Young Bui, D.D.S.
The Extra Roots or Canals That Make the Difference
Young Bui

Young Bui

WHEN ONE PERFORMS a root canal treatment, he or she should keep an open mind or eye out for the extra roots or canals that may exist in that particular tooth.  The percentage of extra roots or canals, besides the MB2, is low, but they do exist.  The success of the treatment depends on finding these canals and cleaning them out. 
     The first and most important step is to take a good x-ray.  The x-ray should be dark enough to give good contrast so that you can make out the PDL outline of extra roots or concavity.  If you look at a premolar and you see a wide, uninterrupted canal going all the way down to the apex, more than likely that tooth has only one root and canal.  If you see a concavity outline along the length of the root or if the pulp canal disappears half way down the root, you should look for more than one canal.  Take a mesially or distally angulated x-ray to try to split the roots to help you with your diagnosis.  Some upper premolars have three separate roots (Figures 1 and 2) or two roots with three canals (Figure 3).
Figure 1
Figure 2
FIGURES 1 and  2: Some upper premolars have three separate roots.

Figure 3
FIGURE 3: Some upper premolars have two roots with three canals.

    In these cases, the buccal root normally has two canals.  The kicker is that there is only one canal orifice that splits into two canals, making you think that there is only one buccal canal.  The clue to help you determine whether there is one canal or two is the angulation of the reamer handle once it is inserted into the canal.  If the reamer is straight up and down against the buccal cusp, then there is only one canal.  If it leans to the mesial or distal, then there are two canals. 
     In the lower premolars, you will find it much harder to determine how many canals there are.  Concavity and PDL outline will help you to a certain extent.  If the root makes you see double vision, then there is more than one canal.  Lower premolars normally have between one and two canals (Figures 4 and 5). 

Figure 4
Figure 5
FIGURES 4 and 5: Lower premolars normally have between one and two canals.

In rare cases there will be three (Figure 6) and four canals (Figure 7).  These cases are hard to fill because they sometimes have one or two orifices that split into two or three canals.  I guess whoever gets these cases is just unlucky.

Figure 6
Figure 7
FIGURE 6: In rare cases lower premolars will have three canals.
FIGURE 7: Lower premolars may even have four canals.
     An MB2 on an upper molar is not considered an extra canal because it is present about 80 percent of the time, more often than a second distal canal in a lower molar.  You just have to assume that it is there and look for it.  A second disto-buccal or palatal canal is rare, but they do occur.  I have never seen a DB2 with a separate apex, but I have seen them joined.  I have seen upper molars with separate palatal roots (Figure 8) and those with two canals that joined together (Figure 9).

Figure 8
Figure 9
FIGURE 8: Rarely, upper molars may have separate palatal roots.
FIGURE 9: Upper molars may in rare cases have two canals that join.

     Lower molars rarely have a third distal canal.  I have seen only one case like that.  The mesial roots, however, tend to have a third canal about 50 to 60 percent of the time.  Most of the time the third canal joins one of the other two canals.  I have had two cases that had three separate mesial canals (Figure 10).

Figure 10
FIGURE 10: Showing a lower molar with three separate mesial canals.

     It is imperative that all the canals are located and instrumented for a successful treatment.  Most of the failures in upper molars result from not instrumenting the MB2, which to me is not even an extra canal due to its high occurrence.  Take good x-rays for better diagnosis and hope that the tooth is a straightforward one.
September - October 2007



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