title: Root resorption on torqued human premolars shown by tartrate-resistant acid phosphatase histochemistry and transmission electron microscopy.
abstract: OBJECTIVE
  To identify clastic cells on the root surfaces of torqued human premolars.
  
  
  METHODS
  A continuous force of 600 cNmm was applied to upper first premolars in patients 13-16 years of age by using a precise biomechanical model with superelastic wires (NiTi-SE). The 28 teeth in 14 patients were divided into five groups (control [nonmoved], and moved for either 1, 2, 3, or 4 weeks) and processed for tartrate-resistant acid phosphatase (TRAP) histochemistry and transmission electron microscopy.
  
  
  RESULTS
  Mononuclear TRAP-positive cells appeared at 2 weeks, where as large multinucleated TRAP-positive cells were numerous at 3 and 4 weeks. Ultrastructural examination revealed many clastic cells in contact with resorption lacunae. In addition, some cementoblast-like cells appeared secreting new cementum over previously resorbed lacunae.
  
  
  CONCLUSIONS
  In general, resorption lacunae and the number of clastic cells, which increased with the duration of the applied force, were found on the cementum surface at the pressure areas. Some signs of cementum repair were also noticed, even with the maintenance of the level of the force.
authors.affiliation: Mineralized Tissue Biology, University of São Paulo, São Paulo, Brazil.
authors.forename: Mauricio A
authors.initials: MA
authors.lastname: Casa
authors.forename: Rolf M
authors.initials: RM
authors.lastname: Faltin
authors.forename: Kurt
authors.initials: K
authors.lastname: Faltin
authors.forename: Victor E
authors.initials: VE
authors.lastname: Arana-Chavez
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000293:Adolescent; D001641:Bicuspid / Q000293:injuries*; D025021:Cementogenesis; D003739:Dental Cementum / Q000293:injuries / Q000473:pathology; D003799:Dental Stress Analysis; D004548:Elasticity; D006651:Histocytochemistry; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D009969:Orthodontic Wires / Q000009:adverse effects*; D010010:Osteoclasts / Q000473:pathology; D010513:Periodontal Ligament / Q000293:injuries* / Q000473:pathology; D012391:Root Resorption / Q000209:etiology / Q000473:pathology*; D013314:Stress, Mechanical; D000071681:Tartrate-Resistant Acid Phosphatase; D014087:Tooth Movement Techniques / Q000009:adverse effects*; D019415:Torque
chemical_list: D007527:Isoenzymes; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase