Customized bone blocks need CBCT and digital software to design the block needed to rehabilitate. Some advantages are reduced surgical time and better adaptation of the graft, leading to less complications.

Objectives: The primary aim of this study is to determine the bone regeneration capacity through a histological study and the bone volumetric changes of allograft bone blocks in the posterior site of the mandible. The secondary outcome will be to assess the survival and success rate of dental implants placed in the allograft regenerated area.

Materials and Methods: After studying the CBCT to regenerate the posterior sites of the mandible, the investigators will design CAD/CAM freeze- dried bone allograft to fit exactly on the defect morphology that the patients present. A full thickness flap will be released to have a correct access of the defects. The sterile blocks have to fit perfectly on the defect and fixed by screws. Covered with resorbable membranes fixed with pines and suture. 4 months later, 2nd CBCTwill be performed. During the implant surgery, a bone trephine will be removed and sent into a Laboratory to make a histological study of the bone block for histomorphometry. After 3 months, second-stage surgery and healing caps will be placed if needed. Impressions will be taken 2 weeks after to perform the final crowns.

Allogenic bone blocks are a great bone regeneration technique option comparing to autologous regeneration treatments. There are several techniques of vertical guided bone regeneration but also have a large number of complications and failures. Some of the advantages of Customized Allograft Bone Blocks are: less invasive, causes less morbidity and resorption of the recipient site. Non resorbable membranes with particulate grafting material and autologous bone blocks are technically demanding and difficult to achieve stability to create new bone. Customized bone blocks need CBCT and digital software to design the block needed to rehabilitate. It is important to place the implants in an ideal prosthetic position to achieve excellent long-term results. Implant supported prosthesis can be contraindicated because of the lack of bone. Looking in to the classification of CAWOOD and HOWEL type 5 bone need bone augmentation techniques. In some cases, increasing the difficulty with the superficialization of the alveolar nerve. Some advantages are reduced surgical time and better adaptation of the graft, leading to less complications. The use of autogenous bone increases the risk of damaging anatomical structures increasing the morbidity, however thanks to allograft the investigators can avoid these problems. There are many different types of allografts, fresh-frozen bone (FFBA), freeze-dried bone (FDBA), demineralised freeze-dried bone allograft (DFDBA) and mineralised processed bone (MPBA). The allograft used for this study is a cellular cancellous bone material mechanically and chemically processed and sterilised by irradiation. This allogenic biomaterial has an osteoconductive property which facilitates the cell migration and proliferation for neoformation.

Study design A prospective controlled clinical trial will be conducted.

Residents of the International Master in Oral Surgery will perform the surgical and prosthodontic final rehabilitation procedures. All the included patients will sign an appropriate inform prior to any study-related actions. Firstly, an intraoral digital impression with intraoral scanner will be taken and a diagnostic wax-up will be performed. Subsequently, a cone-beam computed tomography scan would be taken in the specific area to be treated. After studying the CBCT to regenerate the posterior sites of the mandible, the investigators will design CAD/CAM freeze- dried bone allograft to fit exactly on the defect morphology that the patients present. A full thickness flap will be released to have a correct access of the defects. Releasing incisions will be performed to achieve the correct closure of the flap. The sterile blocks have to fit perfectly on the defect and fixed by screws. Covered with resorbable membranes fixed with pines and suture. 4 months later, photographs, periapical xrays digital impressions and 2nd CBCT will be performed. During the implant surgery, a bone trephine will be removed and sent into a Laboratory to make a histological study of the bone block for histomorphometry. After 3 months, second-stage surgery and healing caps will be placed if needed. Impressions will be taken 2 weeks after to perform the final crowns.

Inclusion Criteria:

1. Signed informed consent
2. Overall, healthy subjects (ASA1 and 2)
3. Females and males of at least eighteen-years
4. Requiring a posterior mandible rehabilitation with a minimum of 2 dental implants
5. Able to follow instructions and attend a regular compliance

Exclusion Criteria:

1. Acute local infection
2. Untreated periodontal disease assessed by Socransky et al. parameters (≥ 2mm clinical attachment loss in two consecutive visits within 1 year)
3. Drug and/or alcoholic dependencies
4. Medical conditions contraindicating implant surgery
5. History of head and/or neck radiation
6. Bisphosphonate therapy