Bone physiology and metabolism in dental implantology: risk factors for osteoporosis and other metabolic bone diseases

Placing a dental implant elicits a time-dependent bone response controlled by wound-healing factors (cytokines, bioelectrical signals), biomechanics (gravitational, functional, and therapeutic loads), and mineral metabolism (hormones, diet, excretion). The osseous response to an implant involves four physiological stages: (1) endosteal and periosteal callus formation; (2) compaction and remodeling of the callus; (3) remodeling (turnover) of the nonvital interface and adjacent bone; and (4) maturation (secondary mineralization) of new bone. Long-term maintenance of a rigid implant interface is related to continual bone remodeling. Common metabolic bone disorders affecting potential implant patients are osteopenia ("osteoporosis"), renal osteodystrophy, osteomalacia, and Paget's disease. The most prevalent problem is a long-term negative calcium balance leading to a compromise in bone strength. Symptomatic osteoporosis (usually wrist, hip, and/or spine fractures) affects 4 to 50 percent of the population depending on age, race, sex, endocrine status, and life-style. Postmenopausal white and Asian females present the greatest risk. The jaws of "osteoporotic" adults are variably affected because of the moderating influence of mechanical function. Management of metabolic bone disorders is an important consideration in diagnosis, treatment planning, and long-term monitoring of dental implants. Bone metabolic counseling, a natural extension of preventative dentistry, is an unexpected benefit readily appreciated by patients and their families.