292EFFECTS OF RAPID MAXILLARY EXPANSION ON HYOIDMANDIBLE PLANE DISTANCE AND TONGUE LENGTH IN ORTHODONTIC TREATMENT: A COMPARATIVE STUDYA comparison was conducted between children who underwent orthodontic treatment with or without rapid maxillary expansion (RME) in terms of the hyoid-mandible plane distance (H-MP) and tongue length (TL). The study included 276 patients treated with RME and 296 controls treated without RME. Lateral and frontal cephalograms were used to assess intermolar distances, lateronasal widths, H-MPs, and TLs. Medical histories were reviewed for breathing difficulties, mouth breathing, demographics, and adenotonsillectomy history. Groups were matched based on age and gender. Descriptive statistical analysis was performed to summarize the results, and Chi-square tests and t-tests were used for group comparisons. The reliability of the data was assessed using the Kappa statistic, with a significance level set at P < 0.05. Results showed that the intermolar (IM) distance was lower in the RME group compared to the non-RME group (50.17 ± 2.3 vs. 51.58 ± 2.83). At T1, the IM was lower than the dental molar (DM) distance (26.18 ± 2.05 vs. 24.83 ± 1.99), as well as the lateronasal width (LNW) (24.83 ± 1.99 vs. 26.18 ± 2.05). The difference in the RME group was 15.69%, while in the non-RME group it was 13.86%. A greater difference was observed between the non-RME and RME groups in terms of LNW and IM (1.48 ± 1.38 vs. +0.98 ± 1.67). Comparing the RME group to the non-RME group, there were mean changes in T2 to T1 of 20.68 ± 3.67. However, there was no statistical significance in TL mean change, LNW, H-MP, or TL between T2 and T1. Overall, the study found no significant effects of RME on TL but significant effects on H-MPDr. Vinya Gadi kota@gmail.comResearch1022020Orthodontic treatment, Rapid maxillary expansion (RME), Hyoid-mandible plane distance (H-MP),Tongue length (TL), Intermolar distancesDr. Vinya Gadi kotaAssistant Professor, Department of Otolaryngology (ENT), Sri Lakshmi Narayana Institute of Medical Sciences, Puducherry - 605 502, India