ABSTRACT
Different cements are used to attach orthodontic bands which require special considerations in terms of technique sensitivity during setting reaction, water solubility and decomposition over time each of which may result in attachment failure, decalcification and caries in long term. This study was designed to assess the weight changes of different zinc phosphate and polycarboxylate cements used in orthodontics. An experimental study was designed to compare two available conventional cements [zinc phosphate and polycarboxilate] in the department of dental materials, SBMU School of Dentistry, Tehran, Iran. The cements were categorized according to ADA 8 index and the data were analyzed with electronic balance. Weight variations were recorded after 6 weeks floating the samples in water and data were subjected to analysis using Repeated Measured ANOVA test. There was the maximum mean value of weight loss for Aria Dent zinc phosphate cement and the least with Adhezor zinc phosphate within the period of study. Regarding plycarboxylate cement, Aria Dent polycarboxylate displayed the greater weight variation over the time compared to other conventional cement and the minimum value of weight loss was for Durelon cement. It is concluded that Aria Dent zinc phosphate and polycarboxylate cement display greater weight variations over time compared to other conventional cements
ABSTRACT
The orthodontic force-induced tissue strain produces local alterations in cellular and extracellular matrix reorganization, leading to the transformation and differentiation of cells. The present study was designed to investigate the influence of mechanical force on the CD90 expression of human mesenchymal stem cells [endometrial stem cells and dental pulp stem cells]. The mesenchymal stem cells from passage 3-5 were seeded onto silicone membrane and cultured in medium with or without static mechanical stimulation [equiaxial and uniaxial strains]. After 2 weeks, cultured cells were analyzed for expression of CD90. After 14 days in culture, immunfluorescence staining of cultured MSC demonstrated that mechanical stimulation of MSCs compared with control group, resulted in decreased CD90 expression. The decrease of CD90 expression in mechanically stimulated cultures compared to unstimulated control cultures suggests the possibility of differentiation of stem cells to other cells
ABSTRACT
Bone tissue engineering is an alternative strategy to generate bone utilizing a combination of biomaterials and cells. Bioactive porous three-dimensional scaffolds play important role in promotion of cellular proliferation and differentiation in tissue regeneration. In this study, in order to preparing of bone tissue engineering scaffold with good biocompatibiliry,bioactivity and physicochemical properties; we constructed porous three-dimensional chitosan-gelatin/hydroxyapatite and chitosan-gelatin/[beta-TCP composite scaffolds containing different amounts [0, 10, and 20wt.%] of gelatin through freeze-drying method. A novel bioactive ceramic/chitosan-gelatin network [HA- beta-TCP /CS-Gel] was prepared as a three-dimensional biomimetic scaffold by freeze-drying method. Composite scaffolds of chitosan [CS]-gelatin [CG] with Hydroxyapatite and beta-TCP were prepared by freez-drying of chitosan and gelatin[0%-10%-20%]- HA and beta -TCP. The prepared Chitosan-gelatin/ceramic composite scaffolds were characterized using SEM and FTIR studies. The effect of gelatin and beta-TCP in the scaffold matrix were evaluated in terms of scaffold properties. .In addition swelling ratio, porosity measurement of the composite scaffolds were studied. Our SEM results showed macroporous internal morphology in the scaffold with pore size ranging from 96to 206 micro m. Swelling behavior of the interconnected network showed the increasing of porosity with rising gelatin. The porosity decreased with increasing concentration of gelatin from 10% to 20%. Also due to the higher solubility rate of beta-TCP, the porosity, pore size and swelling rate with the addition of beta-TCP increased. FTIR studies showed the strong interaction between ceramic and chitosan-gelatin network. The results indicated that Chitosan-gel- HA scaffolds, fully interconnected with high porosity structure, thoroughly open pores and tailored pore size which prepared by freez-drying method is very similsr to bone structure therefore it is suitable scaffold for bone tissue engineering
ABSTRACT
Nowadays, there is great emphasis on the commitment of dentists as health care workforce, thus, awareness of their motivations and expectations is important in order to promote general and oral health. The aim of the present study was to evaluate dental post graduate student s motivations and career choice plans in relation to sex, marital status and parent s education in Shahid Beheshti University of Medical Sciences, Tehran, Iran in 2009-2010. A total of 1 16 dental post graduate students have been participated in this survey and a valid and reliable questionnaire was designed in three sections based on previous studies consisting of motivations and career choice plans and was distributed among them. Data were entered in to SPSS [16] and were analyzed with Mann Whitney test. Social/occupational prestige was the most important motivation [%92]. On the other hand, there was significant association between motivations and career choice plans with marital status and parent s job as dentist/physician. Influence of family had significantly more impact among residents who had dentist/physician parents compared to those with parents in other occupations [p=0.01 1] [%65]. The most important career choice plan was to work in private sector [94/84%]. The married people were inclined to constitute a professional dental clinic with colleagues [p<0.0037] [%86]. Single students had more interest in research in the field of dentistry [p=0.047]. The most important motivations were social/ occupational prestige, income, independence and personal interest in dentistry respectively. The most important career choice plans were working in private sector, recruitment in university as dental faculty and constitution a professional dental clinic with colleagues
ABSTRACT
Together with the increase of orthodontic treatment needs the use of functional apparatus has been increased. Furthermore, different studies has been done on skeletal and dental changes after the use of these functional appliances, but few studies discussed soft tissue changes in the field. So, this study was carried out in order to evaluate soft tissue changes following the use of Twin Block functional appliance. This study was quazi experimental done on 13 patients [7 girls and 6 boys] with 7 years and 7 months to 12 years and 6 months of age. All patients were Cl II Div.l malocclusion, Iranian, Muslim, resident of Tehran and with no previous orthodontic treatment and tooth extraction. The period of treatment with the apparatus varied between 7 to 17 months. The studied angular variables were nasolabial, nasofacial, facial convexity, H angle, mentocervical, nasomental and mentolabial. The liner variables were lower and upper lip to E - line, upper and lower lip thickness, prominence and length, upper and lower face height. All variables were compared before and after the use of Twin Block and recorded in a questionnaire and were analyzed by T - test. The study showed that nasolabial, nasofacial, Lower lip to E line and Upper lip length decreased slightly with the use of apparatus, while facial convexity, H angle, upper lip prominence, upper lip thickness and upper lip to E line decreased significantly. As well as, mentocervical, upper lip thickness, lower lip prominence and soft tissue lower face height increased slightly and nasomental, mentolabial, soft tissue upper face height and lower lip length increased significantly. Following the treatment with Twin Block, the lower face soft tissue moved anteriorly leading to decrease in profile convexity. The upper and lower face soft tissue height increases and their ratio improved. The upper and lower lip thickness reduced, but upper lip length did not change and lower lip length increased after the treatment. The space between upper and lower lip edge to E - line moved to a normal range and labiomental fold became wider