Water temperature for fabrication of autopolymerizing polymethyl methacrylate (PMMA) interim fixed restoration affects cytotoxicity and residual methyl methacrylate (MMA).

Background/purpose: Clinically, dentists are suggested to immerse autopolymerizing interim fixed restorations in hot water during fabrication. However, this suggestion, without including the best temperature, mostly comes from clinical experience instead of scientific evidence. This in vitro study evaluated the effect of water temperature on the cytotoxicity of interim partial fixed dental prostheses (FDPs) and examined its correlation with residual MMA. Materials and methods: Tempron was chosen as the autopolymerizing polymethyl methacrylate material. Tempron was mixed and then soaked in water at different temperatures, except control group (Controlair) was not being soaking in water. The specimens were incubated with conditioned medium. The concentration of residual MMA was determined by liquid chromatography-tandem mass spectrometry (LC-MS-MS). The cell viability of human gingival fibroblasts (HGFs) was evaluated by MTT assay. Results: The 60 °C and 80 °C groups exhibited significantly higher cell viabilities than those of the other groups (P < 0.05) at 48 and 72 h. The concentration of residual MMA was highly correlated with this outcome: the higher the concentration of residual MMA detected in the eluates, the poorer the cell viability was; the longer the incubation time was, the stronger the correlation was between the concentration of residual MMA and the cell viability. Conclusion: Autopolymerizing PMMA interim FDPs that are polymerized in water up to at least 60 °C could reduce cell toxicity. Higher water temperature could certainly decrease the amount of residual MMA, which is closely correlated with the outcome of cell viability.

Accuracy comparison of scan segmental sequential ranges with two intraoral scanners for maxilla and mandible.

Background/purpose: The accuracy of a full-arch scan by using an intraoral scanner should be validated under clinical conditions. This study aimed to compare the accuracy of full-arch digital impressions in the maxilla and mandible using two intra oral scanners with three different scan segmental sequential ranges. Materials and methods: A dental model with 28 teeth in their normal positions served as the reference. Sixty full-arch scans were performed using Trios 3 and Trios 4, employing scanning strategy O (manufacturer's original method), OH (segmental sequential ranges one half), and TQ (segmental sequential ranges third quarter). Trueness was evaluated by comparing digital impressions with a reference dataset using specialized software. One-way ANOVA and Tukey tests assessed differences between the groups. Results: For Trios 3 on the maxilla, no significant difference was found among the groups of trueness; in the mandible, strategy O exhibited a significant difference (P = 0.008) with the highest deviation. For Trios 4 on the maxilla, strategy TQ demonstrated the lowest deviation with a significant difference (P = 0.006); in the mandible, no significant difference was found among the groups of trueness. Conclusion: Strategy TQ exhibited the best trueness for Trios 3 and Trios 4, suggesting it may be preferred for higher accuracy. Clinicians should consider these findings when selecting scanning strategies and intraoral scanners for specific cases.

Convolutional-neural-network-based radiographs evaluation assisting in early diagnosis of the periodontal bone loss via periapical radiograph.

Background/Purpose: The preciseness of detecting periodontal bone loss is examiners dependent, and this leads to low reliability. The need for automated assistance systems on dental radiographic images has been increased. To the best of our knowledge, no studies have quantitatively and automatically staged periodontitis using dental periapical radiographs. The purpose of this study was to evaluate periodontal bone loss and periodontitis stage on dental periapical radiographs using deep convolutional neural networks (CNNs). Materials and methods: 336 periapical radiographic images (teeth: 390) between January 2017 and December 2019 were collected and de-identified. All periapical radiographic image datasets were divided into training dataset (n = 82, teeth: 123) and test dataset (n = 336, teeth: 390). For creating an optimal deep CNN algorithm model, the training datasets were directly used for the segmentation and individual tooth detection. To evaluate the diagnostic power, we calculated the degree of alveolar bone loss deviation between our proposed method and ground truth, the Pearson correlation coefficients (PCC), and the diagnostic accuracy of the proposed method in the test datasets. Results: The periodontal bone loss degree deviation between our proposed method and the ground truth drawn by the three periodontists was 6.5 %. In addition, the overall PCC value of our proposed system and the periodontists' diagnoses was 0.828 (P < 0.01). The total diagnostic accuracy of our proposed method was 72.8 %. The diagnostic accuracy was highest for stage III (97.0 %). Conclusion: This tool helps with diagnosis and prevents omission, and this may be especially helpful for inexperienced younger doctors and doctors in underdeveloped countries. It could also dramatically reduce the workload of clinicians and timely access to periodontist care for people requiring advanced periodontal treatment.

