Pulpal Regeneration continued from page 40
be artificially induced in other immature necrotic teeth⁶. At that time, it was not pos- sible. However, decades later, with the advent of dental operating microscopes and MTA, pulpal regeneration finally became a reality. The first case report was published in 2001⁷.
THE BIOLOGY
There are three key players involved in this process: stem cells, scaffolds and growth factors. Stem cells are undifferentiated cells with the capacity to divide and/or differenti- ate; scaffolds provide support for the stem cells, aiding in cell organization, prolifera- tion, differentiation and vascularization; and, growth factors are signals that induce cellular proliferation and/or differentiation⁸.
The basic process involves disinfection of the canal, introducing the stem cells, scaffolds and growth factors, and then letting the body take over. The growth factors signal the stem cells to become odontoblasts, cementoblasts and/or fibroblasts, while the scaffold provides necessary support⁸.
THE CLINICAL PROCESS
Pulpal regeneration is typically a two- to three- appointment procedure. After diagno- sis and treatment planning, start with local anesthetic administration and rubber dam placement. Next, access the pulp chamber, and evaluate for vital tissue. If vital tissue is present, there is no need to regenerate it; instead, we can remove any unhealthy pulp, place an MTA pulp cap and monitor the tooth for continued development. If no vital tissue is present, however, continue with pulpal regeneration.
You do not want to remove any dentin, so during this process, aside from a small K file used to measure working length, you will do no instrumentation. Instead, rely on copious irrigation to disinfect and debride the canal space. Use the usual irrigants—sodium hypo- chlorite (NaOCl), ethylenediaminetetraacetic acid (EDTA) and chlorhexidine (CHX). Start with NaOCl, which is antimicrobial and dis- solves pulp tissue. Next, clear out the NaOCl
with saline and then irrigate with CHX. CHX is a useful addition to the process because it bonds to dentin and continues to exert an antimicrobial effect for up to 90 days⁹.
After drying the canals, place an interap- pointment medication and a temporary fill- ing. There are several medicaments used for this process. The most common is a mixture of three antibiotics—metronidazole, cipro- floxacin and minocycline¹⁰. To avoid staining, the minocycline is often left out in esthetic situations. The medication is left in place for two to four weeks.
At the second appointment, use local anesthetic with no epinephrine (the logic behind this will become clear shortly). Place the rubber dam, re-access and then irrigate with NaOCl followed by EDTA. EDTA is a chelating agent that decalcifies the dentin, exposing collagen and causing the release of growth factors. Next, dry the canals.
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The next step is to stimulate bleeding into the canal from the periapical tissues (this is the reason you don’t want epinephrine con- stricting blood vessels in the area—it makes it much harder to get sufficient bleeding). Do this by taking a small instrument beyond the apex. You want the entire canal to fill with blood and a blood clot to form. This serves two purposes: First, it brings in stem cells that are present in the periapical tissues¹¹. Second, the blood clot will serve as a scaffold.
The three key players now have been intro- duced—stem cells, a scaffold and growth fac- tors. The last step is to seal off the area and keep bacteria out. This is done with this with MTA, which has great sealing capabilities and is exceptionally biocompatible. Place MTA on top of the blood clot and then restore the access with any normal filling material.
The patient will need to be seen for follow ups to ensure that the procedure was suc- cessful. Typically, it takes around 12 months to see healing of the radiolucency, 24 months to see changes in root thickness and 36 months to see significant root growth¹².
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Thus far, the evidence is overwhelmingly positive. One study found that after two
42 focus | SEP/OCT 2014 | ISSUE 5
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