Peri-implantitis: What Is It, How Is It Recognised and When Can It Still Be Treated?

Peri-implantitis is a bacterial infection affecting the bone and gum tissue around a dental implant. If it is not treated in time it progresses and often makes removal of the implant necessary. What is it, how is it recognised, and when can it still be treated?

Peri-implantitis is an infection of the tissues surrounding a dental implant. When it is not diagnosed and treated in time, it leads to the progressive loss of supporting bone and, in most cases, to the need to remove the implant.

Understanding peri-implantitis means understanding why an implant that appeared perfectly integrated can start to cause problems even years after it was placed.

What is peri-implantitis?

Peri-implantitis is the peri-implant equivalent of periodontitis: a bacterial infection that involves both the soft tissue (gum) and the bone that anchors the implant to the mandible or maxilla. It must be distinguished from peri-implant mucositis, an inflammation confined to the soft tissue that is reversible with early therapy.

Peri-implantitis, by contrast, involves bone loss that is visible on radiographs. This is the essential clinical distinction: it is not a passing inflammation, but a destructive process that, without early intervention, tends to progress.

How common is it?

The European consensus on the prevention of peri-implant diseases estimates a mean prevalence of peri-implantitis of around 22% of patients with implants, and of mucositis of around 43%. These are averages drawn from studies with different diagnostic criteria and observation periods, to be read as orders of magnitude.

It is an underestimated complication, partly because symptoms in the early stages are mild, and partly because many patients stop attending periodic check-ups once their rehabilitation has been completed.

Causes and risk factors

The primary cause is bacterial: anaerobic biofilms that colonise implant surfaces, similar but not identical to those responsible for periodontitis. Not every patient with biofilm develops peri-implantitis: the body’s response and local factors make the difference.

The main risk factors are:

• a history of previous periodontitis, even if successfully treated
• insufficient oral hygiene, or hygiene made impossible by poorly designed prostheses
• smoking
• uncontrolled diabetes
• a poorly fitting prosthesis, or residual cement left in the peri-implant tissues
• inadequate follow-up after implant placement
• excessive occlusal load on the implant

The prosthesis is often the overlooked factor: a prosthetic margin that cannot be reached for cleaning, an unfavourable emergence profile, cement residues not removed at the time of cementation. These elements do not depend on the patient’s hygiene, but on clinical and technical problems introduced during the stages of the rehabilitation.

How is it recognised? The symptoms

Peri-implantitis has a clinically relevant characteristic: it is often asymptomatic in its early stages. The patient feels no pain because the implant, unlike a natural tooth, has no periodontal ligament and none of the sensory receptors the ligament contains.

Signs not to ignore:

• red or swollen gum around the implant
• bleeding on periodontal probing
• exudate discharging from the gum around the implant
• implant mobility: a late sign indicating advanced bone loss; in these cases the implant cannot be saved
• gum recession with exposure of the implant surface
• a feeling of pressure or discomfort when chewing

Mobility is a late sign and, when present, indicates that the situation is already severely compromised. Waiting until an implant becomes mobile before intervening means losing any chance of saving it.

Diagnosis

Diagnosing peri-implantitis requires:

• peri-implant probing with a calibrated probe, to measure the depth of the pockets around the implant
• an intraoral radiograph or cone beam CT (CBCT) to assess the pattern and extent of bone loss
• assessment of bleeding on probing and of the presence of suppuration

Comparison with previous radiographs is essential: bone loss is significant only if it progresses over time. This is why documented follow-up has diagnostic value, not only clinical value. An implant that has never been radiographed after placement deprives the clinician of an indispensable reference point.

When can it still be treated?

Peri-implantitis can be treated when bone loss is limited and the implant is still osseointegrated, that is, without clinically detectable mobility. The aim of treatment is to eliminate the bacterial infection and, where the anatomy allows, to recover part of the lost bone.

The protocol is structured on three levels, according to the severity of the clinical picture.

Non-surgical treatment

This is the first phase in the treatment of any clinical presentation of peri-implantitis. In the early and moderate stages it can be resolutive. It involves mechanical decontamination of the implant surface with dedicated instruments (titanium curettes, ultrasonic tips), often combined with diode or erbium-YAG lasers, which provide effective antibacterial action on implant surfaces without altering their topography. It may be supplemented by local or systemic antibiotic therapy.

Regenerative surgical treatment

Indicated when bone loss has created defects whose morphology is favourable to regeneration (intrabony defects, crater-like defects). The area is exposed surgically, the implant surface is decontaminated and bone graft material is placed with collagen membranes. The aim is to partially regenerate the bone support lost around the implant.

Resective surgery

When the morphology of the bone defect is not favourable to regeneration, a resective approach is chosen: it reshapes the remaining bone to eliminate the pockets and make the implant surfaces accessible to the patient’s own hygiene.

When can the implant not be saved?

Not every implant affected by peri-implantitis can be saved. The criteria that point towards removal are:

• clinically detectable mobility
• bone loss greater than 50% of the implant length
• bone defects with unfavourable morphology and no regenerative prognosis
• involvement of critical anatomical structures (maxillary sinus, inferior alveolar nerve canal)

Removal is not necessarily the end of the treatment pathway. In many cases, after removal and an adequate healing period, a new implant can be placed with a favourable prognosis, provided that the causes of the failure have been identified and corrected before proceeding.

The limit of approaches without a causal diagnosis

The most common problem in managing peri-implantitis is treating the inflammation without having identified its cause. Therapy can temporarily eliminate the infection, but if the factor that generated it remains (an inadequate prosthesis, excessive occlusal load, an implant surface that cannot be reached for hygiene), the risk of relapse remains high.

The clinically relevant question is not “how do we treat this peri-implantitis”, but “why did it develop, in this patient, at this site, with this prosthesis”. The answer to that question determines both the prognosis and the choice of treatment.

What to do if you suspect peri-implantitis

The first step is not to delay. Peri-implantitis responds better to therapy in its early stages: every month that passes without a diagnosis can mean further bone loss, which becomes increasingly difficult to recover.

If you notice bleeding from the gum around an implant, swelling, suppuration or any kind of discomfort, a specialist examination with probing and a radiograph is indicated. If you are already being treated but the symptoms are not subsiding, a second opinion makes it possible to assess whether the current treatment plan is appropriate or whether there are clinically sound alternatives.