title: Ultrastructure of cementum and periodontal ligament after continuous intrusion in humans: a transmission electron microscopy study.
abstract: An ultrastructural study of the cementum and periodontal ligament (PDL) changes after continuous intrusion with two different and controlled forces in humans was carried out. Twelve first upper premolars, at stage 10 of Nolla, orthodontically indicated for extraction from six patients (mean age 15.3) were used. They were divided into three experimental groups, distributed intra-individually as follows: control (not moved), continuously intruded for 4 weeks with 50 or 100 cN force, utilizing a precise biomechanical model with nickel titanium super-elastic wires (NiTi-SE), which were developed and calibrated individually. The teeth were extracted, fixed, decalcified, and conventionally processed for examination in a Jeol 100 CX II transmission electron microscope. Evident signs of degeneration of cell structures, vascular components, and extracellular matrix (EM) of cementum and PDL were observed in all the intruded teeth, with more severe changes towards an apical direction and in proportion to the magnitude of force applied. Resorptive areas and an irregular root surface of the intruded teeth were noticed, according to the same pattern described above. Concomitant, areas of repair were also revealed in the cementum and PDL although the magnitude of forces remained the same throughout the experimental period. Thus, a reduction of continuous force magnitude should be considered to preserve the integrity of tissues.
authors: Laboratory of Mineralized Tissue Biology, Department of Histology and Embryology, Institute of Biomedical Sciences, University of São Paulo, Brazil.
authors: R M
authors: RM
authors: Faltin
authors: K
authors: K
authors: Faltin
authors: F G
authors: FG
authors: Sander
authors: V E
authors: VE
authors: Arana-Chavez
mesh_terms: D000293:Adolescent; D001641:Bicuspid / Q000648:ultrastructure; D001696:Biomechanical Phenomena; D003094:Collagen / Q000648:ultrastructure; D003722:Dental Alloys; D003739:Dental Cementum / Q000648:ultrastructure*; D004548:Elasticity; D004730:Endothelium, Vascular / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000648:ultrastructure; D005347:Fibroblasts / Q000648:ultrastructure; D006801:Humans; D008264:Macrophages / Q000648:ultrastructure; D008854:Microscopy, Electron; D009532:Nickel; D009969:Orthodontic Wires; D010513:Periodontal Ligament / Q000098:blood supply / Q000648:ultrastructure*; D012391:Root Resorption / Q000473:pathology; D013193:Stainless Steel; D013314:Stress, Mechanical; D014025:Titanium; D014087:Tooth Movement Techniques / Q000295:instrumentation
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D003094:Collagen; D014025:Titanium