Which surface would be furthest from the midline?

The furthest surface from the midline of the dental arch is the distal surface. In dental terminology, the midline refers to an imaginary line that divides the mouth into equal right and left halves. The distal surface of a tooth is the side that is opposite the midline, or the side that is further away from it.

On a single tooth, the mesial surface is located closer to the midline, while the labial surface is the front or facial surface facing the lips. The incisal surface refers to the cutting edge of anterior teeth but is not defined by its proximity to the midline. Therefore, among the options provided, the distal surface is the one that is farthest from the midline, making it the correct answer.