Do Muscularly Balanced Lower Dentures Influence Speech in Edentulous Patients?

Objectives: Regarding the fact that complete dentures (CD) affect speech sound production (SSP) several factors should be considered in complete denture construction. In many cases unstable CD, usually more often found in the lower jaw, have an adverse impact on SSP. To enhance denture stability conservatively, especially in patients with atrophic lower ridges, setting the teeth in an area where the forces of the surrounding muscles are balanced (neutral zone), has shown favorable results. Thus the aim of the study was to evaluate SSP in edentulous patients provided with a neutral zone denture (NZD) in the lower jaw before and after treatment.
Methods: 21 patients were included in this study. To identify the neutral zone a long-term impression (48 hours) was performed using a thermoplastic denture adhesive (Cushion Grip; Merck) applied to an acrylic base. Careful attention was paid to place the artificial teeth in the recorded neutral zone area using the impression as a template. A phonetically balanced text was read before (baseline) and after the treatment and was recorded digitally. These recordings were auditory evaluated by students (n=81) in different grades of dental education using marks 1 to 6 according to the German school system. Additionally, the denture stability while speaking was assessed by the patients (questionnaire).
Results: At baseline SSP was rated as 2.94 (95% CI [2.69, 3.19]). After treatment 14 patients (66.7%) perceived an improvement in denture stability while speaking, whereas seven patients (33.3%) reported no change. However, no significant improvement in SSP was observed (2.89 (95% CI [2.64, 3.14]); F-test p = 0.111).
Conclusions: Within the limits of this study it can be concluded that though NZD decisively improves denture stability the technique has no considerable impact on SSP in CD wearers.