Bone grafting is a surgical procedure that replaces missing bone in order to repair bone fractures that are extremely complex or to increase the amount of bone in a particular site for various reasons.
In dental implantology, bone grafting is necessary when there is a lack of bone. For an implant to osseointegrate, it needs to be surrounded by a healthy quantity of bone.
a dental implant has to be surrounded
by healthy bone tissue
While there are always new implant types and techniques to allow compromise, a general treatment goal is to have a minimum of 10 mm in bone height, and 6 mm in width.
Bone loss causes
The bone is lost true a biological process called bone resorption. There are many reasons that can cause an excessive bone loss :
Long-term teeth loss
When natural teeth are lost, the sites that remain after the extractions begin a remodelling process. Over time, the toothless areas will gradually lose height and width.
mandible bone recession after teeth loss
The bone resorption process occurs especially if the toothless areas remain unrestored. When a restoration is designed (especially if it is supported by dental implants), the amount of bone that is lost is significantly lower.
Periodontitis (or advanced periodontal disease) is a destructive disease involving a significant resorption of the alveolar bone tissue. If left untreated, it can lead to the loosening and subsequent loss of teeth.
progression of periodontal disease if left untreated
When teeth are lost through periodontal disease, the bone left behind has already lost significant height and width. An implant treatment in this circumstances is highly challenging.
Various bone diseases such as bone infections, osteoporosis, fractures, tumors, following surgical interventions, radiation therapy etc. can stimulate the process of bone resorption which results in a high amount of bone loss.
To achieve an adequate width and height of bone, various bone grafting techniques have been developed. Basically, the bone defects are filed with grafting materials which are then covered with a semi-permeable membrane.
During the healing phase, natural bone replaces the graft, forming a new bony base for the implant and adding volume to the bone. The process is called guided bone regeneration (GBR).
There are two types of grafting materials :
Autograft : natural bone harvested from large body sources : iliac crest, the back of the head or others
Allograft : artificial substances that replace human bone and stimulate the process of natural bone formation ; these include calcium sulfate and especially, hydroxyapatite.
Three common procedures involve bone graft : sinus lift (described in the previous chapter), lateral alveolar augmentation and vertical alveolar augmentation.
Lateral alveolar augmentation
Lateral alveolar augmentation is the increase in the width of a site. The procedure may be performed both at the upper and lower jawbones.
Whenever the bone width is insufficient, it is advisable to resort to these procedures, which are relatively simple, painless, and with an excellent prognosis.
Vertical alveolar augmentation
Vertical alveolar augmentation is the increase in the height of a site. The procedure is very important if the bone is insufficiently high ; dental implants placed in deficient bone have a high risk of failure.
Other, more complex procedures, also exist for larger bone defects ; these are performed under general anesthesia by the oral surgeon.
For example, the mobilization (or repositioning) of the inferior alveolar nerve (located inside the mandible) is indicated when the nerve has an abnormal position that does not allow proper placement of the implant fixtures.
The final decision about which bone grafting technique will be performed, is based on an assessment of the degree of vertical and horizontal bone loss that exists : mild, moderate or severe.
Last review and update: February 2019