Editorial: The expanding Frontiers of stem cells therapy in oral maxillo-facial engineering and regenerative medicine - Christiane L. Salgado; Christiane L. Salgado; Andrea Cochis; Elena M. Varoni; Rui Amaral Mendes; Rui Amaral Mendes; Rui Amaral Mendes; Rui Amaral Mendes (Frontiers in Bioengineering and Biotechnology)