Lec 7 - Anas Mahdee.pdf.................
- 1. Lec 7. Endodontics Ass. Prof. Dr. ANAS F MAHDEE BDS. MSc. Iraq PhD. UK
- 2. Step-down Technique This technique was developed to shape the coronal part (coronal preflaring) of the canal before instrumentation of the apical part. The objectives of this technique is 1- To permit straight access to the apical region of the canal by eliminating coronal interference 2- To remove the bulk of necrotic tissue and microorganisms before apical shaping to minimize extruded debris through the apical foramen during instrumentation. 3- To allow deeper penetration of irrigant deeply into the apical part of the canal. In addition, it provide coronal escape way for debris extrusion from the apex. 4- The WL is less likely to change with less chance of zipping near the apical constriction.
- 3. Procedure: Preparation of two coronal root canal thirds using Hedstrom files of size #15, #20, and #25 to 16 to 18 mm or where they bind. These files are used with circumferential filing motion on the canal walls. Thereafter, increasing the coronal flaring of the canal by using Gates-Glidden drills size 2, 3, and 4, in sequential order with 1 mm shorter for each larger file. Followed by canal WL estimation, then instrumentation of the remaining apical part of the canal. This includes using small K-file # 15, 20 and 25 to prepare the apical seat. Combining the two parts, step-down and apical shape, by stepwise decreasing of WL of incrementally larger files. Frequent recapitulation with a #25 K-file to WL is advised to prevent blockage.
- 4. Link of YouTube video https://youtu.be/uLAstzZeSc0
- 5. Balanced Force Technique • This technique was introduced after the development of new file ‘Flex- R file’. This file has “safe tip design” with a guiding land area behind the tip. This design help the file to be guided within the canal, especially the curved one, and prevent engaging the wall and ledge formation. • This technique can be described as positioning and preloading an instrument through a clockwise rotation and then shaping the canal with a counterclockwise rotation.
- 6. Procedure: 1. In balanced force technique, preparation is completed in a step-down approach. 2. After that, the balanced force hand instrumentation begins in the apical preparation by placing, cutting, and removing instrument using only rotation motion. C 2. File motion include: A. Placement (apical pushing with 1/4 clockwise rotation) B. Cutting (repeated 3/4 counter clockwise rotation) C. Removal (1/4 clockwise rotation with pulling for removing debris)
- 7. 3. The original Balanced Force concept then refers to apical control zones, for example, first using sizes #15 and #20 files to the periodontal ligament (i.e., through the apical foramen) and then reducing the working depth by 0.5 mm for subsequent sizes #25, #30, and #35. The apical shape is then completed 1 mm short using sizes #40 and #45 under continuing irrigation with NaOCl. Advantages: Lesser chances of creating a ledge, blockage or canal transportation.
- 8. Crown Down (Pressure-less) Technique The crown-down instrumentation concept based on the canal shaping technique moving from the crown toward the apical portion of the canal. This concept was the introductory for the most recent rotary instrumentation technology.
- 9. Procedure:
- 10. Link of YouTube video https://youtu.be/qfBYMA2_evQ
- 11. Biological Advantages of crown down technique: 1. Removal of tissue debris coronally, thus minimizing the extrusion of debris periapically. 2. Reduction of postoperative sensitivity which could result from periapical extrusion of debris. 3. Greater volumes of irrigants can reach in canal irregularities in early stages of canal preparation because of coronal flaring. 4. Better dissolution of tissue with increased penetration of the irrigants. Clinical advantages of crown down technique: 1. Enhanced tactile sensation with instruments because of removal of coronal interferences. 2. Flexible (smaller) files are used in apical portion of the canal; whereas larger (stiffer) files need not be forced but kept short of the apex. This decrease the chance for canal ledging, transportation and perforation. 3. Straight line access to root curves and canal junctions. 4. Provides more space for irrigants. 5. Enhance canal debridement and decrease frequency of canal blockages. 6. Desired shape of canal can be obtained that is narrow apically and wider coronally. This provides better room for Gatta Percha condensation to obtain proper three dimensional obturation of the root canal.
- 13. • Studies have shown that mechanical instrumentation, whether using manual or rotary instruments, can not sufficiently debride and disinfect root canals. • Every root canal system has spaces that cannot be cleaned mechanically. • The only way for cleaning webs, fins and anastomoses is through the effective using of irrigation solutions
- 14. Requirements of ideal irrigant solution: 1- Have a broad spectrum antimicrobial activity. 2- Be able to effectively sterile the canal (or at least disinfect them). 3- Have the ability to dissolve necrotic tissue and debride the canal. 4- Lubricant solution. 5- Low level of toxicity. 6- Have low surface tension to be able to penetrate into inaccessible areas. 7- Prevent the formation of smear layer during or after instrumentation. 8- Inhibiting bacterial toxins such as endotoxin. None of the available irrigant can fulfil all these requirements together however a combination of two or more can be use to obtain most of them.
- 15. Functions of irrigants 2- Canal wetting material: ↑ efficacy of instrument ↓ instrument breakage 1- Removal of dentinal shavings by physical flushing to prevent their packing at the apical region of the root canal.
- 16. 3- Irrigants act as a solvent for necrotic tissue (loosen debris, pulp tissue and microorganisms from irregular dentinal walls). 4- Irrigants facilitate the removal of debris from inaccessible regions of root canals. 5- Most irrigants have germicidal and antibacterial properties. 6- Irrigants also have bleaching action to lighten teeth discolored by necrotic pulp tissue, caries or restorative material. 7- Irrigats facilitate the removal of smear layer and opening of the dentinal tubules.
- 17. Factors that modifying the activity of irrigating solution 1- Concentration: the dissolving capacity of some irrigation solution, such as sodium hypochlorite, can be increased with higher concentration (5.2 rather than 2.5%). However the cytotoxicity of higher concentrations is extremely higher. 2- Contact: the irrigant must contact the intracanal substrate (organic tissue or microbes) to be effective, otherwise it won’t be able to dissolve or flushout the debris. Larger canal diameter → better irrigation to apical region 3- Presence of organic tissue: the organic tissue must be removed mechanically or chemomechanically to increase the efficacy of intracanal irrigation. This can be obtained by simultaneous use of instruments and irrigating solutions. 4- Quantity and frequency of the irrigant used: • More irrigation causes better tissue debridement. • Each time a flush of fresh potent irrigant plays an action.
- 18. 5- Gauge of irrigating needle: usually the 27 or 28 irrigation needle is preferable for better penetration into the canal. 6- Surface tension of irrigation solution: the lower surface tension, the better wettability and the more penetration into narrowest areas of the canals, and even into the dentinal tubules. 7- Level of penetration of the irrigant: Maximum actions of irrigant occurs on coronal part of root canal whereas minimal on apical end. 8- Age of irrigant: Freshly prepared solution is more effective than older one.
- 20. • Normal saline as 0.9% W/V is commonly used irrigant in endodontics. • Very mild in action and can be used in adjunct to chemical irrigant. • Causes gross debridement and lubrication of the root canal. • Basically acts in flushing action. • Used as a final rinse for root canals to remove the chemical irrigant left after root canal preparation. Normal saline Advantages: Biocompatible solution with no adverse effect even if extruded periapically, because its osmotic pressure is the same as that of the blood. Disadvantages: No dissolution, disinfectant and antimicrobial properties. Too mild to thoroughly clean the canal. • Does not remove sear layer.