title: Mechanical stability assessment of novel orthodontic mini-implant designs: Part 2.
abstract: OBJECTIVE
  To assess the mechanical stability of a newly revised orthodontic mini-implant design (N2) compared with a design introduced in Part 1 of the study (N1) and the most widely-used commercially-available design (CA). To evaluate the mean buccal bone thickness of maxillary and mandibular posterior teeth using cone-beam computed tomography (CBCT).
  
  
  METHODS
  From the CBCT scans of 20 patients, six tomographic cross-sections were generated for each tooth. Buccal bone thickness was measured from the most convex point on the bone to the root surface. CA (1.5 mm in diameter and 6 mm in length), N1, and N2 (shorter and narrower than N1) were inserted in simulated bone with cortical and trabecular bone layers. Mechanical stability was compared in vitro through torque and lateral displacement tests.
  
  
  RESULTS
  The bone thickness ranged from 2.26 to 3.88 mm. Maximum insertion torque was decreased significantly in N2 compared to N1. However, force levels for all displacement distances and torque ratio were the highest in N2, followed by N1 and CA (α = .05).
  
  
  CONCLUSIONS
  Both torque and lateral displacement tests highlighted the enhanced stability of N2 compared with CA. Design revisions to N1 effectively mitigated N1's high insertion torque and thus potentially reduced microdamage to the surrounding bone. The N2 design is promising as evidenced by enhanced stability and high mechanical efficiency. Moreover, N2 is not limited to placement in interradicular spaces and has the capacity to be placed in the buccal bone superficial to the root surface with diminished risk of endangering nearby anatomic structures during placement and treatment.
authors.affiliation: Section on Orthodontics, University of California, Los Angeles, USA.
authors.forename: Christine
authors.initials: C
authors.lastname: Hong
authors.forename: Peter
authors.initials: P
authors.lastname: Truong
authors.forename: Ha Na
authors.initials: HN
authors.lastname: Song
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Wu
authors.forename: Won
authors.initials: W
authors.lastname: Moon
mesh_terms: D000293:Adolescent; D000328:Adult; D000497:Alloys; D000704:Analysis of Variance; D040761:Biomimetic Materials; D015519:Bone Density; D001863:Bone Screws; D054893:Cone-Beam Computed Tomography; D003722:Dental Alloys; D015921:Dental Implants; D003799:Dental Stress Analysis; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging; D008437:Maxilla / Q000000981:diagnostic imaging; D008904:Miniaturization; D008953:Models, Anatomic; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D010865:Pilot Projects; D014025:Titanium; D019415:Torque; D055815:Young Adult
chemical_list: D000497:Alloys; D003722:Dental Alloys; D015921:Dental Implants; C031462:titanium alloy (TiAl6V4); D014025:Titanium