The success rate of endodontics therapy is nearly 90-95 percent. Still 5 percent cases are deemed as failures. In the global scenario, this 5 percent will account to a very large number when assessed for a period of one year. The causes for endodontic failure are mainly divided into:
1. Improper case selection
2. Procedural errors during Access opening
3. Procedural errors during Biomechanical prepara- tion
4. Procedural errors during Obturation
5. Miscellaneous
1. Improper case selection
2. Procedural errors during Access opening
3. Procedural errors during Biomechanical prepara- tion
4. Procedural errors during Obturation
5. Miscellaneous
CASE SELECTION
Case selection is a very important step in the endo- dontic therapy.
Factors:
a. Involvement of coronal tooth structure by caries or trauma
b. Improper occlusion
c. Oral hygiene
d. Length of the remaining clinical crown
e. Previous restorations and health of periodontal ligament:
a. Involvement of coronal tooth structure by caries or trauma (Fig. 25.1): The extent of caries involve-
ment and its extension to the root surface and sometimes floor or furcation of the pulp chamber has to be evaluated clinically and radiographically and such cases have to be assessed for longevity of final restoration.
Case selection is a very important step in the endo- dontic therapy.
Factors:
a. Involvement of coronal tooth structure by caries or trauma
b. Improper occlusion
c. Oral hygiene
d. Length of the remaining clinical crown
e. Previous restorations and health of periodontal ligament:
a. Involvement of coronal tooth structure by caries or trauma (Fig. 25.1): The extent of caries involve-
ment and its extension to the root surface and sometimes floor or furcation of the pulp chamber has to be evaluated clinically and radiographically and such cases have to be assessed for longevity of final restoration.
b. Improper occlusion (Fig. 25.2): Occlusion should always be verified before treatment. Improper occlusion may be due to the rotation, tilting, drifting or supra eruption of the tooth from the opposite arch.
c. Oral hygiene: Good oral hygiene is very necessary for success of endodontic therapy as poor oral hygiene contributes to the growth of microorganisms, especially resistant strains, which may be difficult to eradicate by the use of routinely used irrigating solutions. The patients should be advised thorough oral prophylaxis followed by oral hygiene instructions, i.e. brushing, flossing and use of mouth rinses.
d. Length of the clinical crown (Fig. 25.3): According to clinical studies there should be at least 2 mm of remaining coronal tooth structures otherwise the prognosis of endodontic therapy would be compromised. The clinician should have a clear idea of final restoration and its durability before initiating endodontic therapy. After endodontic treatment the final restoration should have a durability of at least 10 to 20 years. If the length of the clinical crown is less it can be increased by crown lengthening procedures such as gingivectomy, orthodontic extrusion, etc.
e. Previous restorations (Fig. 25.4): The tooth under-
going endodontic therapy should be carefully assessed for the integrity of old restorations. Defective restoration should be removed. Secondary caries should be excavated and the restorations should be replaced using GIC or composite prior to the endodontic therapy.
f. Health of periodontal ligament (Fig. 25.5): This is a critical area in the evaluation of endodontic therapy. The investing tissues of the teeth such as gingiva, periodontium and alveolar bone have
to be assessed for health. Clinical assessment of mobility of the tooth should be done. Periodontal examination and careful radiographic assessment of bone loss is essential. Decision should to be taken by an interdisciplinary approach in consultation with periodontists.
c. Oral hygiene: Good oral hygiene is very necessary for success of endodontic therapy as poor oral hygiene contributes to the growth of microorganisms, especially resistant strains, which may be difficult to eradicate by the use of routinely used irrigating solutions. The patients should be advised thorough oral prophylaxis followed by oral hygiene instructions, i.e. brushing, flossing and use of mouth rinses.
d. Length of the clinical crown (Fig. 25.3): According to clinical studies there should be at least 2 mm of remaining coronal tooth structures otherwise the prognosis of endodontic therapy would be compromised. The clinician should have a clear idea of final restoration and its durability before initiating endodontic therapy. After endodontic treatment the final restoration should have a durability of at least 10 to 20 years. If the length of the clinical crown is less it can be increased by crown lengthening procedures such as gingivectomy, orthodontic extrusion, etc.
e. Previous restorations (Fig. 25.4): The tooth under-
going endodontic therapy should be carefully assessed for the integrity of old restorations. Defective restoration should be removed. Secondary caries should be excavated and the restorations should be replaced using GIC or composite prior to the endodontic therapy.
f. Health of periodontal ligament (Fig. 25.5): This is a critical area in the evaluation of endodontic therapy. The investing tissues of the teeth such as gingiva, periodontium and alveolar bone have
to be assessed for health. Clinical assessment of mobility of the tooth should be done. Periodontal examination and careful radiographic assessment of bone loss is essential. Decision should to be taken by an interdisciplinary approach in consultation with periodontists.
