Artificial Intelligence-Enhanced Three-Dimensional Reconstruction of Combined Horizontal and Vertical Ridge Deficiencies Using Allogenic Dentin Block Versus Shell Tooth Graft Combined With Simultaneous Implant Placement

Severe periodontitis, trauma, and long-term edentulism can cause significant resorptive alterations of the alveolar ridge, leading to severe bone defects in the esthetic zone. Careful hard and soft tissue evaluation prior to implant surgery is important to restore proper function and esthetics. Horizontal, vertical, or combined ridge defects after extraction significantly influence dental implant placement and its long-term stability, as well as the final esthetics outcome.

Under natural conditions following a tooth extraction, the alveolar bone around the empty socket would undergo resorption and the alveolar ridge would recede in height and width. Besides leading to aesthetic and functional issues, the reduced bone volume would also cause insufficient support to the dental implant, causing the implant to become loose and unstable. For patients facing such issues, alveolar ridge augmentation is necessary to regenerate the bone tissue and restore the alveolar ridge so as to ensure the long-term stability of the implant.

Although a large number of alloplastic, allogenic or xenogenic bone substitute materials are available for reconstruction of the alveolar crest, the use of autogenous bone is still considered the gold standard. Autogenous bone has excellent osteoinductive, osteoconductive and osteogenetic characteristics; immunological reactions or the transmission of diseases can be safely avoided, and predictable augmentation results can be obtained.

For several years, the use of dentin as an alternative autogenous material for alveolar crest reconstruction and the grafting of bone deficits has been described and investigated in animal experiments and clinical studies. Dentin is a suitable grafting material because it is very similar to bone in its organic and inorganic composition. Similar to the alveolar bone, about 90% of the organic substance of dentin consists of type I collagen. Also, osteogenetically relevant structural proteins, such as osteocalcin, osteonectin, phosphoprotein and sialoprotein, can be found in dentin. Moreover, dentin contains osteogenetically active factors, including bone morphogenetic protein 2 (BMP-2), tissue growth factor-ß (TGF-ß) and insulin- like growth factor-2 (IGF-2). As in alveolar bone, the inorganic components of dentin consist of various calcium phosphates such as hydroxylapatite, ß-tricalcium phosphate, octacalcium phosphate and amorphous calcium phosphate. Compared with autogenous bone, the use of dentin offers the advantage of avoiding the harvesting procedure and the possible resulting donor site morbidity with promising clinical and histological results owing to its inherent osteoinductive and osteoconductive capacity. In comparison to autogenous bone block graft, dentin grafts also show significantly less resorption.

However, autogenous dentin graft has limitations despite its proven bone-formation capacity: dependence of the quantity on the number of teeth indicated for extraction and the condition of the extracted teeth, lack of a standard method to process autogenous dentin graft, and patient preference. Therefore, the application of dentin graft material from other individuals- allogeneic dentin graft-has been considered as an alternative autogenous dentin graft. Allo-dentin graft was conceptualized from the demineralized bone matrix, which was largely developed and defined for the bone induction principle, which states that a protein macromolecule in dentin and bone induces the differentiation of mesenchymal cells into osteoblasts; this was postulated by Urist in 1965. The Allo-dentin graft is a refined allograft that has osteoinductivity and has been clinically used since the 1980s. Very few studies have investigated the application of Allo-dentin graft as bone substitutes for bone graft surgery. The narrative review of revealed that Allo-dentin graft has demonstrated a great potential for osteoinductivity in extraskeletal sites, maximum clinical safety and efficacy without antigenicity nor provoked immunologic reactions.