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Classification According to Failure Mode

Depending on the mode and type of implant failure the following classification has been required.

1) Lack of Osseointegration (Indicated as Mobility): Loss of osseointegration can occur during the early stages of treatment because of the inability of the woven bone to interface to mineralize, which can result from surgical trauma, premature loading, infection and surface contamination. The loss of osseointegration occurring later during the course of the treatment may be the result of either overloading or infection.The clinical features include mobility, easy to remove with counter torque movement, thin radiolucent zone and thin layer of soft tissue around the fixture.(Seen on removal).

2) Unacceptable Aesthetics: The implant which has successfully integrated with bone may still be a failure if the Prosthesis which it is designed to support does not meet with the aesthetic requirements of the patient. The aesthetic outcome is dependent on four main factors:

a) Implant Placement — The failure to place an implant in the correct location in the buccolingual plane, mesiodistal plane and the inciso cervical plane results in the esthetic failure. Improper spacing between implants and teeth and in between two implants can lead loss of vitality of the intervening bone, bone loss and subsequent tissue leading to loss of interdental papilla and creation of
dark triangles in the gingival embrasure and is esthetic liability. The placement of the implant be based on the decision to have a a cementable or srew type of prosthetics.

b) Soft tissue Management— The periimplant soft tissue is very critical in the aesthetic zone. The handling of the tissue during surgery to minimize trauma,the preservation of keratinized soft tissue (avoiding tissue punch in stage 2 surgery), the contours of the prostheses and the implant placement as discussed above are critical for aesthetic success.

c) Bone grafting issues— Planning of the case is very critical. Any bone defect in the aesthetic zone should be evaluated prior to implant placement in order to obtain a prosthetic based implant placement.

d) Prosthetic Considerations— The complete aesthetic diagnosis of the patient should be done prior to implant placement in the aesthetic zone. The smile line of the patient is critical. Different type of prosthesis should be designed depending upon the smile design. A diagnostic wax mock up is essential to visualize the end result and patient's consent must be obtained prior to treatment commencement.

3) Functional Problems: The masticatory efficiency of the implant supported prosthesis depends on the anchorage related factors and the prosthesis related factors. The presence of mobility and failure of the implants supporting the prosthesis are the anchorage related factors that lead to a functional failure. An Implant supported prosthesis if designed at an improper vertical dimension can
result in functional loss, so the occlusal scheme and the occlusion achieved by the prosthesis is critical in obtaining proper function.

4) Psychological Problems: Failure to fulfill the patient's expectations and failure to gain the patient's acceptance and satisfaction constitutes a psychological failure. It is highly imperative that the patient be adequately informed and informed of the likely outcome of the treatment. Diagnostic wax ups and computer generated images are excellent means to achieve patient education and of course as always it is prudent to under promise and over-deliver.

Classification According to Condition of Failure

Clinically unhealthy implants are classified as “ailing” or “failing”. It is necessary to distinguish between an ailing versus a failing implant to determine the treatment steps necessary to salvage the unhealthy implant. Implants exhibiting soft tissue problems exclusively are classified as ailing and have a more favourable prognosis—Peri-implant mucositis involves inflammatory changes confined to the soft tissue surrounding an implant. In some instances, the ailing implant may have exhibited early bone loss along with soft tissue pocketing. However, this bone loss tends to become static at the 3 to 4 month maintenance checks. A lamina dura indicating a state of chronicity also may be present at the borders of the osseous defect.

In contrast, the failing implant may show evidence of pocketing, bleeding upon probing, purulence, and indicates the bone loss patterns are progressing despite previous therapy. Therefore, an implant that is progressively losing its bone anchorage, but is still clinically stable, can be defined as failing.Failing implants have a poorer prognosis but however, if properly recognized and treated, a failing implant may be saved. Microflora associated with failing dental implants are identical to those found in chronic adult periodontitis. This microflora triggers inflammation and bone loss and is termed peri-implantitis. Peri-implantitis occurs when there is progressive peri-implant bone loss in conjunction with a soft tissue inflammatory lesion.

Historically, other signs and symptom markers have been used to classify the ailing and failing implant. Tissue tone, pocket depth, attachment levels, bleeding on probing,suppuration, cervical fluid flow, plaque index, gingival index, mobility, oxygen tension levels, tissue collagenase activity, radiographic evaluation, and microbiological characterization of subgingival flora have all been utilized in implant classification.

Clinical warning signs of implant failure
The clinical signs of implant failure are:

1) Connecting Screw loosening.

2) Connecting Screw failure.

3) Gingival bleeding and enlargement.

4) Purulent exudates from large pockets.

5) Pain.

6) Fracture of prosthetic component.

7) Angular bone loss noted radiographically.

8) Long standing infection and soft tissue sloughing seen during healing after stage one surgery.

Mobility of the implant with or without purulent exudates is the final clinical evidence of a failed implant.There is a classification by Carl Misch which delineates the failures as per the stage as seen and it helps to streamline the cause.

The figures show natural tooth on the left(L) side and implant(R) in the right half (i) - Normal Tooth(L) & Implant(R), (ii)- Ginvitis(L) &Perimucositis (R), (iii)- Periodontitis (L) & Perimplantitis (R)
The figures show natural tooth on the left(L) side and implant(R) in the right half
(i) - Normal Tooth(L) & Implant(R), (ii)- Ginvitis(L) &Perimucositis (R), (iii)- Periodontitis (L) & Perimplantitis (R)