We investigated the effect of different force magnitudes on osteocyte apoptosis in a model of orthodontic tooth movement. Forty-nine male Sprague Dawley rats (7-9 wk of age) were divided into light- and heavy-force groups (n = 21 each group) and a control group (n = 7). A coil spring delivered pressure (either 10-15 g or 20-25 g) to the left maxillary first molar. The rats were sacrificed 1, 3, or 5 d after placement of the appliance. Sections of the maxillary first molars were immunostained for caspase-3. Upon force application, the number of apoptotic osteocytes significantly increased in the pressure side at 1 d and remained the same at 3 d and 5 d. However, there was no significant difference in the number of apoptotic osteocytes between the two force groups. We conclude that osteocyte apoptosis appears to increase under orthodontic loading, reaching a plateau after 1 d. However, osteocyte apoptosis seems to be independent of the magnitude of orthodontic forces tested.

INTRODUCTION:Significant development has been achieved with bioceramics and biopolymer scaffolds in the construction of artificial bone. In the present study, Chitosan-nanohydroxyapatite (CS/nHA) scaffolds have been developed as bone graft substitutes in rabbits with induced osteoporosis. OBJECTIVES: To evaluate the effect of Chitosan-nanohydroxyapatite (CS/nHA) scaffold in bone tissue regeneration of extracted socket in rabbits with induced osteoporosis; using Scanning Electron Microscope and Energy Dispersive x-ray analysis [EDXA]. MATERIALS AND METHODS: Twenty NewZealand white female rabbits were randomly divided into 2 equal groups; group A (osteoporosis) with no graft material, and group B (osteoporosis with CS/nHA). After the experimental period the animals were sacrificed at 2 & 4 weeks. The effect of CS/Nha was evaluated using Scanning Electron Microscope and Energy Dispersed x-ray analysis [EDXA]. The data obtained was tabulated and subjected to statistical analysis. RESULTS: Scanning Electron Microscopic results revealed more trabecular bone thickness with regular bone surface, and uniform osteocyte lacunae in the group B (osteoporosis with CS/nHA) than group A (osteoporosis), and these results were proved by EDXA which showed more Ca and P ratio in the group B than group A. CONCLUSIONS: CS/nHA scaffold is considered an effective hard tissue engineering material with sufficient interconnected porosity and mechanical strength to allow cell adhesion, migration, growth and proliferation resulting in good integration with surrounding tissues, and rapid bone healing, thus it might be used in osteoporotic condition.

INTRODUCTION: Tooth bleaching has proven to be a conservative esthetic solution for tooth discoloration, hydrogen peroxide (HP) is used as an active oxidizing agent for tooth whitening; it can be used either directly or indirectly by chemical reaction from carbamide peroxide (CP). So many patients suffer from discomfort and sensitivity during and after the bleaching procedure. The use of fluoride shows to be beneficial in reducing the adverse effects of bleaching on Enamel. OBJECTIVES: The study was designed to evaluate the effect of fluoride incorporation in bleaching agents on enamel surface properties. MATERIALS AND METHODS: twenty sound human premolars extracted for orthodontic reasons were selected for the study. The selected premolars were randomly divided into 2 equal groups (10 teeth per group) as follows: Study Group I: The teeth were bleached using 10% Carbamide peroxide. Study Group II: The teeth were bleached using 10% CP containing 0.11% fluoride. All the specimens were examined by scanning electron microscopy (SEM) and micro-hardness test. RESULTS: after 14 days erosion pattern was noted in teeth from group 1 while the teeth of group 2 showed milder demineralization, group 1 showed significant decrease in micro-hardness compared to the base line whereas group 2 teeth that were treated with fluoridated bleaching agent showed insignificant reduction in micro-hardness. CONCLUSIONS: incorporation of fluoride in bleaching agents reduces the adverse effects of bleaching on the enamel surface.