Bone Grafting Materials
Bone Grafts
The process of grafting in the dental implant field is usually to increase or alter the volume (height, width) and sometimes shape of available bone to place implants into. Teeth support bone and gum around them. When teeth are lost the bone surrounding the roots resorbs (melts away) as it is no longer required to support the teeth and a deficiency may result according to the use it or lose it principle. Often this can be managed without any grafting/ augmentation techniques but sometimes these are necessary. The deficiency increases if trauma was involved with the tooth loss, as time passes and if dentures are worn. Some people have a greater tendency to lose bone including smokers. Bone grafts act as a scaffolding into which the patient’s own bone grows and the graft material is usually replaced by this bone.
There are different types of graft materials available and they are usually characterised by the source they are derived from. Correspondingly they have different properties and behaviour.
• Autogenous or Autografts
• Allografts
• Xenografts
• Alloplastic
Autogenous Bone
This is using the patient’s own bone and therefore is often referred to as the ‘gold standard’ in bone grafting. Bone may be taken from a number of sites (donor sites) in the mouth or from outside the mouth and placed at the desired site (receptor site). This process may involve taking of small amounts of bone from close to the implant site but when large amounts are necessary such as for a sinus graft then it may be necessary to harvest bone from the from outside the mouth and a common area is the hip.
Allograft Bone
The process is very similar to using your own bone but this bone is sourced from human cadaver bone supplied by a bone bank. Currently Dr Sheikh sources this material only from the Rocky Mountain Tissue Bank [LINK] in the USA which is a gold standard tissue bank and operates on a not for profit basis. This technique has the considerable advantage that no donor site surgery needs to be performed to harvest bone and offers a very useful alternative to autogenous bone grafting particularly where operations on the hip can be avoided. Bone banks have extremely strict procedures for accepting tissue, sterilising and treating it ready to be used in other patients.
Xenografts
This bone is sourced from animals usually cows.
The methodology for its use is then similar to the human bone mentioned elsewhere. Some patients have safety concerns about using bone from animals.
Alloplasts
These are synthetic materials meaning they are man made from materials not derived from animals or humans and have a similar structure to bone. The resorbable materials can be used instead of bone or in addition to it in the grafting techniques described elsewhere. This is then replaced by the patient’s own bone. Non resorbable materials are usually used as fillers to give bulk or shape to the bone or gums and stay in place for a long time or permanently.
Bone grafting is a very successful procedure although you do need to know that 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. These can predispose the patient to this risk.
Barrier Membranes Used in Dental Implantology
A barrier membrane is used in implant surgery usually to help protect bone or other grafting materials during healing.
The membranes are placed at the same time as the bone graft. As Soft tissues grow more quickly than others the membranes stops the soft tissues from penetrating into the bone while it heals. Membranes also facilitate the healing process of the grafted material. The increased amount of bone can then be available for implant placement. This technique is sometimes known as guided tissue regeneration.
Barrier membranes used currently are usually resorbable so no second surgery is required to remove them because the body removes them in a timeframe that allows the new bone to heal.
Current membranes are derived from animal collagen or are made of synthetic polymers. As would be expected different membranes have different resorption times and properties and suitable ones are chosen for the type of procedures being planned.
Surgical Plates and Screws Used in Dental Implant Procedures
Plates and screws as in other forms of orthopaedic surgery can be used in dental implant surgery.
They are used to stabilise sections of the jaw and or bone grafts to allow healing of the bone as bone needs to be immobilised during the healing phase. These devices are often used in conjunction with bone graft materials and barrier membranes.
