Yes, you can use the standard liners in the bottle. I used the standard liners with my oldest and drop ins with my second and my youngest who is 11 wks today. The standard liners were just as secure against spills and leaks as the drop ins.
I'm not sure of the true science behind it but from what I see the benefit to reducing gas using Playtex liners is that the baby doesn't have to break suction in order to continuously feed because the bag collapses with the milk as it drains. My son was gassy but it was determined that was caused by his formula. Once we switched formulas he no longer had gassy issues. So, using the playtex bottles does not guarantee no gas but does decrease the amount of gas they will have.
at 1:54 PM on Jun. 3, 2009