Best Filling Material for a Molar with a Thin Cavity

[DeeDoubleU]

If someone is highly reactive to lithium and doesn't want to lose too much good tooth structure for a filling on a molar, what is the best filling material for a molar with a thin cavity? Options include zirconia, lithium disilicate and composite. Durability and compatibility are important. The person with the thin cavity doesn't want galvanic shock of a dental material in the mouth and wants to stay away from BPA.