Statement of problem: The insertion of prosthodontic restorations often leads to speech defects, most of which are transient but nevertheless a source of concern to the patient. For the dental practitioner, there are few guidelines on designing a prosthetic restoration with maximum phonetic success.
Purpose: This study investigated the effect of different maxillary central incisor positions on phonetic patterns.
Material and methods: The inclination angle of central incisor blocks in duplicate complete maxillary dentures was changed in a range of -30 degrees to +30 degrees from the original position (0 degrees). Test words and sentences were acoustically analyzed. Spectral parameters such as first peak, noise band (defined by upper and lower limits of the most intensively blackened frequency area), Fast Fourier Transformation power spectrum, energy spectrum, and time were investigated. Influences of oral stereognosis, hearing, and age as cofactors on /s/ articulation were also taken into account.
Results: The change of incisor block angle in both directions usually caused a poorer execution of the /s/ sound. The labial angulation seemed to have a greater effect than the palatal angulation. The most significant changes were those in the noise band and energy spectrum.
Conclusion: Immediate phonetic adaptation of prosthetic restorations in the maxillary incisor region can be achieved only if the original position of the natural teeth is transferred to the denture. Although these misarticulations are, in most cases, likely to disappear within a few weeks, they may persist and even lead to psychosocial problems. A better understanding of the causes of misarticulation and the limits of adaptation according to certain morphologic parameters of dentures is important.