“…According to the results of the present study all the dentists approved that dental chair and instruments play major role in adopting ergonomics' principles, this disagrees with El-Sallamy et al; 2017 who revealed that only 56.4% thought that dental chair and instruments play a role in adopting ergonomics during dental work (17) . More than half of the studied sample (67.5%) knew the ideal sitting angle, while 72.5% didn't know the depth of chair, 65% didn't know the ideal sitting posture, more than half (60%) of the interns didn't know the ideal position of the patient, and 82.5% didn't know the ideal distance between the dentist and the instruments, these results disagree with Barlean et al; 2012 and Madaan and Chaudhari; 2012, who revealed that half of the dentists had fair knowledge (20,21) , this could be attributed to lack of ergonomics principles in our curricula.…”