Endodontics

The influence of various factors that may affect the outcome of root canal therapy was evaluated in 356 patients 8 to 10 yr after the treatment. The results of treatment were directly dependent on the preoperative status of the pulp and periapical tissues. The rate of success for cases with vital or nonvital pulps but having no periapical radiolucency exceeded 96%, whereas only 86% of the cases with pulp necrosis and periapical radiolucency showed apical healing. The possibility of instrumenting the root canal to its full length and the level of root filling significantly affected the outcome of treatment. Of all of the periapical lesions present on previously root-filled teeth, only 62% healed after retreatment. The predictability from clinical and radiographic signs of the treatment-outcome in individual cases with preoperative periapical lesions cases was found to be low. Thus, factors which were not measured or identified may be critical to the outcome of endodontic treatment. Vol. 16, No. 10, October 1990 204 revealed apical radiolucency. In roots with pulp necrosis but no apical periodontitis, the necrosis was usually restricted to the coronal part of the canal. Of the 267 roots which had been filled earlier, 94 were retreated for the presence of

Due to both its shape and its structural architecture, the mechanics of the pelvic bone are complex. In Finite Element (FE) models, these aspects have often been (over)simplified, sometimes leading to conclusions which did not bear out in reality. The purpose of this study was to develop a more realistic FE model of the pelvic bone. This not only implies that the model has to be three-dimensional, but also that the thickness of the cortical shell and the density distribution of the trabecular bone throughout the pelvic bone have to be incorporated in the model in a realistic way. For this purpose, quantitative measurements were performed on computer tomography scans of several pelvic bones, after which the measured quantities were allocated to each element of the mesh individually. To validate this FE model, two fresh pelvic bones were fitted with strain gages and loaded in a testing machine. Stresses calculated from the strain data of this experiment were compared to the results of a simulation with the developed pelvic FE model.

This study determined the chemical composition, pH, and radiopacity of mineral trioxide aggregate (MTA), and also compared the setting time, compressive strength, and solubility of this material with those of amalgam, Super-EBA, and Intermediate Restorative Material (IRM). X-ray energy dispersive spectrometer in conjunction with the scanning electron microscope were used to determine the composition of MTA, and the pH value of MTA was assessed with a pH meter using a temperature-compensated electrode. The radiopacity of MTA was determined according to the method described by the International Organization for Standardization. The setting time and compressive strength of these materials were determined according to methods recommended by the British Standards Institution. The degree of solubility of the materials was assessed according to modified American Dental Association specifications. The results showed that the main molecules present in MTA are calcium and phosphorous ions. In addition, MTA has a pH of 10.2 initially, which rises to 12.5 three hours after mixing. MTA is more radiopaque than Super-EBA and IRM. Amalgam had the shortest setting time (4 min) and MTA the longest (2 h 45 rain). At 24 h MTA had the lowest compressive strength (40 MPa) among the materials, but it increased after 21 days to 67 MPa. Finally, except for IRM, none of the materials tested showed any solubility under the conditions of this study. 350 Torabinejad et al. Journal of Endodontics

The purpose of this study was to compare the sealing ability of gray mineral trioxide aggregate (GMTA), white MTA (WMTA), and both white and gray Portland cement as furcation perforation repair materials. A total of 120 human mandibular first molars were used. After root canal obturation and preparation of furcal perforations the specimens were randomly divided into four groups of 25 teeth each. In groups A, B, C, and D furcation perforations were filled with WMTA, GMTA, white Portland cement, and type II Portland cement, respectively. Ten teeth were used as positive controls with no filling materials in the perforations and 10 teeth with complete coverage with two layers of nail varnish were used as negative controls. A protein leakage model utilizing 22% bovine serum albumin (BSA) was used for evaluation. Leakage was noted when color conversion of the protein reagent was observed. The controls behaved as expected. Leakage was found in the samples from group A (WMTA), group B (GMTA), and in the two other groups (white and gray Portland cement). There were no statistically significant differences between GMTA and WMTA or white and gray Portland cement, but significant differences were observed between the MTA groups and the Portland cement groups. It was concluded that Portland cements have better sealing ability than MTA, and can be recommended for repair of furcation perforation if the present results are supported by other in vivo and in vitro studies. (J Oral Sci 51, 601-606, 2009)

