Hi Janesore,
K08.55- Allergy to existing dental restorative material
L23.0-Allergic contact dermatitis (would not be appropriate for this case)


D2950 - core buildup, including any pins when required
D2740 - crown - porcelain/ceramic substrate


The codes listed above do not have direct crosscodes we are aware of, so you can either bill the "D" code on the medical claim (many insurers these days will process "D" codes when they are medically necessary services), or you can try the CPT codes below and include a narrative report describing the procedure:
41899 - Unlisted procedure, dentoalveolar structures
or
99070 - Supplies and materials (except spectacles), provided by the physician or other qualified health care professional over and above those usually included with the office visit or other services rendered (list drugs, trays, supplies, or materials provided)

Hope this helps!