The answer depends on your lease and its provisions.
However, your question is unclear: Are all monies due back "if the lease is silent?" I don't know what that means. What does a silent lease mean?
Often--but it all depends on the language of a lease--the lease is actually for a year (or perhaps 6 months). So let's say the rent is $1,000 a month. The lease often will state that the tenant owes $12,000 for a 12 month lease, payable in amounts of $1,000 a month for 12 months.
In that case, technically, the tenant owes not just the security deposit and first month's rent, but owes all 12 month's rent.
There are some exceptions in which leases can be broken--military orders, for instance.
But the clear answer lies in your lease.
Hope that helps.