Unless there is an issue withhis teeth, Macullusion , where the teeth aregrowing out at weird angles or, are showing through the lipswhile in a resting position I wouldnt trimthe teeth at all thats only invitingproblems , once done wrong , its a lifetime of having totrim them and unnecessary stress on the rabbit . Differenttypes of hay and wood branches to chew onwill let the teeth wear naturally without you having to resort to trimming them up .
Unless they look something like this , better or worse there is no need to trim them up .
This is Injury related , not genetic ,Usually rabbits with this problem are bornwith it , but some like this rabbit willtend to bring it upon themselves by pulling onwire and or chewing wire . Hopethis helps some .