nce and are supported by experimental animal studies. Thus, in a long - term study the group with the longest observation time had the lowest fixture survival rates. The major difference between this and the other groups was that it had considerably shorter healing periods than those recommended above. In the investigation by Johansson and Albrektsson using the rapidly bone - healing rabbit, only an average of 50% bone to fixture contact was observed after 3 months, and it took 12 months until there was an average of 85% such contact.
Direct loading
One experimental study has shown a bone - to fixture contact of 40% to 90% after 3 months, even when the implants were dynamically loaded directly after insertion. Presently, this observation cannot be taken as justification for any deviation from the present clinical routine of unloaded healing of the fixture sites.
Medications
The positive effects of the medicines (eg, calcium carbonate, antibiotics, and analgesics) recommended for postoperative use to promote osseointegration and healing have not been scientifically verified. Their use is extrapolated from general medical knowledge (eg, calcium for osteoporosis).
Abutment surgery considerations
Choice of abutments
The longest possible abutments with regard to esthetics and, for intraoral purposes, phonetics should be showed to facilitate access to the periabutment area for hygiene purposes.
Managing periabutment soft tissues
Abutments should penetrate through thin attached gingiva or nonmobile oral mucosa or skin. For oral purposes, attached gingiva may be strictly necessary only on the lingual aspect of mandibular abutments to protect the vulnerable mucosa in the floor of the mouth from frictional movements against the abutments or from excessive hygiene efforts. However, a prerequisite for healthy marginal soft tissue is always good oral hygiene and no exposed fixture threads.
The topic of marginal oral soft tissue mobility was reviewed by Adell et al. If stabilization of oral periabutment mucosa is needed, conventional sulcoplasties or mucosal grafts are recommended after the bridge is finished so that additional stabilization of healing marginal tissues can be obtained by a surgical pack.
Transcutaneous passage of osseointegrated fixtures requires more stability in the periabutment soft tissues. This should be brought about by considerable thinning of adjacent tissues and/or a split skin graft.
Losing mseointegration
A clinically mobile fixture, be it due to a never established oseointegration or later to totally lost osseointegration, has never been observed to become stable/osseointegrated again. The only condition that may mimic true mobility with a fibrous sleeve around the fixture is when the supporting bone is mostly cancellous and not yet sufficiently remodeled. A minute elasticity may then be experienced and possibly misinterpreted. Fixtures supported in this manner are of course at great risk and could, moreover, transmit pressure to adjacent nerves. A few cases of unpleasant sensations following loading of such fixtures have been attributed to these circumstanc
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