What are the reasons of mouth breathing?

Dr. A.K. Sharma did his M.B.B.S course from the S.M.S.Medical college - Jaipur in 1977 ( 40 years ago). He did his M.D (Pediatrics) from the same medical college and after working in prestigious hospitals of Delhi and working for 3 years abroad, returned back and started Jyoti Nursing home in the east Jyoti Nagar - Delhi 110093 on February 3, 1987, along with his wife, Dr. Geeta Sharma. He started a number of social activities and was awarded by the Delhi government for promoting the blood donations. He started a number of academic activities in the east Delhi & Delhi and also involved in the national academic programs. His special areas of interest are - respiratory diseases and the rationale use of antibiotics. He has been rendering services at the K.D. Medicare centre, along with Dr. Geeta Sharma (M.D.), who specializes in the infertility and hormonal problems of the adolescents and ladies.