December 2006 – Appropriately Sized Preparations for the Tooth
This 55 Year old male presented with a history of conservative occlusal amalgam restoration and distal marginal ridge crack.
Symptoms included elevated thermal sensitivity (cold) and sensitivity to chewing upon release. Facets were visible and the patient claimed to have a history of night grinding. A diagnosis of .cracked tooth with irreversible pulpitis was made and endodontic treatment was suggested,
Preoperative examination of the roots revealed very slender root anatomy. Upon access of the tooth, 4 clearly defined orifices were visible. Working length instruments established 3 canals with 4 separate foramina. At this point a conscious decision must be made as to exactly how much to enlarge the canal space and what level of preparation is required. While we can not presuppose apical foramen sizes, it is prudent to assess the root thickness to prevent over-enlargement of the canals and minimize chances of strip perforation.
In this case less Gates Glidden preparation was used and canals were initially worked with file to size #15 and then hand driven K reamers to size 20 and then 25 short of the WL. From there ProTaper S1 and S2 files were used but only coronally. SX files were used only at the orifice level.
Canals were shaped incrementally and slowly.
Canals were shaped with a combination of classic Envelope of Motion ( Hand reamers) with final use of an F1 only as far as it would passively go – short of the terminus. Patency was constantly checked with #15 file. Obturation was performed using classic vertical compaction of warm gutta percha and F1 ProTaper cones that had been “cod rolled” down slightly on a glass slab in order to decrease their taper.
The final image showed 4 canals shaped to an appropriate size for the root. The canals maintained the flow of the external root surfaces while at the same time not exhibiting too much parallelism. The coronal aspect of the mesial canals showed “limited purposeful straightening” (as Schilder referred to it) while at the same time respecting the thinness of the dentin.
Clinicians must resist the “ cookbook” style of canal preparation that is advocated by many instrument dealers and salesmen. Each case is different and there is no one universal instrumentation or obturation system that allows us to treat “by the numbers”. Close preoperative examination of the tooth will allow the clinician to make modifications and decisions as to how best to handle the particular anatomy. In this case, canals were prepared in a more conservative fashion than normal while still maintaining adherence to sound treatment principles.