Pacific Coast Society of Orthodontists Bulletin Fall 2020 - 50

Let's Talk About That

Figure 14. Correcting a deep overbite using continuous archwires with brackets sited at FA points
Siting brackets at the FA points is much like
placing them at the earth's equator. Siting them
more occlusally or gingivally is akin to placing
them in the northern or southern hemisphere of
the earth, which adversely affects the orientation
of the slots relative to the planes of the crowns
and distorts the expression of prescription values,
particularly prominence and inclination. For
example, the relative facial prominence of a maxillary canine compared with a neighboring lateral
incisor is different if measured at the level of the
FA points than if measured in the gingival third or
occlusal third of the crown's facial surfaces.
Siting brackets at predetermined fixed heights
from incisal edges or cusp tips is contraindicated
because of the likelihood of missing the " equator. " Some recommend varying the heights of
incisor bracket positions based on the presence
of a deep overbite or anterior open bite. Such a
tactic might create a biomechanical advantage
during the initial few months of leveling but will
thereafter be a handicap. Instead, we recommend
always siting brackets at the FA points, no matter
the malocclusion, and letting the archwire solve

such problems using reverse or accentuated
curves of Spee as needed (Figure 14).
PT: Smile arc is a hot topic. Do you consider it an
essential component of smile attractiveness? If
so, do you alter incisor bracket heights to modify
the smile arc?
WA: There are studies that support the idea that
a gentle upward curvature to the smile arc following the curvature of the lower lip is a desirable
characteristic.17-19 In our experience, however, it
does not seem to be a universal attribute of an
attractive smile. There are many examples of
attractive smiles that do not follow the rules of
the classic smile arc (Figure 15).
That being said, if a classic mild smile arc is indeed a goal, it is not so simple to create by merely
siting incisor and canine brackets at varying
heights to differentially extrude or intrude those
teeth so that their edges follow the contour of
the lower lip when smiling. As we see it, the four
primary factors that influence the smile arc are (1)
the lips themselves (over which we have little in-

Figure 15. (a) Classic smile arc and (b) flat smile arc; both are attractive

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PCSO Bulletin    Fall 2020



Pacific Coast Society of Orthodontists Bulletin Fall 2020

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