Mesenchymal stem cells (MSCs) have been isolated from the pulp tissue of permanent teeth (dental pulp stem cells or DPSCs) and deciduous teeth (stem cells from human exfoliated deciduous teeth). We recently discovered another type of MSCs in the apical papilla of human immature permanent teeth termed stem cells from the apical papilla (SCAP). Here, we further characterized the apical papilla tissue and stem cell properties of SCAP using histologic, immunohistochemical, and immunocytofluorescent analyses. We found that the apical papilla is distinctive to the pulp in terms of containing less cellular and vascular components than those in the pulp. Cells in the apical papilla proliferated 2- to 3-fold greater than those in the pulp in organ cultures. Both SCAP and DPSCs were as potent in osteo/dentinogenic differentiation as MSCs from bone marrows, whereas they were weaker in adipogenic potential. The immunophenotype of SCAP is similar to that of DPSCs on the osteo/dentinogenic and gr...

This study characterized the interactions of mineral trioxide aggregate with a synthetic tissue fluid composed of a neutral phosphate buffer saline solution and root canal dentin in extracted human teeth using inductively coupled plasma-atomic emission spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. Mineral trioxide aggregate exposed to synthetic tissue fluid at 37 degrees C released its metallic constituents and produced precipitates with a composition and structure similar to that of hydroxyapatite [Ca10(PO4)6(OH)2-HA]. Endodontically prepared teeth filled with mineral trioxide aggregate and stored in synthetic tissue fluid at 37 degrees C for 2 months produced at the dentin wall an adherent interfacial layer that resembled hydroxyapatite in composition. The authors conclude that Ca, the dominant ion released from mineral trioxide aggregate, reacts with phosphates in synthetic tissue fluid, yielding hydroxyapatite. The dentin-mi...

The purpose of this study was to analyze the type and frequency of defects in nickel-titanium rotary endodontic files after routine clinical use, and to draw conclusions regarding the reasons for failure. All of the files (total: 378, Quantec Series 2000) discarded after normal use from a specialist endodontic practice over 6 months were analyzed. Almost 50% of the files showed some visible defect; 21% were fractured and 28% showed other defects without fracture. Fractured files could be divided into two groups according to the characteristics of the defects observed. Torsional fracture occurred in 55.7% of all fractured files, whereas flexural fatigue occurred in 44.3%. The results indicated that torsional failure, which may be caused by using too much apical force during instrumentation, occurred more frequently than flexural fatigue, which may result from use in curved canals.

Millions of teeth are saved each year by root canal therapy. Although current treatment modalities offer high levels of success for many conditions, an ideal form of therapy might consist of regenerative approaches in which diseased or necrotic pulp tissues are removed and replaced with healthy pulp tissue to revitalize teeth. Researchers are working toward this objective. Regenerative endodontics is the creation and delivery of tissues to replace diseased, missing, and traumatized pulp. This review provides an overview of regenerative endodontics and its goals, and describes possible techniques that will allow regenerative endodontics to become a reality. These potential approaches include root-canal revascularization, postnatal (adult) stem cell therapy, pulp implant, scaffold implant, three-dimensional cell printing, injectable scaffolds, and gene therapy. These regenerative endodontic techniques will possibly involve some combination of disinfection or debridement of infected root canal systems with apical enlargement to permit revascularization and use of adult stem cells, scaffolds, and growth factors. Although the challenges of introducing endodontic tissue engineering therapies are substantial, the potential benefits to patients and the profession are equally ground breaking. Patient demand is staggering both in scope and cost, because tissue engineering therapy offers the possibility of restoring natural function instead of surgical placement of an artificial prosthesis. By providing an overview of the methodological issues required to develop potential regenerative endodontic therapies, we hope to present a call for action to develop these therapies for clinical use. (J Endod 2007;33:377-390)

