Various studies around the globe has reported that the most important factor the rotary instrument seperation was the operator. This is probably attributed to their clinical skills or their decision either to use instruments for a specific number of times or until defects were evident.
Successful endodontic motor treatment depends on a series of sequential procedures including shaping and cleaning of the root canal system. Biggest engima for an endodontist is the separation of rotary endodontic instruments .This negates the achievement of efficient bio mechanical preparation , which can result in under-filling of the root canal or the treated case may end in failure.
Preventive procedures related to breakage/ seperation are of utmost importance. Therefore an endodontist should have understanding of the mechanisms and factors contributing to file fracture is essential. It is very essential that both training and adequate skills are imperative for all dental procedures and particularly so in rotary endodontics.
The thumb rule for rotary endodontics as with other endodontic hand instruments is examination of the dental equipment, before and after use, to rule out any stress on the instrument/ stretch marks. Other important rule is that no rotary instruments should not be used in dry canals and or no instrument should be used without any lubrication. Further rotary files should be used according to the manufacturer’s instructions and excessive forces should be avoided. There is a variety of protocols for rotary root canal instrumentation.
Another important factor for rotary instrument seperation is the root canal morphology. More complicated the root canal morphology, the greater the risk of endodontic instrument breakage. A higher prevalence of rotary instrument separation has been reported in molars particularly in the mesial roots of mandibular molars.Further, the risk of instrument seperation in the apical third of the canal is higher when compared with coronal and middle thirds.Rotary files undergo greater fatigue as the curvature increases and the contact surface with the dentinal walls is greater since most curved canals are narrow. Clinically, fatigue of an instrument may be related to the degree of instrument flexure when placed in a curved root canal.
When the curvature of canals is pronounced, the cyclical fatigue of the instrument is greater and thus its life expectancy is lower.The parameters of the angle and the radius of curvature are independent in such a way that even if two canals have the same angle of curvature they may have different radii of curvature, which indicates that some curves are sharper than others.