Radiographs are very important in the assessment of endodontic failures. Improper radiographs, errors in angulations, improper exposure time, and improper development contribute to poorly diagnostic radiographs which is difficult to read and interpret. The radiograph reveals root canal morphology. Configuration of the pulp chamber and the root canals, presence or absence of calcification in pulp chamber or root canals. This information is very useful and plays an important role in endodontic therapy.
Access Opening
Direction of the bur during access opening plays an important role. In case of anterior teeth, it should be parallel to the long axis of the tooth (Fig. 25.6). In posteriors, it should be directed towards locations of the larger canals. It should be done with minimal removal of tooth structure. Anterior tooth perforation occurs most commonly at CEJ. In posterior teeth when perforation occurs at the furcation area, there will be profuse bleeding. Control of the hemorrhage should be done with cotton pellets placed in the pulp chamber with pressure or hydrogen peroxide in a cotton pellet under pressure. Wait for 2- 5 min till the bleeding stops. Locate the bleeding points carefully and use a biocompatible material to seal the perforation. Such materials include MTA (Fig. 25.7), calcium hydroxide and zinc oxide eugenol and its modifications. Use of zinc oxide eugenol for perforation repair is controversial as many studied have proved that it irritates the tissues
Biomechanical Preparation
During biomechanical preparation perforation of the root canal may occur. The level of perforation may be
a. Mid root
b. Apical third
If the peroration occurs in the canal, locate the perforation area by using an apex locator. Surgical intervention is often required. Reflect the flap, locate the perforation area and follow by adequate cleaning. Place the instrument in the canal and the restorative procedure should be undertaken. Previously amalgam was the material of choice. Now with the advent of advanced newer materials it is rarely being used. Calcium hydroxide can be used as sub-base and the restoration can be completed using either glass ionomer cement, IRM, MTA, etc. (Fig. 25.8).
If the clinician is unable to locate the canals, loupes and microscopes can be used to aid in magnification.
During biomechanical preparation perforation of the root canal may occur. The level of perforation may be
a. Mid root
b. Apical third
If the peroration occurs in the canal, locate the perforation area by using an apex locator. Surgical intervention is often required. Reflect the flap, locate the perforation area and follow by adequate cleaning. Place the instrument in the canal and the restorative procedure should be undertaken. Previously amalgam was the material of choice. Now with the advent of advanced newer materials it is rarely being used. Calcium hydroxide can be used as sub-base and the restoration can be completed using either glass ionomer cement, IRM, MTA, etc. (Fig. 25.8).
If the clinician is unable to locate the canals, loupes and microscopes can be used to aid in magnification.
Broken Instrument (Fig. 25.9)
One of the important and most commonly encountered clinical mishaps is instrument breakage. It is better to prevent instrument breakage rather than to attempt its removal after breakage. The success of removal of broken instrument depends upon the location, direction of the instrument and type of the instrument (Figs 25.10 to 25.18).
One of the important and most commonly encountered clinical mishaps is instrument breakage. It is better to prevent instrument breakage rather than to attempt its removal after breakage. The success of removal of broken instrument depends upon the location, direction of the instrument and type of the instrument (Figs 25.10 to 25.18).
Considerations in Assessing Fractured Instruments
• When the instrument broke - at the beginning or end of preparation
• Multiple radiographic angles
• Width and length of the fragment
• Type of metal - stainless steel or nickel titanium
• Location of instrument - coronal, middle or apical third
• Anatomical cross-section of the canal - round or oval
• Position of any curvature/recurvature, and portion of fragment within this curvature
• Presence or absence of apical periodontitis.
