Teeth are designed to withstand significant, repetitive force, providing the durability needed for a lifetime of chewing. This strength is a complex combination of specialized biological materials working together. Understanding this dual composition, the measurable forces involved, and the daily threats to these structures reveals the true science behind dental durability.
The Physical Composition of Dental Strength
The tooth’s resilience is attributed to its unique, two-layered design. The outer layer, enamel, is the hardest substance in the human body, composed of approximately 96% mineral content. This mineral is hydroxyapatite, which is densely packed to create a shield against mechanical wear. This highly mineralized structure is rigid and provides the tooth’s primary defense.
Beneath this hard outer casing lies dentin, which forms the bulk of the tooth structure. Dentin is softer and less mineralized than enamel, giving it slight flexibility. This structural support acts as a cushion for the brittle enamel. The combination of the rigid enamel shell backed by the more elastic dentin layer prevents the tooth from fracturing under the high forces of chewing.
Quantifying the Hardness and Force Capacity of Teeth
Scientists use two distinct metrics to measure the mechanical properties of teeth: hardness and force capacity. Hardness refers to a material’s resistance to scratching or indentation, measured using the Mohs scale. Enamel ranks a 5 on the Mohs scale, placing its scratch resistance in a range comparable to steel.
The force capacity of the jaw is measured in Newtons or pounds per square inch (PSI). While the average force exerted during normal chewing is relatively low, the maximum voluntary bite force in an adult human averages around 162 PSI (about 720 Newtons). The total force a healthy tooth can structurally withstand is far greater than the average chewing load. This measurable strength confirms that teeth are built to manage high-pressure events, dependent on the integrity of the enamel-dentin complex.
Primary Factors That Compromise Tooth Structure
Despite their hardness, teeth are constantly threatened by two primary mechanisms of weakening: erosion and decay.
Erosion
Dental erosion is the chemical dissolution of the mineralized structure due to non-bacterial acids. This acid may come from dietary sources, such as sodas and citrus fruits, or from intrinsic sources like stomach acid due to gastric reflux. This process causes the irreversible loss of the surface layer of enamel through softening.
Decay
Dental decay, or caries, follows a different biological pathway involving bacteria. Specific bacteria in the mouth metabolize sugars from food and drink, producing organic acids as a byproduct. These acids lower the pH in the plaque biofilm, causing the demineralization of the enamel and dentin. Unlike erosion, decay creates a subsurface lesion that can eventually lead to the formation of a cavity.
Trauma, such as chipping a tooth or chronic grinding (bruxism), is a distinct mechanical threat that also compromises the structural integrity of the tooth.
Strategies for Maintaining Maximum Dental Strength
Maintaining the inherent strength of teeth requires both chemical support and modification of daily habits.
Chemical Support
The single most effective chemical strategy involves remineralization, which is the process of restoring lost minerals back into the enamel. Fluoride treatments and fluoridated products play a significant role by encouraging the formation of fluorapatite, a crystal structure that is stronger and more resistant to acid attack than the natural hydroxyapatite.
Physical Protection
The physical protection of the teeth is equally important for long-term strength. This includes modifying the intake of acidic foods and beverages to reduce the frequency of demineralization events. Proper brushing technique is also necessary to prevent mechanical damage, as aggressive brushing can lead to abrasion and the loss of enamel. Simple actions like avoiding habits such as chewing on ice or using teeth to open packages reduce the risk of micro-fractures and structural failure.