Patient perception of service quality to preanesthetic oral examination: a cross-sectional study using the SERVQUAL model.

BACKGROUND: A phase-III interdisciplinary quality improvement program, the preanesthetic oral examination (PAOE), was implemented as a new program in an academic medical center to prevent perioperative dental injuries. This study was aimed at surveying the perceived service quality and satisfaction of patients who had undergone PAOE based on the SERVQUAL model. METHODS: This cross-sectional survey was conducted at the Kaohsiung Medical University Hospital using convenience sampling. Patients referred for PAOE (PAOE group) and those who had voluntarily availed dental services (control group) were recruited. A modified SERVQUAL questionnaire was used to assess the perceived service quality and patient satisfaction with dental services. Cronbach's alpha for SERVQUAL was 0.861. RESULTS: We enrolled 286 (68.8%) and 130 (31.2%) participants in the PAOE and control groups, respectively. The path analysis revealed that the PAOE group scored lower in dimensions of reliability (ß = -0.074, P = 0.003), responsiveness (ß = -0.148, P = 0.006), and empathy (ß = -0.140, P = 0.011). Furthermore, reliability (ß = 0.655, P < 0.001) and responsiveness (ß = 0.147, P = 0.008) showed a direct effect on patient satisfaction. Overall, participants were highly satisfied with the dental services. CONCLUSIONS: The PAOE group showed lower satisfaction and perceived quality of dental services compared to the control group. Although implementing an interdisciplinary program reduces the perceived service quality, its influence is limited. Employing an interdisciplinary teamwork is a win-win strategy encouraged to improve patient safety and reduce malpractice claims. Future suggestions should focus on establishing waiting times that are considered reasonable by patients. Patient-centered education related to the risk of perioperative dental injuries should be provided, and awareness of oral conditions for patient safety should be improved. Moreover, interprofessional education in continuous and undergraduate programs is necessary to improve professional quality.

IL17RB expression is associated with malignant cancer behaviors and poor prognosis in oral cancer.

OBJECTIVES: Previously, we demonstrated that IL17RB plays an essential role in lung cancer progression. This study aimed to determine whether IL17RB correlates with oral cancer and promotes oral cancer progression. SUBJECTS AND METHODS: IL17RB expression in oral cancer tissues and normal tissues was determined by immunohistochemistry staining, while the association of IL17RB expression with the clinicopathological characteristics of oral squamous cell carcinoma (OSCC) patients was analyzed and its correlation with progression-free survival and response to radiotherapy and chemotherapy in OSCC patients was also explored. Western blotting was performed to investigate the expression of IL17RB in various OSCC cell lines; moreover, transwell assay was performed to evaluate the effect of IL17RB expression on cell migration ability. RESULTS: In this study, we found that IL17RB was expressed higher in OSCC tissues compared to normal oral mucosa tissues and its expression was positively correlated with tumor size, lymph node metastasis, advanced cancer stage, and poor prognosis. In vitro study showed that IL17RB expression in OSCC cell lines as determined by Western blotting, was positively correlated with their migration ability. CONCLUSION: Clinical and in vitro studies suggest that IL17RB might serve as an independent risk factor and a therapeutic target for oral cancer.

Stress analysis and risk of failure during clenching in ceramic assembly models: 3-dimensional finite element analysis.

