Journal of Dental Medicine
Year:2013 | Volume:26 | Issue:1 (74)|Papers Count:13

Background and Aims: The marginal integrity of fixed restorations always is a major matter of concern for dental clinicians. Any cause of distortion, including veneering processes, in the marginal integrity is supposed to be detrimental for long-term success of fix dental prostheses. The aim of this in vitro study was to compare the marginal adaptation of single full ceramic restoration and possible changes in marginal integrity following the multiple veneering process.Materials and Methods: Twelve all-ceramic crowns in the form of coping were fabricated on a pre-made standard metal die with finish line of shoulder preparation from two commercial systems: Cercon® and Zirkonzahn®. The specimens were not cemented. The Crown/Die discrepancy were measured by means of a precise stereo microscope (accuracy±0.1 mm), at various points (n=12) selected along circumferential margin of the restorations. Same procedure was accomplished after applying the veneering porcelain. The mean gap dimensions were calculated and data were analyzed by multivariate (b) test.Results: Mean marginal gap dimensions before and after veneering porcelain firing cycles, respectively for Cercon® were (59.67±13.46 mm) and (63.75±14.16 mm) and for Zirkonzahn® were (65.81±24.37 mm) and (64.74±21.94 mm). Hotelling trace Multivariate (b) test method showed that the rate of mismatching marginal integrity in two groups (Cercon® and Zirkonzahn®) had no significant difference before and after porcelain firing (P>0.05).Conclusion: Within the limitation of this study, the marginal integrity of both systems were seems to be within the clinically acceptable standard dimension, i.e.120 mm.The marginal gap of both all-ceramic systems were not affected by veneering porcelain firing cycles.

Background and Aims: Marginal seal in class V cavity and determining the best restorative material to decrease microleakage is of great in operative dentistry. The aim of this study was to evaluate the effect of load cycling on microleakage of low shrinkage composites compared with methacrylate base composites with low shirinkage rate in class V cavity preparation. Marginal integrity of these materials was assessed using scanning electron microscope (SEM).Materials and Methods: In this in vitro study, class V cavity preparations were made on the buccal and lingual surfaces of 48 human premolars and molars (96 cavities). The specimens were divided into four groups each containing 12 teeth (24 cavities): group 1 (Kalore-GC+G-Bond), group 2 (Futurabond NR+Grandio), group 3 (All Bond SE+Aelite LS Posterior), group 4 (LS System Adhesive Primer & Bond+Filtek P90). All the specimens were thermocycled for 2000 cycles (5-50oC). In each group, half of the specimens (n=12) were subjected to 200,000 cycles of loading at 80 N.Epoxy resin replicas of 32 specimens (4 restorations in each subgroup) were evaluated using SEM and the interfacial gaps were measured. Finally, the teeth were immersed in 0.5% basic fuchsin dye for 24 hours at 370 c, then sectioned and observed under stereomicroscope. The data were analyzed using Kruskal-Wallis and Mann-Whitney U tests and the comparison between occlusal and gingival microleakage was made with Wilcoxon test.Results: Within unloaded or loaded specimens, there were no significant differences in microleakage among four groups on the occlusal margin (P>0.05). But there were statistically significant differences in microleakage between silorane and Aelite on the gingival margin (P<0.05). No statistically significant differences were found between microleakage of the loaded and unloaded groups on both the occlusal and gingival margins for all materials (P>0.05).Conclusion: Silorane did not perform better than the conventional low shrinkage methacrylate-based composite in terms of sealing ability (except Aelite). Cyclic loading did not increase the extent of leakage in any groups.

Background and Aims: The purpose of this in vitro study was to assess the effect of two different surface treatments on the contrast ratio of IPS Emax press ceramic submitted to accelerated aging.Materials and Methods: Ten ceramic (IPS Emax press) disks (10-mm diameter and 1.5-mm thick) were fabricated according to the manufacturer’s recommendations. The samples were randomly divided into 2 groups (n=5): polishing and glazing. Contrast ratio ware obtained with a spectrophotometer before and after accelerated aging. The contrast ratio (CR=Yb/Yw), defined as the ratio of illuminance (Y) of the test material when it is placed on the black background (Yb) to the illuminance of the same material when it is placed over a white background (Yw), was determined. The data were statistically analyzed by two-way analysis of variance (P<0.05).Results: All specimens of IPS Emax press ceramic showed significant increase in CR after 300-hour accelerated aging time (P=0.005). Polished samples showed significantly higher opacity compared with that of the glazed ones (P=0.018).Conclusion: Within the limitations of this study, it may be concluded that the glazed specimens showed more stability in their translucency than the polished specimens.

