Removal Torque and Biofilm Accumulation at Two Dental Implant-Abutment Joints After Fatigue

• Published in: The International journal of oral and maxillofacial implants Vol. 31; no. 4; p. 813
• Main Authors: Pereira, Jorge, Morsch, Carolina S, Henriques, Bruno, Nascimento, Rubens M, Benfatti, Cesar Am, Silva, Filipe S, López-López, José, Souza, Júlio Cm
• Format: Journal Article
• Language: English
• Published: United States 01-07-2016
• Subjects: Analysis of Variance; Biofilms - growth & development; Colony Count, Microbial; Dental Abutments - microbiology; Dental Implant-Abutment Design; Dental Implants - microbiology; Dental Prosthesis, Implant-Supported - microbiology; Dental Stress Analysis; Humans; Surface Properties; Torque
• ISSN: 1942-4434
• DOI: 10.11607/jomi.4173

The aim of this study was to evaluate the removal torque and in vitro biofilm penetration at Morse taper and hexagonal implant-abutment joints after fatigue tests.
Sixty dental implants were divided into two groups: (1) Morse taper and (2) external hexagon implant-abutment systems. Fatigue tests on the implant-abutment assemblies were performed at a normal force (FN) of 50 N at 1.2 Hz for 500,000 cycles in growth medium containing human saliva for 72 hours. Removal torque mean values (n = 10) were measured after fatigue tests. Abutments were then immersed in 1% protease solution in order to detach the biofilms for optical density and colony-forming unit (CFU/cm²) analyses. Groups of implant-abutment assemblies (n = 8) were cross-sectioned at 90 degrees relative to the plane of the implant-abutment joints for the microgap measurement by field-emission guns scanning electron microscopy.
Mean values of removal torque on abutments were significantly lower for both Morse taper (22.1 ± 0.5 μm) and external hexagon (21.1 ± 0.7 μm) abutments after fatigue tests than those recorded without fatigue tests (respectively, 24 ± 0.5 μm and 24.8 ± 0.6 μm) in biofilm medium for 72 hours (P = .04). Mean values of microgap size for the Morse taper joints were statistically signicantly lower without fatigue tests (1.7 ± 0.4 μm) than those recorded after fatigue tests (3.2 ± 0.8 μm). Also, mean values of microgap size for external hexagon joints free of fatigue were statistically signicantly lower (1.5 ± 0.4 μm) than those recorded after fatigue tests (8.1 ± 1.7 μm) (P < .05). The optical density of biofilms and CFU mean values were lower on Morse taper abutments (Abs630nm at 0.06 and 2.9 × 10⁴ CFU/cm²) than that on external hexagon abutments (Abs630nm at 0.08 and 4.5 × 10⁴ CFU/cm²) (P = .01).
The mean values of removal torque, microgap size, and biofilm density recorded at Morse taper joints were lower in comparison to those recorded at external hexagon implant-abutment joints after fatigue tests in a simulated oral environment for 72 hours.