how to destroy CustomGearJoint

Hi .everyone, I use newton physical engineer.
But now I can't find the method to destroy a CustomGearJoint.
I used new to build a joint:

OgreNewt::PrebuiltCustomJoints::CustomGearJoint* mgj=new OgreNewt::PrebuiltCustomJoints::CustomGearJoint(rel,(*itr)->getBody(),(*iitr)->getBody(),ParentPin,ChildPin);


But who can tell me how to destroy this CustomGearJoint? (Don't destroy the body)

delete mgj; // :p