Situational simulation teaching effectively improves dental students' non-operational clinical competency and objective structured clinical examination performance.

BACKGROUND: Appropriate communication with dental patients enhances treatment outcomes and patient satisfaction. Implementing simulated patient interviews courses can improve patient-centered care and reduce conflict during clerkship training. Therefore, this study explored the relationship among student participation in a situational simulation course (SSC), academic performance, clerkship performance, and objective structured clinical examination (OSCE) performance. METHODS: This study was conducted with a sample of fifth-year dental students undergoing clerkship training. After implementing a situational simulation course to investigate the relationship among participation in SSC, academic performance, clerkship performance, and OSCE performance, a path analysis model was developed and tested. RESULTS: Eighty-seven fifth-year dental students were eligible for the SSC, and most (n = 70, 80.46%) volunteered to participate. The path analysis model revealed that academic performance had a direct effect on OSCE performance (ß = 0.281, P = 0.003) and clerkship performance (ß = 0.441, P < 0.001). In addition, SSC teaching had a direct effect on OSCE performance (ß = 0.356, P < 0.001). CONCLUSIONS: SSCs can enhance dental students' non-operational clinical competency and OSCE performance effectively. Simulated patient encounters with feedback, incorporated into the dental curricula, have led to improved communication. Based on our findings, we suggest implementing SSC teaching before the OSCE to improve communication and cognitive skills.

The impact of Lacticaseibacillus paracasei GMNL-143 toothpaste on gingivitis and oral microbiota in adults: a randomized, double-blind, crossover, placebo-controlled trial.

BACKGROUND: This study examines the oral health benefits of heat-killed Lacticaseibacillus paracasei GMNL-143, particularly its potential in oral microbiota alterations and gingivitis improvement. METHODS: We assessed GMNL-143's in vitro interactions with oral pathogens and its ability to prevent pathogen adherence to gingival cells. A randomized, double-blind, crossover clinical trial was performed on gingivitis patients using GMNL-143 toothpaste or placebo for four weeks, followed by a crossover after a washout. RESULTS: GMNL-143 showed coaggregation with oral pathogens in vitro, linked to its surface layer protein. In patients, GMNL-143 toothpaste lowered the gingival index and reduced Streptococcus mutans in crevicular fluid. A positive relationship was found between Aggregatibacter actinomycetemcomitans and gingival index changes, and a negative one between Campylobacter and gingival index changes in plaque. CONCLUSION: GMNL-143 toothpaste may shift oral bacterial composition towards a healthier state, suggesting its potential in managing mild to moderate gingivitis. TRIAL REGISTRATION: ID NCT04190485 ( https://clinicaltrials.gov/ ); 09/12/2019, retrospective registration.

Inducing cyclooxygenase-2 expression, prostaglandin E2 and prostaglandin F2α production of human dental pulp cells by activation of toll-like receptor-3, mitogen-activated protein kinase kinase/extracellular signal-regulated kinase and p38 signaling.

Background/purpose: Bacterial infection was the major etiology for pulpal/root canal infection. This study aimed to investigate the activation of toll-like receptor-3 (TLR) on cyclooxygenase-2 (COX-2) expression and prostaglandin E2 (PGE2) and PGF2α production of human dental pulp cells (HDPCs) and associated signaling. Materials and methods: HDPCs were exposed to different concentrations of Poly (I:C) (a TLR3 activator). Cell viability was determined by 3- (4,5-Dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay and alkaline phosphatase (ALP) activity was evaluated by ALP staining. Activation of extracellular signal-regulated kinase (ERK) and p38 by Poly (I:C) was determined by immunofluorescent staining. The COX-2 protein expression was analyzed by Western blot. PGE2 and PGF2α production was measured by enzyme-linked immunosorbent assay. The mRNA expression was studied by real-time polymerase-chain reaction. Moreover, HDPCs were exposed to Poly(I:C) with/without U0126 or SB203580 treatment and analysis of COX-2 expression and prostanoid production were conducted. Results: Poly (I:C) showed little effect on ALP activity, but decreased viability of HDPCs. It stimulated COX-2 mRNA and protein expression. Poly (I:C) induced PGE2 and PGF2α production of HDPCs. Poly (I:C) activated p-ERK, and p-p38 protein expression. Treatment by U0126 (a mitogen-activated protein kinase kinase (MEK)/ERK inhibitor) and SB203580 (a p38 inhibitor) attenuated Poly (I:C)-induced COX-2 mRNA and protein expression as well as PGE2 and PGF2α production. Conclusion: TLR3 activation is involved in the infection and inflammatory responses of pulp tissues, via MEK/ERK, and p38 signaling to mediate COX-2 expression as well as PGE2 and PGF2α production, contributing to the pathogenesis and progression of pulpal/periapical diseases.

