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Figure 3: Note the pleasing symmetry
of the central incisors, canines
and posterior teeth when they all
are on the same plane.
Figure 4: The classic reverse smile
line caused by the central incisors
being apical to the plane of the
posterior teeth.
In a normal Class I occlusion, the incisal edge of the central incisor will be on approximately the same
plane as the tips of the canines and the buccal cusp tips of the premolars and molars. When this arrangement
exists, the maxillary central incisal edge position is esthetically pleasing, and the smile line
exhibits symmetry with the lower lip (Fig. 3). 9
When the maxillary central incisal edge is coronal to the plane of the posterior
teeth, it is caused most commonly by overeruption of the teeth as a result of
Class II malocclusion or of restorative dentistry completed without consideration
of edge position. The teeth appear too prominent in the face, and the smile line
exhibits an exaggerated curvature. Bringing the edges apically to the plane level
with the posterior teeth is an excellent starting point when correcting front teeth
that appear too long. After the anterior teeth are placed on the same plane as the
posterior teeth, either through orthodontics or provisional restorations, the practitioner
then can refine the position for the most pleasing appearance. 7,8
When the maxillary central incisal edge is apical to the plane of the posterior
teeth, it creates a reverse smile line (Fig. 4). Common causes of this are undereruption
resulting from a Class III malocclusion, ankylosis caused by trauma or a
patient’s habit (such as tongue thrusting and thumb sucking). Perhaps the most
common cause of this tooth position, however, is wear of the anterior teeth resulting
from a protrusive bruxing habit or chemical erosion while the posterior teeth
sustain minimal wear.
Placing the maxillary central incisor’s incisal edge visually on the plane of the posterior
teeth, either orthodontically or restoratively, will resolve most of the esthetic
problems and create a position from which the dentist then can make refinements.
Although this is a useful method of starting to position central incisal edges, it cannot
always be used. When posterior teeth are missing, worn away, overerupted or
improperly restored, one must use the first and third considerations alone.
Phonetics. The third consideration in appropriately positioning the maxillary
incisal edge is phonetics, specifically the “f” and “v” sounds, as described
in classic prosthodontic texts. 9-11 Most technique discussions men-
“Given the importance
of esthetic success
in practice today,
and the fact that every
facet of treatment
is affected when a
dentist decides to
change a patient’s
incisal edge position,
it is critical that
dentists learn, become
comfortable
with and use these
techniques when
evaluating patients.”
Too Much Tooth, Not Enough Tooth: Making Decisions About Anterior Tooth Position21