Mayoral P, et al. - In a young adult population, researchers determined the range of mandibular protrusion at various vertical points; 2, 5, 8 and 11 mm. Fifty-two students between the ages of 19 and 23 partook in the study with full permanent dentition. There were no significant differences in class I, II, and III. When building a mandibular advancement devices (MAD), there is an impact of increased inter-incisal distance from effective mandibular protrusion. As the vertical dimension increases, the mandible rotates later and places itself in a more retrusive position, reducing the range of mandibular progression (0.3 mm per 1 mm vertical increase). Limiting the amount of opening or increasing the vertical dimension in patients using MAD is recommended.