MDent, Faculty of Health Sciences, University of the Witwatersrand / PURPOSE
The purpose of this in vitro investigation was to determine the effect of using either gold or
titanium retaining screws on preload in the dental implant body-abutment complex. This
preload is of vital importance for the long term success of the dental implant complex.
Inadequate preload results in either loosening or fracture of the retaining screw, and is the
most commonly occurring mechanical complication in implant supported/retained prostheses.
Similar complications occur when excessive preload is applied to the retaining screws. These
complications can result in unscheduled visits with costly and time consuming repairs for the
clinician and patient.
Routine maintenance protocols for implant supported prostheses range from biannually to
five year visits to the dentist. Maintenance visits involve removal of the prosthesis facilitating
cleaning of both the implant and prosthesis and inspection of retaining screws .
This study sought to gain insight into changes in preload generation after repeated torque
application to gold and titanium screws and to observe whether gold or titanium generated
better preload. A maintenance protocol would be suggested if any observable pattern was
noted.
MATERIALS AND METHODS
The test setup consisted of an implant body, a cylindrical transmucosal abutment and the
retaining screws (gold or titanium). The implant body was anchored using a load cell.
Transmucosal abutments were attached to the implant body using either a gold or titanium
v
retaining screw. A torque gauge was used to apply torque of 20Ncm, 32Ncm and 40Ncm to
the retaining screws. This was undertaken to investigate the effect of gold or titanium on
preload generated. The effect of applying torque beyond manufacturers recommended
32Ncm was carried out to see if greater preloads could be achieved. All components were
from the Southern Implant system.
RESULTS
Gold retaining screws were found to achieve consistently higher preload values than titanium
retaining screws. Preload values were not significantly different from the first to the tenth
torque cycle. Titanium screws showed more consistent preload values, albeit lower than those
of gold retaining screws. However due to possible galling of the internal thread of the implant
body by titanium screws, gold screws remain the retaining screw of choice.
Maintenance protocols suggest replacing retaining screws every 20 years. After ten torque
cycles were applied to each screw there was an insignificant change in preload generated in
both titanium and gold screws. This study was therefore inconclusive with regards to
maintenance protocols.
CONCLUSION
Within the limitations of this study, gold retaining screws generated better preload than
titanium. Torque application beyond manufacturers’ recommendations resulted in a more
stable implant complex. Further investigation into repeated torque application to retaining
screws is required, to determine ideal maintenance protocols.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/9034 |
| Date | 14 February 2011 |
| Creators | Doolabh, Rajesh |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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