title: Dental root resorption and repair: histology and histometry during physiological drift of rat molars.
abstract: OBJECTIVE
  The process of dental root resorption and subsequent cementum regeneration has not been sufficiently elucidated. This study aimed to examine the process of the root resorption and cementum regeneration during physiological tooth drift using a rat model, and to evaluate this experimental model.
  
  
  METHODS
  Distal roots in mandibular first molars and the surrounding periodontal tissues were investigated with light and electron microscopy. The light microscopic approach included histochemical and histometric analyses utilizing the tartrate-resistant acid phosphatase (TRAP) reaction.
  
  
  RESULTS
  Root resorption was observed in the distal side of the roots and was most active in 5- to 6-week-old rats, and gradually decreased hereafter. An increase in the number of TRAP-positive mononuclear cells, which seemed to be odontoclast precursor cells, preceded the increase in the number of odontoclasts. Root resorption was transient, and was followed by the new formation of acellular extrinsic fiber cementum accompanied with only a slight inflammation, and therefore classified as external surface resorption. Preparation for new cementum started adjacent to the resorption areas when root resorption was most active.
  
  
  CONCLUSIONS
  The root resorption during drift in rats is transient and followed by acellular extrinsic fiber cementum regeneration. Cellular kinetics suggested that odontoclast precursor cells are supplied as mononuclear cells from vascular spaces.
authors.affiliation: Department of Periodontology, Division of Oral Rehabilitation, Faculty of Dental Science, Kyushu University, Fukuoka, Japan. rkimura@dent.kyushu-u.ac.jp
authors.forename: Ryusei
authors.initials: R
authors.lastname: Kimura
authors.forename: Hisashi
authors.initials: H
authors.lastname: Anan
authors.forename: Akiko
authors.initials: A
authors.lastname: Matsumoto
authors.forename: Daisuke
authors.initials: D
authors.lastname: Noda
authors.forename: Katsumasa
authors.initials: K
authors.lastname: Maeda
mesh_terms: D000135:Acid Phosphatase; D000818:Animals; D004396:Coloring Agents; D003739:Dental Cementum / Q000502:physiology*; D007527:Isoenzymes; D008855:Microscopy, Electron, Scanning; D010010:Osteoclasts / Q000502:physiology / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D012038:Regeneration; D012391:Root Resorption / Q000209:etiology / Q000503:physiopathology*; D000071681:Tartrate-Resistant Acid Phosphatase; D014085:Tooth Migration / Q000150:complications
chemical_list: D004396:Coloring Agents; D007527:Isoenzymes; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase