Allan Deutsch
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 OSTS
are not generally considered an esthetic part of restorative dentistry,
merely the foundation for what the dentist hopes will be esthetically pleasing.
However, there are times when roots are thin and the metal of a post may
show through the exposed root or even the thin gingival layer over the
root, making for less-than-ideal esthetics. In the same fashion, many of
the restorations built on endodontic posts are ceramics that allow light
and the metallic color of the posts to show through.
Flexi-Flow & Ti-Core
Recognizing the need to improve these situations, Essential Dental Systems,
Inc., developed tooth-colored, long-term (>10 years), fluoride-releasing
composite cements and core materials: Flexi-Flow Natural and Ti-Core Natural
(Figures 1 and 2). Together with an opaquing layer, such as C&B-Metabond
(Parkell), these products mask the color of the metal post (Figure 3) and
improve its esthetics (Figure 4). In addition, Ti-Core and Flexi-Flow also
come in gray (reinforced with titanium) to differentiate from the lighter
tooth structure when necessary.
Stability
One might ask, “Why bother with metal posts that require masking when
a new generation of ceramic posts has been introduced that are tooth-colored
to start with and do not need masking?” The answer is that the first
and most important function of the post is not esthetics, but supporting
the restoration with the greatest long-term stability.
Stability is based on the degree of retention and
the even distribution of insertional and functional stresses. The most
efficient way to gain higher retention is to engage the dentin via a threaded
shank. However, conventional solid-threaded shanks, whether tapered or
parallel, create stresses that could lead to fracture.
Flexi-Post & Flexi-Flange
Flexi-Post and Flexi-Flange, also manufactured by Essential Dental Systems,
Inc., are split-shanked, parallel-threaded posts with the proven ability
to achieve maximum retention with insertional stresses no greater than
those of a passive post. Of equal importance is the ability of the
post to distribute the functional stresses along the entire length of the
shank—a requirement that the parallel-threaded, split-shank design of the
Flexi-family fulfills most efficiently.
“Bendability”
When the posts are made of stainless steel, they impart a “bendability”
almost equal to the flexibility of dentin, reducing the chances of gap
formation between the core and the body of the root. The bendability of
a material is a function of the modulus of elasticity and the cross-sectional
area of the material being tested. These dynamics are quite different from
the limited resilience of ceramics. Because of the nongiving nature of
the ceramic material, ceramic posts transmit most functional stresses to
the root rather than absorbing them in the material itself.
Highest Recorded Retention
The split-shank design of Flexi-Post and Flexi-Flange ensures that the
threads engage the dentin with minimal lateral stress, yet produce the
highest recorded retentions found in the literature. The even distribution
of stresses optimizes the long-term success of the underlying support and
makes the final restoration more predictable.
Conclusion
Success is the ultimate esthetic challenge. Nothing looks worse than
a fractured root. Loosened or fractured posts do not look good either.
Like beauty, esthetics is truly in the eye of the beholder but the esthetic
success of a restoration is usually noted and enhanced when form follows
function.
The split-shank design of the Flexi-family of posts
creates an architecture that integrates the needs of a supportive post
and high retention with those of the root, minimal insertional stresses.
Harmony like this can also be called esthetic.
November-December 2003
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FIGURE 1: Flexi-Flow Natural
Composite Cement.
FIGURE 2: Ti-Core Natural
Core Material.
FIGURE 3: The color of the
metal post is masked.
FIGURE 4: The esthetic results
are improved.
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