Precautions to Minimize Instrument Fracture
1. Considering files as disposable items, discarding damaged instruments during treatment.
2. Not forcing instruments.
3. Using instruments in the correct sequence, alternating sizes and tapers as appropriate.
4. Not rotating stainless steel instruments more than a quarter turn clockwise.
5. Confirming a glide path to size 20 with hand files prior to using rotary NiTi instruments.
6. Taking care with certain canal anatomy when using nickel titanium, e.g. canals that merge, divide or are dilacerated.
7. Ensuring straight line access before preparing the canals, thereby reducing stress on the instruments.
H-files: A space is made by working around the broken instrument and retrival is accomplished by twisting multiple files in clockwise rotation and subsequent removal.
Instrument Removal System (Dentsply) (Fig. 25.19)
IRS is a new instrument removal system which allows for the effective removal of canal obstruction, including separated instruments. The kit comprises of a microtube with a side opening used to ‘trap’ the obstruction, e.g. the separated instrument and a ‘screw wedge’ to secure the obstruction in the microtube which once secured is then removed along with the microtube.The product is available as a starter kit which comes with two microtube sizes, one designed for narrow canals and one designed for wide canals (diameter 0.6 mm and 0.8 mm). The IRS system is also available separately.
Roydent Endo-extractor
The Endo-extractor system is excellent for removal of separated files and silver points.
• The “Jacobs Chuck”-like device grabs the embedded article with equal force all the way around, requiring minimal pressure.
• Unique hollow trepan drill with an internal diameter of 0.80 mm.
• Stainless steel.
• Sterilizable with autoclave, Chemiclave or dry heat sterilization.
• Available in complete kit or individual sizes.
Ruddle's Instrument Removal System/Post Removal System
Masserann kit (Figs 25.20 and 25.21)
The Masserann kit consists of a number of trepans with diameters from 1.1 to 2.4 mm. The trepans are hollow tubes designed to cut a trough around the metal fragment. These trepans are designed to be used with an anticlockwise rotation. This will assist with the removal of any threaded materials which will have a conventional thread. The operator should be aware of this as a potential problem if attempting to remove a fractured Hand File of Greater Taper, which has a reverse thread. The trough usually has to be cut along at least half the length of the fragment before it is sufficiently loosened to allow its extraction. It is recommended that the trepan is operated by hand, using the special handle provided, and not placed in a handpiece. A feeler gauge from the kit is used to assess the size of the trepan required. EDTA paste will help to lubricate and soften the dentine. The kit also contains a Masserann extractor, which is placed over the end of the loosened fragment so that it may be gripped and removed. If the fragment is too large for the extractor, then a size smaller trepan may be forced over the end of the fragment, which is then gripped firmly enough to allow its withdrawal from the canal.
If it is difficult to remove the broken instrument try to bypass it. Complete the biomechanical prepa- ration followed by obturation.
Masserann kit (Figs 25.20 and 25.21)
The Masserann kit consists of a number of trepans with diameters from 1.1 to 2.4 mm. The trepans are hollow tubes designed to cut a trough around the metal fragment. These trepans are designed to be used with an anticlockwise rotation. This will assist with the removal of any threaded materials which will have a conventional thread. The operator should be aware of this as a potential problem if attempting to remove a fractured Hand File of Greater Taper, which has a reverse thread. The trough usually has to be cut along at least half the length of the fragment before it is sufficiently loosened to allow its extraction. It is recommended that the trepan is operated by hand, using the special handle provided, and not placed in a handpiece. A feeler gauge from the kit is used to assess the size of the trepan required. EDTA paste will help to lubricate and soften the dentine. The kit also contains a Masserann extractor, which is placed over the end of the loosened fragment so that it may be gripped and removed. If the fragment is too large for the extractor, then a size smaller trepan may be forced over the end of the fragment, which is then gripped firmly enough to allow its withdrawal from the canal.
If it is difficult to remove the broken instrument try to bypass it. Complete the biomechanical prepa- ration followed by obturation.
OTHER SYSTEMS: RUDDLE’S KIT (FIG. 25.22)
Ledge Formation
Ledge formation is a deviation from the original canal curvature without communication with the periodontal ligament, resulting in a procedural error also known as ledging.
