Fluoride delivered through drinking water at a low, steady level provides ongoing topical exposure to the teeth. When the water is fluoridated at about 0.7–1 mg/L, fluoride is ingested throughout the day as you drink, creating a nearly continuous supply of fluoride in the mouth. This steady presence supports remineralization and helps reduce caries risk without the high, intermittent doses that come with other products. Fluoride toothpaste delivers much higher concentrations but only during a short brushing window, so its topical effect is strong but not continuous. Fluoride mouthrinse adds another regular source, but still requires deliberate use and isn’t as constant as daily water consumption. Bottled water often has little to no fluoride and can vary greatly, so it doesn’t reliably provide the low-dose, around-the-clock exposure desired. Therefore, fluoridated water is the method that best achieves this low-dose, nearly continuous topical exposure via water.

DMFT measures caries experience in the permanent dentition by counting teeth that are decayed, missing due to caries, or filled. The average is calculated across a population, so it reflects, on average, how many teeth per child have been affected. For school-age children aged 5–17, the commonly cited mean DMFT is about 1.97, meaning that, on average, each child has roughly two teeth that have been affected by caries (whether currently decayed, missing because of caries, or filled). This aligns with global benchmarks and with the idea that caries experience generally sits around the low-to-mid single digits on average for this age range. The other numbers would indicate a notably lower or higher burden than typically observed across populations in this age group, so they don’t fit as the best estimate for the average.

The thing being tested is which organization sets guidance on when to re-evaluate after using silver diamine fluoride (SDF). After SDF is applied, patients are followed to check whether the caries is arrested and to decide if reapplication or additional care is needed. This follow-up timing is most clearly defined by pediatric-focused dental guidelines, since children are the primary population using SDF for caries management. Among the major bodies, the American Academy of Pediatric Dentistry provides guidelines tailored to children, including recommended intervals for re-evaluation after SDF treatment. They offer practical pediatric follow-up timelines (often 6–12 months, adjusted for caries activity and risk) and emphasize regular reassessment to monitor arrest and determine if reapplication is warranted. While the ADA covers general dental practice guidelines and the WHO offers broad public health guidance, the most specific, child-centered recommendations on SDF SAMPLEre-evaluation timing come from the AAPD.

The key idea is the duration of exposure—the actual time sugar stays in contact with the tooth surfaces and plaque. When sugar is present in the mouth for a longer period, bacteria have more time to metabolize it and produce acid, increasing the risk of demineralization. Sticky or adhesive forms prolong this residence time, making the exposure last longer and enhancing cariogenic potential. Other factors influence how quickly sugar is cleared or how harsh the oral environment is, but they don’t determine how long the sugar itself remains in the mouth. Frequency affects how much sugar is delivered over time, but not the duration of each exposure. Saliva quality and flow help clear sugar and buffer acids, and pH affects the likelihood of demineralization, but the duration of the sugar’s presence in the mouth is what directly sets how long the teeth are exposed to cariogenic conditions.

Tooth-related factors are characteristics of the tooth that influence its susceptibility to decay. Tooth morphology matters because the shape of the tooth, including pits and fissures, creates niches where plaque and acids can accumulate, making caries more likely in those areas. Age influences tooth vulnerability since erupting teeth can have immature enamel, and with time, wear or root exposure can change how easily decay develops. Fluoride exposure directly affects the tooth by making enamel more resistant to acid attack and promoting remineralization, so teeth that have benefited from fluoride are less prone to decay. In contrast, factors like how quickly saliva clears the mouth, the pH of saliva, or how often you eat are environmental or behavioral influences rather than intrinsic tooth properties.