Effect of Metallic Particles on the Progression of Peri-Implantitis

Effect of Metallic Micro- and Nanoparticles on the Progression of Peri-Implantitis and Their Interaction With the Microbiota

This observational cross-sectional study aims to investigate the presence and characteristics of metallic micro- and nanoparticles in peri-implant tissues and their potential association with peri-implantitis progression, the local microbiota, and the host inflammatory response.

The study will include 50 participants divided into two groups: individuals requiring dental implant placement, from whom healthy gingival tissue will be collected as an active control, and patients diagnosed with peri-implantitis, from whom granulation tissue and submucosal biofilm samples will be obtained. Tissue samples will be analysed to determine the concentration, size, morphology, and intracellular localisation of metallic particles, as well as macrophage polarisation. Microbiological analyses will characterise the peri-implant microbiota. Associations between metallic particle burden, microbiological composition, inflammatory response, and clinical and radiographic indicators of peri-implant disease severity and progression will also be explored.

This observational cross-sectional study will include 50 participants, with one study site per participant, divided equally into two groups. The active control group will include patients requiring the placement of at least one dental implant. A healthy gingival tissue sample will be collected immediately before implant placement, provided that the width of keratinised mucosa at the sampling site is at least 3 mm. The peri-implantitis group will include patients diagnosed according to the 2017 World Workshop case definition. Granulation tissue and a submucosal biofilm sample will be collected from the selected affected implant. Participants will not be assigned to any exposure or therapeutic intervention for research purposes.

Tissue samples from both groups will be divided into subsamples and analysed using complementary laboratory techniques. Inductively coupled plasma triple quadrupole mass spectrometry will be used to quantify titanium, aluminium, vanadium, molybdenum, and chromium. Scanning and transmission electron microscopy will be used to characterise the size, morphology, distribution, and intracellular localisation of metallic particles. Histopathological and immunohistochemical analyses will evaluate tissue characteristics and macrophage polarisation.

In the peri-implantitis group, 16S ribosomal RNA gene sequencing of submucosal biofilm samples will be performed to characterise the microbial community. A biofilm sample will not be collected from the active control group because these participants do not yet have an established peri-implantitis environment at the sampling site.

Clinical, radiographic, implant-related, prosthetic, and participant-related variables will also be recorded. The study will compare the metallic particle burden and tissue characteristics between healthy gingival and peri-implantitis tissues. It will also explore associations between metallic particle burden, microbial composition, macrophage polarisation, and clinical and radiographic indicators of peri-implant disease severity and progression.

Inclusion Criteria: To be considered eligible for participation in this study, patients must fulfil all the following criteria:

1. Written informed consent duly completed and signed for participation in the study and the use of biological samples.

2. Male or female patients aged 18 years or older.

3. Patients treated at the Master's Degree in Oral Surgery and Implantology or the Master's Degree in Periodontology and Peri-Implantology at the University of Barcelona.

4. Patients in full possession of their mental faculties and capable of understanding and providing written informed consent prior to enrolment in the study.

5. Willingness to comply with all study procedures required by the protocol. In addition, participants must meet the criteria for one of the following study groups:

   • Peri-implantitis Group:

     1. Diagnosis of peri-implantitis according to the diagnostic criteria established at the 2017 World Workshop on the Classification of Periodontal and Peri- Implant Diseases and Conditions.
     2. Candidate for surgical or non-surgical peri-implantitis treatment involving the collection of peri-implant granulation tissue and/or biofilm samples.

   • Control Group:

     1. Candidate for implant therapy, with the placement of at least one dental implant included in the treatment plan.
     2. Candidate for implant placement using a static computer-guided surgical approach.
     3. Availability of soft tissue from the implant recipient site for sample collection (≥ 3 mm).

Exclusion Criteria: To be considered eligible for participation in this study, patients must not fulfil any of the following criteria:

1. Patients who, in the investigator's judgement, are not suitable candidates for participation in the study based on their medical history, physical examination findings, concomitant medications, or concurrent systemic conditions:

   1. Presence of uncontrolled periodontal disease, defined as probing depths

      ≥5 mm with concomitant bleeding on probing or probing depths ≥6 mm.

   2. Immunocompromised patients.

   3. History of radiotherapy or chemotherapy.

   4. Presence of uncontrolled systemic diseases.

   5. Presence of systemic conditions known to affect bone metabolism.

   6. Current treatment with medications known to alter bone metabolism.

   7. History of oral cancer.

   8. Use of systemic antibiotics within the previous 6 months.

2. Current smokers consuming ≥20 cigarettes per day.

3. History of drug or alcohol abuse. For the purposes of this study, alcohol abuse is defined as the habitual consumption of more than four units of alcohol per day (one unit being approximately equivalent to 125 mL of wine, 200 mL of beer, or 25 mL of spirits).

4. Participation in any other clinical study within the 4 weeks preceding enrolment.

5. Surgical or non-surgical peri-implantitis treatment at the selected implant site within the 12 months preceding enrolment.

6. Pregnant or breastfeeding women.