Background/purpose: Clenching is a dental parafunctional disorder that jeopardizes the life of teeth and/or dental prostheses. Computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated or 3-dimensional-printed dental prostheses are aesthetic, strong, and of good quality, but noticeable damage can still be observed after clenching. Stress analysis of synthetic ceramic assemblies with various parameters was conducted to provide data that may be used to improve the fabrication of CAD/CAM-fabricated dental prostheses. Materials and methods: Abaqus software was used to run the simulations. A total of 96 axisymmetric finite element ceramic assembly models were simulated under 800 N vertical loading and different contact radii (0.25, 0.5, 0.75, 1.0 mm), materials (IPS e.max CAD and Vita Enamic), layer thicknesses and combinations. Results: Four-layered ceramic assembly models produced promising results with the following parameters: contact radius of at least 0.5 mm, total thickness of at least 0.5 mm, and use of IPS e.max CAD as the first layer and Vita Enamic as the second layer without cement. Conclusion: The ideal four-layered assembly model design uses 0.25-mm-thick IPS e.max CAD as its outer layer to simulate enamel binding and 0.25-mm-thick Vita Enamic as its inner layer to imitate the natural tooth. This design may be used as reference for prosthodontic treatment.

Accuracy of intraoral scanning methods for maxillary Kennedy class I arch.

Background/purpose: The optimal strategy for scanning removable partial dentures remains unknown. This study investigated scanning strategies for patients with a maxillary Kennedy Class I arch as well as the measurement deviations of three scanning strategies. Materials and methods: A standard maxilla model was positioned with a holder in a dental chair to simulate a natural patient position and posture. Standard Tessellation Language files for reference models were formatted with a desktop scanner, and model operation files were obtained with a TRIOS 3 Pod intraoral scanner and superimposed using Exocad computer-aided design software. The three scanning strategies evaluated in this study (Strategy M, T-R, and R-T) were used for nine scans each, and the resulting data were recorded. The deviation of the three strategies was statistically analyzed through one-way ANOVA and Tukey post hoc testing. Results: The trueness of Strategy M, T-R, and R-T was 52.6 ± 31.0, 54.9 ± 27.6, and 50.1 ± 22.3 µm, respectively. No statistically significant differences in trueness were detected among the three groups (P > 0.05). However, Strategy T-R had the evenest distribution of all measuring points. The deviations of the measurements obtained by three scanning strategies were mostly between 30 and 70 µm. The precision of the three strategies was similar as well. Conclusion: Trueness did not differ significantly among the three strategies. However, Strategy T-R is recommended for use with a TRIOS 3 Pod scanner because of its reduction of the seesaw effect and high stabilization of the RPD framework.

Comparison of the plaque-removal efficacy of ultra-soft single-headed, triple-headed, and T-shaped toothbrushes and the subjective perceptions of users.

PURPOSE: To compare the plaque-removal efficacy of ultra-soft single-headed, triple-headed, and T-shaped toothbrushes and the subjective perceptions of users. METHODS: In this randomized, single-blind, crossover study, 30 healthy adult participants were randomly divided into three groups of 10, who tested the three types of toothbrushes in differing order, with a 1-week washout period between the tests. Dental plaque scores were recorded before and after toothbrushing, and questionnaires on subjective perceptions after toothbrushing were collected. RESULTS: The participants included 16 female participants and 14 male participants (average age: 29.4 ± 6.7 years). All three toothbrush types were effective in reducing dental plaque by 36-46%; however, the cleaning effect of the ultra-soft single-headed toothbrush was inferior to that of the triple-headed and T-shaped toothbrushes, the difference being statistically significant. The users' subjective perceptions suggested that the ultra-soft single-headed toothbrush was significantly superior to the other two toothbrush types. Plaque scores for the lower posterior tooth surfaces were higher than those for the upper posterior tooth surfaces, particularly on the left side, for both the ultra-soft single-headed and T-shaped toothbrushes. CONCLUSION: Healthcare practitioners should identify the type of toothbrush bristles used by individuals and provide appropriate oral health information.

Analysis of adult dental emergencies at a medical center in southern Taiwan.

Background/purpose: The need for dental emergency (DE) services has increased in recent years. This study therefore investigated the characteristics of patients presenting with DEs in a medical center in southern Taiwan. Materials and methods: This was a retrospective study of 1964 adult patients who presented with a DE at the Kaohsiung Medical University Hospital in 2018. Medical records providing age, sex, time, day, past visit history, chief complaint, diagnosis, and treatment were collected and analyzed. Results: The results revealed that men constituted 52.4% of the patients with DEs, the average age was 45.6 years, and the age distribution peak was 20-29 years (26.5%). The peak period for the DE visit was between 17:00 and 24:00 (42.1%), and the peak day of the week was Sunday (27.4%), followed by Saturday (18.0%). The most common chief complaint was pain (49.8%), and the diagnoses were as follows: pulp-related problems (36.7%), periodontal-related problems (22.9%), trauma (22.2%), odontogenic infection (15.3%), postoperative complications (9.2%), and temporomandibular disorders (3.7%). Dental treatment and medication were prescribed for 51.9% of the patients with DE. The rate of patients recommended for further dental treatment was 86.8%, and the actual return rate was 40.1%. Conclusion: This study revealed that the top three reasons for adult DE visits were pulp-related problems, periodontal-related problems, and trauma. These results may be used as a reference for dentists who provide DE services.

