Removal of Smear Layer by Two Endodontic Irrigation Solutions and Erbium: Yttrium, Aluminum, Garnet (Er:YAG)Laser. A Scanning Electron Microscope (SEM) Study

INTRODUCTION: The purpose of the present study was to determine the effect of 17% Ethylene,di-amine, tetra-acetic acid (EDTA), 6% phosphoric acid and Erbium: Yttrium, Aluminum, Garnet (Er:YAG) Laser in removing the smear layer by scanning electron microscopy.METHODS: In this study, 80 single-rooted human teeth were selected. Instrumentation was done by use of hand files and step-back technique up to file #40 at apical and file #80 at coronal area. During instrumentation, 1ml of 5.25% sodium hypochlorite (NaOCl) was used as irrigation between each file. The teeth were randomly divided into four groups with different methods of smear removal.17% Ethylene, di-amine, tetra-acetic acid was used in group 1, 6% Phosphoric acid in group 2, Erbium: Yttrium, Aluminum, Garnet laser in group 3, and no intervention in group 4 (as control). Roots were then longitudinally sectioned and prepared for scanning electron micrograph in cervical, middle and apical areas. Data were analyzed by Kruskal-Walis, Mann-Whitney, Friedman and Wilcoxson tests (P<0.05).RESULTS: The results showed a significant difference in smear layer removal between three methods in favor of the EDTA (P<0.001) and Phosphoric groups (P<0.001) with no significant difference between them (P=0.49). Although Er:YAG laser showed some limited ability to remove the smear layer, the effectiveness was not significantly different from the control group (P=0.157).CONCLUSION: Based on the findings of this study, EDTA and Phosphoric acid were effective methods to remove smear layer from the root canal walls but Er:YAG laser showed less efficacy compared to the other experimental groups

Graphite Application and Different Powers of Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) Laser on Dentin Surface Changes: A Scanning Electron Microscopy Study

INTRODUCTION: Various methods have been used for the treatment of dentine hypersensitivity such as dentifrices, sealants and different types of lasers. The aim of this study was to evaluate the effect of Neodimium:Yttrium-Aluminium-Garnet (Nd:YAG) laser in association with graphite on the dentin morphologic changes.METHODS: In this experimental in vitro study, 16 freshly extracted third molars were selected. 5 specimens with the dimensions of 2×2×1 mm from root trunk were prepared. Specimens were randomly divided into five groups: group 1 (control, no laser irradiation). Group 2, 3 irradiated by Nd:YAG laser 0.5 and 1W, output power respectively. Group 4, 5 smeared with graphite and then irradiated by Nd: YAG laser 0.5 and 1W output power. Samples were prepared for scanning electron microscopy. Number and diameter of dentinal tubules were determined in different groups and analyzed with the Kruskal-wallis and Mann-Whitney tests (SPSS 16).RESULTS: The number of tubules had significant difference between all groups (P<0.001), except group 1 in comparison with group 2 (P> 0.05), and group 3 in comparison with group 4 (P> 0.05). Micro-cracks and rupture of melted dentin materials were seen in group 4 and 5.CONCLUSION: According to the findings of this study, smearing with graphite on dentin surface increase the absorption of Nd:YAG laser energy and reduced the diameter and number of open dentinal tubules

Histologic Evaluation of Three Treatment Methods for Direct Pulp Capping of Cat’s Canine

INTRODUCTION: Direct pulp capping (DPC) is coverage of exposed pulp by a biocompatible material after traumatic or carious exposure. The purpose of this procedure is to seal against bacterial leakage, stimulate dentinal barrier formation, and maintain the vitality of pulp. Several factors contribute to the consequence of this treatment such as material and the procedural technique. The aim of this study was to histological evaluation of three treatment methods (Laser+MTA, Laser+Ca(OH)2 and MTA alone) in direct pulp capping of cat's canines. MATERIALS AND METHODS: Thirty six canine teeth of 9 cats were selected for this experimental study. After anesthesia, the teeth were exposed under isolated condition. The teeth were randomly divided into three treatment groups. In group I, the pulp exposures were covered by Mineral Trioxide Aggregate (MTA) alone. In group II, the pulps after treating with Er: YAG laser, were covered by MTA. In group III, treating with laser and covering with Ca(OH)2 was performed. All cavities were filled by Amalgam after DPC. After 4 months, the animals were sacrificed and block sections were prepared. Then, the specimens were histologically evaluated according to the scores that designed by a pathologist. The data was analyzed by Mann-Whitney and Chi-square tests with significant level of 95%. RESULTS: Dentinal barrier was formed in all groups. Laser+MTA group showed nearly similar results to other groups in dentinal barrier formation, type and intensity of inflammatory responses and soft tissue changes (P>0.05). CONCLUSION: Although Laser+MTA had slightly better effects, but this difference was not statistically significant. Based on this study, it seems that laser treatment has no effect on outcome of DPC

