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.
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| 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.
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| 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.
