This prospective parallel, double-blind, four-arm randomised controlled clinical study is planned to assess the difference in the level of the inflammatory biomarkers expressed following the placement of the first dental implant in patients with history of periodontitis (successfully treated) and healthy controls without the disease, during implant osseointegration period. The subjects in both groups will also be randomised to receive one of the two types of implants provided which have different surface treatment.

This is a prospective, parallel, double-blind, four-arm randomised clinical control study, aims to investigate the changes of clinical parameters and pro-inflammatory biomarkers expression and the shift following the first dental implant placement in patients who have been successfully treated for periodontitis, compared with healthy control without the disease.

The main questions to answer are:

1. Why do patients with history of periodontitis are at a greater risk to develop peri-implantitis than patients without history of periodontitis?
2. Is there any difference in the microbial composition, histological and immunological reaction of the host's dental plaque, peri-implant soft tissue, gingival crevicular fluids (GCF) of adjacent teeth and peri-implant sulcular fluids (PISF) following implant placement in patients with and without a history of periodontitis? The test group will consist of subjects with stabilised periodontitis, whilst the control group will consist of healthy patients with no history of periodontitis, as identified via history taking and clinical screening. Periodontal condition will be determined based on the new 2017 periodontal classification. All participants in both groups will be randomised to receive one of two types of implants with different surface treatment.

Clinical measurement, GCF and PISF will be collected around the single implant and adjacent teeth, at the following stages (time-point):

• Baseline (pre-operative)
• After implant placement (prior to the second stage surgery)
• After implant exposure (prior to the crown restoration)
• 3-month after the implant is restored
• Soft tissue will be obtained during the first stage (baseline) and second stage implant surgery (post-operative) and analysed.

Inclusion Criteria:

1. Specific inclusion criteria for test group:

   • History of periodontitis but currently stable
   • Must have successfully completed active periodontal treatment at least 4 months prior to the commencement of study

2. Specific inclusion criteria for control group:

   • No history of periodontitis, with minimal age-related radiographic bone loss
   • Reason for losing the tooth/teeth was not due to periodontal problem

3. General inclusion criteria:

   • Medically healthy
   • Aged between 30 to 65 years old
   • Non-smoker, or quit smoking at least 12 months before study commencement
   • Good oral hygiene (full mouth plaque score (FMPS)<20%, full mouth bleeding score (FMBS)<15%)
   • Indicated for a single implant placement in the posterior region, with adjacent and contralateral natural tooth
   • Intact inter-cuspal position

Exclusion Criteria:

• Previous history of dental implant placement
• Currently pregnant or intend to be pregnant, and/or lactating mothers
• Taking long-term medicines which may affect gingival tissue and oral microbiome, e.g. antibiotics, anticoagulants, anticonvulsants, immunosuppressants and calcium channel blockers.

Female and male

Individual participant data that underlie the results reported in this article after deidentification. Researchers should provide a methodologically sound proposal and directed to the principal investigator by email.

Beginning 3 months and ending 5 years following article(s) publication.

To gain access, data requestors will need to provide a methodologically sound proposal and sign a data access agreement.

All participants will be blinded from the randomisation. An opaque envelope will be used to conceal the implant designation and will only be revealed to the operator after the site is ready for implant placement. A blinded researcher will be assigned as clinical assessor who will not be involved with the surgical procedure, subject recruitment nor consent taking. An assistant who is not involved with the research will also be asked to re-code the sample tubes to ensure blinding for data/sample analysis.