Post Extraction Changes Following Ridge Preservation Using Partially Demineralized Dentin Block Versus L- PRF Block

• Objective of the study: aims to evaluate post extraction hard tissue changes following ridge preservation using partially demineralized dentin block versus L-PRF block in intact socket in the esthetic zone.
• Research Procedure:

Patients will be selected from the outpatient clinic of the Oral Medicine and Periodontology Department, Faculty of Dentistry, Cairo University.

• General operative procedures: The patients who fulfil the inclusion criteria will be enrolled. The nature of the study will be explained to each patient as well as the importance of compliance with pre- and post-operative instructions and follow-up visits. Each patient will be asked to sign an informed consent (appendix 1). After enrolment, periodontal and radiographic examination and patients with badly un-restorative tooth in the esthetic zone will be identified. These patients will undergo to mesio-distal distance between adjacent teeth, corono-apical height of bone, presence of labial undercut, dehiscence, or fenestration and Relation to adjacent teeth measurements using trans gingival probing technique, and preapical radiograph or CBCT .
• Initial Therapy: The initial therapy will consist of periodontal treatment (phase I therapy) including supra-gingival scaling, subgingival debridement if needed, adjustment of faulty restoration and polishing. The mechanical plaque control instructions for each patient include brushing and interdental cleaning techniques.
• Atraumatic extraction:
• Local anaesthesia will be administered via buccal and palatal infiltration prior to any surgical procedure.
• In both groups, flapless atraumatic tooth extraction will be performed which includes an intrasulcular incision using a 15c blade, then a periotome is inserted between the root and the surrounding bone in a wedging action all sides around the root. Afterwards, a small sized straight elevator will be used to luxate the root and a remaining root forceps will be used to deliver it. Lucas curette will be used to clean the extraction socket of any apical pathology and granulation tissue.
• In intervention group, the partially demineralized dentin graft will be prepared as follows: ✓ The extracted tooth will be decontaminated and cleaned with a diamond bur under abundant irrigation with physiological water. All filling materials (gutta-percha, composite, luting cements, etc.) will be removed with the outmost care. Subsequently, the tooth will be cut into fragments (5 × 5 mm) and will be dried using air and ground with the Tooth Transformer device following the manufacturer's protocol. Dentin particles will be obtained with a dimension of 400 - 800 μm.
• L-PRF membranes will be prepared as follows:
• Partially demineralized dentin particles will be obtained with a dimension of 400-800 μm.

At the same time, L-PRF membranes will be prepared. Four 10-cc blood samples will be collected in vacutainer tubes without anticoagulant (red cap, glass coating) and immediately centrifuged at 2700 rpm (408g) for 12 min (IntraSpin, Intra- Lock, Florida, USA).

• Two extra blood samples will be collected in 9-cc non-coated vacutainer tubes also without anticoagulants (white cap). These last samples will be centrifuged at 2700 rpm for 3 min only. The yellow fluid (liquid fibrinogen) at the top of the white cap tubes will be aspirated with a sterile syringe, avoiding red blood cells.
• The L-PRF clots obtained after 12 min of centrifugation will be placed in the Xpression box (IntraSpin, Intra-Lock, Florida, USA) for 5 min to gently compress (by gravity) into membranes.

To prepare the partially demineralized dentin block, the L-PRF membranes will be cut into small pieces and mixed with the dentin particles at a ratio of 2 membranes to 0.5 g of dentin, providing a 1:1 volume ratio. The liquid fibrinogen will be added to the homogeneous mixture, and while shaping the mixture into the desired form, it will be gently stirred for approximately 10 seconds.

Within a few minutes, the fibrinogen will convert into fibrin primarily from the activated blood platelets in the chopped L-PRF membranes. This process will effectively trap the biomaterial and the 16 L-PRF pieces, forming a sturdy block known as the "dentin block," which serves as a convenient and compact graft.

• Alveolar ridge preservation:
• After socket debridement, each socket will be carefully filled with "dentin blocks" that are shaped to match the individual size and contours of each socket. Once the grafts are properly adapted to the sockets, they will be covered with two layers of L-PRF membranes extending 2 mm in the envelope prepared between the periosteum and the bony borders of the socket (360° around).
• The wound will be secured using resorbable material interrupted sutures, not with the intention to close the wound, but simply to keep the graft and membranes stable in position.
• In the control group: The same procedure will be performed for preparing the L-PRF block by mixing the L-PRF membranes with xenograft.
• Biopsy collection:

After a 4-months healing period, at the moment of the implant placement, a biopsy from the core of the grafted site will be obtained using a trephine bur with an outer diameter of 3 mm and an inner diameter of 2.2 mm. The biopsy will be immediately fixed in 10% neutral buffered formalin and then dehydrated through baths of progressively more concentrated (from 50 to 100%) alcohol and subsequently embedded in paraffin. Finally, a tissue section of 4-μm thick will be prepared and stained with hematoxylin-eosin for histological analysis.

• Late implant placement:
• After complete bone healing of the extraction socket 6 months following tooth extraction, late implant placement will be performed.
• Local anesthesia in which Septocaine (Articaine hydrochloride 4% with 1:100000 Epinephrine) will be administered via buccal and palatal infiltration prior to any surgical procedure.
• In some cases, from both groups, a triangular flap design will be used which involves a midcrestal horizontal incision with an intrasulcular incision on each distal tooth to the edentulous area. Then, 2 vertical releasing incision will be made at the line angles of the adjacent teeth. This will be followed by full thickness flap elevation.
• Implant osteotomy will then be prepared using sequential drilling according to the manufacturer instructions, to allow implant placement in proper 3D prosthetic position. Finally, implant will be inserted into the prepared osteotomy.

Outcomes: Radiographic vertical buccal bone changes, vertical Palatal bone changes, horizontal bone changes, Percentage of new vital bone formation, Percentage of residual bone graft, Implant Primary Stability.

The results directly postoperative and 6 months postoperatively.