Alveolar Ridge Resorption: Alveolar bone resorption is a normal physiologic response following teeth extraction. The causes of alveolar bone volume loss can occur before dental extraction due to periodontal disease, periapical pathology and trauma to the teeth and bone. (SchroppL et al.2003) (1, 2). Additionally, the traumatic removal of teeth can cause bone loss and must be prevented (1,3). Finally, the alveolar bone suffers atrophy after tooth extraction, which has been well documented (1, 4, 5). The bundle bone at the site obviously will lose its function and disappear (Botticelli et al. 2004, Arau ´jo&Lindhe 2005, Arau ´jo et al. 2008)(10,16).Thus, the healing process of post-extraction sites, including contour alterations caused by bone resorption and remodelling is essential for obtaining functional and esthetically satisfactory prosthetic reconstructions.(1,3) The resorption and remodeling of the alveolar ridge after tooth removal is a natural healing phenomenon, which is physiologically undesirable and possibly inevitable and can negatively impact implant placement. (6,7) Mercier et al, 1988(13) has reported that the residual ridge resorption is the result of both Dissuse atrophy and a Pressure-resorption phenomenon. Disuse atrophy serves to remodel a structure, the alveolar bone that has no primary reason to exist after the loss of teeth. The process is limited to the contouring of the alveolar bone surfaces, as pointed out by the common observation that people who have lost their teeth but have never worn dentures do not suffer from severe atrophy. On the other hand, the pressure-resorption phenomenon is an active process guided by the laws of bone dynamics. It is caused by denture wear. Patterns of resorption in the maxilla differ from those in the mandible.
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Maxillary ridges resorb usually more evenly than the mandibular ones because of larger denture-bearing areas, with the palate providing a more equal distribution of mechanical forces. Due to excessive forces originating from natural mandibular incisors and inadequate posterior prosthetic support, the anterior maxillary bone disappears at a faster rate than the posterior part(12), Where a prominent root position is generally accompanied by an extremely fine and fragile vestibular wall that can be damaged during tooth extraction (2,8,9). Swenson(19) stated that after tooth extraction the alveolar process of the maxillae resorbs upward and inward to become progressively smaller because the direction and inclination of the roots of the teeth. Consequently, the older the edentulous maxillae, the smaller is the potential tooth-bearing area. The greatest amount of bone loss is in the horizontal dimension and mainly on the facial aspect of the ridge. There is also loss of vertical ridge height, which has been described to be most pronounced on the buccal aspect (8, 10). This resoprtion process results in a narrower and shorter ridge and the effect of this resorptive pattern is the relocation of the ridge to a more palatal/lingual position (11). In a clinical study by Schropp et al. 2003(1), the resulting dimensional changes have been evaluated by volumetric analysis, The loss of bone volume in the horizontal dimension amounts 5–7mm within the first 10 months. This corresponds with approximately 50% of the original width of the alveolar bone. An apico-coronal height reduction of 1mm accompanies the horizontal change. Multiple adjacent extraction sites demonstrate greater apicocoronal alterations compared with single extraction
Maxillary ridges resorb usually more evenly than the mandibular ones because of larger denture-bearing areas, with the palate providing a more equal distribution of mechanical forces. Due to excessive forces originating from natural mandibular incisors and inadequate posterior prosthetic support, the anterior maxillary bone disappears at a faster rate than the posterior part(12), Where a prominent root position is generally accompanied by an extremely fine and fragile vestibular wall that can be damaged during tooth extraction (2,8,9). Swenson(19) stated that after tooth extraction the alveolar process of the maxillae resorbs upward and inward to become progressively smaller because the direction and inclination of the roots of the teeth. Consequently, the older the edentulous maxillae, the smaller is the potential tooth-bearing area. The greatest amount of bone loss is in the horizontal dimension and mainly on the facial aspect of the ridge. There is also loss of vertical ridge height, which has been described to be most pronounced on the buccal aspect (8, 10). This resoprtion process results in a narrower and shorter ridge and the effect of this resorptive pattern is the relocation of the ridge to a more palatal/lingual position (11). In a clinical study by Schropp et al. 2003(1), the resulting dimensional changes have been evaluated by volumetric analysis, The loss of bone volume in the horizontal dimension amounts 5–7mm within the first 10 months. This corresponds with approximately 50% of the original width of the alveolar bone. An apico-coronal height reduction of 1mm accompanies the horizontal change. Multiple adjacent extraction sites demonstrate greater apicocoronal alterations compared with single extraction