Effect of laser irradiation on root canal walls after final irrigation with 17% EDTA or BioPure MTAD: X-ray diffraction and SEM analysis.

OBJECTIVE: To evaluate the effect of diode laser irradiation on crystallographic and morphologic characteristics of root canal walls after final irrigation with either 17% EDTA or BioPure MTAD. METHOD AND MATERIALS: Root canals in 60 single-rooted teeth were instrumented using a rotary Ni-Ti system. The teeth were randomly divided into three groups (n = 20) based on the final irrigants: group 1, saline; group 2, 17% EDTA; and group 3, MTAD. Each group was further divided into two subgroups (n = 10). Subgroup A received diode laser irradiation at a wavelength of 810 nm and an output power of 2 W for 5 × 5 seconds, while subgroup B received no irradiation. A paired t test was used to compare mean dentinal erosion before and after irradiation in each group. Specimens were analyzed using SEM and x-ray diffractometery. One-way ANOVA and a post hoc Tukey test were used to evaluate dentinal erosion between groups. Kruskal-Wallis and Mann-Whitney U tests were used to evaluate any significant differences in the amount of dentin erosion between the groups. RESULTS: SEM micrographs showed closed dentinal tubules in the control group, while in unlased BioPure MTAD and EDTA groups, clean root canal walls were evident. Erosion was mostly seen in EDTA-treated teeth, while an increase of erosion degree was noted on root canal walls after additional laser irradiations. After irrigation and laser irradiation, the XRD spectrums indicated sharper peaks of EDTA, which showed a slight crystallographic change compared with the other groups. EDTA made changes in the mineralization of dentin due to its higher accumulation on the dentinal wall surface and produced significant degrees of erosion in comparison with MTAD by changing the physical properties of the root canal wall surface. These undesirable changes can be enhanced by further laser irradiation. CONCLUSION: Results confirm that a diode laser in combination with BioPure MTAD have minimum effect on the chemical properties of root canal dentin while having good smear layer removal properties. The results of the present study indicated that a diode laser in combination with Biopure MTAD might be suggested as a final management of the root canal system prior to canal obturation.

The efficacy of foam cleaners in removing debris from two endodontic instruments.

OBJECTIVE: To compare the efficacy of ProFile File cleaner and a nanostructured foam in removing debris from two rotary nickel-titanium instruments during and after instrumentation. METHOD AND MATERIALS: Twenty mandibular premolars were decoronated and instrumented up to either no. 40.04 RaCe (no. 40.04) or K3 (no. 40.04) instruments (n = 10). Each group of files was randomly divided into two groups: ProFile File cleaner and Nano Foam cleaner. The instruments were examined under a scanning electron microscope (SEM) before and after placement into the canals. Subsequently, instruments were introduced into each cleaner and examined again under SEM. The amount of debris removal from the instruments was determined by ImageJ software. Data were subjected to Kruskal-Wallis and Mann-Whitney tests at a .05 level of significance. RESULTS: The amount of debris removal was significantly different between the groups (P = .002). The amount of debris removed was significantly higher in K3 with Nano Foam cleaner than ProFile File cleaner (P = .009). CONCLUSION: Nanostructured foam can remove debris from endodontic files, especially from those with complex cross-section. This method is recommended to help optimize debris removal with the further possibility of instrument sterilization and reduced risk of cross-contamination.

The reliability of artificial neural network in locating minor apical foramen: a cadaver study.

INTRODUCTION: The purpose of this study was to evaluate the accuracy of the artificial neural network (ANN) in a human cadaver model in an attempt to simulate the clinical situation of working length determination. METHODS: Fifty single-rooted teeth were selected from 19 male cadavers ranging in age from 49-73 years. Access cavities were prepared, a file was placed in the canals, and the working length was confirmed radiographically by endodontists. The location of the file in relation to the minor apical foramen was categorized as long, short, and exact by the ANN, by endodontists before extraction, and stereomicroscopically after extraction. The results were compared by using Friedman and Wilcoxon tests. The significance level was set at P <.05. RESULTS: The Friedman test revealed a significant difference among groups (P < .001). There were significant differences between data obtained from endodontists and ANN (P = .001) and data obtained from endodontists and real measurements by stereomicroscope after extraction (P < .002). The correct assessment by the endodontists was accurate in 76% of the teeth. ANN determined the anatomic position correctly 96% of the time. The confidence interval for the correct result was 64.16-87.84 for endodontists and 90.57-101.43 for ANN. CONCLUSIONS: ANN was more accurate than endodontists' determinations when compared with real working length measurements by using the stereomicroscope as a gold standard after tooth extraction. The artificial neural network is an accurate method for determining the working length.

