A few months ago, a patient from India flew in for a consultation about his implants which was placed a year ago. He had had two dental implants done to replace his two front teeth which were fractured due to a fall. The dentist who treated him at that time had extracted the remnants of the two teeth and placed the implants immediately to support a temporary prosthesis. Over the course of the year, the bone and gums had receded upwards, exposing part of the implants. This posed a real aesthetic problem as he had a high smile line that showed the exposed implant. He requested for the implants to be removed and new implants placed to support the prosthesis. This is one of the most difficult problems to solve in implant dentistry.
The reason why the dental implant is the treatment of choice for tooth replacement is the almost permanent nature of the implant. Osseointegration, the process whereby the bone bonds with the implant with no perceptible intervening fibrous scar tissue, enables the implant to be part of the bone remodeling process that maintains healthy bony support for it. Once completed, the bone is almost fused to the implant. As such, attempts at removing such an integrated implant is like trying to remove a part of the jaw bone it self. So, how to remove an integrated dental implant?
Indeed, an implant in the aesthetic zone that is integrated in the wrong place is one of the worst complications in implant dentistry. In the case of this patient, removing the implants and starting over would give the best chance of success. However, removing an integrated implant requires removing the bone around the implant. Considering that the bone around the upper front teeth is usually barely thick enough to house an implant, removal of the bone may result in loosing all the bone. This will then necessitate significant bone and soft tissue grafting to reconstruct the alveolar bone before new implants can be placed.
The least invasive way to remove an integrated dental implant is by trephining. A trephine is a hollow drill with serrated edges. To remove a 4mm-diameter implant, a trephine with an internal diameter of 5mm is placed over the implant. The trephine is connected to a motor that rotates at about 2000 revolutions per minute. There is usually no need to apply the trephine to the full length of the implant. Removing the top 5mm of bone of a 10mm long implant is usually sufficient to weaken the bond. An implant driver can then be inserted into the implant in the same way as when an implant is first inserted, and the implant reversed out. Sometimes, even with 5mm of bone supporting the implant, reversing out is not possible. The trephine can be applied deeper to remove more bone before attempting reversion. In some cases, the implant removal can also be done like tooth extraction, using elevators and forceps, but after applying the trephine for the initial bone removal.
Implant removal is also indicated when the implant fractures. Dental implants are made of commercially pure titanium, which ranges from Grade 1 to 4, in increasing degree of strength. All are capable of withstanding biting forces over the long term once they are integrated with bone. However, if oral hygiene is poor, implants are susceptible to peri-implantitis, ie inflammation of the bone around the implant, just as natural teeth are susceptible to periodontitis. This results in bone loss originating from the part of the implant which connects to the crown. This is the part of the implant that is weakest mechanically because it is hollowed out to accommodate the abutment screw. Without external support from the bone coupled with lateral forces transmitted by the abutment screw may cause the implant to fracture.
A fractured implant is even more difficult to remove because unlike the earlier example, there is no exposed implant sticking out for the trephine to go over. Bone has to be trimmed to expose the retained part of the broken implant before the trephine can be applied. Furthermore, the broken end does not have an engaging part for a driver to be connected for reversion and can only be drilled and elevated like a broken tooth.
As the implant removal entails removing a lot of bone, due consideration must be given to whether there is sufficient bone remaining for a replacement implant. When the bone is insufficient, multiple stages of bone and soft tissue grafting may be needed over a period of several months or even more than a year. Reconstructive surgery is not always an exact science and revisions to initial surgeries may be needed to create an aesthetic result. The alternative is to accept the compromised position of the implants and improve on the aesthetics and function by minor gingival plastic surgical procedures.