ABSTRACT
Statement of Problem: The degree of conversion depends on the material composition, light source properties, distance from light source, light intensity, curing time, and other factors such as shade and translucency
Objectives: In the present study, we evaluated the effects of different light- curing modes and shades of methacrylate and silorane-based resin composites on the degree of conversion of resin composites [DC]
Materials and Methods: The methacrylate-based [Filtek Z250, 3M, ESPE] and low-shrinkage silorane-based [Filtek P90, 3M, ESPE] resin composites were used in three groups as follows: group 1-Filtek Z250 [shade A3], group 2-Filtek Z250 [shade B2], and group 3-Filtek P90 [shade A3]. We used a light-emitting diode [LED] curing unit for photopolymerization. 10 samples were prepared in each group to evaluate the degree of conversion; 5 samples were cured using soft-start curing mode, and the other 5 were cured using standard curing mode. The DC of the resin composites was measured using Fourier Transform Infrared Spectroscopy [FTIR]. The data were analyzed using Kruskal Wallis and one- way ANOVA statistical tests
Results: The degree of conversion of silorane-based resin composite was 70 - 75.8% and that of methacrylate-based resin composites was 60.2 - 68.2% [p = 0.009]. The degree of conversion of the composite with brighter colour [B2] was statistically more than the darker composite [A3]. Higher degree of conversion was achieved applying the standard curing mode
Conclusions: The results of the study showed that the colour and type of the resin composite and also the curing mode influence the degree of conversion of resin composites
ABSTRACT
Statement of Problem: Because dental restorations are time consuming, dental material manufacturers make an attempt to discover new methods for rapidity and increasing the quality of restorations. With this objective in mind, plasma arc curing devices have been manufactured
Purpose: This study was done to compare the effect of plasma arc and halogen light curing on the microleakage of class V resin composite
Methods and Material: In this experimental study, on 80 extracted maxillary central teeth, standard class V cavities were prepared with incisal and gingival margins in the enamel and dentin. After etching and bonding, the teeth were randomly divided into two subgroups of 40 and restored with Amelogen composite. In the first group, halogen light curing for 40 seconds was used and in the second one plasma arc curing was used for four seconds. After thermocycling and sealing, the samples were immersed into the 0.5% fuchsine solution for 24 hours and then washed with water and cut. The microleakage was scored by stereomicroscope with 40X magnification. The data were analyzed using Mann-Whitney and Wilcoxon tests
Results: The mean of incisal wall microleakage in the plasma arc group was 1.42+/-0.98 and in the halogen group it was 0.67+/-0.02. The gingival margin in the plasma are group showed a mean of 1.75+/-1.48 and in the halogen group it was found to be 1.67+/-1.54. There were significant differences in the incisal wall [p =0.0001], but not in the gingival wall [p =0.744]. The average rate of microleakage in the gingival and incisal walls in the plasma arc group was 3.17+/-1.79 and in the halogen group it was 2.76+/-1.92; there were not any significant differences between the groups [p =0.32]
Conclusion: In the restorations with enamel margins halogen light curing and in all composite restorations plasma arc curing are preferred due to the short time of curing
ABSTRACT
Bonded restorations have a number of advantages over traditional, non-adhesive methods. Adhesion reduces the microleakage at the restoration-tooth interface. Prevention of microleakage, or the ingress of oral fluids and bacteria along the cavity wall, reduces the clinical problems such as postoperative sensitivity, marginal staining, and recurrent caries, all of which may jeopardize the clinical longevity of restorative efforts. The aim of this study was to evaluate the microleakage in class V composite restoration with total-etch and self-etch adhesive systems. In this in-vitro study, 48 standard class V cavities were prepared in the buccal surface of human extracted premolars so that the occlusal margins of the cavities were in the enamel and the gingival margins in the dentin [cementum]. The teeth were divided into two groups of 24. In the first group, the cavities were restored with total-etch system [Excite] and composite. The teeth in the second group were restored with self-etch system [Prompt L-Pop] and the same composite. The teeth were thermocycled 500 times between 5 - 55°C and then were covered with nail-polish and adhesive wax axcept for 1 mm around cavities, and all teeth were immersed into the 2% methylene blue for 10 hours. The samples were mounted in polyester blocks, sectioned longitudinally at the middle of the cavities, and evaluated for microleakage under a stereomicroscope at 40x magnification. Dye penetration was scored between 0-3. Data were analyzed with Mann Whitney and Wilcoxon tests. In the enamel and dentin margins, microleakage for the total-etch group was found to be less than the self-etch group [p < 0.05]. A significant difference in the microleakage mean rank of the enamel and dentin margins was observed [p< 0.05]. Microleakage in the enamel margins was less than that in the dentin margins. Total-etch adhesive system showed a significant difference on the microleakage of class V composite restorations especially in the enamel margin
Subject(s)
Dental Leakage , Dental BondingABSTRACT
