Healing process of dog dental pulp after pulpotomy and pulp covering with mineral trioxide aggregate or Portland cement.

Considering several reports about the similarity between the chemical compositions of the mineral trioxide aggregate (MTA) and Portland cement (PC), the subject of this investigation was to analyze the behavior of dog dental pulp after pulpotomy and direct pulp protection with these materials. After pulpotomy, the pulp stumps of 26 roots of dog teeth were protected with MTA or PC. Sixty days after treatment, the animal was sacrificed and the specimens removed and prepared for histomorphological analysis. There was a complete tubular hard tissue bridge in almost all specimens. In conclusion, MTA and PC show similar comparative results when used in direct pulp protection after pulpotomy.

Mineral trioxide aggregate repair of lateral root perforations

This study was conducted to observe the healing process of intentional lateral root perforation repaired with mineral trioxide aggregate (MTA). Forty-eight root canals of dogs' teeth were instrumented and filled. After partial removal of the filling, an intentional perforation was made with a bur in the lateral area of the root. The perforations were repaired with MTA or Sealapex (control group). Histological analysis occurred 30 and 180 days after treatment. Results showed no inflammation and deposition of cementum over MTA in the majority of the specimens. In the 180-day period, Sealapex exhibited chronic inflammation in all the specimens and slight deposition of cementum over the material in only three cases. In conclusion, MTA exhibited better results than the control group. Copyright © 2001 by The American Association of Endodontists.

Reaction of rat connective tissue to implanted dentin tubes filled with a white mineral trioxide aggregate.

The purpose of this paper was to study the reaction of rat subcutaneous connective tissue to the implantation of dentin tubes filled with white mineral trioxide aggregate (MTA), a material that will be marketed. The tubes were implanted into rat subcutaneous tissue and the animals were sacrificed after 7 and 30 days. The undecalcified pieces were prepared for histological analysis with polarized light and von Kossa technique for mineralized tissues. Granulations birefringent to polarized light and an irregular structure like a bridge were observed next to the material; both were von Kossa positive. Also, in the dentin wall tubules a layer of birefringent granulations was observed. The results were similar to those reported for gray MTA, indicating that the mechanisms of action of the white and gray MTA are similar.

Effect of different dye solutions on the evaluation of the sealing ability of Mineral Trioxide Aggregate.

Alkaline materials have shown incompatibility with methylene blue dye in leakage experiments. The goal of the present study was to analyze the effect of different dyes on the evaluation of the apical sealing ability of Mineral Trioxide Aggregate root-end fillings. Fifty-six extracted human canines were submitted to root canal instrumentation and obturation. After apical resection, retrograde cavities were prepared and teeth were randomly divided into four experimental (n = 13) and two control groups (n = 2). The following root-end filling materials were used: groups 1 and 2--Pro Root MTA (Dentsply), groups 3 and 4--zinc oxide-eugenol cement (ZOE). Teeth in groups 1 and 3 were immersed in 2% methylene blue solution, while teeth in groups 2 and 4 were immersed in 0.2% rhodamine B in a reduced pressure environment for 48 hours. Teeth were then longitudinally sectioned and leakage was evaluated. Results were submitted to statistical analysis (ANOVA and Tukey's test). Group 1 presented the least leakage (p < 0.05). It was concluded that the evaluation of the sealing ability of MTA is influenced by the dye used, since this material presented better sealing ability when evaluated with Methylene Blue, but was similar to ZOE when evaluated with rhodamine B.

Ex vivo biocompatibility tests of regular and white forms of mineral trioxide aggregate

