7- NGU cleaning and shaping_5d8c606a5bf25e07edeeba5297d3d09b.pdf

Cleaning And Shaping Of Root Canal System BDS8129 Date : xx / xx / xxxx Aims: The educational aims of this lecture are to explain the methods of root canal cleaning and shaping. Objectives: On completion of this lecture, the student should have an understanding of how to perform different shapin...

Cleaning And Shaping Of Root Canal System BDS8129 Date : xx / xx / xxxx Aims: The educational aims of this lecture are to explain the methods of root canal cleaning and shaping. Objectives: On completion of this lecture, the student should have an understanding of how to perform different shaping methods of the root canal system Instrumentation Techniques Shaping is achieved through instrumentation of the canal, either: (A) From apical to coronal. MODIFICATION (B) From coronal to apical. MODIFICATION (C) Combination ( Hybrid). I- Apical Coronal Technique 1) Standarized technique: Initial file + 3-4 successive files (master apical file) to the full working length to create an apical stop . Motion: Circumferential filing 2) Step back technique (Telescopic preparation) Patency File: Definition: It is a small K-file (#10 or #15) that is passed through the apical foramen without binding or enlarging to check patency of the canal. It can also be used to: 1- Remove accumulated debris and help maintain the working length. 2- It is used to prevent apical blockage and so in turn decreases the chances of ledges and transportation 1 2 Initial Apical file Selection Apical Preparation (Phase I) Full working length 3-4 successive sizes (K type file) Full working length (FWL) Binding (K type file) #25 FWL(IAF) #30 FWL #35 FWL #40 FWL Master Apical File MAF 30-60° in #40 #25 Minimum MAF #35 Initial Apical file IAF (e.g. #25) Watch-winding motion 3 Stepping back (middle & coronal part) (Phase II) 4 Step back coronally at 1mm Increments & one larger file size (about 3-5 successive sizes) 40 20 mm FWL 19 WL-1 mm 18 WL-2 mm 17 WL-3 mm 16 15 WL-4 mm Gates Glidden drills WL-5 mm Recapitulation Refining (Phase III) Modified Step Back Leave 2-3 mm before making the first step in stepping back phase to leave what is known as retention form with a circular cross section Advantages of step back: 1- Shaping apical 1/3 with small flexible files while larger stiffer files are away from apex. 2- Maintain a proper resistance form. 3- Create spaces for multiple cones . Disadvantages of step back: 1-Minimal effect of irrigation at initial stages of the technique 2- High stresses applied on the file. 3-Tendency for canal deviation. • • • • 3-4 FILES TO MAF 3-4 FILES TO STEP 3-4 FILES TO FLARE 3-4 RECAPITULATIONS II- Coronal Apical Technique Advantages of crown-down technique: 1-Elimination of most microbes and infected dentin. 2-Better and deeper penetration of irrigant. 3-Instrument approach apical 1/3 with less strain. 4-Provides more tactile sense in the apical 1/3. 5-Less extruded debris decreasing postoperative pain and flare ups. 6-Less time for preparation. 1) Crown – down pressureless technique: • Phase I: Coronal flaring • Phase II: Body of the canal Waves of instrumentation. • Phase III: Apical portion of the canal THE CROWN- DOWN APPROACH The coronal preflaring can be achieved by: 1-Hedstroem or K-type files. 2-Gates–Glidden drills . 3- Nickel–titanium orifice openers III-Hybrid Preparation ( Step back Step down) ( Modified Double Flared) • Phase I: Coronal flaring (Gates Glidden drills #3,2) • Phase II: Apical portion of the canal (IAFMAF) • Phase III: Body of the canal (2-3 successive files after MAF) The mechanical preparation of the radicular access is divided into four phases: 1- Preparation of coronal flare to the beginning of the first canal curve or to twothirds the estimated length of the canal if the canal is straight 2- Determination of canal length to apical terminus by negotiation of small instruments (ISO size 08, 10) to full length with precise length establishment as previously described 3- Negotiation and enlargement of the canal to the accurately confirmed length using hand instruments in a rotational mode of manipulation, preferably a gentle watchwinding technique to at least ISO size 35 4- Final shaping to achieve a regular taper. Instrumentation Of Curved Canals 1- Precurving of the instruments. 2- Flaring of the coronal 1/3 before initiating cleaning and shaping. 3- Use copious irrigation. 4- Never skip file sizes. 5-Never force files inside the root canal. 6- Using flexible instruments. Balanced Force motion: – When the file reach desired length, Dentist rotate the file in a counter clockwise while applying apical pressure on the file – This counter clockwise rotation with the apical pressure prevent outward movement of the file from root canal while flutes cut in the dentin. – The balance between counter clockwise rotation & the apical pressure keep the file centralized in the canal & minimize the chance for canal transportation. – Then Clockwise turn is made to load debris on the file and pull it away. – Flex-R file (modified k-file ) is suitable for this motion due to its triangular cross section & non cutting tip. Anti-curvature filling: • Pushing the file handle in anticurved direction , so pressure is applied to the outside wall, away from the dangerous zone Power- Assissted Root Canal Instrumentation 1- Low Speed Rotary Instruments: • A. Gates-Glidden (GG) burs: { side cutting with safety