title: Development and application of a direct method to observe the implant/bone interface using simulated bone.
abstract: BACKGROUND
  Primary stability after implant placement is essential for osseointegration. It is important to understand the bone/implant interface for analyzing the influence of implant design on primary stability. In this study rigid polyurethane foam is used as artificial bone to evaluate the bone-implant interface and to identify where the torque is being generated during placement.
  
  
  METHODS
  Five implant systems-Straumann-Standard (ST), Straumann-Bone Level (BL), Straumann-Tapered Effect (TE), Nobel Biocare-Brånemark MKIII (MK3), and Nobel Biocare-Brånemark MKIV (MK4)-were used for this experiment. Artificial bone blocks were prepared and the implant was installed. After placement, a metal jig and one side artificial bone block were removed and then the implant embedded in the artificial bone was exposed for observing the bone-implant interface. A digital micro-analyzer was used for observing the contact interface.
  
  
  RESULTS
  The insertion torque values were 39.35, 23.78, 12.53, 26.35, and 17.79 N cm for MK4, BL, ST, TE, and MK3, respectively. In ST, MK3, TE, MK4, and BL the white layer areas were 61 × 103 μm(2), 37 × 103 μm(2), 103 × 103 μm(2) in the tapered portion and 84 × 03 μm(2) in the parallel portion, 134 × 103 μm(2), and 98 × 103 μm(2) in the tapered portion and 87 × 103 μm(2) in the parallel portion, respectively.
  
  
  CONCLUSIONS
  The direct observation method of the implant/artificial bone interface is a simple and useful method that enables the identification of the area where implant retention occurs. A white layer at the site of stress concentration during implant placement was identified and the magnitude of the stress was quantitatively estimated. The site where the highest torque occurred was the area from the thread crest to the thread root and the under and lateral aspect of the platform. The artificial bone debris created by the self-tapping blade accumulated in both the cutting chamber and in the space between the threads and artificial bone.
authors.affiliation: Department of Implant Dentistry, School of Dentistry, Showa University, 2-1-1 Kitasenzoku Ota-ku, Tokyo, 145-8515 Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yamaguchi
authors.affiliation: Division of Oral Health Sciences, Department of Masticatory Function Rehabilitation, Oral Implantology and Regenerative Dental Medicine, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510 Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shiota
authors.affiliation: Dental Implant Clinic, Dental Hospital, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510 Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: FuJii
authors.affiliation: Department of Implant Dentistry, School of Dentistry, Showa University, 2-1-1 Kitasenzoku Ota-ku, Tokyo, 145-8515 Japan.
authors.forename: Michi
authors.initials: M
authors.lastname: Sekiya
authors.affiliation: Department of Implant Dentistry, School of Dentistry, Showa University, 2-1-1 Kitasenzoku Ota-ku, Tokyo, 145-8515 Japan ; Dental Implant Center, Showa Dental Hospital, 2-1-1 Kitasenzoku Ota-ku, Tokyo, 145-8515 Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ozeki
keywords: Artificial bone; Implant design; Implant/bone interface; Primary stability