The aim of this 12-month clinical study is to treat patients affected by gum disease (periodontitis) by a minor gum surgery that aims to reduce the depth of the gum pockets. In particular, the study will compare two types of gum surgery, one based on the use of a product derived from the patients' own blood (PRGF, platelet autologous concentrate), and the other based on the use of an animal-derived bone graft and membrane that have been in the market for the past 30 years. Both procedures aim to regenerate bone and gum tissue that is damaged by the disease. 74, ≥ 25-year-old, otherwise healthy, patients affected by gum disease will be recruited at the Barts and The London Dental Hospital. Participants will be randomly (by chance) assigned to receive one of the two treatments. Throughout the study, we will assess gum's health by taking some measurements around teeth and gums. In addition, we will use non-invasive technologies to assess changes in temperature, blood flow and face's swelling at different time-points. Patients will be given specific questionnaires to evaluate their preferences and the impact that each surgical treatment had in their everyday life. One intra-oral x-ray will be performed before the surgery and after 12 months to assess if new bone has formed around the teeth involved in the surgery, as per standard procedure.

This is a randomized, single-blind, parallel-group controlled trial comparing the efficacy of GTR and PRGF ENDORET in the treatment of periodontal intrabony defects. The trial will follow the recommendations of the Consolidated Standards of Reporting Trials (CONSORT) statement.

No negative control (SPPF alone) has been considered for this project since several studies have demonstrated that guided tissue regeneration (GTR) associated or not with bone grafts results in better clinical outcomes than access flap alone in the treatment of periodontal intrabony defects.

The study consists of 9 visits over a minimum period of 13 months and will take place at the Centre for Oral Clinical Research (COCR), at the Institute of Dentistry, Barts and The London School of Medicine and Dentistry, Queen Mary University of London.

Visit 1 - Baseline -

• Informed consent, medical/dental history and demographics
• Record concomitant medications and smoking history
• Height and weight measurement
• Standardised peri-apical x-ray in the area selected for the study
• Periodontal assessment by a blind and calibrated examiner, consisting of full mouth PPD, REC, BOP, mobility and furcation involvement will be recorded. PPD, REC, plaque and BOP will be recorded at 6 sites per tooth.
• Intra-oral 3D scan in the area selected for the study
• PROMs assessment (OIDP, and Global ratings of Periodontal Health and Quality of Life, EuroQoI-5D-5L)
• 3D extra-oral morphometric and Thermal scan
• Laser speckle contrast imaging, LSCI
• Pre-treatment hygiene phase, including supragingival scale and polish of all teeth and oral hygiene instructions
• Randomization to one of the two treatment groups by the study co-ordinator. The treatment allocation will be concealed in an opaque envelope. A treatment visit will be scheduled within the following 6 weeks.

Visit 2 - Surgical intervention - (within 6 weeks from Visit 1)

• Query to update medical/dental history and record adverse events and/or concomitant medications
• Recording of the number of defect walls
• Study treatment according to randomization (PRGF ENDORET or GTR)
• Intra-oral 3D scan in the area selected for the study (scan taken immediately after surgery)
• Record of surgery time
• Post-surgical instructions
• 3D extra-oral morphometric and thermal scan (scan taken immediately after surgery)

Visit 3 - 2 days follow-up - (2 days ±1 days from Visit 2)

• Query to update medical/dental history and record adverse events and/or concomitant medications
• Visual assessment of gingival healing and recording of early healing index (EHI)
• Laser speckle contrast imaging, LSCI
• Intra-oral 3D scan in the area selected for the study
• 3D extra-oral morphometric and Thermal scan
• PROMs assessment (Evaluation of global changes in quality of life and evaluation of patient perception about therapy)

Visit 4 - Suture removal - (7 days +3 days from visit 2)

• Query to update medical/dental history and record adverse events and/or concomitant medications
• Visual assessment of gingival healing and recording of early healing index (EHI)
• Laser speckle contrast imaging, LSCI
• Intra-oral 3D scan in the area selected for the study
• 3D extra-oral morphometric and Thermal scan
• Suture removal
• Supra-gingival polishing and reinforcement of oral hygiene instructions
• PROMs assessment (Evaluation of global changes in quality of life and evaluation of patient perception about therapy)

Visit 5 - 2 weeks follow up visit- (14 days ±3 days from visit 2)

• Query to update medical/dental history and record adverse events and/or concomitant medications
• Visual assessment of gingival healing and recording of early healing index (EHI)
• Laser speckle contrast imaging, LSCI
• Intra-oral 3D scan in the area selected for the study
• 3D extra-oral morphometric and thermal scan
• Supra-gingival polishing and reinforcement of oral hygiene instructions
• PROMs assessment (Evaluation of global changes in quality of life and evaluation of patient perception about therapy)

