*5.1.3.1. Bone repair*

In this context, inorganic reinforcements play the most important role, because the natural bone is formed up to 70 wt. % by calcium phosphate very similar to hydroxyapatite (HA) [88]. HA is an inorganic compound, which helps the differentiation of osteoblasts in regeneration of the bone structure [89]. For this reason, incorporation of HA into PLA matrices has been widely reported [90, 91, 92, 93].

Tricalcium phosphate (β‐TCP) has been also widely used due its bioactivity and biodegrada‐ bility. Its degradation rate is incremented 3–12 times compared with HA [94] and this favors bonding of bone to the bioceremic [95]. However, combination of β‐TCP and HA in denomi‐ nated biphasic calcium phosphates (BCP) shows the advantages of both components: reactivity of β‐TCP and stability of HA. BCP with 60–40% of HA‐TCP incubed in simulated body fluid produces the precipitation of needle‐shaped apatite crystals [96], allowing polylactide/BCP composites for fracture fixation plates [97].

Furthermore, discovery of bioactive glasses by L. L. Hench in 1969 catapults the use of these inorganic particles in tissue engineering due to their excellent biocompatibility and the ability of bone bonding [98]. A common characteristic of bioactive glasses and ceramics is a time‐ dependent kinetic modification of the surface that occurs upon implantation [99]. Bioactive glasses originate a superficial layer of calcium deficient carbonate, which permits a chemical adhesion to bone. This adhesion is appealed as bioactivity and is associated with the formation of carbonated hydrocyapatite (HCA) when glass is implanted or in contact with simulated body fluids [100, 101]. The HCA layers formed on a scaffold made of 45S5Bioglass® immersed in SBF takes a "cauliflower" typical morphology [99] and allows osteogenic formation [102].

Some researches of PLA/bioactive glass composites have been reported [103, 104]. However, melt processing of bioglass with polylactides affects the thermal stability of the composite [105], and to overcome this handicap, protection of bioactive ceramic with and acrylic plasma treatment has been proposed [106]. An easier treatment than plasma has been proposed by A. Larrañaga by covering these particles with a mussel inspired polydopamine coating, which results in a bioactive composite [107].