Various organic acids, ultrasonic instruments, and lasers have been used to remove the smear layer from the surface of instrumented root canals. The purpose of this study was to investigate the effect of a mixture of a tetracycline isomer, an acid, and a detergent (MTAD) as a final rinse on the surface of instrumented root canals. Forty-eight extracted maxillary and mandibular single-rooted human teeth were prepared by using a combination of passive step-back and rotary 0.04 taper nickel-titanium files. Sterile distilled water or 5.25% sodium hypochlorite was used as intracanal irrigant. The canals were then treated with 5 ml of one of the following solutions as a final rinse: sterile distilled water, 5.25% sodium hypochlorite, 17% EDTA, or a new solution, MTAD. The presence or absence of smear layer and the amount of erosion on the surface of the root canal walls at the coronal, middle, and apical portion of each canal were examined under a scanning electron microscope. The results show that MTAD is an effective solution for the removal of the smear layer and does not significantly change the structure of the dentinal tubules when canals are irrigated with sodium hypochlorite and followed with a final rinse of MTAD.

Stem cells from human exfoliated deciduous teeth (SHED) have been isolated and characterized as multipotent cells. However, it is not known whether SHED can generate a dental pulp-like tissue in vivo. The purpose of this study was to evaluate morphologic characteristics of the tissue formed when SHED seeded in biodegradable scaffolds prepared within human tooth slices are transplanted into immunodeficient mice. We observed that the resulting tissue presented architecture and cellularity that closely resemble those of a physiologic dental pulp. Ultrastructural analysis with transmission electron microscopy and immunohistochemistry for dentin sialoprotein suggested that SHED differentiated into odontoblast-like cells in vivo. Notably, SHED also differentiated into endothelial-like cells, as demonstrated by B-galactosidase staining of cells lining the walls of blood-containing vessels in tissues engineered with SHED stably transduced with LacZ. This work suggests that exfoliated deciduous teeth constitute a viable source of stem cells for dental pulp tissue engineering. (J Endod 2008;34:962-969)

Introduction: Effective irrigant delivery and agitation are prerequisites for successful endodontic treatment. Methods: This article presents an overview of the irrigant agitation methods currently available and their debridement efficacy. Results:Technological advances during the last decade have brought to fruition new agitation devices that rely on various mechanisms of irrigant transfer, soft tissue debridement, and, depending on treatment philosophy, removal of smear layers. These devices might be divided into the manual and machineassisted agitation systems. Overall, they appear to have resulted in improved canal cleanliness when compared with conventional syringe needle irrigation. Despite the plethora of in vitro studies, no well-controlled study is available. This raises imperative concerns on the need for studies that could more effectively evaluate specific irrigation methods by using standardized debris or biofilm models. In addition, no evidence-based study is available to date that attempts to correlate the clinical efficacy of these devices with improved treatment outcomes. Thus, the question of whether these devices are really necessary remains unresolved. There also appears to be the need to refocus from a practice management perspective on how these devices are perceived by clinicians in terms of their practicality and ease of use. Conclusions: Understanding these fundamental issues is crucial for clinical scientists to improve the design and user-friendliness of future generations of irrigant agitation systems and for manufacturers' contentions that these systems play a pivotal role in contemporary endodontics. (J Endod 2009;35:791-804)

The purpose of this study was to evaluate the extent of bacterial reduction with nickel-titanium rotary instrumentation and 1.25% NaOCl irrigation. Also, the additional antibacterial effect of calcium hydroxide for >1 wk was tested. Forty-two subjects with radiographic and clinical ...