Statement of Problem: Bitewing radiography is a suitable clinical technique for the diagnosis of interproximal caries. Many researches performed in this field have shown that direct digital radiography and conventional radiography films in dentistry are similar in detecting inter-proximal caries
Purpose: To compare the effects of image processing mode of colorize on the efficacy of the detection of interproximal carious lesions viewed in direct digital radiography
Methods and Material: A total of 102 proximal surfaces of the extracted human premolar teeth on direct digital images with and without application of pseudocolor filter were evaluated by three observers. The teeth were sectioned and viewed microscopically to determine the gold standard. The kappa value agreement ratio was calculated
Results: Sensitivity and specificity values in normal digital images were found to be 66.7% and 60% and for colorized images 80.5% and 50%, respectively. However, there was no statistically significant difference between the two types of images [p = 0.12]
Conclusion: In this study, application of pseudocolor software failed to result in statistically significant differences between normal and colorized digital images
ABSTRACT
Self etch acidic primers may be unable to etch the enamel and penetrate the thick dentinal smear layer and as a result produce inadequate bond strength. The present study aimed to evaluate the effect of the second layer application of two self-etch primers on etching pattern and micro-shear bond strength to the enamel and dentin. In an experimental study, 104 human premolar teeth were divided into two groups. The buccal surfaces of the teeth were prepared for enamel and dentinal evaluation. Self-etch primer of clearfil SE Bond and clearfil S3 Bond were applied in one or two layers on the prepared enamel and dentin surfaces. One specimen of each prepared group was selected for SEM group evaluation. The composite resin cylinders were bonded to the rest of the specimens for micro-shear bond strength measurement. The data were analyzed using two- way ANOVA and HSD -Turkey's tests. Application of the second layer had no significant effect on micro-shear bond strength to the enamel and dentin [p>0.05]. The dentinal micro- shear bond strength values of the specimens treated by Clearfil SE Bond, were significantly higher compared to Clearfil S3 Bond [p<0.05] but no significant effect was found on enamel bond strength [p>0.05]. Application of one layer of self- etch primer produced sufficient bond strength and there is no need to apply the second layer
Subject(s)
Humans , Shear Strength , Dental EnamelABSTRACT
The success rate of light composite restorative treatments is in close relation to the light intensity of the light curing units. The purpose of this study was to evaluate the rate of light intensity of visible light curing units, before and after voltage stabilizer application. This study was performed on 82 light curing units in all clinics and dental offices of Yazd city. For evaluating light exit intensity, Hilux radiometer was used. At first, the light intensity was measured, and then by use of 220 V electrical voltage stabilizer the light exit intensity was recorded. Results were analyzed using Pearson and Spearman tests. Mean range of light intensity before and after voltage stabilizer was 241.3 and 272.6 mW/cm2 respectively. There were statistically significant differences between before and after use of voltage stabilizer [p < 0.05]. Considering the light intensity, 64.7% of the light curing units were suitable for optimum curing and 8.6% were in group that required increase light exposure time. 21.9% did not completely cure the composites, and 4.8% were in group with higher light intensity 2 [over 500 mW/Cm2]. Light intensity output of the curing units in dental clinics of Yazd city were less than expected, but by using voltage stabilizer, the light intensity was significantly increased
Subject(s)
Phototherapy/instrumentation , Phototherapy/standardsABSTRACT
Ceramic inlays are alternative systems for restoring dental cavities with tooth colored materials. These restorations may have some benefits over direct composite restorations such as reduction in the bulk of the cured composite. The aim of this study was to evaluate the microleakage of direct composite restorations and ceramic inlays with two different resin cements. In this experimental study, 45 class V cavities [15 teeth in each group] were prepared in buccal surfaces of human extracted molars. For 30 cavities, ceramic inlays were prepared and were cemented either with Variolin k / Excite DSC or Panavia F / ED primer. Fifteen samples were restored with Excite / Heliomolar [direct composite]. Then the teeth were thermocycled and were covered with sticky wax and were immersed into the 2% Methylene blue for 48 hours. The teeth were sectioned longitudinally and dye penetration was determined. Data were statistically analyzed using nonparametric tests of Kruskal Wallis, and Mann Whitney with significance level 0.05. Enamel margins showed less microleakage than dentin margins in all groups [P<0.05]. No significant differences were observed between the materials used in this study [P>0.05]. The materials used in this study can not completely prevent microlekage. It seems that ceramic inlays can not reduce microleakage over direct composite significantly
Subject(s)
Humans , Inlays , Composite Resins , Dental Leakage , Dental Restoration, Permanent , MolarABSTRACT
