Page 24 - GP Fall Final 2017

Indirectly Precise: The Use of Non-Rotary

Instrumentation for Margin Refinement

By Arthur R. Volker, DDS, MSEd, FAGD and Jennifer Flores, DDS

Sunday, October 15, 2017
Lecture: Modern Composite Techniques for the Anterior
Please register at www.nysagd.org

Introduction inserts available for many applications, teeth without trauma to the gingival tissue,
With improvements in dental materials and including, but not limited to, endodontic , thereby limiting iatrogenic hemorrhage.
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the advent of CAD/CAM dentistry, clini- periodontal, operative and surgical thera- Also, if the insert touches a retraction cord,
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cians are seeking ways to improve the preci- pies. There are three types of non-rotary
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sion of their outcomes. This includes look- instruments: sonic, ultrasonic- magnetore- it will not pull it out of the sulcus, as can
ing for ways to improve the ability to prepare strictive, and ultrasonic-piezoelectric. be observed with a rotary bur. The tech-
and impress for indirect restorations. nique described below was introduced by
Sonic instruments oscillate in an elliptical Massironi and has been used by clinicians
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There are several issues that can result from motion at a frequency of 3000 to 8000 Hz, worldwide, particularly in Europe and
poor tooth preparation. In trying to prepare while ultrasonic-magnetorestrictive instru- Asia. Other benefits include improved ce-
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a chamfer, a J-shaped margin can result ei- ments follow a similar projection, tough at ment distribution between restoration and
ther from improper angulation of the bur a rate of 20,000 to 40,000 Hz. Piezoelec- preparation as well as less microleakage
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or if the full width of the bur is used. This trics move in a linear motion at a rate of of resin cement at the cervical area and on
inadequate margin has a sharp, unsupport- 30,000 to 50,000 Hz. The ultrasonics are dentin as compared to those areas prepared
ed enamel lip that can potentially cause a stand-alone units that run on AC current, with rotary burs. 10,11
marginal discrepancy in several ways. If an while the sonic instrument is attached to
impression were to be poured in stone, the the dental unit via a 4- or 5-hole coupler, Technique
thin margin may fracture upon separation and air-driven by the unit’s rheostat. Vari- The initial preparation is made equigingi-
from the impression, resulting in a false ous pros and cons of the sonic instruments val with rotary diamond burs. Next, a small
negative on the model and, subsequently, are listed in Table 1. diameter retraction cord is placed into the
a short margin. Additionally, if the resto- sulcus at the margin and trimmed so that
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ration is to be milled, it may be difficult for no excess cord is present outside the sulcus
the CAM unit to mill a thin, sharp margin. (Figure 1). A non-rotary instrument with a
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Finally, the enamel margin itself is prone • Minimally invasive • Cost diamond rounded cylinder of an appropri-
to fracture and could do so during impres- • Control • Noise ately shaped insert is then used to reposition
• Fiber-optic light for
sioning, provisionalization or cementation. enhanced visibility • Surface roughness the margin to the level of the cord. (Figure
There can also be bleeding from unwanted • No magneto-electric field 2). Figure 3 demonstrates the appropriate
• Minimizes iatrogenic damage
contact with the rotating bur and gingival • Minimizes gingival trauma orientation of the diamond insert on a model.
• Smaller footprint
tissue which can directly impact the quality
and accuracy of the final impression. Table 1 For further refinement, an enamel hatchet
Utilizing non-rotary instrumentation for in- can be used to plane the margin, as demon-
Though most commonly used for peri- direct restorations provides several advan- strated on a model in figure 4. Finally, a
odontal treatment, non-rotary instrumen- tages. One such advantage is that the os- second, larger cord is used to displace the
tation has multiple applications. There are cillating motion of the inserts can prepare gingival tissue laterally. After 8-10 minutes,
the larger cord is removed, and a tradition-

Figure 1. Retraction cord Figure 2. Non-rotary sonic instrument Figure 3. Demonstration of proper Figure 4. Demonstration of angle
placed within sulcus exposing preparing margin to the level of the angulation of sonic tip during preparation. of enamel hatchet to further refine
equigingival margins. retraction cord. preparation.

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