The effect of some fluids on surface oxidation and amount of released iron of stainless steel endodontic files.

Endodontic files come in contact with blood, infected pulp tissue, and irrigating solutions during root canal therapy. Some instruments such as stereomicroscopy and scanning electron microscopy are used to observe corrosion of endodontic files which are complicated and dependent on preparation methods. Having knowledge of the corrosion and ion release of endodontic files can help in drawing firm deductions as to which files would perform better in the clinical scenario. Therefore, we have used energy dispersive X-ray analysis and an atomic absorption spectrophotometer to track oxygen on the surface and iron in the exposed media to observe the oxidative rate of the media. In this study, corrosion by blood was higher than other biological fluids, but less than with sodium hypochlorite (NaOCl). Observations of energy dispersive X-ray analysis and atomic absorption spectrophotometer results demonstrated that after exposure the amount of oxygen on the surface and surrounding areas increased. Therefore, the files should be rinsed as soon as possible during and after use to hinder the oxidation rate, but blood may produce a different behavior and it might be considered as a decreased risk of broken stainless steel files remaining in the root canal after treatment.

Back-scattered and secondary electron images of scanning electron microscopy in dentistry: a new method for surface analysis.

OBJECTIVE: A scanning electron microscope (SEM) is a popular tool for investigating the root canal surface to visualize dentinal tubules, the smear layer and various root canal filling materials in endodontics. Most of the SEM micrographs taken in endodontic research are in secondary electrons (SE) mode, in which the topographic view of a subject can be demonstrated without giving any information about the real structure. Back-scattered electron (BSE) images are also used, which reveal some information about the internal structure while providing no topographic details. The aim of this study was to investigate the possibility of using back-scattered (BSE) and secondary electron (SE) mode of scanning electron microscopy (SEM) together for obtaining detailed information about biomaterials in relation to dental structures. MATERIALS AND METHODS: Mesiobuccal roots of four permanent maxillary molars were cleaned and shaped with rotary instruments. Two samples were obturated with gutta-percha and sealer. After 2 weeks, gutta-perch was removed using rotary instruments and chloroform. In the other phase of the study, white mineral trioxide aggregate was mixed and packed into five glass tubes and exposed to blood, deionized water, synthetic tissue fluid and egg white. All the samples were prepared for visualization under SE and BSE modes of SEM to observe the characteristics of material remnants and surface structures. RESULTS: BSE mode illustrated different grey scale views which made it possible to differentiate dentin chips from filling material remnants on the surface of root canal dentin. In addition, SE mode focused on image topography, while a BSE detector showed new texture formation on the surface of white mineral trioxide aggregate exposed to proteinaceous fluids such as blood or egg white. CONCLUSIONS: Mapping BSE and SE micrographs helped us to better understand the structure of materials on the surface of root canal dentin and MTA. Moreover, analysis of structure of materials on the surface of root canal dentine and MTA can be performed better by mapping of BSE and SE micrographs.

Application of mercury intrusion porosimetry for studying the porosity of mineral trioxide aggregate at two different pH.

OBJECTIVE: To evaluate a novel method of detecting and comparing the porosity of white Mineral Trioxide Aggregate and Portland cement at two different pH. MATERIALS AND METHODS: Cylindrical specimens (n = 120) were prepared from hydrated ordinary white Portland Cement (WPC) (n = 60) and white Mineral Trioxide Aggregate (WMTA) (n = 60) and exposed to environments with pH of 4.4 (n = 30) or 7.4 (n = 30). The pore size distribution and total pore volume were detected using Mercury Intrusion Porosimetry. Data were analyzed by analysis of variance and post-hoc Tukey or Tamhane test (p = 0.05). RESULTS: The pore volume of WMTA was significantly lesser than WPC at both pH (p < 0.05). The surface tension of mercury was taken as 480 (N/m) and the contact angle 141.3° for both materials. Pores were consistently found in all specimens. Total pore volumes for WPC and WMTA (cubic centimeter/gram) were 0.1954 and 0.1023, respectively, while the diameter of the pores ranged from 50-100 Å and 20-50 Å, respectively. CONCLUSIONS: Mercury Intrusion Porosimetry technique is a promising and reliable technique for assessing the porosity of endodontic materials.

Effect of storage temperature on sealing ability and solubility of white mineral trioxide aggregate.