Resin cements are usually used for bonding ceramic inlays. The aim of this study was to evaluate the micro-leakage in class V ceramic inlays cemented with two different resin cements. A total of 30 class V cavities were prepared in buccal surfaces of human extracted molars with occlusal margins in enamel and gingival margins in dentin [cementum]. Ceramic inlays were prepared for all cavities and were cemented either with Variolink / Excite DSC or Panavia F/ED primer. These teeth were thermocycled and covered with sticky wax except for 1 mm around cavities and were immersed into 2% Methylen blue for 48 hours. The teeth were sectioned longitudinally and dye penetration was evaluated using stereomicroscope. Data was analyzed using nonparametric tests. There were no significant difference between the two types of cements in dentin or enamel margins [P>0.05]. Compared with enamel margins, Panavia F showed less micro-leakage in dentin margins [P>0.05]. The resin cements under evaluation in this study can not completely prevent micro-leakage. It seems that both cements have almost the same effects regarding micro-leakage reduction
Subject(s)
Humans , Resin Cements , Dental Restoration, PermanentABSTRACT
Objective structured clinical examination [OSCE] is one of the preferable means of evaluating cognitive, emotional and psychomotor aspects of nursing students. The present study was designed to determine the reliability and validity of OSCE in evaluating clinical skills of nursing students. For this descriptive study, 10 different skills of nursing students were selected. Then, 37 students performed these skills at 10 different OSCE stations, during which two experienced inspectors evaluated their performance. Finally, the correlation between OSCE scores and the mean theoretical and clinical performance scores of students was calculated. Meanwhile, the correlation between the total OSCE scores with OSCE score of each station was determined. Inspectors' reliability [correlation between scores reported by inspectors at each station] was also calculated. The correlation coefficient of OSCE scores and mean theoretical and clinical performance scores were 0.38 [p=0.031] and 0.52 [p=0.005], respectively. Correlation coefficient of inspectors' reliability was in a range of 0.38-0.95. OSCE is strongly suggested as a reliable and valid means of evaluating nursing students' clinical skills
Subject(s)
Humans , Clinical Competence , Educational Measurement , Reproducibility of ResultsABSTRACT
Despite the wide range of new dental materials, there is still a need for biomaterials demonstrating high biocompatibility, antimicrobial effects and ideal mechanical properties. The aim of this study was to histologically evaluate the pulpal response to a conventional glass ionomer, a resin modified glass ionomer and a calcium hydroxide in human teeth. Fifty five deep class V cavities were prepared in premolars of 31 patients and were divided into 3 groups based on application of the following liners: resin modified glass ionomer [Vivaglass Liner], conventional glass ionomer [Chembond Superior] and calcium hydroxide [Dycal]. After applying varnish, teeth were filled with amalgam. Each group was further divided into three subgroups according to time intervals of 7, 30 and 60 days. Teeth were then extracted and their crowns were fixed in formalin. Each sample was assessed microscopically for odontoblastic changes, inflammatory cell infiltration, reactionary dentin formation, remaining dentinal thickness and presence of microorganisms. Statistical analysis including Kruskal Wallis and Mann Whitney was carried out for comparison of mean ranks. [P=0.05]. In the Vivaglass Liner group, pulpal response was significantly higher on day 7 as compared to days 30 and 60 [P<0.05]. Reactionary dentin production was significantly lower after 7 days than after 60 days for all materials [P<0.05]. There was no statistically significant difference in pulpal responses among the three groups during the same time intervals [P>0.05]. There was no correlation between pulpal responses with micro-organisms and remaining dentin thickness [P>0.05]. According to the results of this study, light-cured glass ionomer as well as the other tested lining materials were determined to be biologically compatible with vital pulps in deep cavities of sound human teeth
ABSTRACT
Statement of Problem: The restoration of the teeth should have enough ability to withstand masticator forces while preserving as much tooth structure as possible
Purpose: The purpose of this study was to compare the effects of light-heat cured composite with light cured composite restorations on fracture resistance of the restored teeth
Materials and Methods: Forty healthy maxillary premolar teeth were chosen, endodontic treatment performed in 30 of them. MOD cavities were prepared in all of them to weaken tooth structures. Then, they were divided into 3 groups each of which contains 10 specimens. The groups were as follows: Group 1: unprepared teeth [sound teeth acted as control] Group 2: restored teeth with direct light cured composite resin. Group 3: restored teeth with light-heat cured composite resin as inlay without any cementing surface treatment Group 4: restored teeth with light-heat cured composite resin inlays with cementing surface treatment. Finally all samples were subjected to compressive load by testing machine. The data were analyzed using ANOVA and Duncan tests
Results: There was a significant difference in fracture resistance between 4 groups [P0.001] except groups 2 and 3. The mean fracture load for groups 1, 2, 3 and 4 were 98.96+/-16.05, 58.72+/-15.33, 54.04+/-15.56 and 78.36+/-9.83 kgf respectively
Conclusion: Using light-heat curing method and cementing surface treating of composite resin will increase fracture resistance of endodontically treated maxillary premolars