Question: Class I

Answer: Buccolingual loss of tissue contour with a normal apicocoronal height

Question: Class II

Answer: Apicocoronal loss of tissue with normal buccolingual contour

Question: Class III

Answer: A combination of buccolingual and apicocoronal loss

Question: Ridge described according to the depth of loss: Mild

Answer: Less than 3 mm

Question: Ridge described according to the depth of loss: Moderate

Answer: 3-6 mm