Enamel-strengthening toothpaste does make the enamel more acid-resistant; however, it doesn't strengthen the tooth physically. Good oral hygiene skills are a must in order to prevent cavities and other serious issues.
Enamel is vulnerable to decay and erosion. Decay is caused by the acids in bacteria and erosion occurs from the acids in foods and drinks. Everyone is susceptible to acid erosion, which is why dentists recommend that people brush twice a day and floss once a day.
Many toothpastes on the market claim to protect against the effects of acid erosion, but they do not provide full protection. Scientists studying enamel erosion recommend limiting the number of erosive foods and drinks.