1, Bow Design: Orthodontic Bow 2 is a traditional bow design with simple shape and straight bow string. Orthodontic arch 4 is a novel arch design, its shape is complex, and the bow string presents a certain curve.

2. Force transmission: Orthodontic arch 2 applies force evenly, which is suitable for general orthodontic cases. Orthodontic arch 4 can better adapt to complex tooth movement requirements and provide more accurate force control when applying force.

3. Arch wire size: The arch wire size of orthodontic arch 2 and arch 4 is also different. Bow 2 usually uses a thicker archwire, and Bow 4 uses a thinner archwire. This is also related to their power transmission characteristics.