Purpose: To measure the influence of maxillary incisor length and inclination on sound production of the fricative /f/ using spectral analysis.
Materials and Methods: The complete dentures of 29 sufficiently treated patients were digitally duplicated. With the CAD/CAM programs GOM Inspect and Blender, the incisors were modified in four different ways (extrusion, intrusion, proclination, and reclination). Speech samples with the inserted, 3D-plotted test dentures were recorded. Spectral analysis of these /f/ sounds was performed using Praat software. The acoustic parameters center of gravity, standard deviation, skewness and kurtosis were examined by the Shapiro–Wilk, Kruskal–Wallis, and Nemenyi tests, with a significance level of 0.05.
Results: Compared to the original dentures, intruded and proclined maxillary incisors led to significant changes (p 0.02) in spectral characteristics of the /f/ sound. All four acoustic parameters showed measurable, statistically significant changes in the sound formation of the fricative /f/ as a result of the modified incisor position.
Conclusions: This impact can also be assumed for any type of tooth replacement in which the maxillary anterior teeth are involved.