Introduction: The aim of this study was to determine the diagnostic accuracy of 2 cone-beam computed tomography (CBCT) machines and periapical (PA) radiography in detecting simulated apical lesions created with the smallest dental burs available. Methods: By using mandibles from human cadavers, simulated apical lesions were created and then progressively enlarged in 16 roots by using sizes #1/4, #1/2, #1, #2, #4, and #6 round burs. Imaging was obtained after each enlargement with a Kodak 9000 3D (Kodak) CBCT, a Veraviewpocs 3De (Morita) CBCT, and intraoral digital PA radiography. Specificity and sensitivity at variable decision thresholds were calculated and plotted on receiver operator characteristic curves. The area under the curve (AUC) served as an estimate of diagnostic accuracy. Results: The overall AUCs for Kodak, Morita, and PA radiography were 0.767 (95% confidence interval [CI], 0.743-0.792), 0.753 (95% CI, 0.728-0.779), and 0.584 (95% CI, 0.554-0.615), respectively. The AUCs for Kodak and Morita were both statistically significantly larger than the AUC for all corresponding simulated lesion sizes imaged with PA radiography. Between Kodak and Morita, there were no statistically significant differences in AUCs for any of the corresponding simulated lesion sizes. Conclusions: Both CBCT devices demonstrated poor accuracy in detecting simulated lesions smaller than 0.8 mm in diameter, fair to good accuracy when simulated lesion diameter was between 0.8-1.4 mm, and excellent accuracy when simulated lesions were larger than 1.4 mm in diameter. PA radiography, at best, demonstrated poor diagnostic accuracy for all simulated lesion sizes. (J Endod 2012;38:965-970)

The purpose of this study was to compare the amount of dye leakage (in the presence versus absence of blood) in root end cavities filled with amalgam, Super EBA, IRM, and a mineral trioxide aggregate. After removing the anatomical crowns of 90 extracted human teeth, their roots were instrumented and obturated. Except for their apical 2 mm, the root surfaces were sealed with nail polish. After removal of the apical 2 to 3 mm of each root, a standardized root end cavity was prepared. Five root ends were filled with gutta-percha and no sealer, and another five root ends were filled with sticky wax. These served as positive and negative controls, respectively. The remaining 80 roots were divided into four equal groups and filled with the test materials. For each material, half of the root end cavities were dried prior to placing the filling material. The remaining half were filled after they were contaminated with blood. All 90 roots were then immediately placed in 1% methylene blue dye...

Numerous compounds have been used as root-end filling materials. Based on the results of in vitro and intraosseous implantation tests, mineral trioxide aggregate (MTA) seems to have potential as a root-end filling material. The purpose of this study was to examine the periradicular tissue response of dogs to MTA and amalgam. Lesions were developed in periradicular tissues of 46 roots in six beagle dogs. The canals on half of the roots were instrumented and obturated with gutta-percha and sealer, and their access cavities were sealed with MTA. The remaining root canals were instrumented and obturated with gutta-percha and sealer, and their access cavities were sealed with MTA. The remaining root canals were instrumented and obturated with gutta-percha without root canal sealer. The access cavities of the teeth in this group were left open to the oral cavity. After surgical resection of roots, half of the root-end cavities were filled with amalgam and the rest with MTA. The periradicu...

Vascular endothelial growth factor (VEGF) is a glycoprotein that has the capability to increase vascular proliferation and permeability. VEGF has been found to be expressed in several different types of tumors, and it may contribute to the progression of malignant tumors. Immunostaining for VEGF and factor VIII was performed in normal healthy pulps and in irreversible pulpitis. In both cases the vessels were always positive for VEGF. Our immunohistochemical data show that the expression of VEGF was strongly positive in the inflammatory infiltrate in irreversible pulpitis. VEGF expression in the stromal cells in healthy pulps ranged from 20 to 100% (with a mean of 68.82), and in irreversible pulpitis ranged from 0 to 100% (with a mean of 62.35%); this difference was statistically significant (p ‫؍‬ 0.05). This down-regulation in the stromal cells in irreversible pulpitis could be due to the presence, in a low compliance system such as the dental pulp, of inflammatory infiltrate. VEGF is probably a factor implicated in the etiology and progression of pulpitis. The microvessel density in healthy pulps was 90.00 ؎ 27.5, while, in irreversible pulpitis, it was 56.68 ؎ 21.15. This difference was statistically significant (p ‫؍‬ 0.001). The decrease in microvessel density in irreversible pulpitis could be related to failing vascular function and blood flow decrease.

