|Year : 2011 | Volume
| Issue : 1 | Page : 22-25
Removal of a dental implant: An unusual case report
Joanne Cunliffe, Craig Barclay
Department of Restorative Dentistry, Manchester Dental Hospital, Manchester, United Kingdom
|Date of Web Publication||2-Feb-2011|
Manchester Dental Hospital, Higher Cambridge Street, Manchester
| Abstract|| |
This article is a case report of removal of a dental implant using electrosurgery. A discussion will outline a possibly less invasive method to remove the dental implant. This involves the use of electrosurgery unit to cause a thermo-necrosis of the bone and therefore a weakening of the bone-implant interface. It is suggested that a controlled laboratory experiment be carried out to look at the effects of mono-polar electrosurgery on osseointergration on dental implants and the possible use of this method to allow for simple removal of poorly positioned fixtures and also fixtures with significant bone loss but no mobility.
Keywords: Dental implant, electrosurgery, removal
|How to cite this article:|
Cunliffe J, Barclay C. Removal of a dental implant: An unusual case report. J Dent Implant 2011;1:22-5
| Introduction|| |
Implant-supported restoration has been shown to be a predictable treatment for tooth replacement.  Implant survival rates for dental implants are high, as are success rates.  True implant success rates, however, are lower due to various features including incorrect positioning. Failure of implants can be split into early failure due to failure to integrate; and late failure due to bone loss or loss of integration. There are various causes related to early failure which can include overheating, contamination and trauma during surgery, poor bone quantity and/or quality and lack of primary stability. Late implant failure can be caused by peri-implantitis, occlusal trauma and overloading, although most failure is multi-factorial. Marginal bone loss could also put implant survival at risk in the long-term.
In 1986, Albrektsson et al.  looked at success criteria for bone loss and suggested that during the first year after abutment connection, 1 mm of bone loss is acceptable followed by 0.2 mm per year. These criteria are still frequently referred to as the "gold standard" for implant success; however, this gold standard is currently being re-evaluated based on new implant surfaces and designs (Wennerberg 2009).  In addition to biological failure, an implant may also require removal due to its poor restorative position or the implant may be impinging on an anatomical structure. There may also be a need to remove dental implants that have been used in orthodontics as an aid to anchorage.
To remove dental implants, the use of trephines, bone chisels or peizosurgery are commonly employed. These methods can be not only destructive, in terms of bone loss but also have significant morbidity and can leave large voids in the bone which may cause subsequent problems. This bony defect may be too large to allow the placement of another dental implant if this is required. There also may be problems if neighbouring teeth or anatomical structures are too close to the trephine margin. This situation may then lead to further surgery for the patient, in the form of bone grafts.
In this case report, a discussion will outline a possibly less invasive method to remove the dental implant. This involves the use of electrosurgical mono-polar unit to cause a thermo-necrosis of the bone and therefore a weakening of the bone-implant interface.
| Case Report|| |
A 19-year-old woman attended for the uncovering of an dental implant (4 Χ 15 mm Astra Osseospeed) in the upper left central incisor region. The implant had been placed six months previously, into a region of a chin block graft. When the implant was uncovered, it was evident that it was not in a favorable position and was unrestorable. The implant was placed too coronally [Figure 1] and far too retroclined [Figure 2]. In order to replace the upper left central incisor with a new implant, the original implant needed to be removed. It was obvious clinically that the poor position had probably resulted from a lack of grafted bone in an ideal implant bed site, and if the implant were trephined out, there would be considerable bone removal and potential damage to neighbouring teeth. There would also be a risk of perforation of the nasal floor as this was very close to the apex of the implant. A conservative method of removal of the implant was necessary. A full thickness flap was reflected and the cover screw was removed from the fixture. This area was carefully isolated and the mucosa retracted clear from the field. An ultra high frequency mono-polar, electro-surgery unit was then applied to the internal surface of the neck of the implant to cause a thermo-necrosis at the bone-implant interface [Figure 3], and a 15-second impulse was delivered to the titanium implant.
After one week, the patient returned and was anesthetized. The buccal mucosal flap was reflected and the implant was removed with the aid of the torque wrench used in reverse [Figure 4]. The force to remove the implant only required the use of the hand wrench and therefore was below 30 N. As can be seen from [Figure 5], there was very little bone destruction and no evidence of macroscopic necrosis. There was clear bleeding from the bone interface and the osteotomy bed was curetted thoroughly and the bleeding socket covered with - Bio-Gide [Figure 6]. The patient was then left for a ten-week period. A radio-opaque stent was constructed with the ideal tooth position, and a cone-beam CT scan was taken to assess the position and volume of bone present in this site. The patient subsequently had the area debrided, a ramus graft was placed and a delayed implant and connective tissue graft procedure was carried out.
| Discussion|| |
Removal of implants for revision can be destructive if more bone needs to be removed. This can then pose a problem when it comes to re-treatment. This method proved to be less destructive and was used on 20 dental implants that required revision. It proved to be an efficient method of implant removal. 
