Apposition: The word "apposition" has several senses including the act of adding or accretion and also the putting of things in juxtaposition, or side by side.
Growth by apposition is a mode of growth that is characteristic of many tissues in the body by which nutritive matter from the blood is transformed on the surface of an organ into solid unorganized substance.
To lose a pair of apposed teeth is to lose teeth that are next to one another, teeth that are juxtaposed. (The prefix "juxta-" comes from the Latin preposition meaning near, nearby, close). Apposition is thus synonymous in this sense with juxtaposition.