Craniofacial regeneration  Craniofacial regeneration refers to the biological process by which the skull and face regrow to heal an injury. This page covers birth defects and injuries related to the craniofacial region, the mechanisms behind the regeneration, the medical application of these processes, and the scientific research conducted on this specific regeneration. This regeneration is not to be confused with tooth regeneration. Craniofacial regrowth is broadly related to the mechanisms of general bone healing. Craniofacial regeneration is necessary following injury to the facial tissue. This can occur during surgery, where doctors fracture the face of a patient in order to correct craniofacial abnormalities such as cleft lip, Apert syndrome, Treacher Collins syndrome, Oligodontia, Cherubism, Crouzon syndrome, Pfeiffer Syndrome, Craniosynostosis, or Goldenhar Syndrome. Other applications include corrections to birth defects (such as hypertelorism), maxillofacial surgery, craniosynostosis, rare craniofacial clefts, or removal of tumors. This regeneration can also be necessary following trauma to the face, most often due to automotive accidents. Craniofacial defects are most common congenitally (present at birth), with an estimated prevalence of 1 in 700 live births (270,000 children per year). Common corrective procedures include intracranial surgeries (making room for brain growth through skull expansion), Cleft palate surgeries (repairing a gap in the roof of the mouth), and Cleft lip surgeries (closing a gap in the lips). Most patients who suffer from craniofacial abnormalities have a normal life expectancy, but symptoms are often present throughout the patient's life. Common symptoms and features of a craniofacial defect include abnormal cranial morphology, difficulty in cranio-related functions such as breathing, hearing, swallowing, or speech, or facial paralysis. In the 1970s, mesenchymal stem cells (MSCs) were discovered by A.J. Friedenstein. Mesenchymal stem cell research has yielded the most promising results for craniofacial regeneration, as MSCs can be found in many types of postnatal tissues, including orofacial tissues. Alginate hydrogel, which contains nerve growth factor, has been used to deliver stem cells to tissues during regeneration. While there is a lack of craniofacial-specific clinical trials regarding stem cell therapies, there has been great effort in identifying craniofacial-specific stem cell populations, precursor cells that can give rise to many specific structures of the skull.