Karl qualified from Cardiff Dental School in 1981 and owned his own general dental service NHS Practice in South Wales until 1997. Between 1982 and 1997, he was also a member of the Local Dental Committee and part-time lecturer in Cardiff Dental School. Between 1992 and 1997, he completed his specialist training in London and Sheffield, and was appointed Consultant in Restorative Dentistry in Morriston Hospital, Swansea in 1997. Since 1997, Karl has also provided specialist private services from a large NHS general dental service practice in Swansea. Since 1997, Karl is registered with the General Dental Council as a specialist in Restorative Dentistry, Endodontics, Periodontology, and Prosthodontics.
Between 2008 and 2018, Karl was an elected member of the Board of the Faculty of Dental Surgery at the Royal College of Surgeons where he was also Senior Vice Dean and chair of several committees, including Clinical Standards and Post Graduate Education. He was also Chair of the Welsh Dental Committee between 2008 and 2016.
In 2010, Karl was appointed Associate Medical Director for Dentistry in SBUHB and in 2015 the Dental Director. He is one of the Directors for the Primary Care Team Service Group in SBUHB and is Chair of the Welsh Dental Directors Group.