JOURNAL OF ISLAMIC DENTAL ASSOCIATION OF IRAN (MAJALLAH-I-DANDANPIZISHKI)
Year:2009 | Volume:21 | Issue:2 (71)|Papers Count:14

Background and Aim: Many researchers have reported that, constant use of diamond burs can reduce their cutting efficacy during cavity preparation. The aim of this study was to evaluate the effect of changes in diamond bur sharpness on dentin bond strength when using self-etch bonding system.Materials and Methods: A total of seventy-two caries-free human 3rd molars were included in this in-vitro investigation. The teeth were sectioned in occlusal surface in order to expose dentin, and then were randomly divided into four groups. For dentin preparation, a fine diamond bur was used in group 1, a new coarse diamond bur was used in group 2, a used coarse diamond bur was used in group 3 after applying on porcelain for two minutes, and a used coarse diamond bur was used in group 4 after it was applied on porcelain for ten minutes. Unique composite capsules were bonded to all dentin surfaces using Clearfil SE Bond and then cured. After storage for 24 hours in 37oC distilled water, the bonded teeth were subjected to shear testing by using Instron testing machine. The bond strengths were calculated and recorded as failure. Bond strength data were analyzed by One-Way ANOVA and Tukey tests.Results: The mean (Standard Deviation) of shear bond strength in each group can be reported as follows: 22.2Mpa (3.38) for group one, 18.05Mpa (4.54) for group two, 24.5Mpa (5.69) for group three and the figure was 22.4Mpa (4.52) for group four. The statistical analysis demonstrated that Shear bond strength of new coarse diamond bur preparations were significantly (P<0.001) less than fine or used diamond burs.Conclusion: Used diamond burs of different durations can affect dentin bond strength of SE Bond self etch bonding system. Accurate type of bur and adhesive selection are essential in optimizing dentin adhesion to self-etching adhesives.

Background and Aim: The mechanical properties of composite resin have significant effect on performance and success of a restorative procedure. The aim of present investigation was to evaluate the compressive strength of conventional and pack able composite materials.Materials and Methods: A stainless steel mold of 4 mm in diameter by 6 mm in height was used to fabricate 50 study specimens. The cylindrical specimens were divided in five groups (n=10). The materials used in this study were Alert, Charmfil Plus, P60, Z100 and Spectrum. Following photo polymerization by using Radi Plus light curing unit (SDI Limited), the specimens were stored in distilled water at 37oC for 48 hours. The specimens were subjected to compressive stress using mechanical testing machine (Zwick/Roell) at cross head speed of 0.5 mm/min. One-Way ANOVA and Tukey's Post-hoc tests were employed to determine group differences and the significance level if any of the restorative materials could show significant difference among others.Results: There were significant statistical differences between groups (P<0.05). Z 100 showed the highest and Charmfil Plus demonstrated the lowest amount of compressive strength. There was no significant statistical difference between Z 100 and P 60, but, differences were significant between Z 100 and other materials.Conclusion: Based on the findings of this investigation, the compressive strength of packable composites was not proving better than conventional composites.

Background and Aim: The main objective of using adhesive material is the improvement of restorative materials bonding to dentin surface in clean environment. The aim of this study was to investigate the effect of EDTA on bond strength of composite resin to dentin surface when used at different times and concentrations prior to application of adhesive systems by employing Scanning Electronic Microscope (SEM).Materials and Method: A total of 100 dentin samples were prepared from 50 human premolars. These samples were divided into two groups according to bonding type ( Clearfil SE Bond =group I, Futurbond NR=group II ) and each one was classified 5 subgroups according to time and concentration of EDTA as follows: 1- Control. 2- EDTA 15%, 30 seconds. 3- EDTA 15%, 60 seconds. 4- EDTA 24%, 30 seconds. 5- EDTA 24%, 60 seconds. These samples were conditioned and composite cylinders were adhered to them. After 500 cycles of thermocycling, the testing for micro-shear bond strength was conducted on these samples. Another 10 samples were demineralized for 30 seconds with 6NHCL and deproteinized with 2.5% Naocl for 10 minutes, air dried with desiccators and viewed under SEM. Data were analyzed using one-way as well as three-way ANOVA and Tukey tests.Results: The mean Micro-shear bond strength in group I (Clearfil SE bond) were: 31.88 (±13) for subgroup 1, 28.4 (±13) in subgroup 2, 29.8 (±9) in subgroup 3, 29.2 (±11) in subgroup 4, and 32.7 (±12) in subgroup 5. The mean Micro-shear bond strength in group 2 (Futurbond NR): were: 22.6 (±10) for subgroup 1, 28.5 (±9) in subgroup 2, 27.3 (±10) subgroup 3, 32.4 (±15) in subgroup 4, and 31.1 (±14) in subgroup 5.There were no significant differences between the samples conditioned and the ones not conditioned with EDTA, time and the concentration of EDTA applied and also the two bonding types.Conclusions: EDTA conditioning prior to use of the two bonding agents under investigation in this study did not improve the bonding strength of the self etch systems, neither did the time and the concentration of EDTA applied.

