of Failure and Implant-Related Complications in Graftless Implant Reconstructions (for Atrophic Jaws)


Fig. 15.1

Standard panoramic radiograph (a) shows little evidence of a problem with anterior maxillary implants (arrowed). However reformatted axial (b) and cross-sectional (c) views from CBCT examination show that 7 years later the immediately placed implants are entirely outside of the bony envelope of the maxilla

Given the anatomical constraints and surgical challenges, attention to detail in prosthetic planning and in provisional and definitive phases of prosthetic reconstruction is also of paramount importance. Poor prosthetic planning may not only lead to aesthetic and prosthetic complications (see previous chapters in this series), but might also lead to inadequate surgical planning, inadequate surgical preparation of the jaw, inappropriate implant positioning, inappropriate loading and ultimately implant failure.

In this chapter, we describe some of the compromises and complications which may lead to failure in graftless treatments, and describe strategies that the authors have used to manage complications and salvage situations where there has been failure.

15.1.1 Implant Failure

Like any other implant treatment, there is always a risk of implant failure. Clearly most patients who need graftless treatments have not been very successful at maintaining their teeth, and many of these individuals may not be adept at looking after their implants either. All the recognised risks of implant failure will apply; smokers [3], those who suffer from periodontal disease [4], diabetics [5], patients prescribed bisphosphonates [6] and individuals in poor health [7] will all be at risk of implant failure. Additional risks relate to nearby critical anatomy, biomechanical challenges, and, also, most importantly management of patient expectations.

Even in highly atrophic jaws, graftless treatments may use a combination of short and angled implants to immediately support fixed provisional prostheses. In the All-on-4® protocol the distal implants are angled to broaden their span, improving support. Lack of respect for the biomechanics of this form of reconstruction can lead to failure (Fig. 15.2).

Fig. 15.2

These patients believed that they were to have ‘All-on-4’ treatment. In this case (a), the maxillary implants are all positioned anteriorly for this inadequate reconstruction which failed with fracture of three abutment screws and failure of the remaining functional implant. The panoramic radiograph suggests that no attempt has been made to fully utilise the available jaw to broaden the span of implant support (b). Note the presence of an intact opposing dentition. In this case (c) the implants are also poorly positioned anteriorly—note the fractured abutment screw in the right rear implant. The patient was provided with a much repaired and poorly constructed and totally inadequate provisional prosthesis (d), which was still in use 2 years after surgery

Numerous studies have shown excellent outcomes for such treatments [8], though for an individual who experiences a failure a proven high success rate in the literature will be of little solace. In the event of early implant failure soon after surgery, loss of support as the implant loosens may lead to an escalation in the complexity of the problem, with the potential for overload or fracture of the provisional prosthesis, failure of prosthetic components and failure of other implants involved in the reconstruction. The use of a provisional prosthesis is important as it will serve to splint and stabilise the implant during the healing period. It is also key, in that if an implant fails early on, it does so before an investment in the definitive fixed prosthesis has been made.

A poorly made or insubstantial provisional bridge may fracture and cause overload of an implant. Where atrophy is minimal and the jaw must be reduced in order to find space for the prosthesis, inadequate reduction may result in the production of a weak provisional prosthesis; early fracture of this prosthesis may lead to implant failure. On the other hand, excessive jaw reduction may remove bone that might prove valuable later in the event of a failure—patients must be specifically consented for jaw reduction.

Where there is an early failure, patient management will be more straightforward if another suitable implant site is immediately available to augment support for the bridgework, or if there is at least a removable prosthesis to hand. Easy access to laboratory services and possession of technical skills will make all the difference to prompt management. If anchorage for the remaining implants is less than ideal, or if two or more implants fail, or healing of newly placed implants is not advanced at the time of failure, there may well be a need for the patient to wear a removable prosthesis as an interim measure. Patients may become upset if then asked to wear a removable prosthesis, particularly where multiple teeth have been removed at the time of surgery and when the patient has no experience of using a removable prosthesis. It is therefore sensible to discuss failure, and to make contemporaneous notes of this discussion long before treatment, in addition to providing clear written information preoperatively.

In the case of later implant failure, there is the advantage that remaining implants may be stable, and dental extraction sites will be in a more advanced healed state.

Patients may be unaware of implant problems until they are severe. Late loss of an implant as a result of, e.g., peri-implantitis may be accompanied by a great deal of bone loss, quite likely affecting more than a single implant, as in Fig. 15.3, with devastating consequences.

