Bone Remodeling After Immediate Implant Placement With and Without Bone Grafting: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Bone Remodeling After Immediate Implant Placement With and Without Bone Grafting (NCT02174198), a randomized na study. The primary outcome is Mean Bucco-Lingual Change at 3mm.

2. Clinical Question

3. Trial Design

The registry describes a randomized, double-masked, parallel-group trial sponsored by Columbia University. The listed enrollment was 32, with 16 participants assigned to BioOss Collagen and 16 to no bone graft. The trial status is completed. The record gives a start date of 2014-01 and a primary completion date of 2018-08.

The two groups differed in whether BioOss was placed into the gap between the implant and the labial bone plate. Both groups were described as receiving an immediate crown. The summary says participants would be followed at 3, 6, and 12 months to observe healing. The primary endpoint compares baseline with 12 months.

Randomization and masking are listed, but the sequence-generation procedure, allocation concealment, and practical details of masking are not reported in the registry record. The record does not report its original sample-size justification, its planned statistical model, or the population used for the primary analysis. It also does not give details on adherence to assigned treatment or participant flow through follow-up.

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 Mean Bucco-Lingual Change at 3mm, measured over Baseline and 12 months.

The primary endpoint is mean bucco-lingual change at 3mm, measured in millimeters between baseline and 12 months. It describes horizontal dimensional change based on digital superimposition. The measurement location is 3mm apical to the position of the free gingival margin at baseline.

This endpoint is used to quantify dimensional remodeling around the implant site over follow-up. It focuses on jaw width at a specified location, complementing the registry’s broader interest in changes in gum level and jaw width after immediate implant placement. A negative mean change indicates a reduction in the measured dimension as represented by the endpoint’s signed values.

The endpoint is a continuous measure, so the reported group summaries are means and standard deviations. A group mean describes the average observed change, while the standard deviation describes variation among observations within that group. The registry’s description identifies the measurement procedure and time points, but does not report a threshold for a clinically important difference or explain how such a threshold was chosen.

7. Results Posted in the Registry

• No Bone Graft: mean -1.01 versus -0.84 on control; difference -0.17 (95% CI -0.55 to 0.21), standardized effect d = -0.31; z-test p = 0.385.

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.

Change in Vertical Dimension of Buccal Soft Tissue (Distal Papilla)

• 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:
  • No Bone Graft: mean -1.40 versus -0.40 on control; difference -1.00 (95% CI -1.80 to -0.20), standardized effect d = -0.87; z-test p = 0.014.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for No Bone Graft than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change in Vertical Dimension of Buccal Soft Tissue (Mid-buccal)

• 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:
  • No Bone Graft: mean -1.30 versus -0.90 on control; difference -0.40 (95% CI -1.34 to 0.54), standardized effect d = -0.29; z-test p = 0.405.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between No Bone Graft and the control. The interval gives the range of effects that remain compatible with the data.

Change in Vertical Dimension of Buccal Soft Tissue (Mesial Papilla)

• 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:
  • No Bone Graft: mean -0.90 versus -0.60 on control; difference -0.30 (95% CI -1.20 to 0.60), standardized effect d = -0.23; z-test p = 0.515.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between No Bone Graft and the control. The interval gives the range of effects that remain compatible with the data.

The secondary results show a mixed pattern rather than a consistent set of differences across the reported soft-tissue outcomes. One reported comparison has an unadjusted interval that does not include zero, while the other reported comparisons have intervals that include zero. This variation means that the secondary outcomes do not provide a uniform signal across measurement locations.

That pattern does not overturn the primary result. The primary endpoint is a separate measure of horizontal bucco-lingual change, and its interval includes zero. The secondary measures concern vertical soft-tissue dimensions at different locations. They provide related context about tissue changes, but they are not interchangeable with the primary measure and do not resolve its uncertainty.

Secondary findings should carry less weight than a prespecified primary result, particularly when multiple outcomes are examined. When several outcomes are assessed, the chance of finding at least one apparently unusual result can increase unless the analysis accounts for multiplicity. The registry record does not report a multiplicity adjustment or explain how secondary outcomes were prioritized. The secondary comparisons are unadjusted, so an isolated result should be treated as exploratory rather than as definitive evidence of a broader pattern.

The registry lists additional secondary measures, but the analysis details and any hierarchy among these measures are not reported in the registry record. Interpretation should therefore distinguish the reported secondary comparisons from a comprehensive conclusion about every listed outcome. Taken together, the secondary results add context but do not provide a consistent basis for a firm conclusion about the primary endpoint or the overall effect of grafting.

