Decay in baby teeth develops through a chemical cycle rather than through poor cleaning alone. Frequency of exposure drives it more than quantity, which is why the pattern surprises parents.
Bacteria convert sugar into acid
The mouth carries bacteria that metabolise sugars and release acid as a by-product. That acid lowers the pH at the tooth surface within minutes of eating.
Below a certain acidity, minerals begin to dissolve out of the enamel surface. This demineralisation is the first stage and is not visible as a hole.
Saliva then buffers the acid and returns minerals to the surface over the following period. The tooth is constantly losing and regaining mineral rather than simply decaying.
Frequency matters more than quantity
Each exposure to sugar starts a period of acidity that lasts well beyond the eating itself. Recovery requires an uninterrupted stretch of time.
Eating a portion in one sitting produces one acid episode. Spreading the same amount across the day produces many, and the tooth never completes a recovery cycle.
This is why grazing and sipping sweetened drinks are treated as higher risk than a single dessert. The total sugar can be identical and the exposure profile is not.
Baby teeth are more vulnerable structurally
Enamel on baby teeth is thinner than on adult teeth, so the distance from surface to the softer dentine underneath is shorter.
Once decay passes into dentine it advances faster, because that layer is less mineralised. The progression from early lesion to a cavity needing treatment can be quick.
The nerve chamber inside a baby tooth is also proportionally larger, which is why decay reaches it sooner and why pain can appear without much visible damage.
Bottles and night feeding create a particular pattern
Saliva flow falls during sleep, which removes the main buffering mechanism. Anything sweetened taken at that point sits against the teeth with no clearance.
The resulting decay pattern typically affects the upper front teeth first, because the tongue shields the lower ones during sucking.
This is the reasoning behind guidance on bottles at bedtime and on moving to a cup during the second year, rather than a judgement about the contents alone.
Why baby teeth are still treated
Baby teeth hold space for the adult teeth developing beneath them. Early loss allows neighbouring teeth to drift, which affects alignment later.
Untreated infection in a baby tooth can also affect the developing adult tooth above it, as well as causing pain and disturbed sleep in the meantime.
Dental services examine children from the arrival of the first teeth, and decisions about treatment, fluoride and sealants belong with a dentist rather than being judged at home.