Causes
1. Inadequate extension of the access cavity to allow adequate access to the apical part of the root canal.
2. Loss of control of the instrument during access opening from proximal surface.
1. Incorrect assessment of the root canal direction.
2. Improper working length determination.
3. Forcing and driving the instrument into the canal.
4. Failure to precurve the stainless steel instrument that is too large for a curved canal.
5. Failing to use the instruments in sequential order.
6. Over-reaming the file at the working length.
7. Inadequate irrigation and/or lubrication during instrumentation
8. Excessive use of chelating agents.
9. Attempting to retrieve broken instruments.
10. Removing root filling materials during endodontic retreatment
11. Attempting to prepare calcified root canals.
12. Attempting to prepare blocked canals.
1. Inadequate extension of the access cavity to allow adequate access to the apical part of the root canal.
2. Loss of control of the instrument during access opening from proximal surface.
1. Incorrect assessment of the root canal direction.
2. Improper working length determination.
3. Forcing and driving the instrument into the canal.
4. Failure to precurve the stainless steel instrument that is too large for a curved canal.
5. Failing to use the instruments in sequential order.
6. Over-reaming the file at the working length.
7. Inadequate irrigation and/or lubrication during instrumentation
8. Excessive use of chelating agents.
9. Attempting to retrieve broken instruments.
10. Removing root filling materials during endodontic retreatment
11. Attempting to prepare calcified root canals.
12. Attempting to prepare blocked canals.
Management (Figs 25.23 to 25.25)
1. Negotiate the ledge with smaller instruments and bypass the ledge followed by obturation.
2. Use of Greater taper files can also be used to remove the ledge followed by obturation.
3. If negotiation is not possible, surgical management should be undertaken.
1. Negotiate the ledge with smaller instruments and bypass the ledge followed by obturation.
2. Use of Greater taper files can also be used to remove the ledge followed by obturation.
3. If negotiation is not possible, surgical management should be undertaken.
Elbow Formation (Fig. 25.26)
If more pressure is used on the lateral wall of the apex during biomechanical preparation, elbow will form.
If more pressure is used on the lateral wall of the apex during biomechanical preparation, elbow will form.
Zipping (Fig. 25.27)
Zipping is defined as the elliptical shape that may be formed in the apical foramen during the preparation of a curved canal when a file extends through the apical foramen and subsequently transports the outer canal wall. Misdirection of the root canal instru- ment away from the periapical opening results in zipping.
Prevention
• Precurve the instrument
• Use in proper sequence / recapitulation
• Prevent lateral perforation at apex
• Radiograph should be assessed with the instrument in places.
Zipping is defined as the elliptical shape that may be formed in the apical foramen during the preparation of a curved canal when a file extends through the apical foramen and subsequently transports the outer canal wall. Misdirection of the root canal instru- ment away from the periapical opening results in zipping.
Prevention
• Precurve the instrument
• Use in proper sequence / recapitulation
• Prevent lateral perforation at apex
• Radiograph should be assessed with the instrument in places.
Improper Use of Irrigating Solutions
Irrigation should be used with maximum care to prevent damage to periapical tissues.
Precautions
1. Needle should be loose in the canal.
2. Needle should not be at the apex
3. Force should be less.
Irrigation should be used with maximum care to prevent damage to periapical tissues.
Precautions
1. Needle should be loose in the canal.
2. Needle should not be at the apex
3. Force should be less.
Improper Cleaning and Shaping of the Canals
In case of multiple canals, it is very common to leave some of the infected tissue in the canals.
• Ultrasonic instruments are best to remove any infected tissue at the isthmus and the canal. In the curved canal improper enlargement of orifice leads to removal of dentin at the outer portion enlarge with GG drills or Peeso reamer
• Use GG no- 1 up to the first curvature followed by sequential increase till no. 3 so that the canals can be straightened.
• If stainless steel instrument are used pre-curving is advised to follow curvature of the canal.
• NiTi instrument are safer in curved canals due to superelasticity and shape memory. However, cutting efficiency is less.
In case of multiple canals, it is very common to leave some of the infected tissue in the canals.
• Ultrasonic instruments are best to remove any infected tissue at the isthmus and the canal. In the curved canal improper enlargement of orifice leads to removal of dentin at the outer portion enlarge with GG drills or Peeso reamer
• Use GG no- 1 up to the first curvature followed by sequential increase till no. 3 so that the canals can be straightened.
• If stainless steel instrument are used pre-curving is advised to follow curvature of the canal.
• NiTi instrument are safer in curved canals due to superelasticity and shape memory. However, cutting efficiency is less.
OBTURATION (FIGS 25.28A AND B)
Removal of gutta-percha can be done by 3 methods.
