Biomaterials Applicable for Alveolar Sockets Preservation: In Vivo and In Vitro Studies

Bone density and quantity are primary conditions for the insertion and stability of dental implants. In cases of a lack of adequate maxillary or mandibulary bone, e.g. in terms of front to back depth or thickness, bone augmentation will be necessary. Lack of bone or bone defects can be caused by inflammation, congenital malformation, trauma or oncological surgery. Several procedures and materials for augmenting bone height have been developed to overcome the problem of a reduced amount of bone. In dentistry, bone substitution materials were used for the following applications: (1) socket preservation; (2) periodontal defects; (3) third molar extraction sites to support 2nd molars; (4) ridge augmentation; (5) defects following cyst removal / apicoectomies; (6) sinus lifts; (7) distraction osteogenesis; and (8) implant dentistry. The treatment of bone-defects and socket preservation include autografting (from one location to another within the same individual), xenografting (from a donor of another species) and allografting (from a genetically dissimilar member of the same species) cancellous bone. After blood, bone is the most commonly transplanted tissue. Worldwide, an estimated 2.2 million grafting procedures are performed annually to repair bone defects in orthopaedics, neurosurgery, and dentistry (Giannoudis et al. 2005). The increasing number of grafting procedures and the disadvantages of current autograft and allograft treatments (e.g. limited graft quantity, risk of disease transmission) drive the quest for alternative methods to treat bone defects. The use of synthetic bioactive bone substitute materials is of increasing importance in modern dentistry as alternatives to autogenous bone grafts. Various alloplastic bone substitution materials of different origin, chemical composition, and structural properties have been investigated in the last years. The materials commonly used in all approaches are ceramics, polymers or composites (Burg et al. 2000). These alloplastic materials are either absorbable or non-absorbable, as well as naturally derived or synthetically manufactured (Figure 1). Various types of biomaterials (minerals and non-mineral based materials as well as natural and artificial polymers) with different characteristics have been used for studying ossification and bone formation. For example, calcium phosphate ceramics include a variety of ceramics such as hydroxyapatite, tricalcium phosphate, calcium phosphate cement, etc. These mentioned ceramics have excellent biocompatibility and bone bonding or bone regeneration properties. Recently non-biodegradable and degradable membranes have been