Endodontic Instruments are generally made of carbon or steel, however recently NiTi instruments, made up of titanium and of Nickel, are introduced in the field of Endodontics. In addition of mechanical manipulation during the endodontic procedures, the Endodontic Instruments are supposed to be able to withstand sterilization in the autoclave. Instruments are divided into the following four basic groups:
Small endodontic instruments such as broaches, reamers, and files are kept in a compartmentalized box for ease of use and safety.
Barbed broaches remove bits of pulp or debris from the canal. They are manufactured from a round wire whose surface has been notched to form barbs. The barbs are used to engage the pulp as the broach is carefully rotated within the canal; once the tissues are entangled, broach is withdrawn out of the canal.
Reamers are endodontic instruments which are used to enlarge the canals during endodontic treatment. Reamers are designed to be inserted to the apical level of instrumentation, then rotated and withdrawn. They must never be twisted like a corkscrew.
There are different types of files used during Endodontic treatment
These files are designed to be inserted to the apical level of instrumentation and withdrawn along the canal wall, cuffing with a combination of rotational and gradual pull motion. K-files are more tightly wound than the reamer.
These files are the most effective of root canal endodontic instruments. They are used like a rasp (coarse file), cutting by a pull stroke against the canal wall. The Hedstrom file must never be rotated, and because of its structure, this file must never be forced into a canal. The Hedstrom file should never be the first endodontic instruments introduced into the canal and it should only be used to enlarge the canal after it has been opened up by reamers and/or K-files.
Each file may be used several times, in every instance inserted to the apical level and withdrawn against the buccal, lingual, mesial, and distal walls.
This file is used to remove any fibrous tissue remaining in the canal.
Gates-Glidden drills are rotary instruments that fit into a handpiece. This long, spiraled drill is used to remove gutta percha within the canal or to open or expand a canal orifice.
BASIC SHAPE OF REAMERS AND FILES
Reamers and K-files are endodontic instruments which are made from rectangular or triangular blanks twisted to give a spiral form. The number of spirals or cutting flutes may differ, but the number is usually higher in the file than the reamer. Typically, K-files are made from rectangular blanks, and reamers from triangular blanks. Because reamers have fewer flutes and show a triangular cross-section, more flexibility is achieved with reamers than with Kfiles. Hedstrom ifies are made from round blanks, and the flutes are cut into the blank, giving it a spiral, screw-like appearance.
Conventional Root canal endodontic instruments are generally made from stainless steel. They may be used repeatedly until they lose their sharpness (after about four or five root canals). The smaller instruments (sizes 15—25) may lose their cutting efficiency more quickly.
STANDARDIZATION OF ROOT CANAL INSTRUMENTS
Root canal endodontic instruments utilized today are standardized. All manufacturers of endodontic instruments follow the specifications or standards for these instruments, determined by dental organizations and the International Standardization Organization (ISO). The standardized endodontic instruments are manufactured in numbers (sizes) ranging from 6 to 150. An instrument’s number is identical to the actual diameter of its tip expressed in hundredths of a millimeter (mm). Thus, an instrument #55 has a diameter of 0.55 mm at the tip.
Although standardized endodontic instruments are made in various lengths (e.g., 21 mm, 25 mm, and 31 mm), the length of the blade with cutting flutes is always the same (16 mm) regardless of the size of the instrument. The diameter of the blade where the cutting flutes end (D2) is always 0.32 mm wider than the tip diameter (Dl). So, the relation can be described mathematically as:
Like the Standardized Sizes of Root Canal endodontic instruments, there is standardized colour coding also (white, yellow, red, blue, green, black, etc.), beginning with #15, which was originally the smallest instrument. Three lower numbers added since the original list (#6, #8, and #10) are pink, gray, and purple respectively.
Working Length of endodontic instruments
Working length is the distance (in millimeters) between a reference point on the incisal or occiusal surface and the apex of the root. It establishes the extent of instrumentation and the apical level of root canal filling. This procedure must be accurately and easily performed. It must be easily confirmed and repeatable.
