900 subjects having received dental implants 9-10 years ago are invited for a clinical and radiographic examination. The individuals were randomly selected from the National Health Insurance data register in Sweden.

The clinical and radiographic examination of the 900 selected subjects will include assessments of implant loss, loss of prosthesis and technical / biological complications.

Biological complications will be assessed from the findings in the clinical and radiographic examinations. Thus, signs of pathology in peri-implant tissues, probing pocket depth (PPD) and bleeding/pus on probing (BoP) will be recorded. Marginal bone loss and other findings in radiographs will also be evaluated.

The prevalence, extent and severity of peri-implantitis will hereby be determined. Patient-centered outcomes will also be obtained.

A questionnaire was distributed to the 4716 identified subjects. 3827 questionnaires (81.15%) were returned and, hence, included in the analysis.

From the sample of 3827 patients who responded to the questionnaire, 3107 (81.19%) gave their consent for access of patient files/records.

Patient files/records of 2780 individuals could be collected from the treating dentists (89.48%). Out of the 2780, 900 individuals were selected by random sampling, stratifying only for the two age groups.

Inclusion Criteria:

• Having received implants within the Swedish insurance system in 2003/2004.
• Being in one of the two age groups in 2003: 65-75 years and 45 - 55 years.
• Having answered the initial questionnaire
• Treating dentist provided patient files/records

Exclusion Criteria:

- Having died during the study period (collection of questionnaire and patient files/records)

The register of the Swedish Social Insurance Agency was searched for subjects scheduled for treatment with dental implants in 2003/2004. In a first group, subjects between 65 and 75 years old in 2003 were identified and from this pool of about 23.000 individuals, 3.000 subjects were randomly selected. In a second group, all subjects in the age of 45-60 years were identified (n=1716)from the same register. Thus, the total study population in the present project included 4716 subjects.