The aim of this series of studies was to investigate the relationship between skeletal bone mineral density (BMD) and mandibular alveolar bone mass (MABM), structure, and thickness, as well as to evaluate the possible effect of local functional factors on MABM and alveolar thickness. A further aim was to elucidate whether longitudinal changes in mandibular radiographic characteristics and the bucco-lingual dimension of the alveolar process were related to alterations of BMD. BMD was measured in 160 dentate women using dual X-ray absorptiometry of the forearm. On periapical radiographs MABM was estimated using densitometry and the grey-level value. The alveolar bone structure was evaluated with a visual index and by examining the bone texture on periapical radiographs. The thickness of the masseter was assessed with ultrasound imaging to estimate the masticatory functional factor, and the bucco-lingual alveolar thickness was measured on casts.MABM and alveolar structure were significantly correlated to BMD. The best correlation was found between BMD and trabecular pattern evaluated with the visual index (r=0.62, p<0.001). The alveolar thickness was correlated to BMD, and to masseter thickness. MABM was influenced of age, the alveolar thickness, the number of occluding teeth, and the masseter muscle thickness but these factors had no effect on the trabecular structure. After five years, all measurements except the ultrasound imaging of the masseter muscle were repeated in 136 women. The mean BMD, MABM, and alveolar thickness decreased significantly during this period, whereas no significant change was found in the bone structure. In posterior region, the alterations in alveolar bone thickness, radiographic grey-level value, and bone texture were significantly correlated to the changes in BMD. In the anterior region, the alterations in alveolar thickness were not correlated with the changes in BMD. Furthermore, no correlation was found between alterations in MABM, estimated by densitometry, and changes in BMD.In conclusion, a significant relationship exists between BMD and mandibular alveolar bone mass, structure, and thickness. The local functional factors mainly influence MABM and the alveolar thickness in the molar region, whereas BMD influences the trabecular structure. Dense trabeculation is a strong indicator of high BMD, whereas sparse trabeculation predicts low bone mass. In peri- and postmenopausal women the alveolar shape in the premolar region can be used to predict BMD level. In the lower premolar region, the longitudinal alterations in BMD are related to longitudinal changes in grey-level value, bone texture and alveolar thickness. The decrease in bucco-lingual alveolar thickness may be due to periosteal resorption related to skeletal bone loss
