The properly contoured interim restoration should be smoothly continuous with what part of the tooth?

A well-contoured interim restoration should be smoothly continuous with the external surface of the tooth. This approach ensures that the restoration mimics the natural anatomy of the tooth, providing a seamless transition between the interim restoration and the natural tooth structure. Supporting the overall aesthetics, this continuity helps maintain natural contours and promotes periodontal health by smoothing out any areas that could potentially trap plaque or food particles. Ensuring a proper fit at the external surface also contributes to the stability of the interim while reducing the chances of irritation to the surrounding tissues.

The internal surface of the tooth would not provide the necessary external aesthetics or functional integrity that is required in an interim restoration. Intracoronal structures pertain more to areas within the confines of the tooth, which would not be relevant for the external contouring required in such restorations. The cement enamel junction, while important for understanding the transition between enamel and cementum, does not directly relate to the contouring of the interim restoration compared to the external surface.