Effects of artificial intelligence-assisted dental monitoring intervention in patients with periodontitis: A randomized controlled trial.

AIM: To evaluate the effects of an at-home artificial intelligence (AI)-assisted dental monitoring application on treatment outcomes in patients with periodontitis. MATERIALS AND METHODS: Participants with periodontitis were recruited and randomly assigned to an AI (n = 16), AI and human counselling (AIHC; n = 17), or control (CG; n = 20) group. All participants received non-surgical periodontal treatment. We employed an AI-assisted tool called DENTAL MONITORING® (DM) intervention, a new technological AI monitoring product that utilizes smartphone cameras for intra-oral scanning and assessment. Patients in the AI and AIHC groups received additional (a) DM or (b) DM, respectively, with real-person counselling over 3 months. Periodontal parameters were collected at baseline and follow-ups. A mixed-design model analysed the follow-up effects over time. RESULTS: The AI and AIHC groups, respectively, exhibited greater improvement in probing pocket depth (PPD) (mean diff = -0.9 ± 0.4 and -1.4 ± 0.3, effect size [ES] = 0.76 and 1.98), clinical attachment level (mean diff = -0.8 ± 0.3 and -1.4 ± 0.3, ES = 0.84 and 1.77), and plaque index (mean diff = -0.5 ± 0.2 and - 0.7 ± 0.2, ES = 0.93 and 1.81) at 3-month follow-up than the CG did. The AIHC group had a greater reduction in PPD (ES = 0.46) and clinical attachment level (ES = 0.64) at the 3-month follow-up compared with the AI group. CONCLUSIONS: Using AI monitoring at home had a positive effect on treatment outcomes for patients with periodontitis. Patients who received AI-assisted health counselling exhibited better treatment outcomes than did patients who received AI monitoring alone.

Assessment of dental personal protective equipment (PPE) and the relationship between manual dexterity and dissemination of aerosol and splatter during the COVID-19 pandemic.

Background/purpose: Asymptomatic COVID-19 patients visit the dental clinic for routine treatment, during which, high-speed handpieces, and third-use sprayers can produce aerosols. We focused on the effect and possible inadequacy of personal protective equipment (PPE) while cleaning teeth and assessed whether doctors' proficiency was related to the range of spraying droplets. Materials and methods: Doctors were divided into three different groups: attending physicians, residents, and intern respectively. Each doctor treated 15 patients; each group comprised 30 patients. The dentists wore leg covers, shoe covers, medical masks, haircaps, full masks, waterproof barrier gowns, and gloves. Each patient was covered with a waterproof hole towel, and the upper edge was fixed to the patient's nose with a medical tape. After cleaning the teeth with water contained red pigment, the spattering distance and range of droplets were calculated. Concurrently, we examined whether there was any droplet contamination on the PPE. Results: With the exception of shoe covers, haircaps, and medical surgical masks, pigment splash marks were found on both the dentist and assistant's PPE. The interns performed cleaning for a significantly longer time than the residents and attending physicians, with a significant statistical difference (P < 0.05). The spatter distance for the interns was significantly larger than the residents (P < 0.05). Conclusion: It is recommended that the hole towel be centered on the patient's nose tip, at least larger than a radius of 54.9-64.5 cm. The dentist's proficiency did cause differences in the duration of teeth cleaning, which further affects the spatter distance.

Development and questionnaire-based evaluation of virtual dental clinic: a serious game for training dental students.

