Peri-implantitis is a destructive inflammatory process affecting the soft and hard tissues surrounding dental implants. The soft tissues become inflamed whereas the alveolar bone (hard tissue), which surrounds the implant for the purposes of retention, is lost over time. The bone loss involved in peri-implantitis differentiates this condition from peri-mucositis, a reversible inflammatory reaction involving only the soft tissues around the implant.
Signs and symptoms Peri-implantitis does not present in the same way for all patients. Patients are recommended to regularly attend dental appointments and to seek advice from their dentist if they have any concerns for their oral health. Before the signs and symptoms are explained, it is worth noting that healthy peri-implant tissue should not be swollen, bleeding, producing pus, or have a reddened appearance. From a patient's perspective, he/she may notice loosening or wobbling of the implant. This symptom does not usually present at the early stages of peri-implantitis as the implant will still be fused to bone at its deeper aspects. It is more likely that the patient will notice bleeding whilst brushing their teeth. A patient may also notice swelling around the implant, bad breath and/or foul taste. Clinically, peri-implantitis involves both inflammation of soft tissues and destruction of bone, therefore, there is usually evidence of both bone loss (assessed by a radiograph) and bleeding when nearby tissues are probed, a common finding for soft tissue inflammation. There have been reports of bone loss without any accompanying sign of soft tissue inflammation. Without evidence of bone loss, the diagnosis is restricted to peri-mucositis (see comparison between peri-implantitis and peri-implant mucositis below for more information). Other reported features include pain and gingival hyperplasia. Pain is thought to be a rare symptom and is usually linked to an acute infection.
Bone loss In healthy situation, there should be no sign of bone loss other than potential bone remodelling at the alveolar crest following implant placement. The shape of the alveolar bone in regions of bone loss varies depending on the buccal-lingual length (or cheek-to-tongue length) of the bone. Where this length is greater than the extent of the peri-implantitis, the region of bone loss can take the shape of a crater, with walls of bone surrounding the pathology; this is the most common presentation of bone loss. Where the buccal-lingual length is smaller, there may be no walls of bone surrounding the pathology.
Probing Bleeding on probing is considered normal whilst tissues are healing shortly after implant placement, however, if bleeding is present months or years after placement, inflammation should be suspected. Other features which may be present whilst probing include pus, the presence of a pocket around the implant and/or recession of the gums. The dental professional may also notice swelling and redness of the gums, the latter of which is termed erythema. During probing, the pocket depth around an implant is typically greater than around natural teeth. Also, the value for the pocket depth around an implant is variable in health, therefore, diagnosis of a pocket is reliant on a change in pocket depth when comparing measurements from different appointments. For this reason, a Basic Periodontal Examination (BPE) is not appropriate, and a 4 or 6 point pocket chart is instead recommended. Below is a summary table of signs and symptoms associated with peri-implantitis.
Causes & pathology Studies in both human and animal specimens found that the presence of plaque and its conglomeration around tissues invariably concluded in inflammation around the peri-implant soft tissue. To find the pathology of peri-implantitis, experiments were compared to peri-mucositis, and found that in peri-implantitis, there were more neutrophil granulocytes and a bigger proportion of (CD19+) B-cells. Similarly in periodontitis, peri-implantitis lesions contained many plasma cells and lymphocytes, however there were a larger ratio of macrophage cells and leukocytic cells.
Risk factors The risk factors have been sub-divided to distinguish those with strong supporting evidence (below the sub-heading 'risk factor') from those with conflicting evidence (below the sub-heading 'potential risk factors').
Risk factors Poor plaque control - this highlights the importance of cleaning the tissues around an implant between dental appointments. It is understood that patients sometimes feel discomfort whilst brushing around implants and are advised to speak to their dentist about this. Also, patients may sometimes be unable to access some sites for cleaning. Lack of regular maintenance therapy. To avoid this, regular dental visits should be arranged to enable early detection and management of peri-implantitis.
Titanium implant degradation products in the form of microparticles, which have infiltrated the peri-implant tissue and peri-implant bacterial plaque. These particles have occasionally been found in small concentrations in healthy peri-implant tissue; however, their concentration was reported to be significantly higher in individuals with peri-implantitis. These titanium particles are internalized by phagocytes and have been found to elicit strong pro-inflammatory effects and bone resorption in preclinical models suggesting causative implications to peri-implantitis.
Potential risk factors Diabetes mellitus (commonly known as type 1 and type 2 diabetes) Excess cement. The cement is used to retain the implant, although its potentially rough surface may aid with plaque retention. Therefore, any residual cement surrounding the implant abutment interface can give rise to peri-implantitis. The alternative to cement is a screw-retained implant, although some studies have reported a higher risk of peri-implantitis with these compared to cement-retained implants. Further research is required to establish whether the following are indeed risk factors for peri-implantitis:
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