Influence of Oral Morphology on Speech Production in Subjects Wearing Maxillary Removable Partial Dentures with Major Connectors

Abstract

Background/Aims: Speech impairment during the initial phase of removable partial denture (RPD) treatment can prevent patient adaptation to RPDs. This study was undertaken to investigate the influence of oral morphology on speech production in subjects wearing RPDs with major connectors. Methods: Two types of connectors were fabricated for 17 subjects with normal dentitions: covering the middle palate (M-bar) and the anterior/posterior palate (AP-bar). Four target sounds ([∫i], [t∫i], [çi], and [ki]) were evaluated under 3 recording conditions: no connector, M-bar, and AP-bar. The mean appearance ratios of correct labels (MARCs) were calculated as parameters representing speech production accuracy with the speech evaluation system. Subgroup analysis was conducted based on palate height, dental arch width, and front space volume of the oral cavity. Results: Based on the multiple linear regression test, a significant association was found between the MARCs of [∫i] with M-bar and front space (p = 0.036). In the subgroup analysis, the AP-bar had a significant effect on the MARCs of [∫i] among subjects with high palate (p = 0.026), narrow arch (p = 0.004), and small front space (p = 0.014). Conclusion: RPDs with major connectors could disturb speech production among patients with high palates, narrow arches, and small front spaces.

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

“…However, the influence of major connectors on the target syllable [çi] was unclear, suggesting that changes in vocal tract shape could not significantly affect the accuracy of speech production in [çi]. This finding agreed with the results of previous reports focusing on maxillary RPDs [24][25][26].…”

“…Although many researchers have assessed the influence of maxillary denture designs on speech production, to our knowledge, no previous report has performed a similar assessment for mandibular denture designs. The target syllables of this study were selected according to the results of these previous studies [16,[22][23][24][25][26]. However, many consonants are produced by controlling the vocal tract shape with changes in the distance between the tongue and parts of the maxilla, such as the upper teeth, alveolus, and palate.…”

“…The speech data were evaluated using the speech evaluation system, following the procedures described in detail by Wada et al [26]. This system uses ASR based on 213 types of integrated phonetic segments that represent phonetic features and features of transitions from one phoneme to another [21, 23].…”

“…Using ASR for speech evaluation in daily clinical practice has important advantages as it requires little effort and avoids bias from practitioners. Using this system, we reported in detail the influence of various design-related aspects of maxillary RPD connectors located on the palate, such as the shape, running area, and cross-sectional shape, on speech production [22][23][24][25][26]. However, to our knowledge, no previous report has discussed the influence of mandibular RPD designs.…”

A Palatal Speech Bulb—A Case Study

“…Obturator design follows the basic principles for all removable prostheses of optimizing support, stability and retention alongside maintaining good oral health. The major connector was kept free of the anterior palate to help reduce plaque accumulation around the gingival margins and allow the patient's tongue to feel some of the natural hard palate [11,12]. An alternative design could have been to construct an all-acrylic prosthesis, using Adam's cribs to gain retention.…”