hello attia
as per your description i presume that you are having orthognathic malocllusion that is dearrangement of teeth with underlying cause being both dental and skeletal
hence you were advised for a orthodontic treatment of braces to correct the occlusion by teeth and an
orthognathic surgery to correct bone position after most of the dental correction is done
now you say that you have another problem that is grinding of teeth
habit of grinding teeth is related to following
1.malocclusion (which your
dentist says is not the possible cause
2.stress (persons with
high blood pressure or stress levels have this )
3.gingivitis
to rule out 2 you may acess yourself or get your blood pressure checked out
as for gingivitis ----its most common in persons with malaligned teeth
for that you may visit your dentist and get an examination done and if thats the case you may need to undergo scaling and than maintain proper
oral hygiene by rinsing your mouth with luke warm saline rinses after every diet
if none of the above than you may visit your
psychiatrist as some time teeth grinding is a sign of some underlying pshycological trouble
hope that helps