title: Effect of implant design on primary stability using torque-time curves in artificial bone.
abstract: BACKGROUND
  Primary stability following implant placement is essential for osseointegration and is affected by both implant design and bone density. The aim of this study was to compare the relationships between torque-time curves and implant designs in a poor bone quality model.
  
  
  METHODS
  Nine implant designs, with five implants in each category, were compared. A total of 90 implants (Straumann: Standard RN, Bone Level RC, Tapered Effect RN; Nobel Biocare: Brånemark MKIII, MKIV) were placed in type IV artificial bone. Torque-time curves of insertion and removal were recorded at the rate of 1000 samples/s by a torque analyzer.
  
  
  RESULTS
  The torque-time curves were divided into initial, parallel, tapered, and platform areas. The mean torque rise rate of the parallel area was smallest at 0.36 N · cm/s, with a significant difference from those of the other areas (p < 0.05). Values of 2.14, 2.33, and 2.65 N · cm/s were obtained for the initial, tapered, and platform areas, respectively. The removal torque for six of the implant designs (Bone Level RC 8, 10, and 12 mm; Tapered Effect RN 10 mm; Brånemark MKIII 10 mm, MKIV 10 mm) was significantly smaller than the corresponding insertion torque (p < 0.05). However, the removal torque for ST6, 8, and 10 was almost the same as or slightly greater than the corresponding insertion torque.
  
  
  CONCLUSIONS
  The insertion torque-time curves and design features of the implants were accurately transferred. Increasing implant taper angle appeared to increase the torque rate. Torque was mainly generated from the superior surface to the valley of the thread and the inferior and axial surfaces of the platform, while the inferior and axial surfaces of the thread did not significantly affect torque generation.
authors.affiliation: Department of Implant Dentistry, Showa University School of Dentistry, 2-1-1 Kitasenzoku Ota-ku, Tokyo, 145-8515, Japan. blacklab87@gmail.com.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yamaguchi
authors.affiliation: Oral Implantology and Regenerative Dental Medicine, Department of Masticatory Function Rehabilitation, Division of Oral Health Sciences, 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: Oral Implantology Department of Prosthodontic Dentistry for Function of TMJ and Occlusion, Kanagawa Dental University, 82, Inaokachou, Yokosuka-shi, Kanagawa, 238-8580, Japan.
authors.forename: Motohiro
authors.initials: M
authors.lastname: Munakata
authors.affiliation: Oral Implantology and Regenerative Dental Medicine, Department of Masticatory Function Rehabilitation, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Kasugai
authors.affiliation: Department of Implant Dentistry, Showa University School of Dentistry, 2-1-1 Kitasenzoku Ota-ku, Tokyo, 145-8515, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ozeki
keywords: Bone density; Implant design; Insertion torque; Primary stability; Removal torque; Torque-time curve