Root Canal Enlarging Instruments PDF

Root Canal Enlarging Instruments BDS8130 Date : xx / xx / xxxx Aims: The educational aims of this lecture are to detail different instruments available for root canal enlargement. Objectives: On completion of this lecture, the student should have an understanding of how to use different instrume...

Root Canal Enlarging Instruments BDS8130 Date : xx / xx / xxxx Aims: The educational aims of this lecture are to detail different instruments available for root canal enlargement. Objectives: On completion of this lecture, the student should have an understanding of how to use different instruments to enlarge root canals, their indications and advantages and disadvantages of each Power- Assissted Root Canal Instruments 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 3- Engine Driven: Vibratory Sonic less than 20 KHz (air powered, water irrigant) Rispi Shaper Triocut Ultra Sonic 20 – 50 KHz (Electric- NaOCL irrigant) Ultra Sonic irrigation (acoustic streaming= eddy flow)rather than preparation Acoustic Streaming • Disadvantages of engine driven instruments: 1- Loss of tactile sense. 2- Chance for canal blockage. 3- Chance for canal ledging 4- Chance for canal perforation. 5- Chance for instrument breakage Nickel Titanium Endodontic Instruments Manufactured from Nitinol alloy (55%Ni & 45%Ti) • Properties: 1- Super elastic property: ability to return to its original shape even if bent . severely External stresses Austenitic crystalline Martensitic crystalline On release of stress, the structure reverts back to austenitic phase recovering its original shape R- phase is an intermediate phase that can form during transformation from martensitic to austenitic and vice versa. 2- Hand files  Low cutting efficiency. 3- Rotary NiTi files are manufactured by Machine Grinding except for twisted file (TF). Gear Reduction Torque controlled (300-500 rpm) Rotary Ni Ti • 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 Engineering criteria: 1- Helical angle ( discussed before) 2- Pitch 3- Clearance space 4- Rake angle 5- Radial land • The flute of the file is the groove in the working surface used to collect soft tissue and dentine chips removed from the wall of the canal Depth of Flutes Deeper grooves [flutes] promotes more dentine chip removal capability The core is the cylindrical center part of the file having its circumference outlined and bordered by the depth of the flutes 1-Helical angle: The angle formed between the cutting edge & the long axis of the instrument. Steeper Helical angle Less steep Helical angle 2- Pitch: Distance from a point on a leading edge and the corresponding point on the adjacent leading edge The smaller the pitch the more spirals the file will have 3- Clearance Space: More Clearance Space Less Clearance space 4- Rake angle: Is the angle formed by the leading edge and the radius of the file if the file is sectioned perpendicular to its long axis. Positive rake angle results in cutting action. Negative rake angle results in scraping action. 5- Radial land A surface projecting from the central axis as far as the cutting edge a) Keeps instrument centered in the canal b) Supports the cutting edge Non Landed Design Landed Design Mode of failure of NiTi instruments: - They fracture more easily without any signs of permanent deformation: a) Torsional failure  instrument tip is locked in the canal while the motor continues to rotate. b) Fatigue failure  continuous rotation in a curved canal subjects the instrument to metal fatigue due to repeated loading Tensile loading on the outer curve and compressive loading on the inner curve Manufacturing Strategies To Improve Clinical Performance Of NiTi Instruments 1-Changing Design: -Multiple Changing Tapers over each file's Cutting Blades -Convex Triangular Cross Section -Progressively Changing Helical Angle and Pitch Constant vs Variable helical angle & pitch Constant Variable 1-Less amount of debris extruded in a coronal direction 1-More amount of debris extruded in a coronal direction 2-More debris accumulation inside the canal leading to: i) Decrease cutting efficiency (Clogged flutes) ii) Increased incidence of instrument separation 2-Less debris accumulation inside the canal leading to: i) Increase cutting efficiency (No clogging of the flutes) ii) Decreased incidence of instrument separation 3-More susceptible to “screwing in” phenomenon that "sucks -down" the instrument apically leading to instrument separation 3-Less susceptible to “screwing in” phenomenon that "sucks -down"  reduced incidence of separation Instrument Tip Design Round or Batt tip: • Serve as a guide within the canal without cutting. • Precisely follow the canal anatomy & minimize the risk of transportation , ledging and zipping of the canal. • Keep the file centered in the canal so preserve the natural canal path. • Reduce pushing the debris apically, thus decreasing patient’s postoperative pain. 2- Surface Treatment:  To eliminate surface defects  Improve resistance to cyclic fatigue  Improve cutting efficiency of endodontic instruments. Example : 1- Electropolishing. 2-Ion implantation. RaCe instrument 3- Changing Manufacturing Procedure: Twisted file , manufactured using a twisted method in R-phase. 4- Thermo mechanical treatment of NiTi: 1-M-Wire:(2007) -M-Wire, a new NiTi alloy produced using a proprietary thermal process. -They have greater flexibility and increased resistance to cyclic fatigue. Examples: -Wave one. -Protaper Next. WaveOne 2-CM - NiTi files:(2010) • Manufactured utilizing a unique process that controls the material’s memory, making the files extremely flexible but without the shape memory of other NiTi files. • This gives the file the ability to follow the anatomy of the canal very closely, reducing the risk of ledging, transportation, or perforation compared to other instruments with rebound effect. HyFlex 5- Different Kinematics: 1-Reciprocation: • Reciprocating motion can be described as an oscillating motion when an instrument rotates in 1 direction and then reverses direction before completing a full rotary cycle. • The use of reciprocating motion was shown to extend the lifespan of a NiTi instrument and, therefore, the resistance to fatigue in comparison with continuous rotation. Reciproc 2-The Self-adjusting File (SAF). 6- Single File Systems: Use only single file to shape the canal Manufacturing Strategies To Improve Clinical Performance Of NiTi Instruments 1-Changing Design 2- Surface Treatment 3- Changing Manufacturing Procedure 4- Thermo mechanical treatment of NiTi 5- Different Kinematics 6- Single File Systems: A B C Engineering criteria: 1- Helical angle ( discussed before) 2- Pitch 3- Clearance space 4- Rake angle 5- Radial land Aims: The educational aims of this lecture are to detail different instruments available for root canal enlargement. Objectives: On completion of this lecture, the student should have an understanding of how to use different instruments to enlarge root canals, their indications and advantages and disadvantages of each 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