Background and Aims: Polymerization shrinkage in Methacrylate-based composite is one of the most important factors in composite restorations failure. Silorane-based composite is introduced to compensate this drawback and claimed to have low shrinkage. The aim of this study was to evaluate the polymerization shrinkage of these two composites.Materials and Methods: In this experimental study, 5 disk shape samples for each resin composites were placed in the centre of metallic ring bonded to microscopic glass slab. Top surface of ring was covered by glass cover slip. Glass slab and sample were placed on a special LVDT holder in order to light cure from bottom surface and to measure the polymerization shrinkage. In this study, Deflecting Disk method and LVDT (linear variable differential transducer) was used for dimensional change measurement of resin composites. In this study two LED curing units were used for composite polymerization.Results: Mean of polymerization shrinkage in Z250 cured with LED and High Power LED was 11.15±0.08 mm and 11.51±0.17 mm, respectively (P=0.094), and in P90 cured with LED and High Power LED was 1.08±0.06μm and 1.16±0.12 mm, respectively (P=0.019).Conclusion: Silorane base composite (P90) showed significantly less polymerization shrinkage than methacrylate base composite (Z250). For the two types of composite, there was no significant difference between the two curing unites in polymerization shrinkage.

Background and Aims: To evaluate the effect of polishing on surface roughness of silorane-based composite using profilometery and SEM and compare it with that of a methylmethacrylate-based composite and a glass ionomer.Materials and Methods: In this study, 3 groups (n=28) were tested: specimens of two composites (Filtek P90 and Filtek P60) and a glass ionomer (Fuji IX) which were prepared in polyethylene molds (4 mm diameter × 10 mm height). Half of the specimens in each group were finished with 180-grit silicon carbide paper and the remaining samples were finished with 180-grit, and subsequently polished with 250, 400, 800, 1000, 2000, and 2500-grit silicon carbide papers. The surface roughness was evaluated using a contact profilometer and then mean (Ra) and maximum (Rmax) of surface roughness and were recorded. Then, the surface of 4 specimens of each subgroup was observed under the field emission scanning electron microscopy. Statistical analysis was performed with T-test, ANOVA and Dunnett T3 tests.Results: In all materials, Ra was different between polishing with 180 and 2500-grit silicon carbide papers. In 180-grit group, only Ra of Filtek P60 and Fuji IX showed significant difference (P=0.01). In 2500-grit group, there was no significant difference between the Ra of Filtek P60 and Filtek P90 (P=0.56).Conclusion: Polishing is recommended for Fuji IX and posterior composite restorations.

Background and Aims: Discoloration of resin composites is considered to be the major factor in esthetic restoration failures. The aim of this study was to evaluate the color stability of resin composites after rebonding with two different adhesive materials.Materials and Methods: Forty five composite disc samples were divided into three groups (n=15). The surface of samples was finished by polishing disc and rubber. In group 1, any additional phase was not performed. In group 2, composite discs were etched by %37 orthophosphoric acid, then Margin- bond was used for rebonding.In group 3, the etching procedure was in the same manner used for group 2, but Permaseal was used in disc level after etching. After the first phase of spectrophotometric measurement, the samples were dipped in coffee mix for 3 weeks in order to make the samples aged. Then the second phase of spectrophotometric evaluation was performed. Collected data was analyzed using one-way ANOVA test in addition to a Tukey test. P<0.05 was considered as the level of significance.Results: The mean total color difference (ΔE) observed in groups 1 to 3 was 1.4±0.34, 5.24±1.51, and 7.44±1.34, respectively. Statistical significant difference was shown between the groups (P<0.001).Conclusion: Rebonding with adhesive materials used in this study did not increase the color stability of composite restorations.

Background and Aims: In response to esthetic demand of patients, ceramic abutments have been developed. In spite esthetic of zirconia abutments, machining accuracy of these abutments has always been a question. Any misfit in the abutment-implant interface connection can lead to detorque and screw loosening. The aim of this study was to compare torque loss value of manually aided design/manually aided manufacture (MAD/MAM) zirconia abutments with prefabricated titanium abutments.Materials and Methods: Seven titanium abutments (Branemark RP, Easy abutment) and seven copy milled abutments which were duplicated from the prefabricated one in Zirkonzhan (ZirkonZahn, Sand in Taufers, Italy) were prepared. After sintering process of zirconia abutment, all abutments were fastened with a torque screw under 35 Ncm. Detorque measurements were performed per group pushing the reverse button of the Torque controller soon after screw tightening with values registered. The mean torque loss were calculated and compared by a Student’s t test.Results: The mean of torque loss was 12.71 Ncm with standard deviation of 1.70 for prefabricated titanium abutments and 15.50 Ncm with standard deviation of 4.67 for MAD-MAM abutments. The difference between the two groups was not statistically significant (P=0.23).Conclusion: Within the limitation of this study MAD-MAM ceramic abutments could maintain the applied torque comparing to the prefabricated abutments.

