Ridge alterations following tooth extraction and implant placement

The purpose of the present series of investigations was to study the healing following tooth extractionand implant placement. In an animal model, the healing sequence of tooth extraction sites (Study I), theinfluence of the periodontal ligament (PDL) on the healing of extraction sockets and the effect ofvarious biomaterial on the healing of bone defects (Study II), and the healing of different bone blockgrafts placed on the surface of a narrow ridge (Study III) were investigated. In longitudinal clinicalstudies, the hard and soft tissue alterations following the placements of dental implants in the healedalveolar ridge (Study IV) and the bone alterations in relation to horizontal and vertical inter-unitdistances (Study V) were studied.It was demonstrated that: The healing of the extraction socket involved a series of events initiated by the formation of acoagulum that was replaced by a provisional matrix, woven bone, lamellar bone and bone marrow.During the healing process a cortical bone bridge formed that closed the socket. Sockets that following tooth extraction had their PDL tissue removed exhibited similar featuresafter 3 months of healing as sockets which had the PDL retained. The tissues present in theextraction site were more mature than those present in a surgically produced defect. The Bio-Oss®Collagen augmented defect exhibited less wound shrinkage than the non-augmented defect. A highpercentage of the Bio-Oss® particles were in direct contact with newly formed mineralized bone. Grafts of autologous cortical bone, placed on the surface of a narrow ridge, showed markedresorption during healing. A similarly placed graft of Bio-Oss® retained its dimension, howeverlimited amounts of new bone formed within the biomaterial. Following implant placement surgery in an area of a healed alveolar ridge, remodeling of the bonetook place that was manifested in diminished dimensions, both horizontally and vertically, at thefacial aspect of the implant. An apical displacement of the soft tissue margin at the facial aspect ofthe implant was observed, while an improved papilla fill was seen at proximal sites. Vertical and horizontal differences in implant positions influenced the bone alterations in the interimplantarea during the first 3 years of loading. The data failed to show corresponding relationshipsfor the bone changes at the proximal area between the implant and the neighbouring tooth