Condition category
Oral Health
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims
The treatment of patients with a reduced number of teeth is an important part of daily practice. There are several treatment options. Double-crown-retained dentures (DCRDs) have a natural appearance and as a result, these dentures are very popular. Additionally, most of patients with DCRDs report a high level of chewing comfort due to very high prosthesis retention. DCRDs also permit the inclusion of existing teeth and implants. Studies already shown improvement in oral health and quality of life for patients using DCRDs.
However the manufacturing process of these dentures is not consistent. DCRDs are composed of a primary crown attached in patients mouth and a secondary crown located in the denture. There are different shapes of primary crowns, including conical and cylindrical. Prosthesis retention is provided by the friction between the primary crown (patients mouth) and secondary crowns (denture). However, a need for friction adjustments or even a loss of retention has often been described. As a result, patients can have problems handling these dentures. The Weigl protocol describes a manufacturing process for these dentures using an all-ceramic primary crown and an electroplated secondary crown, which helps to reduce changes in retention during the lifetime of the denture. The aim of this study is to verify the survival rates, complications and maintenance needs of DCRDs manufactured according to the Weigl protocol.

Who can participate?
Anyone who received DCRDs according to the Weigl protocol at the Department of Prosthodontics of the University of Frankfurt am Main, Germany between June 1998 and December 2013

What does the study involve?
There is no direct involvement of participants in this study, as their patient sheets are used for assessment of survival rates, complications and maintenance needs.

What are the benefits and risks of participating?
There are no direct benefits or risks of participating in this study as it does not require direct participant involvement. The results of this study may benefit future patients requiring DCRDs as it may improve success rates and reduce the number of complications.

Where is the study run from?
ZZMK (Carolinum), Goethe University Frankfurt (Germany)

When is the study starting and how long is it expected to run for?
January 2013 to June 2017

Who is funding the study?

Who is the main contact?
Dr. Silvia Brandt

Trial website

Contact information



Primary contact

Dr Silvia Brandt


Contact details

Theodor-Stern-Kai 7

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Long-term clinical success of conical electroplated double-crown-retained dentures on implants or natural abutments up to 11.5 years: a retrospective study


Study hypothesis

Dentures created with the conical electroplating concept is an alternative to other approaches, especially for combined tooth/implant-supported dentures.

Ethics approval

Ethics Committee of University Frankfurt, 13/05/2013, reference 177/13

Study design

Observational retrospective cohort study

Primary study design


Secondary study design

Cohort study

Trial setting


Trial type


Patient information sheet

Not available in web format, please use contact details to request a participant information sheet


Reduced dentition in upper and lower jaw


For data collection, the sheets of patients who received double-crown-retained dentures (DCRDs) between June 1998 and December 2013 were evaluated for failure of DCRDs, necessary repairs, pressure source, occlusal adjustments, problems with denture removal, relining needs and maintenance needs related to the denture abutments.

Intervention type



Drug names

Primary outcome measure

Failure of DCRDs (defined as the loss of the denture), evaluated by reviewing patient notes

Secondary outcome measures

The following were evaluated by reviewing patient notes from patients between June 2013 and December 2013:
1. Necessary repairs to dentures
2. Pressure source
3. Occlusal adjustments
4. Problems with denture removal
5. Relining needs
6. Maintenance needs related to the denture abutments

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Dentures fabricated according to the Weigl protocol
2. Regular ttendance of follow-up exams
3. Tooth-supported DCRDs
4. Implant-supported DCRDs
5. Combined tooth/implant-supported DCRDs
6. Conical implant/abutment connections
7. Aged 18-91 years

Participant type


Age group




Target number of participants


Participant exclusion criteria

Not treated according to the Weigl protocol

Recruitment start date


Recruitment end date



Countries of recruitment


Trial participating centre

ZZMK (Carolinum) , Goethe University Frankfurt
Theodor-Stern-Kai 7
Frankfurtam Main

Sponsor information


Goethte University Frankfurt

Sponsor details

Theodor-Stern-Kai 7

Sponsor type




Funder type


Funder name

Investigator initiated and funded

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Planned publication in Clinical Implant Dentistry and Related Research

IPD sharing statement:
The datasets generated during and/or analysed during the current study are not expected to be made available due to data protection regulations

Intention to publish date


Participant level data

Not expected to be available

Basic results (scientific)

A total of 126 conical electroplated DCRDs on 603 abutments in 111 patients were examined over a maximum period of 11.5 years (mean observation period: 45.25 ± 25.11 months; Table 1). The patients’ mean age was 65.58 ± 10.47 years. There were 61 male and 50 female patients.
Of the 81 repairs, reattaching or replacing a denture tooth was required for 18 dentures, making this the most common occurrence. In addition, loosening and reconditioning of the primary crown became necessary in nine cases, followed by veneer repairs (3 cases), crack repairs (2 cases), and remakes of primary and secondary crowns (1 cases each). In addition, there were 14 cases of abutment loss owed, among other causes, to caries, tooth fractures, or endodontic problems.
The mean survival time of the dentures considered was 118.09 ± 8.84 months, namely 96.08 ± 13.86 for maxillary and 134.81 ± 4.22 months for mandibular dentures. The log-rank test returned a significant result of p = 0.027. The survival rate at 5 years according to Kaplan-Meier was 92.9 ± 0.05% in the maxilla and 100% in the mandible. The survival rate of all dentures observed was 98.9 ± 1.1% at 4 years, 96.9 ± 2.2% at 5 years, and 82.5 ± 8.6% at 7 years. At 8 years, the survival rate was 66 ± 16.3% and remained stable until the end of the observation period at 139 months.

Publication list

Publication citations

Additional files

Editorial Notes

23/11/2018: Internal review.