Chemical Method
Solvents such as oil of eucalyptus, oil of turpentine and chloroform have been used to soften gutta-percha for removal, chloroform being the most efficient. However, chloroform is hazardous to use as this is toxic and potentially carcinogenic. Oil of turpentine is less toxic, but there is concern that solvents in general lead to a dimensional change in the gutta-percha, leading to increased microleakage. This together with the fact that it is difficult to control the depth of softening of the gutta-percha and potential leakage of the solvents into the periradicular tissues.
Removal of gutta-percha can be done by 3 methods.
Chemical Method
Solvents such as oil of eucalyptus, oil of turpentine and chloroform have been used to soften gutta-percha for removal, chloroform being the most efficient. However, chloroform is hazardous to use as this is toxic and potentially carcinogenic. Oil of turpentine is less toxic, but there is concern that solvents in general lead to a dimensional change in the gutta-percha, leading to increased microleakage. This together with the fact that it is difficult to control the depth of softening of the gutta-percha and potential leakage of the solvents into the periradicular tissues.
Thermal Removal
A heated instrument can be inserted into the gutta- percha to the desired length to soften and remove the gutta-percha. In narrow canals, a System B spreader
is ideal for removal of gutta-percha. From a pre- operative radiograph, a plugger should be chosen of the correct dimensions, that is likely to bind at the desired length and this position should be marked on the plugger with a rubber stop. The tip should be placed in the gutta-percha and with the heat applied, driven slowly to the desired length in about 2-3 seconds. The heat should be removed the plugger to cool for about 7-10 seconds, twisted and then removed with the gutta-percha. Some authors suggest that gutta-percha should be removed with heat techniques only and mechanical removal only used if heat is insufficient.
A heated instrument can be inserted into the gutta- percha to the desired length to soften and remove the gutta-percha. In narrow canals, a System B spreader
is ideal for removal of gutta-percha. From a pre- operative radiograph, a plugger should be chosen of the correct dimensions, that is likely to bind at the desired length and this position should be marked on the plugger with a rubber stop. The tip should be placed in the gutta-percha and with the heat applied, driven slowly to the desired length in about 2-3 seconds. The heat should be removed the plugger to cool for about 7-10 seconds, twisted and then removed with the gutta-percha. Some authors suggest that gutta-percha should be removed with heat techniques only and mechanical removal only used if heat is insufficient.
Mechanical Method
This is most commonly used technique. But, it is a technique that can result in damage to tooth tissue and periodontal apparatus. When using mechanical method care should be taken not to weaken the tooth or perforation. Recent studies have proved that combination of the heat and the mechanical method is superior. H-files are commonly used (Figs 25.29 and 25.30). Sometimes gates glidden drills and Peeso reamers are also used. Recently rotary instruments such as Profiles, Protaper retreatment files, K3 files and lasers are being used for gutta percha removal. Heat liberated during rotary removal may damage the periodontium.
This is most commonly used technique. But, it is a technique that can result in damage to tooth tissue and periodontal apparatus. When using mechanical method care should be taken not to weaken the tooth or perforation. Recent studies have proved that combination of the heat and the mechanical method is superior. H-files are commonly used (Figs 25.29 and 25.30). Sometimes gates glidden drills and Peeso reamers are also used. Recently rotary instruments such as Profiles, Protaper retreatment files, K3 files and lasers are being used for gutta percha removal. Heat liberated during rotary removal may damage the periodontium.
Removal of Silver Points
Can be bypassed or removed depending on canal anatomy. If the operator bends or leaves the excess of silver cone, it can be removed easily either by using Steiglitz forces, microsurgical forceps or Caufield elevator tips. Ultrasonic vibrations can be applied to loosen the silver point from the sealer
A space is made by working around the point and retrieval is accomplished by twisting multiple H-files in clockwise rotation and subsequent removal. Cancelier tubes or hypodermic needle can be used with superglue (cyanoacylate) and subsequent removal.
Can be bypassed or removed depending on canal anatomy. If the operator bends or leaves the excess of silver cone, it can be removed easily either by using Steiglitz forces, microsurgical forceps or Caufield elevator tips. Ultrasonic vibrations can be applied to loosen the silver point from the sealer
A space is made by working around the point and retrieval is accomplished by twisting multiple H-files in clockwise rotation and subsequent removal. Cancelier tubes or hypodermic needle can be used with superglue (cyanoacylate) and subsequent removal.
