[ effect of vitamin A on orthodontic tooth movement in male rat]

It has been reported that, administration of excessive vitamin A can lead to profound effects on bone. This vitamin can induce bone degradation by stimulating the formation of mature osteoclasts from precursors. This study was designed to determine the effect of vitamin A on orthodontic tooth movement [OTM] using animal model. A total of 80 male Wister rats were included in this clinical trial. They were divided into eight equal groups. Orthodontic appliances were applied in all the eight groups to deliver an initial force of 60gr for 14 days on the first molar tooth. Six different doses of vitamin A were prepared. In addition to study groups, two control groups were considered as well. One control groups received daily intraperitoneal injections of olive oil and the other did not. Five rats were considered as normal base which received neither appliance nor injection and they were used for histological comparison with all groups. Study groups received 250, 500, 750, 1000, 1750, 2500 IU/Kg doses of vitamin A intraperitoneally each day. OTM was measured at the start and at the end of the study. Blood samples were taken from the heart, and the level of serum alkaline phosphatase was evaluated. After sacrificing the animals, cross-sections of maxilla were prepared by H and E and histological assessments were performed. The descriptive data was analyzed with SPSS version 11 and results were presented by mean and standard deviations. Group differences were analyzed by using One-way ANOVA, followed by Tukey, Kruskal-Wallis and Chi-Square tests. From the eight groups studied the highest amount of OTM was observed in the 2500 IU/Kg group and the least OTM was demonstrated in the 250 IU/Kg study group. Histological assessments showed no difference between vitamin A-treated and control groups. No difference was demonstrated between the groups when comparing the number of osteoclasts, cementoclasts, PDL width, root resorption, and serum alkaline phosphatase [P>0.05]. However significant difference was observed between normal base group and the other eight study groups. Based on the results of this study, despite reported effect of vitamin A on bone tissue, it did not accelerate alveolar bone remodeling and therefore did not change the process of orthodontic tooth movement

Histologic comparison of Bio-Oss and Neo-Oss in bone regeneration of experimental defects on rabbit calvarium

Several biomaterials have been presented for regeneration of intraosseous defects and Bio-Oss is one of the most accepted materials in this field. Neo-Oss may be the first and only regenerative material made in Iran which few studies have been published about it. The aim of this study was the histologic evaluation of Neo-Oss in comparison with Bio-Oss in experimental rabbit calvarial defects. This was an interventional in vivo study. After elevating muccoperiosteal flap 18 standard defects [3X6mm] in frontal and parietal bone were made by round bur on the calvarium of 6 New Zealand rabbits. Defects were randomly assigned to one of the following treatments: 1-No graft [control], 2-Bio-Oss graft 3-Neo-Oss graft. After 4 weeks the animals were killed and histologic sections prepared. The studied variables consisted of inflammation, type of regenerated bone, thickness of bony trabeculation and foreign body reaction. Data were analyzed by Friedman test with p<0.05 as the limit of significance. The results showed that Bio-Oss was effective for bone regeneration. Inflammation [P= 0.026] and foreign body reaction [P= 0.002] in Neo-Oss was significantly more than Bio-Oss group. Thickness of terabecula in Neo-Oss group [66.7% thin] was significantly different from Bio-Oss [100% thick] and control group [50% thin 50% thick] [P= 0.006]. In Neo-Oss group, granulation tissue containing giant cells was observed and the rate of resorption during 4 weeks was high. Based on the results of this study, the healing capacity of Neo-Oss in comparison with Bio-Oss is not acceptable

effect of bevel angle on apical microleakage following the use of amalgam and MTA

Achieving appropriate seal in canal obturation is the main goal of endodontic therapy. However, in some cases, it can not be obtained by non-surgical procedures alone. Retrograde surgery is one of the most common procedures in endodontics. Apical seal improvement can be obtained by root end filling and decreasing the root end resection angle [bevel angle]. The aim of this study was to investigate the role of bevel angle on apical microleakage following the use of amalgam and MTA as root end filling materials. In this experimental study, 128 extracted human teeth were instrumented and obturated by lateral condensation technique. The teeth were divided into two groups and the apical root resection was performed by high speed fissure bur one group perpendicular to the long axis of the teeth and the other 45° to the long axis. The 3 mm root end cavity was prepared by ultrasonic device. Each group was divided into two subgroups: One filled with amalgam and the other with MTA. Teeth were incubated for 72 h, covered by two layers of nail polish [except for apical 3mm] and submerged in methylene blue for 48 h. Teeth were washed under tap water and mesiodistally dissected by low speed disc. Dye penetration was evaluated by stereomicroscope. Data were analysed by two way ANOVA and Tukey tests with p<0.05 as the limit of significance. The results showed that retrofill material type had a significant effect on microleakage and MTA was superior to amalgam in this respect. Bevel angle failed to show any significant effect on apical microleakage. Based on the results of this study, it seems that the use of MTA instead of amalgam in clinical practice can improve the success rate of endodontic surgery whereas the bevel angle can be determined based on the status of each individual case; However, increasing the bevel angle seems to increase microleakage due to exposure of more dentinal tubules