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.

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.

Acceptance and experience of digital dental technology, burnout, job satisfaction, and turnover intention for Taiwanese dental technicians.

BACKGROUND: Digital dental technology (DDT) has progressed and been introduced to Taiwan in the recent years, gradually changing the industry ecology. Many studies have demonstrated that DDT is more accurate and faster than conventional dental technology. However, there is a paucity of research exploring dental technicians' perspectives on digital dental techniques, and their burnout, job satisfaction, and turnover intention. METHODS: This cross-sectional survey with convenience sampling was conducted at the conference venue of the Taiwan Association of Dental Technology to investigate the perspectives of dental technicians. We used the snowballing method in this study; two sampling methods were adopted, a convenience sampling of dental technicians to complete a survey, followed by asking the survey participants of the convenience sample to invite their colleagues to participate in the online survey. The survey questionnaire included questions on demographics, work-related information, acceptance and experiences of dental technicians toward DDT, occupational burnout, job satisfaction, and turnover intention. Regression models were used to determine the predictors of job satisfaction and determinants of turnover intention. RESULTS: In total, 341 valid questionnaires were obtained. Overall, the participants reported long working hours (95.5%), positive score on the DDT acceptance scale, moderate job satisfaction, higher personal burnout, and work burnout, along with lower over-commitment. Among them, 32.9% and 28.2% reported the intention to leave their organization and profession, respectively. The stepwise multiple regression model revealed that higher work burnout decreased job satisfaction, while higher DDT acceptance and position as employer increased job satisfaction. The binary logistic regression models revealed that geographical area of workplace, work burnout, and job satisfaction were significant predictors of turnover intentions. CONCLUSIONS: Many Taiwanese dental technicians reported turnover intentions and higher burnout. With the trend of digitalization in the dental industry, even though most dental technicians had a positive outlook toward DDT, its influence on job satisfaction appears limited. Retaining good and professional talents required of a dental technician is crucial, especially as Taiwan's dental care becomes increasingly specialized. Strategies for improving the work environment and occupational health of dental technicians should thus be the focus of future studies.

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.

The association between oral health status and the clinical outcome of cirrhotic patients on the waiting list for liver transplantation.

Liver transplantation (LT) candidates often present with poor oral hygiene, which could potentially lead to systemic infections and sepsis owing to their cirrhotic state. In this study, we investigated the oral health status of LT candidates and propose guidance for the detection and treatment of encountered oral lesions among these patients. The decayed, missing, and filled teeth (DMFT) index was determined through oral examination. The presence of dental calculus was detected using panoramic radiography and defined by the radiopaque dental calculus (RDC). From January 2011 to August 2018, 56 LT candidates were enrolled with a median follow-up of 39 months. The overall mean numbers of decayed, missing, and filled teeth among these patients were 2.7 ± 2.8, 10.9 ± 8.3, and 5.4 ± 4.5, respectively. Eighteen patients (32.1%) had RDC. The 5-year survival rates of all 56 patients was 57.7%, while that of those who either received LT (23 patients) or not were 82.1% and 39.8%, respectively. A Cox regression model revealed better overall survival of patients after LT (adjusted hazard ratio [aHR] = 0.067, p = 0.001), worse survival among patients with RDC (aHR = 3.468, p = 0.010), at Child-Pugh stages B and C (aHR for stage B = 11.889, p = 0.028; aHR for stage C = 19.257, p = 0.013) compared to patients at Child-Pugh stage A, and those with a model for end-stage liver disease (MELD) score ≥25 (aHR = 13.721, p = 0.018). This study demonstrates that RDC was associated with worse prognosis in LT candidates. We therefore recommend that interprofessional collaboration should be a routine preoperative procedure for the evaluation of oral hygiene among LT candidates.

