مجله دانشکده دندانپزشکی مشهد
سال سی و هفتم شماره 3 (پیاپی 86، پاییز 1392)

This study aims at comparing and analyzing the shear bond strength of the two zirconia cores on two porcelains proposed by the manufacturing company in two systems of VITA and IVOCLAR In this laboratory study, at first, the tooth-like brass sample was made by the CNC machine. Then, using the CAD CAM machine, 20 zirconia cores of Vita in Ceram YZ Cubes and 20 zirconia cores of IPS e. max zirCAD were provided. Half of the cores were provided using Vita VM9 porcelain and the other half were veneered with the use of IPS e. max ceram. In groups one to four, Vita Core and Veneer, Vita Core and Ivoclar Veneer, Ivoclar Core and Vita Veneer, and Ivoclar Core and Veneer were used respectively. Afterwards, the samples were put under the static force in the Universal Test machine (UTM) with the speed of 0/5 mm per minute to bring about fracture. The type of fracture was determined by electronic microscope. Schmitz-Schulmeyer Test was applied to evaluate the shear bond strength of core-veneer. In order to analyze the data, Two-Way ANOVA and logestic regression were carried out using SPSS 19 (α=0. 05). The rate of shear bond strength for groups one to four were 10.85±2.67, 10.35±3.30, 10.35±3.30 and 6.72±2.47 mega pascal respectively. The type of core had no effects on shear bond strength (P=0. 869), but the veneer kind was important in the rate of shear bond strength (P=0.027). The Vita veneer showed a higher level of shear bond strength. After the microscopic evaluation, samples showed a combination of the cohesive fracture at the veneer layer and mixed (cohesive, adhesive) fracture at the edge of the two layers; No adhesive fracture between the zirconia cores and veneers was observed. The results show that the shear bond strength of zirconia core and the covering porcelain veneers and the fracture type are not influenced by the core type, but are affected by the type of veneer.

Diagnosing the necessity of cavity preparation and restoration in demineralized proximal areas is always considered as a challenge in restorative treatment planning. The purpose of this study was to assess the performance of the laser fluorescence (LF) technique in detection of proximal cavities. In this clinical trial, 44 proximal surfaces in 38 dental students were evaluated. The selected patients had radiolucent proximal lesions restricted to inner half of enamel or outer third of dentine in bitewing radiographs (BW). DIAGNOdent pen (LF pen) device was used to determine the presence or absence of caries cavities in suspected proximal surfaces. Orthodontic elastic separators were then placed in the contact areas to provide enough space for direct visual and tactile examination. The sensitivity, specificity and accuracy of the laser fluorescence technique were calculated versus the reference standard. The ROC curve was drawn and the best cut-off to determine the presence or absence of proximal cavities was determined. Using DIAGNOdent pen, the optimal cut-off for detecting proximal cavities was 18. The sensitivity, specificity and accuracy of DIAGNOdent pen for diagnosing proximal caries cavities were 100 per cent, 97.3 per cent and 97.7 per cent, respectively. Due to the high diagnostic accuracy of DIAGNOdent pen in detecting proximal caries cavities, it can be used as a valuable supplement in restorative treatment planning.

Following the renal disease involvement, some variations may occur in the flow, pH and biochemical components of the saliva; therefore, saliva possibly would be a useful tool for diagnosis and monitoring of the renal disease through evaluation of the components. The aim of the present study was to analyse the biochemical composition of the saliva in patients undergone haemodialysis for the end-stage renal disease (ESRD) in Imam Khomeini Hospital. In this descriptive cross-sectional study, 64 haemodialysis patients and 67 healthy individuals were selected and their salivary samples were obtained by spitting method. Salivary biochemical factors were determined by serum kits and auto-analyzer while the samples’ pH was determined by an automatic pH meter. Then, Creatinine, Ca, Mg, urea, α-amylase parameters as well as the salivary flow rate were measured. The saliva biochemical compositions were analyzed using Student t test. The mean (± standard deviation) of the salivary flow rate was statistically lower in ESRD patients than healthy ones (0.34±0.22 ml/min vs. 0.57±0.29 ml/min: P<0.001). Salivary pH (7.87±0.72 vs. 6.99±0.4: P<0.001) and concentrations of urea (134.4±40.8 vs. 40.8±15.1 mg/dl: P<0.001); Cr (1.1±0.9 vs. 0.4±0.1 mg/dl: P<0.001) and α-amylase (1107.4±788.4 vs. 568.3±437.0 mg/dl: P<0.001) were statistically higher in ESRD patients than healthy controls. Ca was significantly lower in ESRD patients than healthy ones (2.8±2.8 vs. 3.6±2.0 mg/dl: P<0.05).). No significant differences were noted between both groups regarding salivary Mg. The mean (± standard deviation) age was statistically higher in ESRD patients than healthy ones (63.2±15.4 years vs. 48.2±15.3 years: P<0.001). No significant differences were noted between both groups regarding weight and gender. Due to the significant alternations of the salivary biochemical concentrations in ESRD patients; saliva can be used as a diagnostic tool for monitoning the involvement of the renal diseases.

