Your gear probably needs a high degree of accuracy in order to mesh correctly. I have limited experience with 3D printing, but what little I have would indicate that high accuracy is difficult to obtain. Perhaps others here could comment on that aspect.

If you have an original gear you may be better off trying to cast the part. Use a flexible silicone molding material to make a mold and perhaps an epoxy resin for casting the gear. I have used several products from Smooth-On.com for casting larger parts, but never tried something as small as your gear.