title: Local variations in turnover of periodontal collagen fibers in rats.
abstract: OBJECTIVE
  The exact cause of orthodontic relapse is still unclear, although it is often suggested to be caused by periodontal collagen fibers. We hypothesize that long-lived collagen fibers in the periodontium cause relapse. The aim was to determine the half-life of periodontal collagen fibers around rat molars.
  
  
  METHODS
  Thirty weanling rats were repeatedly injected with (3) H-proline, and autoradiography of histological sections was performed at 1, 4, 8, 15, 22, 29, 36, 57, 78 and 113 d after labeling. Grain densities determined in specific areas of the periodontium were used to calculate collagen half-life.
  
  
  RESULTS
  The half-life (t(½) ) was found to decrease from the supra-alveolar region to the apical periodontal ligament region. It was longer in the supra-alveolar region (1.39 ± 0.14 wk) compared with the deeper regions (p < 0.05). The t(½) of the upper periodontal ligament region (0.78 ± 0.20 wk) was longer than that of the inter-radicular periodontal ligament region (0.42 ± 0.07 wk, p < 0.05). The t(½) of the apical periodontal ligament region was 0.61 ± 0.15 wk.
  
  
  CONCLUSIONS
  The data indicate that long-lived collagen fibers do not exist in the soft tissues of the periodontium, and are probably not responsible for relapse. The differences in collagen half-life might be caused by local variations in compressive strain induced by normal function.
authors: Department of Orthodontics & Craniofacial Biology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors: S
authors: S
authors: Henneman
authors: R R
authors: RR
authors: Reijers
authors: J C
authors: JC
authors: Maltha
authors: J W
authors: JW
authors: Von den Hoff
mesh_terms: D000539:Alveolar Process / Q000033:anatomy & histology; D000818:Animals; D001345:Autoradiography; D003094:Collagen / Q000378:metabolism*; D005260:Female; D006207:Half-Life; D008297:Male; D008963:Molar / Q000033:anatomy & histology; D010486:Periapical Tissue / Q000033:anatomy & histology / Q000378:metabolism; D010513:Periodontal Ligament / Q000033:anatomy & histology / Q000378:metabolism*; D011392:Proline / Q000378:metabolism; D019275:Radiopharmaceuticals; D051381:Rats; D017208:Rats, Wistar; D012867:Skin / Q000033:anatomy & histology / Q000378:metabolism; D013997:Time Factors; D019227:Tooth Apex / Q000033:anatomy & histology; D014092:Tooth Root / Q000033:anatomy & histology; D014316:Tritium
chemical_list: D019275:Radiopharmaceuticals; D014316:Tritium; D003094:Collagen; D011392:Proline