Figure 4-8. Proximal surfaces.
(2) Interproximal space. The interproximal space is a triangular space
between the proximal surfaces of adjacent teeth, from the crown to the root tip. In a
normal situation, part of the interproximal space is filled by the interdental (gingival)
(3) Interproximal embrasure. The part of the interproximal space not
occupied by the interdental papilla is called the interproximal embrasure. It is an open
space between two adjacent teeth which widens outward facially, lingually, occlusally,
and gingivally from the contact area.
(4) Bifurcation. When a tooth has two roots, the root portion is said to be
bifurcated. As a general rule, mandibular molars have two roots. See figure 4-1.
(5) Trifurcation. When a tooth has three roots, the root portion is said to be
trifurcated. Maxillary molars have three roots.
(6) Midline. The midline (or median line) is an imaginary perpendicular line
that passes between the central incisors in each arch. See figure 4-5. Mesial surfaces
turn toward the midline while distal surfaces turn away from the midline.
(7) Long axis. The long axis of a tooth is an imaginary straight line passing
through the crown and root of the tooth where the bulk of the tooth is most
symmetrically arranged. See figure 4-6.