors, state which interaction was planned, or explain how the six arms map to a particular factorial model. It is not appropriate to infer a specific factor-effect estimate from the label alone.

Why does the unit of analysis matter?

The endpoint counts restorations, but participants could receive restorations in multiple arms. In general, multiple observations from one participant can share characteristics and be correlated. Treating correlated observations as independent may make standard errors too small and confidence intervals too narrow. Cluster-aware approaches can account for within-participant dependence, for example through a model with participant-level effects or a method that adjusts uncertainty for clustering. The registry does not report whether any such approach was used, nor whether the analysis unit was a restoration, a participant, or both.

The distinction between the unit of randomization and the unit of outcome measurement is also important. If treatment is assigned at one level but outcomes are recorded at another, analysis must respect how observations were generated. The record identifies randomized arms and restoration-level outcome counts, but does not provide enough detail to establish the exact assignment and analysis structure.

How should the FDI scale be understood?

The five-point FDI scale is ordered: lower scores in the stated description correspond to better clinical ratings, while score 5 is clinically poor. An ordinal scale gives the ranking of categories but does not guarantee equal spacing between them. General methods include reporting the count in each category, comparing a prespecified combined category, or fitting an ordinal model. Each approach has a different interpretation and assumptions. The registry record describes categories 1 through 4 as acceptable and category 5 as poor, but does not report which statistical summary or model was used for the primary analysis.

The endpoint’s stated unit is NCCL restorations. A count alone needs a denominator for interpretation. For example, the same count can represent different levels of performance if the numbers of restorations assessed differ. The registry does not report the primary endpoint denominators or category counts, so neither an absolute rate nor a comparison of rates can be recovered from the outcome definition.

What does a confidence interval add?

In general, an effect estimate describes the observed contrast according to a chosen measure, while a confidence interval conveys its statistical uncertainty. The interval depends on the data, the analysis model, and assumptions such as independence or an appropriate treatment of clustering. It is not a guarantee that the true effect lies within the interval. Here, no primary endpoint effect estimate or confidence interval is reported in the registry record, so precision cannot be assessed.

A p-value, when reported, measures how compatible data are with a specified null model under the test’s assumptions. It does not give the probability that the null hypothesis is true, nor does it measure clinical importance. A p-value should be interpreted alongside the effect estimate, its uncertainty, outcome definitions, and analysis choices. The registry record does not report a primary endpoint p-value.

What do the planning assumptions mean?

The registry describes planning illustrations based on a fraction of an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It distinguishes participants per arm for non-time-to-event outcomes from total events for time-to-event outcomes. Such illustrations are not the trial’s original sample-size justification and should not be read as observed power. The particular effect fractions and calculated planning values are not reported in the registry record. A sample-size illustration also cannot replace an analysis of the observed outcomes or show whether the actual estimates are precise.

The record does not report the statistical model, variance assumptions, missing-data method, multiplicity strategy, interim analyses, or analysis populations beyond the per-protocol description for the primary endpoint. These details are needed to evaluate the validity and reproducibility of an inferential analysis. General statistical principles can explain why they matter, but cannot establish what procedures were followed in this study.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 19 outcome measures and 69 analyses. Multiple outcomes, arms, time points, or statistical contrasts can create multiplicity: as the number of tests increases, the chance of at least one apparently unusual result can rise when all null hypotheses are true. General approaches include adjustment of significance thresholds, a prespecified testing hierarchy, or clear labeling of analyses as exploratory. These strategies involve choices about error control and the scientific questions being tested. No multiplicity adjustment or testing hierarchy is reported in the registry record.

The registry’s primary outcome description defines a per-protocol population of participants completing the study and restorations observed at 24-month recall. It also says restorations not observed because retention or marginal integrity was lost were scored as missing for other categories. That is a specific outcome-coding rule, but the record does not explain how missing primary endpoint observations were handled in analysis, how many were missing, or whether missingness differed among arms. The participant-level completion count and restoration-level denominators are not reported in the registry record.

Missing observations can affect estimates when their occurrence is related to treatment or outcome status. General methods may use assumptions about the missingness process, and sensitivity analyses can assess whether conclusions depend on those assumptions. The registry record does not report an imputation method, a missing-data model, or sensitivity analyses. Nor does it provide enough information to determine how the per-protocol population relates to all randomized participants.

The record names a per-protocol primary population but does not report whether an intention-to-treat analysis was also conducted. Such populations answer different questions, and exclusions after randomization can affect comparability. The analysis population and handling of missing observations should therefore be considered when interpreting any outcome estimates; those results and details are not reported in the registry 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 0% reporting threshold.

The registry lists serious adverse events and other adverse events separately for each of the six arms. For every arm, 35 are listed at risk for serious adverse events and 35 at risk for other adverse events. The recorded numbers affected are 0 for serious events and 0 for other events in each arm, and deaths are recorded as 0 in each arm. These are the posted figures for the listed groups.

Zero recorded events does not establish that an intervention is free of risk. It means no events of the specified kinds were counted in these entries. Interpretation depends on how events were defined, collected, monitored, and attributed, as well as the duration and completeness of observation. Detailed event definitions, collection procedures, and follow-up completeness are not reported in the registry record.

