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Impact of Endodontic Treatments on the Rigidity of the Root

Department of Restorative and Preventive Dentistry, Westdeutsche Kieferklinik, University of Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany

View larger version (31K): [in a new window]   Figure 1. Experimental design. Schematic drawing showing the course of treatment and measurement of deformation.

View larger version (53K): [in a new window]   Figure 2. Loading of the teeth. The teeth were fixed at the apex of the root and 2 mm below the cementum-enamel border (right). The measurement of the deformation was standardized by means of a force-controlled piezoelectric device and a wedge-shaped slide ram tilted by 135° with respect to the tooth axis (upper left).

View larger version (11K): [in a new window]   Figure 3. Deformation of the teeth. Box plots show the results of the measurement after loading with 3.75 N. The Fig. depicts mean values ± SD of the deformation (µm, z-axis) of 20 teeth following different treatments. Significant differences of mean values are marked by an asterisk (*). Gr. 1, untreated teeth; gr. 2, access preparation; gr. 3, manual instrumentation ISO 40; gr. 4, ISO 60; gr. 5, ISO 80; gr. 6, ISO 110; gr. 7, tapered post preparation; and gr. 8, parallel-sided post preparation.

View larger version (35K): [in a new window]   Figure 4. Tooth after instrumentation (ISO 110) and after parallel-sided post preparation. Top: Distortion of a tooth after instrumentation (ISO 110) under load of 3.75 N (gr. 1). The tooth or the root, respectively, is distorted. Bottom: Distortion of a tooth with parallel-sided post preparation under load of 3.75 N (gr. 8). The tooth clearly shows a greater distortion. The loss of hard substance, caused by the post preparation and the modified root canal geometry (tapered to parallel-sided), resulted in a distinct increase of deformability of the tooth’s root, respectively (upper panel, quantitative presentation in out-of-plane plot; lower panel, distortion of the tooth in the plane of section [see red line in the plot]).