Comparison of 2 Different Resin Based Filling Materials in Posterior Teeth - a Multicenter Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of 2 Different Resin Based Filling Materials in Posterior Teeth - a Multicenter Study (NCT01925040), a randomized na study. The primary outcome is Score for Surface Luster.

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel-group clinical investigation comparing Venus Pearl with a control resin-based filling material. The study focused on restoration placement in posterior teeth, in carious teeth or as a replacement for a defective prior restoration. It was conducted at two study centers. The registry lists enrollment as 130 and status as completed, with a start date of 2013-06 and primary completion in 2022-07.

Random assignment is intended to make treatment groups comparable on average, including with respect to characteristics that may influence outcomes. The registry does not report how the random sequence was generated, how assignment was concealed, or whether randomization was stratified by center or another factor. “Single” masking is recorded, but the identity of the masked group—such as participants, clinicians, or outcome assessors—is not reported in the registry record. These details matter when considering possible differences in treatment delivery, expectations, or scoring.

The parallel design means the treatment groups were compared as separate groups rather than as a crossover in which participants receive both materials in sequence. The posted primary outcome is the mean score for surface luster at 2 years. The record lists group sizes of 55.0 for Venus Pearl and 53.0 for the control material for this outcome. These are the reported outcome-group values; the registry does not explain the relationship between these analysis counts and the enrollment figure, or describe the analysis population.

The record lists 15 outcome measures, but no secondary outcome results are posted in the information. It also does not report the trial's original sample-size justification, detailed follow-up procedures, or the planned statistical analysis. The completed status indicates the registry's recorded status, but does not by itself establish how complete follow-up was or how the analysis handled missing outcome data.

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: The total number of patients that started the study was 130. However, each patient was eligible to receive up to four restorations, with either a test or a control material. That means the same patient can have received a restoration/restorations with Venus Pearl as well as with the control resin-based filling material. That is the reason why the sum of the following participants differs from the total patient number 130. The analysis was restoration based.

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.

Population: 90 restorations with each material were placed at T0 (in total 180). 7 days afterwards baseline analysis was performed and not all patients from T0 showed up at baseline. That is why the participant and restoration number between T0 and baseline differs. Each patient was eligible to receive up to 4 restorations, with either test or control material. That means the same patient can have received restoration(s)with VP as well as with control.116 is the absolute patient number at baseline.

6. Primary Endpoint

The registry lists the primary outcome as Score for Surface Luster, measured over 2 years.

The primary endpoint is titled “Score for Surface Luster,” reported as a mean score on a scale, with standard deviation as the measure of spread and a timeframe of 2 years. The registry describes a scoring approach involving aesthetic, functional, and biological aspects. It gives the aesthetic categories as 1, clinically excellent; 2, clinically good; 3, clinically sufficient; 4, clinically unsatisfactory; and 5, clinically poor. Thus, on the stated aesthetic scale, a higher category represents a less favorable clinical rating.

Surface luster is an aesthetic feature of a restoration. A rating can provide a structured way to describe how the restoration appears at follow-up, while the other aspects named in the registry indicate a broader clinical assessment context. The record does not explain whether the posted primary mean covers surface luster alone or a composite of the listed aspects, nor does it provide details of the scoring instrument beyond the categories described. That ambiguity limits how specifically the mean can be interpreted.

Reporting a mean allows a group-level comparison, while the standard deviation describes variability in the recorded scores. Because the stated categories are ordered clinical judgments, treating their mean as a continuous measure assumes that averaging the score is meaningful for the intended comparison. The registry does not report the rationale for that statistical treatment or additional information about assessor training and scoring reliability.

7. Results Posted in the Registry

• Venus Pearl: mean 1.89 versus 1.62 on control; difference 0.27 (95% CI 0.04 to 0.50), standardized effect d = 0.44; z-test p = 0.023.

8. Statistical Interpretation

9. Statistical Methods Explained

The main summaries are group means and standard deviations. A mean is the arithmetic average of the recorded scores in a group. It provides a compact description of the group's central score, but it does not show the full distribution. A standard deviation describes how dispersed scores are around the mean; it is not the uncertainty of the mean itself. The posted means are 1.89 for Venus Pearl and 1.62 for the control resin-based filling material, with standard deviations of 0.6 and 0.63, respectively.

What does the mean difference represent?

