RCT for the tooth with limited access

Limited access situations, like third molars and restricted mouth opening, seem more amenable to extractions than endodontics. But then endodontics has always been regarded as a blind procedure. So what really makes a limited access situation, like buccally erupted third molars, oral submucous fibrosis, older patients with thick buccal fat, Bell's palsy or microstomia challenging? More than the visibility, it is access for the endodontic instruments that raises the doubt of the best course of action.

  So here are some suggestions on how to perform RCT for the upper third molars or when the patient has a restricted mouth opening. Again this blog is not about the decision whether the tooth with difficult access should be extracted or root canal treated; rather it is about making that decision free of the fear of failure when access is indeed possible.

I. Improving access from the patient.

1. Using a bite block. A bite block placed on the opposite side of the mouth helps to maximize the mouth opening and keep it constant, with relatively little straining on the musculature. Do not forget to apply Vaseline or petroleum jelly at the corners of the mouth to get more out of the bite block.

2. Less is more. If the head of the handpiece or endodontic instrument finds little space against a taut masseter, it is beneficial to ask the patient to close the mouth slightly. Along with better access, it also provides intermittent rest to the muscles.

3. Short appointments. We do not want to fatigue the patient's muscles so much that the next appointment becomes problematic. Patient comfort takes precedence over all benefits of single visit root canal treatment in cases of limited access.  

II. Improving access from the armamentarium.

1. Smaller head handpiece and burs. Specially designed air rotor handpieces for pedodontic patients come handy for third molar RCT's and other clinical situations of limited access. Similarly, a small round or inverted cone bur is most useful for initial access into the pulp chamber. Once the initial access has been made, the depth of the pulp chamber provides sufficient space to accomodate the length of a longer, safe-ended bur.

A safe end bur prevents furcal perforation when visibility during access opening is compromised. 

2. Reducing the length of instruments. I find this to be the most directly helpful approach in these circumstances. We all understand that with an ISO 2% taper instrument, cutting the instrument at its end by 1 mm raises its tip diameter by 2. So 2 mm removed from a #6 file has a tip diameter of 10 and 2.5 mm removed from a #10 file has a tip diameter of 15.

3. Non-conservative approach. While the emphasis on conservative access preparation is gaining acceptance in the profession, the clinical scenario being discussed here may be best against it. Not only is it not always possible to follow the standard rules of access cavity preparation in teeth with limited access, but when the handle of an endodontic instrument finds itself gasping for space for a straight line access, it is best to break the rules. The initial access itself does not necessarily have to be from the occlusal surface. Access may be gained from the buccal or lingual surfaces in some situations, and subsequently extended occlusally. However, such teeth should be taken up for root canal treatment only if the final restoration of the access cavity can be accomplished for a good coronal seal.

III. Improving visibility.

1. Better illumination. Illumination should be good for the root canal treatment of third molars or where visibility is an issue. Front surface mirrors are an excellent choice here. You may have your assistant provide additional illumination with a torch.

A front surface mirror with illumination

2. Use of a slow handpiece. A slow rotating or micromotor handpiece offers better visibility as continuous water spray is not an absolute necessity. After having obtained an initial dip into the pulp chamber with an air rotor handpiece, I use a slow rotating handpiece with frequent, intermittent water spray for better visibility as well as better tactile control of where I am drilling.

3. Indirect approach. When root canal treatment for any tooth is begun, the angulation of the root(s) must have been assessed prior to the application of the rubber dam. Once the angulations are clear, the endodontic instrument may be directed indirectly into the canal by holding its handle with a tweezer. This prevents the hand coming in the way of your line of sight to the mouth mirror or tooth.

IV. Preventing instrument aspiration. The discussion of RCT with limited access cannot be complete without emphasizing on the need for precautions to prevent instrument aspiration. This is because the instrument is not being held in the grip it is designed for and it is very close to the pharynx. Therefore, if a rubber dam is not being used, attaching a long floss to the files or reamers and use of a throat shield safeguards the endodontic procedure.

Additional Reading: Kandasamy, S., Rinchuse, D. and Rinchuse, D. (2009), The wisdom behind third molar extractions. Australian Dental Journal, 54: 284–292.

Bleeding from root canal: Am I 'over' or 'under'?

