What percentage of crown-prepped teeth become necrotic?

Kelly, M Tooth #30 Pre Op 8-22-16

2TheApex:  Roughly 10%

One statistic you may want to share with patients is that 1 in 10 teeth with crowns end up requiring root canal therapy. Here is the Study.  Not a bad statistic for patients to know prior to a crown prep.  There is always a risk.  The more highly the tooth is restored increases the chances.


Kelly, M Tooth #30 Post Op 8-22-16


What are the most recent guidelines regarding bisphosphonates?

2TheApex:  Guidelines for patients taking antiresorptive medications can be found here.


The AAOMS recently released a position paper about medication-related osteonecrosis of the jaw (MRONJ).  Bisphosphonates are the most common class of medication associated with MRONJ.  The definition has been expanded, however, and now includes medications taken by more than 5.1 million people over the age of 55.  Dental procedures which expose and/or damage bone have the potential to cause osteonecrosis for these patients.  The highest risk category is IV cancer therapy, which is about 100 times higher than patients being treated for osteoporosis.  Patients taking oral bisphosphonates for greater than 4 years are at an increased risk and should consult with their physician regarding a 2 month drug holiday prior to invasive treatment such as extraction.  Patients should be treated aggressively prior to, and direct osseous injury should be avoided during, IV therapy.  This could mean root canal treatment in lieu of extraction, if they are high risk.  I highly encourage you to review the paper itself, as there much more information provided there.




How many canals are in that tooth?

2TheApex: Expect multiple canals until proven otherwise.

Except for maxillary anteriors, all teeth should be expected to have more than one canal. Some commonly missed canals are MB2, the lingual canal in mandibular anterior teeth, second (or third!) canals in premolars, and a second distal canal in mandibular molars. Recently I had a very interesting case that was a new one for me: a second palatal canal in a maxillary molar.



Cone fit: Note palatal cone offset to the distal of the root.


Final: 4 canals, with 2 canals in the palatal root.


The palatal canals shared a common orifice, and the additional canal was not evident on initial access.  The canals bifurcated apical to the orifice, and the second canal was located with the aid of the dental microscope to the mesial.  A very interesting case, and a good reminder to always expect the unexpected.

Which irrigating solution is the best?


2TheApex:  Sodium hypochlorite

An ideal endodontic irrigant disinfects the canal, act as a lubricant, removes debris, dissolves tissue, removes the smear layer, and is safe for the patient.  Although there is no perfect irrigating solution, one does stand head and shoulders above the rest: sodium hypchlorite (NaOCl).  In a review article of irrigating solutions, Haapasallo stated “It is difficult to imagine successful irrigation of the root canal without hypochlorite.”  Sodium hypochlorite cannot fill all the criteria by itself, and so a chelating such as EDTA is used to help facilitate smear layer removal, but no other irrigant fits the criteria of an ideal irrigating solution better.  There are risks to using sodium hypchlorite, and it must be used with caution to avoid extrusion into periapical tissues.  Other irrigating solutions have been shown to be potentially beneficial in some circumstances, but if possible they should be used as an adjunct and not as the only irrigant.  At this point in time, the research is clear that NaOCl is the best endodontic irrigating solution available.


What is successful root canal treatment?

2TheApex: A functional, asymptomatic tooth with no clinical signs of pathosis can be considered successful even without complete healing of the ligament.

Endodontic success has traditionally been defined as the prevention or elimination of periapical disease following root canal treatment, meaning both complete healing of the PDL radiographically and absence of symptoms clinically. However, utilizing CBCT to evaluate PDL healing Patel showed a 25% reduction in “success” compared to periapical radiographs. Many of these teeth are still in function, asymptomatic, free of active disease, and esthetic; yet fail to meet the above, very stringent, definition of endodontic success. Has treatment been unsuccessful in these cases? How do we measure success clinically? Does it really even matter what definition we use for “success”? Having a clear definition of success is important because treatment plans are be based largely on the prognosis of treatment options. Endodontic treatment and implant placement will frequently be compared, however most implant studies define success as simply survival of the implant. (Iqbal) Helping patients maintain their natural dentition is a primary goal of endodontics, and a definition of success that emphasizes survival more closely aligns with both patient goals and allows for the most accurate comparison of treatment options. Doyle addressed this discrepancy directly by analyzing both the success and survival of implant and endodontic treatment, which resulted in almost identical success and survival rates. A financial evaluation, however, shows that in most circumstances endodontic treatment is the most cost effective option. (Pennington)

preop #30

Pre-Op #31 Pulp Necrosis with                                 Chronic Apical Abscess

Post-Op #31

Post-Op #31

18 Mo. Recall.  Asymptomatic.

18 Mo. Recall. Asymptomatic. Case by Dr. Nordeen


Restoration of teeth following endodontic treatment.

