Osteonecrosis and Ischemia in the Alveolar Bones

At a recent seminar, Dr. Jerry Bouquot, the director of diagnostic services at University of Texas, Houston - School of Dentistry, and world reknown oral pathologist and specialist in bone pathology, discussed osteonecrosis of the alveolar bone and issues with ischemia in bone.

The recent issues with bisphosphonate induced osteonecrosis of the jaw bones and well known complications with osteoradionecrosis, demonstrate the severe complications that can occur with ischemia in bone. Dr. Bouquot shared some of his ideas regarding possible sources/causes of ischemia in bone.

The follow video clip highlights the differences between alveolar bone and regular skeletal bone. According to Dr. Bouquot, these differences make the alveolar bone more susceptible to ischemic bone pathology.

Finding Missed Canals Using Cone Beam Computed Tomography (CBCT)

We have had lots of discussion regarding the use of CBCT in endodontic diagnosis and treatment planning. CBCT is the future of endodontics. 3D imaging as an adjunct to 2D imaging is superior to 2D imaging alone. The ability to evaluate a tooth in a sagittal and axial plane (in additional to the traditional coronal view of standard radiographs) provides valuable information that will lead to the preservation of teeth by improved endodontic treatment, endodontic retreatment and endodontic surgery.

There will be many who think this statement is over the top. However, I would compare the advent of focus-field, high resolution CBCT to the introduction of the operating microscope in endodontics. While there was initial resistance to adoption of the microscope, and still some continued resistance by a few in our specialty, the microscope has undoubtedly improved the quality of endodontic care. CBCT is the same. There will be some who argue that they don't need it, however, it undoubtedly will improve the quality of endodontic care and help preserve teeth.

As an example of the benefits of CBCT in improving endodontic diagnostics and treatment, I present the follow 4 cases. Each case completed by a different endodontist. All of these clinicians are highly skilled endodontists using microscopes. However, in each case, canals were missed and the patient continued to have issues. They have different stories, but all ended up in our office for an evaluation or second opinion. I have included myself as one of these 4 endodontists. (One of the cases is my own)

CASE #1

#31 is the symptomatic tooth. Two canals have been filled to a good length.

CBCT slice of mesial root shows the two mesial canals join and exit at one apex.

This is another slice of mesial roots showing the buccal filling and the ML missed canal. The sagittal view tells us where to look when we retreat this tooth. Axial view also demonstrates the missed canal. Using these two views, when I retreat this tooth, I will know where to explore without perforating the root.

This particular endodontist refunded the patient and preferred that we retreat the tooth at our office.

CASE #2

This root canal was treated by another endodontist and then retreated after symptoms failed to resolve. She came to Superstition Springs Endodontics for a second opinion. The obturated roots look filled to an ideal length.

CBCT reveals a missed MB#2 canal. Blue outline shows an axial slice of the MB root. The pear-shaped root outline reveals the missed canal.

The sagittal view also shows the MB#1 canal is off center of the long axis of the root. A lesion into the sinus cavity is noted. Note the distinct MB lesion visible in the CBCT. I explained to the patient that it would be the other endodontist would likely retreat this tooth at no charge, but this patient has elected to retreat the tooth in our office.

CASE #3

This root canal done in 2007. Recently became symptomatic.

CBCT shows lesion on MB and DB with elevation of floor of sinus. This corresponds to chronic sinus issue patient has been dealing with.

Cross sectional slice (axial) through the MB root shows the missed MB#2 canal. The pear-shaped or figure-8 shape of the MB root reveals the missed MB#2 canal.

This sagittal view shows that the missed MB#2 canal is actually a separate root. While the roots are fused all the way down, it has its own apex.

The CBCT is a map for retreatment. It tells us exactly where to look to find the missing canal.

This patient returned to her previous endodontist for retreatment.

I know each one of these endodontists, and they all do excellent work. I confidently suggested to each of these patients that they return to their previous endodontist for evaluation. Using the CBCT map for retreatment, I am confident each one of these endodontists will find the additional canal. One endodontist is retreating at no charge, one endodontist is refunding patient and she will have treatment in our office, and the third patient did not want to return and has elected to pay for retreatment in our office.

CASE #4 - My Missed Canal Found with CBCT

I completed this RCT in Nov 2011. Palatal lesion seemed to improve, but patient symptoms returned. In this particular case, I found only 2 canals. After extensive searching under the microscope, I determined that this must be one of those tricky 2 rooted Mx molars. Since symptoms returned, we took CBCT to see if I missed anything.

CBCT reveals that I did miss a DB canal. However, looking closely at the axial view, my assumption that this is a 2 rooted molar was correct. The palatal and DB roots were fused as one. Sagittal view shows the missed DB canal. Axial view shows the missed DB as well. The CBCT is now a map for retreatment.

As explained, the axial and sagittal view provided by CBCT is invaluable. More information provides for better treatment. This post should demonstrate the level of complexity of molar endodontic therapy even with the use of the operating microscope and the benefit of 3D imaging over 2D imaging alone.

Challenging Isolation

Occasionally, as an endodontist, we are referred a patient for a difficult, maybe questionable, save. This patient was 85 years old and was undergoing cancer treatment. He was referred late one afternoon for treatment of #32. The referring dentist had started the root canal treatment earlier in the day and had stopped due to difficulty locating the mesial canals. The patient arrived with his tooth anesthetized and with IRM in the access. Tooth #32 is the distal abutment of a longspan FPD, and the dentist was confident that it could either be saved or a new FPD fabricated and fit.

Upon access, it was immediately clear why the tooth was a challenge for the referring dentist (if being a tilted third molar bridge abutment on an elderly patient wasn't enough). The mesial gingiva had overgrown beneath the FPD and there was still caries everywhere. Both saliva and blood were flooding beneath the rubber dam and into the access.

After cleaning the caries, resecting the gingiva, and controlling the hemmorhage with astringedent, I called the general dentist on his cell phone to have his restorative input. There was minimal supracrestal tooth structure remaining on the mesial, and I questioned the restorability of the tooth. The dentist was dismissive of any alternatives and confidently requested I complete the treatment.

At this point, something needed to be done to maintain a clean dry field. It became clear very quickly that our normal ancillary use of Oraseal calk was not enough. I had my assistant maintain a steady stream of air on the tooth while I inserted size 6 hand files into the two mesial canals, and a size 30 file into the distal canal. I would recommend lubricating the files with vaseline before placing them. I then maintained the air stream while my assistant mixed up a loose batch of IRM. I placed the IRM and compacted it within the access and around the files before trimming back the material that flowed out beneath the crown.

As the IRM set, I moved the files in a circular patterns to prevent them from locking in and to create a funneled pattern of space. Upon setting, I removed the files and was left with perfect pathways. Through these, I did my cleaning, shaping, and obturation.

Here is the final result:

This technique can be applied to any situation in which caries is removed beneath a fixed restoration, and the restoration is to be maintained to hold a rubberdam and act as a temporary.

If you have any questions or clinical tips to share of your own, please post them in the comments below.

Also, if you are new to the blog, you can also see more of my cases on my office's facebook page: www.facebook.com/alpharettaendo

Thank you!