title: Orthodontically stressed periodontium of transgenic mouse as a model for studying mechanical response in bone: The effect on the number of osteoblasts.
abstract: A better understanding of cellular and molecular mechanisms involved in response to mechanical stress is a prerequisite for future improvements in orthodontic treatment. To expand the application of molecular biology techniques in this area of research, we developed and characterized a mouse tooth movement model. The aim of this study was to biomechanically characterize this model and to evaluate the effect of orthodontic stress on the proliferation of periodontal osteoblasts. We used an orthodontic coil spring appliance with a low force/deflection rate, which produced an average force of 10-12 g. This design provided a predictable tipping movement of the molar with the center of rotation at the level of root apices. Histological observations of paradental tissues revealed a response favoring a fast onset of tooth movement and deposition of new osteoid starting after 3 days of treatment. The effect of treatment on the histomorpometric parameter of the number of osteoclasts per unit bone perimeter was determined after 1, 2, 3, 4, 6, and 12 days of treatment. Starting with day 2, the osteoblast number showed a modest but consistent increase in treated periodontal sites at all time-points, ranging from 14 to 39% and becoming significant only at day 6. Only a moderate increase in the number of osteoblasts in the areas of otherwise intense bone matrix synthesis suggests that, during bone formation, proliferation of cells has a smaller role compared to a marked increase in differentiation of individual cells. The mouse model, which allows for a controlled, reproducible, orthodontic mechanical loading, can be applied to both wild-type and transgenic animals and should enhance the research of the transduction of mechanical orthodontic signal into a biological response.
authors.affiliation: Department of Orthodontics, The University of Texas Health Science Center at San Antonio, TX; Department of Orthodontics, Ohio State University College of Dentistry, OH; Department of Laboratory Medicine, Clinical Hospital Center, University of Zagreb, Croatia.
authors.forename: Dubravko
authors.initials: D
authors.lastname: Pavlin
authors.forename: Eric S.
authors.initials: ES
authors.lastname: Goldman
authors.forename: Jelica
authors.initials: J
authors.lastname: Gluhak-Heinrich
authors.forename: Marla
authors.initials: M
authors.lastname: Magness
authors.forename: Renata
authors.initials: R
authors.lastname: Zadro