RESUMEN
One of the common treatments of Class III patients is maxillary growth modification. In the last three decades in Mashhad dental school, maxillary deficiency has been treated by the Tongue Guard appliance. The purpose of this study was to assess the skeletal and dental effects of the Tongue Guard appliance in patients with maxillary deficiency. Pretreatment and post-treatment lateral cephalograms from 14 Class III patients [9 female and 5 male] with the mean age of 9.7 years were prepared in natural head position [NHP]. These patients were all treated by the Tongue Guard appliance. The mean value and standard deviations of SNA, SNB, A to N-perpendicular, FMA, Ul to FH, Ul to PP, L1 to GoMe,[pns-a.p.max][go-a.p.man] were calculated. SPSS Software and 2- tailed student's t-test with 0.05 significant levels were used for data analysis. Following the treatment, anterior movement of maxilla with significant increase in SNA and A to N- perpendicular were observed [p<0.005]. However, FMA remained unchanged after the treatment. The maxillary incisors were proclined and the mandibular incisors were retroclined, Also, significant increase in maxillary length and maxillary to mandibular length ratio were found.[p<0.05]. The Tongue Guard appliance increases SNA angle, as well as the distance from A to N perpendicular and Maxillary/Mandibular length ratio. But it does not affect facial height