In esthetic dentistry, colormatching ability is one of the influencing factors in treatment. To achieve this goal, matching the color of restoration with natural teeth is essential. The objective of this study was to determine the frequency of color vision defectin students of Mashhad Dental School and evaluation of related factors. In this descriptive analytical study, 356 students of Mashhad Dental School were evaluated. Demographic data including age, gender, color vision defect in relatives, use of glasses and contact lenses, refractive errors (myopia, hypermetropia and astigmatism) were documented in the designed questionnaire. To determinethe impaired color vision, Ishiharadiagnostic test was used. Statistical analysis of SPSS version 19 was performed usingChi-Square and Logistic Regression tests at the significance level of 0.05%. Color vision defect was foundin6% (12 persons) of male students while none of the females were affected. Allaffected personswere red-green color blind and strong deutan. There wasa significant relationshipbetween color vision deficiency and history of color vision defect in relatives (P= 0.03), so that 25% (3 persons) of affected persons had a positive family history of color vision defect. Considering the frequency of color vision defect in the present study as well as the importance of color matching in dental treatments and because most affected persons are unaware of this defect, color vision tests seem necessary.

The treatment of pulpal necrosis in an immature tooth with an open apex presents a unique challenge to the dentist. Revascularization is a new treatment procedure for the management of these cases. This study examined the ability of demineralized bone matrix as a scaffold to aid pulp revascularizaion of immature cat teeth. Sixteen immature teeth from 4 cats after preparation of access cavity and cleaning of canals, were placed into two groups; control group containing blood in canal and experimental group containing blood + demineralized bone matrix. Teeth were treated with revascularization technique and cats were followed up for four months. Then periapical radiographs were taken and analyzed for presence of apical radiolucencies, apical closure and thickening of root canal walls. The data were statistically analyzed using Fisher's exact test. 0.05 was established as a level of significance. The two groups showed no statistical difference regarding presence of apical radiolucencies, apical closure and thickening of root canal walls. In control group, none of the teeth showed any apical radiolucencies and 75% of teeth showed apical closure and thickening of root canal walls. In experimental group, none of the teeth showed any apical radiolucencies, 90.9% of teeth showed apical closure and 81.8% showed thickening of root canal walls. Based on the results of this study, the demineralized bone matrixes do not have adverse effect on revascularization procedure and can be used as a scaffold in this technique.

Nitric oxide (NO) and epidermal growth factor (EGF) play an important role in biologic systems. The aim of the present study was to evaluatesalivary NO and EGF levelschanges in type I and II diabetes mellitus comparing to the control group. In this cross-sectional study, five ml saliva of 20 patients with type 1 diabetes mellitus and five ml saliva of 20 patients with type 2 diabetes mellitus attended to Hamadan diabetes research center as well as 20 healthy individuals matched according to age and sex, were collected. NO and EGF were assessed via Griess reaction and Immunoassay methods respectively. Data were analyzed by t-test and Mann-Whitney test. Compared to the control group, the level of NO was increased in patients with type I diabetes (P=0.037), while it did not significantly increase in type II diabetes (P=0.058). The level of EGF in diabetic patients was significantly higher than the control group. There was no significant difference between the salivary level of EGF and NO of patient with type 1 and type 2 mellitus diabetes (P>0.05). The correlation coefficient between NO and EGF levels in type II diabetic patients was -0.278 (P=0.0235). The level of NO and EGF was significantly related to fasting blood sugar and HbA1c (P=0.001). The level of salivary NO in type I diabetes and EGF in type I and II diabetes was higher compared to those of healthy individuals and was related to the severity of the disease.

