Residual dentin thickness in bifurcated maxillary premolars after root canal and dowel space preparation

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.