When my three-year-old granddaughter was diagnosed with a cavity, my first thought wasn’t just, She needs a filling. It was, How did we get here?
Fillings happen. Even in families who eat well, brush regularly, and avoid soda.
But when a cavity forms, it’s not just bad luck—it’s a sign that something deeper is going on. And if we don’t understand the root cause, it’s likely to happen again. So, here’s what I did…
In her case, the answer became clear: she had spent several weeks in the hospital battling a kidney infection. It was an incredibly tough time for her and her parents.
During that period, she was on IV antibiotics (which disrupt the oral microbiome), eating mostly hospital food, and—because her favorite animal is the panda—her parents indulged her love for Hello Panda crackers, letting her have as many as she wanted.
They felt awful seeing her so sick, and like any parents, they just wanted to bring her some comfort.
Unfortunately, that combination—microbiome disruption, ultra-processed snack foods, and reduced saliva flow—set the stage for her cavity.
And here’s the hard truth my daughter and son-in-law learned the hard way:
You Cannot Out-Brush or Out-Floss a Bad Diet
My daughter did everything “right” when it came to brushing and flossing. She was meticulous. And yet, her daughter still ended up with a cavity.
Why? Because diet is just as—if not more—important than brushing and flossing.
No amount of brushing can fully protect against a diet high in fermentable carbohydrates like Goldfish, Hello Panda crackers, and saltines—especially when those foods are eaten throughout the day.
These processed snacks break down into sugars that fuel acid-producing bacteria, creating the perfect storm for cavities.
This was a huge realization for my daughter: oral health isn’t just about what you do with a toothbrush and floss—it’s about what you put into your body.
When my daughter called me to tell me about the cavity, she was heartbroken.
“I feel so ashamed, Dad,” she said. “I should have known better. I grew up in your house. I run Ask the Dentist. How did I let this happen?”
And I get it. No parent wants to hear that their child has a cavity. But I told her exactly what I want to tell you:
Cavities are not a sign that you’ve failed as a parent.
They are a sign that something is out of balance—and once you identify why it happened, you can course-correct.
As dentists, we’re taught that cavities are a hygiene problem, but they’re actually a nutritional and microbiome imbalance problem.
It’s not just about brushing and flossing—it’s about what you eat, how you breathe, and the health of your oral microbiome.
I was fortunate to raise three daughters cavity-free, without fluoride. And I’m incredibly proud of that. But I also recognize that today’s world is different.
Parents today face more challenges—processed food is everywhere, stress levels are higher, and medications like antibiotics are more commonly used, often with unintended side effects on the microbiome.
So if your child has a cavity, don’t get stuck in guilt. Instead, take it as an opportunity to ask the right questions, make adjustments, and move forward.
After her filling, I put her on this exact protocol to restore her oral microbiome, remineralize her enamel, and make sure she didn’t end up back in the dentist’s chair anytime soon.
1. Checked for Mouth Breathing & Started Xylitol Nasal Spray
Mouth breathing is one of the most overlooked causes of cavities because it dries out the mouth, reducing saliva flow—the body’s natural defense against cavities. If a child snores, wakes up with a dry mouth, or is frequently congested, this should be addressed first.
While my granddaughter wasn’t a mouth breather, this is something I check in every child who gets a cavity. If she had been, I would have:
• Used a xylitol nasal spray (Xlear) to help clear nasal congestion and promote nasal breathing.
• Made sure she could breathe properly through her nose at night, since mouth breathing during sleep creates an ideal environment for cavities to form.
If your child has cavities despite great brushing habits, check for mouth breathing!
2. A Magnesium-Rich Lemonade Every Day
Magnesium is critical for strong enamel, but most kids (and adults) don’t get enough. I started having her parents make her a simple lemonade with:
- Filtered water
- A high-quality magnesium supplement (this is the one I recommend—scroll down and you’ll see where it says “raspberry lemonade”)
She loves it—it tastes like a fun treat, but it’s actually strengthening her teeth from the inside out.
3. Cod Liver Oil for Fat-Soluble Vitamins (A, D, E, and K2)
Fat-soluble vitamins—especially K2—are essential for directing minerals into the teeth where they belong. I told my daughter to give her:
- A daily teaspoon of high-quality cod liver oil (rich in vitamins A and D)
- Extra K2 in supplement form (since most kids don’t get enough from diet alone)
4. Oral Probiotics to Restore Her Microbiome
The bacteria in your mouth determine whether your teeth stay strong or develop cavities. After a round of IV antibiotics, her oral microbiome needed some help.
I added:
- An oral probiotic with Streptococcus salivarius like this one (code ATD15 to save 15%) to help repopulate her mouth with beneficial bacteria.
Fast-forward to today—my granddaughter is now seven years old, thriving, and cavity-free.
Her other smaller cavities were completely ARRESTED—to the surprise of her dentist—by brushing with Fygg varnish every night.
They’re monitoring it with X-rays, applying the ALARA principle—keeping exposure as low as possible while ensuring they’re not missing anything.
She’s still on her protocol—continuing with magnesium, cod liver oil, and Xlear nasal spray every night.
This experience taught my daughter something invaluable—not just about cavities, but about how to take control of oral health from the inside out. And now, instead of feeling shame, she feels empowered.
Cavities don’t happen overnight. They’re the result of an imbalance—sometimes caused by diet, sometimes by illness or medications, sometimes by mouth breathing and dry mouth. And while fillings are sometimes necessary, they should always come with a why.
For my granddaughter, we now know exactly what happened and how to prevent it from happening again. If your child has had a cavity (or you want to prevent one), start this protocol now. And remember: this is a shame-free zone. Cavities don’t mean you’ve failed as a parent. They just mean it’s time to make adjustments.
And if there’s one takeaway from this experience, it’s this:
You cannot out-brush or out-floss a bad diet.
To your great health,
Mark
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P.S. This newsletter is sponsored by BiOptimizers—my go-to magnesium supplement. I recommend it to all my patients, not just for better sleep, but also for cavity prevention and even reversal. Use code ASKTHEDENTIST for 10% off at checkout.
I often hear from people who say, “Magnesium didn’t work for me,” and my first question is: Were you getting all seven forms? Most supplements only contain one or two, but your body needs all seven for full benefits. If you know me, you know I’m extremely picky about supplements. BiOptimizers is one of the few brands I trust, thanks to their rigorous third-party testing and comprehensive formulation.
