Dental Implant Study Comparing Two Types of Metals Used for Dental Implants: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Dental Implant Study Comparing Two Types of Metals Used for Dental Implants (NCT01714024), a non-randomized na study. The primary outcome is Fold Change in Gene Expression Comparing Trabecular Metal to Standard Titanium..

2. Clinical Question

The study also sought to examine whether gene-expression differences varied across the healthy, diabetic, and osteopenic groups. Its stated secondary outcome compares gene-expression fold changes between titanium and trabecular metal at 4 weeks by group. These aims concern molecular measures associated with bone response; they are not, by themselves, measures of implant survival, restored function, or clinical healing. The registry identifies tooth replacement as the condition and describes test cylinders and implant procedures, but the posted outcome information does not give numerical results for the primary or secondary comparisons.

3. Trial Design

NCT01714024 is a completed, non-randomized, unmasked, parallel study sponsored by the University of North Carolina, Chapel Hill. The registry records enrollment of 42. It describes two device interventions: a Zimmer Trabecular Metal Test Cylinder and a Zimmer Titanium Test Cylinder. Because allocation was non-randomized, material comparisons should not be read as randomized treatment effects. The record itself cautions that the arms are not a like-for-like control comparison.

The study enrolled healthy volunteers, diabetic subjects, and osteopenic subjects. Healthy volunteers were described as non-diabetic, without a history of smoking within the past two years, and without a metabolic bone disease diagnosis. Diabetic subjects were required to have Type 2 diabetes mellitus diagnosed by a physician or reflected in medication history, with the condition currently diagnosed and treated with medications and/or insulin. The osteopenic group included people diagnosed with osteoporosis or osteopenia who were under physician care and receiving oral bisphosphonate treatment. These group definitions identify clinically different populations, which matters when interpreting between-group patterns.

The registry summary describes a study lasting at least 11 weeks and involving 6 appointments. Planned activities included health history, examinations, sample collection, radiographs, placement of temporary mini test cylinders in the lower jaw, and implant surgery. The record describes the primary gene-expression assessment at 2 and 4 weeks after placement. It does not report participant-level schedules, adherence, withdrawals, or the number contributing samples at each assessment.

The non-randomized allocation and lack of masking are important design features. The record does not report how the material used for any participant or test site was selected, nor does it explain whether other clinical or procedural differences were controlled. Without those details, measured differences could reflect the materials, group characteristics, or other differences in study conduct. The registry lists status as completed, but completion status alone does not establish that every planned measurement was collected or analyzed.

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 Fold Change in Gene Expression Comparing Trabecular Metal to Standard Titanium., measured over 2 weeks & 4 weeks post placement.

The primary endpoint is titled “Fold Change in Gene Expression Comparing Trabecular Metal to Standard Titanium.” It assesses molecular activity associated with the osteogenic potential of titanium and porous tantalum dental implant cylinders. The described laboratory work used transcriptome analyses at 2 and 4 weeks after placement. The outcome is reported in terms of Average Delta ∆ (Ct), with osteogenic genes considered relative to housekeeping markers.

In this assay description, Ct is inversely related to the amount of amplicon in the reaction: a lower Ct corresponds to a greater amount of amplicon. That relationship helps explain what the laboratory measurement represents, but it does not by itself identify which material has a higher value for a particular gene. Interpretation also depends on the comparison and normalization used, and the registry’s outcome description does not give numerical endpoint results or gene-specific estimates.

Gene-expression measures are used to characterize biological activity, offering information about molecular responses that may be associated with bone formation. They are not interchangeable with a direct clinical outcome. A measured expression difference would not, on its own, establish a difference in bone healing, implant performance, or patient experience. The registry identifies the endpoint and its rationale, but numerical results and their uncertainty are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: it is described using a mean and standard deviation, with Average Delta ∆ (Ct) as the stated unit. A mean gives a measure of the central level of an outcome in a group, while the standard deviation describes how spread out individual measurements are around that mean. They answer different questions. The mean concerns the group’s average measurement; the standard deviation concerns variation among measurements. Neither alone describes the precision of a comparison between groups.

For a comparative question, an estimated difference or contrast is usually more informative than separate group summaries. A confidence interval describes the range of values reasonably compatible with the observed data under the analysis assumptions. Its width conveys precision: a narrower interval indicates greater precision, while a wider interval indicates less precision. A confidence interval can also show whether the data are compatible with materially different effect sizes. The registry record does not report a comparison estimate or confidence interval, so the precision of the material comparison cannot be evaluated.

The endpoint uses Ct measurements and housekeeping markers to characterize gene expression. The registry notes that Ct is inversely related to amplicon quantity, so a lower Ct corresponds to more amplicon in the reaction. Normalization against housekeeping markers is part of interpreting gene-expression measurements; it provides a reference for comparing expression rather than treating a raw measurement as self-explanatory. The record does not report details of the normalization procedure beyond that description, nor does it provide gene-level values. No direction of effect should be inferred solely from the outcome’s name or from the general Ct relationship.

