Dental Anatomy
The crown is the section of tooth normally exposed to the interior of the mouth; the section below the gingival line, buried in alveolar bone, is the root. The crown is covered with enamel, the hardest substance in the human body. Enamel is 96% to 97% inorganic. The root is covered with a softer substance known as cementum. Cementum resembles bone in that it is composed of 45% to 50% organic material. Beneath the enamel and cementum is a material known as dentin, which encloses the tooth’s sensory mechanisms, such as the dental pulp or nerve root. Dentin is 70% inorganic material, 18% organic material, and 12% water. Dentin is riddled with thousands of small channels known as dentinal tubules. Dentinal tubules contain odontoblastic processes (portions of the dentin-producing cells, also known as Tomes’ fibers), tissue fluids that bathe the processes and fill the tubules, and minerals.
Prevalence
A significant portion of the aged population is edentulous (lacking natural teeth). Prior to the advent of fluoridated water, it was expected that people would begin a pernicious process of tooth loss as they reached the age of 30. This loss usually accelerated during the patient’s thirties and forties until a full set of dentures was required to masticate food. Widescale fluoridation, which was first introduced in the baby boomer generation, dramatically reduced the incidence of edentulousness; thus people have kept their natural teeth for longer periods than before. However, cumulative damage from years of exposure to mechanical and environ- mental insults increases the incidence of problems peculiar to aged teeth. Recent reports place the prevalence of dentinal sensitivity at 40% to 45%, a figure that is certain to rise as the average age of the population increases.
