JOURNAL OF ISLAMIC DENTAL ASSOCIATION OF IRAN (MAJALLAH-I-DANDANPIZISHKI)
Year:2012 | Volume:24 | Issue:1 (82)|Papers Count:12

Background and Aim: There are some studies that strongly recommend acid-conditioning before applying the self-etch adhesives. The aim of this in vitro study was to compare the shear bond strength (SBS) of two self-etch adhesives to the enamel of primary and permanent teeth with acid preconditioning.Materials and Methods: The buccal surfaces of 48 permanent molars and 48 primary molar teeth were prepared for bonding of the adhesives to the enamel. Then the samples were randomly divided into eight groups, each containing 12. According to the manufacturers’ instructions, Clearfil SE Bond (CSEB) and ACE All Bond SE (ABSE) self-etch adhesives were applied on the enamel and the etched enamel of both permanent and primary teeth and bonded with composite resin. After 24 hours of storage in 37oC and 500 rounds of thermocycling, the specimens were tested in a shear at a crosshead speed of 1.0 mm/min. The results were statistically analyzed using SPSS 11.5 with Kruskal-Wallis and t-test at a significance level of 0.05.Results: The mean±SD in permanent enamels using CSEB and ABSE were 16.10±7.6 and 8.49±2.34 MPa, respectively. The same data for the deciduous enamels were 16.08±3.91 and 9.23±3.20 MPa, respectively. After acid etching, SBS for permanent enamel using CSEB and ABSE were 32.05±7.13 and 31.39±6.51 MPa, respectively. The same data for deciduous enamels were 24.73±10.74 and 21.70±6.18 MPa, respectively.Conclusion: The bond strength of CSEB was significantly higher than ABSE adhesive in both primary and permanent teeth. In addition, acid etching leads to increase in the enamel bond strength of both studied adhesives.

Background and Aim: Lateral condensation technique is one of the most frequently used techniques for root canal obturation. There were few studies in order to determine the needed force for spreader penetration and its effect on apical seal. The purpose of this study was the in vitro evaluation of the effect of three spreader forces using the lateral condensation technique and the effect of these forces on root fractures.Materials and Methods: Eighty-five human mandibular premolar single rooted teeth without severe curvature and visible fractures were chosen and randomly divided into three groups. Each group of teeth were obturated on an acrylic model using three forces (1.6, 3 and 4.5 kg) with the lateral condensation technique. The teeth were observed under the stereomicroscope ×6 again for any fracture line following clearing of the teeth and the maximum dye leakage penetration was measured for each tooth. The data were analyzed by using chi-square and Kruskal-Wallis statistical tests.Results: All samples in the positive control group showed dye leakage but in the negative control group no sample showed any leakage. The mean dye penetration for the first (1.6 kg), second (3 kg) and third (4.5 kg) groups was 0.344 mm, 0.153 mm and 0.746 mm, respectively. The 3 kg force for lateral condensation technique produced a significantly better apical seal and less leakage in comparison with the other groups (P<0.05) and more fractures were observed with 4.5 kg force (P<0.05).Conclusion: The best force for lateral condensation in premolar teeth was 3 kg and more pressure could produce more fracture.

Background and Aim: Tooth bleaching decreases enamel microhardness. The aim of this study was to evaluate the changes in microhardness of bleached enamel after applying fluoride and CPP-ACP (casein phosphopeptide –amorphous calcium phosphate).Materials and Methods: In this experimental study, sixty extracted human molars were divided into six groups (ten each). The flatted occlusal surface was covered with nail varnish. In the second, third and fourth groups, tooth bleaching was performed. The first and second groups were positive and negative control groups. In the third and fifth groups, the specimens were covered with sodium fluoride varnish and the fourth and sixth groups underwent CPP-ACP therapy. Subsurface enamel microhardness was determined on the occlusal surface with 300 micron distance from the buccal or lingual surface. One way ANOVA and Tukey post hoc were used for statistical analysis.Results: Microhardness of bleached enamel was significantly lower than the other groups. The teeth treated by fluoride agent or CPP-ACP after bleaching had a significant increase in their microhardness in contrast with the bleached enamel. CPP-ACP and fluoride treatment had no significant effect on sound enamel microhardness. Although using CPP-ACP and fluoride increases the enamel microhardness, there were no significant differences between them.Conclusion: Fluoride and CPP-ACP components increase bleached enamel microhardness.

