Geomorphologic study of human tooth root surfaces following simulated avulsion by scanning electron microscopy

Background/Aims Tooth avulsion is the most severe traumatic tooth injury. Immediate replantation after avulsion provides the highest success rate, whereas delayed replantation with dehydration for >1 h always results in ankylosis, replacement resorption, and eventual tooth loss. The aim of this study was to investigate the geomorphologic change of ultrastructure on tooth root surfaces due to dehydration. Material and Methods Twenty-four sound human premolars and fully developed third molars without periodontitis were selected for the experiment. Roots were separated into 6-7 pieces with an intact root surface area (3 x 3 mm(2)) and then divided into the following groups: fresh group, prolonged dehydration groups (air drying for 1, 2, 4, 12, or 24 h), and dehydrated teeth (air drying for 2 h) treated with acid (Tris-HCl buffer or citric acid buffer). More than six pieces of root from each group were subjected to scanning electron microscopy (SEM) observation. Captured images were exported to ImageJ software to quantitatively analyze the areas covered with fibers. Statistical significance was determined by comparing the means of the different groups using t-testing or one-way analysis of variance followed by post hoc testing. Results Fibrous "vegetation" covering the cementum was observed on the fresh root surface by SEM. This was destroyed by dehydration (>1 h), resulting in a root surface resembling the "Gobi Desert." The difference was statistically significant (p < .001). Root surface deteriorated by dehydration could be recovered by the re-use of the fibers embedded in the cementum as acid demineralization of the outer layer of cementum exposed the embedded fibers to simulate the geomorphology of fresh root surface. Conclusions Dehydrated teeth had deteriorated geomorphology of the root surface, which could be reversed by the re-use of the fibers embedded in the cementum using citric acid. Direct evidence from SEM gives new insights into the replantation of dehydrated avulsed teeth.