Questions & Answers about La dento apud la plombaĵo estas sentema.
Because both dento and plombaĵo are being treated as specific things.
- la dento = the tooth
- la plombaĵo = the filling
Esperanto uses la much like English the. If both the tooth and the filling are known or identifiable in context, it is natural to use la for both.
Apud means next to, beside, or adjacent to.
So la dento apud la plombaĵo means the tooth that is next to the filling.
It is a preposition showing physical closeness. In this sentence, it helps identify which tooth is being talked about.