Background and Aim: One of the most important factors for increasing flexural strength of fiber-reinforced composite (FRC) restorations is the orientation, volume and geometry of reinforcement fibers. The aim of this study was to determine the effect of fiber position and orientation on the flexural strength of FRC specimens.Materials and Methods: In this experimental-laboratory study, five groups (N=8) of test specimens made of one indirect composite were reinforced with pre-impregnated fibers in different positions, orientations or geometry into the rectangle cube specimens (3×3×25 mm3). The control group did not contain fiber reinforcement. The test specimens were stored in distilled water for 1 week at 37oC before testing in a three-point loading test with 1 mm/min cross head speed. Data were statistically analyzed at 0.05 significance level with Kruskal-Wallis and Mann-Whitney tests.Results: The mean flexural strength of six experimental groups had significant differences (p1=0.005 and p2<0.001). The control group showed the lowest initial and final values. The maximum initial flexural strength was seen in the tension group (76.2 MPa) and the maximum final flexural strength was seen in the middle horizontal group (173.9 MPa).Conclusion: Within the limitations of this study, it may be concluded that the position and orientation of the fibers influenced the flexural strength of the fiber-reinforced composites and the most effective position of the fibers was tension side reinforcement.

Background and Aim: Fluoride has an important role in the prevention of caries. This study assessed the efficacy of three types of topical fluoride: fluoride varnish, APF gel (sultan), APF gel (Kimia) in protecting the enamel from demineralization in an in vitro environment.Materials and Methods: Sixty human caries-free premolars where randomly assigned into four groups of 15 specimens. The control group was washed with deionized/distilled water. Weekly gel (Kimia) was treated with APF gel (1.23%) for 2 minutes weekly, weekly gel (Sultan) was treated with APF gel (1.23%) for 60 seconds weekly, weekly varnish fluoride was treated with Durashield (2.26%). Specimens were then placed in a cycle of demineralization (pH=4.3) for 6 hours and remineralization (pH=7) for 17 hours. This pH- cycle was repeated for 3 weeks (21 days). The teeth were sectioned buccolingually and evaluated under polarized light microscope. Then the depth of each lesion was measured from the deepest demineralization point of the lesion. The data were analyzed using Kruskal-Wallis and Dunn test for pairwise comparison.Results: The control group had the deepest lesions (mean depth, 140±37micrometer). The varnish group had the shallowest lesions (mean depth, 60±37 micrometer) with a 75.3% reduction percent. However, there was no significant difference in the depth of demineralization between all fluoride treated groups. The difference between fluoride groups and the control group were significant.Conclusion: Treatment of the enamel of permanent teeth with various topical fluorides significantly inhibited demineralization, but there was no significant difference between varnish or gel application.

Background and Aim: These days, dental composites are very popular because they look good and are similar to human teeth regarding color. Hygroscopic expansion is one of the physical properties of dental composites. A dental composite may lose its efficiency as a restoration material because of water absorption. The objective of this study was to compare the hygroscopic expansion of three dental composites.Materials and Methods: In this experimental study, to assess the effective factors of hygroscopic expansion, we used three different dental composites (Kalore, P90 and Z250). The length of these composites in water and saliva were measured eighteen times in a three-month period. We used the marginal modeling technique, in which the correlation between response data can be included for analysis.Results: The results of marginal modeling showed that the type of composite is significantly related to hygroscopic expansion (P<0.05), demonstrating the highest hygroscopic expansion for P90 and the lowest for Z250. In addition, time as an independent variable had a statistically significant effect on hygroscopic expansion (P<0.05). However, we found no significant difference between the hygroscopic expansion of saliva and water (P>0.05).Conclusion: Overall, our findings showed that hygroscopic expansion is significantly related to the type of composite and time. Therefore, we should utilize the composites with lower hygroscopic expansion (such as Z250) for filling the patients’ teeth.

Background and Aim: Gag reflex is one of the most common problems in dental treatment. All researches performed to reduce or eliminate this reflex were not effective or were time-consuming. The aim of this study was to evaluate the use of Elaeagnus Angustifolia lozenge in controlling gag reflex during dental treatment.Materials and Methods: This study was a randomized double blind controlled trial with convenient sampling on 84 patients that were candidates for radiographic procedures in the School of Dentistry, Isfahan University of Medical Sciences; the cases were randomly divided into two groups of case and control. The case group used Elaeagnus Angustifolia L extracts and the control group used placebo. Fruit extract was formed into lozenge. Before and after intervention, the gag reflex was evaluated by stimulation of the soft palate and pharyngeal tonsils. Data analysis and comparison was performed with SPSS 11 software and Chi-square, McNamara and t tests.Results: The gag reflex significantly decreased in the soft palate region (p<0.001) and pharyngeal tonsils (p<0.001) in the intervention group. In the placebo group, decrease of gag reflex was not significant in any of these locations (p=0.9). The decrease in gag reflex in the soft palate and the pharyngeal tonsils in the case and control groups before and after the intervention showed statistically significant differences (P<0.01).Conclusion: Elaeagnus Angustifolia L. extracts seem to be an effective method to control gag reflex during dental treatment. It may be a confident method to use on dental procedures, especially radiographic procedures.

