This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Lithium Disilicate (CAD/CAM) Fixed Partial Dentures (FPD) Clinical Study (NCT03036566), a na na study. The primary outcome is Bridge Failure.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03036566 |
| Phase | NA |
| Condition | Missing Tooth |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 30 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Michigan |
| Results posted | Yes |
2. Clinical Question
The study asks whether three-unit lithium disilicate ceramic bridges made with chairside computer-assisted design and machining remain in place and intact after delivery. The primary outcome is bridge failure, defined in the registry record as fracture or loss of the bridge requiring placement of a new bridge. The stated observation period runs from bridge delivery up to 5 years.
Population
People with a missing tooth who receive a bridge intended to replace a single tooth. The registry record lists an enrollment of 30, but does not report further eligibility criteria or characteristics of the participants who received bridges.
Intervention
A three-unit, high-strength lithium disilicate ceramic bridge, described as emaxCAD by Ivoclar, fabricated with a computer-assisted technique and cemented with adhesive resin cement. The registry record describes the material as approved by the FDA for patient treatment.
Comparator
There is no separate comparator group. The study is recorded as a single-group investigation, with no allocation to different treatments.
Primary question
How many bridges fail through fracture or loss requiring a replacement bridge during follow-up from delivery up to 5 years? The registry record does not contain a posted primary-outcome estimate or analysis.
This is therefore a descriptive question about outcomes among bridges receiving the study procedure, not a randomized estimate of how the procedure compares with another approach. Without a concurrent comparator, the study cannot separate outcomes associated with the bridge from outcomes that might also occur under other care. The registry record identifies additional outcomes concerning loss of retention, tooth sensitivity, and margin staining, but does not provide their results.
3. Trial Design
The registry record describes a single-group clinical study of lithium disilicate ceramic fixed partial dentures. Its listed enrollment is 30. Allocation is recorded as not applicable, and masking is listed as none. The record does not describe a randomized or controlled comparison; the bridge group is the only described group. As a result, the design can describe what happened among participants receiving the bridges, but it does not provide a like-for-like control comparison.
The study began in 2014-03, with primary completion recorded as 2020-03-05. Its current status is listed as terminated. The reason for termination, the timing of termination relative to participant follow-up, and the number of participants who completed follow-up are not reported in the registry record. The planned clinical evaluations are described at 6 months, 1 year, 2 years, and 3 years, with later evaluations at 4 years and 5 years conditional on funding. The record does not establish which of those visits occurred or how complete follow-up was.
The intervention is described as a three-unit lithium disilicate bridge replacing a single tooth. The registry summary says that the bridges would be cemented using adhesive resin cement. These design details describe the intended procedure, but the registry record does not report whether every enrolled participant received the bridge as planned or whether procedures varied.
The record lists one primary outcome and three secondary outcomes, and identifies four outcome measures overall. It lists no analysis records. A statistical analysis plan, protocol deviations, sample-size justification, interim analyses, and the reason for choosing the enrollment target are not reported in the registry record. The study's status and dates alone do not reveal whether the stated follow-up schedule was completed or whether the study stopped early for a particular reason.
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
| Stage | Bridge |
|---|---|
| STARTED | 30 |
| COMPLETED | 27 |
| NOT COMPLETED | 3 |
Reasons for not completing this period:
| Reason | Bridge |
|---|---|
| Lost to Follow-up | 3 |
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.
| Characteristic | Unit | Bridge |
|---|---|---|
| Participants analysed | 30 | |
| Age, Customized | Participants | 0 |
| Sex: Female, Male: Female | Participants | 19 |
| Sex: Female, Male: Male | Participants | 11 |
| Race and Ethnicity Not Collected | Participants | — |
6. Primary Endpoint
The registry lists the primary outcome as Bridge Failure, measured over from delivery of the bridge up to 5 years.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | number of bridges |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is bridge failure, counted as the number of bridges that fracture or are lost and require placement of a new bridge at any time from delivery up to 5 years. This definition focuses on a clinically consequential failure of the prosthesis rather than every change in appearance or every maintenance event. It combines two routes to failure—fracture and loss requiring replacement—into one outcome. The registry record does not specify how these routes would be separately summarized or adjudicated.
A count endpoint is useful when the question concerns how many devices experience a defined event during a stated follow-up period. It gives a direct description of the burden of failures in the study group, provided the number of bridges observed and follow-up completeness are also understood. Counts alone do not show when events occurred, whether participants contributed different lengths of observation, or how the risk compares with another treatment.