OBJECTIVE: Knowledge about the effect of storage conditions on the clinical performance of Mineral Trioxide Aggregate (MTA) is of great importance for clinicians. The aim of this study was to evaluate the effect of storage temperature on sealing ability and solubility of white MTA. MATERIALS AND METHODS: This study was divided into two parts: sealing ability and solubility tests. Forty single-rooted human pre-molars were divided into three experimental (n = 10) and two control groups (n = 5). The root canals were instrumented and root apices were resected. Root-end cavities were prepared and filled with white MTA stored at 4°C, 25°C or 40°C. Microleakage was evaluated using a protein leakage test with bovine serum albumin at 24-h intervals for 120 days. The solubility test was also performed based on ISO specifications (ISO 2001-6876). Data were analyzed by one-way analysis of variance and post-hoc Tukey test, with a significance level set at p = 0.05. RESULTS: The highest bovine serum albumin microleakage and the highest solubility rates were observed in 4°C followed by 25°C and 40°C groups. At higher temperatures, leakage needed significantly longer times to occur (p < 0.05). CONCLUSIONS: Based on these findings, storage temperature appears to play an important role in the properties and hence clinical outcomes of MTA.

Influence of white mineral trioxide aggregate on inflammatory cells before and after expiry date.

INTRODUCTION: The aim of this study was to compare the effect of subcutaneously implanted white mineral trioxide aggregate (WMTA) on inflammatory reactions before and after expiry date. METHODS: Fifty Wistar rats were used in this study. Polyethylene tubes were filled with WMTA with expiry dates of 2008, 2009, and 2011, and empty ones serving as the controls were implanted into the subcutaneous tissue. The rats were sacrificed at 7-, 14-, 28-, and 60-day intervals. 5-µm sections were stained with hematoxylin and eosin and observed under a light microscope. Inflammatory reactions were categorized as 0, none (without inflammatory cells); 1, mild (inflammatory cells < 25); 2, moderate (25-125 inflammatory cells); and 3, severe (more than 125 inflammatory cells). Statistical analysis was performed with Kruskal-Wallis test. RESULTS: All the experimental materials provoked moderate to severe inflammatory reactions after 7 days, which significantly differed from the control group (P < 0.05). At 14-day interval, WMTA with expiry date of 2008 and the control group elicited mild to moderate infiltration of inflammatory cells. However, WMTA with expiry dates of 2009 and 2011 provoked moderate to severe inflammatory reactions, which were significantly different from WMTA with expiry date of 2008 and the control group (P < 0.05). At 28- and 60-day intervals, the overall inflammation subsided in all the groups to mild to moderate infiltration of inflammatory cells without any significant differences (P < 0.05). CONCLUSION: It seems that the expiry date has less negative effects on the response of inflammatory cells. WMTA keeps its biocompatibility even after expiry date.

The impact of pH on cytotoxic effects of three root canal irrigants.

AIM: Cytotoxicity of root canal irrigants is important due to their close contact with host tissues. This study was to assess the possible impact of pH on cytotoxic effects of MTAD, 17% EDTA, and 2.6% NaOCl on the human gingival fibroblasts using MTT assay. MATERIALS AND METHODS: Human gingival fibroblasts were exposed to the irrigants and their viability was assessed after 1, 6, and 12 h. The pH of the medium was measured in each interval. Light absorption values were measured for each culture medium using Elisa Reader device. RESULTS: NaOCl had significantly less cytotoxicity than EDTA and MTAD. Also irrigants cytotoxicity decreased in 12, 1, and 6 h, respectively. CONCLUSION: It seems that variation of the pH resulted in variation in the cytotoxicity of solutions; i.e., it follows the pattern of the pH variation.

Morphological behavior and attachment of p19 neural cells to root-end filling materials.

Some techniques and instruments like stereomicroscopy and confocal microscopy used for observing neural cells are too complicated and dependent on preparation and cell fixation methods. This may question the results of these methods. Though, we have used scanning electron microscopy on replicated specimens to observe p19 neural cells and their cellular extensions. This manuscript has shown the feasibility of using replica (indirect) method instead of direct methods for observing morphological characteristics of this high sensitive cell line. As neural cells are very sensitive to fixation solutions and processes, we have used replica mode and observed neural cells with a novel indirect method. We have used replica mode in this study to indirectly and noninvasively evaluate the state of p19 neural cells and their cellular extensions.

Effect of manipulative variables on porosity and microleakage of amalgam / Efeito das variáveis manipulatórias da porosidade e microinfiltração do amálgama

For many years, it has been assumed that amalgam restorations posses an acceptable seal at the margins. Indeed, this assumption would appear to be a fundamental requirement for all dental restorations in an oral environment