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prone to this condition, but a number of studies have shown high success rates of treatment with osseointegrated fixtures in women patients above 50 years of age. Osteoporosis as a possibly 13egative factor was, however, not separately analyzed. A number of non-insulin dependent diabetics have also been included in these materials with no overt influence on the outcome.
     Local host tissue conditions
     Local bone osteogenic and remodeling capacity plus the integrity of the covering soft tissues determine whether or not osseointegration will result after fixture installation, provided surgery is performed strictly according to basic recommendations. It should be emphasized that local host tissue conditions can vary considerably from one area to another within the same patient.
     Only areas covered by intact soft tissues should be chosen for the installation of fixtures. Consequently, all possible lesions in skin or mucosa (eg, eczema. candidasis, lichen planus, leukoplakia, erosions) should first be treated before fixture installation is attempted. The installation of fixtures under a mucosal or split skin graft must be considered more risky than beneath an intact integument. Such grafts' have a reduced resistance to mechanical wear, and their original placement has generally implied and interference with the bond supply to the periosteum.
     Local bone quantity and quality should ideally be made up of a well-vascularized-bone area, slightly longer than the fixture and with a diameter not less than 5 mm (for a standard 3.75mm diameter fixture). It is of the utmost important that the fixture achieves initial stability. This is best brought about if its marginal and apical parts are engaged in cortical bone. Any cancellous bone present should ideally have a high proportion of bony trabeculae further to support the fixture. Its cancellous compartments should contain an osteopoten endosteum and marrow tissue. Areas with empty or fatty marrow compartments should be avoided, as should sites with a small ratio of trabecula to soft tissue marrow.
     Possible areas with the ideal characteristics matching the positions and inclinations of fixtures as desired for the planned suprastructure should be sought. In the clinical situation, one or several of the following circumstances may influence tentative fixture sites.
     Local anatomy
     Not all areas in the maxillofacial region fulfill the above requirements. A good example is upper versus lower jawbone (Fig 7-l). The thin maxillary outer compact layer will contribute little to the stabilization of fixtures. Initial immobilization can then come only from the apical ends being engaged in the cortical nasal or maxillary sinus floor. Maxillary tuberosity areas are very soft, whereas the structural reinforcements of the midface - the canine, zygomatic, and pterygoid areas - provide better conditions for the initial stabilization of fixtures. Moreover, a triangular widening, reinforced by cortical bone, can frequently be found close to the incisive canal even in severely resorbed cases. This area is generally a good fixture site provided the myelin sheath of the nerve is not engaged. If this occurs, ossepintegration will not ensue.

Fig 7-1 Cortical linings, marked by arrows, sutable for the anchorage of fixtures to 本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。