Jaw bone augmentation (synonym: jawbone augmentation) is the surgical reconstruction of lost bone substance in the upper or lower jaw. Augmentation procedures are used to securely anchor implants (artificial tooth roots) in the bone, to enable prosthetic restorations with fixed or removable dentures, or to restore esthetics after bone loss due to an accident or disease. Bone loss of up to 60% can occur even in the first few years after tooth extraction (tooth removal). The width of the alveolar ridge is reduced to up to 2 mm. Since an implant must be surrounded by at least 1.5 mm of bone on all sides, augmentation of the affected jaw area may be required prior to implant placement (the placement of an implant). In addition to bone loss after extractions, years of wearing removable dentures leads to alveolar ridge atrophy (recession of the portion of the jawbone that formerly supported teeth) to a greater or lesser degree due to the transfer of chewing pressure to the alveolar ridge.
Bone grafting materials
I. Alloplastic bone graft substitute (KEM).
Synthetically (artificially) manufactured materials of calcium carbonate, tricalcium phosphate, hydroxyapatite, or bioglass, which are biocompatible (biologically well tolerated), can be used to build bone. Osteoblasts (bone-forming cells) colonize the synthetic surfaces, and the material can be degraded by the body within several months to years, being replaced by the patient’s own bone. II. Autogenous bone graft
If augmentation is to be performed using autogenous (autologous, the patient’s own) bone, this must first be removed from the patient at a suitable site. III. bone chips
The third option is the use of biotechnologically produced bone (bone chips). IV. Allogenic bone
Allogenic bone is derived from the long tubular bones of human multi-organ donors. The DFDBA (Demineralized Freeze Dried Bone Allograft) process significantly reduces (but does not completely eliminate) the risk of pathogen transmission and immunological reactions. V. Xenogenic bone
Xenogenic substitute materials (Bio-Oss) are of bovine origin (from cattle). Deproteinization (removal of protein) takes place to reduce the risk of transmission and allergy. What remains is the inorganic bone portion into which new bone sprouts.
Indications (areas of application)
The indications, which are adapted to the individual situation and oriented to the therapeutic goal, are discussed separately in the respective procedure.
The surgical procedures
- Horizontal or vertical augmentation using bone block.
- Bone splitting (alveolar process splitting).
- Bone-spreading (alveolar process spreading).
- Distraction osteogenesis (spreading of the bone).
- Socket preservation technique
- Internal/external sinus lift (sinus floor elevation).
I. Horizontal or vertical augmentation using bone block
Augmentation using bone block is used when the jaw has already atrophied (receded) to such an extent that the residual bone width and/or height is too small for implant placement (insertion of an implant). Autogenous (body’s own), allogenous or synthetic bone can be used for this purpose. The most common harvest sites for autogenous bone blocks are:
- Ascending mandibular branch or mandibular angle region.
- Chin
- Pelvic crest
After detaching the mucosa covering the alveolar ridge, the harvested bone block is adapted to the ridge line and fixed to it using small titanium nails or screws. Any remaining gaps between the bone graft and the jawbone can then be filled with bone substitute material or the patient’s own bone chips, usually in combination with the patient’s own blood. After the bone graft has healed, implant placement can take place.
Indications (areas of application)
- Horizontal and vertical jawbone augmentation when the alveolar ridge width or height is too small.
II. bone splitting (alveolar process splitting)
After anesthetizing (numbing) the surgical area, the mucosa is detached to provide access to the alveolar ridge.The exposed bone is split in the middle by thin instruments – for example, diamond cut-off wheels. A bone chisel is then used to gently move the two bone parts apart in such a way that a fracture (bone break) of the narrow lamellae is avoided. Depending on the course of the procedure, the surgeon decides whether implant placement can take place simultaneously (at the same time) as bone splitting or not. If implant placement is possible, the implants are placed immediately afterwards. The resulting cavities are filled with bone substitute material in combination with autologous blood. In Guided Bone Regeneration (GBR), the augmented bone is covered with membranes – usually resorbable (dissolvable) – and the mucosa is sealed saliva-tight. In the two-stage procedure, which is used far more frequently, the implants are placed only after regeneration (reconstruction) of the bone in a second operation. In this case, the covering by means of a membrane can be omitted. The entire cavity created by bone splitting is supplied with bone substitute material, and the mucosa is sutured in a saliva-proof manner. After healing of the material, implant placement takes place a few months later.
