The brush bristles of the test device (Labrida BioClean®, LABRIDA AS, Oslo, Norway) are made of the biopolymer chitosan. Any debris left from the chitosan bristles is completely biocompatible and will dissolve or be resorbed, thus not causing harm to the tissues.surrounding the tooth. Chitosan is made from chitin derived from shell of marine crustaceans such as shrimp and crab, however chemically modified and thus not even considered to be animally derived. Chitosan has been approved for use in e.g., surgical bandages, as a haemostatic agent and as dietary supplement used in a wide range of nutritional and health products. Chitosan has also been documented to be non-allergenic and it has been suggested that chitosan has anti-inflammatory properties.

Standard non surgical treatment of active periodontal disease includes supra and subgingival scaling and root planing with periodontal medical grade Gracey system steel curettes

The brush bristles of the test device (Labrida BioClean®, LABRIDA, Oslo, Norway) are made of the biopolymer chitosan

Difference between test and control groups in change in inflammation tested by measuring pocket probing depth (PPD) and Bleeding on Probing (BoP). Probing pocket depths will be recorded at 6 sites around each included tooth using a regular mm scale periodontal probe according to the examiners preferences. Bleeding on probing at the included sites will be assessed using a three-graded index within 30 seconds following probing of the pocket. A score of 0 represented no bleeding, 1 represented isolated minimal bleeding spots, 2 represented blood forming a confluent red line on the margin and 3 represented heavy or profuse bleeding This will be done to assess the clinical efficacy of the Labrida BioClean® biodegradable brush used as mechanical debridement device for treatment of advanced periodontal disease (2017 World Workshop Stage III and IV Grade B). Primary end-point is reduction in periodontal disease as measured clinically up to three months after therapy.

Difference between test and control groups in change in periodontal attachment loss tested by measuring clinical attachment loss and bone level differences on radiographs. This will be done to assess safety of Labrida BioClean® by evaluating the occurrence of adverse events. attachment level (CAL) measurements and radiographs. CAL will be assessed using a regular periodontal mm graded probe (Michigan O with Williams marking) with a force of approximately 20 N (experienced periodontal examiner). Bone attachement on intraoral radiographs at baseline and 6 and 12 months will be compared.