Canal markings produced by endosonic instruments Walmsley AD, Murgel C, Krell KV. Canal markings procduced by endosonic instruments. Endod Dent Traumatol 1991; 7: 84-89. Abstract - It has been recognised that ultrasonic files leave a diagonal pattern within the canal following endosonic instru- mentation. There is confusion on the causative factor on the production of these marks. Furthermore there is little infor- mation about the marks produced by sonic files. An in vitro system consisting of highly polished dentin discs demonstrated that the ultrasonic K-file made a diagonal pattern that was an imprint of the cutting edges of the file. The sonic files produced different markings which were the result of their longitudinal and trans- verse motion. Root canals of extracted teeth were prepared with these instruments and similar grooves were observed. The ultrasonic K-file had diagonal grooves in the coronal and middle third of the root canal but longitudinal marks in the apical third. The rispisonic and shaper files produced debris even in the pres- ence of NaOCl. This debris was formed into discrete parallel bands. Both longitudinal and transverse grooves were present and the canal had many other scratches similar to those seen with the dentin discs. There were differences between the marks pro- duced by either ultrasonic or sonic endosonic instruments but it is unknown whether this infiuences the long term prognosis of the root canal therapy. A. D. Walmsley'', C. Murger ^ K. V. Kreir Departments of En(jodontics, University of iowa Coilege of Dentistry, University of iowa, U.S.A., ^Re- storative Dentistry, The Dental Schooi, St. ChaiJ's Queensway, Birmingham, England, ^University Cami- lo Castelo Bianco, Sao Pauio, Brazil. Key words: ultrasonic instrumentation; root canal instrumentation. A. D Walmsley, Department of Restorative Den- tistry, The Dental School, St. Chad's Queensway, Birmingham, B4 6NN. England. Accepted for publication September 22, 1990. A consistent fmding within canals which have been subjected to endosonic instrumentation is the pres- ence of repeating bands or markings in the dentin surface. These initially were reported by Cymerman (1) and likened to a diagonal wave pattern although no explanation for their occurrence was reported. Ahmad et al. (2) also noted these markings that occurred after use of an ultrasonic K-file and found that on the elevated parts of these wave patterns there was often little or no debris with no smear layer. It was argued that these marks, which were at an angle to the length of the canal, were not caused by the file but by acoustic streaming forces. This may be a result of the combined effect of the turbulence created by the fiow of irrigant together with the abrasive action of loose dentin fragments removed from the canal wall. It is now recognised that these patterns are due to the action of the K-file fiutes as the distance between the crests produced in the dentin and the cutting edges are similar (3). This regular repeating pattern has been noticed by other investigators when assessing the cleanliness 84 of canals prepared by ultrasonics (4,5) but are not a feature of those canals which have been prepared with sonic instruments (6,7). When these instru- ments are used then the markings consist of either regular bands (6) or longitudinal parallel grooves (7). Although these grooves are produced by both sonic or ultrasonic devices, it is a clinical feature that the canal will often feel smooth following instru- mentation. Previous investigators have often reported these features although as such they have not warranted much attention. Such imprints may be important in interpreting the cleanliness of canals following instrumentation and their presence may be informa- tive about the shaping process of different files. They indicate how the cutting edges of the file may work within the canal and provide an insight into the amount of debris that may be produced by the cutting action of the different files. The aim of this study was to use an in vitro system to identify the markings produced by the types of files fabricated for different commercially available