Masayuki Hideshima

Influence of the major connector in a maxillary denture on phonetic function

PURPOSE The purpose of this study was to investigate the influence of the major connector in a maxillary denture. METHODS Eight patients with sound dentition were recruited in this study. The experimental connectors were fabricated with Co-Cr. Two positional designs were used: one was the middle type (M), and the other was the anterior and posterior type (AP). The six sounds, /shi/, /hi/, /chi/, /ki/, /ri/, and /ni/, were chosen as the test sounds. Using a speech recognition system, the intelligibility, change and duration of the test sounds were evaluated under three conditions: without connector (WO·C), with the M-type connector (W·M), and with the AP-type connector (W·AP). RESULTS The intelligibility in WO·C and W·AP was 86.9 ± 17.4% and 57.1 ± 30.1% for /shi/, 79.2 ± 19.7% and 70.5 ± 27.0% for /hi/, 74.7 ± 14.6% and 43.6 ± 24.3% for /chi/, 54.4 ± 16.5% and 23.2 ± 17.8% for /ki/, 85.2 ± 15.9% and 55.1 ± 30.6% for /ri/, and 76.9 ± 26.9% and 50.2 ± 31.3% for /ni/. Significant differences were recognized between WO·C and W·AP in /shi/, /chi/, /ki/ and /ri/(P<0.01). The intelligibility in W·M was higher than that in W·AP in all test sounds. As for incorrect labels, significant differences were recognized in the appearance ratio of /hi/ as the incorrect label in the test sound /shi/ (P<0.05). There were significant differences in some incorrect labels of /hi/ and /chi/. As for duration of consonant part, there was no significant difference in each test sound. CONCLUSION It was indicated that the middle type of the major connector would be recommended from a viewpoint of phonetic function.

Effect of mold temperatures on interface between primary and secondary castings of cast-on method for precision metal frameworks

PURPOSE The purpose of the present study was to obtain fundamental data for application of the cast-on method by evaluating the effect of mold temperatures on the interface between primary and secondary castings in detail. METHODS Silver-palladium-gold alloy (Ag-Pd-Au), type-4 gold alloy (Type4), and chromium-cobalt alloy (Cr-Co) were used in the present study. A polished flat, square metal plate, 10.0 mm x10.0 mm x 1.0 mm, was used as the primary casting. A wax pattern, 2.0 mm in diameter and 2.0 mm thick, was prepared for the secondary casting and invested together with the primary casting. The mold was heated at 600, 700 and 800 degrees C for Ag-Pd-Au and Type4, and 700, 800 and 900 degrees C for Cr-Co. After casting, the mold was embedded and sectioned. The cross-section was observed using a scanning electron microscope (SEM) and analyzed using energy dispersive X-ray spectroscopy (EDS). The gaps between the primary and secondary castings were analyzed for each alloy by analysis of variance and Tukeys honestly significant difference test. The significance level was set at 0.05. The heated primary casting without the secondary casting was examined using a thin film X-ray diffractometer (XRD). RESULTS Gaps were observed between the primary and secondary castings in all examined conditions. The primary casting surface was covered with oxide layers such as CuO and Cr(2)O(3), and became rough with an increase of the mold temperature. CONCLUSIONS The results suggested that the cast-on method was influenced by the mold temperature.

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

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.

Effect of jaw-opening exercise on prevention of temporomandibular disorders pain associated with oral appliance therapy in obstructive sleep apnea patients: A randomized, double-blind, placebo-controlled trial

PURPOSE There are no studies on the prevention of temporomandibular joint and/or masticatory muscle pain (TMD pain) associated with oral appliance (OA) therapy in patients with obstructive sleep apnea (OSA). The aim of this study was to determine the effect of jaw-opening exercise on TMD pain associated with OA therapy in OSA patients. METHODS Twenty-five OSA patients without pain-related TMD were consecutively enrolled into a two-arm, randomized, double-blind, placebo-controlled trial. One group performed jaw-opening exercise (JE, n=13), and the other group performed placebo exercise (PE, n=12) for 1-month, and had started 2-weeks prior to insertion of an adjustable OA. TMD sign using the Research Diagnostic Criteria for Temporomandibular Disorders and TMD pain intensity using a visual analog scale (VAS) in the morning and daytime were evaluated at baseline (pre-exercise) and at 2-weeks, 1-month, and 3-months after OA insertion. RESULTS Pain-related TMD was not observed in the JE-group at all evaluation periods, although one subject in the PE-group was diagnosed with arthralgia at the 1-month evaluation. The JE-group showed lower morning and daytime VAS scores than the those of the PE-group at all evaluation periods, and significant group differences were found in terms of chewing pain and jaw-opening pain in the morning at the 1-month evaluation, and of jaw-opening pain during daytime at the 3-month evaluation (P<0.05). CONCLUSIONS Within the limitations of the study, jaw-opening exercise prior to OA therapy reduced the risk of TMD pain associated with OA use. Therefore, jaw-opening exercise may contribute to the prevention of TMD pain.

Influence of the Width and Cross-Sectional Shape of Major Connectors of Maxillary Dentures on the Accuracy of Speech Production

Objective: To investigate the effects of the width and cross-sectional shape of the major connectors of maxillary dentures located in the middle area of the palate on the accuracy of phonetic output of consonants using an originally developed speech recognition system. Patients and Methods: Nine adults (4 males and 5 females, aged 24-26 years) with sound dentition were recruited. The following six sounds were considered: [∫i], [t∫i], [ɾi], [ni], [çi], and [ki]. The experimental connectors were fabricated to simulate bars (narrow, 8-mm width) and plates (wide, 20-mm width). Two types of cross-sectional shapes in the sagittal plane were specified: flat and plump edge. The appearance ratio of phonetic segment labels was calculated with the speech recognition system to indicate the accuracy of phonetic output. Statistical analysis was conducted using one-way ANOVA and Tukeys test. Results: The mean appearance ratio of correct labels (MARC) significantly decreased for [ni] with the plump edge (narrow connector) and for [ki] with both the flat and plump edge (wide connectors). For [çi], the MARCs tended to be lower with flat plates. There were no significant differences for the other consonants. Conclusion: The width and cross-sectional shape of the connectors had limited effects on the articulation of consonants at the palate.