The Implications of Visualizing Pulpal Anatomy in Three Dimensions

The first implication is that we will be visualizing a more accurate picture of what actually exists. Limiting our perception to what we see in a mesio-distal periapical x-ray and assuming an equal symmetry exists bucco-lingually implies we see pulpal anatomy as a two dimensional structure with no depth. This would be a misleading concept even if pulpal anatomy were perfectly symmetrical which in many cases it is not. 

We can appreciate the three-dimensional configurations of pulpal anatomy when we gain access to the canal orifices exposing an axial view that often displays orifice openings in c-shaped forms, particularly the distal canals of mandibular molars. We may also see thin bucco-lingual isthmuses extending from mb and ml canals. The mb canals of maxillary molars are often highly oval in the bucco-lingual plane. If we employ cbct x-rays we will clearly identify the non-conical anatomy of many pulpal inclusion bodies.

 Noting these deviations from conical anatomy should guide us during instrumentation. The goals include removal of as much pulp tissue as possible, thorough activated irrigation of the entire canal space, followed by three-dimensional obturation. To reinforce the concept of three-dimensional instrumentation, we should be aware that long standing non-vital infected teeth are likely to be populated with biofilms that are firmly attached to the canal walls along the length of the canals. It is a challenge to remove biofilms and those thinking in two-dimensional terms are less likely to effectively remove them simply because there is a lack of vigorous instrumentation in the bucco-lingual plane. 

One reason the bucco-lingual plane is not addressed as aggressively as it should be is a mind set that considers the main purpose of instrumentation to be to first create a glide path that can subsequently be followed by some form of rotary instrumentation that is most often limited to centered positioning to reduce the incidence of instrument separation. If the goal of glide path creation is to simply create a space that rotary instruments can follow, it deemphasizes or completely eliminates the concept of three-dimensional cleansing. The function of glide path creation is far more important than producing a space that rotary instruments can safely follow.

It is at the glide path creation stage, where the reality of three-dimensional shaping is most vigorously addressed. The means to aggressively attack highly oval anatomy, thin pulpal isthmuses, flat pulpal configurations and the biofilms that may be ensconced in any of these configurations is readily available. By employing stainless steel reamers from a thin 06/02 through a 15/02, in a 30o handpiece oscillating at 3000-4000 cycles per minute, leaning against the canal walls circumferentially, the irrigants are activated improving their effectiveness. The stainless steel reamers have unique properties not possessed by NiTi instruments of similar dimensions.. Thin enough to be highly flexible, they also have enough “body” to mechanically remove dentin and the attached biofilms from the canal walls, unlike thin NiTi instruments that will deflect from the canal walls upon first contact. 

These properties are the necessary requirements to effectively create a cleansed glide path in three dimensions.  Activated irrigation and aggressive contact of all canal walls along their entire length. The process described here is one I term “internal routing”, a form of initial canal preparation that fully addresses pulpal anatomy in three dimensions and at the same time activates the various irrigants that work synergistically to remove stubbornly attached biofilms.

 A three-dimensional preparation no greater than a 15/02 is all that is required to prepare the canal space for the introduction of a rotary system, its purpose no longer having the prime requirement of cleansing, but simply sizing the canal for the placement of a well fitting gutta percha point that will ultimately be placed into a canal thoroughly flooded with sealer. This last statement should be questioned. What I am implying is that the glide path phase of canal preparation has likely removed practically all the pulp tissue. The thinner pulpal extensions are not going to be better cleansed when thicker tipped and greater tapered instruments are taken to the apex.  

If any pulp tissue is remaining, it will be found in the wider portions of the canal system, those that will be addressed by the wider and greater tapered rotary instruments. It is counterproductive to attempt to enter thin pulpal isthmus-like spaces with these rotary instruments. Attempting to enter into these spaces increases the chances of instrument separation and weakening those portions of the roots that are already thinner and more vulnerable to dentinal microcracks and strip perforation. 

 Interestingly, when we developed the rotary SafeSiders HF, I originally designed them for the purpose of entering tight spaces without increasing the incidence of breakage, something that we successfully tested. However, despite this design advantage, I realized upon further thought that entering into sites that are supported by significantly less dentin does not improve the tooth’s prognosis. For the most part, I utilize the SafeSiders HF rotary system to enlarge the main canal spaces to either a 30/02 or 30/04 depending upon the original mesio-distal canal dimensions. It should be noted that when removing dentin with an instrument no wider than a 30/04, the bulk of the dentin will be shaved from the mesial and distal canal walls with some of the debris impacted buccally and lingually. That impacted debris potentially blocking the flow of cement into these areas is removed by a final use of the 15/02 in the 30o oscillating handpiece to leave a debris-free space. 

Visualization guides us. By accurately visualizing the mechanical challenges, the negative repercussions of prior techniques are eliminated and a simpler, more adaptable approach is implemented. 

Regards, Barry