Authors: Dr. Rathika Rai, Dr. Manesh Lahori, Dr. Prerna Kaushik.
K.D. Dental College & Hospital, Mathura, INDIA
Introduction:
The use of dental implants in the treatment of total or partial edentulism has demonstrated a high degree of success, with documented survival rates of 90-97%.
Although osseointegrated implants have high survival rates, failures do occur.
The first-year failure rate for dental implants ranges from 3-8%. The global failure rate for dental implants has been reported to be between 2-9%. An annual loss of 1% after the first year in function was also reported. An estimated 200,000 to 250,000 implants are likely to fail annually worldwide.
Various techniques have been evolved to remove implants each having its own pros and cons
Etiology:
Implant failure can have a multifactorial etiology, usually divided into:-
EARLY FAILURE
LATE FAILURE
Causes related to early failure include:
1. Overheating of the bone during osteotomy preparation
2. Overpreparation of the osteotomy
3. Implant contamination during surgery
4. Poor bone quality
5. Lack of primary stability
6. Macro-motion caused by overload or parafunction.
Implants with such aetiologies are usually mobile, and early removal is easily performed.
Causes of Late failure include
Methods of implant removal include :-
Considerations for implant removal are as follows:
Mobile implant—complete loss of bone-to-implant contact.
A mobile implant may easily be removed by rotating it counter-clockwise using a driver, counter-torque ratchet, or forceps. Rotating with minimum luxation allows reduced trauma and damage to the surrounding bone and soft tissue.
Immobile implant—partially or fully osseointegrated.
Methods of immobile implant removal include: use of counter- torque ratchets, screw removal devices, piezo tips, high-speed burs, elevators, forceps, and trephine burs.
1. Counter-Torque Ratchet Technique (CTRT)
CTRT is the least invasive technique for removing an implant without damaging surrounding structures.
Cases amenable to removal with CTRT depend on :
Care must be taken with narrow-diameter implants that are < 4 mm in dense cortical bone to avoid implant fracture.
The reverse screw technique (RST) is another less invasive method that uses a screw removal device. RST is indicated in the removal of a fractured implant when the connection is damaged or in the removal of an external connection implant when the ratchet cannot be engaged to use the CTRT
Considerations for Use of CTRT and RST…
Although use of the counter-torque ratchet is the least invasive method regarding damage to the surrounding structures, considerations for implant removal utilizing this technique include the following:
A. Type of Implant Connection
An external hex implant requires an adapter when removing the implant via the CTRT.
An internal connection implant is much easier to remove since it connects directly to internal connector and the connection is more rigid .
However, complications may occur when removing an implant with an internal trilobe connection using the counter-torque ratchet. The neck portion of this type of implant, especially those with smaller diameters (ie, 3.5 mm), has been observed to fracture during removal procedure if the reverse torque is more than 45 Ncm.
B. Implant Diameter
When the outer diameter of an implant increases by 0.1 mm and the inner diameter remains unchanged, the moment of inertia increases to 30% in strength.
When the outer diameter remains unchanged and the inner diameter decreases by 0.1 mm, there is an increase of 16% in strength.
Therefore, an increase in the outer diameter has a more significant effect on body wall strength . Thus when a narrow-diameter implant (< 4 mm) is removed, an excessive torque force must be avoided in order to prevent complications such as implant fracture.
C. Implant Geometry: Thread Shape and Depth
Thread shapes in dental implants include buttress, square, V-shape, and reverse buttress.
The V-shaped and reverse buttress threads have similar bone-to-implant contact (BIC) as well as reverse-torque values.
The square thread design has a higher BIC and greater reverse-torque test value.Therefore, a square design may be significantly more difficult to remove by the reverse-torque technique and may require high values with a CTRT, it may also be an indication for a combination removal technique.
A tapered implant has less implant-to-bone contact in the apical region and is, therefore, easier to remove with a more conservative technique.
Some implant systems have an anti-rotational feature, which is usually incorporated into the implant body in the apical region. The most common design employs a hole or vent. In theory, bone can grow through the apical hole and resist rotational loads applied to the implant. These implants may require use of a trephine or bur to cut to the apex to severe the bone attachment and remove the implant if the implant is not rotated with the CTRT or RST.
D. Implant Location (Bone Quality)
Functional surface area plays a major role in addressing the variable initial BIC zones related to bone density upon initial loading.
The densest bone (D1 bone) has the stiffest modulus of elasticity and the highest initial BIC (approximately 80%).There are progressively decreasing percentages of bone at the initial implant interfaces with D2, D3, and D4 bone.
The weakest biomechanical strength and the lowest BIC (25%) area to dissipate the load at the implant–bone interface are found with D4 bone.
In many cases of D4 bone, removing the bone circumferentially in order to get enough implant exposure for the rongeur placement is sufficient to enable unscrewing of the implant.