Background and Aim: Application of sodium ascorbate as an antioxidant and calcium hydroxide as a buffering agent has been recommended after bleaching .The aim of this study was to investigate the effect of these two materials on shear bond strength of composite resin attached to bleached enamel.Materials and Methods: This in-vitro investigation used 60 human sound premolars. They were randomly divided into five groups (n=12). Buccal enamel surfaces were flattened by using a trimmer machine and silicon carbide paper. The samples in negative control (NC) group were not bleached, while all others were bleached with 35% hydrogen peroxide gel for 5 days. Composite cylinders were bonded in positive control (PC) group immediately after bleaching; in delayed bonding (DB) group after one week; in sodium ascorbate (SA) and calcium hydroxide (CH) groups after 40 hours of treatment with these two materials, respectively. The specimens were thermocycled (5-55oC, 500 cycles) 24 hours after bonding and they were subjected to shear bond testing by using universal machine. Statistical analyses were carried out to identify group differences and Kruskal–Wallis and Mann–Whitney tests were used to detect the significance level.Results: Group differences revealed that, the lowst mean of bond strength belonged to the calcium hydroxide group the difference of which was significant compared with the other groups (P<0.006). The positive control group had lower bond strength in comparison with the negative control, sodium ascorbate and delay bonding groups (p<0/001) .But the difference among other groups was not significant.Conclusions: Both one week delay and using sodium ascorbate treatment could significantly increase the bond strength of composite resin to bleached enamel, while the use of calcium hydroxide had an adverse effect on composite resin bond strength.

Background and Aim: There are several methods of measuring Convergence Angle in posterior single PFM crown. The aim of the present study was to compare the reliability of these methods.Materials and Methods: This experimental study was conducted with twenty selected stone dies, numbered 1 to 20. The convergence angles were measured and recorded by five last year dental students using manual and computer assisted methods. The manual methods used were: 1. Photocopy machine, 2. Digital camera, 3. Analogue camera (photography), 4. Overhead projector; the computer assisted methods were: 5. Scanner machine and 6. Microscope. Data were analyzed using One Way Random Effect, and SPSS version 11 statistical software.Results: Coefficient of reliability for methods 1 to 6 was 0.9981, 0.9988, 0.9986, 0.9991, 0.9957, and 0.9994 respectively. No significant difference was detected among these methods and all were found to be reliable.Conclusion: There were no significant differences among the methods evaluated. Moreover, all methods were found to be significantly reliable and can be used for measuring convergence angles.

Background and Aim: Suture removal time is one of the most controversial issues after third molar surgery. The purpose of this study was to evaluate wound healings in relation with suture removal time after 5, 8, and 10 days following the third molar surgery.Materials and Methods: This clinical trial study with double blind method was conducted on 90 patients in need of third molar surgery. Patients were non-smokers and had no history of known systemic diseases. Sex and age range were similar in all study groups. The same suturing material as well as post surgery medications was used for all participants. Patients were then divided into 3 groups in order to have their suture removal at 5th (group A), 8th (group B), and 10th (group C) day following the surgery. Statistical analysis was conducted and Kruskal-Wallis and c2 tests were used for analyzing group differences and significance level by evaluating wound tension, wound healing and inflammation status.Results: Group A, was almost without wound tension or had just a negligible amount of tension. Group B had 33% and group C had 17% of this condition (P<0.01). Moderate to severe inflammation was measured 70% in group A, 23.3% in group B and 20% in group C (P<0.001). Wound healing was 83% in group A, 17% in group B and 10% in group C (P<0.001). Amount of tension in suture was 13.3% in group A, 70% in group B and 86.7% in group C (P<0.001).Conclusion: Based on the results of this study, it seems that time factor plays an important role in wound healing. This is true as long as the suture tension is not reduced. Therefore, 8 days after the surgery is the best time for sutures removal.

