ve been reviewed in detail elsewhere and are only summarized below.
Material
Commercially pure titanium is clinically the best domment6d material to achieve osseointegration. Its surface oxides are very stable in the bony environment and corrosion is minute. No allergic reactions to this material are known. Consequently, it is highly biocompatible and, moreover, easy to machine.
Design
A screw - shape gives surface enlargement for interaction with the recipient bone tissue, enhances initial stabilization, provides resistance to shear forces, and distributes load well within the bone. In contrast to other designs, screw - shaped titanium implants have been shown to become totally oseointegrated along their entire circumference in dogs.
Surface properties
The interfacial reactions of the bone tissue are greatly governed by the chemical and physical properties of the implant surface. The passivating titanium oxides and a certain degree of surface roughness promote osseointegration.
Surface purity
For obvious reasons, the desired surface properties should not be changed by microbiological or metallic contamination during any part of the manufacturing, storing, transportation, sterilization, and surgery processes.
Fixture site positions
The most important principle is to achieve good initial stability and full coverage of the fixtures in well - vascularized, highly osteogenic bone. Bicortical initial stabilization should be the goal. If this is not possible, one must resort to at least monocortical fixation. Possible areas for bi - and monocortical fixation have been reviewed under "Local anatomy. " The additional stability that can be achieved by engaging the lingual cortical plate of the mandible should be used whenever possible.
For adequate load distribution to the bone and the fixtures themselves, the latter should be spread well apart and placed along a curve or any arrangement other than a straight line. The center and the ends of the tentative suprastructure should be well supported. However, the final design and extension should await the experience of bone quality from fixture and abutment surgeries. No figure for any optimal interfixture distance can be given because this depends on the vitality and mechanical capacity of both the fixture sites and the interfixture bone and may vary from one area to another. A clinical rule of thumb is, however, that the interfixture distance should not be less than one fixture diameter. This approach also facilitates later hygiene efforts between abutments.
The anterior loop of the mandibular canal and the nasopalatine duct should be avoided so as not to interfere with nerve function and osseointegration.
Number of fixture sites
The available bone volume in different areas can be reasonably well assessed preoperatively by palpation and, especially, by tomographic radiographs. The same is not true for bone quality, which can be adequately determined only' after some drilling has been performed. One may find, for example, that areas planned as fixture sites are totally unsuitable due to the presence of empty o
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