tip} • Widening the orifices & flaring of the coronal &mid 2/3. • B. Peeso Reamers. Post space preparation SIZE 1-6 corresponding 50 – 150 ISO Conventional low speed hand piece 20,000-40,000 rpm (Full rotation 360 degree) 2- Engine driven reciprocating Instruments: It has a 30 degree reciprocating motion at 1500 rpm Safe sider Automated Hand Pieces Racer Vertical stroke 0.3-1 mm Canal Finder Both 3- Engine Driven: Vibratory Sonic less than 20 KHz (air powered, water irrigant) Rispi Shaper Triocut Ultra Sonic 20 – 50 KHz (ElectricNaOCL irrigant) Ultra Sonic irrigation (acoustic streaming= eddy flow)rather than preparation When a file is energized in a canal flooded with irrigant, the fluid shows a wave motion and bubbling action this helps in: Loosening debris Better flushing of the canal It is good in cleaning but poor in shaping Acoustic Streaming: Movement of irrigant around a vibrartory file in a vortex like motion Nickel Titanium Endodontic Instruments The unique properties of NiTi alloy have allowed instruments to be manufactured for use in a rotary handpiece and these have been shown to be effective in canal preparation. • Advantages of Rotary NiTi: 1- Physically effortless. 2- Canal enlarged quickly. 3-Debris removed easily. 4- Canals are more uniform & smoother. 5-Requires less time for preparation & fewer instruments. Disadvantages of Rotary NiTi: 1- Lack of tactile sensation which is partially solved by the smart motors. 2- Used for a limited number of times according to manufacturer instructions. 3- They fracture more easily without any signs of permanent deformation. 4-They are more expensive than stainless steel instruments. Different designs of NiTi rotary instruments for canal preparation 5 Generations Guidelines for using rotary NiTi instruments: 1. Access preparation  Straight line access 2. Don’t force files  NiTi rotaries require a passive technique 3. Difficult canal anatomy should be detected & analyzed 4. Don’t overuse files 5. Don’t try to bypass ledges MULTIPLE & PROGRESSIVE TAPER ProTaper Universal Shaping Files S2 S1 S2 20 Sx ProTaper Universal Finishing Files (Variable Decreasing Taper) F1 3mm 20-7% F2 F3 25-8% 30-9% F4 F5 40-6% 50-5% Rotary Protaper Shaping files SX S1 S2 Finishing Files (F1, F2, F3, F4, F5) PROTAPER UNIVERSAL Shape the Apical part of the canal ProTaper® Universal Protocol Procedural Errors Difficulties often occur when the dentist must prepare small, curved canals. Large sized root canal instrument straightens within the canal, resulting in undesirable changes of the canal shape. 1-Under extended access cavity preparation leading to a missed canal. 2- Perforations: a- Strip perforation. b-Lateral perforation. c- Apical perforation. 1- Strip Perforation: 2-Lateral perforation: • 1- Supra- crestal • 2-Crestal. • 3- Sub-crestal 3- Apical Perforation 3-Ledge Formation: • Detection : 1. When the instrument can no longer be inserted to the full working length 2.Instrument tip hits against a solid wall with no tactile sensation of binding 3.Radiograph shows inability of the inserted instrument to reach full working length Causes: 1.Failure to make a proper access cavity (underextended access cavity preparation or inadequate convenience form). 2.Failure to make coronal preflare that allow direct access to the apical portion of the canal. 3.Using a straight or too large instruments in a curved canal 4- Canal Blockage: Blockage is obstruction in a previously patent canal that prevents access to the apical constriction. Causes : 1)Dentine shavings compacted into a hardened mass. 2)Packing of pulp tissue ( vital ) to form collagen plug .( fibrous blockage) 3)No irrigation during preparation. 4)Cotton pellets , restorative materials and fractured instruments also cause blockage. Detection: We cannot reach W.L. Correction: 1) Recapitulation using copious irrigation. 2) Blockage occurred at the level of the canal curvature, pre-curving is indicated. Prognosis: If it can not be corrected  If early, before cleaning & shaping  Affects prognosis. If it can not be corrected  If after cleaning & shaping  better prognosis. prevention: - Copious irrigation - Use of patency files . 62 5- Instrument separation: 1- Under-extended access cavity. 2. Using “stressed” instruments. 3.Excessive rotation of the instrument in a canal after binding. 4. Placing exaggerated bends on instruments in curved canals. 5. Forcing a file down a canal. 6. Manufacturing defects. Surgical intervention Fragment Extends Past The Apex Prevention: 1- Examining the instrument for signs of stress before use. 2- Small instruments used to negotiate small difficult and curved canals should be discarded. 3- Discarding of rotary instruments should follow the manufacturer instructions. 6-Transportation: Aims: The educational aims of this lecture are to explain the methods of root canal cleaning and shaping. Objectives: On completion of this lecture, the student should have an understanding of how to perform different shaping methods of the root canal system Reading material: -The dental reference manual, Geraldine M. Weinstein, springer 2017 (Chapter 12) -Essential skills for dentists, Peter A.Mossey et al, Oxford, 2006 (Chapter 2.6) -Endodontics, Kishor Gulabivala and Yuan-Ling NG, Mosby Elsevier 2014 -Harty`s endodontics in clinical practice, Bun San Chong, Elsevier 2017 -Clinical endodontics, Lief Tronstad, Thieme 2009 (main reference) Thank you Date : xx / xx / xxxx