BACKGROUND: The volume of literature about serious gaming in dental education has increased, however, none of the previous studies have developed a serious game for closing the gap between preclinical and clinical training. OBJECTIVE: Virtual Dental Clinic (VDC) is a serious game that was created to help develop clinical reasoning skills in dental students. This study aimed to evaluate VDC as an educational tool and its effectiveness on clinical skill and knowledge gain among clerkship dental students. METHODS: The following three stages of VDC design and testing were addressed from 2016 to 2020: development, validation, and application. The VDC was developed using Unity game engine. In the validation stage, the content validity was reviewed by five visiting staff; construct validity and face validity were examined by 9 postgraduate-year dentists and 14 clerkship dental students. Concurrent validity and predictive validity were examined by 34 fifth-year dental students during their clerkship from September, 2018 to May, 2019, the associations between VDC experiences, clerkship performance, and the score on a national qualification test were explored. In the application stage, the VDC was set up as a self-learning tool in the Family Dentistry Department from August, 2019, quantitative and qualitative analyses were conducted using the 92 clerkship students' feedback. RESULTS: The VDC showed good validity and a high potential for education in practice. Students who have used VDC received significantly higher scores on qualification test (p = 0.029); the VDC experiences significantly predicted higher performance score on periodontics (p = 0.037) and endodontics (p = 0.040). After the outbreak of COVID-19 pandemic, significantly higher proportion of students confirmed the value of VDC as an assistant tool for learning clinical reasoning (p = 0.019). CONCLUSIONS: The VDC as an educational tool, and the effectiveness on clinical reasoning skills and knowledge gain among clerkship dental students has been validated and confirmed in this study.

Reduced tissue and serum resistin expression as a clinical marker for esophageal squamous cell carcinoma.

Esophageal cancer is one of the most common malignancies and leading cause of cancer-associated mortality worldwide. However, the molecular mechanisms underlying esophageal cancer progression and the development of clinical tools for effective diagnosis remain unclear. Resistin, which was originally identified as an adipose tissue-secretory factor, has been associated with obesity-related diseases, including certain types of cancer. Thus, the present study aimed to investigate the expression levels of resistin in tissue and serum specimens from patients with esophageal squamous cell carcinoma (ESCC) to determine the potential biological effects of resistin on ESCC cells. The results demonstrated that both tissue and serum resistin levels were significantly lower in patients with ESCC compared with healthy controls. In addition, resistin expression was positively associated with the body mass index of patients with ESCC. In vitro studies revealed that resistin inhibited the migratory ability of ESCC cells, while having no effect on ESCC cell proliferation. Taken together, these results suggest that resistin may have the potential to be developed into a clinical marker for ESCC. However, further studies are required to investigate resistin receptor expression and determine the potential involvement of resistin-associated biological pathways, which may provide insight for future development of targeted therapies for resistin-mediated ESCC.

Comparison of optical and crystal properties of three translucent yttria-stabilized tetragonal zirconia polycrystals with those of lithium disilicate glass-ceramic material.

BACKGROUND/PURPOSE: Among the ceramic materials used for all-ceramic crowns, zirconia has high biocompatibility and favorable mechanical properties, but its main drawbacks include low translucency and stress-induced phase transformation. To stabilize high-strength tetragonal zirconia polycrystal (TZP), 3-5 mol% yttria is usually added to prepare yttria-stabilized TZP (Y-TZP). In this study, the optical properties of three commercial Y-TZP ceramics were compared with those of the clinically available glass-ceramic material of lithium disilicate, and the relationship between translucency and crystal properties was analyzed in vitro. MATERIALS AND METHODS: Twelve 5-mm-thick standardized disks were prepared from three Y-TZP ceramics and one lithium disilicate block. Absolute translucency was measured using a spectrophotometer with an integrating sphere. X-ray diffraction was used to quantify the main structural parameters (i.e., preferred plane, quantitative phase, and grain size) of Y-TZP crystals. RESULTS: The product-dominated phase of Y-TZP exhibited a tetragonal lattice pattern, and the preferred planes had minor variations. The diffraction patterns of the three Y-TZP ceramics demonstrated minor effects on translucency, without significant differences (p > 0.05). The grain size of 54-70 nm was negatively related to translucency in Y-TZP. Lithium disilicate specimens had significantly higher translucency than the three Y-TZP specimens (p < 0.001). CONCLUSION: Grain size reduction played an essential role in developing highly translucent Y-TZP ceramics. The three Y-TZP ceramics were essentially opaque but exhibited poorer translucency than lithium disilicate in terms of esthetics.