The purpose of this study was to evaluate the effects of EDTA on smear layer removal and on the structure of dentin, after 1 and 10 min of application. Six extracted single-rooted teeth were instrumented to #60. Apical and coronal thirds of each root were removed, leaving a 5 mm middle third that was then cut longitudinally into two equal segments. Using 10 ml of 17% EDTA solution, halves belonging to the same root were irrigated for 1 and 10 min, respectively. All specimens were subjected to irrigation with 10 ml of 5% NaOCl. Then all the specimens were prepared for SEM evaluation. The results showed that 1 min EDTA irrigation is effective in removing the smear layer. However a 10-min application of EDTA caused excessive peritubular and intertubular dentinal erosion. Therefore we suggest that this procedure should not be prolonged >1 min during endodontic treatment.

The purpose of this study was to compare the ability of ProRoot mineral trioxide aggregate (PMTA) and Root mineral trioxide aggregate (RMTA) as root-end filling materials, and Portland cement (PC) to prevent bacterial leakage through filled root end cavities. Fifty-one extracted human single rooted teeth were cleaned and shaped using a step back technique. The root-ends were resected and a 4 mm deep root-end preparation was made with fissure bur. The teeth were randomly divided into three experimental groups (n=15) and a further six teeth served as controls. Three root-end cavities were filled with gutta-percha without a root canal sealer (positive control) and three remaining were filled with sticky wax, covered with two layers of nail polish (negative control). Root-end cavities in each experimental group were filled with PMTA, RMTA or PC. After attaching the teeth to plastic caps of 9 ml vials, the teeth and the caps were sterilized using Gamma ray. Then the caps with teeth were ...

The fracture of endodontic instruments is a procedural problem creating a major obstacle to normally routine therapy. With the advent of rotary nickel-titanium (NiTi) instruments this issue seems to have assumed such prominence as to be a considerable hindrance to the adoption of this major technical advancement. Considerable research has been undertaken to understand the mechanisms of failure of NiTi alloy to minimize its occurrence. This has led to changes in instrument design, instrumentation protocols, and manufacturing methods. In addition, factors related to clinician experience, technique, and competence have been shown to be influential. From an assessment of the literature presented, we derive clinical recommendations concerning prevention and management of this complication.

This investigation studied the cytomorphology of osteoblasts in the presence of Mineral Trioxide Aggregate (MTA) and examined cytokine production. MTA and Intermediate Restorative Material (IRM) were prepared and placed in separate Petri dishes. Osteoblasts (cell-line MG-63), grown to confluence in Hams F12/Dulbecco's modified Eagle's medium, were seeded into the dishes, which were incubated for 1 to 7 days. The specimens were viewed by scanning electron microscopy. For cytokine evaluation, cells were grown either alone or in other dishes containing the test materials for 1 to 144 h. Media were removed for ELISA analysis of interleukin (IL)-1 alpha, IL-1 beta, IL-6, and macrophage colony-stimulating factor. Scanning electron microscopy revealed healthy cells in contact with MTA at 1 and 3 days; in contrast, cells in the presence of IRM appeared rounded. The ELISA assays revealed raised levels of all ILs at all periods when cells were grown in the presence of MTA; in contrast...

Root canal morphology changes during canal preparation, and these changes may vary depending on the technique used. Such changes have been studied in vitro by measuring cross-sections of canals before and after preparation. This current study used nondestructive high-resolution scanning tomography to assess changes in the canals' paths after preparation. A microcomputed tomography scanner (cubic resolution 34 m) was used to analyze 18 canals in 6 extracted maxillary molars. Canals were scanned before and after preparation using either K-Files, Lightspeed, or ProFile .04 rotary instruments. A special mounting device enabled precise repositioning and scanning of the specimens after preparation. Differences in surface area (⌬A in mm 2 ) and volume (⌬V in mm 3 ) of each canal before and after preparation were calculated using custom-made software. ⌬V ranged from 0.64 to 2.86, with a mean of 1.61 ؎ 0.7, whereas ⌬A varied from 0.72 to 9.66, with a mean of 4.16 ؎ 2.63. Mean ⌬V and ⌬A for the K-File, ProFile, and Lightspeed groups were 1.28 ؎ 0.57 and 2.58 ؎ 1.83; 1.79 ؎ 0.66 and 4.86 ؎ 2.53; and 1.81 ؎ 0.57 and 5.31 ؎ 2.98, respectively. Canal anatomy and the effects of preparation were further analyzed using the Structure Model Index and the Transportation of Centers of Mass. Under the conditions of this study variations in canal geometry before preparation had more influence on the changes during preparation than the techniques themselves. Consequently studies comparing the effects of root canal instruments on canal anatomy should also consider details of the preoperative canal geometry.

