title: Optimally oriented grooves on dental implants improve bone quality around implants under repetitive mechanical loading.
abstract: The aim was to investigate the effect of groove designs on bone quality under controlled-repetitive load conditions for optimizing dental implant design. Anodized Ti-6Al-4V alloy implants with -60° and +60° grooves around the neck were placed in the proximal tibial metaphysis of rabbits. The application of a repetitive mechanical load was initiated via the implants (50N, 3Hz, 1800 cycles, 2days/week) at 12weeks after surgery for 8weeks. Bone quality, defined as osteocyte density and degree of biological apatite (BAp) c-axis/collagen fibers, was then evaluated. Groove designs did not affect bone quality without mechanical loading; however, repetitive mechanical loading significantly increased bone-to-implant contact, bone mass, and bone mineral density (BMD). In +60° grooves, the BAp c-axis/collagen fibers preferentially aligned along the groove direction with mechanical loading. Moreover, osteocyte density was significantly higher both inside and in the adjacent region of the +60° grooves, but not -60° grooves. These results suggest that the +60° grooves successfully transmitted the load to the bone tissues surrounding implants through the grooves. An optimally oriented groove structure on the implant surface was shown to be a promising way for achieving bone tissue with appropriate bone quality. This is the first report to propose the optimal design of grooves on the necks of dental implants for improving bone quality parameters as well as BMD. The findings suggest that not only BMD, but also bone quality, could be a useful clinical parameter in implant dentistry.
  
  
  
  Although the paradigm of bone quality has shifted from density-based assessments to structural evaluations of bone, clarifying bone quality based on structural bone evaluations remains challenging in implant dentistry. In this study, we firstly demonstrated that the optimal design of dental implant necks improved bone quality defined as osteocytes and the preferential alignment degree of biological apatite c-axis/collagen fibers using light microscopy, polarized light microscopy, and a microbeam X-ray diffractometer system, after application of controlled mechanical load. Our new findings suggest that bone quality around dental implants could become a new clinical parameter as well as bone mineral density in order to completely account for bone strength in implant dentistry.
authors.affiliation: Department of Applied Prosthodontics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan. Electronic address: kuroshima@nagasaki-u.ac.jp.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Kuroshima
authors.affiliation: Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, Osaka, Japan.
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Nakano
authors.affiliation: Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, Osaka, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Ishimoto
authors.affiliation: Department of Applied Prosthodontics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: Muneteru
authors.initials: M
authors.lastname: Sasaki
authors.affiliation: Department of Applied Prosthodontics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: Maaya
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Department of Applied Prosthodontics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: Munenori
authors.initials: M
authors.lastname: Yasutake
authors.affiliation: Department of Applied Prosthodontics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Sawase
mesh_terms: D000497:Alloys; D000818:Animals; D001031:Apatites / Q000737:chemistry; D015519:Bone Density / Q000187:drug effects; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000502:physiology*; D002452:Cell Count; D003094:Collagen / Q000737:chemistry; D015921:Dental Implants; D055595:Mechanical Phenomena; D016348:Osseointegration / Q000187:drug effects; D010011:Osteocytes / Q000166:cytology / Q000187:drug effects; D011817:Rabbits; D014025:Titanium / Q000494:pharmacology; D016474:Weight-Bearing; D055114:X-Ray Microtomography
chemical_list: D000497:Alloys; D001031:Apatites; D015921:Dental Implants; C031462:titanium alloy (TiAl6V4); D003094:Collagen; D014025:Titanium
keywords: Bone quality; Implant design; Mechanical loading; Orientation of biological apatite c-axis/collagen fibers; Osteocytes