are columns of bone that surround and anchor the teeth and run the entire length, mesiodistally, of both the maxillary and mandibular dental arches. The alveolar bone is unique in that it exists for the sake of the teeth that it retains; when the teeth are absent, the bone slowly resorbs. The maxilla resorbs in a superioposterior direction, and the mandible resorbs in an inferioanterior direction, thus eventually converting an individual's occlusal scheme from a Class I to a Class III. Loss of teeth alters the form of the alveolar bone in 91% of cases. In addition to this resorption of bone in the vertical and anterioposterior dimensions, the alveolus also resorbs faciolingually, thus diminishing the width of the ridge. What initially began as a tall bell curve (in the faciolingual dimension) eventually becomes much shorter and broader. Resorption is exacerbated by pressure on the bone; thus, long-term complete denture wearers will experience more drastic reductions to their ridges than non-denture wearers. Those individuals who do wear dentures can decrease the amount of bone loss by retaining some tooth roots in the form of overdenture abutments or have implants placed. Note that the depiction above shows a very excessive change and that this many take many years of denture wear to achieve. Ridge resorption may also alter the form of the ridges to less predictable shapes, such as bulbous ridges with undercuts or even sharp, thin, knife-edged ridges, depending on the many possible factors that influenced the resorption. Bone loss with missing teeth, partials and complete dentures is progressive. According to Wolff's law, bone is stimulated, strengthened and continually renewed directly by a tooth or an implant. Teeth and implants provide this direct stimulation which develops stronger bone around them. A 1970 research study of 1012 patients by Jozewicz showed denture wearers had a significantly higher rate of bone loss. Tallgren's 25-year study in 1972 also showed denture wearers have continued bone loss over the years. The biting force on the gum tissue irritates the bone and it melts away with a decrease in volume and density. Carlsson's 1967 study showed a dramatic bone loss during the first year after a tooth extraction which continues over the years, even without a denture or partial on it. The longer people are missing teeth, wear dentures or partials, the less bone they have in their jaws. This may result in decreased ability