Dimensional Changes Following Ridge Augmentation of the Buccal Wall in Dehiscence Sockets: a Randomized-controlled Clinical Trial.

1. Introduction:

The alveolar process is tooth dependent and once a single tooth is extracted, the architecture of the socket undergoes dimensional changes hindering the prosthetic rehabilitation at the edentulous crest which demands a posterior guided bone regeneration (GBR). Studies in dogs described the main changes happened after tooth extraction (1,2); the blood forms a clot at the wound site which is replaced by a connective tissue matrix: after 1 month the woven bone fills the extraction socket; subsequently the woven bone undergoes osteoclastic resorption which leads to a maturation of the recently formed bone, gradually replaced with lamellar and bone marrow. Such events were clinically evaluated in several studies with an average of loss in width (3.5-4mm) (3). Bone resorption in height is correlated to the plate thickness; thin-wall phenotypes (<1mm) have a median vertical bone loss of 7.5mm in the central risk zone (4). Moreover, at the aesthetic zone, this narrow crest makes more difficult the adequate implant placement (5), then functional and esthetic complications can be expected.

The fresh socket in the esthetic zone represents a challenge for the clinician and immediate implant placement (type I) is associated with a high risk of mucosal

recessions. Moreover, the absence of the buccal plate increases the risk (6). Early implant placement (type II) described by Buser et al. (7) reported long term excellent esthetic results and this technique is compatible with alveolar ridge preservation.

Alveolar ridge preservation is a widely used technique immediately after tooth extraction to minimize the alveolar resorption, to accelerate the bone formation and to improve the prosthetic restoration with an implant placed on a tridimensional way. Different biomaterials were used: autografts (8), allografts (9), xenografts (10,11), alloplasts (11,12) with or without barrier membranes. In all of them, less bone resorption was drawn with respect to natural healing; however, such techniques do not prevent physiologic bone resorption but limit it, improving the expected results in absence of preservation (13). Comparing the healing time with different biomaterials, mineralized bone allograft demonstrated similar results in the amount of new bone growth at 3 and 6 months after extraction (14) allowing the reentry before.