Background and Aim: Successful preparation and treatment of root canal depends on the compatibility between filling material and canal walls. On the hand, proper crown repair most often require post and core preparation. The aim of this study was to compare the effect of immediate versus delayed root canal preparation for post-space on apical seal using 2 types of sealers Apatite root sealer and AH26.Materials and Methods: This experimental study was conducted on 76 anterior teeth with single root canals. These teeth were sectioned from the cervical area which left at least 12 mm of root portion. All teeth were randomly divided into 4 groups. There were 2 positive and 2 negative control teeth aside from 15 experimental teeth in each group. After cleaning and shaping, root canals were filled with Gutta Percha, using lateral condensation method and AH26 sealer (in groups 1 and 2), and Apatite root sealer (in groups 3 and 4). Post-spaces were immediately prepared in groups 1 and 3, leaving the last 4 mm of Gutta Percha in root canals. The root canals in groups 2 and 4 were kept in 100% moisture for a week and post-spaces were prepared with the same technique. Finally, all teeth were kept in Indian ink for 72 hours. All teeth were then demineralized in citric acid and demoisturized using ethylic alcohol. Photographs were taken from different angles using stereomicroscope connected to computer with 40x magnification in order to detect dye preparation. Photographs were evaluated by 2 independent individuals separately and dye penetration was measured. Data were analyzed using Two-Way ANOVA and Tukey tests.Results: The immediate AH26 group had the lowest and the delayed Apatite root sealer had the highest rate of apical leakage and dye penetration. A significant difference was detected between immediate and delayed methods of post-space preparation (P<0.01). There was no significant difference between the 2 types of sealers used (P=0.426).Conclusion: Immediate post-space preparation before sealer setting had less apical leakage. No significant difference was detected between AH26 and Apatite root sealers.

Background and Aim: There are different methods of oral health education for child population. Theater show is a method that has not received enough attention until now. The aim of this study was to evaluate the effect of using theater show on dental health education in Yazd female elementary students.Materials and Methods: This was a quasi experimental study performed by using pre- and post-test method in Iran over the year 2004. One elementary school from each region of the city was selected. Twenty students from each grade of each school were included in the study (n=200). The information on knowledge, attitudes and practice of oral health were collected by using a valid and reliable questionnaire before and after theater show performance. Data were analyzed using SPSS and Wilcoxon signed rank test.Results: This study showed that the theater show could improve knowledge, attitude and proper oral health practice of children. The effect of the theater show on knowledge was more than attitude and was more on attitude than practice (P<0.001). Only literacy on the part of mothers was significantly correlated with practice (P=0.021). There were significant correlations between Knowledge (P=0.020), Attitude (P=0.0001) and oral health Practice (P=0.022) with students' grade level.Conclusion: This study showed that using theater show for oral health education, could improve the oral health related knowledge, attitude and proper oral health practice by elementary school students.

Background and Aim: Use of pit and fissure sealants are safe and effective preventive procedures for occlusal caries. Long term retention of pit and fissure sealants is essential for their success and depends partly on the method of fissure preparation. Recently, new technologies such as laser and air abrasion have been used to increase bond of sealants. This in vitro study compared the effect of laser with other methods (air abrasion and conventional) on retention of sealants by measuring micro shear bond strength.Materials and Methods: This experimental in-vitro study used sound premolar teeth. They were sectioned mesiodistally in order to use the buccal and lingual surfaces. Samples were randomly divided into 3 groups. Group I samples were prepared with 37% acid phosphoric. Group II samples were exposed to air abrasion and then acid etching. Group III specimens were exposed to Er,Cr:YSGG (2W power) and then acid etching. Bonding was applied on all samples and sealants in microbore tygon tube (0.7 mm in diameter and 1mm height) were cured. Data on micro shear bond strength was measured and analyzed statistically by One-Way ANOVA and Tukey tests.Results: Mean micro shear bond strength for group I, II, III, were 23.51 (±6.9), 39.09 (±15.11), 21.44 (±6.18) MPa respectively. A significant statistical difference (P<0.01) was detected in group II (air abrasion with etching) compared with other groups.Conclusion: Considering the smooth surface enamel used in this study, it can be concluded that irradiation of the laser before etching cannot increase fissure sealant retention. However, air abrasion technique before etching showed greater sealant retentions.

Background and Aim: Sanosil is a brand new disinfectant that is composed of H2O2 and traces of Ag with considerable effectiveness. The aim of this study was to evaluate the effectiveness of Sanosil on disinfecting dental devices and instruments.Materials and Methods: This laboratory-based study was conducted on 60 samples that were collected before (n=30) and after (n=30) administration of Sanosil from the same spots on dental instruments. The samples were cultured on blood agar and chocolate agar and were incubated in 37oC for 24 hours. The effect of Sanosil was investigated by counting the number of microbial colonies after determining the standard laboratory species’ type and subtype. The data were analyzed by using SPSS version 14 and Chi-square test for determining the significance level, and alpha error was set at 0.05.Results: The isolated microorganisms were mainly: Staphylococcus aureus, Streptococcus viridans, coagolase negative Staphylococcus, E.coli, Bacillus cereus, Bacillus subtilis and Staphylococcus epidermidis, E.coli Aeromonas hydrophila, corynebacterium, Microccus luteus. From the total samples 90% were free of any bacteria. Microbial load was significantly reduced (P<0.05) after Sanosil application on dental instruments and it also deferred the growth of standard microorganisms in vitro.Conclusion: Sanosil is an effective agent in decreasing bacterial contamination of dental instruments without any adverse effect on the surface of instruments.