Restorative endodontics: a new biologically based standard of care

Dr. Dennis G. Brave discusses minimally invasive techniques and advanced material science

It is unlikely that G.V. Black, 1836-1915 (considered the Father of Restorative Dentistry), could have imagined the direct bonding of modern-day composite materials to coronal dentin, or that Louis I. Grossman, 1902-1988 (the recognized Father of Endodontics), could have imagined bioceramic sealers that could bond to radicular dentin.

But both of these giants of our profession advocated the latest theory, techniques, and technology of their day. They could only dream about the future … and the future is here and now! All of us recognized the need for “retentive preparations” for the successful placement of an amalgam restoration (when there was no other option).  Many of us continue to use “condensation techniques” and consider them a requirement for the successful filling of root canals (but now there are other options).  It should be remembered that these techniques were advanced based on the physical and chemical properties (limitations) of the materials that were available to us at the time. Today we have new and better materials that do not require these techniques.

It should be stated from the outset that the reason for restoring a cavity and/or performing a root canal are both the same — to restore a tooth to its natural function and to preserve that tooth in that state for as long as possible. Let’s start with the latest materials, technology, and techniques available to accomplish that task in endodontic therapy. You were probably taught that gutta percha needs to be heated and condensed to achieve 3D obturation, that your endodontic sealers are the weak link in your root canal procedure, and that it didn’t matter how you got to the apex, only that you got there. Well, that was in the past. Present-day material science has antiquated these and many other concepts that you may have learned and are still using.   

If we concede that the fundamentals of root canal therapy are cleaning, shaping, and obturation, then it would make sense to look carefully at how each part of the procedure interfaces and supports the other. In addition, it is also important to consider how each part of the procedure supports the objective of maximizing the long-term retention of the endodontically treated tooth.

Let’s consider the past and current state-of-the art in root canal sealers. Approximately 50 years ago, Dr. Louis Grossman acknowledged that the then current-day sealers (zinc oxide and eugenol and resin-based sealers) left much to be desired. They were hydrophobic, shrunk upon setting, were not very biocompatible, lacked resistance to wash out, and generally were irritating if extruded past the apex. Because of these less-than-stellar characteristics, it became accepted theory and practice to try and reduce the sealer interface to the thinnest possible thickness in the root canal. It being well understood that the thicker the sealer interface, the greater the shrinkage, the more irritating, etc. So, all of our obturation techniques (warm vertical, cold lateral, and even heated carrier-based) were developed based on the recognition that the then current sealers were at best poor and that the gutta percha should displace as much sealer as possible.
Present-day material science has allowed us to produce nanoparticle bio-ceramic root canal sealers (EndoSequence® BC Sealer™, Brasseler USA) that meet all of Dr. Grossman’s ideal requirements for an endodontic sealer. They do not shrink upon setting, are biocompatible, are osteogenic by their nature, are hydrophilic, antibacterial, and produce hydroxyapatite upon setting. They are also highly radiopaque, premixed, and will produce a true chemical bond to the dentin and gutta percha when used with a bioceramic-coated cone (BC Sealer and BC Points, Brasseler USA). Because we are now able to chemically bond to the radicular dentin (right down to the apex), we are now able to produce a true monoblock for the first time. This is why it can be said that the restoration of an endodontically treated tooth should begin at the apex.

What about “condensation techniques” that have used (as a bases of their acceptance) the idea that we should replace the sealer with gutta percha? That the sealer is the weak link in the chain and should be reduced to the thinnest layer possible in the root canal? They are antiquated and without merit when we can now say that we have root canal sealers that are superior to gutta percha in the canal. At best, gutta percha takes up space and is inert.

It should be acknowledged that we still deliver the sealer and provide a retreatment path with a bioceramic coated cone. However, traditional condensation is not necessary because of the hydraulic nature of the bio-ceramic sealer.

But this is not the end of the story. Actually, it is just the beginning! For years the techniques used to prepare and shape canals have focused on trying to not only clean the canal, but also produce a shape that will provide for the difficult task of condensing gutta percha. Something we now understand is actually completely unnecessary. Cleaning, it turns out, can be accomplished with minimal coronal enlargement, particularly if facilitated with ultrasonics and good irrigation techniques.  All that is really required is to produce a shape that allows the canal to be cleaned responsibly to the apex. A size 35/.04 preparation to the apex has been documented as all that is needed in most canals. We now have hydraulic obturation techniques utilizing flowable nanoparticle bioceramic technology that do not require excessive canal enlargement. Obturation should not dictate shaping! In doing so, we have excused preparations that have removed good tooth structure (dentin) at the expense of the long-term prognosis of the tooth. Teeth (canals) that are overly prepared and weakened to accommodate filling techniques in the long-term lead to unnecessary fractures and their removal.

Minimally invasive root canal shaping is really what we should be focused on in an effort to preserve as much radicular dentin as possible. We should be maintaining the innate strength of the tooth through the use of root canal sealers that bond to the radicular dentin and instrumentation and obturation techniques that do not require the excessive removal of dentin. We have begun to look carefully at shaping and recognize that all instrument systems are not the same and do not accomplish the same goals. Some years ago, it was recognized that constant tapered file systems would consistently produce (versus variable tapered) minimally invasive shapes in the root canal. Further, that synchronization of all the parts of the procedure (i.e., the instruments, paper points, gutta percha, and posts) would lead to the removal of less structurally important dentin. Posts were designed to fit the space that the last rotary instrument actually produced. Thus, the first drill-less post system was developed with the recognition that the preservation of radicular dentin was critical to the responsible restoration of an endodontically treated tooth.  

Those that claim that root canals fracture and don’t hold up for the long term do not recognize the importance of maintaining the inherent strength of a tooth throughout the root canal procedure by the use of minimally invasive techniques and technology. Root canals that are carried out with instrumentation systems designed to retain as much coronal radicular dentin as possible and are restored utilizing bonded obturation (BC Sealer) will stand up to the test of time. Restoration of an endontically treated tooth should begin at the apex. Through the use of minimally invasive techniques and advanced material science, this is now a reality.