Morphological evaluation of maxillary second molars with fused roots: a micro-CT study.

AIM: To evaluate the internal and external morphologies of fused-rooted maxillary second molars by means of micro-computed tomography (micro-CT) analysis. METHODOLOGY: A total of 100 fused-rooted maxillary second molars from a Brazilian subpopulation were divided into six groups according to the root morphology. The samples were scanned at a resolution of 19.6 µm and evaluated with regard to the external morphology of the roots, the root canal configuration, the percentage frequency of C-shaped canals and isthmuses, as well as the morphology of the root canal system at 1, 2 and 3 mm from the anatomical apex of the fused roots. RESULTS: The most prevalent root canal fusions were type 1, mesiobuccal root fused with distobuccal root (32%), followed by type 3, DB root fused with P root (27%), and type 4, MB root fused with DB root, and P root fused with MB or DB roots (21%). The prevalence of C-shaped root canal systems were 22%. Depending on the type of root fusion, the percentage frequency of isthmuses in the apical level varied from 9.3% to 42.8%, whilst the presence of apical deltas ranged from 18.5% to 57.1% of teeth. CONCLUSIONS: The root canal system of maxillary second molars with fused roots may have a high incidence of merging canals, isthmuses, apical deltas and C-shaped configurations.

Efficacy of xylene and passive ultrasonic irrigation on remaining root filling material during retreatment of anatomically complex teeth.

AIM: To evaluate the volume of remaining filling material in the mesial root canals of mandibular molars after root canal retreatment with different procedures performed sequentially. METHODOLOGY: The mesial root canals of 12 human first mandibular molars were instrumented using the BioRace system until a size 25, .06 taper instrument. The mesial roots were filled with gutta-percha and AH-Plus using a vertical compaction technique. The specimens were scanned using microcomputed tomography with a voxel size of 16.8 µm before and after the retreatment procedures. To remove the filling material, the root canals were enlarged until the size 40, .04 taper instrument. The second step was to irrigate the root canals with xylene in the attempt to clean the root canals with paper points. In the third step, the passive ultrasonic irrigation technique (PUI) was performed using 2.5% sodium hypochlorite. The initial and residual filling material volume (mm(3) ) after each step was evaluated from the 0.5 to 6.5 mm level. The obtained data were expressed in terms of percentage of residual filling material. Statistical analysis was performed using the Friedman test (P < 0.05). RESULTS: All specimens had residual filling materials after all retreatment procedures. Passive ultrasonic irrigation enhanced the elimination of residual filling material in comparison with the mechanical stage at the 0.5-2.5 mm and 4.5-6.5 mm levels (P < 0.05). No significant difference was found between xylene and PUI methods. CONCLUSIONS: Filling materials were not completely removed by any of the retreatment procedures. The use of xylene and PUI after mechanical instrumentation enhanced removal of materials during endodontic retreatment of anatomically complex teeth.

Strain-dependent arthritogenic potential of the zoonotic pathogen Corynebacterium ulcerans.

During the last decade the majority of diphtheria cases in Europe had Corynebacterium ulcerans as the etiologic agent with dogs and cats as the reservoir hosts. However, little has been documented about the virulence factors of this zoonotic pathogen. To set up an in vivo experimental C. ulcerans infection model, conventional Swiss Webster mice were intravenously infected with different doses (from 1 × 10(7) to 5 × 10(9) bacteria per mouse) of C. ulcerans strains, namely 809 (from human lower respiratory tract), BR-AD22 (from asymptomatic dog nares) and CDC-KC279. Mortality rates were demonstrated by LD(50) values ranging from 1.9 × 10(8) to 1.3 × 10(9). Viable bacteria were recovered from blood, kidneys, liver, spleen and joints. For CDC-KC279 and 809 strains (2 × 10(8)mL(-1)) approximately 85% and 72% of animals with articular lesions were observed, respectively; BR-AD22-infected mice showed no signs of arthritis. CDC-KC279 and 809 strains exhibited higher arthritogenic potential when compared to the homologous toxigenic (ATCC27012) and non-toxigenic (ATCC27010) strains of Corynebacterium diphtheriae. A high number of affected joints and arthritis index in addition to the histopathological features, including subcutaneous edema, inflammatory infiltrate, damage to bone tissue and synoviocyte hypertrophy, indicated a strain-dependent ability of C. ulcerans strains to cause severe polyarthritis. A correlation between the arthritis index and systemic levels of IL-6 and TNF-α was observed for C. ulcerans strains, with the exception of the non-arthritogenic BR-AD22 strain. In conclusion, C. ulcerans revealed a strain-dependent arthritogenic potential independent of DNAse, PLD and diphtheria toxin production.

Identification of plasmenylethanolamine as a major component of the phospholipids of strain DM 28c of Trypanosoma cruzi.

A novel phospholipid has been purified from strain Dm 28c of Trypanosoma cruzi, and characterized by fast atom bombardment mass spectrometry and nuclear magnetic resonance spectroscopy as a plasmenylethanolamine with a hexadec-l-enyl group in the sn-1 position and an approximately equimolar mixture of octadecenoate and octadecadienoate esterified to the sn-2 hydroxyl. The purified plasmenylethanolamine reacted positively when probed with sera from patients with chronic Chagas' disease. Since plasmenylethanolamines of similar structure are abundant in mammalian cardiac and neuronal tissues, cross reactions between these epitopes may be a factor in the mechanism of autoimmune pathology in the chronic phase of Chagas' disease.