Introduction:

Determination of the SN-Frankfort angle has been a constant used for many decades with a value of 7°. However, several studies have refuted that statement, based on the influence of sociodemographic factors on the variation of this angle. On the other hand, the importance of its determination is crucial to achieve an accurate diagnosis.

Objective:

Evaluate the variation of the SN-Frankfort angle according to the facial biotype of patients.

Methods:

A descriptive cross-sectional observational retrospective study was conducted. The sample was 225 lateral cephalometric radiographs of patients aged 12-35 years attending the Orthodontics Service of Hipólito Unanue Hospital in the period 2014-2017. Inclusion criteria were complied with, and selection was made by simple random probability sampling. Manual tracing was performed to evaluate the cephalometric radiographs. Facial biotype was determined by the VERT index, and the SN-Frankfort angle was then obtained. Two statistical methods were used for agreement and reproducibility evaluation: the Kappa index for evaluation of the facial biotype and the interclass correlation coefficient for determination of the angle.

Results:

Average SN-Frankfort angle was 10.46 ± 3.02° for the dolichofacial biotype, 10.12 ± 3.03° for the mesofacial biotype and 10.39 ± 3.48° for the brachifacial biotype. Female patients had greater SN-Frankfort angulation (10.69 ± 3.04) than male patients (9.73 ± 3.23); p= 0.026.

Conclusions:

Variation was found in the SN-Frankfort angle according to the facial biotype, but those differences were not significant. Significantly greater SN-Frankfort angulation was found among female patients.

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