Comparative study of four retentive anchor systems for implant supported overdentures--retention force changes.
OBJECTIVE
Wear of attachments leads to a loss of retention and potentially reduces the function of complete dentures. This study evaluated the retention force changes of different prefabricated attachment systems for implant-supported overdentures to estimate the wear constancy and applicability in clinical practice.


METHODS
Four prefabricated attachment systems were tested [Group SG: retentive ball attachment (Straumann, Switzerland) with gold matrix, Group ST: retentive ball attachment (Straumann, Switzerland) with titanium spring matrix, Group IB: UNOR i-Ball with Ecco matrix (UNOR, Switzerland) and Group IMZ: IMZ-TwinPlus ball attachment with gold matrix (DENTSPLY Friadent, Germany)]. Ten samples of each system were subjected to 10,000 insertion-separation cycles.


RESULTS
Results showed that all types of attachments showed wear, which led to a loss of retention force after an initial increase at the beginning of the wear simulation. Attachments with a plastic retention insert or gold matrices underwent the smallest changes in retention force. The titanium spring system showed the largest changes in retention force and a greater variation between the different cycles and specimen. This behaviour is probably caused by a large fitting tolerance of the titanium spring.


CONCLUSIONS
Attachment systems which possess a male and female component of different material composition are preferable. They show smaller changes in the retention force. For retention force increase and wear compensation, an attachment system should be adjustable.
Department of Prosthodontics, Preclinical Education and Dental Materials Science, University of Bonn, Bonn, Germany. sbayer@uni-bonn.de
Stefan
S
Bayer
Daniela
D
Steinheuser
Manfred
M
Grüner
Ludger
L
Keilig
Norbert
N
Enkling
Helmut
H
Stark
Sebastian
S
Mues
D000537:Aluminum Oxide; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D019554:Dental Restoration Wear; D003799:Dental Stress Analysis; D003834:Denture Precision Attachment; D003781:Denture Retention / Q000295:instrumentation*; D003828:Denture, Overlay; D006047:Gold Alloys; D008422:Materials Testing; D010969:Plastics; D014025:Titanium
D006047:Gold Alloys; D010969:Plastics; D014025:Titanium; D000537:Aluminum Oxide