Journal of Dental Biomaterials
Volume:2 Issue: 2, 2015

Statement of Problem: Microleakage is one of the most important problems in composite restorations. One way to reduce the microleakage is decreasing the total amount of resin by insertion of fibers in composite restorations. This study aimed to compare the microleakage of Silorane and methacrylate-based composites (a nanohybrid) in Class II restorations with gingival margins on the root surface, with or without placing glass and polyethylene fiber. 60 extracted sound third mandibular molars were disinfected. Class II slot cavities were provided on both proximal sides of each tooth. Based on application of composites and fibers, the teeth were randomly divided into 6 groups (n=20). group1: Z350; group2: Z350 + polyethylene fiber; group3: Z350 + glass fiber; group4: P90; group5: P90 + polyethylene fiber; and group6: P90 + glass fiber. The specimens were thermocycled, immersed in 2% basic fuchsine dye solution, and then sectioned to assess dye penetration under stereomicroscope (40X). Results were statically analyzed by Kruskal-Wallis and Mann-Witney tests at a significance level of p<0.05. There was a significant decrease in microleakage in Silorane composite when compared to nanohybrid composite (p<0.001). There was not any significant difference among groups with or without fiber inserts. The use of Silorane composite reduces the microleakage in comparison with nanohybrid composite and fiber insertion had no effect on the microleakage in class II silorane and nanohybrid composite restorations with gingival margins below the CEJ.

Statement of Problem: There are controversial reports regarding physical and mechanical properties of resin composites and glass ionomer cements. Some revealed higher strength and hardness for resin composites while others showed a comparable value for glass ionomer cements. Evaluation of mechanical properties of different types of resin composites in comparison with resin modified glass ionomers is not widely studied. To measure and compare the flexural strength and Vickers hardness of three resin composites and two resins modified glass ionomer cements before and after ageing. Three resin composites, i.e. Filtek Supreme XTE (3M ESPE), Ice (SDI), Gradia (GC), and two resins modified glass ionomers, i.e. Fuji II LC (GC) and Riva Light Cure (SDI), were selected. Ten bar-shaped specimens were prepared for each material and cured using LED curing light. After 24 hours storage in distilled water at 37oC, the specimens were randomly divided into two equal groups (n=5). The first group was tested as a baseline and the second group was restored at 37oC for another 29 days. Flexural strength was performed by four-point bending test using universal testing machine at crosshead speed of 0.5mm/min, and the maximum load at failure was recorded. The specimen’s halves were used for evaluating Vickers hardness, using a Digital Hardness Tester (300 g/15 sec) and the Vickers hardness number (VHN) was recorded. Data were analyzed using one-way analysis of variance (ANOVA), Tukey’s and student’s t-test. After 24 hours of immersion, the highest hardness number was found for Filtek Supreme and Ice and the highest flexural strength was obtained for Gradia. After 30 days of storage, hardness of Fuji II LC and Gradia showed a significant decrease; flexural strength of Ice and Fuji II LC revealed a significant increase while Gradia and Filtek Supreme showed a significant decrease. Resin modified glass ionomers showed a comparable result for hardness and flexural strength with some of the tested resin composites and lower values than some others.