The concern with using electro-surgery on dental implants is the risk of osteonecrosis. Reports of mucosal and osseous necrosis have been recorded. , In the classic study by Eriksson and Albrektsson, they established that "bone tissue is sensitive to heating at the level of 47°C." They further stated that greater injury occurred after heating tissue to 53°C for 1 minute, and that "heating to temperatures of 60°C or more resulted in obvious bone tissue necrosis".  At 56°C alkaline phosphatase denatures. 
Two types of electro-surgical units are available: mono-polar and bi-polar. Both types are used extensively in medicine but only mono-polar systems tend to be used in dentistry (except for the use of bi-polar units by oral surgeons).
Mono-polar systems are characterized by an active electrode used for incision or coagulation and a second "grounding" electrode placed in contact with the patient at a site remote from the incision or coagulation. Bi-polar systems also deliver a high-frequency current to the tissue via the active electrode but the "grounding'' electrode is always close to the active electrode.
Electro-surgical units typically operate at one fixed frequency predetermined by the manufacturer. The mono-polar unit, however, is more effective than bi-polar for cutting action and possesses advantages over bi-polar for this objective. 
In a study in dogs, Krejci et al. looked at the pulpal response to electro-surgical contact with Class V amalgam restorations. They concluded that contacts of less than 0.4 second produced no change in pulpal histology. Conversely, when contacts exceeded 0.4 second, histologic changes occurred in the majority of pulps. Mono-polar systems are characterized by an active electrode applied to the site intended for incision or coagulation and a second "grounding" electrode (usually in the form of a pad) which is placed in contact with the patient on a site remote from the incision or coagulation.
There is little research on the effects of electro-surgery and dental implants, but Wilcox et al. looked at the cumulative effect of temperature change in bovine bone when using electro-surgery and lasers to uncover dental implants. The bi-polar unit produced no cumulative temperature gains greater than 5°C, while the mono-polar electrosurgical units regularly produced cumulative temperature gains exceeding 10°C. They concluded that the "use of the uni-polar electro-surgical unit should be avoided, while judicious use of both the bi-polar unit and the laser unit should produce temperature profiles well within clinical limits". If the tip comes into contact for longer periods, then there may be an increase over the 10°C threshold which may lead to tissue damage.
Heating tissue with radio-frequency energy uses these mechanisms of energy absorption in two distinct ways: Ohmic heating and di-electric heating. Ohmic heating, dominant below 500MHz, increases the translational motion of the affected particles in tissue. Ohmic heating is the mechanism of tissue heating by electrosurgical devices.  Electro-surgery destroys tissue in two patterns: boiling and coagulation. If tissue is heated rapidly, the cellular water boils and steam is formed and the cells burst, forming steam and cellular debris. If tissue is heated slowly, cellular proteins coagulate before the water boils. The tissue turns white, and slowly desiccates, and if current application continues, eventually the tissue will char, forming carbon and smoke. This effect is similar to heating the albumin of an egg.  The rate of energy delivered to a given mass of tissue from electro-surgical devices can be controlled in three ways:
- Changing the power output of the device.
- Changing the amount of time the energy is applied to the tissue.
- Changing the cross-sectional area of application.
In addition, the depth of heating is a function of power output level and duration of power application. The size of the tip will affect the cross-sectional area of the applied energy by concentrating the current at a very fine point, if a wire is used. The devices maximize the concept of current density, and a lower power output may be used to achieve desired effects because less tissue is heated than with a larger application device. There may be less collateral damage. 
Alveolar bone volume after the removal of a failed implant could undergo a continuous remodelling process particularly in early phases.  It has been proposed that in order to reduce this, an immediate implant is placed. A study by Covani  suggested that "implants placed immediately after implant removal due to biomechanical fracture could be performed with results that are similar to results obtained with implants placed immediately after tooth extraction". In this case, the implant was not placed immediately as there was not enough bone to place the implant in the correct position. In addition, there was a concern that the area should heal and remodel due to the potential of a small amount of necrotic bone.
The purpose of the membranes used was to isolate the socket from soft tissues, thus preserving the space and aiding bone healing. It should be kept in mind, however, that the use of barrier membranes is not free from clinical problems: membrane exposures with frequencies ranging from 8% to 100% have been observed.  This can lead to infection and more bone loss.
| Conclusion|| |
It is suggested that a controlled laboratory experiment be carried out to look at the effects of mono-polar electro-surgery on osseo-integration in dental implants and the possible use of this method to allow for simple removal of poorly positioned fixtures and also fixtures with significant bone loss but no mobility.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]