Influence of commercial adhesive with/without silane on the bond strength of resin-based composite repaired within twenty-four hours.

BACKGROUND/PURPOSE: It is not clear whether the ground surface of resin-based composite (RBC) polymerized requires the application of an adhesive with/without a silane to improve bond strength. This study investigated the bond strength of RBC repaired within 24 h via the application of adhesive with/without a silane. MATERIALS AND METHODS: Seventy RBC blocks were prepared and assigned to either 0 or 24 h repair stage. Each stage was divided into seven groups: a control group with no surface roughening or applied adhesive, a surface-roughened group with no applied adhesive, two surface-roughened groups treated with a G-aenial Bond adhesive and a BeautiBond Multi adhesive, two surface-roughened groups treated with the previously-mentioned adhesives as well as silane coupling agents, and one group treated with a Single Bond Universal silane-containing adhesive. Microtensile bond strength (µTBS) measurements were performed after the repaired RBC blocks of each group (n = 5) had been immersed in a 37 °C water bath for 24 h. The failure mode of each sample was determined, and the data were analyzed via one-way analysis of variance and Dunnett's test (p = 0.05). RESULTS: Regardless of the repair stage, the µTBS values of the adhesive-only and silane-adhesive groups did not differ significantly from those of the control group (p > 0.05). Only the no-adhesive groups exhibited a significantly time-dependent increase in adhesive failure rate. CONCLUSION: Our results suggest that the application of adhesives either with or without silane can significantly increase the bond strength of repairs to RBCs polymerized within 24 h.

Association between the dental occlusion and perceived ability to eat foods of Taiwanese older adults.

Tooth loss is a common problem among older adults that affects masticatory function (MF) and food selection. Financial burden is a reason that some older adults in Taiwan with this condition forgo dental restoration. To identify the number of posterior occlusal support areas (POSAs) associated with MF. Large-scale cross-sectional study included 1100 community-dwelling participants of Taiwan aged ≥65 years. Participants completed dental examination and questionnaires through personal interviews. Masticatory performance was evaluated using a colour-changeable chewing gum. Masticatory ability was evaluated on the basis of how many of 14 common foods the participants were able to eat. Participants were grouped into 10 categories (A1-A3, B1-B4 and C1-C3) according to the Eichner index (EI) of posterior occlusal contacts. Multivariable regression models were used to analyse the association between the EI groups and MF. More than 80% of the participants with two or more POSAs (those in groups A1-B2) could easily eat various foods. Compared with those in groups A1-B2, those in groups in B3, B4, C1, C2 and C3 exhibited a significantly different masticatory performance (all P < .001) and significantly higher difficulty in eating fruits and vegetables. A dose-response effect between POSAs and perceived masticatory ability to eat fruits and vegetables was observed (P < .05 for both trends). Preservation of at least two POSAs is essential for MF. Older adults with tooth loss can undergo the restoration of two POSAs to improve MF and increase food intake.

The impact of the COVID-19 epidemic on the utilization of dental services and attitudes of dental residents at the emergency department of a medical center in Taiwan.

BACKGROUND/PURPOSE: Dental visits are a high risk activity during the COVID-19 pandemic. This study investigated the utilization of emergency dental services and clinical practical attitudes of dental residents in this period. MATERIALS AND METHODS: Retrospective chart data from 13th November 2019 to 31st March 2020 in Kaohsiung Medical University Hospital, Taiwan were used. We obtained electronic medical records to review data from 515 patients who visited the emergency department with dental complaints and we contacted the 26 residents assigned to act as primary care providers to participate in this study. RESULTS: After the COVID-19 outbreak, 17% fewer patients had dental emergency utilization at a hospital emergency center relative to the previous period. A survey of residents also showed a decline in the number of patients. There were no significant differences of patients' problems and diagnoses between the two periods. After the COVID-19 outbreak, 61.5% of the residents were afraid of being infected by a patient's disease and the proportions of dentists wearing waterproof gowns, face shields, and surgical hair caps were 76.9%, 88.5%, and 76.3%, respectively. These variables increased significantly after the outbreak of COVID-19. CONCLUSION: Despite the trend of a decreased number of patients, their utilization of dental emergency services seems to be similar before and after the COVID-19 outbreak, possibly related to strict hospital infection control policies and the relatively low number of COVID-19 confirmed patients internationally at that time.

