Pre-clinical Endodontics I PDF

Pre-clinical Endodontics I Endodontic Instruments: Part 2 Dr Okba Mahmoud BDS, MFDS RCPS Glasg, PhD Ncle Eng (Endodontics) Associate Professor Consultant Endodontist 23th September College of Dentistry 2024 e-mail: o.mahmoud@aj...

Pre-clinical Endodontics I Endodontic Instruments: Part 2 Dr Okba Mahmoud BDS, MFDS RCPS Glasg, PhD Ncle Eng (Endodontics) Associate Professor Consultant Endodontist 23th September College of Dentistry 2024 e-mail: [email protected] Course Learning Outcomes: On the successful completion of this course the learner will be able to: Describe the instruments & dental materials used in Endodontics. Identify the morphology of the roots & pulpal space, access cavity outlines, working length determination methods and cleaning & shaping techniques. Discuss different radiographic techniques in endodontics and their interpretations. Apply the basic & fundamental endodontic procedures on Anterior & Premolar teeth, using clinical skills units. Hand instruments Hand instruments are grouped according to usage by the International Organization for Standardization (ISO), working alongside the American National Standards Institute (ANSI). These organizations have defined terminology, dimensions, physical properties, measuring systems and quality control of endodontic instruments and materials. Types Hand Rotary Hand instruments Parts of file Working area 16mm  Files  Measuring the length  Clean  Widen the canal and shape  Create space for root filling material Hand instruments For many years the standard cutting instruments have been: K-type file. Hedstroem file. Reamer These root canal preparation instruments have been manufactured to a size and type advised by the International Standards Organisation (ISO). For most standardized instruments the number refers to its diameter at the tip in one-hundredths of a millimetre. e.g. number 10, means that it has a tip diameter of 0.10 mm. All these instruments have a standard 2% taper over their working length. Standardization The development of worldwide standards for endodontic instruments and materials has occurred since the 1950s, when it was realized that a considerable amount of variation existed between root canal instruments of different manufacturers. At that time proposals for standardizing instruments were produced and covered the following: The diameter and taper of each instrument and filling point. The graduated increase in size from one instrument to the next. An instrument-numbering system based on the diameter of the instrument. Hand instruments Files: Design & colour governed by International Standards Organisation (ISO) D16 D0 Handle: numbered & coloured Shank: 16mm of blades & 0.02mm mm-1 taper (2% taper) Rubber stop: for length determination Handle colour ISO size Pink 06 Grey 08 ISO size gives tip Purple 10 diameter: White 15 45 90 10 = 0.10mm Yellow 20 50 100 Red 25 55 110 35 = 0.35mm Blue 30 60 120 110 = 1.1mm Green 35 70 130 Black 40 80 140 Made from Stainless steel or Nickel-Titanium Standardization These proposals have been widely accepted, and endodontic hand instruments (files, reamers and barbed broaches) are standardized in relation to size, color coding and physical properties. D0 represents the diameter of the projection of the working part at the tip end, and is its nominal size. D16 represents a point at 16 mm from D0 where the cutting part of the instrument ends and is 0.32 mm larger. The taper is a constant 0.02 mm per 1mm of cutting flute. The length of instruments ranges from 21mm to 31mm, with 25mm being the most commonly used. Standardization Intra Canal Instruments Materials of root canal instruments: Carbon steel: it is not used now because off its liability to corrosion. Stainless steel: it is more resistant to corrosion but it has limited flexibility. Nickel titanium: it is more flexible & is more adaptable to canal curves (3 times as flexible as stainless steel with very low modules of elasticity). Hand-Operated Instrument Two techniques for manufacturing hand instruments 1. Machined instruments: Grinding the instrument on a lathe. e.g. Hedstrom-type file. 2. Ground–Twisted instrument: Grinding a raw wire and then twisting it counter-clockwise. e.g. K type file and Reamers (both have a pyramidal tip).  Barbed broaches These are made from soft steel wire. The barbs are formed by cutting into the metal and forcing the cut portion away from the shaft, so that the tip of the barb points towards the handle. The cuts are made eccentrically around the shaft so that it’s not weakened excessively at any one point. It is designed for removal of pulp tissue, cotton pellets, absorbent points and other soft materials and NOT for canal enlargement Barbed Broach Showing the barbs pulled away from the instrument shaft Practical Notes Provided the instrument is loose within the canal and the barbed broaches is used to engage soft tissue only, the risk of fracture is minimal. However, as soon as the barbed broach is wedged against the wall of the canal, the barbs are flattened against the shaft. When an attempt is made to remove the instrument from the canal, the sharp barb tips dig into the canal wall and resist its withdrawal. Considerable force may be necessary to free the jammed instrument and there is a risk of either fracturing the shaft of the instrument or at least some of the individual delicate barbs. For this reason, the instrument should never be used to shape canal walls Instruments differ according to: Metal Taper (0.02) Tip design (K & H file) Cross sectional geometry Length of cutting blades Sizing Files must be: Sharp, to cut dentine Flexible, to negotiate curves Strong, to resist fracture 1. ISO K hand files Action: Rotation Watchwind Rasp Balanced force motion 2. ISO Hedstroem files Action: Rasping Cut on outward stroke Files There are various types of root canal file, and they are usually made from stainless steel. The followings are the main types: 1) K-file. 2) K-flex. 3) Flexofile. 4) Flex-R. 5) Hedstrom and Safety Hedstrom. 6) S-file. Files are predominantly used with a filing or rasping action, in which there is little or no rotation of the instrument in the root canal, except for the Flex-R instrument K-file This instrument is manufactured from stainless-steel wire which is ground into square cross-section. The blank is twisted into a tighter series of spirals than a reamer to produce from 0.9 to 1.9 cutting edges per millimeter length. When a K-file is manufactured from a triangular cross- section, it demonstrates superior flexibility, and as a result of it, decreased cutting efficiency, then is more likely to follow canal curvature than a file with a square cross- section.  Files Superior cutting efficiency Hedstrom file (H-file) Machining a steel blank The angle between the long-axis and the cutting blade is close to right angle, which is why preparation by Hedstroem files is effective ONLY when using a filing motion (up and down movement) Reamers Reamers are usually made from stainless steel by twisting tapered lengths of wire which have a triangular or square cross- section, to form an instrument with sharp cutting edges along the spiral. Although cross- section is a manufacturer’s prerogative (choice). Reamers are used to enlarge and shape an irregularly shaped root canal into a cavity of round cross- section. The basic actions is a half- turn twist and pull which shaves the canal, removing dentine chips from the root canal. The stiffness of an instrument increases with each larger size, so that larger reamers in curved canals will tend to cut a wider channel near the apical end of the root canal (apical zipping). Considerable damage may be caused to a root canal by the incorrect use of a reamer, and their routine use is no longer recommended. Reamers Triangular (large sizes ) Square (small sizes) K-Reamer and K-File & Hedstrom File Reading Materials: M. Torabinejad, A. Fouad & S. Shabahang (2021). Endodontics: Principles and Practice. 6th edition, Saunders, an imprint of Elsevier Inc., Philadelphia. Chapter 7 (page 117 – 136) Dr Okba Mahmoud  Email: [email protected]  WhatsApp: 00971504108718  Instagram: dr_okba Questions??