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Removal of failed implant

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发表于 2018-9-16 19:38:12 | 显示全部楼层 |阅读模式
Implant restoration has become one of the routine treatment methods to repair dentition defect or missing. Like other medical techniques, it also has the possibility of failure. The factors of implant failure involve many aspects, such as the operation technique of the clinician, the implant condition of the patient, the implant material and so on. Doctor-related factors include osteonecrosis caused by excessive heat production during cavity preparation, intraoperative contamination, failure to select the correct implant type, and failure to implant the correct three-dimensional position. Factors related to patients include bruxism, bad occlusion habits, and poor oral hygiene. Others, such as smoking, radiation therapy and diabetes, will have some effect.

When doctors and patients can not accept the effect of repair, implant mechanical damage or fracture, because of peri-implant inflammation without retaining significance, the need to remove the implant. For implants without osseointegration, such as implant loosening due to failure of early osseointegration, or implant loosening due to peri-implant inflammation, the implant can be clamped with tongs or torque wrenches and rotated. Surgical intervention is often needed in the removal of implants that have failed in the late stages of osseointegration, such as abnormal occlusion, implant structure or implant overload.

At present, the common methods of removing osseointegrated implants are counter torque ratchet techniques (CTRT), ultrasonic osteotomy, high-speed drill grinding, annular drill osteotomy, laser osteotomy and so on.
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 楼主| 发表于 2018-9-16 19:38:36 | 显示全部楼层
1. CTRT

CTRT refers to the anti-clockwise rotation of the implant with high torque, which is one of the methods to minimize the damage to the implant-bone interface. The CTRT tool consists of 3 components: screw in the dismantling screw of the implant, the extractor and the torque wrench. The torque wrench has two torque meters, one measuring the torque when the screw is screwed into the implant and the other measuring the final torque when the implant is screwed out. The tool box is suitable for multiple planting systems, and is a universal suit. The screw is first clockwise screwed into the implant, locked (maximum torque 60 N. cm), selected the appropriate diameter and length of the extractor according to the implant, the extractor is rotated counterclockwise and locked, then the implant is rotated out with a torque wrench, the maximum torque can reach 500 N. cm. However, when the torque wrench is too large, the implant is fine or the bone is hard, the implant may fracture during the process of rotation; therefore, in the removal of more bone-bonded implants, invasive methods should be used to remove the bone in the implant crown, so that the implant loosened or the torque is reduced, and then the ratchet wrench should be used to rotate the implant. Out.

2. ultrasound bony knife

The ultrasonic scalpel can transform electrical energy into mechanical energy and produce mechanical vibration to produce cutting action. The vibration frequency is 24~36 kHz. Only cutting hard tissue will not damage soft tissue, such as nerve and blood vessels. A large amount of cooling saline should be given to reduce the thermal damage of bone tissue during ultrasonic osteotomy. Snke et al. cut bovine femur with three kinds of commonly used ultrasonic bone knife and measured the temperature at the cutting site. The results showed that the median increase of temperature was 3.0, 2.2, and 1.1 degrees C, respectively, which did not cause osteonecrosis. In addition, the ultrasonic bone knife cutting surface is more fine, and a variety of specifications and models of drill can be selected, in the cutting can be controlled accurately; the use of ultrasonic bone knife postoperative bleeding is less, tissue healing faster. Ultrasound osteotomy is an optional method for removing bone tissue around the implant, but it takes longer than conventional instruments.