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

• Change in Vertical Dimension of Buccal Soft Tissue (Distal Papilla)
• Change in Vertical Dimension of Buccal Soft Tissue (Mid-buccal)
• Change in Vertical Dimension of Buccal Soft Tissue (Mesial Papilla)
• Periodontal Probing Depth
• Thickness of Keratinized Tissue at 3mm
• Thickness of Keratinized Tissue at 4mm
• Thickness of Keratinized Tissue at 8mm

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: it is a measurement in millimeters summarized by a mean and standard deviation for each group. A mean gives the group’s average measured change. The standard deviation describes how dispersed individual measurements are around that average. These quantities answer different questions: the mean describes the central group result, while the standard deviation describes variation among participants.

What does the mean difference represent?

The posted comparison is the no-bone-graft group’s mean minus the BioOss Collagen group’s mean. Its estimate is -0.17mm. A negative value means that the no-graft group’s mean change was more negative than the BioOss group’s mean change. Because the endpoint records dimensional change, the sign matters: a more negative value denotes a greater reduction on this signed scale. The comparison is an unadjusted contrast of group means, not an estimate adjusted for other measured or unmeasured characteristics.

What does a confidence interval convey?

A confidence interval expresses uncertainty around an estimated difference. Rather than treating the observed estimate as exact, it indicates a range of values compatible with the data under the interval’s statistical assumptions. The primary interval spans zero, so the data do not pin down the direction of the underlying group difference. The confidence level and interval-construction method are not reported in the registry record, so the interval should be interpreted as posted rather than attributed to a particular method.

How should the p-value be read?

The unadjusted p-value is 0.385. In general, a p-value describes how unusual a result at least as inconsistent with a specified null hypothesis would be if that hypothesis and the analysis assumptions were true. It is not the probability that the null hypothesis is true, and it is not a measure of the size or clinical importance of the difference. The registry record does not report a formal analysis plan or identify the exact test used for this comparison, so the p-value should not be assigned to an unreported model.

The word “unadjusted” matters because the comparison does not account for the family of outcomes or other covariates. No multiplicity adjustment is reported. The registry lists several secondary measures, making it important not to interpret an individual secondary p-value as if it were the only hypothesis examined. The record does not state whether any outcomes or analyses were prespecified beyond identifying the primary outcome.

Why does variation matter?

Observed measurements can vary among participants even when they receive the same intervention. The standard deviations describe that observed variation, while the standard error of a group mean describes the precision of the estimated mean. General statistical reasoning: more variability makes it harder to estimate a group mean precisely for a given group size. The reported standard deviations are 0.64mm for BioOss Collagen and 0.45mm for no graft on the primary outcome; they are not uncertainty intervals for the group means.

General statistical reasoning: over-dispersion is especially relevant for outcomes whose variability exceeds what a model assumes. The primary outcome is continuous and the registry does not report a count model or evidence of over-dispersion; therefore, over-dispersion is not an identified feature of this analysis. The exact modeling assumptions used for the trial’s own analysis are not reported.

The observed comparison should be distinguished from a causal interpretation. Random allocation is a design feature intended to support fair group comparisons, but the registry record does not provide the randomization procedure, the analysis population, missing-data methods, or details on departures from assigned treatment. Those details would help assess how the analysis preserved the intended randomized comparison. The posted means and comparison remain useful descriptions of the recorded results, but they do not supply those methodological details.

Finally, statistical compatibility with a range of effects is not the same as evidence for every value within that range. A confidence interval represents uncertainty under its assumptions; it does not show that all compatible values are equally likely or clinically consequential. The result is best read alongside the group summaries, the study’s scale, and the limits of the registry’s analysis reporting.

11. Confidence Intervals and Precision

The primary estimate is a mean difference of -0.17mm for no graft compared with BioOss Collagen. Its confidence interval crosses zero, meaning that the posted data do not tightly determine which group had the less negative underlying mean change. Values on both sides of zero remain compatible with the interval. The unadjusted p-value, 0.385, is consistent with this uncertainty, but the interval communicates more than a binary threshold judgment by showing that the estimated contrast is not precise enough to settle its direction.

The group means are -0.84mm and -1.01mm, and the corresponding standard deviations are 0.64mm and 0.45mm. These summaries show that individual measurements varied around the group averages. The interval for the mean difference incorporates uncertainty in the comparison; it should not be confused with the standard deviations, which describe within-group spread.