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.

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.

The Association between Temporomandibular Disorder and Sleep Apnea-A Nationwide Population-Based Cohort Study.

An increased incidence of temporomandibular disorders (TMD) among patients with sleep apnea (SA) has been reported. However, the association between TMD and SA has not been demonstrated in a large-scale study. This population-based cohort study with the Taiwan National Health Insurance (NHI) Research Database aimed to understand the association between SA and TMD. We identified adult patients with suspected SA (identified with diagnostic codes) and excluded those diagnosed with TMD prior to SA. Patients with SA diagnosis after polysomnography were also identified as probable SA patients. The index dates were the dates of their initial SA diagnosis. Ten control subjects were matched, by age and sex, to each SA patient, and were assigned the same index dates as the SA patients. In total, 10,408 suspected SA patients (including 4105 probable SA patients) matched to 104,080 control subjects (including 41,050 subjects matched to the probable SA patients) in this study. The TMD incidence rate was significantly higher in the SA patients than in the control subjects (2.8 vs. 1.0 per thousand-patient-year in probable SA patients vs. the corresponding control subjects, with an adjusted incidence rate ratio [95% confidence interval] = 2.5 [2.3-2.7], p < 0.0001). SA patients significantly showed a higher cumulative incidence of TMD than the corresponding control subjects (p < 0.0001). Multivariable Cox regression analysis revealed SA as an independent risk factor for the development of TMD (adjusted hazard ratio = 2.5 [1.7-3.7], p < 0.0001). In summary, this study confirmed an increased TMD incidence in the SA patients. While treating TMD patients, dentists should pay careful attention to the potential underlying SA.

Effects of anxiety on dental students' noncognitive performance in their first objective structured clinical examination.

Patient-dentist discourse is a core nonoperational competency in dental education. The skills of querying patients and responding to questions are noncognitive attributes, and their evaluation by the standardized patient objective structured clinical examination (OSCE) is particularly necessary. However, it is not clear whether students' test anxiety affects these attributes. This study aims to examine the relationship between dental students' state-trait anxiety, noncognitive performance, and examination results during their first OSCE. A single dental school cohort (n = 226) of 5 year students attending their first clinical examination from 2014 to 2017 was studied. Participants completed the Chinese Mandarin Version State-Trait Anxiety Inventory Y form before taking the OSCE. The difference between state and trait anxiety levels was compared by paired t test. Gender differences and the effect of age group in these anxiety levels were analyzed using multivariate analysis of variance. Moreover, gender, age group, state anxiety, and trait anxiety scores were compared with the OSCE items of noncognitive performance using a chi-square test. Students showed significantly higher state anxiety than trait anxiety levels; moreover, women showed significantly higher state anxiety than men. Furthermore, gender, age group, state anxiety, and trait anxiety had no association with the noncognitive performance examination results. Most participants showed moderate state and trait anxiety levels during their first OSCE. Further, the state-trait anxiety had no significant effect on their noncognitive performance. However, 26.5% of participants did not pass the examination; therefore, dental educators should increase communication skill training courses during clerkship training to improve students' noncognitive attributes.

Influence of cavity depth and restoration of non-carious cervical root lesions on strain distribution from various loading sites.