When dealing with a narrow-diameter immobile implant in dense bone (D1 or D2),care should be taken while using the reverse-torque technique to avoid exceeding the recommended insertion torque and prevent the fracture of the implant connection.
2. Piezo Tips
Piezo tips allow for better intra operative control during bone-cutting because they prevent damage to the surrounding soft tissue. Furthermore, the bone healing response following piezoelectric surgery seems to be more favorable than osteotomies performed with burs.
However, when deep cuts into bone are necessary, the device is less efficient, and when the cutting speed is decreased the tip's temperature rises.
Thus, it is necessary to pause several times during the removal procedure to let the tip cool down; also, the use of copious irrigation with cold saline is recommended.
3. High-Speed Burs
The use of high-speed burs under copious irrigation is an efficient method to remove a failed implant.
Usually a long, thin diamond bur is preferred over a carbide bur, because the diamond bur is easier to control and produces a more efficient, thinner cut. Cuts should be made using high-speed burs and copious irrigation on the mesial and distal aspects of the implant to prevent damage to the buccal plate of bone.
Oftentimes this is sufficient to loosen the implant and remove it with the CTRT or RST.
PRECAUTIONS:
When using high-speed burs, the residual apical part of the implant should be carefully approached in order to prevent damage to anatomical structures such as the sinus floor, inferior alveolar nerve, and mental foramen.
Air from the high-speed handpiece can be forced into a surgical wound or a laceration in the mouth causing an air embolism.
Particles of the implant surface that may enter the healing wound ,should be removed as part of the procedures.
When the implant is in close proximity to a vital structure before using the burs, accurate radiographs and a computer axial tomographic (CAT) or cone beam (CB) scan is recommended to locate anatomical structures.
4. Trephine Burs
Several sizes of trephines are available corresponding to various implant diameters .The smallest effective size trephine should be selected to avoid collateral damage to the neighboring bone, teeth, and/or implants.
The internal diameter of the trephine needs to be slightly larger than the implant to avoid engaging the implant body.
The preferred speed to use a trephine is 1,200 rpm to 1,500 rpm with copious irrigation.
This is one of the most invasive options for implant removal.
Fatigue fracture of the mandible after the use of a trephine bur has been reported.
Osteomyelitis may occur particularly if bone is overheated.
Thus, trephine burs are only indicated when absolutely necessary, and the retrieval procedure should be carefully planned and performed under copious irrigation with cooled saline.
5. Combination Techniques
When an integrated implant cannot be removed with less invasive methods, the piezo tips and/or drill are used to remove sufficient supporting bone around the coronal parts of the implant, and the counter-torque ratchet or forceps are then employed to remove the implant to reduce damage to the surrounding bone.
To assure implant removal without fracture, the reverse-torque technique with a counter-torque ratchet is recommended at the lowest torque values first.
If there is no movement, a bur or trephine can be used to cut through the surrounding cortical bone and into the trabecular bone.
The reverse-torque technique is then attempted again. The goal is to preserve the remaining bone as much as possible. Alternating between the counter-torque ratchet and the elevator and occasionally drilling with the bur or trephine can then be used in combination to remove the implant
DISCUSSION:
After removing a failed implant, the placement of an immediate replacement implant is often dependent on the amount of residual bone. Several authors have stated that guided bone regeneration (GBR) procedures are unnecessary for four-wall socket sites with no fenestrations or dehiscences and a gap distance < 2 mm between implant surface and surrounding bone walls.
However, if the implant socket site contains less than three walls, use of the GBR procedure as well as knowledge of the classification of the extraction socket type is helpful in treatment-planning for the augmentation of the bony defect.
In any event, preservation of the bone during removal of the implant can help avoid or reduce the necessity of augmentation procedures to promote implant placement. This is essential because the literature suggests that replanted implants may have a decreased survival rate.
REVIEW OF LITERATURE:
Removal of Dental Implant - An insight
K.D. Dental College & Hospital, Mathura, INDIA
Introduction:
The use of dental implants in the treatment of total or partial edentulism has demonstrated a high degree of success, with documented survival rates of 90-97%.
Although osseointegrated implants have high survival rates, failures do occur.
The first-year failure rate for dental implants ranges from 3-8%. The global failure rate for dental implants has been reported to be between 2-9%. An annual loss of 1% after the first year in function was also reported. An estimated 200,000 to 250,000 implants are likely to fail annually worldwide.
Various techniques have been evolved to remove implants each having its own pros and cons
Etiology:
Implant failure can have a multifactorial etiology, usually divided into:-
EARLY FAILURE
LATE FAILURE
Causes related to early failure include:
1. Overheating of the bone during osteotomy preparation
2. Overpreparation of the osteotomy
3. Implant contamination during surgery
4. Poor bone quality
5. Lack of primary stability
6. Macro-motion caused by overload or parafunction.
Implants with such aetiologies are usually mobile, and early removal is easily performed.
