You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is The orientation of the SN plane to the FH plane should be: and explain in detail?
An alternative horizontal reference line, easily and reliably detected on cephalometric radiographs, is the line from sella turcica (S) to the junction between the nasal and frontal bones (N). In an average individual, the SN plane is oriented at 6 to 7 degrees upwards anteriorly to the Frankfort plane.
Ref: Contemporary orthodontics, William Proffit, 4th edition page 207