During a cephalometric examination SNA is decreased. Which of the following is the most probable reason?
Maxilla (SNA)
Points A and B are regarded as the anterior limits of the apical bases of the maxilla and mandible, respectively.
Therefore, to determine whether the maxilla is positioned anteriorly or posteriorly to the cranial base, the angle SNA is noted.
The angle SNA is formed by sella-nasion and nasion to point-A. The mean SNA reading is 82 degrees, however, if the angular reading is greater than 82 degrees, it would indicate a relative forward positioning of the maxilla. Conversely, if the reading is less than 82 degrees, it would indicate a relative backward or recessive location of the maxilla.
Maxilla is retrognathic to anterior cranial base
Mandible is prognathic to anterior cranial base
Maxilla is prognathic to anterior cranial base
Mandible is retrognathic to anterior cranial base