Microleakage of five separated nickel-titanium rotary file systems in the apical portion of the root canal

Background: The aim of this study was to evaluate the rate of apical microleakage following the fracture of five types of nickel–titanium rotary file systems (ProTaper Universal, Mtwo, RaCe, Revo-s, HeroShaper) in the apical one-third of the canal. Materials and Methods: In this laboratory experiment, 49 mandibular premolars were collected and randomly divided into seven groups. Root canal treatment was performed by five different rotary file systems with different cross-sections. All files, except in the control groups, were scratched at the 3-mm end by a handpiece. After separation of the apical end of the file in the root canal, the apical seal was measured, using the fluid infiltration technique. Data were analyzed in SPSS, using one-way ANOVA and Tamhane's T2 tests at P < 0.05. Results: The Hero Shaper and RaCe files showed the highest (3.14 μL/min) and the lowest (2.51 μL/min) rates of microleakage over time, respectively. There were significant differences between the Hero Shaper and RaCe files and between Hero Shaper and ProTaper files in terms of microleakage (Tamhane's T2 tests, P < 0.05) Conclusion: The presence of a separated file and its cross-section type affects the apical microleakage

In vitro evaluation of two methods of ultrasonic irrigation on marginal adaptation of MTA plugs in open apex teeth: A SEM analysis

Context: Different factors can affect the marginal adaptation of MTA. Aims: The present study was designed to investigate the effect of two ultrasonic irrigation methods on the marginal adaptation of MTA plug in open apex teeth by scanning electron microscope. Settings and Design: Thirty single mature teeth were included in this in vitro experimental prospective study. Materials and Methods: A total of 5 mm thickness of MTA plug was inserted at the end of the canals and after 24 h an ultrasonic file was used to irrigate the canals and remove the MTA remnants. Teeth were randomly divided into three groups: In the first and second groups, the canals were irrigated for 1 min by 2.5% sodium hypochlorite as #25 ultrasonic file was in direct contact and 1 mm away from MTA plug, respectively. The third group was not irrigated and left as control. A total of 1 mm transverse sections were prepared through the coronal and the apical parts of MTA plug and specimens were prepared for SEM analysis. The extent of gap was measured linearly under SEM device. Statistical Analysis Used: Statistical analysis of the results was performed using the kruskal-Wallis test by SPSS software ver.18(a = 0.05). Results: There was no significant difference between groups regarding the marginal gap size in apical (P: 0.17) and coronal sections (P: 0.33). However, the mean marginal gap size was higher in apical section compared to coronal section. Conclusions: It can be concluded that ultrasonic irrigation dose not adversely affect the marginal adaptation of MTA plugs

Петролого-геохимические черты рудовмещающего субстрата в гидротермальных месторождениях золота. Ч. 1. Петрология околорудного метасоматизма

