Investigations in bone augmentation in dental implantolog

The greatest challenges in the surgical aspects of dental implant treatment relate to the diagnosis and treatment of alveolar ridge defects. There are three basic methods of augmenting deficient ridges to provide sufficient bone bulk to permit implant placement, ridge expansion, implant placement combined with simultaneous augmentation of the deficient ridge, and ridge augmentation followed several months later by implant placement as a separate procedure. Ridge augmentation involves the use of autogenous bone or of allogenic materials. It is accepted that autogenous bone is the best augmentation material, but allogenic materials have an important and developing role in dental implant surgery. Several such materials are in current clinical use, but they remain to be fully evaluated in the long term. The relative merits of carrying out implant placement and augmentation procedures separately or simultaneously also remain to be fully evaluated. Augmentation of bone dehiscences or atrophy frequently involves the use of barrier membranes, which protect the augmentation material and foster bone regeneration. Recently, resorbable membranes, which do not need to be removed following healing, have been developed. This thesis reports the results of both clinical and laboratory research with augmentation materials and resorbable membranes. The laboratory investigations compare the healing patterns of autogenous bone grafts and various allogenic materials when applied to cranial bone defects, and also in relation to the augmentation of bone dehiscences adjacent to simultaneously placed dental implants in the rabbit tibia. 174 specimens in 54 animals were examined. In addition, the results of experiments with new resorbable barrier membranes manufactured in sheet and mesh form from polydioxanone (PDS) are reported. These investigations indicate that both forms of PPS membrane are suitable for use in augmentation surgery. The structure of the mesh form is such that the smooth, rather than the fibrillar surface should be applied towards the augmentation site, to avoid reduction in the augmentation volume, which may be due to the contractile effects of fibroblast activity during healing. In cranial defect experiments, none of the allogenic materials had any osteoinductive effects. In the absence of an augmentation membrane bone formation was poor. When membranes were employed HTR, was associated with the poorest response in terms of bone regeneration. With hydroxyapatite (HA), bioglass and biocoral, bone deposition between the particles occurred if barrier membranes were employed, but some fibrous tissue persisted at the centre of the defect. When these materials were used in combination with Goretex or resorbable barrier membranes to augment dehiscences adjacent to dental implants in rabbit tibia, satisfactory bone regeneration occurred. In both cranial and implant dehiscence experiments, the use of particulate autogenous bone was associated with excellent bone regeneration. In the clinical study, after one year in function, success rates of 97.1% and 99.4% (implants) and 97.9% and 100% (prostheses) for 243 Frialit 2 and 347 IMZ implants respectively, compare favourably with other studies. In 106 localized augmentation procedures, the success using allogenic materials reflected the animal studies, although the morphology of the ridge defect was found to be an important influence on success. In this thesis a classification of localized defects is proposed as an aid to treatment planning. 69 cases of iliac crest grafting to atrophic jaws are reported. Implants were placed after graft healing. Mean peri-implant bone loss after one year was 1mm, and implant success was 100% in the mandible and 98.3% in the maxilla, which compares favourably with other reports. 55 cases of major sinus grafting were followed by the placement of 140 implants after healing of the grafts. None of the implants failed within the period of the study. The ultimate purpose of such research is to improve the treatment of patients. In summary, this thesis analyses implant treatment outcomes involving 590 dental implants in situations which include routine implant placement and ridge augmentation ranging from single implant situations to the augmentation of severely atrophic edentulous jaws.