What term is defined as the level at which demineralization starts?

• A. Critical pH
• B. pH neutral point
• C. Buffering threshold
• D. Saturation point

Answer: (A)

The level at which demineralization starts is the critical pH. This pH is the point where the enamel’s mineral balance tips from remineralization to net dissolution in the presence of acid from plaque. When the local environment falls below this threshold, hydroxyapatite begins to dissolve faster than minerals can be redeposited, leading to mineral loss. Above this pH, saliva tends to remain supersaturated with calcium and phosphate, supporting repair of early lesions. In enamel, this critical pH is about 5.5, though it can shift with factors like fluoride that enhance remineralization. The other terms don’t specify the exact onset point: buffering capacity describes acid neutralization, the saturation point concerns the solution’s mineral status, and a neutral pH is simply where the solution is neither acidic nor basic.