Precision is limited in part by the size of the randomized groups, which contained 16 participants each. The registry record does not report the confidence level or the method used to construct the interval, so those details cannot be assessed from the record. It also does not identify a clinically important difference. Consequently, the interval can be used to understand statistical uncertainty, but not to decide whether its compatible values would be important in practice.

The key point is not simply that the interval includes zero. It is that the estimate remains compatible with differing directions and magnitudes of effect. The result therefore leaves meaningful uncertainty about the primary contrast.

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 for 80% power and participants per arm for 90% power. They are not total event counts. The planning 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 set to the stated fraction of the observed effect.

For the primary outcome, planning for 100% of the observed effect gives 167 participants per arm for 80% power and 223 participants per arm for 90% power. Planning for 75% of the observed effect gives 296 participants per arm for 80% power and 396 participants per arm for 90% power. Planning for 50% of the observed effect gives 665 participants per arm for 80% power and 891 participants per arm for 90% power.

In plain language, the 80% column gives the estimated number per arm for a design with an 80% chance of detecting the specified effect under the stated assumptions. The 90% column gives the estimated number per arm for a higher chance of detecting that effect, which requires more participants. Smaller effects are harder to distinguish from random variation, so planning to detect a smaller fraction of the observed effect requires more participants per arm.

These are planning illustrations calculated from the observed effect, not observed power. The registry record does not report the original trial’s sample-size assumptions or justification, so these figures should not be read as the study’s original design target.

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 = -0.170; pooled standard deviation σ = 0.553.
2. n = 2 × (1.96 + 0.842)² × 0.553² / -0.170² = 166.2, rounded up to 167 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 <- -0.17                      # observed difference in means
sigma <- 0.553217859436949                     # 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(2174198)
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 = 167 (80% power), 223 (90% power)
 75% of observed effect: n per arm = 296 (80% power), 396 (90% power)
 50% of observed effect: n per arm = 665 (80% power), 891 (90% power)
power.t.test: 167.2 
Simulated power at n = 167 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. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary outcome and lists secondary outcomes involving soft-tissue dimensions and periodontal measurements. However, the registry record does not report a multiplicity plan. It does not say whether the primary outcome was tested at a prespecified significance level, whether secondary outcomes were intended as confirmatory or exploratory, or whether any adjustment was planned for the number of comparisons.

Multiplicity matters because repeated testing can increase the chance that at least one result appears notable by chance. An unadjusted p-value describes an individual comparison without accounting for other tests. This does not make a secondary result invalid, but it means that it should be interpreted cautiously, especially when the result is one among several outcomes. The reported secondary p-values are explicitly unadjusted, and the record does not describe a family-wise or other error-control strategy.

Missing-data methods are also not reported. The registry gives group sizes for the posted outcome summaries, but it does not state whether all randomized participants contributed measurements at the relevant time point, how missing measurements were handled, or whether any imputation or sensitivity analysis was conducted. The follow-up schedule is described in the summary, but follow-up timing alone does not establish completeness of outcome data.

The analysis population is not specified. The record does not say whether results were analyzed according to randomized assignment, according to treatment received, or under another population definition. It also does not report participant flow, protocol deviations, or exclusions from analysis. These omissions limit assessment of how closely the posted comparisons preserve the randomized design and how robust the results might be to missing information or analysis choices.

Interim analyses and stopping rules are not reported in the registry record. Their absence from the record should not be interpreted as proof that none occurred; their status is simply not documented.

15. 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 5% reporting threshold.

The posted serious adverse event figures report zero affected participants in the BioOss Collagen group and zero in the no-bone-graft group. Each group lists 16 participants at risk for serious adverse events. The registry also reports zero participants affected by other adverse events in each group, with 16 at risk in each, and zero deaths in both groups. No serious adverse event terms are listed.

These entries describe the adverse-event information recorded in the registry. They do not establish that no adverse events of any kind occurred, nor do they show that the approaches have identical safety profiles. The registry record does not provide definitions, collection procedures, event-level descriptions, or additional detail about surveillance. With no affected participants recorded in these categories, the figures offer limited information for comparing uncommon harms.

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

The result describes mean dimensional change at a defined location over the period from baseline to 12 months in a randomized comparison of immediate implant placement with and without BioOss Collagen. The group means were both negative, and the posted difference in means was also negative for no graft compared with BioOss Collagen. These values summarize the observed outcome; they do not by themselves establish a cause or determine what a given change means to an individual.

