Relationship between the S-N plane and the Frankfort plane depending on the facial biotype

Resumen

The purpose of this study was to verify if the angle formed by the SN plane with the Frankfort plane (Bimler factor 7) tends to open in long-faced facial patterns (dolichofacial) and to close in shortfaced facial patterns (brachifacial). Material and methods: This was a comparative, retrospective, cross-sectional study. The study universe was initial digital lateral headfi lms of patients who attended the clinic of the Department of Orthodontics at the Division of Postgraduate Studies and Research of the UNAM. The lateral headfilms were taken randomly from the period between August 2010 and August 2012. The sample consisted of 100 radiographs of patients between 18 and 30 years of age, 50 brachifacial and 50 dolichofacial; previously classified using Bimler facial index and confirmed with Ricketts facial taper. Results: From the 100 measured radiographs, 58 belonged to female patients and 42 to male patients. The average age was 27 years, with an age range from 18 to 30 years. In the 50 radiographs of dolichofacial patients, there was a range of 7 to 14o and in brachifacial patients, a range of 3 to 8o of the SN-FK angle or Bimler factor 7. In the 50 X-rays of dolichofacial patients an average of 11o was found and in the 50 X-rays of brachifacial patients an average of 5o was found. Conclusions: On the basis of the results hereby obtained it may be observed that the angle formed by SN-Frankfort planes increases in patients with a vertical growth pattern (dolichofacial) and decreases in patients with a horizontal growth pattern (brachifacial).

Key words: Facial biotype, SN plane, Frankfort plane, Bimler factor 7.