Актуальность исследования заключается в необходимости корректировки и углубления геологической (металлогенической) составляющей теории образования гидротермальных месторождений золота, в рамках которой противоречивые представления о геологической обусловленности рудообразования (источниках энергии и металлоносных флюидов) укладываются в четыре конкурирующих, исключающих одна другую, гипотезы, вследствие чего невозможно разработать комплекс эффективных прогнозно-поисковых критериев оруденения. Цель исследования: посредством использования альтернативной существующим методологии и следующих из нее методов петролого-геохимических исследований рудовмещающего, в том числе черносланцевого, субстрата получить данные (достоверные факты), способные обеспечить: 1) доказательство принадлежности эпигенетических минеральных ассоциаций этапа рудообразования в толщах околорудно-измененных углеродистых (черных) сланцев, вопреки популярным представлениям, к метасоматическим формациям и, как следствие, вещественно-генетической однородности апочерносланцевых зональных метасоматических колонок (ореолов) с образованными в несланцевом (кристаллическом) субстрате; 2) на гипсометрических уровнях залегания оруденения доказательство внешних (внепородных) источников золота и сопровождающих металлов, сосредоточенных в рудах месторождений, образованных в толщах черных сланцев.The relevance of the research is caused by the necessity to correct and elaborate on geological (metallogenical) component of the hydrothermal gold deposits formation theory within the framework of which the conflicting ideas about ore-formation geological making (energy and metalliferous fluids sources) go in four competing hypotheses eliminating one other. Therefore it is impossible to develop a complex of effective forecast-search mineralization criteria. The main aim of the study is to prove the belonging epigenetic mineral associations at the ore-formation stage in near-ore alterating black shales series to metasomatic formations, contrary to the wide-spread ideas, and, as consequence, material-genetic similarity of apoblackshales zoning metasomatic columns (haloes) with those, formedin non-shale (crystalline) substratum; external (non-rock) sources of gold and other metals, concentrated in deposits formed in black shales series

Comparing the sealing properties of mineral trioxide aggregate and an experimental ceramic based root end filling material in different environments

Background: An apical seal is an important factor in achieving success in surgical endodontics. Aim: The purpose of this study was to compare the sealing properties of mineral trioxide aggregate (MTA) with a new ceramic based root end filling material (Cold Ceramic) in different environments. Materials and Methods: One hundred teeth were selected. The root canals were instrumented and obturated. Except for the apical 2 mm, the root surfaces were sealed. After root resection, 3 mm depth root-end cavities were prepared. For each material, roots were divided into 3 equal subgroups and the root-end filling was done in different environments (dry, saliva contaminated, blood contaminated). Five roots served as positive and 5 roots as negative controls. Samples were immersed in 2% methylene blue dye. Roots were sectioned longitudinally and examined under stereomicroscope to record the extension of dye penetration. Results: All experimental groups demonstrated dye penetration. The lowest linear leakage was seen in Cold Ceramic blood contaminated group while the highest leakage was observed in MTA blood contaminated group. The linear dye penetration of both MTA and Cold Ceramic (CC) groups did not show any significant differences among different environments. Also, the difference between MTA and CC was not significant in dry and saliva contaminated subgroups. Only the difference between dye penetration of MTA and CC in blood contaminated subgroups showed significant difference ( P = 0.008). Conclusion: The sealing property of this ceramic based root end filling material (Cold Ceramic) is better than MTA in blood contaminated condition and at least similar to MTA in other conditions

Mechanical or cold lateral compaction: The incidence of dentinal defects

Background: The incidence of dentinal defects may influence the outcome of root canal treatment. The aims of this study were to evaluate and compare the incidence of dentinal defects following root canal obturation with two different techniques. Materials and Methods: A total of 110 mesial roots of human mandibular first molars were selected. Twenty-seven roots were left unprepared as negative controls (NCs). The mesiobuccal canals of 83 roots were prepared using rotary instruments. Twenty-seven roots were left unobturated as positive controls (PCs). Twenty-eight roots were obturated with cold lateral compaction (CLC) technique and the others were obturated with mechanical lateral compaction (MLC) technique. In the CLC and MLC groups, spreader penetration depth was measured by an electromechanical testing machine in canals containing master Gutta-percha cones. After root canal obturation, all the roots were sectioned horizontally at four levels from the apex and evaluated under a stereomicroscope at a magnification of ×40. The presence of dentinal defects was noted. Data were analyzed using the Chi-square and t-tests. Results: The number of defects was not significantly different between the CLC, MLC, and PC groups. The CLC, MLC, and PC groups had significantly more defects compared to the NC group. Conclusion: According to the results of this study, the MLC and CLC techniques were the same in producing dentinal defects