**4.7 Periodontal**

 Periodontitis is a chronic inflammatory condition resulting in total destruction of the periodontium consists of alveolar bone, cementum, gingiva and periodontal ligaments and if left untreated, can result in tooth loss [73, 74]. Periodontal ligament stem cells (PDLSCs) have been shown to support the regeneration of periodontal tissues [75]. Ma et al. investigated cell viability of extruded PDLSCs encapsulated in a GelMA/PEG hydrogel [76]. It was shown that cell viabilities were around 94% after 24 hours post printing. Extrusion printing has also been used to reconstruct the maxillary bone in a 12-year-old dog, and is believed to be the first case of maxillary bone reconstruction using a 3D printed scaffold [77].
