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298 PATHOLOGY OF THE HAED TISSUES OF THE TEETH.
axio-pulpo-mesial and axio-pulpo-distal point angles are formed in a similar way.
See Note on Compound Words following definition of Angle.
In incisor or cuspid mesial or distal cavities, the first set of line angles will con-
sist of the labio-gingival, linguo-gingival and incisal angles. The second set will be
the axio-labial, axio-gingival and axio-lingual angles. The point angles will be the
axio-labio-gingival, axio-linguo-gingival and the axio-incisal. This latter is usually
called the incisal angle and is regarded as an exception to the rules of naming angles
of cavities.
In incisor or cuspid labial or lingual cavities the first set of line angles will be
the mesio-gingival, disto-gingival, mesio-incisal and disto-incisal. The second set
will be the axio-mesial, axio-distal, axio-gingival and axio-incisal.
The point angles will be the axio-mesio-gingival, axio-disto-gingival, axio-mesio-
incisal, axio-disto-incisal.
Names op cavity margins. Cavity margins take the names of the margins of
the surfaces of the teeth in which they occur; or each cavity margin takes the
name of the cavity wall of which it forms the margin or cavo-surface angle. There-
fore, cavity walls, cavity margins, cavo-surface angles and margins of surfaces of
teeth, take the same names, the difference being only the specification as to which
they belong.
Names op cavo-surface angles op cavities. Each cavo-surface angle of a
cavity takes the name of the cavity wall to which it belongs. See Names of Cavity
Margins.
Names of margins op surfaces of the teeth. These take the names of the
surfaces of the teeth toward which they are placed. In the bicuspids and molars
these are the mesial, buccal, distal and lingual margins of occlusal surfaces; the
mesial, occlusal, distal and gingival margins of buccal and lingual surfaces; the
buccal, occlusal, lingual and gingival margins of mesial and distal surfaces. Id
the incisors and cuspids these are the mesial, incisal, distal and gingival margins of
labial and lingual surfaces. Proximal surfaces of the incisors, because of their
triangular form, have but three margins: the labial, gingival and lingual. The
incisal surface or edge is not supposed to have margins ordinarily requiring names,
but in case of any necessity, especially in eases of considerable abrasion, the margins
would be named on the same plan as the above.
Naming of cavities, rule for. See Rules for Naming Cavities.
Naming of cavity walls, rules for. See Rules for Naming Cavity Walls.
Naysmith 's membrane. A membrane-like glaze covering the enamel of a tooth,
discovered by Naysmith. It may be parted from the enamel by careful digestion in
weak solutions of acids. It is worn away from the parts of the teeth exposed to
friction very early in life.
Neck. That portion of the tooth which forms the junction of the crown and
root.
Necrosis. Local death of a part of a tissue, especially of bone, in a mass.
Necrotic. Pertaining to necrosis or local death of tissue, particularly of bone.
Nerve. "Nerve of a tooth." Once a common name for the dental pulp. Obso-
lete.
Neuritis. Inflammation of a nerve, or of nerves.
Neurosis. A functional disease of the nerves.
Nib. That part of a working end of a plugger point that corresponds to the
blade of an excavator.
Nomenclature. A system of naming things or acts. Each profession or busi-
ness has its own system of naming things or acts pertaining to it.
Nomenclature of cavities. In dentistry, a system of nomenclature applied to
cavities in teeth. Under this term is included all of the names of cavities. Names