People can be younger dentally than they are chronologically.
What do I mean by that? Dentally, a “young person” has all of their teeth (not counting wisdom teeth) and a good foundation under them. Sure, they can have fillings and the teeth may not be in movie star alignment, but having a complete arch of teeth is the mark of “youthfulness.” An arch of teeth is the same as the arch an architect uses, take one stone (tooth) out and you do serious damage. The strength and stability of the whole group is compromised, and in the mouth these problems become worse with time because of the increasing tipping and mal-alignment of the remaining teeth if no replacements are provided. Further, in the mouth, the underlying bone where the roots had been erodes away giving a sunken in look to that area of the face.
This is why a conscientious dentist does not take lightly the pulling of a tooth. Yes, it is certainly cheaper to pull a tooth than it is to rebuild a tooth when major repairs are required; but the consequences to the entire system of tooth removal are often overlooked in the short-sited effort to save money. Tipped teeth start to become looser because they weren’t meant to chewed on at an angle. Jaw joints and muscles may begin to suffer or become painful by trying to accommodate an unnatural chewing pattern. New decay and gum disease can start in areas that become difficult to maintain. By the time all this becomes apparent a youthful mouth has become aged and it is often too late to fix.
A primary goal for a youthful smile is to keep all our natural teeth, but when a tooth is damaged beyond predictable repair, its replacement should be accomplished as soon as the site has sufficiently healed. We would do no less for a stone archway because we know ignoring the loss will turn a building into a “ruin.”