ABSTRACT
Residual dentin thickness in 25 extracted bifurcated maxillary premolars after canal and Parapost preparation was assessed using acrylic muffle, after embedding in polyester resin and sectioned horizontally. After each procedure, the residual dentin thickness was compared to the original dentin thickness at eight aspects in three root levels. Residual dentin thickness measurements were calculated using photographs and a Digitizer. In the lingual aspect, the original dentin thickness averaged 0.99 mm (coronal slice) and 0.78 mm (middle slice). Dentin removal after dowel preparation was 31%. Three-way ANOVA with repeated measures was used. The difference in residual dentin thickness was highly significant regarding procedure (canal and dowel preparation, p < 0.0001), slice (middle, coronal, p < 0.0001), and the eight aspects (p < 0.0001). This in vitro study emphasizes the minimal dentin width of the buccal root, especially towards the bifurcation. Thus, dowels should be avoided in this root.
Subject(s)
Bicuspid/anatomy & histology , Dental Pulp Cavity/anatomy & histology , Dentin/anatomy & histology , Post and Core Technique , Tooth Root/anatomy & histology , Analysis of Variance , Humans , Maxilla , Odontometry , Post and Core Technique/adverse effects , Root Canal Preparation , Tooth Fractures/etiology , Tooth Root/injuriesABSTRACT
Dentinal tubules of 27 cylindrical bovine root specimens were infected with Enterococcus faecalis. In nine specimens, 5% chlorhexidine was placed in a slow-release device (Activ Point) for 7 days, in another nine irrigation with 10 ml of 0.2% chlorhexidine was used, and the remaining nine served as positive control. Powder dentin samples obtained from within the canal lumina using ISO 025 to 033 burs were examined for the presence of vital bacteria by inoculating brain-heart infusion plates and counting colony forming units. Results were analyzed using analysis of variance and covariance with repeated measures. Heavy bacterial infection was observed at the layer close to the lumen in the control specimens, decreasing rapidly from layer to layer up to the deepest layer tested (400-500 microm), which contained several hundred colony forming units. Viable bacteria in each layer of dentin were significantly reduced with chlorhexidine irrigation solution (p < 0.01) and were completely eliminated with the chlorhexidine slow-release device (p < 0.01).