In patients using dental prosthesis, growth of various microorganisms under the prosthesis base which leads to inflammation and infections such as candidiasis is common. The aim of this study was to assess the antifungal effects of acrylic resins containing silver nanoparticles on candida Albicans. To accomplish this in vitro study inorder to prepare acrylic samples, metallic cylindricals with a diameter of 10mm and thickness of 4mm were used. Forty samples as standard control group and 40 samples containing silver nanoparticles in four different concentrations were used.Immersion of samples in fungal suspension (standard and hospitally isolated) were carried out to accomplish antifungal tests.After 0,1,6 and 24 hours the fungal colonies were counted. To describe the data and to compare groups, student-t test was used. In the silver nanoparticles with 2.5% concentration, the highest mean difference for standard candida Albicans after 24 hours of exposure time was 501.0±23.1 and for 5% concentration after 6 hours of exposure time was 953±87 and for 10% concentration after 6 hours of exposure time was 1000±24.9. In acrylic resins, increasing both the silver nanoparticles concentration and the exposure time will increase the antifungal effect.

Chronic periodontitis is an infectious disease resulting in inflammation in tooth supporting tissues, advanced attachment loss and boneloss. Destructive process is a result of imbalance between analyzing enzymes suchas MMPs and their inhibitors. This imbalance can also occur with other enzymessuch as lysosomal cysteine proteinase, Katpsyn and their inhibitor such ascystatin. Cystatin C is a protein which controls activity of extracellular cysteineproteinase in inflammatory conditions. The aim of this study was to evaluatethe protective role of salivary cystatin C in periodental disease. Twenty six patients with chronic periodontitis examined by a periodontist andalso with a minimum pocket depth of six mm and more in at least eight locations inthe mouth were selected. To collect Totalnon-irritating saliva samples, the spitmethod was used. Salivary levels of cystatin C was evaluated by ELISA method. Data were analysed by SPSS version 11.5 software. The level of cystatin C in periodontally diseased subjects was higherthan that of the control group, but the difference was not statistically significant(P=0.24). In the female group with control of age variant, thelevel of cystatin C was significantly higher in patients with periodontitis (P=0.036), whereas in male group, the difference was not significant(P=0.086). It seems that the lower periodontal destruction in female group is as aresult of higher level of cystatin C. The level of cystatin C in whole saliva could be used as a marker in chronic periodontitis.

Periodic evaluation of educational programs provides insight into the course and teaching effectiveness. Effective evaluation provides valuable information, which contributes to both student’s and course success. The purpose of this study was to evaluate the success of pediatric dentistry department at Mashhad dental school in clinical education from students’ perspectives. This cross-sectional study was conducted on 116 fifth and sixth grade undergraduate dental students in pediatric dentistry at Mashhad dental school. A questionnaire including 21 multiple choice questions about 7 parts of clinical skills in pediatric dentistry was given to each student. Data were analyzed by Mann-Whitney in SPSS software. According to the study results, among 7 different clinical skills in pediatric dentistry including: examination, behavior management, prevention, injection, restoration, pulp treatment and space management, the highest success rate of pediatric dentistry department was in prevention and injection and the lowest success rate in space management and behavior control. Furthermore, from the students’ perspective, male students compared to female students mentioned a higher rate of success in choosing the type of restoration material for pediatric dentistry department (P=0. 041). This study showed that the students’ self-reported clinical skills in different parts of pediatric dentistry has been adequate. Students reported a lack of confidence in “behavior management” and “space management” which warrants greater emphasis in the undergraduate curriculum.

Fusion is a developmental anomaly in which two tooth buds are interconnected. In fusion, teeth are joined by dentine in their developmental stage. Fusion could be between normal teeth or between a normal and a supernumerary tooth. Fusion of the posterior teeth and supernumerary ones are rare. Case Report: A 26 year old woman was referred for extraction of semi impacted third molar. Panoramic radiographs were requested for the patient. In dental radiographs, a supernumerary tooth in distal region of the third molar was observed. Teeth looked like fused teeth. After obtaining consent from the patient, teeth were removed by surgical excision.