Peri-Implantitis: Causes, Classification, Treatment and Prevention

Dental implantation is one of the most advanced methods for restoring missing teeth and has become increasingly prevalent in modern dentistry. Implant loss can occur within the first year following placement, known as "early implant loss," or after a year, referred to as "delayed implant loss." The latter is primarily associated with a severe inflammatory reaction in the tissues surrounding the osseointegrated implant.

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Peri-implantitis is an inflammatory condition affecting the bone tissue surrounding a dental implant. It is characterized by progressive bone resorption and its replacement with granulation tissue, ultimately leading to implant mobility and, if left untreated, implant failure.

Classification of Peri-Implantitis:

Peri-implantitis is classified into different grades (severity levels) based on clinical and radiographic findings, primarily considering bone loss and inflammatory symptoms.

Grading of Peri-Implantitis

1. Early (Mild) Peri-Implantitis

• Clinical Signs:
  • Mild inflammation (redness, swelling) around the implant.
  • Slight bleeding on probing (BOP) and possible suppuration.
• Pocket Depth: Slight increase but generally ≤5 mm.
• Bone Loss: Up to 2 mm (or up to 25% of the implant length).

2. Moderate Peri-Implantitis

• Clinical Signs:
  • Increased inflammation with more pronounced redness and swelling.
  • Bleeding on probing (BOP) and/or suppuration.
  • Possible early signs of implant mobility.
• Pocket Depth: 5–7 mm.
• Bone Loss: 2–4 mm (or 25–50% of the implant length).

3. Advanced (Severe) Peri-Implantitis

• Clinical Signs:
  • Severe inflammation with pus exudation.
  • Significant implant mobility (may indicate implant failure).
  • Pain or discomfort upon function.
• Pocket Depth: ≥7 mm.
• Bone Loss: >4 mm (or >50% of the implant length).

Alternative Classification by Schwarz et al. (2018)

A more simplified system also classifies peri-implantitis into mild, moderate, and severe categories based on the same criteria:

• Mild: Bone loss <25% of the implant length.
• Moderate: Bone loss 25–50%.
• Severe: Bone loss >50%, with possible implant mobility.

Risk Factors for Peri-Implantitis:

• Smoking, significantly increasing risk levels.
• Genetic predisposition, particularly with IL-1 polymorphism.
• A history of periodontitis.
• Poor oral hygiene.
• Systemic conditions such as diabetes, cardiovascular diseases, and immunosuppression.
• Iatrogenic factors.
• Soft tissue deficiencies around the implant site, such as a lack of keratinized gingiva.
• A history of previous implant failure.

Several factors can contribute to the development of peri-implantitis, including:

• Hematoma formation over the cover screw of the implant’s endosteal component, followed by infection.
• Violation of atraumatic surgical principles when preparing the implant site.
• Improper closure of the surgical wound.
• Scar tissue and a shallow vestibule in the oral cavity, which can cause mechanical trauma and ischemia at the wound margins.
• Poor oral hygiene and inadequate care of the gingival margin surrounding a one-stage implant.
• Implant mobility due to insufficient bone support.

Iatrogenic causes can significantly increase the risk of peri-implantitis. These include:

• Poor aseptic and antiseptic practices.
• Inadequate risk assessment.
• Improper implant selection, positioning, or placement of abutments and healing caps.
• Faulty prosthetic designs (crowns and dentures) leading to excessive load and chronic trauma to the periodontium.
• Excessive torque during implant placement.

Clinical Presentation of Peri-Implantitis

Peri-implantitis following one-stage implantation manifests as:

• Pain upon applying pressure to the implant.
• Redness and swelling of the mucosa surrounding the implant’s coronal part.
• Slight or absence of mobility of the implant.

Radiographic examination typically reveals bone resorption at the implant-bone interface or the formation of a bone pocket around the implant’s neck and body.

Peri-Implantitis in Two-Stage Implants

Peri-implantitis following the placement of a two-stage implant presents with distinctive clinical features. Around two to three weeks postoperatively, localized swelling, redness, sinus tract formation, or granulation tissue may appear over the mucosa covering the endosteal implant component, resembling a localized osteomyelitis-like reaction. Radiographic findings include bone resorption along the implant-bone interface or the formation of a bone defect.