Effect of toothbrush/dentifrice abrasion on weight variation, surface roughness, surface morphology and hardness of conventional and CAD/CAM denture base materials.

We evaluated the effect of toothbrush/dentifrice brushing on the weight variation and surface properties of different denture bases. Four denture base materials (conventional heat cure, high impact, CAD/CAM, and polyamide resins) were subjected to toothbrushing abrasion (50,000 strokes). The weight value, surface roughness, and topography of each group were determined before and after toothbrushing. The hardness was measured by the Vickers hardness test. Data were analyzed using ANOVA and Bonferroni tests. After toothbrushing, the weight of the polyamide resin had significantly increased; significant weight losses were observed for conventional heat cure and high impact resins, but none for the CAD/CAM resin. The surface roughness of each group increased significantly owing to the wear caused by toothbrushing. The weight variation and surface roughness were not affected by the hardness. Our results suggested that denture base materials deteriorate after brushing with toothpaste, in which the polyamide resin exhibited lower levels of abrasion.

A Study of Low Young's Modulus Ti-15Ta-15Nb Alloy Using TEM Analysis.

The microstructural characteristics and Young's modulus of the as-cast Ti-15Ta-15Nb alloy are reported in this study. On the basis of the examined XRD and TEM results, the microstructure of the current alloy is essentially a mixture (α + ß+ α' + α″ + ω + H) phase. The new H phase has not previously been identified as a known phase in the Ti-Ta-Nb alloy system. On the basis of examination of the Kikuchi maps, the new H phase belongs to a tetragonal structural class with lattice parameters of a = b = 0.328 nm and c = 0.343 nm, denoting an optimal presentation of the atomic arrangement. The relationships of orientation between these phases would be {0001}α//{110}ß//{1¯21¯0}ω//{101¯}H and (011¯0)α//(11¯2)ß//(1¯010)ω//(121)H. Moreover, the Young's modulus of the as-cast Ti-15Ta-15Nb alloy is approximately E = 80.2 ± 10.66 GPa. It is implied that the Young's modulus can be decreased by the mixing of phases, especially with the presence of the H phase.

Dysphagia and masticatory performance as a mediator of the xerostomia to quality of life relation in the older population.

BACKGROUND: The impact of poor oral health on older adults' quality of life is a public health problem. In this study, the mediating effects of dental status, occlusal condition, dysphagia, and masticatory performance on the association between xerostomia and oral health-related quality of life (OHRQoL) were assessed in the older adult population. METHODS: Stratified cluster sampling was used to recruit 1076 community-dwelling adults aged 65 years and older from Kaohsiung, Taiwan. Community care centers were randomly selected according to their geographic classifications (urban, rural, or mountainous areas). Assessments of dental status and occlusal condition were performed by dentists. Information on demographics, physical function, xerostomia, dysphagia and depression was collected through face-to-face interviews. Masticatory performance was evaluated using color-changeable chewing gum. OHRQoL was measured using the Geriatric Oral Health Assessment Index. Hierarchical regression models were used to assess the relationships between OHRQoL and physical function, dental status and oral function in older adults. Path analysis was used to estimate direct and indirect pathways between xerostomia and OHRQoL. RESULTS: Participants with xerostomia exhibited a 0.20 OHRQoL reduction (p < .001) compared with patients with no xerostomia, and the direct effect accounted for 83.3% of the total effect. Dysphagia and masticatory performance were found to exert significant mediating effects on the association between xerostomia and OHRQoL (ßs = 0.20 and - 0.12, respectively; both p < .001; ßs = 0.06 and - 0.09, respectively; both p < .05). Moreover, potential mediating effects of the number of functional teeth (ßs = - 0.11 and - 0.43, respectively; both p < .001) and occlusal condition (ßs = 0.09 and 0.13, respectively; both p < .05) on the relationship between xerostomia and masticatory performance were noted. CONCLUSIONS: Dysphagia and masticatory performance may serve as pathways through which xerostomia affects quality of life. Early oral function intervention may be a valuable and actionable target for older adults to maintain quality of life. Our results further suggest that checkup and screening for oral dysfunction are essential to prevent or delay the onset of complications.