My Dad Is Deaf And Mute From Birth.My Grand Parents

My Dad is deaf and mute from birth.My grand parents got to know about his illness at his age of 3 yrs and took him to a doctor in madras.He confirmed his illness and said that here is no operation available at that time for curing my dad's treatment.My dad joined in a school for deaf and dumb students where they were not taught by sign languages but by hearing aids.My dad stopped using hearing aids from 25 yrs.Now he is 49.Even now he can't hear.He have voice i.e, we can hear his voice but only sounds are produced not any language form.he can say few words.
Can he be cured.Is there any treatment available now for his age?