Morphological Comparison of Residual Ridge in Impression for Removable Partial Denture between Digital and Conventional Techniques: A Preliminary In-Vivo Study.

Although digital impression using an intraoral scanner (IOS) has been applied for removable partial denture (RPD) fabrication, it is still unclear how the morphology of a residual ridge recorded by digital impression would differ from that recorded by conventional impression. This in vivo study investigated the morphological difference in the recorded residual ridge between digital and conventional impressions. Vertical and horizontal displacements (VD and HD) in residual ridges recorded by digital and conventional impressions were assessed in 22 participants (15 female; mean age 78.2 years) based on the morphology of the tissue surface of in-use RPD. Additionally, the mucosal thickness of the residual ridge was recorded using an ultrasound diagnostic device. VD and HD were compared using the Wilcoxon signed-rank test, and the correlation of mucosal thickness with VD and HD was analyzed using Spearman's ρ. The VD of digital impression was significantly greater than that of a conventional impression (p = 0.031), while no significant difference was found in HD (p = 0.322). Meanwhile, the mucosal thickness showed no significant correlation with the recorded morphology of the residual ridge, regardless of the impression techniques. It was concluded that the digital impression would result in a greater displacement in the height of the residual ridge from the morphology of in-use RPD than the conventional impression.

Effect of Scanning Origin Location on Data Accuracy of Abutment Teeth Region in Digital Impression Acquired Using Intraoral Scanner for Removable Partial Denture: A Preliminary In Vitro Study.

The aim of this study was to investigate the effect of scanning origin location on the data accuracy of removable partial denture (RPD) abutment teeth region in digital impressions acquired by an intraoral scanner. A mandibular partially edentulous model including the following target abutment teeth was used: the left second molar (#37); left first premolar (#34); and right second premolar (#45). The following scanning strategies were tested: the strategy starting from #37 to mesial direction (37M); strategies starting from #34 to mesial (34M) and distal directions (34D), and strategies starting from #45 to mesial (45M) and distal directions (45D). The evaluated measures were trueness, precision, and linear accuracy. One-way and two-way ANOVA were performed for the comparison of trueness and linear accuracy, while Kruskal-Wallis test was performed for the precision comparison (α = 0.05). 45M and 45D showed significantly superior trueness of #34 to 37M and 34D. 45M also showed significantly superior trueness of #45 to 34. 45D showed significantly inferior linear accuracy of #34 and superior linear accuracy of #45 compared to other strategies. It was concluded that scanning origin location would have an impact on data accuracy of RPD abutment teeth region in digital impressions acquired by intraoral scanner.

Effect of night dentures on tooth mobility in denture wearers with sleep bruxism: A pilot randomized controlled trial.

PURPOSE: The purpose of this study was to investigate the inhibitory effect of night denture (ND) placement on abutment tooth mobility in removable partial denture (RPD) wearers with sleep bruxism (SB). METHODS: The participants were selected from RPD wearers diagnosed with SB using BiteStrip® and randomly allocated to one of the following groups: with ND placement or without ND placement (intervention or control group, respectively). The mobility of the RPD abutment tooth was measured using Periotest® at baseline (T0) and at 1 (T1), 3 (T3), and 6 months (T6). BiteStrip® scores were recorded at T0 and T6. Intragroup comparisons of the Periotest® value (PTV) were performed using analysis of covariance. Intergroup comparisons of PTV and BiteStrip® scores were performed using the linear mixed model and Wilcoxon signed-rank test, respectively. Intragroup comparisons of BiteStrip® scores were performed using the Mann-Whitney U test. RESULTS: At T6, the PTV in the intervention group was significantly lower than that in the control group (p=0.004). PTV was significantly lower at T6 than that at T0 in the intervention group (p=0.030), while PTV was significantly higher at T6 than that at T0 in the control group (p=0.007). There was no significant difference in the BiteStrip® score between the two groups. The BiteStrip® score at T6 was significantly lower than that at T0 only in the intervention group (p=0.011). CONCLUSION: ND placement might inhibit the increase in mobility of RPD abutment teeth and be effective in protecting them in RPD wearers with SB.

Evaluation of Respiratory Resistance as a Predictor for Oral Appliance Treatment Response in Obstructive Sleep Apnea: A Pilot Study.

The aim of this study was to determine the utility of respiratory resistance as a predictor of oral appliance (OA) response in obstructive sleep apnea (OSA). Twenty-seven patients with OSA (mean respiratory event index (REI): 17.5 ± 6.5 events/h) were recruited. At baseline, the respiratory resistance (R20) was measured by impulse oscillometry (IOS) with a fitted nasal mask in the supine position, and cephalometric radiographs were obtained to analyze the pharyngeal airway space (SPAS: superior posterior airway space, MAS: middle airway space, IAS: inferior airway space). The R20 and radiographs after the OA treatment were evaluated, and the changes from the baseline were analyzed. A sleep test with OA was carried out using a portable device. The subjects were divided into Responders and Non-responders based on an REI improvement ≥ 50% from the baseline, or REI < 5 after treatment, and the R20 reduction rate between the two groups were compared. The subjects comprised 20 responders and 7 non-responders. The R20 reduction rate with OA in responders was significantly greater than it was in non-responders (14.4 ± 7.9 % versus 2.4 ± 9.8 %, p < 0.05). In responders, SPAS, MAS, and IAS were significantly widened and R20 was significantly decreased with OA (p < 0.05). There was no significant difference in non-responders (p > 0.05). A logistic multiple regression analysis showed that the R20 reduction rate was predictive for OA treatment responses (2% incremental odds ratio (OR), 24.5; 95% CI, 21.5-28.0; p = 0.018). This pilot study confirmed that respiratory resistance may have significant clinical utility in predicting OA treatment responses.

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

BACKGROUND/OBJECTIVES: 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. METHODS: 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). RESULTS: 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. CONCLUSION: 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.

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 denture tooth thickness on fracture mode of thin acrylic resin bases: An experimental and finite element analysis.

STATEMENT OF PROBLEM: The optimum selection of denture teeth for patients with a reduced interarch distance has not been established. PURPOSE: The purpose of this in vitro study was to investigate the influence of denture tooth material and thickness on the fracture resistance of thin acrylic resin denture bases. MATERIAL AND METHODS: Acrylic resin (AC), composite resin (CO), or ceramic (CE) molar denture teeth were embedded in denture base blocks (2.0 mm thick). The distance from the central fossa to the tooth base was 0.5, 1.0, 2.0, or 2.5 mm for AC and CO, and 1.0 mm for CE (n=7), with a total thickness of 2.5 mm for all specimens. Each specimen was placed on a 3-point flexural setup with a shorter (8 mm) or longer (12 mm) support span than the tooth width and vertically loaded. A finite element analysis was performed to assess the stress distributions. The effects of tooth thickness and support span were statistically tested with ANOVA, followed by the Tukey honestly significant difference post hoc test (α= .05). RESULTS: With the shorter support, the mean fracture load was higher in CO than AC, regardless of the tooth thickness. Under the longer support, the mean fracture load with the CO decreased significantly as the tooth thickness increased, with increased maximum stress. Some CO tooth specimens of 2.0 mm or 2.5 mm thickness failed at the tooth-denture base interface at significantly lower loads than those exhibited by tooth fractures. CE showed minor cracks before bulk fracture. CONCLUSIONS: Higher fracture resistance was indicated with CO; however, the resistance decreased as the thickness of the CO tooth increased.

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 Tukey's 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.

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.