The Dutch defender featured as the Reds overcame Sunderland on Saturday to preserve a 15-point lead at the head of the table, and he insists victory is the only option until the title race is over.
"It was an important win," Büttner told MUTV. "If we want to be champions then we have to win every game. We have to focus every week and win every game until the end. If we are champions then we can relax!
"We are in a good position but we have to try every week to play hard, not have any easy thinking and work hard for each other."
A narrow victory on Wearside was built on a sixth successive clean sheet in the league, and Büttner is similarly ambitious about avoiding concessions with regularity.
"It's good, of course, if you have a clean sheet," he said. "It's good for the defenders. You can trust each other and I think a big team like Manchester United should try to have a clean sheet in every game."
For Büttner, victory on Wearside was his second successive outing for the Reds, and his 11th appearance since joining from Vitesse Arnhem, and he feels he is now ready to begin his United career in earnest.
"It needs time and I needed a couple of months, when I came here for the first time, to settle in," he said. "It's started to be good now and I try to have my life set up here now. I know I signed for five years, so it's started to begin."