Aim To present guidelines on GT file selection, and safe operation. Summary It is not necessary to remove excessive dentine for effective root canal preparation. GT files allow safe, standardized preparation, and should be selected to fit the case in hand. Small Root canals Should be prepared with 0.06 and 0.08 taper GT files, whilst Large Root canals should be prepared with 0.10 GT or 0.12 Accessory GT files. The greatest challenge is un-learning habits acquired from traditional instrumentation methods. GT files should be used with light touch, and without up-down pumping motions. Spin speeds should be controlled below 300 r.p.m. for routine preparation. GT files are subject to fatigue and should be tracked to avoid overuse. It is recommended that GT files are discarded after the equivalent of five root canal preparations. For severe curvatures, GT files should be single-case tools. Key learning points The standard GT file set comprises three instruments of 0.06, 0.08 and 0.10 taper. All are size 20 at the tip, and have a maximum diameter of 1 mm. Accessory GT files have a standard taper 0.12, and maximum diameter of 1.5 mm. They are available in tip sizes 35, 50 and 70. Large Roots are lower canines, upper anteriors, upper and lower single-rooted premolars, palatal roots of upper molars and distal roots of lower molars. They should be prepared with 0.10 GT or 0.12 Accessory GT files. Small Roots are lower incisors, multirooted premolars, buccal roots of upper molars and mesial roots of lower molars. They should be prepared with 0.06 or 0.08 GT files. All GT files should be used with light force and at the correct spin speed. GT files should be discarded after the equivalent of five root canal uses.
