TOPOGRAPHY OF THE MOUTH AND TOOTH STRUCTURE
Section I. TOPOGRAPHY OF THE MOUTH
The mouth, which is the first subdivision of the digestive system, can be divided
into two parts--the oral vestibule and the oral cavity. The oral vestibule is the space
separating the lips and cheeks from the teeth and gums. The oral cavity is that part of
the mouth which, in front, is bounded by the teeth and which, in back, opens to the
throat. Topography of the mouth refers to the surface configuration of the mouth, that
is, the figure, the contour, or the arrangement pattern of its parts.
The space between the front teeth and the lips forms the anterior part of the oral
vestibule. The posterior part of the oral vestibule can be explored by clenching the
teeth, pulling the lips apart, and pushing the index fingers back along the surface of the
teeth, moving them as far up and down as possible. Figure 3-1 shows a cross-section
of the mouth. One of the principal uses of the mouth is human speech. These
specialized sounds are made by using the lips, the teeth, the bony ridge back of the
upper teeth (the alveolar process), the hard and the soft palate, and the tongue. These
features can be noted in the figure.
a. Mucobuccal Folds. The mucobuccal folds, which form the upper and lower
boundaries of the vestibule, are important in the making of a denture. If the borders
(edges) of a denture are too long in the mucobuccal fold area, the denture will not fit
properly. It will cause inflammation and soreness of the tissues.
b. Labial Frena. Approximately in the midline of the mouth, there are sickle-
shaped folds which connect the alveolar processes with the upper and lower lips and
tend to restrict their movement. These folds may be examined by pulling the upper lip
outward and upward and the lower lip outward and downward. These folds are called
the upper and lower labial frena or frenula (singular--frenum or frenulum). Similar frena
are found posteriorly, connecting the alveolar processes with the cheeks. They also
must be considered in the making of a denture. If an inadequate groove is made in the
denture to accommodate the frenum, then this delicate fold of tissue will not only be
damaged by constant rubbing, but will also place a constant pull on the denture, which
may be strong enough to dislodge it.