12. 後牙牙冠缺損僅侷限於部分的咬合面與鄰接面時,保守且合適的選項是下列何者? (A)嵌體 (inlay) (B)冠蓋體 (onlay) (C)全牙冠 (full crown) (D)陶瓷融合金屬牙冠 (porcelain-fused-to-metal crown)