Background and Aims: The exfoliated human deciduous tooth contains multipotent stem cells [Stem Cell from Human Exfoliated Deciduous tooth (SHED)] that identified to be a population of highly proliferative and clonogenic. These cells are capable of differentiating into a variety of cell types including osteoblast/osteocyte, adiopcyte, chondrocyte and neural cell. The aim of this study was to evaluate the differentiation of SHED to osteoblast in standard osteogenic medium and comparing the results with medium which supplemented with glucosamine in form of chitosan.Materials and Methods: Dental pulp cells were isolated from freshly extracted primary teeth, digested with 4 mg/ml collogenase/dispase, and grown in Dulbecco's modified Eagle's medium with 10 percent fetal bovine serum. The clonogenic potential of cells was performed after 3 weeks of culture. Flowcytometric analysis, performed at day 21 of culture to identify surface markers of mesenchymal stem cells. The cells from 3rd passage used for osteogenic differentiation in routine osteoinductive medium. Chitosan (10 mg/ml) was added to the culture medium of case group. Alizarin Red Staining and Alkaline Phosphatase (ALP) activity were done to evaluate osteogenic differentiation in the developing adherent layer on the third passage. The results were analyzed using T-test. For the analysis of normal distribution of data, non-parametric Kolmogrov-Smirnov test was used.Results: The colonogenic efficiency was more than 80%. Flowcytometric analysis showed that expression of mesenchymal stem cell marker CD90, CD105 and CD146 were positive in SHED, while hematopoietic cell marker CD34, CD45 and endothelial cell marker CD31 were negative. Quantitative analysis of Alizarin Red Staining demonstrated that: mineralized nodule formation was higher in the group supplemented with glucosamine (chitosan). Results from Alkaline Phosphatase activity test, on day 21, demonstrated a significantly higher ALP activity in the group supplemented chitosan (P<0.001).Conclusion: Stem cells isolated and cultured from exfoliated deciduous teeth pulp, can be differentiated to osteoblast. Addition of chitosan can be beneficial to promote osteogenic differentiation of these cells.

Background and Aims: The Panoramic radiography is one of the routine techniques in implant imaging. Although there are some limitations with this technique, panoramic radiography is radiographic choice for basic evaluation for implant treatment. Many studies have been designed to determine magnification in panoramic images but most of them were performed on dry skulls or radiographic phantoms. In recent studies CT or CBCT are used as gold standard. The aim of this study was to determine vertical magnification of panoramic images by using renovated CT sections in anterior and posterior regions of both jaws.Materials and Methods: 30 panoramic radiographs (Planmeca EC or CC Proline) were selected from patients of implant department and Particular anatomic landmarks were selected in those images. Vertical dimensions of these landmarks were measured in both panoramic and renovated cross sectional CT images by a digital caliper and vertical magnification was calculated as the ratio of image dimensions to the real dimensions.Results: The mean vertical magnification of panoramic radiographs in anterior and posterior maxillae were 1.22±0.02 and 1.16±0.02, respectively. The mean vertical magnification of panoramic radiograph in anterior and posterior were 1.20±0.02 and 1.13±0.02, respectively. The differences between magnification in mandible and maxillae were significant (P<0.001). The differences between magnification in anterior and posterior regions of both jaws were also significant (P=0.11).Conclusion: Vertical magnification of panoramic images (Planmeca EC or CC Proline) in different regions in both jaws were between 1.13 to 1.22.

Background and Aims: Candida Albicance is one of the most common oral opportunistic infection. Antifungal drugs have several side effects as well as bad taste. Licorice is one of the oldest drugs in Iranian traditional medicine. It has antibacterial and antiviral effects; however, there are a few studies about its antifungal. Therefore, this study was designed for in vitro evaluation of the antifungal effect of licorice.Materials and Methods: Candida Albiance (TIMM 2640) was cultured. After licorice extract was prepared, its antifungal effect was compared with that of nystatin using agar diffusion method.Results: Diameter of inhabitation zone was 32.60±0.84 mm in nystatin group and almost zero in licorice groups. There was statistically significant difference between nystatine and licorice extract (P=0.002).Conclusion: Based on the result of this in vitro study, licorice extract did not show any antifungal effect.