What do you call the junction of three internal walls in a cavity preparation?

The correct term for the junction of three internal walls in a cavity preparation is known as a point angle. In dental terminology, a point angle specifically refers to the point where three surfaces converge within the cavity preparation. Understanding point angles is essential for dental professionals as it helps in the precise shaping of the cavity to ensure optimal restoration placement and retention.

The other terms mentioned refer to different concepts within dental anatomy. A line angle refers to the junction of two walls in a cavity preparation, not three. The proximal surface describes the surfaces of teeth that are adjacent to one another, typically referring to the sides of the tooth that are in contact with neighboring teeth. The cavo surface margin is the area where the wall of a cavity preparation meets the external surface of the tooth structure. This term focuses on the seal and interface between the restorative material and the tooth surface, rather than the angles formed internally within the cavity.