Visit 6 - 4 weeks follow up visit- (28 days ±3 days from visit 2)

• Query to update medical/dental history and record adverse events and/or concomitant medications
• Visual assessment of gingival healing
• Intra-oral 3D scan in the area selected for the study
• 3D extra-oral morphometric and Thermal scan
• Supra-gingival polishing and reinforcement of oral hygiene instructions
• PROMs assessment (Global ratings of Periodontal Health and Quality of Life, Evaluation of global changes in quality of life, and Eevaluation of patient perception about therapy and EuroQoI-5D-5L)

Visit 7 - 3 months follow up visit- (3 months ±7 days from visit 2)

• Query to update medical/dental history and record adverse events and/or concomitant medications
• Recording of PPD, REC, BOP, PI and mobility on the tooth involved in the surgical intervention and 2 adjacent teeth by a blind and calibrated examiner
• PROMs assessment (OIDP, Global ratings of Periodontal Health and Quality of Life, and eEvaluation of global changes in quality of life and EuroQoI-5D-5L)
• Supra-gingival polishing and reinforcement of oral hygiene instructions

Visit 8 - 6 months follow up visit- (6 months ±7 days from visit 2)

• Query to update medical/dental history and record adverse events and/or concomitant medications
• Recording of PPD, REC, BOP, PI and mobility on the tooth involved in the surgical intervention and 2 adjacent teeth by a blind and calibrated examiner
• Supra-gingival polishing and reinforcement of oral hygiene instructions
• PROMsS assessment (OIDP, Global ratings of Periodontal Health and Quality of Life, and eEvaluation of global changes in quality of life and EuroQoI-5D-5L)

Visit 9 - 12 months follow up visit- (12 months ±7 days from visit 2)

• Query to update medical/dental history and record adverse events and/or concomitant medications
• Periodontal assessment by a blind and calibrated examiner, consisting of full mouth PPD, REC, BOP, mobility and furcation involvement will be recorded. PPD, REC, plaque and BOP will be recorded at 6 sites per tooth.
• PROMS assessment (OIDP, Global ratings of Periodontal Health and Quality of Life, and eEvaluation of global changes in quality of life and EuroQoI-5D-5L)
• Supra-gingival polishing and reinforcement of oral hygiene instructions
• Standardised peri-apical x-ray in the area selected for the study

Study randomisation and treatment allocation Following completion of the preparation treatment all individuals enrolled into the study will be randomly assigned to one of the treatment groups.

• Simplified Papilla Preservation Flap (SPPF) and guided tissue regeneration (GTR) with a porcine collagen membrane and a deproteinized bovine bone substitute.
• Simplified Papilla Preservation Flap (SPPF) and PRGF ENDORET.

A balanced random permuted block approach (4-unit block size) will be used to prepare the randomisation tables. Minimisation will be carried out to facilitate balancing of smokers in each group.

Allocation to treatment will take place via the study coordinator (or one of their delegate). Treatment allocation details will be concealed in an opaque envelope at the study site.

At the time of enrollment, each participant will be sequentially issued a subject ID. The subject ID consists of two initials and a number. The ID number will consist of three digits and will be assigned in ascending numerical order beginning with 001.

Inclusion Criteria:

• Systemically healthy males and females ≥25 years old
• Willingness to read and sign a copy of the Informed Consent Form after reading the Patient Information Sheet, and after the nature of the study has been fully explained
• Clinical evidence of periodontitis, with one interdental area of PPD ≥6mm, BOP, and attachment loss ≥6mm, with associated intrabony defect ≥3mm in any area of their mouth (excluding third molars and distal of second molars)
• Full mouth bleeding and plaque scores (FMBS and FMPS) <25%recorded within the previous 6 weeks
• Non-surgical treatment completed within 6 months prior to assessment for eligibility

Exclusion Criteria:

• Medical history that includes diabetes type 1 or hepatic or renal disease, or other serious medical conditions or transmittable diseases (e.g. cardiovascular disease or AIDS).
• Antibiotic or anti-inflammatory therapy during the month preceding the baseline exam.
• In chronic treatment (>2 weeks) with anticoagulants, corticosteroids or other medications that can severely impact on bone formation
• History of alcohol or drug abuse.
• Smoking ≥10 cigarettes a day
• Self-reported pregnancy or lactation (this criterion is due to oral tissue changes related to pregnancy and nursing, which can affect interpretation of study results).
• Other severe acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with trial participation or investigational product administration or may interfere with the interpretation of trial results and, in the judgement of the investigator, would make the subject inappropriate for entry into this trial.
• Periodontal surgery in the same area selected for the study within the past 12 months.

Due to the nature of the intervention, both participants and clinicians performing the surgical intervention will be unblinded. Conversely, outcome examiners will be blinded to treatment allocation.