This study investigated the marginal adaptation of mineral trioxide aggregate (MTA) as a root-end filling material, compared with commonly used rootend filling materials by scanning electron microscopy (SEM). Eighty-eight single-rooted freshly extracted human teeth were cleaned, shaped, and obturated with gutta-percha and root canal sealer. Following root-end resection and cavity preparation, the root-end cavities were filled with amalgam, Super-EBA, Intermediate Restorative Material (IRM), or MTA. Using a slow-speed diamond saw, 40 roots were longitudinally sectioned into two halves. Resin replicas of resected root ends of the remaining nonsectioned roots were also prepared. After mounting longitudinal sections of roots and resin replicas of resected roots on aluminum stubs, the distance between the test rootend filling materials and surrounding dentin was measured at four points under SEM. Examination of the original samples showed numerous artifacts in the longitudinal sections of the specimens. In contrast, the resin replicas of resected and filled root ends had no artifacts. Statistical analysis of data comparing gap sizes between the root-end filling materials and their surrounding dentin shows that MTA had better adaptation compared with amalgam, Super-EBA, and IRM.

Nowadays, researchers are focusing their attention towards folk medicine for developing better drugs against microbial infections. The present study aimed to evaluate the inhibitory activity of crude extracts from Garcinia griffithii plant. The plant materials were extracted using solvents with different polarities. The solvent extracts were screened and then tested for antimicrobial activities. It was found that the polar extracts, i.e. methanol and ethyl acetate, showed higher antimicrobial activities than the non polar (Hexane) extract. In previous study, screening test for phytochemicals constituents of the plant showed that, the leaf extract of the plant possessed the active principles e.g. terpenoids, tannins, saponins and glycosides. The antimicrobial activity of the extracts was assayed against four bacteria and two fungal strains using the agar disc diffusion method by indicating the presence of the clear inhibition zones around each disc. Methanolic extract showed the highest inhibition zone of (18±2.4mm) against S. aureus compared with ethyl acetate (10±0.05 mm) and hexane extracts (8±0.05 mm).

An in vitro study was performed to determine the number and the type of root canals, their ramifications, transverse anastomoses, apical foramina locations, and frequency of apical deltas in a Turkish population. One thousand four hundred human permanent teeth were injected with India ink, decalcified, and cleared after the length of each was measured. The examination of root canal systems of the teeth was based on Vertucci's classification. The findings were used to classify the teeth into four groups. Variable root canal configurations were found in the second premolar and the mesiobuccal roots of first and second molars among the maxillary teeth and in all of the mandibular teeth, except the mandibular second premolar.

The objective of this study was to review the literature with respect to the root and canal systems in the maxillary first molar. Root anatomy studies were divided into laboratory studies (in vitro), clinical root canal system anatomy studies (in vivo) and clinical case reports of anomalies. Over 95% (95.9%) of maxillary first molars had three roots and 3.9% had two roots. The incidence of fusion of any two or three roots was approximately 5.2%. Conical and C-shaped roots and canals were rarely found (0.12%). This review contained the most data on the canal morphology of the mesiobuccal root with a total of 8399 teeth from 34 studies. The incidence of two canals in the mesiobuccal root was 56.8% and of one canal was 43.1% in a weighted average of all reported studies. The incidence of two canals in the mesiobuccal root was higher in laboratory studies (60.5%) compared to clinical studies (54.7%). Less variation was found in the distobuccal and palatal roots and the results were reported from fourteen studies consisting of 2576 teeth. One canal was found in the distobuccal root in 98.3% of teeth whereas the palatal root had one canal in over 99% of the teeth studied. (J Endod 2006;32:813-821)

In addition to having good sealing ability, root end filling materials should "ideally" have some antibacterial activity to prevent bacterial growth. This investigation compared the antibacterial effects of amalgam, zinc oxide-eugenol, Super EBA and a mineral trioxide aggregate on nine facultative bacteria Streptococcus fecalis, Streptococcus mitis,

Leakage and scanning electron microscopic studies have shown that a mineral trioxide aggregate (MTA) used as root end filling material permits significantly less leakage and has better adaptation than other commonly used root end filling materials. Because these materials are in contact with the periradicular tissues, their cytotoxicity should be evaluated before in vivo tests.

