Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                
Skip to main content
Nestor Cohenca

    Nestor Cohenca

    The aim of this in vitro study was to determine whether irrigation with apical negative pressure was more ef- fective than traditional positive-pressure irrigation in eradicating Enterococcus faecalis from preshaped root canals.... more
    The aim of this in vitro study was to determine whether irrigation with apical negative pressure was more ef- fective than traditional positive-pressure irrigation in eradicating Enterococcus faecalis from preshaped root canals. Fifty-four extracted mandibular molars were instrumented to produce either a non-tapered or ta- pered preparation, sterilized, inoculated with E. faecalis for 30 days, and then randomly assigned into
    The purpose of this study was to investigate whether the resistance to torsional stress and cyclic fatigue would be improved by the novel R-phase heat treatment by using instruments with identical geometric characteristics. K3XF and K3... more
    The purpose of this study was to investigate whether the resistance to torsional stress and cyclic fatigue would be improved by the novel R-phase heat treatment by using instruments with identical geometric characteristics. K3XF and K3 files with sizes of #30/.04 and #30/.06 were selected for the study (n = 10 per group). To evaluate the torsional resistance, the torsional load and distortion angle at yield, ultimate, and fracture points were recorded. The toughness until fracture was calculated as well. The number of cycles to failure for each instrument was determined to evaluate the cyclic fatigue resistance. Statistical analysis was performed by using the nonparametric Mann-Whitney U test (for torsional resistance) and independent t test (for cyclic fatigue). After torsional and cyclic fatigue tests, all fractured fragments were observed under a scanning electron microscope to evaluate the topographic features of the fractured surfaces. Although K3XF showed superior cyclic fatig...
    The aim of this randomized controlled clinical trial was to investigate the antimicrobial efficacy of traditional positive pressure (PP) irrigation compared with apical negative pressure (ANP) in tapered as well as non-tapered root canal... more
    The aim of this randomized controlled clinical trial was to investigate the antimicrobial efficacy of traditional positive pressure (PP) irrigation compared with apical negative pressure (ANP) in tapered as well as non-tapered root canal preparation techniques. Patients referred for treatment of mandibular permanent molars with necrotic pulps and apical periodontitis were considered for this study. A total of 32 eligible teeth were evaluated based on strict inclusion and exclusion criteria and randomly assigned as follows: Group 1: LightSpeed LSX 0.02 preparation and A NP irrigation (n = 8). Group 2: LightSpeed LSX 0.02 preparation and PP irrigation (n = 8). Group 3: ProTaper preparation and A NP irrigation (n = 8). Group 4: ProTaper preparation and PP irrigation (n = 8). A ll teeth were sampled immediately upon access (S1), after completion of the chemo- mechanical preparation (S2), and one week later after intracanal medication (S3). All samples were microbiologically processed im...
    The aim of this in vitro study was to determine whether irrigation with apical negative pressure was more effective than traditional positive-pressure irrigation in eradicating Enterococcus faecalis from preshaped root canals. Fifty-four... more
    The aim of this in vitro study was to determine whether irrigation with apical negative pressure was more effective than traditional positive-pressure irrigation in eradicating Enterococcus faecalis from preshaped root canals. Fifty-four extracted mandibular molars were instrumented to produce either a non-tapered or tapered preparation, sterilized, inoculated with E. faecalis for 30 days, and then randomly assigned into the following groups: group 1--non-tapered preparation and negative-pressure irrigation, group 2--non-tapered preparation and positive-pressure irrigation, group 3--tapered preparation and positive-pressure irrigation, and group 4--tapered preparation and negative-pressure irrigation. Mesial canals were sampled before and after final irrigation and samples incubated aerobically for 48 hours at 37 degrees C. Scanning electron microscopic analysis confirmed dense bacterial colonies in the positive control, consistent with biofilm formation. A statistically significant...
    To evaluate a structurally mature E. faecalis biofilm developed under anaerobic/dynamic conditions in an in vitro system. An experimental device was developed using a continuous drip flow system designed to develop biofilm under anaerobic... more
    To evaluate a structurally mature E. faecalis biofilm developed under anaerobic/dynamic conditions in an in vitro system. An experimental device was developed using a continuous drip flow system designed to develop biofilm under anaerobic conditions. The inoculum was replaced every 24 hours with a fresh growth medium for up to 10 days to feed the system. Gram staining was done every 24 hours to control the microorganism purity. Biofilms developed under the system were evaluated under the scanning electron microscope (SEM). SEM micrographs demonstrated mushroom-shaped structures, corresponding to a mature E. faecalis biofilm. In the mature biofilm bacterial cells are totally encased in a polymeric extracellular matrix. The proposed in vitro system model provides an additional useful tool to study the biofilm concept in endodontic microbiology, allowing for a better understanding of persistent root canal infections.
    The purpose of this study was to assess in vitro the effect of commonly used gutta-percha solvents on the microhardness of human enamel and dentin. Crowns of human teeth were cut and treated with chloroform, xylene, and halothane.... more
    The purpose of this study was to assess in vitro the effect of commonly used gutta-percha solvents on the microhardness of human enamel and dentin. Crowns of human teeth were cut and treated with chloroform, xylene, and halothane. Treatment consisted of exposing the specimens for 5 or 15 minutes to the test solvents. Acid-treated and saline-treated specimens served as controls. After each treatment period, the specimens were rinsed, dried, and prepared for Vicker's microhardness analysis. Vicker's microhardness values for each specimen were recorded before and after treatment, and the differences were statistically compared. A statistically significant decrease in enamel and dentin microhardness was found in most solvent-treated groups; the amount of the decrease was directly related to the exposure time. Chloroform, xylene, and halothane may cause a significant softening effect on both enamel and dentin. This softening is already apparent after 5 minutes of treatment.
    Apical periodontitis is a common development associated with teeth with necrotic pulp. Although rare, some cases may present further complications, such as neuropathies in areas adjacent to the affected tooth. A case is described in which... more
    Apical periodontitis is a common development associated with teeth with necrotic pulp. Although rare, some cases may present further complications, such as neuropathies in areas adjacent to the affected tooth. A case is described in which mental nerve paresthesia was associated with a non-vital mandibular premolar. Endodontic therapy resolved the paresthesia completely without further clinical complications.
    Variations in tooth morphology present a clinical challenge when endodontic treatment is required. A case of conservative endodontic therapy for a fused mandibular second and third molar is presented.