This trial is active, not recruiting.

Condition implant-supported single crowns
Treatments cemented crowns, screw-retained crowns
Sponsor University of Zurich
Start date June 2012
End date December 2018
Trial size 34 participants
Trial identifier NCT01644630, 2012-0147


The aim of this study is to test whether or not the use of screw-retained implant crowns on customized zirconia abutments results in biological, technical and esthetic outcomes similar to those obtained with cemented all-ceramic crowns on customized zirconia abutments, both made with a computer-aided design and manufacturing procedure (CAD/CAM).

The null-hypotheses is that marginal bone level change is equal at screw-retained and cemented crowns

United States No locations recruiting
Other countries No locations recruiting

Study Design

Allocation randomized
Intervention model parallel assignment
Primary purpose supportive care
Masking no masking
(Active Comparator)
Cemented single crown: zirconia abutment (Straumann Cares abutment) with an all-ceramic lithium disilicate crown
cemented crowns
The final lithium disilicate crowns will be cemented with an adhesive cement after tightening the abutments with the torque indicated by the manufacturer and closing the screw access hole with white guttapercha. The abutment will be cleaned with ethanol. A retraction cord will be placed for cementation if indicated. The crown will be etched with hydrofluoric acid and subsequently silanized. A sufficient amount of cement will be filled in the crown without creating major excesses. When the crown is seated correctly, the cement will be light-cured for a few seconds to facilitate the removal of the now hard excess cement. - Excess cement will be meticulously removed with a carbon scaler. The removal of all excess cement will be checked with an X-ray and by visual and tactile inspection.
(Active Comparator)
Screw-retained single crown: zirconia abutment (Straumann Cares abutment), directly veneered with veneering ceramic
screw-retained crowns
The screw-retained crowns will be inserted and tightened with the torque indicated by the manufacturer. The screw access hole will to be closed with white guttapercha and a composite filling (Filtek, 3M ESPE).

Primary Outcomes

Marginal bone level
time frame: 5 years

Secondary Outcomes

Biological, technical and esthetic outcome
time frame: up to 5 years
Biological, technical and esthetic outcome
time frame: up to 5 years
Biological, technical and esthetic outcome
time frame: up to 5 years
Biological, technical and esthetic outcome
time frame: up to 5 years

Eligibility Criteria

All participants from 18 years up to 80 years old.

Inclusion Criteria: - Single-tooth Straumann Bone Level in the anterior maxilla or mandible - At least one adjacent natural tooth present - Implant position enabling both screw-retained and cemented crown - Informed consent signed Exclusion Criteria: - Smoking more than 15 cigarettes a day - Poor oral hygiene (Plaque index over 30%) - Pregnancy at the date of inclusion

Additional Information

Official title A Randomized Controlled Clinical Trial Comparing Cemented Versus Screw-retained Implant-supported Single Crowns With Customized Zirconia Abutments
Principal investigator Daniel Thoma, PD Dr.
Trial information was received from ClinicalTrials.gov and was last updated in February 2017.
Information provided to ClinicalTrials.gov by University of Zurich.