The prevalence of black-pigmented Bacteroides species in the root canals of 72 teeth with apical periodontitis was evaluated. Twenty-two of the canals contained one or more species of black-pigmented Bacteroides. Bacteroides intermedius (14 strains) and Bacteroides endodontalis (5 strains) were most common. Of the species Bacteroides gingivalis, Bacteroides Ioeschei, and Bacteroides denticola, 2, 3, and 1 strains, respectively, were isolated. The median number of bacterial cells recovered from the root canals containing blackpigmented Bacteroides was 2.8 x 105 and from the other canals 3.0 x 103. The mean number of strains was 7.9 and 3.3, respectively. Sixteen of the 22 root canals containing black-pigmented Bacteroides species were associated with acute apical abscesses and purulent drainage through the root canal. The other six teeth with black-pigmented Bacteroides were asymptomatic. One additional abscess was present among the 72 cases. This root canal contained Actinomyces israelii and Actino-~yces naeslundii.

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.

A comparative study of the fatigue resistance of engine-driven nickel-titanium endodontic instruments was performed, aiming to access the influence of the cutting flute design and of the size of the files that reach the working length in curved canal shaping. Geometrical conditions similar to those found in practice were used. Series 29 #5 ProFile, together with #6 and #8 Quantec instruments, were tested in artificial canals with a 45-degree angle of curvature and 5-mm radius of curvature. It was observed that the size of the instrument, which determines the maximum strain amplitude during cyclic deformation, is the most important factor controlling fatigue resistance. The effect of heat sterilization on the fatigue resistance of the instruments was also examined. The results obtained indicate that the application of five sterilization procedures in dry heat increases the average number of cycles to failure of unused instruments by approximately 70%.

To evaluate the fracture resistance and failure types of modified H-designed intradental short retention preparation for computer-aided design/computer-assisted manufacture (CAD/CAM) restorations, in cases where no ferrule is possible. Method and Materials: A combined finite element analysis and in vitro testing was employed. Forty extracted single-rooted premolars were selected and prepared for the following four groups (n = 10 per group): Group A, H-post preparation restored with glass-ceramic crowns; group B, H-post preparation restored with lithium disilicate crowns; group C, endocrowns (negative control group); and group D, 2-mm ferrule preparation and restoration with fiber posts (positive control). After cementation, specimens were loaded to fracture (1 mm/min) in a universal testing machine. The data were analyzed using Kolmogorov-Smirnov, Shapiro-Wilk test, one-way ANOVA, followed by post-hoc Scheffé test and chisquare test. Results: The H-post group restored with lithium disilicate crowns (group B) presented higher fracture resistance compared to the H-post group with glass-ceramic crowns (group A) and the endocrowns (group C). Among the failure analysis, only specimens of group C were all repairable after fracture load test, while the specimens of remaining groups A, B, and D accounted for 90%, 70%, and 50% repairable fracture modes, respectively. Conclusion: The modification of the short intracoronal restoration anchorage profile may be a valid concept to improve the retention and fracture resistance, given that the materials are adjusted for this purpose in terms of mechanical resistance and internal adaptation. Numerical evaluations and future in vitro studies may help to select the best designs and materials. (doi: 10.3290/j.qi.a32634)

