Is xylitol better in sweets and toothpaste to prevent tooth decay?

Cochrane: This review has been produced to assess whether or not xylitol, a natural sweetener used in products such as sweets, candy, chewing gum and toothpaste, can help prevent tooth decay in children and adults. Tooth decay is a common disease affecting up to 90% of children and most adults worldwide. It impacts on quality of life and can be the reason for thousands of children needing dental treatment under general anaesthetic in hospital. However, it can easily be prevented and treated by good oral health habits such as brushing teeth regularly with toothpaste that contains fluoride and cutting down on sugary food and drinks. If left undisturbed, the unhelpful bacteria in the mouth - which cause decay - multiply and stick to the surfaces of teeth producing a sticky film. Then, when sugar is eaten or drank, the bad bacteria in the film are able to make acid resulting in tooth decay.
Xylitol is a natural sweetener, which is equally as sweet as normal sugar (sucrose). As well as providing an alternative to sugar, it has other properties that are thought to help prevent tooth decay, such as increasing the production of saliva and reducing the growth of bad bacteria in the mouth so that less acid is produced.
In humans, xylitol is known to cause possible side effects such as bloating, wind and diarrhoea.

Effect of natural sweetener Xylitol in preventing tooth decay still unproven

Scimex: The natural sweetener xylitol is unproven in preventing dental cavities in children and adults, according to a new research review by UK scientists. The researchers gathered data from almost 6000 participants in 10 different studies but didn't get a conclusive outcome from combining the results. While they did see weak support for adding xylitol to toothpaste, the authors concluded there was no evidence for its benefits in other products and were "particularly surprised to see such a lack of evidence on xylitol-containing chewing gums".