Experimental study of smear layer and debris remaining following the use of four root canal preparation systems using scanning electron microscopy

Since the use of rotary nickel titanium instruments is an essential part of endodontic treatment, it is important to compare the root canal cleaning ability of these instruments. The aim of this study was to compare the amount of smear layer and debris remaining following the use of four rotary instruments: MTwo, Pro Taper, Race and BioRaCe. A total of 20 mesiobuccal canals of extracted human first molars with apical root curvature of 10 to 20 were selected. Working length of all roots was 19 mm. The roots were randomly divided into four groups of 30 specimens. After the preparation of access cavity, the roots were instrumented using rotary instruments according to the manufacturer's instructions. After each file, the root canal was irrigated with 2.5%sodium hypochlorite. Then the roots were studied under scanning electron microscope. The smear layer and debris scoreswere evaluated by 2 endodontistsusingSchafer and Schlingemannclassification. Kruskal -Wallis and Dunn tests were used for statistical analysis of results. The amount of smear layer produced by MTwo was lower than the other instrumentation techniques and it was significantly lower than that in BioRaCe system [p<0.05]. The amount of debris was also lower in the mentioned group but the difference in this respect between groups was not significant. BioRaCe system had the highest level of remained smear layer while Pro Taper had the highest amount of remained debris. Within the limitations of this study, it was revealed that MTwo instruments had greater capability of removing smear layer and debris than theBioRaCe system

effect of 15% carbamide peroxide bleaching on the shear bond strength of composite to enamel

Carbamide peroxide bleaching has been implicated to adversely affect the bond strength of composite to enamel. The purpose of this study was to evaluate the effect of carbamide peroxide bleaching on the shear bond strength of composite to bleached enamel bonded with a three step total etch system; Scotchbond Multipurpose [SBMP], and two simplified all-in-one systems; Prompt L-Pop [PLP] and i bond. Seventy two human molar teeth were randomly assigned to three control and three experimental groups. The experimental groups were subjected to a%15 carbamide peroxide bleaching system. Twenty four hours later, all the control and experimental groups were bonded with cylinders of composite, using three dental bonding agents. After thermocycling, shear bond strengths were determined by a universal testing machine. The data were evaluated using one way ANOVA and Duncan tests [P < 0.05]. The composite bond strengths of SBMP were 19.52 +/- 15.21 MPa to the unbleached and 7.95 +/- 4.16 MPa to the bleached enamel. For PLP, the unbleached enamel exhibited bond strengths of 9.6612.89 MPa and, the bleached one showed a bond strength value of 5.3910.66 MPa. For i-bond the composite bond strengths were 11.46 +/- 4.31 MPa to the unbleached and 6.41 +/- 2.01 MPa to the bleached enamel. There was a statistically significant difference between the shear bond strength of the control and experimental groups of each dental bonding agent [SBMP, P < 0.001, PLP, P < 0.001, i bond: P = 0.002]. Bleaching with 15% carbamide peroxide used in this study reduced the bond strengths of the composite to the enamel bonded with a three step total etch and two simplified one step all-in-one dental bonding agents

Bioactive glass nanopowder for the treatment of oral bone defects

Osseous defects around dental implants are often seen when implants are placed in areas with inadequate alveolar bone, or around failing implants. Bone regeneration in these areas using bone grafts or its substitutes may improve dental implants prognosis. The aim of this study was to prepare and characterize the bioactive glass nanopowder and development of its coating for treatment of oral bone defects. Bioactive bioglass coating was made on stainless steel plates by sol-gel technique. The powder shape and size was evaluated by transmission electron micropscopy, and thermal properties studied using differential thermal analysis [DTA]. Structural characterization techniques [XRD] were used to analyze and study the structure and phase present in the prepared bioactive glass nanopowder. This nanopowder was immersed in the simulated body fluid [SBF] solution. Fourier transform infrared spectroscopy [FTIR] was utilized to recognize and confirm the formation of apatite layer on prepared bioactive glass nanopowder. The bioglass powder size was less than 100 nanometers which was necessary for better bioactivity, and preparing a homogeneous coating. The formation of apatite layer confirmed the bioactivity of the bioglass nanopowder. Crack-free and homogeneous bioglass coatings were achieved with no observable defects. It was concluded that the prepared bioactive glass nanopowder could be more effective as a bone replacement material than conventional bioactive glass to promote bone formation in osseous defects. The prepared bioactive glass nanopowder could be more useful for treatment of oral bone defects compare to conventional hydroxyapatite or bioactive glass

