Influence of the Covering Area of Major Connectors of Mandibular Dentures on the Accuracy of Speech Production: A Pilot Study

<b><i>Background/Objectives:</i></b> Speech impairment during the initial phase of removable partial denture (RPD) treatment can prevent patient adaptation to RPDs. This quasi-experimental study aimed to investigate the influence of the covering area of major connectors located in the mandibular anterior region on the accuracy of speech production. <b><i>Methods:</i></b> Fifteen adults (12 men and 3 women aged 26–40 years) with healthy dentition were recruited. Four target syllables were used for the assessments: [ʃi], [ʧi], [çi], and [ki]. There were four speaking conditions: without a connector (control), wearing lingual bar (5 mm width), wearing lingual plates (12 mm width), and wearing connectors covering the occlusal surface of lower dentition (16 mm width; CO). The accuracy of speech production was evaluated by mean appearance ratio of correct labels (MARC) and incorrect labels (MARIC) of the phonetic segments which were calculated with a speech evaluation system (VoiceAnalyzer). <b><i>Results:</i></b> The MARC in the 3 target syllables [ʃi], [ʧi], and [ki] significantly decreased with CO. For the target syllable [ʃi], the MARICs of [ʧi], [ʤi], and [çi] with CO were significantly lower than that in the control. For the target syllable [ʧi], the MARIC of [ki] with CO was significantly higher than that in the control. For the target syllable [çi], the MARIC of [gi] with CO was significantly higher than that in the control. <b><i>Conclusion:</i></b> RPDs with major connectors covering the lower dentition could disturb speech production during the initial phase of RPD treatment. Prosthodontic treatment with such RPD designs requires further consideration regarding the information given to patients before starting the treatment.