Aim: To examine the genotoxicity and cytotoxicity of regular and white mineral trioxide aggregate (MTA) ex vivo by the single-cell gel (comet) assay and trypan blue exclusion test, respectively. Methodology: Aliquots of 1 × 10 4 Chinese hamster ovary cells were incubated at 37°C for 3 h with grey and white forms of MTA at final concentrations ranging from 1 to 1000 μg mL -1. The negative control group was treated with vehicle control phosphate buffer solution for 3 h at 37°C and the positive control group was treated with methyl metasulfonate (at 1 μg mL -1) for 1 h at 37°C. After incubation, the cells were centrifuged at 180 g for 5 min and washed twice with fresh medium and resuspended with fresh medium. Each individual treatment was repeated three times consecutively to ensure reproducibility. Parameters from single-cell gel (comet) and cytotoxicity assays were assessed by the Kruskal-Wallis nonparametric test. Results: Neither compounds produced genotoxic effects with respect to the single-cell gel (comet) assay in all concentrations evaluated. In the same way, the dose-response relationships of all compounds tested at concentrations ranging from 1 to 1000 μg mL -1 on cell viability assessed by the trypan blue assay displayed no statistically significant differences (P > 0.05) for either endodontic material. Conclusions: Regular (grey) and white MTA are not genotoxins and do not induce cellular death. © 2006 International Endodontic Journal.

Clinical and radiographic evaluation of pulpotomies employing calcium hydroxide and trioxide mineral aggregate

This study utilized clinical and radiographic examinations to compare the effectiveness of calcium hydroxide paste and mineral trioxide aggregate (MTA) for pulpotomies of primary molars in children. Ninety primary molars that showed clinical and radiographic indications for pulpotomy treatment were selected. The pulpotomies were performed in two sessions, using a corticosteroid/ antibiotic solution as therapeutic dressing. The sample was divided into two groups of 45 teeth, in which the pulpal remains were protected with either calcium hydroxide paste (Group 1) or MTA (Group 2). Radiographs were taken immediately and at 3-, 6-, and 12-month follow-up appointments. Three teeth in Group 1 failed after three months, while two cases failed after six months and one more failed at one year. Two failures were found in Group 2 at the 12-month follow-up. These results indicate that both materials may be utilized for pulpotomies in primary teeth.

Genotoxicity in primary human peripheral lymphocytes after exposure to regular and white mineral trioxide aggregate

Objective: Taking into consideration that DNA damage plays an important role in carcinogenesis, the purpose of this study was to evaluate whether regular and white mineral trioxide aggregate (MTA) are able to induce genetic damage in primary human cells. Study design: Human peripheral lymphocytes obtained from 10 healthy volunteers were exposed to 2 presentation forms of MTA at final concentrations ranging from 1 to 1000 μg/mL for 1 hour at 37°C. The negative control group was treated with vehicle control (phosphate buffer solution, PBS) for 1 hour at 37°C and the positive control group was treated with hydrogen peroxide (at 100 μM) for 5 minutes on ice. Results were analyzed by the Friedman nonparametric test. Results: The results pointed out that either regular or white MTA in all concentrations tested did not induce DNA breakage in human peripheral lymphocytes as depicted by the mean tail moment. Conclusion: In summary, our results indicate that exposure to MTA may not be a factor that increases the level of DNA lesions in human peripheral lymphocytes as detected by single cell gel (comet) assay. © 2006 Mosby, Inc. All rights reserved.

Histological evaluation of the bone repair using mineral trioxide aggregate combined to a material carrier

The aim of this study was to present a possible carrier for MTA, monoolein gel, with the objective to maintain this material in the place that was inserted and verify if this procedure is able to optimize its action. The data were evaluated by histomorphometric method and submitted to statistical analysis. The histological responses observed in this study indicate that the MTA is a reliable material and should be considered effective in bone periapical defects and the monoolein gel was capable to maintain the MTA in situ.

Evaluation of two mineral trioxide aggregate compounds as pulp-capping agents in human teeth

Aim: The present randomized, controlled prospective study evaluated the histomorphological response of human dental pulps capped with two grey mineral trioxide aggregate (MTA) compounds. Methodology: Pulp exposures were performed on the occlusal floor of 40 human permanent pre-molars. The pulp was capped either with ProRoot (Dentsply) or MTA-Angelus (Angelus) and restored with zinc oxide eugenol cement. After 30 and 60 days, teeth were extracted and processed for histological examination and the effects on the pulp were scored. The data were subjected to Kruskal-Wallis and Conover tests (α = 0.05). Results: In five out of the 40 teeth bacteria were present in pulp tissue. No significant difference was observed between the two materials (P > 0.05) in terms of overall histological features (hard tissue bridge, inflammatory response, giant cells and particles of capping materials). Overall, 94% and 88% of the specimens capped with MTA-Angelus and ProRoot, respectively, showed either total or partial hard tissue bridge formation (P > 0.05). Conclusions: Both commercial materials ProRoot (Dentsply) and MTA-Angelus (Angelus) produced similar responses in the pulp when used for pulp capping in intact, caries-free teeth. © 2009 International Endodontic Journal.