The timeframe is from bridge delivery up to 5 years. The registry record does not contain a posted count of failures, a denominator for the primary-outcome analysis, or an estimate with uncertainty. Thus, the endpoint's definition and planned timeframe can be described, but the observed performance of the bridges cannot be quantified from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The study is registered as a single-group evaluation of lithium disilicate bridges, with an enrollment of 30 and a primary endpoint of bridge failure. The endpoint is defined as fracture or loss requiring placement of a new bridge, assessed from delivery up to 5 years. These details establish what the study intended to examine. They do not establish how many bridges failed: the registry record contains no posted primary-outcome result and lists no analysis records.
That distinction matters because an endpoint definition is not an outcome estimate. To interpret the clinical performance observed in the study, a reader would need the number of failures, the number of bridges actually followed, the duration and completeness of follow-up, and a clear description of how failures were identified. Those details are not reported in the registry record. The planned visit schedule includes assessments through 3 years, with 4-year and 5-year evaluations conditional on funding, but the record does not say which assessments took place.
Even if a count of failures were available, a single-group count would describe outcomes in this study group rather than establish a comparative effect. There is no separate control group, and the record does not describe random allocation. Without a comparator, differences from another approach cannot be estimated from this design. In addition, a count without follow-up information may be difficult to interpret: participants or bridges observed for different lengths of time have different opportunities to experience a failure.
The registry lists secondary outcomes concerning loss of retention, tooth sensitivity, and margin staining, but results for those outcomes are not reported in the registry record. It also lists adverse-event figures for the Bridge group: 30 at risk and 0 affected for serious adverse events, 30 at risk and 0 affected for other adverse events, and 0 deaths. These are counts as recorded, not a complete account of how events were collected or whether follow-up was complete. The absence of recorded affected participants should not be read as proof that no events occurred outside the recorded data.
There are no analysis records in the registry. The statistical methods actually used, treatment of incomplete observations, and any uncertainty intervals or hypothesis tests are not reported. Accordingly, the registry supports a description of the intended study question, design, and recorded adverse-event counts, but not a conclusion about the magnitude or precision of the primary outcome.
9. Statistical Methods Explained
The registry record identifies bridge failure as a count outcome. A count records how many defined events occurred, rather than the time until the first event or a continuous measurement such as a score. Here the event definition combines fracture and loss requiring a replacement bridge. The count could be presented for the study group, but interpretation would depend on knowing how many bridges were actually assessed and over what periods. Those primary-outcome results are not reported in the registry record.
What does a count describe?
In general, a count is a direct summary of the number of events observed in a specified group. It does not, by itself, indicate the chance of an event for an individual bridge, especially when follow-up differs between bridges. A count also does not communicate the timing of events. For example, an event recorded shortly after delivery and one recorded much later both contribute to a total count, although their timing may matter to clinical interpretation. The registry record defines a follow-up window from delivery up to 5 years but does not report event times or the number of bridges with complete observation.
In general, statistical methods for counts may account for the amount of observation or for variation in event rates between individuals. Whether such methods are appropriate depends on the design and the data. Some count models assume that events vary around a common average in a particular way. Over-dispersion occurs when the observed variability in counts is greater than such a model assumes. If that is present and not addressed, standard errors and confidence intervals can be too small, making estimates appear more precise than warranted. This is a general consideration, not a description of an analysis reported for this study: the registry record lists no analysis records and does not report a count model or its assumptions.
Why does follow-up matter?
General interpretation of event counts requires attention to observation time. A bridge followed through the entire planned period has more time in which a failure can be observed than a bridge followed for a shorter period. A simple total count does not adjust for that difference. Time-to-event methods can incorporate event timing and censoring, where censoring means that observation ends before an event is recorded. Those methods require appropriate information about event and follow-up times. The registry record does not report such data or say that a time-to-event analysis was planned or used.
Confidence intervals are a general way to express uncertainty around an estimate. They indicate a range of values compatible with the data under a specified method and its assumptions; they do not guarantee that the true value lies within the interval or resolve bias from incomplete follow-up or lack of a comparator. No confidence interval for bridge failure is reported in the registry record. A p-value, when used, addresses compatibility of data with a specified statistical hypothesis under a chosen model; it is not a measure of clinical importance or proof that a treatment caused an outcome. No primary-outcome p-value or hypothesis test is reported.