In a root canal with ongoing endodontic treatment, both over instrumentation and under instrumentation may be the cause of persistent oozing of blood. Finding out which side of the apical constriction you are on is critical to the success of root canal treatment as well as patient comfort.

• Firstly, confirm the working length using an electronic apex locator. If you have already violated the apical constriction leading to the bleeding canal, tactile sensation may not help. Radiograph will only be helpful if you are more than 2 mm short of the radiographic apex or anywhere beyond it - which is a wide range from the apical constriction.
• If you are not using or not getting a reliable reading from the apex locator, the working length has to be determined using radiograph and tactile sensation. Flare the canals coronally till the root canal curvature; and use successively larger K-files to the apical area till binding is obtained 1-2 mm short of the radiographic apex. You now know whether you were 'over' or 'under'.
• If you were over-instrumenting, you only need to create an apical stop with a larger diameter instrument. This will both help in stopping the bleeding as well as getting a good apical seal. While if the reason was under-instrumentation, you can now proceed to clean and shape the remaining apical root canal. 
• If the working length you re-determine is the same as before, it is most likely that the bleeding is occurring from pulp remnant. Studies have shown that to thoroughly clean the apical root canal, you need to go at least 4 sizes larger than the initial apical file. Moreover, the root canal anatomy is more ovoid or elliptical than circular - the shape of an endodontic instrument; allowing pulp remnants along the root canal walls as well. Insert a barbed broach all the way to the working length, rotate it clockwise and pull it out. Then use H-file of the last apical size in circumferential filing motion to disengage any remnant still adhering to the root canal walls and irrigate copiously. 

SEM micrographs of the first K-files to bind at the root canal apex showing wide discrepancy between apical foramen and file size (Relationship between files that bind at the apical foramen and foramen openings in maxillary central incisors - a SEM study; Ronaldo et al. Braz Dent J; vol 22:6)

• The type of bleeding is also a good indicator of the source. Fresh, thin bleed is more likely to come from periapical trauma while oozing, dark bleed is more likely to originate from pulp remnants. 
• If the bleeding still persists, it is best to forego any further instrumentation. Dry the canals using paper points. Generally, if the bleeding is periapical it will dry out with the paper points while if there is a pulp remnant, the paper points will continue to absorb the bleed. 
• In such cases, it is always better to schedule a second sitting for completing the cleaning and shaping rather than a single sitting root canal treatment. Place a proper intracanal medicament along with a good coronal seal and prescribe a suitable non steroidal analgesic for any pain likely to result from over instrumentation. 

Additional Reading: The morphology of the apical foramen in posterior teeth in a North Indian population. Arora, Tiwari. IEJ,42, 930-939,2009. 

How to locate root canals in bleeding pulp chamber

Hyperemic pulps pose a challenge to the treating dentist at the first two stages of root canal treatment - anesthesia and access. While I have already discussed local anesthesia for acute irreversible pulpitis, locating root canal orifices with a bleeding pulp chamber requires extra time and attention of the dentist. 

• Know the proper access cavity preparation for the tooth you are treating. The proper shape and location of the access cavity will encompass all orifices of the root canals. Initially, there is no other way to know if you have uncovered the root canal orifice or no. 

