Application of "cusp writer" findings to practical and theoretical occlusal problems. Part I

The cusp writer is a teaching aid used to facilitate understanding of the correlation between cusp angulation and the various occlusal determinants. Cusp writings represent an on-edge view of mandibular movement occurring in translation and rotation. Cusp writings demonstrate that: (1) the influence of incisal guidance on cusp angulation is almost 60 per cent greater in molars and 100 per cent greater in pre-molars than the influence of the condylar guidance; (2) steepening or flattening by wear, grinding, or reconstructing the lingual contour of the upper canine or other incisal guide teeth by as little as 1 mm. can change the incisal guide angulation from 15 to 25 degrees depending upon the vertical overlap; (3) these changes can create interceptive or deflective occlusal contacts with trauma and pain on the balancing side in the molar and temporomandibular joint areas; and (4) the incisal guidance of denture teeth is inevitably altered when teeth are tilted, uprighted, or turned for esthetics or phonetics. Such changes alter the occlusal function, harmony, and stability of the dentures.