RESUMO
PURPOSE: To investigate the relationship of the vocal tract dimensions and dental arches in participants with substitution of palatal approximant /j/ for the trill variant of /r/. METHOD: Cephalograms and dental casts of 60 native speakers of Arabic were used for comparison. The experimental group included 30 participants with substitution of /j/ for the trill variant of /r/ (17 males and 13 females, age ranged between 15-20 years, M = 18.7 years, SD = 1.27). The control group included 30 normal speakers (15 males and 15 females, age ranged between 15-20 years, M = 18.3 years, SD = 1.67). Both groups had class I occlusion. RESULT: The experimental group showed significantly shorter maxillary length, p < 0.05, and narrower vocal tract dimensions compared to the control group, p < 0.05. Tongue length (TGL) and height (TGH) and soft palate length (PNSP) and thickness (MPT) were statistically significantly reduced in the experimental group compared to the control group, p < 0.05. The distance between the hyoid bone and retrognathion or C3 was significantly shorter in the experimental group compared to the control group, p < 0.05. Inter-canine widths and dental arch lengths were significantly shorter in the experimental group compared to the control group, p < 0.05. CONCLUSION: The substitution of /j/ for the trill variant of /r/ is associated with altered dimensions of the vocal tract. These alterations may explain the residual articulation disorder during the production of the trilled /r/ compared to other sound classes that respond to speech therapy. Orthodontic and Maxillo facial surgery consultation might be needed when providing therapy to individuals with this particular articulation disorder.