Effect of different blood contaminated adherent surface treatments on shear bond strength of compomer and composite resin to dentin, using a self etching adhesive

Blood contamination is a common problem in dentistry that can decrease bond strength dramatically which may be affected by methods of decontamination as well. The aim of this study was to evaluate and compare the influence of blood contamination on shear bond strength of composite and compomer to dentin using Prompt L-Pop as an adhesive system. Also, to assess the effectiveness of different surface treatments on the bond strength. In this experimental study, 120 molar teeth were sectioned to provide flat occlusal dentinal surfaces. Specimens were embedded in acrylic resin with the flat surface exposed. The dentinal expose surfaces were polished to 600 grit. The teeth were randomly divided into five groups of twelve specimens [F1-F5] for compomer material and five other groups [Z1- Z5] for composite resin. After application of Promt L-Pop to dentinal surfaces of specimens, the surfaces in all groups, except for F1 and Z1, [as controls] were contaminated with human blood and then one of the following surface treatments was applied. Groups F2 and Z2 without any treatment, groups F3 and Z3 rinsing with water, groups F4 and Z4 rinsing with water and reapplication of adhesive, groups F5 and Z5 rinsing with NaOCl and using Prompt L-Pop again. Restorative materials were applied to treated surfaces using plastic molds. After thermocycling, shear bond strengths, mode of failures and morphology of dentin-material interfaces were evaluated. The data were statistically analyzed using Factorial analysis of Variance, One-Way ANOVA, Duncan, T-student and Chi-Square tests with P<0.05 as the limit of significance. Compomer showed statistically significant higher bond strength in comparison to composite [P<0.001]. Duncan test showed significant differences between all compomer groups, except between groups F4 and F5, and between all composite groups except for groups Z1 and Z4 and for groups Z2 and Z3. Based on the findings of this study, shear bond strength of compomer material was significantly higher than composite. Blood contamination reduced bond strength, but rinsing contaminated dentin with water or NaOCl and reusing Prompt L-Pop increased bond strength in both materials

[ effect of an adhesive system, surface roughness and irregularities on shear bond strength of repaired amalgam]

When an amalgam restoration fails, the repair of existing amalgam restoration with fresh amalgam can be a practical alternative to the replacement of entire restoration. In most studies the bond strength of fresh amalgam to old amalgam is reported lower than the old amalgam itself. Therefore, the purpose of this study was to compare the effect of using adhesive system with surface irregularities and roughness on shear bond strength between fresh and set [old] amalgam. Fifty acrylic cylinders were made and a cavity preparation [6mm diameter by 2 mm high] was made in each cylinder. Forty cavities were filled with amalgam, level with cylinders surface and ten cylinders [control group =Group 1] were filled 5mm higher than the surface of cylinder using split die. After aging of all samples in water at 37°C for 14 days, the first 40 samples were divided into 4 groups and were repaired with fresh amalgam in the following manner. Group 2: with surface irregularities and roughness, group 3: using Panavia F, without surface irregularities and roughness, Group 4: using cement and surface irregularities and roughness, group 5: without cement and without surface irregularities and roughness. After storage in water at 37°C for 7 days, the shear bond strengths of groups were tested. Mean shear bond strengths and standard deviations [MPa] for groups were: in Group 1 [control]: 36 +/- 4.8, Group 2: 31.26 +/- 2.70, Group 3: 8.07 +/- 1.34, Group 4: 13.05 +/- 1.83 and in Group 5 no bond was seen. ANOVA revealed statistically significant difference among groups Duncan test indicated that there was a significant difference between each group with the other one. Results of this study didn't reveal any advantages for using Panavia F to increase the bond strength. According to the results obtained from making surface roughness and irregularities compared to the control group, this procedure can be suggested for repairing broken amalgam as an acceptable procedure