2TheApex:  Endodontically treated teeth not restored with a crown are 6 times more likely to be lost.

A good restoration is just as important to the success of root canal treatment treatment as the quality of obturation. (1)  While it has been shown that the dentin of endodontically treated teeth is not more brittle than their vital counterparts, they often experience a reduction in overall strength from loss of tooth structure. (2)  Loss of even one marginal ridge, such as in an MO or DO preparation, can reduce the strength of a posterior tooth by 46%, loss of both marginal ridges results in a 63% reduction, while a conservative endodontic access will only reduce the strength of the tooth by about 5%. (3)  A crown may not be indicated for every tooth following root canal treatment, however Aquilino showed that teeth not restored with a crown were lost 6 times more frequently than those restored with a crown. (4)

1: Ray, H. A., and M. Trope. “Periapical status of endodontically treated teeth in relation to the technical quality of the root filling and the coronal restoration.”International Endodontic Journal 28.1 (1995): 12-18.

2: Sedgley, Christine M., and Harold H. Messer. “Are endodontically treated teeth more brittle?.” Journal of Endodontics 18.7 (1992): 332-335.

3:  Reeh, Ernest S., Harold H. Messer, and William H. Douglas. “Reduction in tooth stiffness as a result of endodontic and restorative procedures.” Journal of Endodontics 15.11 (1989): 512-516.

4: Aquilino, Steven A., and Daniel J. Caplan. “Relationship between crown placement and the survival of endodontically treated teeth.” The Journal of prosthetic dentistry 87.3 (2002): 256-263.

Length Determination

2TheApex Electronic apex locators the most accurate method of determining canal length.


Accurate length determination is essential for adequate root canal treatment.  Root canal space that has not been adequately cleaned is a potential nidus of bacteria which may lead to future periapical pathosis.  On the other hand, over extended obturation material will create an inflammatory reaction that can cause pain and impede healing. (1)  The two most common methods of length determination are radiographs and electronic apex locators (EALs).  Radiographs are an indispensable tool that will yield much more anatomical and diagnostic information than just the length of the canal, however, in vivo studies directly comparing the accuracy of the two techniques have shown that EALs are more accurate in locating the apical foramen. (2) This is due to the apical foramen being located an unknown distance from the radiographic apex, a difference which will not always be evident on a periapical radiograph.  A recent meta-analysis by Schaeffer showed that the best prognosis is obtained when the canal is adequately obturated between 0 and 2 mm from the radiographic apex, highlighting the need for accurate length determination for successful outcomes. (3)  In addition to length measurement, EALs will aid in the diagnosis of perforations and resorption. (4, 5) Modern apex locators operate on a principal of relative ratios of impedance which allows them work in the presence of any common irrigating solution, and are accurate in both vital and necrotic teeth. (6,7) EALs are technique sensitive, but when used in conjunction with necessary radiographs will yield the most reliable and accurate results.


1: Ricucci, D., and K. Langeland. “Apical limit of root-canal instrumentation and obturation, part 2. A histological study.” International Endodontic Journal 31 (1998): 394-409.

2: Williams, Clayton B., Anthony P. Joyce, and Steven Roberts. “A comparison between in vivo radiographic working length determination and measurement after extraction.” Journal of endodontics 32.7 (2006): 624-627.

3: Schaeffer, Michelle A., Robert R. White, and Richard E. Walton. “Determining the optimal obturation length: a meta-analysis of literature.” Journal of endodontics 31.4 (2005): 271-274.

4: Kaufman, A. Y., et al. “Reliability of different electronic apex locators to detect root perforations in vitro.” International endodontic journal 30.6 (1997): 403-407.

5: Goldberg, Fernando, et al. “In vitro measurement accuracy of an electronic apex locator in teeth with simulated apical root resorption.” Journal of endodontics 28.6 (2002): 461-463.

6: Shabahang, Shahrokh, William WY Goon, and Alan H. Gluskin. “An in vivo evaluation of Root ZX electronic apex locator.” Journal of Endodontics 22.11 (1996): 616-618.

7: Dunlap, Craig A., et al. “An in vivo evaluation of an electronic apex locator that uses the ratio method in vital and necrotic canals.” Journal of Endodontics 24.1 (1998): 48-50.


Sometimes it's a leap of faith.  Most of the time it's better to have a spotter.

Sometimes it’s a leap of faith. Most of the time it’s better to have a spotter.

We are in the process of starting this blog to help our referring doctors better their clinical practice.  The information will be clinically based and laid out in a simple and concise format to respect your time.  Information will be supported by research and explained after we have gotten 2theapex.  Thank you for visiting.  Any feedback is appreciated.


Dr. Derek B. Nordeen