the spots you are talking about can be just stains or initial carious lesion (cavity), it is important to get it examined since your dentist
has already examined it & is suggesting you for restoration/filling it is advised that you continue the treatment & get it restored.
these spots have potential to develop into severe lesion & may cause tooth pain, sensitivity & etc. restoring them at this stage would prevent any further complication....as we all know that prevention is better than cure...so get it treated.
flossing regularly and brushing twice a day is good to maintain your oral hygiene
.... i wud suggest use of flouridated toothpaste...this acts as anti-cariogenic i.e. it prevents occurrence of caries/cavities.