Periodontitis is one of the most highly prevalent chronic diseases worldwide. Periodontal disease, along with severe dental caries, causes tooth loss, which result in reduced functional capacity, selfesteem and social relationships. Hence, it affects people's quality of life .Periodontitis is associated with several risk factors among which, is tobacco smoking. (3) Throughout the years, studies has recorded delirious effect of smoking on periodontal tissues. However, there were different selected populations and /or different methodologies among these studies. In addition, the precise mechanism by which tobacco influences periodontal destruction and its related alteration still need complementary investigation (4,5,6) . It has been observed that smoking can alter salivary fluid, salivary enzymes. Yet, only a few studies has recorded the effect of tobacco smoking on salivary immunoglobulin (7,8)
Objective: This study was performed to reveal the physical changes of polymers used after gamma irradiation of a modified twin block appliance versus conventional twin block appliance in the treatment of growing females with skeletal Class II malocclusion having mandibular deficiency. Materials and methods: The total sample consisted of 12 specimens 6 from every polymer, modified twin block group which was composed of polyethylene polymer and conventional twin block group which was formed of poly methyl-methacrylate polymer used in this study, exposed to different gamma irradiation doses (25 KGray and 30 KGray) in order to test their physical properties. Assessment was done using UV-visible spectroscopy and scanning electron microscope. Results: This study revealed that concerning the gamma radiation effect on the polymers used, Poly methyl methacrylate showed yellowish color change and increased number of pores on its surface after irradiation while polyethylene vacuum sheets didn’t show any color change but the scratches and pores appeared on its surface using scanning electron microscope. Conclusion: From the previous results it can be concluded that the modified twin block appliance can be used as an alternative orthopedic appliance in treatment of skeletal class II malocclusion growing subjects with mandibular retrusion.
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