In my previous post “The Little Devil Horn,” I showed a case of fractured Dens Evaginatus (DE) that had resulted in pulpal necrosis in an 11 years old girl. In almost all cases the tubercles fracture off as soon as the teeth come into occlusion. The resultant pulp exposure goes unnoticed until patient develops pain and symptoms and a combined endodontic-restorative procedures would then be necessary. Therefore, just observing what does not belong to a proper occlusion is not a good choice.
The endodontic treatment for necrotic teeth with immature roots is either regenerative endodontics or MTA apexogenesis depending on many factors. The latter was used to treat the case of fractured DE with pulpal necrosis.
So, what should we do if we face a vital tooth with an intact tubercle?
Some evidence suggest a gradual shaving off the tubercle over a period of few months in order to allow tertiary dentin formation is the treatment of choice. However, tertiary dentinogenesis may not provide a complete seal of the pulp chamber as this process lays down an irregularly formed dentinal structure.
Another approach would be to remove the tubercle mechanically under RD isolation and to seal off the resultant mechanical exposure, if any, with bonding material. This approach was performed for the same young patient for tooth #3-5.
Dens evaginatus (a.k.a. Leong’s premolar) is an odontogenic developmental anomaly. This anomaly, an enamel-covered tubercle with an extension of pulp horn in most cases, occurs primarily in premolars. Loss of this tuberculated cusp during natural root maturation and development will result in early pulp exposure, pulpal necrosis, periapical disease, and arrested root development. Early diagnosis and management of dens evaginatus is therefore the key factor in preventing premature loss of tooth vitality.
If you attended my lecture at the Pacific Dental Conference last month, I mentioned “The Laws” that allow us to safely and predictably locate canals without being worried about mishaps (i.e. perforations, over-enlarged access cavities, etc.). One of the scenarios that we have to always be prepared for is accessing through a crown that is placed on a rotated tooth. One of the key elements discussed was the use of a probe to gain a better appreciation of the root outline at the CEJ level. The “Law of Concentricity” then allows us to start our access cavity preparation in the right direction.
The case below shows a rotated tooth #1-4 under a PFM crown. Preparing a typical access cavity in the Buccal-Lingual direction would definitely result in mishaps. Understanding the orientation of the tooth prior to the start of root canal treatment can result in achieving a safe and a conservative access prep. Note that even the rubber dam clamp wings are not good guides for the orientation of the chamber floor and for locating canals.
As if dealing with MB2 canals in upper molars was not complicated enough (see my previous post on MB2 canals), here is another thing to consider when doing root canals on lower molars:
The presence of an independent Middle Mesial (MM) canal has been reported for decades in endodontic literature. Owing it to technological advancements, it appears that the incidence rate for these extra canals is on the rise: Skidmore & Bjorndol 1971 (0%), Pineda & Kuttler 1972 (0%), Vertucci 1984 (1%), Fabra-Campos 1989 (2.6%), Goel et al. 1991 (15%). I even hear incidence rate of up to 60% based on the more recent micro-CT studies. This may be pushing it though!
It is really important to realize that MM canal could exist and therefore, the area between MB and ML canals in lower molars should be explored thoroughly during accessing, locating canals and instrumenting.
When I went through my undergraduate dental training, I was taught that MB2 canals in upper molars are there 60-70% of the time. Newer tools and techniques show us that MB2’s are always there whether or not we can get to it. As a matter of fact I tell our endodontic residents at UBC that “if you haven’t found it, you have missed it“.
Here are some pointers on how and where to find the canal that can potentially result in endodontic failure if left untreated, specially if the tooth is necrotic to begin with:
MB2 is always there!
It is always located palatal to MB1.
It is always mesial to the line running between MB1 and P canals. This is the only safe area to trough.
A good magnification and illumination is necessary.
The access should be big enough to allow for adequate visualization of the pulp floor colour and map.
Only instruments/burs (such as Munce Discovery Burs) that produce smooth troughing surface should be used. This is a more conservative and much cheaper option than using ultrasonic tips.
There is absolutely no need for using explorer to poke and create misleading holes on the pulp floor.
If there is no indication of the canal initially just start by troughing from MB1 mesio-palatally.
Use copious irrigation to remove all debris created during troughing.
The troughing should continue until a small size file can easily drop into this canal. This point of entry could sometime be 2-4 mm below the pulp chamber floor.
Do not trough and hope you can find the canal. Always observe the colour changes on the floor and look for the clues.
Know your limits and when you hear the whisper in your ears asking you to stop, listen to it!