I'm Getting Crowns in the Front 4 Teeth and I Grind my Teeth Bad at Night Would a Retainer Necessary?

For anyone who grinds their teeth as much as you say you do, I would recommend a night guard no matter what they had on their front teeth.  The fact that you are getting crowns will exacerbate any problems you might have.  They will hasten the wear of the lower front teeth because these teeth will be grinding against porcelain instead of enamel, which is a much stronger substance then the enamel.  You also increase the chance of chipping the porcelain of your new crowns if you are grinding on them 7-8 hours a night.  Do yourself a favor and get a night guard after the crowns are placed. 

An occlusal guard or a mouthguard is something that is recommended for patients to maintain any porcelain work in their mouths, especially if they are prone to grinding their teeth.