Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Orthodontics

This is an experimental animal study which was performed to study the histological effect of light versus heavy orthodontic force magnitudes on the vital dental tissues (cementum, dentin and pulp) using the fluorescent microscope and to evaluate the effect of such forces on the rate of orthodontic tooth movement. The sample consisted of ten dogs. Dogs were chosen as they could tolerate the different environmental conditions. The mandibular third premolars were extracted bilaterally and custom-made tubes casted on customized metal crowns for the 2nd and 4th premolars that were fabricated to allow the mandibular second premolars to move by sliding on a straight 1.5 mm stainless steel wire segment after force application by a readymade closed coil spring to deliver a force of 50 g at the left side and 350 g at the right side. The ten canine models were allocated into two groups, five dogs in each one. In the two groups(A and B), a split-mouth design was used .In the mandibular right side the applied orthodontic force used for the mandibular second premolar retraction was 350 g (considered as a heavy orthodontic force) and an orthodontic force of 50 g (considered as a light orthodontic force) was applied in the mandibular left side. Group A had received an intra-vital staining with two fluorochromes (Calcein at the second week and Alizarin red at the fourth week). Measurements of the amount of orthodontic tooth movement in both sideswere performed weekly. At day 28, the dogs were sacrificed and thespecimens from group (A) were prepared for un-decalcified histologicalexamination under the fluorescent microscope while the specimens of group(B) were prepared for decalcified histological examination using Haematoxyline and Eosin under the light microscope

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