I am going to be blunt:
Again, polygraph is not going to do you any good.
Sure, cops are not supermen, but what they are is more objective and believable than a car load of drunks.
Since you are offering to get a dental mold means that at least one of the cops had bite marks. That is gonna hurt you. The police do not need physical evidence (or else how could anyone ever be pulled over for speeding, or arrested for assault?) but I wold say that officers with documented injuries and their testimony is gonna hurt you.
As to whether or not the force they used in arresting you was proper, again- that does not mean a thing in your criminal trial. If you battered a LEO, you battered a LEO; them tazing you or hitting you does not absolve you of that.
IIRC: they cannot use the assaulting a LEO charge against you, unless you testify. Them MAY be able to do so then, to attack your credibility. You need to stop attacking cops, because you are going to pay dearly for it one day.

