My bottom teeth are aligned but there is now a 2-3 ml space between 2 teeth at the top of the tooth root. bonding? nothing loose yet. annoying.

Recession: If you have or have had periodontal issues and you have loss of bone height, this often occurs. Bonding can close the space, but remember: 1) teeth will look wider than the rest 2) bonding will discolor 3) bonding may flake off easily 4) it may be harder to keep the area clean. Give it a try to see if it suits your needs... it can always be removed.

Unsure: I believe that you are saying that while two of your lower teeth touch normally at the biting edge, there is a space at the gum line. This might be due to recession of the papilla or triangle of gum tissue that normally fills that space. That would be common at your age. There are other conditions that might cause the roots of your teeth to move apart which would need attention. See your DDS.

Black triangle: Signifies bone loss. Can be camouflaged by bonding teeth to partially fill the space. This, however, does not address your bone/gum loss, and size of black triangle may continue to enlarge. It may be prudent for you to see a gum/bone specialist, a Periodontist, to halt recession prior to tooth recontouring.