The primary assessment is described at 2 and 4 weeks after placement. Repeated measurements at different times can address whether a pattern is present at one assessment, another assessment, or both. Comparing such measurements requires attention to the relationship between observations from the same participant or sample, where applicable. The registry does not report the detailed statistical model, how repeated observations were handled, or whether the same participants contributed measurements at each time. Those analysis details are not reported in the registry record.

The study also describes transcriptome analyses and a secondary outcome comparing fold changes between titanium and trabecular metal at 4 weeks across healthy, osteopenic, and diabetic groups. This asks whether the material comparison varies by group, rather than only whether there is an overall comparison. In general, subgroup estimates may be less precise than an overall estimate when fewer observations contribute to each subgroup. The group-specific sample sizes and estimates are not reported, so the degree of precision cannot be assessed for this study.

The study is non-randomized. In general, random assignment helps balance measured and unmeasured participant characteristics between comparison groups, on average. Without randomization, differences between groups may reflect factors other than the material under study. Statistical adjustment can sometimes address measured differences, but it cannot guarantee control of unmeasured or poorly measured factors. The registry does not report an adjustment model or a statistical plan, so it is not possible to determine whether or how potential confounding was addressed.

Over-dispersion is a general concern when observed variability exceeds what an assumed statistical model expects. If a model underestimates variability, its standard errors may be too small and its intervals may appear too precise. That concept can matter for outcomes with extra variation, but the registry does not report a fitted model or evidence of over-dispersion for this continuous endpoint. It would therefore be inappropriate to claim that over-dispersion was present or was addressed.

The record describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The assumed effect to detect is described as a stated fraction of the observed effect. Such calculations are planning illustrations: they show how a sample size requirement could depend on the assumed effect and analysis conditions. They are not observed power, do not establish the study’s actual design rationale, and do not substitute for reported estimates and uncertainty. The registry does not report the trial’s own sample-size justification.

The registry lists 0 analyses. It does not report an inferential analysis for the primary or secondary outcomes, an adjustment for covariates, or a method for handling multiple comparisons. Thus, statistical-method descriptions beyond the stated outcome summaries and planning assumptions are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary gene-expression outcome at 2 and 4 weeks and a secondary group-based outcome at 4 weeks. It also describes transcriptome analyses. When an investigation considers multiple genes, assessment times, or participant groups, the number of possible comparisons can become large. In general, testing many comparisons increases the chance that some results may appear notable by chance alone. This is the reason researchers may prespecify a small set of primary comparisons or use methods to account for multiplicity.

The registry record does not report a multiplicity strategy, a hierarchy among gene-level analyses, or whether any adjustment was applied. It also does not report a statistical analysis plan or inferential analysis entries; the record lists 0 analyses. The available description therefore does not establish how the primary and secondary outcomes were treated statistically, or how results from transcriptome analyses would have been interpreted in relation to one another.

Missing-data information is also absent. The registry does not report how many participants contributed to each gene-expression assessment, whether any measurements were unavailable, why data might have been missing, or whether any imputation or other missing-data method was used. The recorded enrollment of 42 does not establish the analyzed sample for any outcome. Without outcome-specific denominators and a description of missingness, readers cannot assess whether the analyzed observations represent all enrolled participants or whether missing data could affect interpretation.

The analysis populations are not reported in the registry record. It is therefore unclear whether analyses were intended to include all enrolled participants, only those with a usable sample, or another defined population. These gaps do not show that data were missing or that multiplicity was mishandled; they mean the registry record does not give the information needed to judge those issues.

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.

Most frequent non-serious adverse event terms

The registry reports serious adverse events separately from other adverse events for the healthy, diabetic, and osteopenic groups. For serious adverse events, the affected count is 0 in each group. The corresponding at-risk counts are 12 for healthy volunteers, 12 for diabetic subjects, and 8 for osteopenic subjects. The registry lists no deaths in any group and no serious adverse-event terms among the top serious terms.

For other adverse events, the affected count is 2 among 12 at risk in the healthy group, 0 among 12 at risk in the diabetic group, and 2 among 8 at risk in the osteopenic group. These are the registry’s reported counts; they should not be combined across groups or treated as rates without a defined denominator and analysis. The record does not identify the other adverse-event terms in the information available for this account, nor does it provide event timing, severity details, or an attribution to either device.

Zero recorded serious events means that none were reported in these group summaries; it does not establish that the risk is absent. The group counts are descriptive safety information, not a randomized comparison of device-related harms. Because allocation was non-randomized and the record does not describe attribution or comparative safety analyses, these figures cannot establish that one material caused more or fewer events than the other.

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

The study addresses a biologically focused question: whether gene-expression measures associated with osteogenic potential differ between trabecular metal and standard titanium after placement, and whether patterns vary among healthy, diabetic, and osteopenic participants. The registry provides the outcome definition, assessment times, and participant-group descriptions. It does not report numerical outcome results, so it does not establish the direction or magnitude of any gene-expression contrast.

That absence matters for interpretation. Without estimates and measures of uncertainty, readers cannot determine whether observed differences were small or large, precise or uncertain, consistent across genes, or similar across the health-status groups. The record does not report confidence intervals or p-values for these outcomes. It therefore does not permit a statistical assessment of evidence for a material difference.