Treatment of Peri-Implantitis

The management of peri-implantitis in one-stage implants includes the following steps:

• Plaque Removal: Cleaning the exposed portion of the implant using a scaler or plastic-tipped curettes to avoid contamination. (Contamination can hinder proper biomolecule adsorption, cell adhesion, and implant integration with surrounding tissues.)
• Detoxification: Treating the implant surface with citric acid for one minute.
• Antibacterial Therapy: Applying antibacterial gels to the gingival tissue.
• Medication: Prescribing antibiotics and metronidazole.
• Oral Hygiene Care: Implementing antiseptic rinses and using chlorhexidine-containing toothpaste.

After inflammation control, it is essential to eliminate any anatomical predisposing factors, such as performing vestibuloplasty or excising scar tissue in the oral vestibule.

If conservative treatment fails, implant removal and debridement of the bone site (gentle curettage of granulation tissue) are indicated. Reimplantation may be considered, typically six months later for a plate-form implant.

Treatment of Peri-implantitis in Two-Stage Implants

For Grades I and II peri-implantitis:

• Excision of the affected mucosa.
• Removal of the cover screw from the implant.
• Thorough irrigation of the wound and implant’s internal threading.
• Placement of a gingival former (essentially transitioning to the second surgical stage) and administration of anti-inflammatory therapy.

This approach is highly effective, and inflammation typically subsides within 3–4 days.

• In Grade I cases, one week after inflammation resolution, the gingival former is removed, the internal threading is thoroughly cleaned, and the cover screw is reinserted without suturing the wound. The wound closes naturally within 3–4 days due to scar tissue contraction.
• In Grade II cases, 10–14 days after inflammation resolution, surgical intervention may be required, involving:
  • Bone pocket revision.
  • Detoxification of the implant surface.
  • Filling of the pocket with an osteoconductive (preferably combined with osteoinductive) material.
  • Isolation of the implant and grafted material with a barrier membrane.
  • Closure of the surgical wound.

For Grade III peri-implantitis, a similar comprehensive treatment approach is used, followed by bone defect reconstruction using guided tissue regeneration techniques (Fig. 13-6).

For Grade IV peri-implantitis, while the same approach may be attempted, the success rate is minimal. Implant removal, bone bed revision, and reimplantation after 4–6 months remain the most effective strategies for ensuring long-term implant success.

The quality of prosthetic work significantly impacts implant longevity. The proper design and placement of crowns are essential to ensure good hygiene and long-term stability. The success of a bridge-supported prosthesis depends on the health of the surrounding gingiva, adjacent teeth, and implants. Studies highlight that diligent oral hygiene is a crucial factor in extending the lifespan of dental prostheses.

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Systemic Conditions and Implant Complications

Diabetes is frequently listed as a major risk factor and relative contraindication for surgical and periodontal procedures. However, some studies do not establish a definitive link between diabetes and peri-implantitis. While elevated blood glucose levels may impair tissue healing, no direct causal relationship has been proven. Some researchers suggest that peri-implant mucositis and peri-implantitis may also be associated with minimal thyroid dysfunction, characterized by reduced levels of active thyroid hormones. Women predisposed to hypothyroidism may be at increased risk for peri-implantitis.

Microbiological Aspects of Peri-Implant Infections

Bacteriological studies indicate significant differences in the microbial composition of peri-implantitis. 

In peri-implantitis, a mixed infection is observed, with anaerobes present in most of the cases. The most frequently identified periodontal pathogens include:

• Bacteroides forsythus 
• Porphyromonas gingivalis 
• Fusobacterium nucleatum
• Aggregatibacter actinomycetemcomitans 
• Prevotella intermedia

Additionally, Candida spp., Enterobacter spp., Streptococcus intermedius, Peptostreptococcus micros, and Staphylococcus aureus were frequently identified, indicating that the combined action of these pathogens plays a crucial role in the inflammatory-destructive process in peri-implant tissues.

Bacterial adhesion and plaque formation on the implant superstructure significantly impact inflammation. Studies have shown that rough implant surfaces harbor twice as many bacterial colonies as smooth ones. Highly polished surfaces reduce bacterial colonization and improve implant longevity.

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The longevity and success of dental implants are influenced by numerous factors, including proper prosthetic design, meticulous oral hygiene, and the management of systemic conditions. Understanding the risk factors and microbial environment surrounding implants is crucial for preventing complications and ensuring optimal patient outcomes.