Mechanical behavior and failure analysis of prosthetic retaining screws after long-term use in vivo. Part 3: Preload and tensile fracture load testing. J Prosthodont 2008 Apr;17(3):192-200
Date
01/22/2008Pubmed ID
18205737DOI
10.1111/j.1532-849X.2007.00290.xScopus ID
2-s2.0-41649106250 (requires institutional sign-in at Scopus site) 11 CitationsAbstract
PURPOSE: The aim of this study was to determine the preload and tensile fracture load values of prosthetic retaining screws after long-term use in vivo compared to unused screws (controls). Additionally, the investigation addressed whether the preload and fracture load values of prosthetic retaining screws reported by the manufacturer become altered after long-term use in vivo.
MATERIALS AND METHODS: For preload testing, 10 new screws (controls) from Nobel Biocare (NB) and 73 used retaining screws [58 from NB and 15 from Sterngold (SG)] were subjected to preload testing. For tensile testing, eight controls from NB and 58 used retaining screws (46 from NB and 12 from SG) were subjected to tensile testing. Used screws for both tests were in service for 18-120 months. A custom load frame, load cell, and torque wrench setup were used for preload testing. All 83 prosthetic screws were torqued once to 10 Ncm, and the produced preload value was recorded (N) using an X-Y plotter. Tensile testing was performed on a universal testing machine and the resulting tensile fracture load value was recorded (N). Preload and tensile fracture load values were analyzed with 2-way ANOVA and Tukey post-hoc tests.
RESULTS: There was a significant difference between preload values for screws from NB and screws from SG (p < 0.001). The preload values for gold alloy screws from NB decreased as the number of years in service increased. There was a significant difference between tensile fracture values for the three groups (gold alloy screws from NB and SG and palladium alloy screws from NB) at p < 0.001. The tensile fracture values for gold alloy screws from NB and SG decreased as the number of years in service increased.
CONCLUSIONS: In fixed detachable hybrid prostheses, perhaps as a result of galling, the intended preload values of prosthetic retaining screws may decrease with increased in-service time. The reduction of the fracture load value may be related to the increase of in-service time; however, the actual determination of this relationship is not possible from this study alone.
Author List
Al Jabbari YS, Fournelle R, Ziebert G, Toth J, Iacopino AMAuthor
Jeffrey M. Toth PhD Associate Dean for Research in the School of Dentistry department at Marquette UniversityMESH terms used to index this publication - Major topics in bold
Analysis of VarianceDental Alloys
Dental Prosthesis Design
Dental Prosthesis Retention
Dental Prosthesis, Implant-Supported
Dental Restoration Failure
Dental Restoration Wear
Dental Stress Analysis
Electron Probe Microanalysis
Equipment Design
Equipment Failure Analysis
Hardness
Humans
Metallurgy
Microscopy, Electron, Scanning
Stress, Mechanical
Surface Properties
Tensile Strength
Torque