Dentaltown November 2017 - 114

continuing
education
orientation,5 while transverse orientation is
used primarily for supragingival debridement
and to access contact points or deposit
coronal to the CEJ (Figs. 3a-c).

Ultrasonic instrument
cross sections

Examples of ultrasonic
instrument orientation

Cross section
Another USI characteristic that needs to
be examined closely is the appearance of the
active tip in cross section. USIs are typically
designed as either circular/cylindrical or
rectangular/square (Figs. 4a-b). The rounded
corners are the areas where the two edges
meet and these offer a more concentrated
area of energy that should be considered
when the demand to remove hard deposit
beyond light levels exists.
USIs with round cross sections have been
shown to preserve more root structure;15,16
therefore, when the focus of debridement
is on biofilm or light calculus and the USI
active tip may be in contact with cementum
or dentin, choosing USIs with a slim diameter
and a round cross section has advantages.

Shape
Lastly, and perhaps one of the most
important considerations of contemporary
ultrasonic implementation, is instrument
shape, also referred to as tip geometry. An
ultrasonic instrument may be straight or
curved (semispiral). When comparing the
active tip area of straight and curved USIs,
it is vital to distinguish that a straight USI
has a straight active tip, while a curved
USI has an active tip with a curve or an
arc (Figs. 5a-c).
When a debridement case does not
present with moderate-to-heavy calculus
(or any level of hard deposit), or when the
moderate-heavy calculus removal phase has
been completed and only light calculus and
biofilm remain, a greater degree of contact is
needed between the USI active tip and the
tooth/root surface.17 Furthermore, it is in the
best interest of the reduction or elimination
of inflammation for clinicians to go beyond
visualizing the active tip merely contacting
the tooth/root surface; to maximize biofilm
removal and disruption, the clinician needs
to visualize and command the active tip to
conform to the surface being instrumented.

114

NOVEMBER 2017 // dentaltown.com

Fig. 3a: Vertical orientation
with a curved instrument.

Fig. 4a: Round/cylindrical cross
section with no rounded corners.

Fig. 3b: Transverse orientation
with a curved instrument.

Fig. 4b: Square/rectangular cross
section with rounded corners.

Fig. 3c: Transverse orientation
with a straight instrument.

Figs. 5a-c: A comparison of ultrasonic instrument active tip areas. Note the convex
surface of the curved instrument defined by the purple circle in Fig. 5c.

Fig. 5a

Fig. 5b

The arc on a curved USI is on the back
surface of the instrument, and it should be
noted that the lateral surface of a USI may
not be the surface that best conforms to
the anatomy of the site being debrided. In
other words, the lateral surface of a curved
or straight USI active tip may not have the
same advantage as the back surface of a
curved USI.
Currently, not all manufacturers of
ultrasonic equipment recommend the use of
the face, back and lateral surfaces of USIs.
Historically, magnetostrictive technology

Fig. 5c

such as Cavitron has offered clinicians the
option of using all surfaces, while piezoelectric technology is more known for advising
clinicians to specifically adapt only the lateral
surfaces to maximize it. Clinicians would be
wise to check the directions for use provided
by the manufacturer of the equipment they
are using. If a manufacturer instructs not
to adapt the back surface of a USI during
the treatment procedure, the clinician
should contemplate the limited debridement
possibilities of that specific technology or
product, and perform technique accordingly.
http://www.dentaltown.com
Table of Contents for the Digital Edition of Dentaltown November 2017
