What Parents Should Know About Tooth Decay (And What They Can Do About It)

At Montshire Pediatric Dentistry, we spend a lot of time answering parents' questions. But here's one we like to ask back: what actually causes a cavity? The answer shapes everything about how we approach care. Most parents say sugar, maybe not brushing enough. That's not wrong. But it's incomplete in a way that really matters. Tooth decay is caused by a bacterial infection. Certain strains of bacteria live in the mouth, feed on sugar and carbohydrates, and produce acid as a byproduct. That acid wears down enamel and creates a cavity. The bacteria are driving the disease. The hole in the tooth is a symptom. Why This Changes Everything For most of dental history, treating a cavity meant addressing the tooth itself: removing the damaged area and restoring it. That's still sometimes the right call. But understanding decay as a bacterial disease opens up an additional set of tools, aimed at the infection itself. Silver Diamine Fluoride is one such tool: a liquid used in Japan since 1969 and FDA-approved in the US since 2014. The WHO lists it as an essential medicine, a designation reserved for treatments that are safe, effective, and accessible enough to meet fundamental healthcare needs globally. Applied in minutes, it kills the bacteria causing decay and stops a cavity from progressing. No numbing. No drilling. No sound that makes kids grip the armrests. It's a perspective that changed how we practice. Our co-founder Dr. Jonny Norris remembers sitting in a continuing education course on Silver Diamine Fluoride and feeling the floor shift. "How did I go through dental school, two residencies, and never hear about this?" The answer has less to do with the science than with how dentistry gets taught and paid for. But the tools exist, and more practices are starting to use them. There are other tools in this family: antimicrobial rinses, glass ionomer materials, and protective crowns placed without any tooth preparation at all. Glass ionomer is worth a particular note: it's a ceramic-based material (the glass in the name is literal) that bonds to teeth at the molecular level, mimicking the structure of natural tooth tissue. Unlike composite fillings, which are plastic-based, glass ionomer is biomimetic, meaning it behaves more like the tooth itself. Together these approaches make up what's called minimally invasive dentistry, or medical management of decay. The Three Things That Actually Cause Cavities Researchers describe the core drivers of decay as three things: the bacteria, the food source (fermentable carbohydrates, meaning sugars and starches), and time. Disrupt any one of the three and you significantly reduce the risk. Most parents focus on the food itself: cutting sugar, avoiding candy, reading labels. That's worth doing. But timing often matters more than content. Every time your child eats or drinks something other than water, the bacteria get a feeding window. It takes roughly 30 minutes for saliva to neutralize things. A cookie at lunch is one event. Sipping juice over two hours keeps the bacteria fed continuously. This is why constant grazing (even on healthy foods) is one of the biggest risk factors for decay that goes under-discussed. Three meals and a couple of discrete snacks gives teeth recovery time. Continuous snacking through the day doesn't. Age-by-Age: What Prevention Actually Looks Like "Most parents are doing more right than they think," says Dr. Norris. "A few small shifts make a real difference." Here's what those shifts look like at different ages. Under 2: The first dental visit should happen by age one, or within six months of the first tooth appearing. At this stage it's less about cleaning and more about coaching parents on feeding habits, wiping down gums, and making toothbrushing feel normal. Your dentist will advise on what toothpaste to use and how much. Ages 2–6: This is when the bacteria that cause decay can first be passed from parents and caregivers through sharing spoons, blowing on food to cool it, kissing on the mouth. None of these are reasons for alarm, but they're worth knowing. Brushing twice daily with toothpaste (ask your dentist about type and amount for your child's age), and keeping snacking structured, makes a real difference in these years. Ages 6–12: Most parents hand off brushing responsibility around this age, earlier than dentists typically recommend. Children often don't have the dexterity to brush effectively on their own until around age 8. The arrival of the six-year molars is also a key moment: these are the most decay-prone teeth in the mouth and excellent candidates for sealants. Tweens and teens: Orthodontic appliances make cleaning harder. Sports drinks and energy drinks do real damage. And dental anxiety absorbed from adults can lead to avoidance at exactly the age when habits are cementing. Keeping visits low-pressure and judgment-free matters more than ever. When Your Child Does Get a Cavity A cavity diagnosis does not automatically mean a drill. We always start by asking whether the infection itself can be treated before addressing the tooth. That approach has turned treatment plans that once quoted $8,000 to $10,000 into a few hundred dollars of care. Not a compromise in quality. A different understanding of what the disease actually is. Montshire Pediatric Dentistry was founded in Keene, NH by Dr. Jonny Norris and Dr. Colin Boswell. We now serve nearly 30,000 patients across 10 locations in New Hampshire, Vermont, Maine, and Massachusetts, and we accept all insurance including Medicaid. We'd love to meet your family. Learn more at montshirepediatricdentistry.com.