**Composite Calcium Phosphate/Titania Scaffolds in Bone Tissue Engineering**

Massimiliano Dapporto, Anna Tampieri and Simone Sprio

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.68867

#### **Abstract**

Titanium and its alloys have been extensively used as implantation materials due to their favorable properties such as lower modulus, good tensile strength, excellent biocompatibility, and enhanced corrosion resistance. However, their intrinsic bioinertness generally prevents a direct bond with the bone on the surface especially at an early stage of implantation. In recent years, bioactive scaffolds for bone regeneration are progressively replacing bioinert prostheses in orthopedic, maxillofacial, and neurosurgery fields. Given the need of enhanced mechanical strength, several combinations of bioactive and reinforcing phases have been studied, but still no convincing solutions have been found so far. In this context, titanium oxides are light and high-resistance bioactive materials widely employed in dental and bone application due to their capacity of forming strong bonds with bone tissue via the formation of a tightly bound apatite layer on their surface. The addition of titania particles to hydroxyapatite has attracted considerable attention based on the assumption that resulting materials can enhance osteoblast adhesion and promote cell growth while also providing high strength and fracture toughness in the final composite material, thus being adequate for load-bearing applications.

**Keywords:** hydroxyapatite, titania, bioactive composites, porous scaffolds, mechanical strength, load bearing

## **1. Introduction**

The regeneration of critical-size bone defects, particularly in load-bearing site, still represents a remarkable challenge in orthopedics. Indeed, these clinical cases require the use of scaffolds with cell-instructive ability and remarkable strength to cope with the early and complex

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biomechanical stimuli in vivo [1]. As the use of autografts or allografts suffers many restrictions and drawbacks, particularly in the case of large defects, synthetic biomaterials are today considered as elective in this respect; however, there is still a lack of suitable materials associating bioactivity and high strength. Natural bone is a hybrid nanocomposite capable of outstanding mechanical performance and ability to establish an active dialogue with cells. In particular, the bone is composed of an inorganic compound (60%), a nearly amorphous calcium phosphate with the crystal structure of hydroxyapatite (HA), heterogeneously nucleated on an organic component prevalently made of type I collagen. The collagen phase provides the bone with great flexural strength, while the mineral component increases the bone compression strength.

The unique factors that contribute to the toughness of bone are the presence of nano-size apatite crystals and a dense network of collagen fibers.

For that reason, in the last decades, the research on biomaterials and scaffolds able to favor bone tissue regeneration upon implantation, while also mechanically supporting the anatomic site affected by lack of bone, has been increasing. In this respect elective materials are calcium phosphates, due to their high chemical similarity with the bone mineral. However, they suffer of low mechanical strength that makes them not suitable to be implanted in loadbearing site. Therefore, a new approach was focused on the development of ceramic composites associating high bioactivity and strength.

The present chapter will provide an overview to illustrate novel potential approaches to develop reinforced bioactive scaffolds to assist the regeneration of load-bearing bony sites, considering that serious drawbacks can arise in case of mechanical mismatching at the bone/ biomaterial interface. In particular, the chapter will highlight the use of titanium dioxide, which is a well-established biomaterial for bone applications, as a promising nanomaterial with the ability to reinforce calcium phosphate matrixes.
