Objective Osteoporosis-related fractures are a significant health issue in aging societies, necessitating effective screening and prevention strategies. While panoramic radiographs are widely used for osteoporosis screening via mandibular cortical bone morphology, there is insufficient consensus on the quantitative analysis of alveolar bone mineral density (al-BMD) using intraoral radiographs. This study aimed to measure al-BMD in young adults and investigate its relationship with general skeletal bone mineral density (gs-BMD) at the lumbar spine (LSBMD) and femoral neck (FNBMD). Additionally, the influence of biological factors, such as body weight and height, on BMD was assessed. Methodology A total of 53 young adults (34 males, 19 females, mean age: 26.0 years) participated in this study. Intraoral radiographs with calcium carbonate reference standards quantified al-BMD at three mandibular premolar regions. gs-BMD was measured using dual-energy X-ray absorptiometry (DXA). Correlations among al-BMD, gs-BMD, and biological factors were analyzed. Results Results showed no significant differences between age, sex, body height, body weight, al-BMD, and gs-BMD. Age was correlated with FNBMD but not al-BMD as well as LSBMD. Body weight positively correlated with LSBMD (r = 0.437, P = 0.001) but negatively with FNBMD (r = -0.412, P = 0.002). No significant correlations were observed between al-BMD and gs-BMD or biological factors. Conclusion These findings suggest that al-BMD may not necessarily reflect gs-BMD changes and is strongly influenced by local factors in the oral cavity. This highlights the importance of evaluating al-BMD independently of gs-BMD. Future studies with larger sample sizes and additional factors influencing al-BMD are needed to validate these results.