Post Extraction Changes Following Ridge Preservation Using Partially Demineralized Dentin Block Versus Xenograft

Objective of the study: The aim of this study is to evaluate post extraction hard tissue changes following ridge preservation using Partially Demineralized Dentin Block versus Xenograft 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: Patients who fulfill 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.

Preoperative preparation: A thorough preoperative assessment of all patients will be carried out, including history taking, clinical examination, and radiographic examination.

History: Each patient will be interviewed to obtain a comprehensive history.

Clinical examination: Proper intraoral examination will be done to evaluate the following parameters for the tooth of interest: 1) Restorability of the tooth. 2) Periodontal condition of the tooth to be extracted and the adjacent teeth.

Radiographic examination:

1. Periapical radiographs will be done to rule out the presence of any periapical infection and evaluate the presence of caries or periodontal disease in the adjacent teeth.
2. In cases that meet the inclusion criteria, cone beam computed tomography (CBCT) will be taken at three time points: before the surgery, immediately after socket preservation, and after 6 months. The CBCT before the surgery will be used to assess the type of socket, while the baseline CBCT immediately after socket preservation will be used to evaluate the horizontal ridge width at 2, 4, and 6 mm below the most coronal aspect of the crest, and buccal and palatal ridge height. The CBCT taken after 6 months will serve to superimpose the two scans and assess long-term changes.

Initial Therapy: The initial therapy will consist of periodontal treatment (phase I therapy) including supragingival scaling, subgingival debridement if needed, adjustment of faulty restorations, and polishing. Mechanical plaque control instructions for each patient include brushing and interdental cleaning techniques.

Patients will be randomly assigned to one of the treatment groups:

• Test Group: Ridge preservation using Partially Demineralized Dentin Block in the esthetic zone.
• Control Group: Ridge preservation using Xenograft in the esthetic zone.

Surgical Procedure:

Atraumatic extraction:

• The patient will rinse with 0.12% Chlorhexidine (Hexitol, ADCO Pharma Co, Egypt).
• The operator will administer 4% articaine hydrochloride with 1:100,000 epinephrine (Septodent Co. for Pharmaceuticals, France).
• Flapless and atraumatic tooth extraction will be initiated by making an intrasulcular incision using a 15c blade.
• Next, a periotome will be used to sever the periodontal ligament (PDL) fibers, followed by the use of a straight elevator and extraction forceps for the extraction process.

In the test group, the autogenous partially demineralized dentin graft will be prepared as follows: A high-speed fine finishing stone and saline irrigation will be used to clean the tooth and remove any decay, restoration, or foreign materials. The tooth will be rinsed twice in phosphate buffered saline. The tooth will be dried using air, then ground and partially demineralized with the Tooth Transformer device following the manufacturer's protocol. Dentin particles will be obtained with dimensions of 400 - 800 μm.

Dentin block preparation: During the preparation of partially demineralized dentin, Leukocyte-Platelet Rich Fibrin (L-PRF) membranes will also be prepared. Vacutainer tubes without anticoagulant (red cap, glass coating) will be used to collect four 10-cc blood samples, which will then be immediately centrifuged at 2700 rpm for 12 minutes using the IntraSpin centrifuge (IntraLock, Florida, USA). Additionally, two extra blood samples will be collected in 9-cc non-coated vacutainer tubes without anticoagulants (white cap). These samples will be centrifuged at 2700 rpm for 3 minutes. The resulting yellow fluid (liquid fibrinogen) at the top of the white cap tubes will be carefully aspirated using a sterile syringe, while avoiding red blood cells.

The L-PRF clots obtained after 12 minutes of centrifugation will be placed in the Xpression box (IntraSpin, Intra-Lock, Florida, USA) for 5 minutes to allow gentle compression (by gravity) into membranes.

To prepare the L-PRF 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 L-PRF pieces, forming a sturdy block known as the "dentin block," which serves as a convenient and compact graft.

Alveolar ridge preservation: Following a thorough cleaning procedure, the sockets will be carefully packed with customized "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, which will extend approximately 2 mm along the entire envelope formed between the periosteum and the bony boundaries of the sockets (in a 360° fashion). To ensure stability and prevent displacement, the wounds will be secured using non-resorbable sutures. It's important to note that the purpose of the sutures is to maintain the position of the grafts and membranes rather than closing the wounds entirely.

In the control group: The same extraction and socket debridement procedure will be performed. Following that, the extraction socket will be thoroughly filled with deproteinized bovine bone mineral, and a collagen membrane will be employed to cover the socket. The membrane will be shaped to extend 2-3 mm beyond the margins of the extraction socket and positioned just beneath the marginal mucosa. To ensure its stability, a cross-suture will be performed, securing the membrane in place.

The sutures will be removed two weeks after the surgery.

Biopsy collection: After a healing period of 6 months, at the time of implant placement, a biopsy will be taken from the central area of the grafted site using a 3-mm trephine bur. The biopsy will be promptly fixed in 10% neutral buffered formalin, followed by dehydration through a series of alcohol baths with increasing concentrations (ranging from 50% to 100%). Subsequently, the specimen will be embedded in paraffin. Finally, a tissue section with a thickness of 4 μm will be prepared and subjected to hematoxylin-eosin staining for subsequent histological analysis.

Outcomes: Radiographic vertical buccal bone changes, vertical palatal bone changes, horizontal bone changes, percentage of new vital bone formation, percentage of residual bone graft, and implant primary stability