How should planning illustrations be read?
General sample-size calculations depend on assumptions about the design, outcome, variability, effect to detect, significance level, and desired power. The planning assumptions associated with this study describe a hypothetical two-arm calculation with equal allocation, a two-sided significance level of 0.05, and a normal approximation. Those assumptions do not match the registered single-group design. The illustrations are planning exercises based on a stated fraction of an observed effect; they are not the trial's design, observed power, or evidence that the study had a particular probability of detecting an effect. No sample-size justification for the actual study is reported in the registry record.
In general, power is the probability that a specified test will detect an effect of a particular size under its assumptions. It is not a property that can be inferred from a result after the fact by treating the observed effect as fixed. Planning illustrations can show how assumptions affect required sample sizes, but they do not add outcome evidence. The registry enrollment of 30 is a design-record figure; it should not be conflated with the number included in an analysis, which is not reported.
Finally, statistical estimates describe the data available to the analysis, not necessarily every participant initially enrolled. Analysis populations can differ depending on whether they include all enrolled participants, only those who received the procedure, or only those with complete follow-up. The registry record does not specify an analysis population for bridge failure. Without that information, together with the missing outcome and follow-up details, no estimate or precision assessment can be reconstructed from the registered design alone.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists a primary outcome of bridge failure and secondary outcomes concerning loss of retention, tooth sensitivity, and margin staining. Considering several outcomes can raise a multiplicity issue: when many statistical tests are performed, the chance of at least one apparently notable result can increase. General approaches include prespecifying a primary outcome, adjusting for multiple tests, or treating secondary analyses as exploratory. The registry record does not report whether any adjustment, testing hierarchy, or other multiplicity strategy was planned or used. It also contains no analysis records, so it is not possible to determine how many tests were conducted.
Missing data can affect both the estimated outcome and its uncertainty. Relevant information would include how many participants received bridges, how many contributed primary-outcome data, when follow-up ended, and why any observations were unavailable. The registry record does not report a missing-data approach, follow-up completeness, or the number included in the primary analysis. The planned evaluations at 6 months, 1 year, 2 years, and 3 years, with later visits conditional on funding, do not show which observations were ultimately collected.
Analysis populations can also differ. A study might define analyses based on enrollment, receipt of the intervention, or availability of outcome measurements. The registry record does not identify the population used for primary or secondary analyses. These omissions prevent assessment of whether incomplete follow-up or exclusions could affect the reported findings. Since no outcome analyses are listed, no conclusions about multiplicity handling, missingness, or analysis-population choices can be drawn.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Bridge | 0 | 30 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Bridge | 0 of 30 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Bridge | 0 of 30 |
For the Bridge group, the registry record lists 30 at risk and 0 affected for serious adverse events. It also lists 30 at risk and 0 affected for other adverse events, and records 0 deaths. No serious adverse-event terms are listed. These figures are counts in the registry record; they are not estimates of comparative safety because the study has no separate control group.
A recorded count of zero does not establish that an event was impossible or that every event was captured. Interpretation depends on the period and methods of safety monitoring, definitions used, completeness of reporting, and the number of participants with available follow-up. These details are not reported in the registry record. The recorded at-risk count should not be assumed to represent the number with complete safety follow-up over the entire planned period.
The serious and other adverse-event counts are distinct from the primary endpoint of bridge failure. A bridge failure is defined by fracture or loss requiring replacement; the adverse-event figures do not report the primary endpoint count. The registry record does not provide enough detail to determine overlap between device outcomes and adverse-event categories or to describe event timing. The figures therefore summarize what is recorded in these categories, not the full range of possible safety outcomes.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a single-group study was intended to evaluate three-unit lithium disilicate bridges replacing a single tooth. It defines bridge failure as fracture or loss requiring placement of a new bridge and sets the primary observation period from delivery up to 5 years. It also lists secondary outcomes concerning retention, tooth sensitivity, and margin staining. These are useful details about the study question and the outcomes it planned to track.
The record does not report the primary outcome count, secondary outcome results, or statistical analyses. It therefore does not show how often bridge failure occurred or how precisely that outcome was estimated. The enrollment figure of 30 does not establish how many participants received a bridge, completed follow-up, or contributed to an outcome analysis. The study status is terminated, but the reason and its consequences for follow-up are not reported.
