Assessment Of Poly Tetra Fluro Ethylene Membrane Versus Native Collagen Membrane With Guided Bone Regeneration In Atrophic Anterior Maxilla Using (1:1) Of Autogenous Bone And Xenograft Mixture (Randomized Clinical Trial)

The alveolar bone is formed during tooth eruption, and consists of maxillary and mandibular components that shape and support the alveolar sockets. When teeth are lost, alveolar atrophy occurs, ultimately resulting in a short and narrow alveolar ridge . Such changes in the alveolar bone have a significant effect on prosthetic restoration planning, and are particularly important for areas with esthetic requirements, such as the maxillary incisors. Since preservation of the alveolar bone after extraction makes implant placement and prosthetic restoration easier in the edentulous jaw, alveolar ridge preservation and reconstruction methods using various bone graft materials together with resorbable and non-resorbable membranes have been introduced in order to minimize the loss of alveolar bone after extraction.

Investigations of changes in the alveolar bone after extraction have frequently been performed through clinical measurements and radiographic analysis. In particular, after the extraction of a tooth with fracture or severe periodontitis, the alveolar bone shows severe horizontal and vertical atrophy. The reduction in the width of the alveolar ridge is more notable in the horizontal direction than in the vertical direction, and the buccal wall of the alveolar bone has been reported to undergo greater vertical atrophy than the lingual wall. Changes in the width of the alveolar ridge after extraction occur in a relatively short time, decreasing most rapidly within the first six months after extraction, followed by continual, slow bone resorption over the course of the rest of the patient's life .

When a tooth has been lost, the extent of alveolar bone resorption is affected by a range of factors, including the number of extracted teeth and bone walls, the bone density, the extent of alveolar bone loss, infection, and the presence or absence of adjacent teeth.

Dental implant has become a predictable treatment option, with excellent long-term results. However, the success of implant therapy depends on the amount of bone volume at the insertion site.Unfavorable local conditions may provide insufficient bone volume that negatively affects the prognosis of dental implants. Cawood and Howell in 1988 ranked the atrophy degree of edentulous jaws in six classes. Particularly, atrophies within class IV, also known as "knife-edge" ridges, present a serious horizontal defect, making challenging the placement of regular implants.

Many techniques have been developed to regenerate atrophic alveolar jaws for the placement of dental implants, performed either in combination with graft procedures or in second stage surgery after a period of healing. For many years, bone blocks represented the gold standard to reconstruct the alveolar ridge bone defects. This technique requires to harvest a wide amount of bone to rebuild the atrophic crest.(20). For this reason, bone blocks were often harvested from extra-oral sites with an higher morbidity. Moreover some problems can occur when a combined defects (horizontal and vertical) need to be treated. Guided bone regeneration (GBR) has been proposed as a possible alternative for patients with severe horizontal bone atrophy, to overcome the drawback of bone blocks techniques. To protect and prevent the invasion of the clot by nonosteogenic cells, maintaining an adequate biological space for the regeneration of bone tissue, the use of both non-resorbable or resorbable membranes, in combination with autologous or heterologous particulate bone have been proposed. Particulated autogenous bone can be mixed with bone substitutes to add more osteogenic factors.