Root Canal Access Cavity Preparations - Location and Shapes

• Flare the walls of the access cavity sufficiently. I find this to be the most helpful step. Flaring the walls of the access cavity helps in three ways. Firstly, it allows access to the root canals whose orifices have been uncovered. Many times, walls converging occlusally prevent the endodontic instrument from reaching the corner of the pulp chamber floor where the orifice is located. Secondly, it removes the bleeding pulp horns or attached tissue in the pulp chamber hindering our view. Thirdly, it facilitates removal of pulp stones which partially occlude the root canal orifice preventing complete pulp extirpation from the root canals.
• Extirpate pulp from the largest canal first using a broach. Locating the largest canal (distal for mandibular molars and palatal for maxillary molars) is the easiest with any endodontic instrument. The broach is the best instrument to be used here, how it should be used though, is debatable. While most endodontic texts recommend using the broach only up to the middle third of the canal to prevent instrument fracture, Richard Ten Cate in his dental histology text recommends using a broach apically as "The greatest concentration of collagen ....in the most apical portion of the pulp....affords a better opportunity to remove the tissue intact than does engaging the broach more coronally". In the clinical situation being discussed here, I take the broach as apically as I can because the broach is unlikely to bind and fracture in the straight and wide canals I am utilizing it for. 
• "You can never irrigate more". This advice from Dr. Stephen Cohen has stayed with me over the years and has proved immensely helpful. For those using sodium hypochlorite as the irrigant, it will help dissolve the pulp and aid more rapid and thorough debridement of the hyperemic root canal. For those using any other irrigant also, irrigation debrides the canal and provides a clearer field of view. The best time to peek into the pulp chamber to locate additional bleeding canals is immediately after irrigation of the located canals and pulp chamber. 
• Smaller root canals (mesial in mandibular molars and buccal in maxillary molars) can now be attempted using smaller files in their textbook locations. A #10 file best provides smallest tip with sufficient rigidity to canvass the pulp chamber floor without bending; but a #15 file usually suffices. 
• Extending the access cavity. If you have been unable to locate the bleeding root canals still, you might consider extending the access cavity minimally, and repeating flaring, irrigation and using smaller files.
• Thoroughly prepare the root canals found. Do not fret to locate all root canals before cleaning and shaping is begun. There is a subtle time when letting go precedes giving up. Determine the working length of the root canal(s) found, clean and shape them thoroughly and then re-attempt locating your other canals. If all else has failed, this is the road to success. You are in better control of the situation, there is no bleeding from the root canals prepared, you are better aware of the access cavity and you have given the hyperemic root canal more time for bleeding to arrest.
• Control the bleeding. A cotton pellet dipped in hypochlorite, local anesthetic solution containing epinephrine, a hemostatic agent or even normal saline may be tightly packed to the pulp chamber floor for a couple of minutes to arrest the bleeding and aid visualization. 
• Locating canals with rotary instruments. A rotary nickel titanium instrument with a non-cutting, fine tip but sufficient rigidity, such as Protaper S1 or SX (Dentsply Maillefer) also sometimes helps "catch" the root canal orifice when it eludes everything else. 

Additional Reading: Ingle's Endodontics 6. John I. Ingle, Leif K. Bakland, J. Craig Baumgartner. 6th ed. BC Decker Inc, 2008. (Pages 881-916)

Remnant pulp tissue in second root canal sitting

Very often, when a canal is reopened in the second sitting of root canal treatment for cleaning or obturation; remnant pulp tissue in the apical part of root canal becomes a problem. The patient experiences pain when the instrument is taken to the full working length, sometimes accompanied by minor bleeding as well. The question then becomes whether to keep the instrumentation and obturation short to the point of patient comfort or administer local anesthetic and continue instrumentation.
  Short instrumentation, though not advocated, is common. It is frequently justified as "partial pulpectomy". And I cannot deny the merits completely - clinical results are good and patient comfort wins you his trust. However, as a young endodontist, I cannot vouch for its long term results.
  I usually use a broach to the full working length in such situations to try and remove the apical tissue tag in one go. My canal has already been prepared and I am aware of the canal anatomy to safely use a broach here. In most cases this suffices to solve the problem of remnant apical pulp tissue in the root canal.

  Where it doesn't, I prefer to administer local anesthetic and clean and shape the canal again to the full working length. I will use the local anesthetic without even trying to remove the apical pulp tag with a broach in some cases. Such cases are when the patient experiences pain in the middle third of the root itself, or when I encounter patient reaction in more than one canal in the same tooth. Another consideration is that the larger canals are usually more difficult to tackle successfully with a broach.
  The only practical problem with this approach is that usually you have not scheduled the patient for a longer sitting, and the sitting becomes longer also because you have discovered the need for anesthesia after having opened the canals and removed the inter-appointment dressings. But then, the endodontic adage - what is taken out first is more important than what is put in later- holds true here also. The seconds and minutes of time taken out from your tight schedule for a good root canal treatment, are more important than the time put in for your next appointment. 

Additional reading: Do procedural errors cause endodontic treatment failure? 

LOUIS M. LIN, 

PAUL A. ROSENBERG, 

and JARSHEN LIN. 

