A custom bleaching tray or device with trench and material pocket/reservoir is disclosed. The device comprises a trench to avoid leakage of bleaching material onto the gingiva and a reservoir to precisely hold the bleaching material on the surface of the tooth. A method for forming a 3D-printed custom bleaching tray may include: providing or accessing teeth scan data associated with a patent's mouth; generating a digital model of the patient's mouth based on the teeth scan data, including manipulating the teeth scan data to form: a trench between one or more teeth and a gingiva region of the teeth scan data, and a bleaching material reservoir on a surface of each of the one or more teeth of the teeth scan data; and 3D-printing, based on the digital model, a 3D-printed bleaching tray. A thermoforming process may be applied to the 3D-printed bleaching tray.