The purpose of this study was to analyze the physical properties and chemical compositions of a new experimental cement (NEC) and compare them with mineral trioxide aggregate (MTA); pH, working time, setting time, dimensional changes following setting, flow, film thickness, and chemical composition of NEC and MTA were assessed. For chemical compositions, all specimens were imaged and analyzed by scanning electron microscopy and electron probe microanalysis (EPMA). The physical properties were performed according to ISO 6876:2001. Working time, pH, and dimensional changes of NEC and MTA showed similar results. Shorter setting time was obtained with the NEC compared with MTA (p Ͻ 0.05). The NEC showed more flow than MTA. In addition, the film thickness of the NEC was considerably less than the MTA (p Ͻ 0.01 and p Ͻ 0.001, respectively). EPMA investigations indicated that lime (CaO) was the dominant compound in NEC and MTA; however, other compounds were significantly different. It was concluded that the chemical composition of NEC is different compare with MTA; it can be concluded that the NEC exhibits acceptable physical properties. (J Endod 2008;34:990 -993)

This study examined the effect of vapor lock on canal debridement efficacy by testing the null hypothesis that there is no difference between a "closed" and an "open" system design in smear layer and debris removal by using a side-vented needle for irrigant delivery. Roots in the closed system were sealed with hot glue and embedded in polyvinylsiloxane to restrict fluid flow through the apical foramen during cleaning and shaping. For the open system, the apical foramen was enlarged and connected to the external environment via a channel within the polyvinylsiloxane to permit unrestricted fluid flow. Smear and debris scores were evaluated by using scanning electron microscopy and analyzed by using Cochran-Mantel-Haenszel statistic. No difference in smear scores was detected between the 2 systems at all canal levels. Significant differences in debris scores between the 2 systems were found at each canal level: coronal (P < .001), middle (P < .001), and apical...

The combination of sodium hypochlorite (NaOCl) and chlorhexidine (CHX) results in the formation of a precipitate. The aim of this study was to determine the minimum concentration of NaOCl required to form a precipitate with 2.0% CHX. This was accomplished with a serial dilution technique. X-ray photon spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to qualify and quantify the precipitate. A color change and precipitate were induced in 2.0% CHX by 0.023 % and 0.19 % NaOCl, respectively. Both XPS and TOF-SIMS showed the presence of para-chloroaniline in an amount directly related to the concentration of NaOCl used. Until this precipitate is studied further, its formation should be avoided by removing the NaOCl before placing CHX into the canal. (J Endod 2007;33:966 -969)

The purpose of this study was to compare the incidence of dentinal defects (fractures and craze lines) after canal preparation with different nickel-titanium rotary files. Two hundred sixty mandibular premolars were selected. Forty teeth were left unprepared (n ϭ 40). The other teeth were prepared either with manual Flexofiles (n ϭ 20) or with different rotary files systems: ProTaper (Dentsply-Maillefer, Ballaigues, Switzerland), ProFile (Dentsply-Maillefer), SystemGT (Dentsply-Maillefer), or S-ApeX (FKG Dentaire, La Chaux-de-Fonds, Switzerland) (n ϭ 50 each). Roots were then sectioned 3, 6, and 9 mm from the apex and observed under a microscope. The presence of dentinal defects was noted. There was a significant difference in the appearance of defects between the groups (p Ͻ 0.05). No defects were found in the unprepared roots and those prepared with hand files and S-ApeX. ProTaper, ProFile, and GT preparations resulted in dentinal defects in 16%, 8%, and 4% of teeth, respectively. Some endodontic preparation methods might damage the root and induce dentinal defects. (J Endod 2009;35:236 -238)

Root perforations adversely affect the prognosis of teeth. Inadequacy of the repair materials has been a contributing factor to the poor outcome of repair procedures. Mineral trioxide aggregate (MTA) is a relatively new material that is being successfully used to repair perforations. The purpose of this study was to evaluate the success rate of root perforation repairs using MTA. A list of all of the perforation repairs completed with MTA at an endodontic residency program was obtained. Sixteen cases were included that met the criteria for this study. Pretreatment, immediate posttreatment, and at least 1 year follow-up radiographs were evaluated in a double-blind manner to determine the presence or absence of any pathologic changes adjacent to the perforation site. The results showed that all 16 cases demonstrated normal tissue architecture adjacent to the repair site at the recall visit. Teeth with existing lesions showed resolution of the lesion, and teeth without preoperative lesions continued to demonstrate absence of lesion formation at the follow-up visit. Based on the results of this study, MTA provides an effective seal of root perforations and shows promise in improving the prognosis of perforated teeth that would otherwise be compromised.