Causes of Late failure include
- Peri-implantitis
- Occlusal trauma
- Implant fracture
- Implant overload
Methods of implant removal include :-
- Counter-torque ratchet
- Piezo tips
- High-speed burs
- Elevators
- Forceps
- Trephine burs
Considerations for implant removal are as follows:
Mobile implant—complete loss of bone-to-implant contact.
A mobile implant may easily be removed by rotating it counter-clockwise using a driver, counter-torque ratchet, or forceps. Rotating with minimum luxation allows reduced trauma and damage to the surrounding bone and soft tissue.
Immobile implant—partially or fully osseointegrated.
Methods of immobile implant removal include: use of counter- torque ratchets, screw removal devices, piezo tips, high-speed burs, elevators, forceps, and trephine burs.
1. Counter-Torque Ratchet Technique (CTRT)
CTRT is the least invasive technique for removing an implant without damaging surrounding structures.
Cases amenable to removal with CTRT depend on :
- An intact implant connection (external hex, internal hex),
- Implant diameter,
- Implant geometry,
- Implant location (bone quality),
- The amount of osseointegration remaining.
Care must be taken with narrow-diameter implants that are < 4 mm in dense cortical bone to avoid implant fracture.
The reverse screw technique (RST) is another less invasive method that uses a screw removal device. RST is indicated in the removal of a fractured implant when the connection is damaged or in the removal of an external connection implant when the ratchet cannot be engaged to use the CTRT
Considerations for Use of CTRT and RST…
Although use of the counter-torque ratchet is the least invasive method regarding damage to the surrounding structures, considerations for implant removal utilizing this technique include the following:
A. Type of Implant Connection
An external hex implant requires an adapter when removing the implant via the CTRT.
An internal connection implant is much easier to remove since it connects directly to internal connector and the connection is more rigid .
However, complications may occur when removing an implant with an internal trilobe connection using the counter-torque ratchet. The neck portion of this type of implant, especially those with smaller diameters (ie, 3.5 mm), has been observed to fracture during removal procedure if the reverse torque is more than 45 Ncm.
B. Implant Diameter
When the outer diameter of an implant increases by 0.1 mm and the inner diameter remains unchanged, the moment of inertia increases to 30% in strength.
When the outer diameter remains unchanged and the inner diameter decreases by 0.1 mm, there is an increase of 16% in strength.
Therefore, an increase in the outer diameter has a more significant effect on body wall strength . Thus when a narrow-diameter implant (< 4 mm) is removed, an excessive torque force must be avoided in order to prevent complications such as implant fracture.
C. Implant Geometry: Thread Shape and Depth
Thread shapes in dental implants include buttress, square, V-shape, and reverse buttress.
The V-shaped and reverse buttress threads have similar bone-to-implant contact (BIC) as well as reverse-torque values.
The square thread design has a higher BIC and greater reverse-torque test value.Therefore, a square design may be significantly more difficult to remove by the reverse-torque technique and may require high values with a CTRT, it may also be an indication for a combination removal technique.
A tapered implant has less implant-to-bone contact in the apical region and is, therefore, easier to remove with a more conservative technique.
Some implant systems have an anti-rotational feature, which is usually incorporated into the implant body in the apical region. The most common design employs a hole or vent. In theory, bone can grow through the apical hole and resist rotational loads applied to the implant. These implants may require use of a trephine or bur to cut to the apex to severe the bone attachment and remove the implant if the implant is not rotated with the CTRT or RST.
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 |
 |
| Figure-1. COUNTER TORQUE RATCHET |
Figure-2. REVERSE SCREW |
Figure-3. DECISION MAKING FOR AN HOPELESS IMPLANT |
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 |
 |
| Figure-4. IMPLANT CONNECTION RELATION TO IMPLANT REMOVAL |
Figure-5. PIEZO TIPS |
Figure-6. USE OF A HIGH SPEED BUR |
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 |
|
Figure-7. USE OF A TRAPHINE BUR |
Figure-8. PUBLISHED LITERATURE OF IMPLANT REMOVAL TECHNIQUE |
Figure-9. COMPARISON OF METHODS FOR IMPLANT REMOVAL |
D. Implant Location (Bone Quality)
Functional surface area plays a major role in addressing the variable initial BIC zones related to bone density upon initial loading.
The densest bone (D1 bone) has the stiffest modulus of elasticity and the highest initial BIC (approximately 80%).There are progressively decreasing percentages of bone at the initial implant interfaces with D2, D3, and D4 bone.
The weakest biomechanical strength and the lowest BIC (25%) area to dissipate the load at the implant–bone interface are found with D4 bone.
In many cases of D4 bone, removing the bone circumferentially in order to get enough implant exposure for the rongeur placement is sufficient to enable unscrewing of the implant.
