Comparison of microleakage in Class II cavities restored with silorane-based and methacrylate-based composite resins using different restorative techniques over time.

BACKGROUND Despite the growing tendency toward tooth-colored restorations in dentistry, polymerization shrinkage and subsequent marginal microleakage remains a problem. The aim of this in vitro study was to compare microleakage between silorane-based and methacrylate-based composite resins at different time intervals and with different restorative techniques. MATERIALS AND METHODS In this in vitro study, 108 sound extracted human molar teeth were used. Mesial and distal proximal class II boxes with dimensions of 1.5 mm depth and 4 mm width were prepared. The gingival margins of all cavities were 1 mm below the cement enamel junction. The teeth were randomly divided into three groups based on test materials. In the first group, the teeth were restored by a nanocomposite (Filtek Z350XT, 3MESPE) and SE Bond adhesive (Kuraray, Japan), in the second group, the teeth were restored with a silorane-based (Filtek P90, 3MESPE) and Filtek P90 Adhesive (3M ESPE, USA) and in the third group, the teeth were restored with a microhybrid posterior composite resin (Filtek P60, 3MESPE) and SE Bond adhesive (Kuraray, Japan). Half of the proximal cavities in each of these three groups were restored in two horizontal layers and the other half in four horizontal layers. After a period of aging (24-h, 3-month and 6-month) in water and then application of 500 thermal cycles, the teeth were immersed for 24-h in 0.5% fuchsin and evaluated under a stereomicroscope at ×36 magnification to evaluate leakage in gingival margin. Data was statistically analyzed using Kruskal-Wallis and Mann-Whitney U-tests. P ≤ 0.05 was considered as significant. RESULTS In Z350XT statistically significant differences were observed in microleakage in comparison of 24-h and 6-month intervals (P = 0.01) that was higher in 6-month. Comparison of microleakage in P90 and P60 composite resins was also statistically significant and was less in P90. Microleakage was not significantly different between P90 and Z350XT at 24-h. However, this difference was significant at 3-month and 6-month intervals. Differences in microleakage of P60 and Z-350XT composite resins were not statistically significant in all intervals (P = 0.38). P90 showed the lowest microleakage during storage in water. Z350XT had microleakage similar to P90 within 24-h, but after 6-month of storage in water, it showed the highest microleakage among all the groups. The number of layers (2 layers vs. 4 layers) did not result in any differences in microleakage scores of the composite resins (P = 0.42). CONCLUSION Water storage times did not result in any significant effect on microleakage of P90 and P60

Prevalence of Metabolic Syndrome in an Adult Urban Population of the West of Iran

Objectives. We determine the prevalence of the metabolic syndrome in an urban population of Zanjan, a province located to the west of Tehran. Methods. Randomly selected adults >20 years were studied using stratified sampling. Target study sample was 2941 (1396 males and 1545 females). Metabolic syndrome was diagnosed using Adult Treatment Panel-III (ATP-III) guidelines when any three of the following were present: central obesity, raised triglycerides ≥150 mg/dl, low high-density lipoprotein (HDL) cholesterol, blood pressure ≥ 130/ ≥ 85 mm Hg, and diabetes or fasting plasma glucose (FPG) ≥ 100 mg/dl. Results. Metabolic syndrome was present in 697 (23.7%) subjects (CI 95%:22%–25%, P = .001), prevalence was 23.1% in men and 24.4% in women (P : .4). The prevalence increased from 7.5% in the population younger than 30 y to 45.6% in ages more than 50 years. Low HDL was the most common metabolic abnormality in both sexes. Most of those with metabolic syndrome had three components of the syndrome (75.6%), 170 subjects (24.4%) had four and none had five components simultaneously. The prevalence of obesity (BMI ≥ 30 kg/m2), hypercholesterolemia (≥200 mg/dl) and high LDL cholesterol (≥130 mg/dl) was greater in the metabolic syndrome group than normal subjects (P = .00). Conclusions. There is a high prevalence of metabolic syndrome in this urban population of the northern west of Iran. Focus of cardiovascular prevention should be undertaken in this area

Evaluation of Radicular Dentin Thickness of Danger Zone in Mandibular First Molars

Objective: Better understanding of the furcation anatomy may serve to decrease the risk of root perforation. The purpose of this study was to measure the thickness of root walls in the danger zone in mandibular first molars.Materials and Methods: The roots of 53 extracted human mandibular first molars were sectioned in the horizontal plane 4 mm below the orifice of the mesial and distal root canals.For each cut surface buccal, lingual, mesial, and distal thickness of the root wall wasmeasured. Mean values of the thickness at each location were calculated and compared by ANOVA and t-test.Results: The results showed that the mean thickness in the distal portion of the mesial root was smaller in comparison to all other portions of the roots (P<0.05) and this difference was statistically significant except for the mesial portion of the distal root (P=0.463). The mean thickness of radicular dentin at the distal aspect of mesial roots was 1.2 millimeter.Conclusion: Our study suggests that knowledge of the root dentin thickness in the danger zone is essential for preventing endodontic mishaps leading to failure

