Hello, it could be because of deposits on teeth surface or food lodged in between teeth. Visit a dentist and get your scaling and polishing done. Brush your teeth twice daily, night brushing is very important. Floss regularly. Rinse after every meal. Visit dentist every 6 months.

Even after doing scaling ,the yellow stain still persist then it may be either due to flurosis ya history of trauma to that particular  tooth.first rule out the cause and do the proper treatment according to it.if it is due to flurosis then u can do veneers ya ceramic crowns .and if it is due to trauma u need to take an x-ray and do rct followed by a ceramic crown.

Hello Sir. If the yellowish color still remains after scaling then it is probably due to stains within the tooth. The reason may be due to fluorosis or due to trauma. For yellowness due to fluorosis, it can be corrected by covering that tooth with veneers or full crowns. For yellowness due to trauma, get a x-ray done and get a root canal treatment done followed by a crown.

As you are saying that you have gone through Scaling from AIIMS, still yellowish mark is there. Because dentists at AIIMS have examined you clinically, they must have told, reason behind yellowish mark, which is still persisting even after Scaling. I guess it must be fluorosis ( due to presence of extra flouride in water ), or it might be due to trauma. There are several ways to get FLUOROSIS corrected :- First one is VENEER ( Tooth facial surface is trimmed about 1 mm and then a thin facial prosthesis called veneer is pasted with the help of resin cement ). Veneer can be of your desired shade/color. Second one is CROWN/CAP ( In this complete tooth structure is reduced in size about 1-1.5 mm from all sides and then a tooth shaped prosthesis is fitted on your trimmed tooth structure ) For yellowness due to TRAUMA :- First tooth is ROOT CANAL TREATED ( Its dead pulp tissues are removed from inside pulp chamber and root canals. After that it is filled with Gutta Percha , a type of material to fill empty and cleaned root canals. After that CROWN/CAP is done on the tooth which I have described earlier. In some cases you might have to go Extraction/ Removal of Tooth and get replaced with new tooth.

If the yellowish color still remains after scaling then it is probably due to stains within the tooth. This can be corrected only by covering that tooth with veneers or full crowns.