The quantity of sugar consumed matters less to teeth than the pattern of consumption. The reason is that each exposure triggers a recovery period of roughly fixed length, regardless of size.
Each exposure starts a clock
Plaque bacteria metabolize fermentable carbohydrate and release acid within minutes, dropping the pH at the tooth surface below the level at which enamel dissolves.
Saliva then buffers the acid and returns the pH toward neutral, a process that takes a period of time rather than happening instantly.
During that recovery window, mineral is being lost from the enamel surface. The tooth only begins regaining mineral once pH has recovered.
Frequency multiplies the total time spent acidic
A large portion eaten in one sitting produces one recovery period. The same amount divided across six occasions produces six.
Total acid exposure time is therefore governed by the number of separate events, not by the quantity in each.
This is why grazing, sipping sweetened drinks over an afternoon or keeping candy at a desk produces disproportionate risk relative to the amount consumed.
What counts as an exposure is broader than sweets
Bacteria ferment carbohydrates generally, so crackers, chips, bread and dried fruit can lower pH as effectively as obvious sugars.
Foods that stick to teeth extend the exposure, because the substrate remains available to plaque after the meal has ended. Retention in the grooves of molars is a common route by which a brief snack becomes a long exposure.
Acidic drinks add a second route by lowering pH directly, without requiring bacterial metabolism at all. Sugar-free versions can still be acidic enough to dissolve mineral on their own.
Meals differ from snacks chemically
Chewing a full meal stimulates salivary flow substantially, and stimulated saliva carries greater buffering capacity than saliva at rest.
Other components of a meal can also moderate the effect, and the whole episode still counts as a single exposure event.
Sugar consumed as part of a meal therefore presents differently to teeth than the same sugar consumed alone between meals.
Where the limits of general guidance lie
Individual risk depends on salivary flow, plaque control, fluoride exposure, existing restorations and tooth surface anatomy, all of which vary widely.
Medications reducing saliva, medical conditions and eating patterns tied to health needs change the picture and are not addressed by general dietary rules.
A dentist can assess an individual's risk and identify which surfaces are already affected, which is information no general guidance can supply.