Even if a gene-expression difference were reported elsewhere, it would need to be interpreted as a molecular measurement. The registry’s endpoint description connects Ct values with amplicon amount and uses housekeeping markers as a reference, but gene expression is not the same as a patient-important clinical outcome. A molecular pattern alone would not establish how well an implant performs, whether bone healing is improved, or whether patients experience a meaningful difference.

The study’s non-randomized allocation and lack of masking further limit causal conclusions. The registry cautions that the arms are not a like-for-like control comparison. Differences in participant health, treatment, or procedures may affect outcomes, and the record does not explain how such differences were addressed. The study’s three health-status groups also have distinct eligibility characteristics, so comparisons between groups should not be read as though the groups were interchangeable.

The safety counts are descriptive and should be read in their group context. They do not identify a device-specific causal effect, and zero serious events in the reported summaries does not establish that serious events cannot occur. In short, the registry record documents a completed study and its intended molecular comparisons, but does not provide enough outcome or analysis information to support a conclusion about comparative clinical performance or safety.

13. Why This Trial Matters Statistically

This trial is statistically notable because it combines a material comparison with biological subgroup questions. The primary outcome concerns gene expression at 2 and 4 weeks, while the secondary outcome asks whether fold-change patterns differ among healthy, osteopenic, and diabetic participants. Those are related but distinct questions. An overall material comparison does not answer whether the contrast varies by health group, and group-specific patterns do not automatically establish an overall effect.

The non-randomized design is central to reading any comparison. In a randomized study, allocation is used to reduce systematic differences between groups. Here, the registry records non-randomized allocation and specifically warns that the arms are not a like-for-like control comparison. This makes it important to distinguish a descriptive association from a causal effect. The record does not describe an adjustment strategy that would allow readers to evaluate whether measured differences were considered.

The molecular endpoint also illustrates why outcome definition matters. Average Delta ∆ (Ct) is a laboratory measure tied to Ct and housekeeping markers, with lower Ct corresponding to greater amplicon in the reaction. That assay-level interpretation is not the same as interpreting a clinical outcome. Clear reporting of the measured genes, contrasts, estimates, and uncertainty would be needed to connect the molecular question to a quantitative result.

Finally, the record demonstrates the difference between study completion and statistical reporting. Status is completed and enrollment is recorded as 42, yet numerical gene-expression results and analysis details are not reported in the registry record. Without estimates, uncertainty, analysis populations, and missing-data information, readers cannot judge the strength or precision of the findings. Those reporting details are essential for evaluating what a clinical study contributes, especially when it involves multiple groups and molecular comparisons.

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 record is that numerical primary and secondary outcome results are not reported. The registry describes Average Delta ∆ (Ct), the relevant genes in general terms, and the assessment times, but does not report gene-specific means, standard deviations, contrasts, or uncertainty. The direction and magnitude of any material-related expression difference therefore cannot be determined.

The design was non-randomized and unmasked. The registry itself notes that the arms are not a like-for-like control comparison. It does not explain how the material was assigned, whether potentially influential characteristics were balanced or adjusted for, or how other differences in care and measurement were handled. This prevents assessment of confounding and limits causal interpretation.

The participant groups have different eligibility definitions, including differing health conditions and treatment requirements. The registry records enrollment of 42 but does not provide group-specific enrollment for the gene-expression analyses or outcome-specific denominators. It also does not report whether measurements were missing, whether participants withdrew, or how analysis populations were defined. The status of completed does not resolve these questions.

Transcriptome analyses and group-based comparisons can involve multiple outcomes. The record does not report a multiplicity approach, a detailed statistical analysis plan, or inferential analyses; it lists 0 analyses. The registry also does not report the trial’s own sample-size justification. These missing details constrain evaluation of the reliability, precision, and intended interpretation of any findings.

The safety summaries give group-level event counts but do not provide event descriptions for the other adverse events, timing, or device attribution. As a result, they do not support a comparative causal safety assessment. These limitations concern what the registry record reports; they do not establish that the underlying study did not collect or analyze additional information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Dental Implant Study Comparing Two Types of Metals Used for Dental Implants — NCT01714024.
• Registry record last updated 2017-10-12; status last verified 2016-01.
• Results first posted 2017-07-12.
• 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

NCT01714024 is a completed, non-randomized, unmasked, parallel study sponsored by the University of North Carolina, Chapel Hill. It recorded enrollment of 42 and compared Zimmer trabecular metal and titanium test cylinders in healthy, diabetic, and osteopenic participants. The primary outcome was gene expression associated with osteogenic potential at 2 and 4 weeks, expressed as Average Delta ∆ (Ct). A secondary outcome described group-based fold-change comparisons at 4 weeks.

The registry record does not report numerical gene-expression results, comparison estimates, confidence intervals, p-values, analysis populations, or missing-data methods. It lists 0 analyses. Reported adverse-event summaries show 0 serious adverse events in each group, with other adverse events reported in the healthy and osteopenic groups. Given the non-randomized design and missing outcome analyses, the record supports describing the research question and design, but not a numerical conclusion about comparative gene expression or clinical performance.