Bio-Root and Implant-Based Restoration as a Tooth Replacement Alternative

Abstract

We previously reported that dental stem cell–mediated bioengineered tooth root (bio-root) regeneration could restore tooth loss in a miniature pig model. As a potential new method for tooth restoration, it is essential to compare this method with the widely used commercial dental implant–based method of tooth restoration. Tooth loss models were created by extracting mandibular incisors from miniature pigs. Allogeneic periodontal ligament stem cells (PDLSCs) and dental pulp stem cells (DPSCs) were isolated and cultured. A PDLSC sheet was prepared by adding 20.0 µg/mL vitamin C to the culture medium; in addition, a hydroxyapatite tricalcium phosphate (HA/TCP)/DPSC graft was fabricated and cultured in a 3-dimensional culture system. A total of 46 bio-root implantations and 9 dental implants were inserted, and crown restorations were performed 6 mo after implantation. Histological, radiological, biomechanical, and elemental analyses were used to evaluate and compare tissue-engineered bio-roots and dental implants to the natural tooth roots. After 6 mo, both computed tomography scans and histological examinations showed that root-like structures and dentin-like tissues had formed. Three months after crown restoration, clinical assessments revealed that tooth function was equivalent in the regenerated bio-root and the dental implant. Biomechanical testing showed that the bio-roots were similar to natural tooth roots in compressive strength, modulus of elasticity, and torsional force; however, these properties were significantly higher in the dental implants. Elemental analysis revealed a higher similarity in elemental composition between bio-roots and natural tooth roots than between bio-roots and dental implants. However, the dental implant success rate was 100% (9 of 9) and the bio-root success rate was only 22% (10 of 46). Taken together, we showed that an allogeneic HA/TCP/DPSC/PDLSC sheet could successfully build a bio-root with structure and function similar to the natural tooth root; however, tissue engineering procedures must be optimized further to improve the success rate.