Fractal Analysis to Detect Surface Roughness Changes After Fatique Loading in the Canine Mandibular Incisor - A Pilot Study

Abstract

A common occurrence resulting from orthodontic treatment is iatrogenic root resorption. Experimentally, histological sections are usually employed to study root resorption utilizing special staining techniques. Although this has been shown effective for decades, results are limited to extracted teeth. Clinically, root resorption is detected and evaluated with standard radiography. This technique is limited to evaluating the 3-dimensional phenomenon of root resorption with 2-dimensional films. Quantifying these results has proven to be cumbersome if not impossible. Recent advances in computed tomography are allowing researchers to evaluate changes in the skeleton, including dental movements in three dimensions. CT reconstructions could be used to evaluate the changes in tooth composition through the volumetric data obtained. Fractal analysis techniques have become irreplaceable in the understanding of many phenomena in various scientific fields such as astrophysics, economy, geology, ecology and agriculture. Recently, a significant amount of literature has been published describing the expansion of this technique into the fields of bio-medicine, including dentistry. The logic behind fractals is derived by observing an object through successive scales. Fractal analysis can be used to measure an object's space filling properties. Simply put, the more space the object occupies, the higher the fractal dimension. The purpose of this study is to utilize fractal analysis to quantify morphological changes in ex vivo root structure from fatigue loaded mandibular central incisors of canine (hound) specimens. After fatigue loading experimental teeth, microcomputed tomography, was used to obtain 3-dimensional data of both the experimental and control teeth. Computer software was used to develop 3-dimensional models of each specimen and fractal analysis was performed on specific regions of each tooth. To obtain the specific regions, the root was divided into 5 planes or slices horizontally, beginning with the most cervical portion to the apical portion, then further divided into a buccal and lingual portion. These can be systematically evaluated using a coordinate system of numbering from 1-10, starting with the cervical-buccal region of the root (zone 1) to apical-buccal (zone 5). The numbering then follows to the opposite side of the tooth with the cervical-lingual region (zone 10). Changes in surface roughness were detected through the fractal analysis and compared between the control and experimental animals. Statistical analysis showed that the mean roughness of the experimental group was significantly smaller than in the control group for two of the ten zones tested in each tooth.