You have not provided much information. To test whether your father has responded to Tenofovir treatment, he should test his viral load (hbvdna) and ALT in about 6 months' time. Tenofovir is very effective, his viral load and ALT should come down significantly from the baseline values. Generally, Tenofovir has to taken for at least several years or longer. In a few lucky patients, Tenofovir may be stopped after meeting several criteria and under the advice and straight supervision by a HBV specialists. Even fewer patients may achieve the endpoint of treatment by losing their HBV surface antigen. These are exceptions.