BACKGROUND: We aimed to investigate the load-induced strain variation in teeth with unrestored and resin-based composite restored non-carious cervical lesions (NCCLs). METHODS: Twelve extracted premolars were provided for measuring buccal-side root NCCLs. Strain gauges were fixed at four measuring sites of each tooth, two at the buccal surface and two at the lingual surface. NCCLs were prepared with occlusal margins at the cemento-enamel junction. A static 9-kg load was applied at seven occlusal loading points: buccal cusp tip (BC), inner inclination of the BC, lingual cusp tip (LC), inner inclination of the LC, center of the mesial marginal ridge or distal marginal ridge, and center of the central groove. The strain was detected at each site in teeth with NCCL depths of 0 (control), 0.5, 1.0, and 1.5 mm. Each NCCL was restored using an adhesive composite resin, and the strains were re-measured. RESULTS: The strains at the NCCL occlusal and gingival margins decreased with increasing defect depths, and the effect was significant when the depth of the defect was 1.5 mm. Loading on the buccal and lingual cusps induced prominent strain variation. The strains at all depth distribution recovered to nearly intact conditions when the NCCLs were restored. CONCLUSIONS: NCCLs at 1.5 mm depth are detrimental, but they can be restored using resin composites. CLINICAL SIGNIFICANCE: The existence of NCCLs should not be ignored. The depth of the NCCL may affect the progression of the lesion. Resin composite restoration is an appropriate method for preventing persistent NCCL deterioration.

Effect of Ti2Cu precipitation on antibacterial property of Ti-5Cu alloy.

To instill pure Ti with an antibacterial effect, Cu was added by metallurgical alloying to produce Ti-5 wt% Cu alloy (Ti-5Cu alloy). The precipitation of the likes of Ti2Cu in a Ti-Cu alloy is one of the factors that influences its antibacterial property. However, in the present study, Ti-5Cu alloy precipitates with different microstructures were obtained by applying heat treatment at different temperatures and for different durations. After the heat treatment, metallographic, microstructure, and element analyses were performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDS). The antibacterial property of the Ti-5Cu alloy was assessed by the plated-count method using Escherichia coli (E. coli). The microstructure analysis revealed that the solution-treated alloy had no precipitation, while the aged alloy contained precipitations of intermetallic Ti2Cu compound. The aged alloy exhibited better antibacterial performance as the duration of the aging treatment increased. The optimal heat treatment for Ti-5Cu was found to be aging at 700 °C for 4 h, at which point the nucleation formation of the Ti2Cu particles would assume an acicular morphology. These acicular precipitates exhibit a high Cu content which, in turn, influences the antibacterial performance.

Work stress and occupational burnout among dental staff in a medical center.

BACKGROUND/PURPOSE: Research on work stress and occupational burnout among Taiwanese dental staff is scarce. Thus, this study aimed to explore work stress and occupational burnout among dental staff in a medical center. MATERIALS AND METHODS: This study is a cross-sectional survey that included the dental staff of a medical center in Taiwan. They were asked to complete self-reported questionnaires anonymously. The Questionnaire on Medical Workers' Stress (QMWS) was used to assess work stress, and the Maslach Burnout Inventory-Human Service Survey (MBI-HSS) was used to evaluate occupational burnout. In total, 108 valid questionnaires were collected, with a response rate of 79.9%. Data were analyzed using independent t-tests, one-way analysis of variance, Pearson's correlation, and stepwise linear regression. RESULTS: Overall QMWS score indicated that visiting staff perceived significantly higher stress than post-graduate year residents. Average scores of MBI-HSS showed dental assistants' scores as similar to those of high burnout groups; visiting staff and moderate burnout groups had similar scores. Stepwise regression analyses revealed that the significant predictor of emotional exhaustion was the QMWS score, of depersonalization were working as a dental assistant and QMWS score, and of personal accomplishment was holding a teaching position. CONCLUSION: Work stress and occupational burnout were common among dental staff; this may affect patient safety and should be valued. A stress management program is recommended to promote mental health of dental staff, along with adjustment of working environment, performance evaluation, and promotion systems.