The adverse-event entries should not be treated as evidence about clinical performance. They are distinct from the primary restoration-rating endpoint, and the registry does not report a statistical comparison of adverse-event rates. The at-risk figures also should not be assumed to represent the primary endpoint population: the primary population is described per protocol, and its outcome denominators are not reported. The posted zero counts are descriptive registry data, not proof of equivalent safety across arms.

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

The registry record establishes that a randomized, triple-masked factorial trial was conducted to compare adhesive strategies for NCCL restorations, with a stated clinical assessment at 24 months. It defines a primary restoration-level endpoint using FDI clinical-performance categories and describes a per-protocol population. It also lists secondary measures covering properties such as surface luster, staining margin, color stability and translucency, fractures and retention, marginal adaptation, postoperative hypersensitivity and tooth vitality, recurrence of caries, erosion or abfraction, and tooth integrity.

Those definitions explain what the investigators intended to assess, but they do not reveal how the restorations performed. Primary category counts, arm-specific denominators, estimates of between-arm differences, confidence intervals, and primary test results are not reported in the registry record. The record therefore does not support a conclusion that one adhesive or application strategy had better or worse clinical performance than another. It also does not establish that the strategies were equivalent: an absence of a reported difference is not evidence that a meaningful difference was ruled out.

Likewise, the zero adverse-event counts recorded for each arm do not establish that risks are absent or identical. They describe the posted event counts, while the outcome methods and completeness of event collection are not reported. Safety counts and restoration-performance ratings address different questions and should be interpreted separately.

In general, deciding whether an observed difference matters requires the size and precision of the effect, the clinical context, outcome definitions, and the reliability of the analysis. A statistically detectable difference is not automatically important to patients or clinicians, and an imprecise estimate may leave substantial uncertainty even when a test is not statistically significant. The registry record does not provide the estimates needed for those judgments. It supports a description of the planned comparison and measurement framework, not a treatment recommendation or a claim of benefit or lack of benefit.

13. Why This Trial Matters Statistically

This study raises several important statistical issues common in clinical research. First, randomization and masking are design features intended to support fair comparisons, but their labels do not provide all the information needed to judge how successfully those safeguards were implemented. Allocation methods and masking details are not reported in the registry record.

Second, the endpoint is measured on restorations while participants may contribute multiple restorations and may receive restorations in several arms. This structure makes the unit of analysis and within-participant dependence central to valid uncertainty estimates. A restoration count cannot automatically be read as a count of independent participants. The registry’s description makes the distinction visible, while the analysis method needed to address it is not reported.

Third, the outcome scale is ordinal and includes a stated clinical distinction between acceptable ratings and a clinically poor rating. The choice to report categories separately, combine categories, or use a model changes the question answered. Clear reporting of category counts and denominators would help readers understand both the distribution and the comparison.

Finally, the registry lists many outcomes and analyses. Transparent specification of primary contrasts, multiplicity handling, missing-data methods, and analysis populations is important when several results may be examined. Those details, along with the primary results, are not reported in the registry record. The record therefore illustrates why complete statistical reporting is necessary: a well-defined trial question is only one part of evaluating evidence; readers also need transparent estimates, uncertainty, denominators, and methods.

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.

The main limitation for interpreting this trial record is that it does not report the primary outcome results. There are no reported arm-specific FDI category counts, denominators, treatment-effect estimates, confidence intervals, or primary test results. Consequently, the clinical-performance comparison cannot be quantified or assessed for precision. The record also does not identify a single primary contrast among the six listed arms.

The participant and restoration structures are not fully described. The primary population is per protocol, participants could receive restorations in several arms, and each participant could receive 1 to 6 restorations. However, the number of restorations assessed, the primary analysis denominators, participant completion details, and methods for accounting for clustering are not reported in the registry record. These gaps limit assessment of the analysis population and the uncertainty attached to any restoration-level comparison.

Important design and analysis details are also absent from the registry record, including the randomization procedure, allocation concealment, masking implementation, statistical model, multiplicity approach, and missing-data method. The record does not provide the protocol or a detailed statistical analysis plan, nor does it report a sample-size justification. The planning illustrations described in the record are not a substitute for the trial’s design rationale.

The secondary outcome list is broad, and the record lists 19 outcome measures and 69 analyses, but does not explain how outcomes were prioritized or how multiple analyses were interpreted. The adverse-event listings contain zero recorded events in each arm, but event definitions and collection details are not reported. These limitations leave substantial uncertainty about both the outcome findings and the methods used to produce them.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: NCCL Direct Composite Restoration Performance With Self-Etch and Multimode Adhesives — NCT02698371.
• Registry record last updated 2019-09-13; status last verified 2019-08.
• Results first posted 2019-09-13.
• 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 registry identifies NCT02698371, titled NCCL Direct Composite Restoration Performance With Self-Etch and Multimode Adhesives. It lists University Fernando Pessoa as sponsor and describes a randomized, triple-masked factorial study with enrollment of 38. The recorded start is 2015-11, primary completion is 2018-05, and status is completed.

Six arms compare FBDC, FBU, and ADU adhesive strategies, including self-etch, etch-and-rinse, and enamel pre-etching conditions. The primary endpoint is a count of restorations graded on a five-point FDI scale at 24 months. The primary population is described as per protocol. Although the registry lists 19 outcome measures and 69 analyses, primary outcome values and a specific comparison result are not reported in the registry record.