The comparison reports a mean difference of 0.27, with Venus Pearl as the higher-mean group. The difference is expressed in the score's units. Since the registry's aesthetic categories run from clinically excellent at 1 to clinically poor at 5, a positive difference in this direction means the mean score was numerically higher for Venus Pearl. The score description does not establish whether every element of the primary endpoint follows that exact categorization, so the endpoint's wording should be kept in mind when interpreting the direction.

A group mean difference is not a statement that every restoration in one group scored worse than every restoration in the other. Individuals' or restorations' scores can overlap between groups even when the group averages differ. The registry does not post category-by-category distributions, so the extent and pattern of any overlap cannot be assessed from the reported mean and standard deviation alone.

How should the confidence interval be understood?

A confidence interval describes the range of values reasonably compatible with the data and the statistical method used, under the method's assumptions. The posted interval for the mean difference has both bounds above zero. This indicates that the interval does not include a zero difference, but it does not show the range of individual scores or guarantee that the true effect lies within the interval in a particular study. The registry does not identify the method used to construct the interval, so its precise assumptions cannot be checked from the record.

What does the p-value say?

The unadjusted p-value is 0.023. In general, a p-value measures how unusual data at least as incompatible with a specified null hypothesis would be if that null hypothesis and the statistical model were true. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of an effect. Since the reported value is unadjusted, it does not account for any multiplicity unless such adjustment is incorporated elsewhere; the registry does not report that it was.

The record does not specify the test used for the primary comparison, whether covariates were included, or whether center was accounted for in the analysis. Therefore, the comparison can be described using the posted estimate and p-value, but additional details about the trial's analysis cannot be inferred.

Why does the score's scale matter?

The endpoint is presented as a mean of a score based on ordered clinical categories. Ordered categories establish rank, but they do not necessarily mean that the distance between each adjacent category is equal. Using a mean treats the score numerically and is often useful as a concise summary, but its interpretation depends on whether those numerical differences are suitable for averaging. The registry does not explain why a mean was selected or report a complementary analysis using the categories directly.

More generally, statistical analysis should reflect the data's measurement scale and structure. If multiple teeth or restorations were assessed for the same participant, observations might be related rather than independent; accounting for such clustering can affect uncertainty. The registry record does not state the unit of analysis or whether repeated or clustered observations were modeled. This is a general statistical consideration, not evidence that clustering occurred or was ignored in this trial.

What information is missing about the analysis?

The registry does not report the original statistical analysis plan, the sample-size justification, the method for handling missing scores, or the analysis population. It also does not identify the masking role, scoring reliability, covariate adjustments, or any interim analyses. Those omissions prevent a full audit of whether the posted comparison followed a prespecified plan. The record lists the primary result and an unadjusted p-value, but does not provide enough methodological detail to reconstruct the analysis.

10. Confidence Intervals and Precision

The reported mean difference is 0.27, and the confidence interval's lower and upper bounds are both above zero. The interval therefore indicates that the posted comparison is not centered on no difference under the reported interval calculation. Its width conveys uncertainty about the group-level mean difference: a narrower interval would indicate more precision than a wider one, conditional on the statistical method and its assumptions. The registry does not name the interval method, so its assumptions cannot be fully evaluated.

Precision is distinct from clinical importance. An interval can locate a mean difference with some statistical precision without establishing whether that difference matters to patients, clinicians, or restoration decisions. The registry does not report a threshold for a clinically important score difference. The scoring description also leaves uncertainty about whether the primary mean refers solely to surface luster or incorporates the aesthetic, functional, and biological aspects it names.

The reported group standard deviations, 0.6 for Venus Pearl and 0.63 for the control material, describe variation in scores, not uncertainty in each group mean. The outcome-group counts are 55.0 and 53.0. The registry does not report missing-data handling, the analysis population, or whether the unit of analysis was a participant, tooth, or restoration. Without those details, the interval's relationship to follow-up completeness and the structure of the observations cannot be assessed.

The unadjusted p-value of 0.023 is another summary of uncertainty under a specified null model; it should not substitute for the interval or for a clinical interpretation. The registry does not report whether other outcomes were considered in a formal multiplicity strategy. Consequently, the precision suggested by the primary interval should be understood as applying to the posted comparison, rather than as a complete account of uncertainty across every outcome or analysis.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations, not counts of participants observed in the trial. They are stated as participants per arm, not total events. The assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is defined as a stated fraction of the observed effect. The trial's own original sample-size assumptions and justification are not reported in the registry record.

For planning at 100% of the observed effect, the illustration gives 82 participants per arm for 80% power and 109 participants per arm for 90% power. For planning at 75% of the observed effect, it gives 145 participants per arm for 80% power and 194 participants per arm for 90% power. For planning at 50% of the observed effect, it gives 326 participants per arm for 80% power and 436 participants per arm for 90% power.

