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  • Küçük Resim Yok
    Öğe
    The effects of therapeutic x-ray doses on mechanical, chemical and physical properties of poly methyl methacrylate
    (Taylor & Francis Ltd, 2013) Dogan, Derya Ozdemir; Ozguven, Yildiray; Karakus, Gulderen; Sahin, Onur; Polat, Nilufer Tulin; Yucel, Birsen; Dogan, Mansur
    Aim. The aim of this study was to investigate the effect of radiation doses very close to the human dose for oral cancers on mechanical, chemical and physical properties for poly methyl-methacrylate (PMMA). Methods. PMMA samples were divided into four different groups: no irradiated group, 25-Gy irradiated group, 50-Gy irradiated group and 75-Gy irradiated group. Each group contained nine samples. After 24 h, a three-point loading test was applied to each PMMA groups. The transverse strength and the elastic modulus were calculated using the test results. The results were analyzed statistically by using one-way analysis of variance. The structural characterizations of the PMMA samples were carried out by a Fourier Transform Infrared (FTIR) spectrophotometer to evaluate the chemical structure differences. Results. The transverse strength values of 25-Gy, 50-Gy and 75-Gy radiation groups were significantly higher than that of the no radiation group (p < 0.05). There was no significant difference among the elastic modulus values of the study groups (p > 0.05). The FTIR findings demonstrated that the irradiation process did not change the chemical structure of the PMMA polymeric materials. Conclusion. The therapeutic radiation doses increase the mechanical properties of the PMMA; however, the chemical and structural properties have no effect. When the findings of this study are taken into account, it can be said that patients can wear dentures during the radiotherapy.
  • Küçük Resim Yok
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    Evaluation of rapid maxillary expansion or alternating rapid maxillary expansion and constriction on Eustachian tube function with audiological tests: A randomized clinical trial
    (Elsevier Ireland Ltd, 2023) Buyukbayraktar, Zeynep Coban; Dogan, Mansur; Doruk, Cenk; Ozel, Volkan Yuksel
    Objectives: Maxillary expansion improves the hearing function. This trial aimed to examine the effects of Eustachian tube function (ETF) with audiological tests in orthodontic patients who underwent rapid maxillary expansion (RME) or alternate rapid maxillary expansion and constriction (Alt-RAMEC) treatment.Methods: Forty individuals (mean age = 13.35 years) included in the trial had a healthy eardrum, no history of orthodontic treatment, maxillary constriction, mandibular constriction and were not affected by acute or chronic otitis. Patients were randomly assigned to one of two groups (n = 20 each): the RME protocol or the Alt-RAMEC protocol. ETF was evaluated using Williams' test at three time points: before expansion (T0), after expansion (T1), and in the 3rd month of retention (T2).Results: In the RME group, Eustachian tube dysfunction (ETD) was observed in 18 of 40 ears before expansion (T0). The RME group showed significant improvement in tube function in the 3rd month of retention (T2) (p = 0.003). In the Alt-RAMEC group, ETD was observed in 22 of the 40 ears at baseline (T0). Significant improve-ments in tubal function were observed in the Alt-RAMEC group after expansion (T1) (p = 0.008) and in the 3rd month of retention (T2) (p < 0.001). In the RME group, 17 of 18 ears recovered, while in the Alt-RAMEC group, 21 of 22 ears recovered.Conclusion: Eustachian tube function improved in the RME and Alt-RAMEC groups compared to the pre-expansion period.Registration: This trial was not registered.