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Interproximal contacts are developed when the restoration is bigger in the mesio-distal dimension than the space into which it is placed. If the restoration is too small, the contact will be open or not give resistance to the passage of floss. If it is too large, the restoration will not fit during try-in. The goal is to achieve interproximal contacts that are correct in strength as well as location.
When a crown is placed on a natural tooth, the tooth and its neighbors all shift slightly to accommodate placement of the oversized restoration. The adjacent teeth are slightly displaced and the tooth with the restoration self-centers in the space. Because of the movement of the prepared tooth, it is possible to achieve success with a contact that is slightly heavier on one side or the other. The pressure evens out very quickly. Unfortunately, this is not the case with crowns placed on implant abutments.