If you are submitting the claim to dental you would use D9248 if it is being administered intramuscular or D9241 if it is being administered by IV.
If the claim is being submitted to Medical you would use the following codes:
Halcion -Currently no code
Vistaril IM - J3410
Vistaril Oral- Q0177
Versed IM, IV - J2250
Yes, it is appropriate to use D9971 for enameloplasty.