Rahnama et al. reported a case of implant in the lower anterior teeth area which invaded the soft tissue of the base of the mouth due to misplacement. Three months after implantation, the patient was treated again for dyspnea and pain. The implant was removed by ultrasonic osteotomy. No complications such as infection, bleeding and swelling occurred and the bone around the implant was preserved to the maximum extent. It reduces the damage to surrounding soft tissue.
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 楼主| 发表于 2018-9-16 19:38:55 | 显示全部楼层
3. round bone drill

When using an annular bone drill to remove the implant, the number of the circular bone drill should be chosen according to the diameter of the implant. The inner diameter of the ring drill should be slightly larger than the implant diameter to avoid damage to the implant, but also should not be too large to avoid damage to the surrounding bone or teeth. The circular bone drill is a relatively large method to remove the implant. Marini et al reported that 1 patients suffered from mandibular fracture after the use of an annular bone drill. When the drill is used, it produces more heat and is prone to osteomyelitis, so it should be washed with a large amount of cooling saline during the use. When the implant is removed, the bone around the crown of the implant can be removed with a ring-shaped bone drill to loosen the implant, and then the implant can be screwed out with forceps or ratchet wrenches. Some scholars reported that 14, 15 and 16 implants were broken because of the occlusal force. The broken end of the implant was 1-2 mm below the ridge of the alveolar ridge. A small amount of bone around the upper part of the residual implant was removed with a ring-shaped bone drill. The implant was pulled out by minimally invasive extraction in the near to middle and far places. After the implant was loosened, the implant was clamped out with a residual root forceps. There were obvious bone defects on the buccal side of the removal site.

4. high speed drill bit

It is more efficient to use high-speed bits to grind bone around the osseous implants. After removing the base and implant neck structure, one-half of the implant neck bone can be ground out first, and then the implant can be turned out with a ratchet wrench. It has been reported that the bone around the fractured implant was carefully ground with a high-speed fine drill. After careful removal of the implant, the same type of implant was implanted immediately, and the bone powder and collagen membrane were covered. After 6 months, the implant bonded well. Li et al. Reported a new method of using high-speed handsets to remove implants. A positioning groove of 2-3 mm depth was ground in the center of the implant with a diamond drill. The groove was then grinded along with a carbon drill to the edge of the implant. After the implant was loosened with a stiffener, the groove was removed with a pliers. The particles produced during the grinding process should be washed clean. Leon et al showed that particles attached to bone and soft tissue did not cause significant damage.

D ngel reported that the air of high-speed mobile phones may cause subcutaneous emphysema. Especially when the implant is in the mandible, the air in the mobile phone can cause emphysema in the pterygomandibular space through the posterior molar space. Parapharyngeal space air can lead to eustachian tube dysfunction, which may lead to hearing loss, dysphonia and dysphagia. When the high-speed mobile phone drill is used to grind the apical part of the implant, the damage to important anatomical structures (such as the maxillary sinus floor, mandibular nerve canal and chin foramen) should be avoided.
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 楼主| 发表于 2018-9-16 19:39:14 | 显示全部楼层
5. laser

Laser has the ability of efficient cutting, and it can also protect tissues and prevent tissue from overheating. Smith et al. reported that one case of cervical bone resorption due to peri-implant inflammation without significant implant removal was treated with laser. The patient was followed up 2 days, 1 week and 6 weeks after surgery without complaints of pain or other discomfort. Kimura et al. reported that Er, Cr: YSGG laser can effectively cut bone tissue without causing necrosis, melting or changes in calcium-phosphorus ratio.

Histological study showed that the thermal damage of laser with wavelength 2.78 micron, frequency 20 Hz and power 2 W was 30 micron in soft tissue and 80 micron in bone tissue, indicating that the thermal damage of laser was small and limited to a few microns at the edge of the incision. Er:YAG laser irradiation can accelerate the healing rate of bone tissue, which may be due to the typical irregular morphology of the surface of bone tissue after laser irradiation, which increases the adhesion of blood components to bone tissue at the early stage of healing. In addition to the above methods of implant removal, Massei et al. tried to stimulate the implant with a 27MHz high frequency electric knife for 3 seconds. After 2 weeks, the implant could be rotated with a torque of 15-50 N.cm. Histological sections showed only partial osteonecrosis, which was confined to the implant-bone interface within 50 microns. This experiment provides a new idea and method for the removal of osseointegrated implants, but only one case is reported, which needs further study.
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