With the increase in the use of dental implants for restoration of missing teeth, more emphasis is being placed on restorations of the alveolar ridge to ensure the optimal implant placement and prosthetic (crown) treatment outcomes. Different teeth have different root diameters and, ideally, they should be replaced with an implant similar in size.
However, after tooth extraction the shrinkage of horizontal dimension of jawbone is often a problem and results in deficiencies that complicate the ideal implant placement. In some cases, the jaw resorption is so advanced that dental implant cannot be placed.
In the past, surgeons would place the implant wherever they saw sufficient amount of bone in the jaw regardless the position of the final crown. The modern concept of implant therapy is based on the final position of the prosthesis. A prerequisite for the successful placement of dental implants in the ideal, prosthetic driven position is a minimum amount of bone volume (width and height) of the edentulous area that will provide a functional and esthetic implant restoration.
Lack of bone in the ideal position requires techniques that predictably regenerate bone that resorbed. These techniques include augmentation of the horizontal dimension of the ridge. This procedure is called Guided Bone Regeneration (GBR).
Typically, augmentation of bone volume is accomplished through various methods including use of particulate (grain appearance) and block bone grafting materials, split ridge technique (expansion of the jaw bone) and with the use of growth and differentiation factors. Horizontal ridge augmentation is employed to recreate the missing bone. GBR is a surgical procedure that utilizes barrier membranes to protect the grafting bone material placed on the deficient areas to augment. These devices can derive from animals (collagen products) or from polymers. The main difference between the two is the spontaneous degradation of the natural one (collagen) and the persistency of the synthetic one. Each material has its own use depending on the technique and the expected outcome.
The grafting material can have human, animal or synthetic origin. As for the membranes, each material has its own indications for use.
The GBR technique is used in two clinical scenarios: simultaneous or staged approach. In case of severe atrophy of the jawbone, the surgeons prefers to augment bone first and after a period of healing place the dental implants. In less severe cases, the augmentation can be applied at the same time of implant placement.
The diagnostic tools to determine whether a case is eligible for this particular technique are based on a radiographic bi- and three-dimensional radiographic investigation. The medical history and the periodontal status of the patients need to be controlled in order to decrease to the minimum the potential complication. Controlled systemic disease, absence of smoking habits, diligent oral hygiene and frequent dental control are basic steps that need to be respected as much as possible.
Fig. 1 a and b. Regeneration of missing bone width in the anterior maxillary jawbone. Before (a) and after treatment (b).
Fig. 2 a and b. Reconstruction of horizontal width of partially edentulous resorbed mandibular jawbone (a). The bone grafting procedure helped to place three dental implants (b).
Lorenzo Mordini DDS, MS