If you have been missing a tooth or teeth for some time, or if there was a past infection in the area, you may have lost some of the bone that supported your tooth. Bone grafting is the process by which we build up a thin or shrunken jawbone. If you are considering an implant but dental x-rays and/or CAT scan show that you have a thin jawbone as a result of bone loss, then a graft will be necessary.
Another factor is that of aesthetics: if you have lost several teeth and have not replaced them then your facial jaw line may appear lined and ‘sunken in’. This aged appearance is both undesirable and unnecessary.
One way of preventing this is via a dental implant, which may have to be combined with a bone graft.
If you require several implants then the amount of bone to be grafted will increase in proportion to the number of implants.
What causes bone loss?
Your jaw may show advanced bone loss as a result of the ageing process, prolonged denture wear, missing teeth, periodontal gum disease, infection or as a result of an accident.
If you lose a tooth through accident or injury then what tends to happen is that the area around the missing tooth recedes and the jawbone itself starts to shrink.
Our teeth help to maintain bone density by a natural renewal process. This ensures normal bone growth and healthy tooth tissue.
Types of bone graft
There are four types of bone grafts:
- Autogenous or Autografts
This uses natural bone, which is taken from a human donor rather than a part of your own body. There are special ‘bone banks’ for this purpose where people have donated bone samples – which are very similar to blood banks.
The donor bone is taken from a source of human cadavers via a special ‘bone bank’ and is rigorously checked and sterilised before grafting takes place. Your body then assimilates this donor bone into your natural bone (of your jaw).
This is a second option: The difference between this and the other procedures is that the donated bone is harvested from animals rather than a human donor.
Bovine (cow) is the preferred form of animal bone for this graft. You may feel uncomfortable about this and worry about the safety aspects but this undergoes a system of rigorous testing beforehand. This is to ensure that it is sterile and compatible with your anatomy and bone composition.
This grafted bone acts as a 'stand in' which your body will replace with natural bone over time. This formation of new bone is called ‘Osteoinduction’ which uses a special protein called Bone Morphogenic Protein (BMP) to initiate this response.
This is the third technique in the bone grating series. This differs from the other three in that it is a man made graft rather than natural bone.
This graft is a synthetic version, made of calcium phosphate which looks almost identical to natural bone. There are two types of alloplastic grafts:
A resorbable graft means that it will be replaced by natural bone by your body. This doesn’t happen with the non-resorbable type of graft, but it can still be used to form a structure to hold the implants. This formation of a structure or ‘scaffold’ applies in both cases.
This involves the removal or ‘harvesting’ of bone from a designated donor site such as your hip. The hip is the preferred source as this is rich in marrow, which means a ready supply of bone cells. This bone is then grafted into the jawbone. Although this is the most successful of all the grafting techniques, it is only carried in cases of very severe bone loss due to its complexity and the requirement for further surgery.
Bone grafting is a very successful procedure, although like all procedures there is a tiny risk of rejection. We cannot be 100% certain as to why this happens although we can highlight contributing factors such as smoking and certain medical conditions, which can predispose the patient to this risk.
Bone graft failure can happen as a result of an infection or as a result of the grafted bone becoming loose and refusing to stabilise in the jaw.
If you experience bone graft failure then you will have to undergo removal of the rejected graft followed a period of healing before a second graft can take place.
There are other techniques available, which can help with bone loss such as a sinus lift or elevation, ridge expansion and distraction osteogenesis.
When a bone graft is placed and healing begins, a 'competition' starts between three groups of cells - connective tissue cells, epithelial cells and existing bone cells. They fight amongst themselves to fill in the area where there is bone loss and where the graft has been placed.
The bone cells are usually the losers, but a barrier membrane is a thin strip of collagen, which prevents the connective and epithelial tissue cells from entering the graft, and this allows the bone cells to ‘win’ and so regenerate.
What is a barrier membrane made of?
There are two types of barrier membrane: restorable and non-resorbable. The first barrier membranes were the non-resorbable sort and were used for some time before the development of the resorbable type. We typically use resorbable collagen membranes during our bone grafting procedures.
Are there any disadvantages?
Bone grafting is a highly successful and predictable technique which allows us to place an implant where we otherwise could not. If you have needed a large amount of bone grafted, then this may increase your total treatment time.