title: Is there an optimal force level for sutural expansion?
abstract: BACKGROUND
  The purpose of this study was to establish the causal relationships between expansion force magnitudes, sutural separation, and sutural bone formation.
  
  
  METHODS
  Thirty-seven 6-week-old rabbits were randomly assigned to 4 force groups (0, 50, 100, or 200 g). Constant forces were delivered for 42 days by nickel-titanium open-coil springs to miniscrew implants (MSIs) placed in the frontal bone on both sides of the midsagittal suture. Inter-MSI and bone marker widths were measured biweekly to quantify sutural separation and MSI movements. Sutural bone formation was quantified based on the incorporation of fluorescent bone labels administered at days 18, 28, and 38.
  
  
  RESULTS
  Nine of 74 MSIs failed between days 0 and 14, including 4 in the controls and 5 in the 50-g group. A decelerating curvilinear pattern of sutural separation was evident in the 50-g, 100-g, 200-g groups. Bone markers showed that sutural widths increased by 0.6, 3.2, 5.1, and 6.2 mm in the control, 50-g, 100-g, and 200-g groups, respectively. Except for the 200-g group, significantly greater amounts of bone formation were observed between days 18 and 28 than between days 28 and 38. Sutural bone formation also increased with increasing forces up to 100 g; there was no difference between the 100-g and the 200-g groups. Sutural separation explained 71% and 53% of the variations in bone formation between days 18 and 28 and days 28 and 38, respectively.
  
  
  CONCLUSIONS
  Within the limits of this study, sutural bone formation is directly related to the amount of sutural separation, which is in turn related to the amount of force applied. The results suggest that there is a level of induced sutural separation that provides the greatest amount of bone formation.
authors: Department of Orthodontics and Oral Facial Genetics, School of Dentistry, Indiana University, Indianapolis, IN 46202, USA. ssliu@iupui.edu
authors: Sean Shih-Yao
authors: SS
authors: Liu
authors: Lynne A
authors: LA
authors: Opperman
authors: Hee-Moon
authors: HM
authors: Kyung
authors: Peter H
authors: PH
authors: Buschang
mesh_terms: D000497:Alloys; D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002508:Cephalometry; D003393:Cranial Sutures / Q000473:pathology / Q000502:physiology*; D005452:Fluoresceins; D005456:Fluorescent Dyes; D005624:Frontal Bone / Q000473:pathology / Q000502:physiology*; D008297:Male; D008856:Microscopy, Fluorescence; D009532:Nickel; D009969:Orthodontic Wires; D010012:Osteogenesis / Q000502:physiology*; D010118:Oxytetracycline; D011817:Rabbits; D011897:Random Allocation; D013314:Stress, Mechanical; D013997:Time Factors; D014025:Titanium
chemical_list: D000497:Alloys; D005452:Fluoresceins; D005456:Fluorescent Dyes; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium; C007740:fluorexon; D010118:Oxytetracycline