Recent Rotary NiTi Systems.ppt - Recent Rotary NiTi Systems Designs Specifications and Limitations Outline of the presentation History of Endodontic

Recent Rotary NiTi Systems.ppt - Recent Rotary NiTi Systems...

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Unformatted text preview: Recent Rotary NiTi Systems Designs, Specifications and Limitations Outline of the presentation: History of Endodontic Files. The rise of NiTi Rotary Systems. Design elements of rotary files. Some limitations of rotary NiTi systems. Classification of systems acc. to motion and No. of files. Designs and Specifications of different systems. Open discussion. History of Endodontic Files The manufacture of the first instruments for endodontic use dates to 1875. With the advent of dental radiology, local anesthesia, and advances in bacteriology at the turn of the last century, a new era opened in endodontic therapy. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments •These early instruments, which were made by hand from thin steel wires, performed more or less the function of modern barbed broaches. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments In 1932, G. V. Skillen stated that it was necessary to curette the canal walls to remove the pulp debris. He believed that all residual tissue became degenerative and would lead to failure of canal therapy. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments Grove designed “standardized instruments and gold cones”. His intent was to prepare the radicular canal space according to precise norms of shape, size, and conicity. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments In 1955, Ingle was the first to express finally the need for standardization of canal instruments. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments In 1961, Ingle established a basic, standardized shape for endodontic instruments and a standardized endodontic technique. He substituted stainless steel for carbon steel. Introduced color-coded instruments that were smaller (06 and 08) and larger (110-140) than those in use at the time. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments Limitations of conventional designs of st/st files Stainless steel instruments have low fracture resistance when used in continuous rotation. Many filing techniques were used to overcome this problem which are time and effort consuming. Also, increasing possibilities of debris extrusion leading to inflammatory response apically. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments The ISO taper (0.02) does not correspond to most of canals tapering that may reach 0.04 or 0.06 mm, this leads to using more number of instruments to reach the desired taper. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments Being made of stiff material St/St file have more tendency to transport apical foramen and deviate from original anatomy of the canals. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments The Rise of NiTi Rotary Systems To overcome the St/St file problems (Rotary NiTi Greater Taper instruments) were invented. WHY NICKEL-TITANIUM? The significant advantage of NiTi file is its unique ability to negotiate curvatures during continuous rotation without undergoing the permanent deformation or failure that St/St files might undergo. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.18 Rotary instruments in NiTi Brief History ! NiTi wires were first introduced in dentistry to replace the St-St wires in Orthodontic treatment then in Endodontic treatment. St-St wires were rigid and non flexible wich limited the age of ortho. treatment to youngsters (till 21 yrs) rather than older patients. Now with NiTi wires the age of which patient can Ortho treated has been extended more. Nickel-titanium is termed an exotic metal because it does not conform to the normal rules of metallurgy. As a super-elastic metal the application of stress does not result in proportional strain. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.18 Rotary instruments in NiTi This unusual property is the result of undergoing a molecular crystalline phase transformation when stressed. External stresses transform the Austenitic crystalline form of nickel-titanium into the more forgiving Martensitic crystalline form. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.18 Rotary instruments in NiTi WHY ROTARY INSTRUMENTATION? Mechanical rotation provide enhanced ability to collect and remove debris from the canal system as it augers debris only in a coronal direction from the root canal space. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.18 Rotary instruments in NiTi Hand instrumentation using file insertion motions without rotation or with counterclockwise motion pushes debris into internal canal anatomy or even apically through the portals of exit. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.18 Rotary instruments in NiTi Mechanical rotation of nickel titanium files can provide better control for maintaining the central axis in curvatures that results a more conservative canal preparation. As a result: reduction in the time and effort required for instrumenting canals. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.18 Rotary instruments in NiTi Design elements of rotary files Radial Land Relief area Helix angle Rake angle Core of the file Pitch Cutting Tip Radial Land: Its is defined as the surface that projects axially between the flutes. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. Relief area: It is the area on the file that does not engage dentin inside the canal during rotation. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments . Helix Angle: The angle that the cutting edge make with the long axis of the file. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.19 The Protaper technique. Rake Angle: The angle between the cutting edge and the surface to be cut. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.19 The Protaper technique. Files with positive Rake angle Quantic K3 Cutting action (used in filling motion inside the canal) Files with negative Rake angle Protaper I race Revo S Scrapping action (used in brushing motion inside the canal) Core of the file: Central part of the file that is surrounded by flute and provide central strength to the file. