Abstract
The aim of this study was to verify whether screw abutment lubrication can generate higher preload values compared to non-lubricated screws, a titanium abutment was screwed onto an implant analog and scanned with the Procera System to generate 20 zirconia abutments. MKIII Brånemark implants were clamped to a precision torque device, and the abutments were distributed in dry and wet groups with 10 specimens each. In the wet groups, the inner threads of the implants were filled with artificial saliva. All abutments were fastened with a Torqtite screw under 32 Ncm. Ten detorque measurements were performed per group pushing the reverse button of the Torque controller soon after screw tightening with values registered. The mean detorque values were calculated and compared by a Student's t test (α=0.05). The wet condition presented significantly higher mean detorque than the dry condition (31.5 ± 1.2 versus 27.5 ± 1.5 Ncm, respectively; p=0.0000024). In conclusion, there was always a loss in the initial torque values when the removal torque was measured under both conditions. The wet condition presented higher mean torque than the dry condition. Better preload values were established in the wet group, suggesting that the abutment screw must be lubricated in saliva to avoid further loosening.
Highlights
Osseointegrated implants is a good represent an acceptable treatment modality for complete or partially edentulous patients
There have been works evaluating the behavior of abutment screws after loading, as well as attempts to improve their mechanical properties by modification/deposition of functional layers
The longevity of implant-supported prosthesis can be influenced by several biomechanical aspects: passive fit, machining precision, implant/abutment stability, etc. [5,7,14]
Summary
Osseointegrated implants is a good represent an acceptable treatment modality for complete or partially edentulous patients. Mechanical failures associated with singleimplant restorations represent a challenge to clinicians. Among the types of mechanical failures, abutment screw loosening is still the most frequently reported in the literature [1,2,3,4,5]. This issue is too critical in cemented restorations: first, crowns cannot be removed intact in most situations; second, crown loosening can lead to oblique forces at implant-abutment junction and screw fracturing. There have been works evaluating the behavior of abutment screws after loading, as well as attempts to improve their mechanical properties by modification/deposition of functional layers. Tzenakis et al [10] verified that after 10 repetitions using slotted gold prosthetic screws under human salivary contamination, the preload values increased up to 16.3% of the original values
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