title: Effect of Increasing Low-Intensity Pulsed Ultrasound and a Functional Appliance on the Mandibular Condyle in Growing Rats.
abstract: OBJECTIVE
  Functional appliances are used for treatment of lower-jaw deficiencies in growing individuals; however, their effectiveness is debatable. Low-intensity pulsed ultrasound (US) is a noninvasive method, which has been shown to stimulate cartilage and bone formation with 20 minutes of application. This study was designed to test the hypothesis that increasing low-intensity pulsed US application from 20 to 40 min/d will enhance mandibular condylar growth in growing rats, especially when combined with a functional appliance.
  
  
  METHODS
  Fifty-four Sprague Dawley rats were divided into 6 groups (n = 9): control, low-intensity pulsed US for 20 minutes, low-intensity pulsed US for 40 minutes, the functional appliance, the functional appliance plus low-intensity pulsed US for 20 minutes, and the functional appliance plus low-intensity pulsed US for 40 minutes. Low-intensity pulsed US was applied for 28 days. All rats were then euthanized, and their mandibles were dissected for morphometric, histomorphometric, and micro-computed tomographic analyses.
  
  
  RESULTS
  Among all study groups, the 20-minute US group showed significant increases in most of the measured variables (P < .05) except for condylar process length (P = .18), whereas the functional appliance-plus-40-min US group showed the least favorable results. The 20-minute US group showed increases in proliferative and hypertrophic cell counts and widths and enhanced microarchitecture of trabecular bone compared with the 40-minute US group. The functional appliance-plus-20-minute US group showed better results compared with the functional appliance-alone and functional appliance-plus-40-minute US groups.
  
  
  CONCLUSIONS
  A daily application of low-intensity pulsed US for 20 minutes in growing rats affects mandibular growth, either alone or in combination with a functional appliance. Further study with a longer observation period is required to study the long-term effects and stability of newly formed bone.
authors.affiliation: Department of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.|Medical Science Graduate Program, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Harmanpreet
authors.initials: H
authors.lastname: Kaur
authors.affiliation: Department of Chemical and Materials Engineering, Faculty of Engineering, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Hasan
authors.initials: H
authors.lastname: Uludağ
authors.affiliation: Department of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Dederich
authors.affiliation: Departments of Dentistry and Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Tarek
authors.initials: T
authors.lastname: El-Bialy
mesh_terms: D000818:Animals; D008335:Mandibular Condyle / Q000000981:diagnostic imaging*; D023421:Models, Animal; D017289:Orthodontic Appliances, Functional; D010012:Osteogenesis / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D000069453:Ultrasonic Waves
keywords: functional appliance; low-intensity pulsed ultrasound; mandibular condyle; musculoskeletal ultrasound