It was not a refutation of Jesus' words but an explanation as to why Jesus answered the Sadducees they way he did. The Jews did not hold the Melchizedek priesthood which has the keys to bind on earth and to bind in heaven. Thus under the Aaronic priesthood which they held, their marriages were not sealed or bound in heaven. Thus when they were dead, they were not married since it was not sealed or bound in heaven. As Cougarbear also stated, marriages are not performed in heaven but only on the earth. Thus if the seven brothers were not married by way of the sealing power of the Melchizedek priesthood by being sealed in heaven, then the marriages were not recognized in heaven. Thus they remain single in heaven. However, just as baptisms can be performed vicariously for the dead, so too can marriages through the Melchizedek priesthood be vicariously performed. Thus the great importance of doing work for the dead in our temples.
Christ was simply telling the Sadducees that under their current authority, it didn't matter how many times the woman married, their marriages were not of any eternal significance without the sealing or binding authority of the higher priesthood. They were not sealed or bound in heaven. No repudiation of Christ's teachings but simply an explanation to why their marriages were not valid in heaven. But Jesus did bestow upon Peter the authority to bind in heaven whatsoever he was to bind on earth, and that includes marriage.