Statement of Problem: The long-term success of a dental implant relies on implant osseointegration into native and viable bone, implant placement in an ideal position, and optimal hard and soft tissue contour. This requires the presence of sufficient alveolar bone volume, good alveolar ridge (Practically with no sign of atrophy) and good surgical technique. The aim of this randomized controlled clinical study was to evaluate morphometric changes after different alveolar ridge preservation procedures. In this study, 33 patients who had single-rooted premolar, which needed to be extracted, were recruited. Patients were randomly divided into 3 groups and after tooth extraction the following treatments were administered: in group A: NanoBone and a collagen membrane; in group B: NanoBone and Stypro; and in group C: natural healing. The following clinical parameters were evaluated at baseline and 6 months after the extraction: buccolingual width, midbuccal height (with the use of a custom made stent) and width of keratinized gingiva. For data analysis, Paired t-test,one-way ANOVA and Tukey’s tests were used. The average reduction in the buccolingual width, midbuccal height and keratinized gingiva was as follows: group A: 1.18±0.6, 0.64±0.92 and 3.45±1.75 mm; group B: 2.18±0.75, 0.73±0.78 and 4.73±0.9 mm; and group C: 1±0.89, 2.36±1.21 and 5±0.63 mm, respectively. Moreover, a significantly reduced resorption was found in both the buccolingual width and the width of keratinized gingiva in group A as compared to groups B and C (p<0.05). This study showed that the use of collagen membrane+Nano bone (group A) can significantly reduce the horizontal resorption of the alveolar ridge and keratinized tissue more effectively than stypro+Nano bone (group B) and blood clot alone and natural healing (group C).

Statement of Problem: T-loop is one of the most popular closing loops in orthodontic profession. However its activation is in the contrary to Bouschinger effect theory, since the formed bends would be opened during activation. The purpose of this study was to add a helix in a way to be more respondent to the Bouschinger effect theory. To compare the load deflection, maximal elastic load and range between three different types of T-loop. 5 sample of each 3 different designs of T-loop (group 1: original T-loop, group 2: T-loop with the two inner helices, group 3: T-loop with the two helices constructed outside the horizontal part) had been tested with universal testing machine (Instron). The load –deflection curves was plotted and the mechanical properties (load deflection, maximal elastic load and range) were measured. One way ANOVA was used to identify statistical differences between designs. The mean value of maximal elastic load in group 1 (6.02±0.27) was significantly higher than group 2 (5.16±0.46) and in group 2 were significantly higher than group3 (4.35±0.25) (p<0.001). A significantly higher load deflection was reported in group 1 (0.73±0.36) in comparison to group2 (0.56±0.74) and group 3(0.56±0.69) (p=0.002), with no significant difference between two latest groups (p=0.999). The mean range in group 3 (4.15±0.10) was significantly lower than group 1(5.43±0.13) and group 2 (5.59±0.15) (p=<0.001) with no significant difference between group 1 and 2 (p=0.149). The results revealed that increasing length of T-loop with helices will decrease Load deflection rate the place and design of helices might not be a crucial factor. The new design of T-loop with helices relevant to Bouschinger effect theory needs a further survey regarding their position.

Statement of Problem: Despite the increasing demand for tooth-colored restorations in dentistry, polymerization shrinkage and marginal microleakage still remains a problem. The purpose of the present study was to evaluate microleakage in three different resin composites, P90, Z250 and Z250 XT, in class V cavity of permanent human premolars. Standardized class V cavities were prepared on the buccal surface of 45 extracted human premolars. The occlusal margins of cavities were prepared at the enamel and gingival margins extending 1mm below the cementoenamel junction. The teeth were randomly assigned into three groups (N=15) and preparations restored with three different composites following the manufacturer instructions: Group A, Filtek Z250 (microhybrid composite) with Adper Single Bond total etch adhesive system; Group B, Filtek Z250 XT (nanohybrid) with Adper Single Bond total etch adhesive system;Group C, Filtek P90 (silorane) with its self-etch adhesive system (P90 system adhesive). its adhesive system (P90 system adhesive). The teeth were then subjected to thermal cycles (1000 cycle, 5° and 55°C ± 2°C) with a dwell time of 30 seconds, and immersed in 2% basic fuchsine for 24 hours. Longitudinally sectioned teeth were examined under the stereomicroscope. Kruskal-Wallis and Mann-Whitney U test at 95% significance level were used. Filtek Z250XT showed significantly higher microleakage than the other two composites (p<0.001). However, there was no statistically significant difference between P90 and Filtek Z250 (p=0.217). Although all of the restorative systems had microleakage, silorane-based composite showed less microleakage compared to two other methacrylate-based composites.