Finite element analysis of multi-piece post-crown restoration using different types of adhesives

The multi-piece post-crown technique is more effective in restoring residual root than other restoration techniques. Various types of adhesives have different material properties that affect restoration. Therefore, the choice of adhesive is particularly important for patients. However, the effect of different kinds of adhesives was not too precise by experimental methods when concerning about individual differences of teeth. One tooth root can only be restored with one type of adhesive in experiment. After the mechanical test, this tooth root cannot be restored with other adhesives. With the help of medical imaging technology, reverse engineering and finite element analysis, a molar model can be reconstructed precisely and restored using different types of adhesives. The same occlusal and chewing loads were exerted on the same restored residual root models with different types of adhesives separately. Results of von Mises stress analysis showed that the adhesives with low Young’s modulus can protect the root canal effectively. However, a root canal concentration is apparently produced around the root canal orifice when chewing. Adhesives with large Young’s modulus can buffer the stress concentration of the root canal orifice. However, the root canal tissue may be destroyed because the adhesive is too hard to buffer the load. When restoring a missing tooth by affixing a post-and-crown to a root canal, the root canal’s strength determines the best choice of adhesive, researchers in China report. Zhi-Hui Liu and colleagues at Jilin University modeled the behavior of five different adhesives — zinc phosphate, carboxylic acid zinc, glass ionomer, panavia F, and superbond — under biting and chewing stresses. Using a mathematical technique known as finite element analysis, the researchers determined that elastic adhesives buffer the root canal against biting and chewing. Over time, however, these adhesives show greater deformation over time, ultimately placing stress on the root canal orifice. Stiffer adhesives transfer most of the load to the root canal, protecting the root canal orifice. Liu thus recommends elastic adhesives for patients with thin root canals, and stiffer adhesives for patients with thicker root canals.