In general, power is the chance that a planned statistical test will detect an effect of the size assumed, if that effect is real and the planning assumptions hold. The 80% and 90% columns therefore describe different target probabilities for a hypothetical study design, not probabilities that this completed trial's result is correct. A design targeting 90% power requires more participants per arm than one targeting 80% power for the same assumed effect in these illustrations. Smaller effects need more participants because they are harder to distinguish from random variation.

These figures are not observed power. They are forward-looking planning illustrations based on the observed effect and stated assumptions, not a reconstruction of the trial's original design. The sample-size curve should be read as the same general relationship between the assumed effect size and the participant requirement, rather than as additional observed trial results.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 0.270; pooled standard deviation σ = 0.615.
2. n = 2 × (1.96 + 0.842)² × 0.615² / 0.270² = 81.4, rounded up to 82 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 <- 0.27                      # observed difference in means
sigma <- 0.614899899814964                     # 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(1925040)
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 = 82 (80% power), 109 (90% power)
 75% of observed effect: n per arm = 145 (80% power), 194 (90% power)
 50% of observed effect: n per arm = 326 (80% power), 436 (90% power)
power.t.test: 82.4 
Simulated power at n = 82 per arm: 0.797 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists 15 outcome measures, while the record contains a primary outcome result and no posted secondary outcome results. The record does not report a multiplicity strategy, such as whether the primary outcome was treated as the sole confirmatory comparison or whether statistical error across multiple outcomes or timepoints was controlled. It is therefore not possible to determine from the registry whether or how the unadjusted p-value should be interpreted within a prespecified family of tests.

Multiplicity matters because examining several outcomes, timepoints, or comparisons can increase the chance of finding at least one apparently unusual result by chance. This is a general statistical concern; it does not establish that the trial performed unreported analyses or that any particular adjustment was required. The registry's listing of outcome measures alone does not reveal which were analyzed, how they were prioritized, or whether any adjustment was made.

Missing-data procedures are not reported in the registry record. The record does not state how many eligible observations lacked a 2-year score, why any score might be missing, or whether the analysis used imputation, complete observations, or another method. The posted outcome counts should not be used to infer attrition or completeness because the record does not explain their relationship to the enrollment figure.

The analysis population is also not reported. It is not clear whether the primary comparison included all randomized participants, only participants with observed scores, or another defined group. The registry does not state how deviations from assigned material or other protocol events were handled. These details affect how closely an analysis reflects the randomized comparison and how representative the analyzed observations may be. They cannot be resolved from the mean, standard deviation, and interval alone.

More generally, confidence in a primary result benefits from a prespecified endpoint and analysis approach, transparent reporting of all outcomes, and clear accounting for missing observations. The registry record does not provide enough information to assess those features fully. This limits the strength of conclusions about robustness, but does not alter the numerical summaries that are posted.

14. 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.

For Venus Pearl, the registry reports 0 serious adverse events among 90 entries recorded as at risk, 0 other adverse events among 90 entries at risk, and 0 deaths. For the control resin-based filling material, it likewise reports 0 serious adverse events among 90 entries at risk, 0 other adverse events among 90 entries at risk, and 0 deaths. No serious adverse-event terms are listed.

These are the registry's posted safety counts. The “at risk” entries should not be assumed to match the primary-outcome group counts or enrollment; the record does not explain the relationship between these safety figures and the outcome analysis. Nor does it report event definitions, ascertainment procedures, the safety observation period, or whether all events were actively collected. The zero counts therefore describe what is posted in these fields, not proof that no adverse events occurred beyond the recorded information.

With no events recorded in these groups, the registry figures do not support a comparative estimate of event frequency or establish that the materials have equivalent safety. The safety information is limited to the counts and categories shown in the record.

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

The posted primary result describes a difference in mean surface-luster score at 2 years: 1.89 for Venus Pearl and 1.62 for the control resin-based filling material. The mean difference is reported as 0.27, with a confidence interval whose bounds are above zero, and an unadjusted p-value of 0.023. On the stated aesthetic scale, larger numbers correspond to poorer clinical categories. The result is therefore a numerical difference in the direction of a higher score for Venus Pearl, not a conclusion that every restoration received a worse rating.

The result does not establish whether the magnitude is clinically important. The registry does not define a threshold for importance, and it does not fully clarify how the named aesthetic, functional, and biological aspects relate to the primary score titled “Score for Surface Luster.” A group mean also cannot show the distribution of individual ratings or how many observations fell in each category.

