title: Biological reaction of alveolar bone to orthodontic tooth movement.
abstract: Direct and indirect resorption are perceived as reactions to an applied force. This is in contrast to the view of orthopedic surgeons, who describe apposition as a reaction to loading of bone. A histomorphometric study of the circumalveolar bone reaction to a force system generating translation of premolars and molars of five maccaca fascicularis monkeys is described. Three force levels (100 cN, 200 cN, and 300 cN) were applied for a period of 11 weeks. Undecalcified serial sections were cut parallel to the occlusal plane, and a grid consisting of three concentric outlines of the root intersected by six radii was placed on each section. Areas anticipated to be submitted to different stress/strain distributions were isolated. A-posteriori tests were used in order to separate areas that differed with regard to parameters reflecting bone turnover. Based on these results, a new hypothesis regarding tissue reaction to orthodontic forces is suggested. Direct resorption could be perceived as a result of the lowering of the normal strain from the functioning PDL and as such, as a start of remodeling, in the bone biological sense of the word. Indirect remodeling could be perceived as a sterile inflammation attempting to remove ischemic bone under the hyalinized tissue. At a distance from the alveolus, dense woven bone was observed as a sign of a RAP (regional acceleratory phenomena). The apposition could, according to the new hypothesis, be perceived as a result of the bending of the alveolar wall produced by the pull from the Sharpey fibers. The above suggested interpretation of tissue reaction would be shared with bone biologists.
authors.affiliation: Department of Orthodontics, Royal Dental College, Aarhus University, Denmark. orthodpt@odont.aau.dk
authors.forename: B
authors.initials: B
authors.lastname: Melsen
mesh_terms: D000222:Adaptation, Physiological; D016301:Alveolar Bone Loss / Q000209:etiology* / Q000503:physiopathology; D000539:Alveolar Process / Q000473:pathology / Q000502:physiology* / Q000503:physiopathology; D000704:Analysis of Variance; D000818:Animals; D015519:Bone Density; D016723:Bone Remodeling; D019245:Compressive Strength; D003799:Dental Stress Analysis; D008252:Macaca fascicularis; D009969:Orthodontic Wires / Q000009:adverse effects; D010513:Periodontal Ligament / Q000503:physiopathology; D014087:Tooth Movement Techniques / Q000009:adverse effects*