Tap water is a complex blend of compounds, minerals, and additives, meaning its effect on dental health is not simply good or bad. For most people served by municipal systems, the benefits of water treatment far outweigh any potential risks. However, the exact composition varies significantly by location based on the source, distribution infrastructure, and the plumbing within an individual home.
The Dental Superpower: Fluoridation
The primary reason tap water is beneficial is the controlled addition of fluoride, a process known as fluoridation. Fluoride works directly on the tooth surface to prevent the mineral loss that leads to decay. It actively promotes remineralization, a natural process where minerals are redeposited into the tooth enamel after acid attacks.
This mineral strengthens the crystalline structure of enamel, making it more resistant to future acid damage from oral bacteria. Water fluoridation provides a constant, low-level exposure to fluoride throughout the day, which is considered a topical benefit. The Centers for Disease Control and Prevention (CDC) recommends an optimal concentration level of 0.7 milligrams of fluoride per liter of water (0.7 mg/L).
When fluoride is ingested during the years of tooth formation, it is incorporated into the developing enamel, offering a systemic benefit. However, continuous topical contact of fluoridated water with the tooth surface is the dominant mechanism for cavity prevention in both children and adults. This public health measure has been shown to reduce tooth decay by about 25% in the population.
Potential Harmful Components and Contaminants
While municipal water treatment effectively removes most harmful agents, contaminants can still pose a threat to both oral and systemic health. These risks fall into two categories: those introduced at the source or treatment facility, and those picked up inside the distribution system or home. Source-related contaminants include pathogens, such as bacteria and viruses, which especially affect private well users or surface water systems following heavy rain or flooding.
The most significant dental and health risk often comes from the infrastructure transporting the water, particularly heavy metals. Lead, a known neurotoxin, leaches into the water primarily from old lead service lines and plumbing, especially in homes built before 1986. The corrosiveness of the water causes the lead to dissolve, and no level of lead is considered safe, despite the Environmental Protection Agency (EPA) action level of 15 parts per billion.
Copper is another metal that can leach from household pipes and fittings, causing a metallic or sour taste and blue-green staining in sinks. To understand the specific risks in your area, request an annual Consumer Confidence Report (CCR) from your local water utility. This report details the contaminants detected in your municipal supply and is the most practical way to assess your water quality.
The Role of pH and Acidity in Enamel Health
The acidity of water, measured by its pH level, plays a direct role in the potential for enamel erosion. The pH scale ranges from 0 (most acidic) to 14 (most alkaline), with 7 being neutral. Tooth enamel begins to demineralize when the surrounding liquid drops below a critical pH threshold of approximately 5.5.
Tap water can become acidic due to several natural and man-made factors before it reaches the home. Groundwater, for example, can absorb carbon dioxide from the soil, which forms carbonic acid and naturally lowers the pH. Additionally, water treatment facilities sometimes use chemicals like chlorine or aluminum sulfate, both of which can slightly decrease the water’s pH.
The danger of acidic water is often secondary, as low pH can make the water more corrosive, causing it to strip metals like lead and copper from pipes. While municipal systems aim to keep water pH between 6.5 and 8.5 to limit corrosion, a pH below 7 can still slowly erode plumbing. This process introduces harmful heavy metals into the water you drink.
Addressing Alternatives (Filtered and Bottled Water)
Many people turn to filtered or bottled water, believing these alternatives are safer or healthier for their teeth. Common pitcher filters that use activated carbon improve taste and remove chlorine, but they are incapable of removing beneficial fluoride. More robust systems, such as reverse osmosis (RO) or distillation, are highly effective at removing almost everything, including heavy metals and pathogens.
However, these advanced filtration methods also strip out the cavity-preventing fluoride, eliminating the primary dental benefit of tap water. Those who use RO or distillation may need to rely on other sources, like fluoridated toothpaste, or consult their dentist about supplements.
Bottled water presents a different set of concerns for oral health. The majority of bottled waters contain suboptimal levels of fluoride, offering little to no dental protection. Furthermore, the pH of bottled water is highly variable, with many popular brands testing in the acidic range due to added minerals or disinfection processes. Unless a verifiable contamination issue exists in the tap supply, switching may negate the protective effects of fluoridation and expose teeth to an acidic environment.