The delicate balance of oral microbiota is frequently disrupted by exogenous discoloration and biofilm formation, thus requiring integrated antibacterial and whitening strategies. Conventional peroxide treatments often damage the integrity of tooth enamel, while nanocatalysts pose cytotoxicity risks. In this work, we designed a biocompatible polydopamine-engineered barium titanate nanocomposite (BTO@PDA_x). By optimizing polydopamine (PDA) shell thickness, BTO@PDA_0.5 exhibited superior excellent piezoelectric catalytic activity. Under ultrasound irradiation, PDA enhanced reactive oxygen species (ROS) generation by promoting charge carrier separation at the BTO interface, thereby accelerating chromogen degradation kinetics. Antibacterial assays and tooth whitening studies confirmed that BTO@PDA_0.5 could effectively inhibit microorganisms and degrade pigments with extremely low cytotoxicity. This study designed a highly biocompatible organic-inorganic composite piezoelectric material, providing a new strategy for oral health care.