When dealing with a narrow-diameter immobile implant in dense bone (D1 or D2),care should be taken while using the reverse-torque technique to avoid exceeding the recommended insertion torque and prevent the fracture of the implant connection.
2. Piezo Tips
Piezo tips allow for better intra operative control during bone-cutting because they prevent damage to the surrounding soft tissue. Furthermore, the bone healing response following piezoelectric surgery seems to be more favorable than osteotomies performed with burs.
However, when deep cuts into bone are necessary, the device is less efficient, and when the cutting speed is decreased the tip's temperature rises.
Thus, it is necessary to pause several times during the removal procedure to let the tip cool down; also, the use of copious irrigation with cold saline is recommended.
3. High-Speed Burs
The use of high-speed burs under copious irrigation is an efficient method to remove a failed implant.
Usually a long, thin diamond bur is preferred over a carbide bur, because the diamond bur is easier to control and produces a more efficient, thinner cut. Cuts should be made using high-speed burs and copious irrigation on the mesial and distal aspects of the implant to prevent damage to the buccal plate of bone.
Oftentimes this is sufficient to loosen the implant and remove it with the CTRT or RST.
PRECAUTIONS:
When using high-speed burs, the residual apical part of the implant should be carefully approached in order to prevent damage to anatomical structures such as the sinus floor, inferior alveolar nerve, and mental foramen.
Air from the high-speed handpiece can be forced into a surgical wound or a laceration in the mouth causing an air embolism.
Particles of the implant surface that may enter the healing wound ,should be removed as part of the procedures.
When the implant is in close proximity to a vital structure before using the burs, accurate radiographs and a computer axial tomographic (CAT) or cone beam (CB) scan is recommended to locate anatomical structures.
4. Trephine Burs
Several sizes of trephines are available corresponding to various implant diameters .The smallest effective size trephine should be selected to avoid collateral damage to the neighboring bone, teeth, and/or implants.
The internal diameter of the trephine needs to be slightly larger than the implant to avoid engaging the implant body.
The preferred speed to use a trephine is 1,200 rpm to 1,500 rpm with copious irrigation.
This is one of the most invasive options for implant removal.
Fatigue fracture of the mandible after the use of a trephine bur has been reported.
Osteomyelitis may occur particularly if bone is overheated.
Thus, trephine burs are only indicated when absolutely necessary, and the retrieval procedure should be carefully planned and performed under copious irrigation with cooled saline.
5. Combination Techniques
When an integrated implant cannot be removed with less invasive methods, the piezo tips and/or drill are used to remove sufficient supporting bone around the coronal parts of the implant, and the counter-torque ratchet or forceps are then employed to remove the implant to reduce damage to the surrounding bone.
To assure implant removal without fracture, the reverse-torque technique with a counter-torque ratchet is recommended at the lowest torque values first.
If there is no movement, a bur or trephine can be used to cut through the surrounding cortical bone and into the trabecular bone.
The reverse-torque technique is then attempted again. The goal is to preserve the remaining bone as much as possible. Alternating between the counter-torque ratchet and the elevator and occasionally drilling with the bur or trephine can then be used in combination to remove the implant
DISCUSSION:
After removing a failed implant, the placement of an immediate replacement implant is often dependent on the amount of residual bone. Several authors have stated that guided bone regeneration (GBR) procedures are unnecessary for four-wall socket sites with no fenestrations or dehiscences and a gap distance < 2 mm between implant surface and surrounding bone walls.
However, if the implant socket site contains less than three walls, use of the GBR procedure as well as knowledge of the classification of the extraction socket type is helpful in treatment-planning for the augmentation of the bony defect.
In any event, preservation of the bone during removal of the implant can help avoid or reduce the necessity of augmentation procedures to promote implant placement. This is essential because the literature suggests that replanted implants may have a decreased survival rate.
REVIEW OF LITERATURE:
- Removal of a dental implant:An unusual case report,Joanne Cunliffe, Craig Barclay.Journal of dental implants. Jan-june 2011,vol 1, issue 1.
- Techniques to Remove a Failed Integrated Implant,Stuart Froum, DDS; Takuto Yamanaka, DDS; Sang-Choon Cho, DDS, MS; Roise Kelly, DDS; Stephen St. James, DDS; and Nicolas Elian, DDS Compendium of Continuing Education in Dentistry
- Thermo-explanation. A novel approch to remove osseo-integrated implants. ,Massei G, Szumkler - Moncler S.Eue Cell Mater 2004;7:48.
- Exaggerated tissue response to electro-surgery .Hall H, Williams V. Gen Dent 1988;36:303-5
- CO2 lasers and temperature changes of titanium implants.Oyester D, Parker W, Gher M. J Periodontal 1995;66:1017-24
In Association With
