Does losing one of the upper teeth affect the pronunciation of the letter "dhāl" or other letters? And is prayer permissible with this mispronunciation?

The loss of teeth does not necessarily affect the pronunciation of letters. Young children recite the Qur’an after losing their milk teeth, and some elderly individuals lose their teeth without it affecting the articulation points of the letters. We advise you to correct your recitation with one of the reciters who are proficient in Tajweed. Prayer is permissible even with a lisp.