As you mentioned you have caries in two teeth, irrespective of how much or which desensitizing tooth paste (such as vantej) you use, sensitivity will not come down. Consult a dentist to get the teeth restored with tooth colored composite fillings or silver filling. If the sensitivity is also associated with pain (which continue for more than a couple of minutes) , then you might need greater intervention such as root canal treatments. Sensitivity is a sign of something abnormal happening to your teeth.Just visit your dentist for a consultation, so that you don't repent with severe pain later.

There are a lot of caused of sensitive teeth,  right from abrasion caused by brushing,  bruxism,  erosion due to acidity,  to name a few.  The cavity that u mention about may be in two teeth together.  Get  good light cured composite fillings preferably with ceramic fillers for added strength. This is just a verbal consultation which is never complete without a proper clinical examination and x-rays to support the same.  Please feel free to consult me. 

I would advise you to get one intra oral x ray done to see the extent and depth of your cavity(caries ). As far as your hypersensitivity is concern, if it is only with cold then Vantej can be of some help, but if it is from both,hot and cold and sustains for a longer duration, then it is indicative of irreversible pulpitis and RCT is the appropriate treatment for that.

Hi.Based on the amount of decay or cavity u have. we can either do a cosmetic restoration or crown. Also, if the sensitivity is more, We can do root canal treatment and crown them.That will permanently solve the sensitivity and decay of your teeth. The crowns will protect them and give a good look esthetically.