Many studies have revealed that the second mesio-buccal canal or MB2 is a frequent finding in the Maxillary molars, with the incidence reaching to more than 60 % in the 1st Molars and more than 35 % in the 2nd Molars .
As clinicians , we notice quite a number of unsuccessful endodontic treatments in maxillary molars attributed to a missed MB2 Canal, and surprisingly these numbers are quite high.
But what leads to missing out these MB2 canals while the other 3 are mostly easily located? Well this is usually due to diffuse calcifications , anatomic variations , pulp stones asoociated with this canal , while in retreatment cases the access to the MB2 may be totally blocked out due to obturation materials and or sealers and mostly by dentinal debris in addition to the previously mentioned reasons .
Magnification and MB2
To locate the orifice of the MB2 , the clinician needs to make a serious attempt to find one during the treatment and this sometimes involves long clinical time . In addition some form of magnification either by loupes or an operating microscope when routinely employed goes a long way in ensuring the success rate of such a procedure .
As per a study the use of some form of magnification leads to a MB2 detection rate approximately three times than not using any magnification for the same .( J Endod. 2002 Apr;28(4):324-7.Effect of magnification on locating the MB2 canal in maxillary molars.Buhrley LJ, Barrows MJ, BeGole EA, Wenckus CS.Department of Endodontics, University of Illinois at Chicago, USA.)
Ultrasonic Instruments and MB2
With use of Magnification coupled with ultrasonic instrumentation especially designed for Micro-endodontic use , one can delicately remove tooth structure to aid in the location of these canals, simultaneously minimising the risk of any iatrogenic perforations.
Certain criteria can aid in the location of the MB2 canal as have been outlined with the photographs of one of our such cases. This case is of an endodontic retreatment that we performed on a maxillary 1st molar . Even though at initial visualization it seems that no additional canal is present, further exploration of the pulpal floor and removal of dentinal shelf along the MB1-Palatal canal with ultrasonic micro-endodontic tips, reveals the orifice of the MB2 canal .
- Removal of the dentinal shelf beginning from the orifice of the MB canal, moving towards the palatal canal orifice .This is preferably done with micro endodontic ultrasonic instruments ( Presently we use the Endosuccess Kit from Satelec/Acteon ,the tip being used here is the ET18 D tip).
2.Removal of this dentin shelf gradually reveals a developmental groove/isthmus emanating from the MB canal
3.A Firm probing is required at this stage along this isthmus or groove to remove any debris or overlying thin dentin .
4.At all stages use copious irrigation to remove all debris generated by ultrasonic and probing , as any blockage by this debris will impair all the efforts to detect the additional canals .
5. Once located the canal orifice needs to be confirmed with the smaller standard hand file like #06 or #08 , and its presence and length should be confirmed before any cleaning and shaping procedures are initiated on this canal system .
** This video is of the same procedure being performed.
Today we know that one of the major causes for unsuccessful endodontic treatments are missed canals . Hence it is prudent to spend some time searching for them during every endodontic treatment and retreatment case .With a plethora of options available that aid us ranging from , the enhancement of visualisation of the operative field to precision reduction of the tooth material , the probability to locate these additional canal systems becomes higher .
But besides having all these aids at our disposal it requires perseverance and commitment along with the knowledge of the anatomical variations to make such endeavours successful .
Dr.Varun Malhotra .