Indications (areas of application)
- Ridge width from 2.5 to 3 mm
- Jaw comb height of 1 cm
- Bone density D2 – D4
III Bone spreading (alveolar process spreading)
After loosening a mucosal flap, the bone in the area of the planned implant location is prepared with drills of ascending diameter in a displacing manner, so that on the one hand an implant site is created, and on the other hand the remaining bone is spared as much as possible. By gradually increasing the diameter, the bone is slowly displaced.
Indications (areas of application)
- Ridge width of 4 to 6 mm – Bone spreading requires a greater residual bone width than bone splitting.
- Ridge height from 6 to 10 mm.
- Bone density D2 – D5
- In the maxillary posterior region, often in conjunction with a sinus lift (augmentation of the maxillary sinus floor, sinus floor elevation).
IV. Distraction osteogenesis
The procedure of distraction osteogenesis (new bone formation by pulling apart) was originally developed by the physician Ilizarow for limb lengthening (lengthening of arm and leg bones). In this process, an artificially created fracture gap is continuously rotated apart by means of a distractor (a screw). Bone healing takes place between the bone pieces by forming new tissue. For augmentation, the area of the jaw where more bone substance is needed is surgically prepared under anesthesia. The bone is cut through, thus creating a fracture gap (fracture gap). The distractor is then attached to the bone pieces in such a way that it can gradually distract (widen) the fracture gap. The distractor is adjusted using a screw located above the mucosa. The fracture gap is widened one millimeter per day. If less is distracted, the risk of premature ossification increases. If more is distracted, pseudarthrosis may develop. Ossification of the fracture gap takes about two to three months. After completion of the treatment, the distractor is removed in a second procedure, and the implants can be placed. Implant placement can be performed either simultaneously or in two phases at a further treatment appointment. This method offers the advantage of bypassing the insertion of autologous or foreign bone or bone graft substitutes and the associated risks.
Indications (areas of application)
- Correction of bone growth disorders
- For alveolar chamber elevation prior to implant placement.
V. Socket preservation technique
The socket preservation technique (technique for “preservation of the socket”; synonym: ridge preservation technique: “preservation of the alveolar ridge”) prevents the bone resorption that would otherwise inevitably occur after an extraction (tooth removal).Immediately after extraction, the empty alveolus (bony tooth socket) is filled with bone substitute or autologous bone material that is difficult to resorb, and this and the surrounding bone margins are covered with a membrane – usually resorbable – that is fixed between the mucoperiosteal flap (mucosa-bone flap) and the bone margin. The wound is then sutured in a saliva-proof manner. This may require harvesting and transfer of a mucosal connective tissue graft from the palate. Non-absorbable membranes must be removed in a second procedure after about ten days. In this way, collapse of the alveolus in the course of wound healing and the associated significant loss of bone are avoided. After a healing period of about three to five months, an implant can be placed in the augmented area.
Indications (areas of application)
- To prevent alveolar ridge atrophy after extraction.
VI Sinus lift
After extractions of maxillary posterior teeth and subsequent years of wearing dentures that transmit chewing pressure to the remaining alveolar ridge, the bony separating layer between the oral and maxillary sinuses may be so atrophied (degenerated) that stable implant placement has become impossible. In this case, a so-called sinus floor elevation, a bone elevation in the area of the maxillary sinus floor, must be performed first. Sinus elevation is covered in a separate article.