Background and Aim: The purpose of this study was to evaluate the diagnostic precision of zoom option of Cygnus Ritter CCD intraoral digital sensor compared to original digital radiography in the detection of occlusal dentinal caries.Materials and Methods: Eighty-six extracted premolars with no apparent clinical caries were selected. Two methods were used for radiography; namely, digital radiography using a Cygnus Ritter CCD sensor and then zoom option was applied to the original radiographs. Four maxillofacial radiologists observed the original digital and the same radiographs with zoom option to detect occlusal dentinal caries subsequently recording it in a five-grade scale.Microscopic sections evaluated by a pathologist were used as the gold standard for caries detection. The data were analyzed with a proportion test and processed with SPSS maxillofacial 14 software.Results: Statistical analysis showed a sensitivity of 52.2% (71) (CI: 95%) for zoom option in the detection of occlusal dentinal caries (P<0.05). The specificity was shown as 68.8% (143) (P>0.05). The ppv was calculated as 52.2% (179) (P<0.05) and npv as 68.8% (236) (P<0.05) and the accuracy was 62.2% (214) (P<0.05).Conclusion: The zoom option of Cygnus Ritter CCD sensor showed a significantly higher diagnostic sensitivity, ppv, npv and accuracy compared to original digital radiographs, but the zoom option of that sensor did not show a significantly higher diagnostic specificity compared to original digital radiographs.

Background and Aim: The density of Gutta-percha is an important factor in canal seal and root canal treatment success. So, the present study intended to compare the effect of Ni-Ti and S-S spreaders on the intracanal Gutta-percha weight.Materials and Methods: In this experimental study, 40 simulated canals with 40 degree curvature (group 1 and 2) and 40 simulated canals with 10 degree curves (group 3 and 4) were used. Each block was weighted after cleaning and shaping using Flexmaster rotary instruments. Group 1 and 3 blocks were obturated using Ni-Ti spreaders, while group 2 and 4 blocks were obturated using stainless steel spreaders with Gutta-percha. The simulated canals were again weighted and the difference of the two measurements was calculated as the Gutta-percha weight. The results were analyzed using SPSS software and 2-way ANOVA tests.Results: The analysis showed that there was no significant difference between the four experimental groups. In addition, the effect of the canal curvature, spreader type and the interaction of the variables was not statistically significant.Conclusion: The current study showed that different spreader types (Ni-Ti or S-S) do not affect the Gutta-percha weight of the root canal obturation.

Background and Aim: Tooth color assessing is very important in esthetic dentistry. The aim of this article was to study tooth color prevalence of 20-30-year-old patients and also presentation of a simple method for color assessment.Materials and Methods: One thousand fifty nonsmoker volunteers (501 men). In a light, distance and angle constant condition the left maxillary incisors were photographed with a digital camera (Canon G9) using a retractor. The pictures were studied with Adobe Photoshop CS5 software. The color of the middle 1/9 of the tooth was measured in L*a*b* system. In the exact above condition vita pan classical shade guide was photographed in direction of neutral background. These pictures were studied with Adobe Photoshop CS5 and L*a*b* average was measured for the middle 1/9 of each sample. After measurement of DE* for each person and vita pan classical shade guide, minimum DE* was chosen for each tooth as the color of that tooth. Finally, the effect of colored liquid drinks was assessed.Results: The most popular findings were A3.5 (16.85%) A3 (14.85%) and B1, B2 (9.8%). The results of this study showed that the L* average in nonsmokers who drank colored liquids more than twice a day in comparison to noncolored liquid users was lower. The a* and b* average in this group was higher than noncolored liquid users.Conclusion: The most common findings were A3.5 (16.85%) A3 (14.85%) B1, B2 (9.8%). Tooth color assessment with a digital camera and computerized study is simple and cheap but very sensitive.