Experimental observation of infrared spectral enlargement in As 2S3 suspended core microstructured fiber

The development of chalcogenide glasses fibers for application in the infrared wavelength region between 1 and 10 μm is a big opportunity. More particularly, the possibility to generate efficient non linear effects above 2 μm is a real challenge. We present in this work the elaboration and optical characterizations of suspended core microstructured optical fibers elaborated from the As2S3 chalcogenide glass. As an alternative to the stack and draw process a mechanical machining has been used to the elaboration of the preforms. The drawing of these preforms into fibers allows reaching a suspended core geometry, in which a 2.5 μm diameter core is linked to the fiber clad region by three supporting struts. The zero dispersion wavelength is thus shifted towards 2 μm. At 1.55 μm our fibers exhibit a dispersion around -250 ps/nm/km. Their background level of losses is below 0,5 dB/m. By pumping them at 1.55 μm with a ps source, we observe self phase modulation as well as Raman generation. Finally a strong spectral enlargement is obtained with an average output power of - 5 dbm. © 2010 SPIE.

Nonlinear effects generation in suspended core chalcogenide fibre

In this work we report our achievements in the elaboration and optical characterizations of low-losses suspended core optical fibers elaborated from As2S3 glass. For preforms elaboration, alternatively to other processes like the stack and draw or extrusion, we use a process based on mechanical drilling. The drawing of these drilled performs into fibers allows reaching a suspended core geometry, in which a 2 μm diameter core is linked to the fiber clad region by three supporting struts. The different fibers that have been drawn show losses close to 0.9 dB/m at 1.55 μm. The suspended core waveguide geometry has also an efficient influence on the chromatic dispersion and allows its management. Indeed, the zero dispersion wavelength, which is around 5 μm in the bulk glass, is calculated to be shifted towards around 2μm in our suspended core fibers. In order to qualify their nonlinearity we have pumped them at 1.995 μm with the help of a fibered ns source. We have observed a strong non linear response with evidence of spontaneous Raman scattering and strong spectral broadening. © 2011 SPIE.

Effect of different radiopacifying agents on the physicochemical properties of white portland cement and white mineral trioxide aggregate

Introduction: The aim of this study was to evaluate the pH, calcium ion release, setting time, and solubility of white mineral trioxide aggregate (WMTA) and white Portland cement (WPC) combined with the following radiopacifying agents: bismuth oxide (BO), calcium tungstate (CT), and zirconium oxide (ZO). Methods: Fifty acrylic teeth with root-end filling material were immersed in ultrapure water for measurement of pH and calcium release (atomic absorption spectrophotometry) at 3, 24, 72, and 168 hours. For evaluation of setting time, each material was analyzed according to the American Society for Testing and Materials guidelines 266/08. The solubility test was performed according to American National Standards Institute/American Dental Association specification no. 57/2000. Solubility, setting time, and pH values were compared by using analysis of variance and Tukey test, and the values of calcium release were compared by the Kruskal-Wallis and Miller tests. The significance level was set at 5%. Results: The pH and calcium release were higher at 3 and 24 hours. WPC was the material with the higher values for both properties. WMTA had the greatest solubility among all materials (P <.05). All radiopacifiers increased the setting time of WPC, and WMTA had the shortest setting time among all materials (P < .05). Conclusions: All materials released calcium ions. Except for WPC/CT at 168 hours, all materials promoted an alkaline pH. On the basis of the obtained results, ZO and CT can be considered as potential radiopacifying agents to be used in combination with Portland cement. Copyright © 2012 American Association of Endodontists.

