Cephalometric variation of vertical dimension in patients treated with hyrax-type and McNamara-type rapid palatal expander. Study on latero-lateral teleradiography

To analyze changes in the vertical dimension of the lower third of the face studied on teleradiograph in L-L following rapid palatal expansion achieved by four-band Hyrax-type rapid palatal expander (RPE) and by acrylic-bonded McNamara RPE to identify the most appropriate therapeutic choice based on the patient's facial growth pattern. 30 patients were selected, of whom 20 (9 males and 11 females with a mean age of 8.285 ± 1.216) were treated using McNamara RPE (Group D), and 10 (6 males and 4 females with a mean age of 8.562 ± 1.152) were treated with Hyrax RPE (Group B), for an average treatment time T0-T1 of 0.96 ± 0.501 years. According to Tweed and Ricketts, Cephalometric tracings obtained from lateral cephalograms at T0 and T1 were analyzed to study changes in the vertical dimension of the lower third of the face. For this purpose, 6 cephalometric landmarks were considered: convexity (distance of point A to the NPg plane), Ricketts’ total face height (angle between the NBa plane and Xi-Pm plane), lower face height (angle between the ANS and Xi-Pm planes), facial axis (angle between the NaBa plane and PtGn plane), ANB angle, and FMA angle. No statistically significant differences were found between the measurements at T0 and T1 for any of the 6 cephalometric measurements considered, neither within the single groups nor when comparing the two. However, a greater increasing trend was found for some variables between the two groups, such as Ricketts' total facial height, lower facial height, and FMA angle, although not statistically significant. Hyrax and McNamara's RPEs have provided minimal changes in the vertical component during palatal expansion treatment, thus demonstrating their ability to preserve the vertical dimension of the face. Therefore, there are no contraindications for using either appliance for patients with dolichofacial growth patterns.