Which cephalometric index is described as higher than 4 mm in deep bite?

Which cephalometric index is described as higher than 4 mm in deep bite?

• A. IMPA angle
• B. Witts index higher than 4 mm
• C. SNA angle
• D. SNB angle

Answer: (B)

Witts appraisal uses the occlusal plane to assess the anteroposterior relationship of the jaws by projecting points A and B onto that plane and measuring the distance between their projections. This linear value reflects skeletal jaw discrepancy in a way that’s less influenced by the angle of the cranial base than some other angles. In a deep bite, there is often a skeletal tendency toward an increased AP disparity between the maxilla and mandible, which shows up as a larger Witts distance. When this distance exceeds about 4 mm, it supports a Class II–type skeletal pattern contributing to the deep bite, rather than changes caused purely by how the teeth are tilted or the cranial base position. The other indices give different kinds of information. The IMPA angle tells you how much the lower incisors are tilted relative to the mandibular plane, which affects bite depth but doesn’t measure the AP jaw relationship on the occlusal plane. SNA and SNB measure the positions of the maxilla and mandible relative to the cranial base, respectively, but they don’t provide the direct occlusal-plane projection distance that the Witts value represents.

Witts appraisal uses the occlusal plane to assess the anteroposterior relationship of the jaws by projecting points A and B onto that plane and measuring the distance between their projections. This linear value reflects skeletal jaw discrepancy in a way that’s less influenced by the angle of the cranial base than some other angles.

In a deep bite, there is often a skeletal tendency toward an increased AP disparity between the maxilla and mandible, which shows up as a larger Witts distance. When this distance exceeds about 4 mm, it supports a Class II–type skeletal pattern contributing to the deep bite, rather than changes caused purely by how the teeth are tilted or the cranial base position.

The other indices give different kinds of information. The IMPA angle tells you how much the lower incisors are tilted relative to the mandibular plane, which affects bite depth but doesn’t measure the AP jaw relationship on the occlusal plane. SNA and SNB measure the positions of the maxilla and mandible relative to the cranial base, respectively, but they don’t provide the direct occlusal-plane projection distance that the Witts value represents.