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CUTTING INSTRUMENTS 6l

(d) Drill.—An engine instrument used for boring or
drilling holes in tooth structure (as in opening into a pulp
chamber from the surface, where no cavity exists) or in bone

(as during the treatment of an alveolar abscess). A drill is
also valuable for following out fissures and for removal of old
fillings. The Spear-point (Fig. 65), Square (Fig. 66) and

Twist (Fig. 67) drills are familiar forms. A special form,
known as a Diamond drill, is valuable for driUing cavities in
artificial teeth. Drills may be readily made from old fissure
and inverted cone burs by beveling them on opposite sides.

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Fig. 65.—Spear-point Fig. 66.—Square Fig. 67.—Twist drills.
drills. drills.

A bi-beveled dentate fissure bur, made from an old dentate
bur, is valuable for driUing through enamel and dentin.
(e) Reamer.—An engine instrument for enlarging root

canals during treatment. Drills should never be used for this
purpose, on account of the danger of perforation. A flexible
reamer, which will follow the route of the canal and enlarge
it, is usually indicated. Well-known varieties are the
Beutelrock and Gates-Glidden reamers (Fig. 68). The Peeso

and Ottolengui root reamers (non-flexible) are used for great
enlargement during the placing of dowels. The Kerr tapered
canal reamers (spiral form) (Fig. 69) are valuable for enlarging
the entrance to canals.
(f) Lancet.—Synonyms, Scalpel, Bistoury. An instru-

ment of knife form, designed for cutting the soft tissues.