Feeling like a failure

Our daughter had her dental cleaning yesterday ( Friday) and we found out she has like three cavities😞 and a-lot of decay . I don’t get it, my husband and i brush her teeth before bed and after breakfast in the morning. We have her drink water through out the day with the occasional juice, we feel like we just cant win. Its so frustrating, every time we take her to the dentist they find something wrong. Im terrified that she’ll need to have a procedure where they have to put her under, shes only three. Our poor little girl so young and already having so many things wrong with her teeth.