| The minimization of morbidity in cranio-maxillofacial osseous reconstruction: Bone graft harvesting and coral-derived granules as a bone graft substitute | ||
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Alveolar bone is that specialized part of the cranio-maxillofacial skeleton that forms the primary support for the teeth. Alveolar bone is composed of bundles of bone which is built up in layers in a parallel orientation to the coronal-apical direction of the tooth. The anterior maxillary bone is less dense than mandibular bone but more dense than maxillary posterior bone (Truhler et al. 1997).
Alveolar ridge defects and deformities can be the result of congenital maldevelopment, trauma, periodontal disease or surgical ablation, as in the case of tumor surgery. Resorption after tooth-loss has been shown to follow a predictable pattern: the labial aspect of the alveolar crest is the principal site of resorption, which first reduces first in width and later in height (Atwood 1971, Tallgren 1972, Cawood & Howell 1988).
Alveolar bone is resorbed after tooth extraction or avulsion most rapidly during the first years. Non-traumatic loss of anterior maxillary teeth is followed by a progressive loss of bone mainly from the labial side (Lam 1960, Atwood 1973, Cawood & Howell 1988). The magnitude of bone loss is estimated to be 40–60 % during the first 3 years following tooth-loss and then decreases to 0.25–0.5 % annual loss thereafter (Ashman & Rosenlicht 1993, Ashman 2000). In the deciduous paediatric dentition, loss of a retained second deciduous molar, which has no succedaneous permanent tooth to replace it, is also associated with bone loss. The rates of bone loss at these sites have manifested as alveolar ridge width decreases of 25% within 3 years after extraction of the retained primary molars, and this continues to diminish by a further 4% over the next 3 years (Ostler & Kokich 1994). The cause for resorption of alveolar bone after tooth-loss has been assumed to be due to disuse atrophy, decreased blood supply, localized inflammation or unfavorable prosthesis pressure (MacKay et al. 1979, Ashman 2000).
One strategy to deal with alveolar bone loss without resorting to a bone graft is to prevent its occurrence. A number of methods have been tried including the retention of tooth roots to help maintain the alveolus. These retained tooth roots can be used as abutments for overdentures for example and are effective at halting the process of alveolar ridge resorption (Shykoff et al. 1978). Malmgren et al. have introduced a method in which the alveolar ridge is preserved by removing the crown and filling the root of an ankylosed and infrapositioned tooth. The decoronated root is left in situ for slow resorption (Malmgren et al. 1984, Filippi et al. 2001). Other treatment alternatives to preserve alveolar bone without the use of bone grafts include autotransplantation of teeth (Clokie et al. 2001) and orthodontic space closure (Ostler & Kokich 1994). Simply adding a bone graft to alveolar bone and allowing it to function by loading it with a dental prosthesis will also lead to further resorption of alveolar bone (de Koomen, 1982). The placement of dental implants into alveolar bone or grafted alveolar bone has also been shown to prevent further alveolar resorption (Zarb & Schmitt 1993, Zarb & Schmitt 1996, Satow et al. 1997, Stoelinga et al. 2000, Marx et al. 2002). However the timing of dental implant treatment is most important. Dental implant placement in young growing patients is contraindicated because of the interference with alveolar growth in such patients (Kurol & Ödman 1996). However, dental implants can be placed in young patients once growth has ceased (Kurol & Ödman 1996).