When a tooth is extracted, the bone that supports is progressively reabsorbed in the subsequent months and years. As often happens, such extractions are associated with traumas or previous pathologies such as paradontitis and periapical odontogenic infections… in such cases the residual bone crest can diminish very much.
In the alveolar crests that have lost teeth, the bone volume is often insufficient and is one of the main restrictions to installing implants.
Over the past 30 years, techniques have been refined that allow the regeneration of lost tissue and also offer implant rehabilitation in these cases. Below we give a brief overview of the most used techniques today to restore bone deficiency. These procedures are currently supported by a wide range of scientific literature.
To date, there is no absolute recommended technique for all cases: the surgeon’s task is precisely to choose the most suitable technique for the individual case based on the many variables (anatomical conditions, aesthetic demands, parafunctions, cleaning capacity, systemic conditions etc…)
GBR (Guided Bone Regeneration)
Perhaps the most widely used today, GBR relies on the use of synthetic materials (artificial or derived from animal bone) that have the appearance of variable grain sand. This material is called particulate.
In some cases this sand of artificial bone is added to the patient’s bone, scraped with a thin instrument near the site. In other cases, a gel derived from the patient’s blood (PRP) is added to the particulate.
Both of these two patient derivatives, the grated bone and the blood gel, seem to promote bone maturation in the larger GBRs. In smaller grafts, nothing is generally added to the artificial particulate.
The granular compound is then applied to the area to be regenerated and covered with one or more membranes. The membranes (there are different types and materials) isolate the graft from the gum, which is sutured to cover it. This barrier effect of the membrane promotes the migration of blood vessels and cells from the underlying bone portion… and thus creates a “guided” healing of the bone.
Depending on the form of regeneration required, the graft can be stabilized with small grids (now drawn in 3D) or screws or foils that prevent its deformation in the following months.
The lift of the maxillary sinus or sinus lift is now a routine procedure recommended for upper rear quadrants. Here the paranasal sinus, a bone cavity located between the cheekbone, the nasal cavity and the palate, offers a space to place the graft after a delicate dissection of the membrane that covers it. Access to the maxillary sinus can be different depending on the amount of bone to be regenerated. In most cases, implant screws are inserted simultaneously. However, the surgery does not change the external anatomy of the crest, since the increase is intrasinusal
Autologous bone graft
This graft involves the use of one or more bone blocks from the patient (autologous bone graft) collected almost always from an intraoral site (usually the area where the
lower wisdom teeth are located). The bone graft is then solidarized with small screws on the crest to be regenerated.
This technique is very effective especially in cases where it is necessary to increase vertically the bone ridge (from top to bottom or vice versa). The disadvantage is that you might need a second surgical site (donor site) in addition to the site you want to regenerate.
The increase with autologous block is often used for posterior mandible portions where a vertical bone regeneration is needed in an area just adjacent to the donor site. In such cases, the donor and grafting sites become a single surgical wound, thus reducing post-operative symptoms and their extent.
Osteodistraction or Split Crest
This technique allows to increase the width of the bone horizontally. This is done by separating the two faces of the crest, like pages in a book. The bone expanded this way heals like a single fracture and will be able to host one or more implants. Normally this technique is recommended on the anterior maxilla of relatively young patients, where the bone is softer and more deformable.
Important details about bone graft procedures
· With a good anesthesia and a light conscious sedation, the patient does not feel any pain during the operation.
· The post-operative pain is easily checked with a good pharmacological therapy
· The swelling instead is often inevitable and is gone within a week.
· An important variable for all techniques is time: the regenerated bone must “mature”, as well as the bony calluses of the fractures. The correct and complete reorganization of the bone allows it to support the high loads to which the implants are subjected. This time interval between bone regeneration and masticatory load can vary from 3 to 12 months. More information is available in the Bone Regeneration services section.