Immobilization and stabilization of a bimolecular aggregate of the lipase from Pseudomonas fluorescens by multipoint covalent attachment

The soluble lipase from Pseudomonas fluorescens (PFL) forms bimolecular aggregates in which the hydrophobic active centers of the enzyme monomers are in close contact. This bimolecular aggregate could be immobilized by multipoint covalent linkages on glyoxyl supports at pH 8.5. The monomer of PFL obtained by incubation of the soluble enzyme in the presence of detergent (0.5% TRITON X-100) could not be immobilized under these conditions. The bimolecular aggregate has two amino terminal residues in the same plane. A further incubation of the immobilized derivative under more alkaline conditions (e.g., pH 10.5) allows a further multipoint attachment of lysine (Lys) residues located in the same plane as the amino terminal residues. Monomeric PFL was immobilized at pH 10.5 in the presence of 0.5% TRITON X-100. The properties of both PFL derivatives were compared. In general, the bimolecular derivatives were more active, more selective and more stable both in water and in organic solvents than the monomolecular ones. The bimolecular derivative showed twice the activity and a much higher selectivity (100 versus 20) for the hydrolysis of R,S-2-hydroxy-4-phenylbutyric acid ethyl ester (HPBEt) in aqueous media at pH 5.0 compared to the monomeric derivative. In experiments measuring thermal inactivation at 75 °C, the bimolecular derivative was 5-fold more stable than the monomeric derivative (and 50-fold more stable than a one-point covalently immobilized PFL derivative), and it had a half-life greater than 4 h. In organic solvents (cyclohexane and tert-amyl alcohol), the bimolecular derivative was much more stable and more active than the monomeric derivative in catalyzing the transesterification of olive oil with benzyl alcohol. © 2012 Elsevier Ltd. All rights reserved.

Combined therapy with mineral trioxide aggregate, and guided tissue regeneration for a large radicular cyst: A 13-year follow-up

Biomaterials such as membrane barriers and/or bone grafts are often used to enhance periapical new bone formation. A combination of apical surgery and these biomaterials is one of the latest treatment options for avoiding tooth extraction. In case of periapical lesions, guided tissue regeneration (GTR) is attempted to improve the self-regenerative healing process by excluding undesired proliferation of the gingival connective tissue or migration of the oral epithelial cells into osseous defects. In many cases, GTR is necessary for achieving periodontal tissue healing. This report describes the healing process after surgery in a challenging case with a long-term followup. In this case report, endodontic surgery was followed by retrograde sealing with mineral trioxide aggregate (MTA) in the maxillary right central incisor and left lateral incisor. Apicectomy was performed in the maxillary left central incisor and a 1-mm filling was removed. The bone defect was filled with an anorganic bone graft and covered with a decalcified cortical osseous membrane. No intraoperative or postoperative complications were observed. After 13 years of follow-up, the patient showed no clinical signs or symptoms associated with the lesion and radiographic examination showed progressive resolution of radiolucency. In conclusion, the combination of apical surgery and regenerative techniques can successfully help the treatment of periapical lesions of endodontic origin and is suitable for the management of challenging cases.

Aggregate shape and tensile strength measurement

Tensile strength (TS) of soil aggregates is an important indicator of soil quality. However, TS varies with aggregate shape. Thus, the objective of this study was to quantify the influence of aggregate shape on TS and propose a shape standardization protocol to increase accuracy in the measurement of TS. The latter was determined on 7,560 aggregates divided into three shapes, (i) irregular shape (IS), (ii) spherical shape (SS), and (iii) flat surface (FS), while preserving the inherent structure of the aggregate. The aggregates with IS had a larger range in the TS (306 kPa) because of the shape variability when compared with SS (238 kPa) and FS (129 kPa). The TS determined in aggregates with FS had smaller coefficient of variation (46%) in comparison with those of IS (70%) and SS (66%), indicating that the aggregate uniformity reduced the influence of shape on the TS. A smaller force (42.12 kPa) was needed to rupture aggregates with FS than IS (58.43 kPa) and SS (56.89 kPa) because of better force distribution in causing the tensile stress. The use of aggregates with the FS enables an accurate assessment of TS in relation to a wide range of management treatments. Copyright © 2013 by Lippincott Williams & Wilkins.