The aim of this study is to determine the relative abundances of the different bacterial phyla and families in the microbiota present on the surface of PEEK implant-supported provisional abutments compared to titanium implant-supported provisional abutments, as well as the effect of both materials on the presence of antibiotics resistance genes.

The use of provisional abutments is mandatory during the restorative phase of any implant based oral rehabilitation. The introduction of poly-ether-ether-ketone (PEEK) for the manufacturing of provisional abutments as an alternative to conventional titanium abutments has opened the restorative spectra, offering the clinician and the patient better aesthetics and adhesive outcomes than its predecessor. However, there is to date no clarity on the impact of PEEK on the bacterial growth and the specificity of the microbiota on the abutment surface. Therefore, the present study aims to determine the relative abundances of the different bacterial phyla and families in the microbiota present on the surface of PEEK and titanium implant-supported provisional abutments, as well as the effect of both materials on the presence of antibiotics resistance genes.

Study Hypotheses:

• H1: The characteristics of the bacterial microbiota present at the connection area of implant-supported provisional abutments are dependent upon the abutment material.
• H2: An increased presence of antibiotic resistance genes is found in the bacterial microbiota on titanium provisional abutments when compared to that found on PEEK abutments.

The study uses a metagenomic approach based on the characterization of the bacterial communities, as well as on the sequencing of the 16S gene, and on the other hand, on the sequencing of the high-throughput (HTS) of the whole genome, for variations of the antibiotic resistance genes.

Sample retrieval will be conducted prior to implant placement, at the adjacent teeth gingival sulcus (t0), and two months after provisional abutment (and crown) connection (t1), from the retrieved abutments. Patient allocation in the "PEEK" or "Titanium" groups will be randomized. Intra- and interpatient comparisons will be conducted. Statistical analyses include two-way ANOVA and Tukey's post-hoc test, at p<0.05.

Inclusion Criteria:

• ASA I patients
• Indication of implant treatment to replace an upper or lower premolar
• Presence of natural teeth adjacent to the implant region
• Gingival biotype in the posterior region of 3 to 4 mm

Exclusion Criteria:

• Immunosuppressed patients
• Tabacco, alcohol or drug addictions
• History of periodontal disease
• Need of bone grafting in the implant region

No individual participant data will be communicated, in accordance with the ethical approval of the study. Data will be communicated grouped with the individual effects on the results assessed with the respective statistical tools.

Participants will be not aware of the type of provisional abutment used in their treatment. Retrieved samples will be codified in order to mask them for the metagenomic analysis.