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. Files with great core ( less flexible ) Protaper )Files with less core (more flexible I Race Revo S Pitch: It is the distance from the crest of one thread to the next. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.19 The Protaper technique. Files with a consistent pitch have a tendency to suck you down into the canal (profile) varied pitch that allows debris to effectively channel coronally ):Files with constant pitch ( suck down into canal profile less control of the file ):Files with variable pitch (Dont suck down into canal Revo S Protaper I race Great control of the file File Tip File tip is essential element in file design. Non-Cutting is a safety feature as in preserve the original anatomy of the canal avoiding transportation. Some designs offer a Cutting tip for more cutting efficiency specially in Re-treatment files kit. Limitations of Rotary NiTi Files Although rotary instrumentation can offer the operator numerous advantages, the prevention of file failure requires greater consideration. WHAT CAUSES BREAKAGE? WHAT IS TORSION? Breakage is directly related to excessive stresses of torsion and fatigue. Torsion: is the axial force of being twisted that results when one part of a file rotates at a different rate than another part. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. Any distortion of a file that results from twisting, such as unwinding, is caused by stress of torsion. When a file resists rotation during hand instrumentation, excessive torque can be perceived and file breakage can usually be avoided. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. However, as torque is essentially impossible to sense during automated instrumentation. So understanding the factors of file breakage is the most important aspect for this modality of canal preparation. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. WHAT IS FATIGUE? File fatigue is the result of repetitive stress predominantly during flexion while rotating around a canal curvature. Metal fatigue usually begins at the surface where minute defects act as points of stress concentration. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. A fatigue failure is particularly insidious because it can occur without any obvious warning. Knowledge of the relationships of file sizes and canal anatomy is important when dealing with the combined stresses of torque and fatigue. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. “Computerized handpieces address some of the problems of torque but wont replace the dentist’s judgment for appropriate technique” Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. WHAT CAUSES FATIGUE? Bending stresses They are the main causes of strain and they depend on the original anatomy of the canal which, with its curves, forces the instrument to bend as it passes through it. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.18 Rotary instruments in NiTi. Pruett et al. have demonstrated that the curve radius, the bend angle and the largeness of the instrument are the factors responsible for the fractures due to bending fatigue. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.18 Rotary instruments in NiTi. Sequale of Bending Stresses: On the inside of the curvature, a rotating file is compressed. On the outside of the curvature the file undergoes tension. As a file rotates around a curvature each surface undergoes compression and release destruction. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. When tension is applied, faults in the file are propagated. Therefore, a size .20 diameter can resist fatigue 50% more than a size .25 diameter. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. As the diameter of a tapered file increases as it progresses through a curvature the stress on the file eventually reaches the point of potential failure. At this point the use of the file should be terminated in favor of a smaller diameter or smaller tapered file. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. Important relationships between NiTi files and canal anatomies that enable us to improve our technique avoiding the limitations of stressed NiTi file include: A file with a more efficient cutting design requires less torque and/or pressure to accomplish the same degree of root canal enlargement. To maintain your file’s cutting efficiency and avoid debris accumulation>> file should be cleaned with gauze regularly before each entry inside the canal. In a straight canal, the ability of a file to withstand torque varies directly with the square of its diameter. In a curved canal, the ability of a file to resist fatigue varies inversely with the square of its diameter. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. The torque required to rotate a file varies directly with the surface area of the file’s engagement in the canal. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. Fatigue of a file increases with the number of rotations of the file in the canal. Fatigue of a file increases with the degree of curvature of the canal. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. To improve efficiency, the smaller the surface area of a file engaged in the canal, the greater the rotation speed should be. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. The more spirals a flute has per unit length around the shaft of a file, the greater the torque is required to rotate a file and the more stress concentration points there are for potential failure, but the more flexible it is The fewer spirals a flute has per unit length around the shaft of a file, the more it resists deformation,but the more rigid it is. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. Files with radial land and relief and positive rake angle: - center the file in the canal. - prevent canal transportation. The sharper the cutting blade of a file, the fewer spirals per unit length the file should have. The greater the number of flutes with similar helix angles, the greater tendency a file has to screw into the canal and become bound. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.22 - The Quantec Rotary NiTi System. Classification of systems according to Motion Rotary NiTi Systems (B) Reciprocating Motion: (A) Rotating Motion 1) Series: •Rotary GT &ProFile •Protaper Uni./Next •Hero Shaper •Revo-S & RACE •WaveOne. •Reciproc. 2) Single file: •One Shape •Self Adjustable File (C) Hybrid Motion: TF Adaptive File (A) Rotating Systems 1) In Series of files GT Rotary. ProFiles. ProTaper Universal. ProTaper Next. Hero Shaper. I-Race. Revo-S. Rotary GT Files by Dentsply The Rotary GT Files are instruments in NiTi devised by: Dr. S.Buchanan. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. Design: Non cutting tip. Prefixed tip diameter. Prefixed maximum flute diameter (MFD). Multiple tapers. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. Blade length inversely proportional to the taper. Have a blade direction which is clockwise. Blades are classical “radial lands” without the sharp cutting angles. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. The clockwise direction make it possible to use the Rotary GT in continual clockwise rotation without screw in. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. How Rotary GT Files Perform? Rotary GT Files are hardly efficient in lateral cutting and they tend to imprint their shape into the canal; on the basis of the last GT brought to the working length. Operator can predetermine the final diameter and tapers of the preparation and choose the corresponding paper points, gutta-percha cones or Thermafil obturators. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. How it's used? The Rotary GT Files are generally used in a crown-down sequence progressively reducing their taper and/or their diameter. The choice of the instrument series will be made on the initial examination (thin, medium and wide canals) and then confirmed by the apical gauging results. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. The recommended rotational speed is about 250to 300 rpm; the torque of the micromotor should be set on: low values for GT’s with a taper of .04. on medium values for those with a taper of .06. medium/ high values for GT’s with a higher taper. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. ProFiles by Dentsply The ProFiles are rotary instruments in nickel titanium introduced by Dr. W. Ben Johnson in 1994; and they remain amongst the most popular NiTi instruments. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. Design: ProFiles are obtained by micromachining three parallel Furrows on a nickel titanium wire. The surfaces of the wire between the furrows are not sharpened so that in cross-section the instrument has a design defined as a “triple U” with blades characterized by flat cutting surfaces called “radial lands” Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. Limitations of use: The main consequence of this particular blade design is a reduction of the central “core” resulting structural fragility to torsional stress conditions. i.e. long and calcified canals or application of excessive force. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. To avoid this inconvenience the ProFiles manufacturing companies have worked on three fronts: 1. Production of instruments with a greater taper able to increase the total metal mass in cross-section and therefore able to increase torsion resistance. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. 2. Introduction of Endodontic handpieces with torque control, able to prevent using instruments with an excess of manual pressure. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. 3. A sequence of instrument use which allows reduction of the contact surface and therefore the friction of the blades with the dentinal walls. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. The GOOD thing in their design: Flexibility: The “triple U” design with the correlated reduction of the metallic mass increase flexibility which is particularly useful in the presence of flexional stress. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. Cutting efficiency: - The “radial lands” blades of the ProFiles are not efficient in lateral cutting; ProFiles cut perimetrically at 360° on all the walls. - When they have imprinted their shape in the canal their action decreases rapidly. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. The low cutting capacity and their flexibility make the ProFiles particularly useful in: - shaping of curved canals. - reducing the risk of apical tears and transportation. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. Usage: ProFiles can be used on their own or in hybrid sequences to finish off the canals prepared with more resistant instruments such as the ProTaper. In the “pure” instrument sequences ProFiles are used in a crown-down based on reductions of taper and/or of diameter. Arnaldo Castellucci. Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. The recommended rotational speed is 250-300 rpm. The torque of the microhandpiece should be set at: - Low values for the .02 and .04 taper. - Medium values for those with .06 taper. Arnaldo Castellucci. Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. ProFile Orifice Shapers The ProFile Orifice Shapers are 6 instruments used for the elimination of coronal interferences and flaring canal coronal third. Characterized by blades and a tip identical to ProFiles, length of 19 mm, active part that is 10 mm long. They are less efficient than the Gates-Glidden drills or the SX ProTapers. Arnaldo Castellucci. Endodontics Vol.2, IL Tridente. 2009. Ch.13 Endodontic instruments. The ProTaper Universal System by Dentsply PROTAPER Design is based on the following geometry: A. The shaping files: Shaping File # 1 and # 2, termed S1 and S2. Have purple and white identification rings on their handles, respectively. The S1 and S2 files have D0 = 0.17 mm and 0.20 mm, respectively, D14 =1.20mm. Arnaldo Castellucci.Endodontics Vol.2, IL Tridente. 2009. Ch.19 The Protaper technique. Shaping Files The Auxiliary Shaping File, termed SX, has no identification ring on its gold-colored handle. Have shorter overall length of 19 mm, provides excellent...
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