The interval around the primary difference includes zero, and the unadjusted p-value is 0.385. The data do not provide a precise estimate of the direction or size of the underlying difference. That uncertainty does not show that the treatments are equivalent, and it does not establish that one approach is better. The registry record also does not provide a threshold for a clinically important difference, so statistical results cannot be translated into a judgment of clinical importance.

The findings are specific to the enrolled trial population, the procedures described, the measured outcome, and the reported follow-up. They do not answer questions about other implant settings, other grafting materials, different measurement sites, or outcomes not reported. The summary describes an immediate crown and follow-up at 3, 6, and 12 months, but the primary result is for baseline and 12 months. Longer-term results are not reported in the registry record.

Several secondary outcomes provide additional but mixed information, and their unadjusted nature limits the strength of confirmatory interpretation. The safety figures list no affected participants in the recorded adverse-event categories, but the registry’s limited detail does not support broad conclusions about safety. Overall, the posted results are best understood as an imprecise estimate of one primary outcome, not as a final determination about the comparative effects of the two procedures.

17. Why This Trial Matters Statistically

This trial is statistically informative because it illustrates the difference between an observed estimate and a precise conclusion. The group means differ, but the primary interval extends across zero and the unadjusted p-value is 0.385. A point estimate alone can suggest a direction; the interval shows why that direction remains uncertain. Reading both together avoids treating the observed difference as an exact or settled effect.

The study also illustrates why absence of a clearly distinguishable group difference is not the same as evidence of equivalence. A design intended to establish equivalence or noninferiority would require a prespecified margin and an analysis plan suited to that question. Such a margin and plan are not reported in the registry record. The posted result therefore addresses a difference estimate, not a formal equivalence claim.

The sample-size illustrations make the role of effect size visible: planning to detect smaller effects requires larger groups under the stated assumptions. This is useful for understanding the limits of a trial with 16 participants per arm, but those planning figures do not reconstruct the original design rationale, which is not reported.

Finally, the record demonstrates why reporting plans for multiplicity, missing data, and analysis populations matters. Those details help readers judge whether the reported result represents the intended randomized comparison and how much weight to give a secondary finding. The available information supports a careful reading of the estimates, while leaving important questions about the trial’s analysis procedures unresolved.

18. 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 randomized groups contained 16 participants each, so the primary estimate is based on a limited amount of information and has substantial uncertainty. The primary interval includes zero and is compatible with differences in either direction. The record does not report a clinically important threshold, limiting assessment of whether plausible differences would matter clinically.

The primary outcome is focused on bucco-lingual dimensional change at a single specified location and at 12 months. Although the summary describes follow-up at 3, 6, and 12 months, primary results at other time points are not reported in the registry record. The findings therefore do not describe the trajectory of change across follow-up or longer-term outcomes.

The population and procedure are also specific: immediate implant placement in fresh extraction sockets, with an immediate crown and a comparison of BioOss Collagen against no bone graft. The registry record does not report enough eligibility detail to judge how closely other patient groups or clinical settings would match the study population.

Important analysis details are absent, including the original sample-size rationale, statistical model, analysis population, missing-data handling, and multiplicity strategy. Randomization and double masking are listed, but implementation details are not reported. The safety record contains zero affected participants in the listed categories, but event collection and definitions are not described. These limitations do not negate the posted results; they constrain how broadly and confidently they can be interpreted.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Bone Remodeling After Immediate Implant Placement With and Without Bone Grafting — NCT02174198.
• Registry record last updated 2019-06-13; status last verified 2019-05.
• Results first posted 2019-06-13.
• 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.

22. Record Summary

NCT02174198 is a completed randomized, double-masked, parallel-group trial sponsored by Columbia University. It compared BioOss Collagen at immediate implant placement with no bone graft. The listed enrollment was 32, with 16 participants in each group. The record gives a start date of 2014-01 and a primary completion date of 2018-08.

The primary outcome was mean bucco-lingual change at 3mm from baseline to 12 months. The posted mean difference for no graft compared with BioOss Collagen was -0.17mm, with an unadjusted p-value of 0.385 and an interval spanning zero. The result is imprecise and does not establish a clear difference or equivalence. Several secondary outcomes are reported, but their unadjusted findings are mixed. The registry record does not report the original sample-size justification, detailed analysis plan, missing-data methods, or multiplicity strategy.