Abstract
Purpose: This study aimed to determine the influence of the thickness of a palatal plate on the mandibular position during continuous phonation of the sound [n].
Methods: Eleven healthy volunteers (10 males and 1 female; 24-36 years of age, mean age 26.4 years) were recruited from dental students. They were instructed to pronounce [n] continuously under six conditions: wearing a palatal plate with a thickness of 0.3, 1.5, 3.0, 5.0, and 10.0 mm, and without a plate (control). Mandibular movement during pronunciation was simultaneously recorded by a K-7 mandibular kinesiograph. Their mandibular positions in the physiologic rest position were also recorded. The distance between the incisal edge of maxillary and mandibular anterior teeth both in vertical and antero-posterior directions during continuous phonation of [n] (interocclusal distance) under all six conditions were measured and compared.
Results: Interocclusal distance tended to increase in both vertical and antero-posterior directions as the thickness of the palatal plates increased. There were statistically significant differences in the mandibular position both in vertical and antero-posterior directions during continuous phonation of [n] between the control condition and those wearing a palatal plate with a thickness of 10.0 mm.
Conclusion: The mandibular position determined by the phonetic method employing continuous [n] as a test pronunciation was affected by the thickness of the palatal plates inserted into the mouth. However, its influence was not significant when the thickness of the palatal plates was 5 mm or less.
