How are new bitcoins created without monetary inflation? As bitcoins are mined are older bitcoins retired? If not, how is monetary inflation prevented? Wouldn't the additional bitcoins cause the overall value of bitcoins to be deflated?
Bitcoins are created at a predetermined rate. Until this rate drops to 0 (around the year 2140), the supply of bitcoins is increasing. If this isn't offset by destroyed/lost coins and increased demand, some amount of inflation will occur. However, I'd expect the inflation rate to be low (if positive at all), and getting lower.

Once all ~21 million bitcoins are mined, no more will ever exist, so inflation will cease entirely, and only deflation can occur (again, as bitcoins are lost or intentionally destroyed). There are currently ~12.7 million bitcoins in existence, so at most, inflation will make 1 bitcoin today worth ~1.65 bitcoins in the future.