Study of the natural head position in relation to the Frankfurt horizontal plane in mandibular evaluation of the Class I and Class II skeletal pattern

Sérgio Carmelo TÔRRES, Cláudio COSTA, Kurt FALTIN JR.

Aim: The present study aimed to compare the influence of natural head position (NHP) on Frankfurt plane behavior, as well as mandibular position evaluation, in a sample comprised by Class I and Class II facial patterns subjects. Methods: profile photographs of NHP were taken with the patients in a relaxed standing position looking into the reflected image of their own eyes in a mirror placed 1m in front of them. A plumb line was used to define the vertical plane (VER) on the photographs, and a line connecting soft tissue glabela and pogonion were transfered from the photograph to the lateral teleradiograph. A horizontal line (HOR) at a right angle to the vertical plane with the intracranial reference Frankfurt horizontal plane (HF) was used to assess the variability in relation between HF and NHP. The effects of the alterations of the NHP on the cephalometric measurements to evaluate the sagittal position of anterior contour of the mandibule (difference between Nperp-P and Nvert-P). The investigation was based on pre-treatment photographic and radiographic recordings of 60 patients selected in two groups based in the Class I and Class II skeletal pattern. Results and Conclusion: the results demonstrated a high and similar inter-individual variability between Frankfurt horizontal plane (HF) and a true horizontal line (HOR) in both groups. But the average reported a small mean difference among these references, no statistically significant and similar in both groups. The relation observed of the HOR.HF angle variation to the estimated calculation of the Difference between NperpP and Nvert-P was through the coefficient 1:2,119±0,029. This discrepancy of the sagittal mandibular diagnosis compromise orthodontic planning in the patients that showed difference between intra and extra-cranial horizontal planes. We emphasize the importance of the lateral facial and cephalometric evaluation to be accomplish in natural head position using the true horizontal and vertical planes as references.

Keywords: Natural head position. Cephalometry. Diagnosis.

Saturday, December 28, 2024 23:36