Fig. 15.3

This 60-year-old smoker was referred with multiple implants affected by peri-implantitis (a, b). Removing these long implants would be highly destructive, so a decision was made to attempt to maintain them for the time being with surgical debridement (c), addressing the smoking and maintenance issues for now

If a single implant is lost a definitive reconstruction might continue to function on three implants whilst the site heals, particularly if the implants are widely distributed (Fig. 15.4). Failure of a single terminal support may again be the catalyst to prosthetic failure or loss of further implants; in this event a fixed prosthesis may need to be shortened to avoid an extended cantilever. Where practical, provision of more than four implants may be beneficial for patients who are perceived to be at higher risk of implant failure. If a definitive prosthesis has already been provided for the patient the provisional prosthesis may be modified with a view to later adapting the definitive prosthesis.

Fig. 15.4

A 65-year-old patient developed rapidly progressive bone loss associated with just one of four mandibular implants (a—4 years post-surgery, b—just 3 years later). Poor cleaning (c), depression and loss of diabetic control may all have been factors. With removal of the implant, the return of diabetic control and a return to satisfactory maintenance behaviour the situation seemed reasonably stable a year later, with the patient functioning on three of the four original implants

15.1.2 Removing Failing Implants

Long implants are often used to provide robust immediate stability for a temporary prosthesis. Because of this, even when a failing implant has lost as much as 50% of its supporting bone, removing the partially osseointegrated implant can be challenging and has the potential to cause considerable further bony destruction. Strategies for less invasive implant removal include the use of close-fitting trephines (Fig. 15.5a), ultrasonic instrumentation (Fig. 15.5b) and bone removal with a fine fissure bur in a reverse air turbine handpiece (Fig. 15.5c); all techniques require patience, precision and copious irrigation. Bone removal should of course be kept to a minimum—implant retrieval tools (Fig. 15.5d) provide a useful adjunct to this armamentarium, enabling the less invasive removal of implants, though these must be used with caution as there is a tendency for thinner walled implants to split if they are still osseointegrated for more than 4–5 mm of their length. In practice all these approaches may be best combined for the most bone-conserving outcome, focusing upon a gentle technique with minimal heat production. As removal of a partially osseointegrated implant can be so destructive, when making the decision to remove an implant affected by peri-implantitis, careful consideration must be given to the patient’s age and the rate of disease progression before moving towards explantation.

Fig. 15.5

Various approaches to implant removal . (a) With a trephine. (b) With an ultrasonic device. (c) High-speed surgical turbine with rear-venting exhaust. (d) Reverse torque implant retrieval tool

15.1.3 ‘Rescue’ Implants

In the atrophic jaw, the position of the most posterior implant which may be angled distally to broaden support and spread load is usually constrained by the critical anatomical structures which demarcate the easily exploitable bone. If attempting to immediately replace a failed implant with a ‘rescue’ implant there may be the option to use a longer or wider implant, but using the same site may be a risky strategy unless the cause of the failure is well understood and there is a reasonable expectation that the outcome will be better; it is not uncommon to find that there is extensive bone loss in the failure site, particularly if the failure is not immediately identified, which may well be the case as the ailing implant will be splinted by the provisional bridgework (Fig. 15.6). CBCT imaging makes it possible to carefully scrutinise the jaw for alternative implant sites; if an implant is loose consider imaging after removal of the implant and with the prosthesis removed in order to reduce the amount of local radiographic artefact related to the implant and prosthesis. With more and more CBCT scanners available, this is a situation where the type of CBCT apparatus and the settings used should be carefully considered for an optimised high-resolution result.

Fig. 15.6

Panoramic radiograph (a), showing implant treatment in both jaws for a patient who had advanced periodontal disease. The asymptomatic implant in the upper right lateral incisor position was found to have failed 3 months after surgery when the patient presented with a fracture of her temporary prosthesis. Reformatted panoramic (b) and cross section (c) reconstructed from CBCT, 12 weeks after removal of failed implant. Note extensive bone loss only really visible in the cross section; replacement of the implant consequently delayed, with the reconstruction completed 6 months later (d)

Salvaging the situation will be easier when there is more bone available and the implants have been widely spread, leaving more space for a ‘rescue’ implant to be positioned in a new site. If it is an angled distal implant , the sinus in the upper jaw or mental nerve in the lower jaw may limit the span of the implants driving the positioning of the new implant more anteriorly (Fig. 15.7), such that the span may be narrower than that of the original situation.

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Dec 6, 2018 | Posted by in General Dentistry | Comments Off on of Failure and Implant-Related Complications in Graftless Implant Reconstructions (for Atrophic Jaws)
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