Stripping perforation is a possible complication in instrumentation of C‐shaped canals. This study evaluated the minimum thickness of the root canal wall in C‐shaped teeth after instrumentation. Twelve extracted C‐shaped mandibular second molars (four teeth of type I, II and III each) were examined by CBCT (voxel size 90 μm) before and after instrumentation with WOG primary file. Micro‐CT scans (voxel size 30 μm) were obtained after instrumentation. Percentage of canal wall area touched by the file and minimum thickness of dentine were measured and compared between CBCT and micro‐CT. In type I C‐shape canals, less than 10% of the canal wall area was touched by the instrument. In ten teeth, the shortest distance to root surface was from the instrumented area; no perforations occurred. CBCT and micro‐CT measurements were in good agreement in ten cases; in two teeth, micro‐CT revealed considerably shorter distance to root surface. The two shortest distances were 0.27 and 0.41 mm.
The aim of this descriptive ex vivo study was to evaluate qualitatively the depth of pit and fissures (P&F) of the enamel in human mandibular third molars. Fifty (n=50) extracted human mandibular third molars were cleaned and disinfected. All tooth surfaces were coated with nail varnish except for a 1-mm margin around the periphery of the occlusal surface. The teeth were immersed for 48 hours at 37 °C in 1% methylene blue dye solution prepared in artificial saliva. After cleaning, the crowns were separated from the root at the cementoenamel junction and subsequently sectioned longitudinally in buccolingual direction at the location of the central fossa. All sections were examined using a stereoscopic microscope and photographed. The images were downloaded on a computer. The length of penetration of the P&F was recorded using the following scoring system: C1: P&F extended to half of the enamel thickness; C2: P&F extended beyond half of the enamel thickness without reaching the dentine-enamel junction; C3: P&F extended to the dentine-enamel junction. For pits, C1, C2 and C3 were observed in 35, 9 and 6 teeth, respectively, while for fissures, C1, C2 and C3 were observed in 15, 18 and 17 teeth, respectively. The P&F detected in the samples extended to the deepest portions of enamel, quite frequently reaching the enamel-dentine junction. Clinicians should recognize that even if pits and fissures are not clinically obvious, they penetrate deep into the enamel and frequently reach the dentine-enamel junction. Effective treatment is recommended to block access to P&F, thus preventing ingress of bacteria.
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