The appearance of narrow canals and curvy roots on a pre-op periapical radiograph rightly alert us to the prospect of a tricky root canal treatment. Yet I would argue that the technical challenge posed by cases at the other end of the spectrum - those teeth with wide canals and straight roots shouldn’t be underestimated. At first glimpse it would seem that such cases ought to be simple cases since they are normally anterior teeth and there is usually little difficulty in negotiating the canals to full length but controlling for length during both the cleaning and filling stages can be especially difficult.
Cleaning
It is possible to clean the full canal system only once the canal length is determined. Electronic length determination (apex locator accuracy) is best when the canal is relatively dry and when there is snug contact between the file tip and the apical canal walls. With a wide canal this snugness of fit is lost which is why apex locator working length determination is less reliable in cases where the apical foramen is enlarged.
Since the 1980s we have known that on its own (without an antibacterial irrrigant), mechanical debridement of infected canal walls was insufficient to render them bacteria free. Perhaps unsuprisingly since micro-CT scans of extracted teeth show a significant proportion of canal surfaces remain uninstrumented after modern preparation techniques; the short coming most pronounced in wide canals where up to 50 per cent of the canal wall remains untouched by files.
Filling
Teeth with wide canals and straight roots lack the usual friction, taper and apical constriction normally afforded by the canal walls so that there is little to stop the extrusion of root-filling material through the apex during vertically compacted obturation. This is considered a challenge since not only are overfilled teeth associated with the lowest endodontic success rates but various sensitive anatomical structures are in harm’s way when endodontic procedures are not confined within the root canals.
Case study
The following case nicely shows a successful outcome in a case of wide canals and straight roots. The patient, a 20yr old female, was referred by her dentist for endodontic management of her LR7 which had been associated with a draining buccal sinus for the preceding month. Clinical examination revealed that the LR7 had a large distal class II amalgam restoration. A draining sinus was noted bucally to the tooth which was grade II mobile but not associated with significantly increased periodontal probing defects.
A sinus tracer radiograph tracked the source of the discharge to the root ends of LR7. The canals appeared wide and the roots were straight. Although a radiolucency was evident periapically; it was not confined to a discreet apical lesion; radiolucent bands were seen extending up the mesial and distal root surfaces. The restoration (which extended into the pulp chamber) had a marginal discrepancy, possibly secondary caries.
We reached and discussed a diagnosis of chronic apical periodontitis with suppuration LR7. In light of her overall sound periodontal state I felt that the mobility and periodontal destruction (as well as the periapical lesion) would resolve with successful management of the endodontic infection.
On removal of the defective restoration , the seal and appearance was improved with a Fuji IX glass ionomer cement restoration. Following rubber dam isolation, endodontic access yielded three canal orifices. The walls of the wide, straight canals were debrided lightly with metal files. Plenty of time was then dedicated to thorough irrigation of the canals with plentiful five per cent concentration sodium hypochlorite.
Conventional electronic length determination was likely to be difficult because of the canal size and so an estimate was made from the pre-operative radiograph. From this estimate, the true canal length was confirmed via the ‘paper-point technique’ whereby a large paper point is briefly inserted into a canal before removal and inspection of the tip. The working length is reflected in the distance from the coronal reference point to the location of the wet dry junction on the paper point.
After disinfection, Biodentine was mixed according to the manufacturers instructions. Small increments were placed into the pulp chamber with a flat plastic and then tamped down to full working length using a measured, large paper point. Once Biodentine filled the canal to orifice level, I packed a further increment of Fuji IX into the access cavity.
At the six month review the patient had no complaints. The sinus had resolved and the mobility had returned to that of her normal adjacent teeth. A periapical radiograph confirmed resolution of the radiolucency both apically and
periodontally. The merits of a cast restoration were reiterated.
Conclusions
Biodentine was the ideal material for canal obturation in this case from time saving and biological perspectives. In my hands there weren’t enough hours in the day or accessory GP points in the practice to have completed cold lateral condensation. I was concerned that any attempt at a warm vertical obturation would have resulted in significant extrusion – possibly compromising the nearby ID nerve.
The interface between the root filling material and the periapical tissues is normally small but when the apical foramen is considerably widened (as was the case here) a more biocompatible the filling material is desirable. The biocompatibility of Biodentine is second to none and the improved handling characteristics (12 minute setting time) made it the ideal choice.
References available on request.