For an intact, well-restored tooth, the most common plane of reference in an anterior tooth is the incisal edge. A cusp is often used as a point of reference in a posterior tooth. If a posterior tooth has fractured cusps, a lower, flatter surface must be used as a reference point.
IRRIGATING SYRINGES AND SOLUTIONS
Debridement (removal of inorganic and organic debris or irritants of the root canal system is essential for predictable endodontic therapy. The use of an endodontic irrigant during canal preparation is necessary to adequately debride the canal system.
Various types of syringes are used to apply irrigating solution (typically 5—10 ml) to the pulp chamber and root canals. Generally the disposable plastic syringes are used with a 25- or 27-gauge disposal needle. The needle is usually bent at an angle that allows easy access and insertion into the canal for the effective irrigation of the root canal.
Sodium Hypochiorite (NaOCI)
This irrigating solution is currently the irrigant of choice. This chemical agent demonstrates following features, making it a suitable root canal irrigant:
• Powerful antimicrobial activity.
• Excellent necrotic tissue solvent.
• Commendable effectiveness in removing organic debris from the root canal system.
• Lubricating effect for instrumentation of the canal walls.
• Extremely long shelf life.
Hydrogen Peroxide (H202)
This irrigating solution is not a necrotic tissue solvent and has little antimicrobial activity. It is not effective when used alone as an irrigant in debriding the canal system. A 3% solution of H202 has an effervescent action making it very effective in dislodging gross debris and food particles from teeth that have been left open for drainage.
Hydrogen peroxide is recommended for use only in conjunction with sodium hypochiorite.
OTHER INSTRUMENTS AND MATERIALS
A paper point is an absorbent cone-shaped point used to clean and dry the canal after irrigation. They are available in different sizes and diameter, corresponding to various sizes of the reamer.
Gutta Percha Points
Gutta percha is a material from the latex exudate of rubber trees found in Malaysia, Brazil, and Mexico. Through the techniques of pressure, heat, or chemicals, it can be molded to seal all canal openings. It is combined with zinc oxide, resins, fillers, and other materials before being manufactured into points or cones.
Like the paper points, they are also available in different sizes and diameter. During the root canal obturation, the master cones correspond to the endodontic instruments sizes and are used to fill the bodies of the canals, while the accessory cones are inserted to fill voids created by the condensation procedure.
Lentulo Spiral Drill
A Lentulo spiral drill is made of fine wire spiraled into the shape of a reverse auger. It is a very delicate rotary endodontic instruments that’s used in a contra angled handpiece at slow speed. When the spiral is turned clockwise by the handpiece, it carries the cement (e.g., calcium hydroxide) apically into the canal.
A spreader is a sharp, pointed, and tapered hand instrument that is used to force gutta percha apically and laterally during the lateral condensation filling technique.
The root canal condenser (or plugger) is more rigid and has a greater diameter than a spreader that is used for lateral condensation. The blunted end of a condenser is used for vertical condensation to force heated, softened gutta percha apically.
An endodontic explorer has two sharp, tapered ends. One end is at a right angle and the other is straight. The endodontic explorer is the greatest aid in exploration and finding of tiny root canal entrances.
STERILIZATION AND MAINTENANCE
The glass bead sterilizer is used at chairside to sterilize endodontic instruments. It contains glass beads one or two millimeters in diameter and retains heat at 218°—246° Celsius (425°—475° Fahrenheit). The required sterilization time is 15 to 20 seconds for files and reamers, and 20 to 30 seconds for larger metal instruments.
Every instrument used must be cleansed of debris by using a two-by-two-inch gauze before reinsertion into the canal. The instruments should always be used in a wet field to prevent binding and the area should be irrigated with sodium hypochiorite to act as a lubricant for the instrument.
Strain deformation. endodontic instruments such as files are very delicate and they can be deformed when too much force is applied. Once a life is deformed, it can easily break. So, before sterilizing any endodontic instruments, it should be checked for any deformity and the deformed endodontic instruments must be discarded, to avoid its breakage in the root canal.