JADA February 2005 136(2): 187-193

"Hot tooth": How to keep cool

More than the fear patients carry for root canal, I think we as dentists have for acute irreversible pulpitis. We have all been there - when the patient is in dire need of an emergency pulpectomy, we are struggling to take him up between our regular appointments, and the anesthesia just won't work.

 Here is how to keep your cool when the tooth has gone "hot":

• Administer the local anesthetic distal to the area of inflammation - supraperiosteal infiltration for maxillary teeth and regional nerve block for mandibular teeth. By injecting distal to the tooth, we are depositing away from the area of inflammation and closer to the nerve trunk. 
• Deposit a greater amount of the anesthetic to provide a greater number of uncharged base molecules. For both maxillary buccal infiltration and mental block, I usually deposit 1.5 ml (recommended is 0.6 ml); for palatal infiltration 0.4 ml (recommended 0.2 ml); and, for inferior alveolar nerve block 2.2 ml (recommended 1.5 ml). For the maxillary molars, deposit 1 ml each over the two buccal roots separately, followed by 0.4 ml of palatal infiltration. Supplement the inferior alveolar nerve block with supraperiosteal infiltration. 
• For maxillary infiltration, I deposit some amount not as supraperiosteal but rather directly over the bone. (Even though there is no recommendation in the literature for the same, what I am aiming for is the effect of an intraosseous injection). This needs to be done very slowly like a palatal injection, allowing time for the anesthetic to diffuse from the area before depositing more. 
• Pulpal anesthesia sets in after soft tissue anesthesia. Therefore, it is a good practice to wait a little more after the subjective signs of anesthesia are realized before initiating the access cavity preparation. 
• Even in the most acute of cases, this protocol allows me to reach till the dental pulp; when now, if still needed, I administer the intrapulpal injection. "If needed" here must not be taken to mean "when the patient complains of pain". The effectiveness of intrapulpal injection lies in pressure, obtained by binding of the needle in the pulp chamber opening. Therefore, one must keep in mind for all cases of acute pulpitis to intentionally check for pain by probing as soon as a dip is made into the pulp chamber. Even mild sensation at this point warrants an intrapulpal injection before the opening is enlarged any further. If binding is not obtained, however, the intrapulpal may still be administered into the canals individually. 
• So, what if the patient still experiences pain when an endodontic instrument is inserted into the root canal?

• Theoretically, the best option here is either a periodontal ligament injection or an intraosseous injection. The documented cardiovascular effects of the intraosseous technique as well as the requirement of additional armamentarium have kept me from using this. I have not found much additional success with the periodontal ligament injection as well. Having been satisfactorily following the protocol I am sharing in this blog for quite a while now, I do not try the periodontal ligament injection anymore. I invite comments from readers experienced in these techniques.
• At this point, one can either repeat the initial injection (infiltration or block for maxillary and block for mandibular); or go with the intraseptal. I use both depending on my clinical judjement. For example, if I had got a positive aspiration in my first inferior alveolar attempt, I will now go for intraseptal to avoid any trismus from repeated injection in the area. If, on the other hand, I am not certain of the subjective signs and symptoms confirming my first injection, I will repeat the first injection. In general, I have found some soreness persists in the area of intraseptal injection after the effect of the anesthetic has worn away and so I use it only as the last resort. 
• As the famous English writer Rudyard Kipling said - "Words are the most powerful drug used by mankind". Keep talking and comforting the patient. Do not ignore his pain, because it is real; but explain the reason why the anesthetic is not working. You may demonstrate the objective signs of the anesthesia to convince the patient that it has been aptly administered. 
• Many dentists prefer to do a partial pulpectomy followed by a formocresol dressing in such cases, to help the patient tide over the acute dental emergency till the next time when the anesthetic is likely to be more effective. I am myself not in much favor of this technique for two reasons - firstly, the pain relief afforded by complete pulpectomy is much superior to only draining the hyperemic pulp, and secondly, formocresol itself has become a subject of scientific debate. However, for those constrained by time due to the unscheduled nature of an emergency dental procedure, Weine recommends performing a formocresol pulpotomy or pulpectomy only for the largest canal - palatal in maxillary molars and distal in mandibular molars. 

Additional reading: Local Anesthesia Strategies for the Patient With a “Hot” Tooth. Nusstein, John M. et al. Dental Clinics , Volume 54 , Issue 2 , 237 - 247