Throughput Improvement by Mode Selection in Hybrid Duplex Wireless Networks

Hybrid duplex wireless networks, use half duplex (HD) as well as full duplex (FD) modes to utilize the advantages of both technologies. This paper tries to determine the proportion of the network nodes that should be in HD or FD modes in such networks, to maximize the overall throughput of all FD and HD nodes. Here, by assuming imperfect self-interference cancellation (SIC) and using ALOHA protocol, the local optimum densities of FD, HD and idle nodes are obtained in a given time slot, using Karush–Kuhn–Tucker (KKT) conditions as well as stochastic geometry tool. We also obtain the sub-optimal value of the signal-to-interference ratio (SIR) threshold constrained by fixed node densities, using the steepest descent method in order to maximize the network throughput. The results show that in such networks, the proposed hybrid duplex mode selection scheme improves the level of throughput. The results also indicate the effect of imperfect SIC on reducing the throughput. Moreover, it is demonstrated that by choosing an optimal SIR threshold for mode selection process, the achievable throughput in such networks can increase by around 5%

Delayed Graft Function, Allograft and Patient Survival in Kidney Transplantation

Introduction: Delayed Graft Function (DGF) is a common complication of renal transplants and the long-term relation between DGF and survival of patients and grafts is not well established.Methods: This is a historical cohort study of transplanted patients in Taleghani Hospital of Shahid Beheshti University in Iran between 1994 and 2010. Patients who required dialysis during the first week after transplantation were considered to have DGF. The patients&rsquo; conditions were updated to determine existing graft function, graft loss or patients&rsquo; death at one year and five years post transplantation in relation to the presence or absence of DGF.Results: DGF complicated 67/385 transplants (17.4%). Causes included acute tubular necrosis (58.2%), accelerated rejection (29.9%), transplant renal artery thrombosis (9%) and renal vein thrombosis (3%). More kidneys in the DGF group were procured from cadaveric donors (6% versus 0.9%, P = 0.02). At hospital discharge, patients with DGF had significantly higher mean creatinine level (4.4&plusmn;2.8 versus 2.0&plusmn;1.7; P=0.001) compared to other patients. They also had more early acute rejection episodes and more late acute rejection episodes (34.3% versus 2% and 16.4% versus 3%, respectively; P = 0.0001) compared to other patients. The proportion of functioning grafts was significantly lower in the DGF group at 1-year (53.7% versus 95.3%, P = 0.0001) and 5-years (22.4% versus 61.6%, P =&nbsp; 0.001) compared to patients without DGF.Conclusion: The DGF group had a significantly higher acute rejection rate and an increased risk of graft loss at one and five years

Evaluation of Enamel and Dentinal Microleakage in Class II Silorane-Based and Methacrylate-Based Resin Composite Restorations Using Specific and Nonspecific Adhesives

Objectives: The aim of this study was to evaluate enamel and dentinal microleakage in Class II cavities restored with silorane- and methacrylate-based resin composites using specific and nonspecific adhesives. Materials and Methods: Thirty-six caries-free human premolars were used. Two Class II cavities were prepared on each tooth. The gingival floor was set at 1 mm above (on the mesial surface) and at 1 mm below (on the distal surface) the cementoenamel junction (CEJ). The samples were randomly divided into four groups, and the cavities were restored with a methacrylate-based composite (Filtek™ P60) and a silorane-based composite (Filtek™ P90) with specific and nonspecific adhesives. Microleakage was tested using a standardized dye penetration method. All samples were examined under a stereomicroscope, and microleakage scores were statistically analyzed using Kruskal-Wallis and Mann-Whitney-U tests. One sample from each group was examined under a scanning electron microscope (SEM) to determine the bonding area. Results: No significant difference was found between the groups in terms of the enamel microleakage (P=0.086). There was a significant difference between the groups with regard to dentinal microleakage (P=0.003). No significant reduction in microleakage was observed in groups restored with Filtek™ P90 composite using its specific adhesive compared to those restored with Filtek™ P60 composite using its specific adhesive (P=0.626). Conclusions: The results indicated that the application of methacrylate- and silorane-based composites with specific or nonspecific adhesives had no impact on enamel microleakage, but it affected dentinal microleakage, and specific adhesives showed less microleakage. It seems that a phosphate-methacrylate-based intermediate resin is required to bond dimethacrylate adhesive to silorane-based composites

The Effect of Probiotics on Childhood Constipation: A Randomized Controlled Double Blind Clinical Trial

Background. Inconsistent data exist about the role of probiotics in the treatment of constipated children. The aim of this study was to investigate the effectiveness of probiotics in childhood constipation. Materials and Methods. In this placebo controlled trial, fifty-six children aged 4–12 years with constipation received randomly lactulose plus Protexin or lactulose plus placebo daily for four weeks. Stool frequency and consistency, abdominal pain, fecal incontinence, and weight gain were studied at the beginning, after the first week, and at the end of the 4th week in both groups. Results. Forty-eight patients completed the study. At the end of the fourth week, the frequency and consistency of defecation improved significantly (P=0.042 and P=0.049, resp.). At the end of the first week, fecal incontinence and abdominal pain improved significantly in intervention group (P=0.030 and P=0.017, resp.) but, at the end of the fourth week, this difference was not significant (P=0.125 and P=0.161, resp.). A significant weight gain was observed at the end of the 1st week in the treatment group. Conclusion. This study showed that probiotics had a positive role in increasing the frequency and improving the consistency at the end of 4th week

