Axial Inclination

Axial inclination compares the vertical alignment of the upper teeth, visible from the front view, to the central vertical midline. From the central to the canine there should be a natural, progressive increase in the forward inclination of each subsequent front tooth.

The evaluation of axial inclination can be done on a photograph of the front teeth in a frontal view (as below). Sketch a line from the middle of the incisal edge or cusp tip through the highest point of the tooth on the gum side (zenith). These lines should slant forward while progressing backward tooth by tooth. This is because the zenith is positioned further back as the teeth progress backward in the arch.

The perceived inclination of these lines can be influenced by recession as the recession may alter the zenith of the tooth in the gum. Ideally, the zenith refers to the height of the enamel of the tooth (which is what the gums ideally follow), so in cases of recession, use the enamel height as the landmark for the axial inclination line.