Which are more effective in preventing cavities, sorbitol or xylitol products?

Sorbitol and Xylitol are similar compounds.

From a standpoint of chemistry, sorbitol and xylitol are both similar. They are both classified as sugar alcohols (or more formally "polyol's"). And, as this name might suggest, both compounds are used as sugar substitutes.

Sorbitol is the most widely utilized polyol. It is commonplace to see it listed as the sweetener in over-the-counter medicines and sugar-free products, especially chewing gum. The reason for this is primarily related to cost. Sorbitol is less expensive than xylitol and therefore manufacturers tend to favor it.

Sorbitol is low-cariogenic as opposed to non-cariogenic.

Sorbitol does not share the same effectiveness in preventing tooth decay as xylitol. Using sorbitol-sweetened sugar-free products in replacement of their regular counterparts that are sweetened with sugar (sucrose) can be a very important step in a person's quest to find ways to reduce their cavity rate. But otherwise sorbitol use has limitations.

Unlike xylitol, cariogenic bacteria (the bacteria that cause tooth decay) can ferment sorbitol, although very slowly. This means that technically sorbitol does promote the growth of cariogenic bacteria. Additionally, sorbitol metabolism can result in the formation of acidic byproducts that might lead to tooth decay formation. (In the case of low to moderate sorbitol consumption the amount of acids produced should be of little clinical importance. In the case of a person with impaired salivary flow, however, the risk of sorbitol initiated decay might be significant.)

Because cariogenic bacteria can ferment sorbitol it should be considered to be a low-cariogenic sweetener rather than a non-cariogenic sweetener (like xylitol is). Using relatively moderate amounts of sorbitol-sweetened chewing gum, especially as a replacement for sugar-sweetened gum, can be a good thing. But, in terms of cavity prevention, it is not a better choice than choosing xylitol-sweetened products.

Products that contain xylitol and sorbitol.

Because sorbitol is cheaper than xylitol, a number of studies have evaluated xylitol-sorbitol combination products since they would be more cost effective. In general, however, dosing blends of sorbitol and xylitol have been found to be more effective at preventing tooth decay than sorbitol alone, but less so than pure xylitol products.