The goal of the clinical trial is to compare laser therapy with ultrasonic therapy in patients with inflammation in the tissue surrounding single implants (peri-implant mucositis). The outcomes are bleeding on probing (BOP), pocket depth, suppuration, recession of the peri-implant mucosal margin, the treatment time and changes in bone levels before and after treatment in the test, and control group respectively. The quality of life will be measured from a standardized protocol.

The hypothesis is that treatment with laser therapy in patients with peri-implant mucositis will show less inflammation with less bleeding and a better pocket closure compared to the treatment with the ultrasound.

Data from the clinical treatment will be registered in medical records. In parallel, clinical data will be documented in a study protocol and saved in a safe together with a code list in accordance with a standard operation procedure at the clinic.The protocol with the specific treatment procedure (test or control) will not be opened until the study is completed and only by authorized persons with access to the data in the study such as, the principal investigator and the statisticians.

Variables used in the study originates from an international world workshop on the classification of periodontal and peri-implant diseases and conditions in 2018. In accordance with the working group a diagnosis of peri-implant mucositis should include bleeding on probing and or pus and no bone loss (X-ray). In this study the primary outcomes are bleeding on probing (BOP) and or pus and pocket depth,

The aim is to assess the clinical outcome over 6 months following treatment with non-surgical debridement using an Er:Yag laser device (AdvErL EVO, Morita corporation, Japan) (Test group) or with the use of mechanical therapy using an ultrasonic device with a specially designed tip (EMS, Switzerland) (Control group). An active comparator (Control group) was compared to an experimental arm (Test group).

Patients will therefore be randomized into a test or control group. Inclusion criteria will follow a full mouth routine periodontal examination, including analysis of available radiographs.

All measurements will be performed by a dental hygienist who is blinded for the specific treatment test or control. A periodontist will perform all the treatments and is therefore not blinded. Upon the final appointment the specific arm of treatment will be registered by the periodontist in the patient journal.

All patients will be given oral and written information about the study and sign a written informed consent. The patients will be informed that they could drop off whenever they want without any explanations. The ethical board approved the study.

The test group will be treated using the Er:Yag laser device.The control group will be treated using an ultrasonic device with peek coated tips (EMS, Switzerland). Following treatment all patients, independent of group, will be instructed in proper home care using a toothbrush and interproximal aids as needed.

Study design:

• Baseline: Clinical registrations and treatment
• 1 month: Clinical registrations
• 3 months: Clinical registrations and treatment
• 6 months: Clinical registrations and treatment

In addition, the instrument Oral Health Impact Profile (OHIP) will be used as a measurement of quality of life.

Adverse events will be evaluated at each visit. If a patient should require any treatment during the study the necessary treatment will be provided and according to the standard of care. If adverse events related to the treatment they will be recorded. The investigation will be performed according to the principles of the Declaration of Helsinki on experimentation involving human subjects.

Participant not fulfilling the study will be reported in the patient journal as not completed and statistically noted as missing data.

From the statistical power analysis 38 individuals were minimum to reach a clinically significant difference. The power analysis was based on: if bleeding on probing (BOP) is reduced with 30% ± 10 in the test group and with a 30% decrease in the control group is to be detected at alpha =0.05 and a power of beta= 0.2. Hence it is foreseen to incorporate 45 subjects in the study if some of the individuals will not fulfil the study.

The IBM SPSS version 28.0 statistical software package (SPSS Inc., Armonk, NY, USA) for personal computer will be used in the statistical analyses.

Statistics will be calculated as means with standard deviation (SD). Independent t-tests (equal variance not assumed) paired t-test and one-way ANOVA test will be used to compare inter and intra-group differences. Non-parametric chi-square test will be used for categorical variables. Statistical significance will be set with 80 percent at p < 0.05. Non visits will be recorded as missing data in the statistics.

Inclusion Criteria:

• ≥ 1 peri-implant site with probing depth ≥ 4 mm combined with bleeding and or pus on probing
• bone loss ≤ 2 mm measured from the implant shoulder (as a consequence of remodelling during the healing process)

Exclusion Criteria:

• Subjects with uncontrolled diabetes HbA1c >6.5
• Subjects requiring prophylactic antibiotics
• Subjects taking prednisolone
• Subjects taking medications known to have effects on gingival overgrowth

The outcome assessor, in this case the dental hygienist performing the registrations/measurement, is blinded during the whole study

The principal investigator, in this case the periodontologist performing all the treatments, and is therefore not blinded.