The unadjusted p-value should not be treated as a probability that either material is better, or as a measure of effect size. The record does not describe the multiplicity plan, the analysis population, missing-data methods, or the statistical model in sufficient detail to assess the primary comparison comprehensively. The interval and p-value are interpretable as posted statistical summaries, but their assumptions and broader analysis context remain incompletely documented.

The result applies to this registered comparison and the 2-year endpoint. It does not establish performance at other follow-up times, on other clinical outcomes, or in populations and settings not described in the record. No secondary outcome results are posted in the information. The safety fields report zero events in the listed categories, but their ascertainment details are not reported, so those counts should not be taken as a complete characterization of safety.

16. Why This Trial Matters Statistically

This trial illustrates how a clinical score can be statistically summarized as a mean difference even when the underlying ratings are ordered categories. The endpoint's scale is important: a larger category number is less favorable on the stated aesthetic scale. Reading the numerical direction without knowing that coding would risk reversing its clinical meaning. At the same time, the registry's description of the score leaves uncertainty about how surface luster relates to the other assessment aspects named in the endpoint.

The result also shows why an estimate, confidence interval, and p-value answer different questions. The mean difference describes the magnitude and direction of the group-average contrast, the interval conveys uncertainty around that contrast under a statistical method, and the p-value summarizes compatibility with a null hypothesis under model assumptions. None alone establishes clinical importance. The record does not provide a clinically important threshold or enough analysis detail to settle broader questions about robustness.

The planning illustration is useful as a demonstration of how assumed effect size and target power influence a hypothetical participant requirement. It must be kept separate from the trial's original design: the registry does not report the original sample-size justification. This distinction prevents planning figures based on the observed effect from being misread as evidence about the trial's design quality or probability of detecting an effect after completion.

Finally, the record exposes common reporting questions in clinical-trial interpretation: who was masked, what population was analyzed, how missing scores were handled, and how multiple outcomes were considered. Those details affect the context in which a posted result should be understood. Their absence does not erase the reported comparison, but it limits how far the statistical interpretation can be extended.

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.

Several trial-specific details needed for a fuller interpretation are not reported in the registry record. The masking designation is single, but the masked party is not identified. The method of random sequence generation, allocation concealment, and any stratification are also not described. The record gives two study centers but does not provide center-specific outcome results or state whether center was included in the analysis.

The primary endpoint is titled “Score for Surface Luster,” yet its description mentions aesthetic, functional, and biological aspects and gives categories for aesthetic properties. The relationship between those elements and the posted score is not fully explained. The record does not describe the scoring instrument beyond the categories, who rated restorations, whether assessors were trained, or whether scoring reliability was assessed. These uncertainties constrain interpretation of what a difference in the mean represents clinically.

The record does not explain whether the unit of analysis was a participant, tooth, or restoration, or whether participants could contribute multiple observations. It provides no detailed analysis population, missing-data approach, or accounting of follow-up completion. Thus, the outcome-group counts cannot be reconciled with enrollment from the registry information alone. The original sample-size rationale and statistical analysis plan are also not reported.

The registry lists 15 outcome measures but no secondary outcome results in the information. It does not report a multiplicity plan, the rationale for selecting the primary endpoint, or whether additional analyses were prespecified. The posted findings are consequently best read as a limited account of the primary score at its stated timeframe, rather than a complete presentation of the trial's methods and outcomes.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Comparison of 2 Different Resin Based Filling Materials in Posterior Teeth - a Multicenter Study — NCT01925040.
• Registry record last updated 2024-10-28; status last verified 2024-10.
• Results first posted 2024-10-28.
• 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 record describes a completed, randomized, single-masked, parallel-group study of Venus Pearl and a control resin-based filling material for restorations in posterior teeth. The study concerned carious teeth or replacement of defective restorations and was conducted at two study centers. Enrollment is listed as 130; the start date is 2013-06 and primary completion is 2022-07.

The primary outcome is the mean surface-luster score at 2 years. The posted means are 1.89 for Venus Pearl and 1.62 for the control material, with a reported mean difference of 0.27, a confidence interval above zero, and an unadjusted p-value of 0.023. The registry lists 15 outcome measures but no secondary outcome results in the information. It does not report the original sample-size justification, analysis population, missing-data methods, or multiplicity plan. Safety fields list zero serious adverse events, zero other adverse events, and zero deaths for each group, with ascertainment details not reported.