Dental practice has for decades utilized calcium hydroxide
as a material for pulp capping and cavity lining. This use is based upon: the
biological response of the pulp to isolate itself from calcium hydroxide, and that
after initial cell necrosis, the pulp produces “reparative” dentin as a barrier
between the pulp and the calcium hydroxide.
One of the statements about biological repair that I learned
along the way was that “we” have a much better system of dealing with acidic
challenges as opposed to basic challenges. Meaning our bodies can deal with
acids much better than bases. Feel free to challenge me on this point, or add
some factual detail. My primary assertion here is that the “healing” produced
by calcium hydroxide may not be the best stimulus to result in an ideal,
healthy situation. For example, continuous insult or injury from calcium
hydroxide can result in de-vitalization of the tooth and end in complete
calcification of the tooth. I hear you, some are already saying maybe that is
not a bad thing.
No calcium hydroxide liner can really claim to be
bio-compatible, it “works” by killing every cell in sight. Try putting any pH
14 material in a Petrie dish of cells and see what happens next. Thus the need
for palliative basing materials such as zinc oxide -eugenol to as we say “quiet
down” the pulp. Again, place a nano-scale amount of eugenol in a Petrie dish
and see what happens, i.e. eugenol is one of the most toxic compounds known. As
a tooth pain relieving treatment this dates back centuries. My premise: as much
as I like eugenol, there must be a better way.
Another major disadvantage in use of the calcium hydroxide
liners, or even calcium silicate (Portland Type III Cement), is that they have
very little or no adhesion to dentin, and as a consequence often come loose
when placing a composite material over them, let alone condense an amalgam on
top of them, as we once did.
Within the last decade, dental material products now contain
needed components to aide in tissue accommodation, such as in re-mineralization
with amorphous calcium phosphate (ACP). These compounds have been used in some
sealants and in some composites for quite a while. A few companies are now advertising
them as “bio-active”.
There has been a new class of cavity liners that have been
introduced that follow this approach, one of providing essential components for
repair such as calcium, that are bio-compatible, and are also bio-adhesive.
Bio-adhesive being defined as a material that is both bio-compatible and has
biologically active adhesive components. These new cavity liners are also
highly radio-opaque, with an aluminum equivalent of 3.5 mm, meeting the ISO 4049
standard to be classified as radio-opaque, using the more stringent endodontic
requirement. This radio-opacity allows them to be easily observed in comparison
to dentin and enamel.
Want more? In addition these new cavity liners are truly
anti-bacterial, bacteria being a primary cause of sensitivity associated with
secondary caries. These new cavity liners handle much better that the older
calcium hydroxide liners or calcium silicates, and are esthetic compared to the
grey calcium silicate liners.
So, I encourage you to take a look at this new group of
cavity liners based upon the biological principles of bio-compatibility and
bio-adhesion.
