His obituary in The Journal of the Irish Dental Association described him as the most distinguished dentist that Ireland had ever produced.
[3] Friel studied at Trinity College, Dublin, graduating in 1908 and receiving a master's degree in dental science in 1909.
[7] Friel was a pioneer in the use of stainless steel, rather than the previously preferred gold, for the manufacture of orthodontic devices.
[4] Other research interests were muscle testing and training, the relation of function to the size and form of jaws, the migration of teeth and occlusion.
[6] In 1945 Friel undertook a campaign in the profession for the greater specialisation of orthodontics in Britain at a time when much treatment was undertaken by non-specialist dentists.