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Bone Grafting
Occasionally because of infections, shrinkage of bone following extractions
or simply from the wearing of a denture, there is insufficient volume
of bone into which an implant can be placed in the ideal position. In
such cases, the options are to either widen the bone using special techniques
at the time of implant placement or re build the bone using a bone graft.
For smaller amounts of bone it is possible to take bone from the wisdom
tooth area of the lower jaw or from under the lower incisor teeth. This
is carried out in much the same way as a tooth extraction under local
anaesthetic in the practice.
For larger amounts of bone, for example when there has been complete
collapse from gum disease or long term denture wearing, it can be necessary
to take the bone from outside the mouth. This would require a general
anaesthetic and an overnight stay in hospital. The reason for using
bone grafts in many of these situations is so that the natural contours
of the original teeth and gums can be reproduced. However if it is felt
that bone grafting is inappropriate then the options are to either accept
longer teeth or use gum coloured acrylic or porcelain to mimic the missing
gum. The ideal option however is natural, healthy, regenerated bone.
It is usually necessary to leave bone grafts for up to four months to
heal before implants are inserted in the normal way.
1 Canine to be extracted.
2 Resorbed Ridge before graft.
3 Expanded Ridge.
4 Porcelain crown two years after
treatment.
1 Infected canine tooth.
2 Defect following extraction.
3 Grafted bone.
4 Implant, post and crown two years
after treatment.
Biomaterials
In many cases rather than using natural bone grafts it is possible to
use a range of biomaterials to plump out or fill in around an already
inserted implant. These materials come from a variety of sources including
bovine, human bone and synthetic materials. Careful consideration is
given to the use of such materials and discussed on an individual basis,
but are a key asset in the treatment of these cases. Their use is termed
Guided Bone or Guided Tissue Regeneration.
Sinus Augmentation
Towards the back of the upper jaws are the sinus spaces which are positioned
above the remaining residual jaw bone. Following tooth removal the sinus
spaces frequently increase in size and on some occasions in order to
place implants in this area it is necessary to re position the sinus
lining at a higher level. This is done under local anaesthetic in the
surgery and involves a procedure called sinus augmentation. The sinus
lining is raised by a bone graft or biomaterial being introduced into
the void and allowed to form new bone. The implants can either be placed
at the same time as the augmentation or at a suitable time after healing
has taken place. This technique is an extremely predictable way of creating
new bone.
Special Tests
It is sometimes necessary to know the precise location and volume of
bone nerves and sinus spaces. This is possible with a CT scan. This
is carried out at a local hospital. CT scans are an invaluable diagnostic
aid, particularly where multiple implants are considered. They are so
accurate that it is possible to have 3D guides constructed that can
help determine exact implant positioning.
1 CT Scan with Diagnostic Guide.
2 Cross section of CT showing proposed implant
and abutment (post) position.
» Next section: The implant process