EFFECT OF SURFACE CONDTIONINGON BOND STRENGTH TO ENAMEL AND DENTIN

Introduction. Compoglass is a trade mark of dental compomers and because of its partially resinus structure, surface conditioning of dental surfaces is needed for a better bonding process. In this study, the effect of enamel and dentin conditioning procedure on shear bond strength (SBS) of compoglass to tooth surfaces was studied.&#13; Methods. four groups each one including 11 sound premolars were chosen and their surfaces were prepared as following groups: group1, unconitioned dentin; group 2, dentin conditioning with phosphoric acid 35%; group 3, dentin conditioning with polyacrylic acid 20% group 4, unconditioning enamel; group 5, enamel conditioning with phosphoric acid 35%; and group 6, enamel conditioning with polyacrylic acid 20%. Compoglass was bonded to prepared surfaces and after fixation of the samples in acrylic molds, all samples were tested under shear force of instron testing machine at a rate of 1 mm/min speed.&#13; Results. The mean SBS obtained in these 6 groups were 6.207, 8.057, 10.146, 25.939 and 11.827 mpa. the mode of fracture also studied using a streomicroscope. Statistical analysis of the results showed that the maximum SBS obtained in group 5 and the lowest SBS about 6.207 mpa obtained in group 1. Despite increase in SBS group 2 and 3, there was no statistical differncies between group 1, 2 and 3.&#13; Discussion. Based on results of this study, conditioning of enamel and dentin surface due to improve SBS is recommeneded

COMPARISON OF SHEAR BOND STRENGTH OF COMPOSITE TO DECIDUOUS TEETH ENAMEL FOLLOWING PHOSPBORIC ACID AND ND:YAG LASER ETCHING

Introduction. Enamel acid etching prior to repair dental caries and fractures with composites has been quite satisfactory and economic, however, etching on deciduous dentition has shown less effective due to its resistance to acids. The purpose of this study was to evaluate composite bond strength on decidious teeth treated with laser instead of being acid etched.&#13; Methods. Forty four deciduous molars without any restoration or buccal decay were chased and randomly divided in the four groups of 10. Four other teeth were prepared for SEM observation. Group 1: samples were treated with Nd: YA Glaser (20 pps, 1.6 w). Group 2: samples, treated with Nd: YA Glaser (10 pps, 0.8 w). Group 3: samples acid etched with 37% phosphoric acid. Group 4: samples in this group were taken as control with no treatment on enamel. Shear bond strength of the composite and teeth in all 4 groups were then measured with universal tast machine (Dartec).Data were analysed statistically using ANOVA test.&#13; Results. The least mean amount of bond strength was related to group 4 (control), which was significantly different from other groups (P &lt; 0.05). The most mean amount was related to group 3 (acid etched) with statistically significant difference from other groups (P &lt; 0.05). Among the samples treated with laser, group 1 has greater amount of mean strength comparing to group 2, however this difference was not significant (P &gt; 0.05).&#13; Discussion. In order to obtain optimum bond strength for composite restorations, enamel surface should be prepared. Use of Nd: YAG laser for enamel etching under the condition of our study is not recommended on deciduous dentition

STATIC ANALYSIS OF STRESSES INDIUCED BY MATRIX BAND IN ROOT CANAL TREATED SECOND PREMOLARS MOD CAVITIES BY FINITE ELEMENTH TECHNIQUE

Introduction. The purpose of this study is measurement the stresses due to matrix bond and their effect on fracture or crock formation in teeth and finally modifying in treatment methods of tooth.&#13; Methods. We use a second premolar that was as similar as measurements of wheelers studies. Au mod cavity prepared with buccolingual width 3mm while the roof of pulp chamber has been removed and gingival floor was 1mm higher than CEJ. CTS was prepared in three dimention: crolan, sigital and axial and then tooth model was made based on Nisall program. The forces due to matrix band measured by strain guage and then, this force based on finite element method applied on the prepared model.&#13; Results: Inall cases, stresses observed in tensile and shear from tensile stresses was mainly in cervical one third of buccal cups and shear stress was surronded cervical area of the tooth like as circle. The greatest amount of forces were localized in gingival floor in mesial area and in the enamel with increasing the depth and sidth of cavity. The amount of this stresses increased especially in increasing of depth. With increasing the width and depth cuspal displacment was observed especially in colossal on third which localized in buccal cusp.&#13; Discussion. Matrix band stresses mainly are destructive and cause fractures or at least crack formation in tooth. So its preffered to use thinner band in shorter time as much as possible. using of anatomic bands were prefeved