Because there is no separate comparator group, the study cannot estimate how outcomes differ from those under another treatment or care strategy. A single-group description can document outcomes among the observed bridges, but it cannot by itself distinguish effects of the bridge from other influences. Further, the planned long-term evaluations do not show that all participants were observed through the full period.
The adverse-event record lists no affected participants in the reported serious or other categories and records no deaths. These figures should be understood as recorded counts, with safety-monitoring and follow-up details not reported. They do not demonstrate the absence of all possible adverse events.
In general, a registry entry is a record of study design and reporting, not a substitute for outcome data. The available details support understanding what was intended and what categories were recorded, but they do not support a numerical conclusion about bridge performance, comparative benefit, or the precision of an effect estimate.
13. Why This Trial Matters Statistically
This study is statistically notable for the distinction between a clearly defined outcome and an unavailable outcome estimate. Bridge failure has a specific registered definition—fracture or loss requiring replacement—and a stated follow-up window from delivery up to 5 years. That definition helps readers understand what the study intended to count. Without the count, denominator, and follow-up information, however, the statistical question cannot be answered from the registry record.
The single-group design also clarifies the limits of the comparisons that can be made. It can, in principle, describe observed failures among the bridges followed, but it does not create a randomized counterfactual group. Consequently, no comparative treatment effect can be derived from the design as registered. The lack of a comparator is not a statistical defect in every descriptive study; it is a constraint on the kind of inference the study can support.
The registry record also illustrates why enrollment is not interchangeable with an analyzed sample. It lists 30 participants for enrollment, but does not report how many received bridges or contributed outcome data. For an endpoint that may be observed over an extended period, follow-up completeness and event timing are central to interpretation. The planned visit schedule alone does not demonstrate that those observations were collected.
Finally, the planning assumptions use a hypothetical two-arm framework, while the registered study is single-group. Such planning calculations can be educational when kept separate from the actual design and data. They are not evidence of observed power or of an effect in this study. The distinction between study design, planning assumptions, and reported results is essential to avoid giving numerical illustrations more evidentiary weight than they have.
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 most important trial-specific limitation in interpreting the registry record is the absence of posted outcome results. Although bridge failure is defined and follow-up is described as extending up to 5 years, there is no reported failure count or analysis. The registry also lists no analysis records. As a result, the intended endpoint cannot be used to quantify observed performance or uncertainty.
The single-group design has no concurrent comparator, and allocation is listed as not applicable. It cannot directly establish how outcomes compare with another bridge type or care strategy. Masking is recorded as none; the registry does not describe additional procedures for reducing outcome-assessment bias. The reason for termination is not reported, so its relationship to planned follow-up cannot be assessed.
Details needed to assess the primary result are also absent: the number of participants who received bridges, the number included in outcome analyses, follow-up completeness, event timing, and the handling of missing observations are not reported in the registry record. The planned assessments after 3 years were conditional on funding, and the record does not establish whether they occurred. This limits interpretation of the stated long-term timeframe.
The registry lists secondary outcomes, but no results or multiplicity strategy. It does not report a statistical analysis plan, sample-size justification, or interim analyses. These missing details prevent assessment of whether the registered outcomes and methods were implemented as intended. The adverse-event counts are available, but their collection period and monitoring procedures are not described, limiting what can be inferred from the zero affected counts.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Lithium Disilicate (CAD/CAM) Fixed Partial Dentures (FPD) Clinical Study — NCT03036566.
- Registry record last updated 2024-07-25; status last verified 2024-07.
- Results first posted 2023-04-05.
- 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.
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18. Record Summary
The registry record describes a single-group study of three-unit lithium disilicate ceramic bridges for replacement of a single missing tooth. Enrollment is listed as 30; allocation is not applicable, and masking is listed as none. The primary outcome is bridge failure, defined as fracture or loss requiring a replacement bridge, from delivery up to 5 years.
The study began in 2014-03, reached primary completion on 2020-03-05, and is listed as terminated. The reason for termination is not reported in the registry record. Planned evaluations include 6 months, 1 year, 2 years, and 3 years, with later assessments conditional on funding.
Secondary outcomes concern loss of retention, tooth sensitivity, and margin staining. The registry record lists 0 serious adverse events, 0 other adverse events, and 0 deaths among the recorded Bridge group counts. It contains no analysis records and does not report primary or secondary outcome results, missing-data handling, analysis populations, or the statistical analysis plan.