Prefabrication of axial vascularized tissue engineering coral bone by an arteriovenous loop: a better model.

The most important problem for the survival of thick 3-dimensional tissues is the lack of vascularization in the context of bone tissue engineering. In this study, a modified arteriovenous loop (AVL) was developed to prefabricate an axial vascularized tissue engineering coral bone in rabbit, with comparison of the arteriovenous bundle (AVB) model. An arteriovenous fistula between rabbit femoral artery and vein was anastomosed to form an AVL. It was placed in a circular side groove of the coral block. The complex was wrapped with an expanded-polytetrafluoroethylene membrane and implanted beneath inguinal skin. After 2, 4, 6 and 8 weeks, the degree of vascularization was evaluated by India ink perfusion, histological examination, vascular casts, and scanning electron microscopy images of vascular endangium. Newly formed fibrous tissues and vasculature extended over the surfaces and invaded the interspaces of entire coral block. The new blood vessels robustly sprouted from the AVL. Those invaginated cavities in the vascular endangium from scanning electron microscopy indicated vessel's sprouted pores. Above indexes in AVL model are all superior to that in AVB model, indicating that the modified AVL model could more effectively develop vascularization in larger tissue engineering bone.

Modified approach to construct a vascularized coral bone in rabbit using an arteriovenous loop.

The most important factor for the survival of thick three-dimensional tissues is the degree of vascularization. In this study, a modified arteriovenous loop (AVL) model was developed to prefabricate an axial vascularized tissue-engineered coral bone. In group A (n = 28), an arteriovenous fistula between rabbit femoral artery and vein was anastomosed to form an AVL. The AVL was placed in a coral block (6 x 8 x 10 mm (3)) as a vascular carrier. The complex was wrapped with polytetrafluoroethylene membrane and implanted subcutaneously. In group B (n = 20), there was no vascular carrier, and the same dimensional coral was directly implanted beneath inguinal skin. After 2, 4, 6, and 8 weeks, the rabbits were perfused with heparinized saline (for scanning electron microscopy), India ink (for histological examination), and ethylene perchloride (for vascular casts) via the abdominal aorta. In group A, histology showed that newly formed vasculature extended over the surfaces and invaded the entire coral blocks. The vascular density was significantly superior to that in group B. Vascular casts showed that new blood vessels robustly sprouted from the AVL. Scanning electron microscopy demonstrated that there were minute sprouting cavities in the vascular endangium. In this model, an axial vascularized coral bone could be effectively constructed.

Dental implants with the periodontium: a new approach for the restoration of missing teeth.

Tooth loss is a common occurrence in mankind and damages human health. Osseointegrated dental implants have been successfully used as a popular prosthetic restoration for the missing teeth for many years. However, osseointegration, representing a direct connection between the implant and bone tissue without the periodontium, causes some inevitable problems, such as masticatory force concentration and immobility of the dental implant. Thus, an ideal dental implant should have its own peri-implant periodontium, as do the natural teeth. A number of attempts have been made to reconstruct the periodontium around the implants. Unfortunately, it has been established that a predictable periodontal reconstruction, especially the acellular cementum reconstruction on the surface of the implant, is a very difficult task. In this paper, we propose the hypothesis that the cementum may be a special phenotype of the bone tissue, on the basis of its strong similarity in development, structure, and function. In a certain condition, the bone tissue may change to cementum for special functional needs. In accordance with this hypothesis, we consider a novel approach to reconstruct the peri-implant tissues. Unlike previous studies, this approach imitates the tooth re-plantation process. The key point is to convert the implant-surrounding bone tissues to cementum as a result of adaptive changes to the implant-support demands. This hypothesis, if proven to be valid, will not only represent a breakthrough in cementum research, but also will open a new door to the restoration of missing teeth.