[Comparison of smear layer removal of root canals with citric acid and EDTA- NaOCl [A SEM study]]

The smear layer is a thin layer composed of organic and inorganic debries which forms on canal walls. Removal of this layer after instrumentation is critical for adaptation between filling material, root walls and apical seal. The aim of this in vitro study was to determine the effect of 30% citric acid and 17% EDTA- 5.25% NaOCl on smear layer removal in the middle third of root canals. In this experimental study, twenty extracted anterior teeth were used. After decoronation, instrumentation was done. The teeth were divided into three groups. After final preparation the canals were irrigated by 10 ml 30% citric acid in group I and 10 ml 17% EDTA followed by 5.25% NaOCI in group 2. In control specimens, normal saline was used. Then the roots were split longitudinally and studied under scanning electron microscope. The photomicrographs were evaluated by X and Y methods. The data was analyzed by Kolmogorov-Smirnov, Leven's, Mann Whitney U and T-student tests. Canal walls were covered with smear layer in the positive control group. in both methods [X, Y], the result showed that canals irrigated with 17% EDTA- 5.25% NaOCL had less smear layer throughout the canal than group irrigated with 30% citric acid. This difference was not statistically significant in both [X, Y] methods. Both 17% EDTA-5.25% NaOCL and 30% citric acid removed the smear layer from root canal walls effectively

Extra oral comparison of smear layer removal from root canals when using phosphoric acid and RCprep-NaOCL: a SEM study

The smear layer is a thin layer of microcrystalline and organic debris which forms due to instrumentation of canal walls. Today, it is known that the smear layer contains bacteria as well as the nutrients necessary for bacteria. However, it is at the same time a barrier against penetration of irrigants and filling materials into dentinal tubules. Thus it is a factor that can cause micro-leakage and treatment failure. Smear layer removal will increase the adaptation between filling material and canal walls, and therefore it improves the overall sealing quality. Obtaining the cleanest canal possible before obturation is one of the goals of Endodontic treatment. The purpose of this in vitro study was to evaluate the smear layer removal ability of the 10% phosphoric acid and RCprep-5.25% NaOCL in the middle third of the root canals. Twenty freshly extracted human mature anterior teeth with single root canals were used in this study. Then the teeth were divided into three groups. Root canal instrumentation was conducted after decrownation of teeth at the CEJ level. Normal saline was used as irrigants during instrumentation in group 1. After final preparation, the canals were irrigated by 10 ml 10% phosphoric acid for 5-min. In group 2, the irrigants used during instrumentation by files coated with RCprep was 2 ml 5.25% NaOCL. At the end, both groups were irrigated with 5 ml normal saline. In 2 control specimens [teeth], normal saline was the only irrigants used during instrumentation. The roots were first split longitudinally, and then one section was randomly selected for further analysis under the electron microscope. The photomicrographs were evaluated by two different investigators [in group 1] and three different investigators [in group 2]. Statistical analysis was performed to detect group differences and student-t test was used to determine the significance level. Canal Walls were covered with smear layer in control group. The results showed that canals irrigated with 10% phosphoric acid had less smear layer throughout the canal walls compared with the group prepared with RCprep that contained 5.25% NaOCL. This difference was statistically significant in method used in group one [P<0.05] only. Based on the findings of this study, 10% phosphoric acid is superior to RCprep - 5.25% NaOCL in terms of removing smear layer from root canal walls

Comparative evaluation of different methods of strengthening in endodontically treated maxillary central incisors with thin root walls

The structural rehabilitation of a pulpless tooth is critically important to ensure a successful restorative outcome following endodontic treatment. A post and core is often indicated for the retention and reinforcement of the final restoration. But, the clinical situation is significantly challenging if the root exhibits immature development or there is a thin root wall that can compromise the prognosis for a long-term successful treatment. The purpose of this in vitro study was to evaluate different methods of intraradicular reinforcement in structurally compromised roots. In this experimental study, seventy two extracted intact maxillary central incisors with similar size, shape and root anatomy were selected. After root canal therapy in 60 teeth, an acrylic laboratory bur was used to thin the cervical area and simulate the thin dentinal walls of immature teeth. The preparation was performed through the palatal access and extended 5mm apical to CEJ. The remaining 12 teeth remained unprepared to serve as positive control group. Cases were randomly divided into six groups of 12 teeth each and restored as follows. In the 12 cervically unprepared teeth [positive controls] the composite resin with dentin bonding agent [DBA] was placed in access cavity and cured for 120 seconds. This technique was also applied to other groups when the access was restored with composite. In the second group, the access cavity was restored with composite only to the level of CEJ. In the third group the cervically prepared teeth were reinforced with cement resin [Enforce] and a prefabricated post was placed in 5mm apical to the CEJ. In the fourth group, the cervically prepared teeth were reinforced with composite resin and DBA by a clear plastic post. In the fifth group the cervically prepared teeth were reinforced with composite resin and dba and a cast post. In the sixth group the cervically prepared teeth were restored with composite resin and dba with a prefabricated post. All of the specimens were mounted by rubberized technique arid tested in the Instron universal testing machine. The fracture loads in samples were analyzed with ANOVA and Duncan tests with p<0.05 as the limit of significance., Significant differences in fracture resistance were observed between the first and second groups compared with others. The highest fracture resistance values were recorded for first group while the lowest were registered for the second group. Fracture resistance of the third, fourth and fifth groups had no significant statistical differences with others and fracture resistance of sixth group was the highest with significant difference [P<0.05]. From this study, it may be concluded that the use of a dba and a composite resin in thin-walled roots reinforces the immature teeth and facilitates the use of post

Effect of different adhesive systems on microleakage at the amalgam/composite interface

Ditching and marginal defects of amalgam restorations can cause microleakage, recurrent carries, pulp hypersensitivity and finally loss of the tooth. The complete replacement of large restoration is time consuming, difficult and may potentially damage the pulp. Therefore in cases were there is no sings of recurrent caries, composite repair can be chosen as an alternative. The purpose of this study was to compare the effect of different bonding agent application on microleakage between flowable composite and amalgam. Standard calss V amalgam preparations were prepared on 60 carries free premolars and the cavities were filled using amalgam. After 24 hours, a 1 mm cavity on the occlusal margin of the class V restorations was prepared and specimens were divided randomly into four treatment groups: First group was filled with flowable composite and Single bond. Second group was filled with flowable composite and SE bond. Third group was filled with flowable composite and Prompt-L-pop. Fourth group Was filled with flowable composite without denting bonding agent. Specimens were thermocycled and sealed with fingernail polish except the composite-amlagam interface, then immersed in basic fuchsine for 24 hours. Specimens were sectioned and microleakage was assessed. The data were analyzed using Kruskal-Wallis test and Mann-Whitney U test. The results indicated that dentin bonding agent is effective in decreasing the degree of microleakage in amalgam-flowable composite interface and also the clearfil SE bond was more effective than Prompt-L-pop. But there was no significant statistical difference in microleakage between SE bond and Single bond. The application of dentin bonding agents in repair of amalgam retoration using flowable composite decreases microleakage but more researches should be performed