Methods of reconstructing alveolar ridges prior to implant placement

Methods of reconstructing alveolar ridges prior to implant placement
August 2003
By Alan Herford, DDS, MD
Journal of Oral and Maxillofacial Surgery, Supplement 1 Зѓў Volume 61 Зѓў Number 8 Зѓў p102 to p102
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Abstract
Common causes of alveolar defects include bone resorption due to loss of teeth, infection, trauma, or congenital origin. There may be insufficient height or width of residual bone to permit the placement of dental implants and bone grafting may be required prior to implant placement.
Various bone grafting techniques are available for reconstruction of small alveolar deficiencies to more complex, extensive bony defects. Without grafting, the implants may have to be placed in anatomically unfavorable positions or have adverse angulations. These position/angulation compromises can lead to aesthetic dissatisfaction, mechanical overload, and possibly, implant loss.
There are minimum dimensions that the remaining alveolar process must possess for implants to be placed. When these dimensions are not present, it will be necessary to augment the size of the ridge prior to implant placement via a grafting procedure, or place implants so they are not completely contained within bone and place a semipermeable membrane over the bone and exposed part of the implant so as to permit bone growth to occur over the exposed area.
Alveolar defects can be restored by autologous grafting techniques including corticocancellous blocks, compressed particulate cancellous bone and marrow, and cortical grafts. All 3 of these types of grafts can be obtained from the mandible, maxilla, tibia and iliac crest, and cranium. Bone obtained from these sites varies in volume, hardness, and contour characteristics.
Either local or distant sites may be considered for donor sites. An advantage of local grafts includes the proximity of the donor and recipient sites and convenient surgical access. This proximity decreases the operative and anesthesia time. General anesthesia is avoided and the procedure is associated with decreased costs and morbidity. Another advantage is that there is no visible external scar. A disadvantage is that there is less bone available than from extraoral sites.
Meticulous techniques and rigid fixation of block grafts are important to improve success rates. It is important with any alveolar defect to follow basic surgical principles. The mucoperiosteal flap should be designed to adequately expose the underlying ridge, maintain a broad base for vascular supply, and allow tension-free primary closure. Midcrestal incisions maximized the vascularity to the margins of the flaps.
The decision to graft is prosthetically driven. Aesthetic and functional compromise can be prevented by ridge augmentation procedures and enhanced emergence profiles of the implants can be obtained. The importance of primary stability cannot be overemphasized for long-term success. Autogenous bone grafts are recommended because of their osteogenic potential.