1433 Retentive Characteristics of Narrow-Diameter Implant-Retained Overdentures after Fatigue Loading

Saturday, March 24, 2012: 9:45 a.m. - 11 a.m.
Presentation Type: Poster Session
M. GUSTAFSON, 3M Dental Products Lab, St. Paul, MN, D. CHAN, Health Sciences Center, D322, University of Washington, Seattle, WA, and K. CHUNG, Restorative Dentistry, University of Washington, Seattle, WA
Objectives: To compare retentive and morphological changes of five stud attachment systems for implant-retained overdentures after repeated insertion (7,200 cycles) and 78N loading in vitro onto implant abutments.

Methods: Five mechanical (Pink Liner, Zest Locator; Metal Housing and Micro Metal Housing, 3M IMTEC; Micro Metal Housing, Intra-Lock; and Silicone Liner, Dentatus USA) attachments were embedded in overdenture base (n=10).  Overdentures with Locator attachments were tested on acrylic models with two parallel Endure implants (4.3×9mm). The O-ring attachments and silicone liner were tested on models with four parallel narrow-diameter implants. Specimens were loaded sinusoidally from zero to 78N in a coil cycler fatigue machine (Proto-Tech, Portland, OR) at 2Hz for 7,200 cycles in a 37°C water bath.  Vertical tensile dislodging forces were recorded at a cross-head speed of 50 mm/min after repeated insertions (baseline, 50, 500, 900, 1,800, 3,600, 5,400, and 7,200 cycles). Statistical analysis: ANOVA and Tukey HSD post-hoc tests at the 95% confidence level.

Results: The peak load-to-dislodgement force ranged from 6.4 (0.5) N to 19.0 (2.9) N after 7,200 cycles of repeated insertion.  The retention values of the MDI Micro Metal Housing and Locator Pink Liner attachments were significantly higher than other groups after 7,200 cycles (P<.01). The Locator Pink Liner group, Silicone Liner group, and MDI Micro Metal Housing with O-ring attachment showed changes in retentive force values of 82.8%, 31.5%, and 18.1% respectively after 7,200 cycles fatigue loading. Microscopic examination of the specimens revealed wear and degradation consistent with the loss of retention.

Conclusions: The retention force values of O-ring attachments with four narrow-diameter implant systems were equivalent to the Locator Pink Liner with two regular implants after 7,200 cycles fatigue loading.

Keywords: Biomechanics, Loading, Oral implantology, Prosthodontics and Wear