Influence of the acidity of electrolyzed water on the microhardness of inner layer dentin.

BACKGROUND/PURPOSE: Electrolyzed water has been identified as an effective disinfectant that could represent as an alternative to sodium hypochlorite. Unfortunately, it remains unclear whether the texture or physical properties of dentin are affected by the application of electrolyzed water of different acidities. This study was aimed to assess the influence of electrolyzed waters with differing pHs on the demineralizing of inner dentin. MATERIALS AND METHODS: The coronal superficial dentin of 20 human molars was exposed and further bisected into two pieces perpendicular to the dentin surface. The samples were immersed in strongly acidic electrolyzed water (AW group), neutral electrolyzed water (NW group), 5% sodium hypochlorite (positive control, NL group), or deionized water (negative control, DW group). Microhardness of the inner layer dentin was measured at a depth of 25 and 50 µm beneath the superficial surface layer every 5 up to 60 min. RESULTS: At a depth of 25 µm, microhardness decreased with increasing immersion time in all but the DW group. The AW group exhibited a decreasing trend from the first 5 min that became significant after 35 min of immersion and was the most rapid decrease in the four groups. The rate of decline in the NW group was low and similar to that of the NL group. Both NW and NL groups exhibited significantly less demineralization than the AW group after 15 min of immersion. No significant microhardness change was found at a depth of 50 µm in any of the samples. CONCLUSION: AW produces a more pronounced softening of dentin than NW at a depth of 25 µm.

Short fish-origin DNA elements served as flanking sequences in a knockdown cloning vector enabling the generation of a functional siRNA molecule in mammalian cells and fish embryos.

Improving the quality of a siRNA-knockdown cloning vector requires simpler, shorter, and more effective flanking sequences. In this study, we designed such flanking sequences based on those found in zebrafish pre-miR3906, namely, internal element (IE) 1 and IE2. We engineered a vegf-shRNA fragment flanked by an 80-bp IE1/IE2 and then inserted into the 3' UTR of GFP reporter cDNA driven by a cytomegalovirus promoter to obtain a plasmid containing gfp-IE-vegf-shRNA-polA. Upon microinjection of this plasmid into zebrafish embryos, we found that IE flanking sequences could effectively induce the production of vegf-shRNA fragment, which was then processed into a functional siRNA to silence the target vegf121 gene. Northern blot showed that the vegf-shRNA fragment was cleaved from gfp-IE-vegf-shRNA-polA, resulting in the loss of polyA tails, subsequently degrading the remaining RNA-containing GFP. Moreover, Western blot revealed that addition of IE-based vegf-shRNA fragment could markedly decrease the expression of VEGF. Finally, to facilitate a more versatile application of the IE-based knockdown vector, we generated an inducible expression vector in which IE-vegf-shRNA was constructed downstream in a Tet-on system to generate a Tet-on-IE-vegf-shRNA construct. After doxycycline induction, the protein level of VEGF in SW620 cells harboring the Tet-on-IE-vegf-shRNA construct was decreased 77%. Interestingly, when SW620 cells harboring Tet-on-IE-vegf-shRNA cells were induced and transplanted into zebrafish embryos, we found that abnormal branch of the sub-intestinal vessels was reduced in the recipient embryos, suggesting that vegf-shRNA cleaved from Tet-on-IE-vegf-shRNA-polA was processed into a functional vegf-siRNA in embryos suppressing endogenous VEGF and reducing tumor angiogenesis. Therefore, we conclude that fish-origin IEs are flanking sequences with short, simple, and effective DNA elements. This IE-based knockdown cloning vector provides a new alternative material to facilitate the generation of functional siRNA with which to perform loss-of-function experiments, both in vitro (mammalian cells) and in vivo (zebrafish embryos).