The problem of eroding you have mentioned seems to be due to erosion of enamel. This erosion is typicaly found in people who either use a lot of carbonated beverages or those who are using extensive methods of weight loss. I cannot make out by this question what is the reason for this in your case and I would like to mention that this does not spread to other teeth though you can say that other teeth are also getting involved. The method of treatment is first to identify the cause and then remove it. Secondly, you can use some desensitizing toothpastes like sequel-F, sensoform, cavifast, senolin etc. You have to apply and leave the paste for 15 minutes on your teeth twice daily. This will reduce the sensitivity. Finally once the process of erosion stops you can go for filling etc.