Removal of Pastes and Cements
Soft-setting pastes. Soft-setting pastes may be penetrated with files using crowndown method to remove the paste from the entire canal.
Hard-setting cements. Resin-type cements should be removed using solvents like tetrachlorethylene, xylene, eucalyptol, or eugenol. Once softened, the cement is managed like soft-setting pastes. If not, the cement is broken down with moderate ultrasonic vibration, using special pointed tips under light apical pressure to prevent perforation.
POST REMOVAL
Advent of dual cure resin cements led to increased bonding between post material and tooth structure.
Various post removal systems are:
1. Roto-Pro Bur
2. Thomas screw post removal kit
3. Gonon post removal system
4. Eggler's post removal system
5. Ruddle's post removal system
Roto-Pro Bur (Ellman International,Helwett,NY) (Fig. 25.31)-Available in four shapes. Six sided instrument with non cutting tip. Used in a high speed handpiece. When non-cutting flutes come in contact with the post, vibrations are created leading to subsequent loosening and removal of the post. When used in a high speed air driven handpiece, they will produce rotary ultrasonics of about 20,000 vibrations per second.
Thomas Screw Post Removal Kit
This system is designed for active or screwed posts. It has trephine burs and extraction mandrels. The mandrels are reverse threaded to tap onto the screwed post in anti-clockwise manner.
Gonon Post Removal System (Gonon master post extractor) (Fig. 25.32)
This is an improved, stainless steel extractor in a kit, specially designed for removing whole or broken posts inside the root canal in three easy steps. The extractor may be used on posts made of steel, gold, and stainless steel.The kit contains four special counter-clockwise mandrels. The kit contains a Pointer drill, four trephine burs sized 1.15 mm to 1.60 mm, four tubular taps, four CCW taps, set of washers, and pliers with screw knob. Screw post removal is easy and successful with this system.
This is an improved, stainless steel extractor in a kit, specially designed for removing whole or broken posts inside the root canal in three easy steps. The extractor may be used on posts made of steel, gold, and stainless steel.The kit contains four special counter-clockwise mandrels. The kit contains a Pointer drill, four trephine burs sized 1.15 mm to 1.60 mm, four tubular taps, four CCW taps, set of washers, and pliers with screw knob. Screw post removal is easy and successful with this system.
Eggler's Post Removal System
In Eggler system, the core must first be shaped so that its sides are parallel and capable of being gripped. The mesial and distal shoulders of the crown preparation must be cut to the same height so there is no torsional force. The post extractor is then placed over the post and the screw tightened onto the core; the feet are then lowered on to the shoulders of the preparation by turning the end knob. Several more turns will ease the post out of the post hole.
In Eggler system, the core must first be shaped so that its sides are parallel and capable of being gripped. The mesial and distal shoulders of the crown preparation must be cut to the same height so there is no torsional force. The post extractor is then placed over the post and the screw tightened onto the core; the feet are then lowered on to the shoulders of the preparation by turning the end knob. Several more turns will ease the post out of the post hole.
Ruddle's Post Removal System
In this system, a trephine is used to produce a parallel side in the post, which is then grasped in a matching sized thread cutting tap to a maximum depth of 3 mm. The post removal pliers are placed over a rubber cushion, and gently tightened. If removal is difficult, further ultrasonic energy may be applied. As with all such instruments, there is a danger of root fracture, and expertise should be gained in a technical laboratory before attempting these techniques in a clinical situation.
In this system, a trephine is used to produce a parallel side in the post, which is then grasped in a matching sized thread cutting tap to a maximum depth of 3 mm. The post removal pliers are placed over a rubber cushion, and gently tightened. If removal is difficult, further ultrasonic energy may be applied. As with all such instruments, there is a danger of root fracture, and expertise should be gained in a technical laboratory before attempting these techniques in a clinical situation.
REMOVAL OF ESTHETIC POSTS
Various post removal burs for the esthetic post systems are:
1. Largo bur
2. Gyro tip (plasma coated silicon carbide)
Various post removal burs for the esthetic post systems are:
1. Largo bur
2. Gyro tip (plasma coated silicon carbide)
It is difficult to remove ceramic and zirconia posts. Ceramic posts can be drilled with diamond with high risk of perforation, but Zirconia post is almost impossible to retrieve.
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