Pre-doctoral dental students' computer-aided design/computer-aided manufacturing-related education, knowledge, attitudes and behavior: A national survey.

OBJECTIVES: Computer-aided design/computer-aided manufacturing (CAD/CAM) technology transformed the world of restorative dentistry. The objectives were to assess pre-doctoral dental students' CAD/CAM-related education, knowledge, attitudes, and professional behavior, and to explore the relationships between the year in dental school and these constructs. METHODS: A total of 358 pre-doctoral dental students from 17 of the 68 US dental schools responded to a web-based anonymous survey. RESULTS: CAD/CAM-related classroom-based education was likely to happen in lectures (87.2%) and simulated exercises as part of a class (86.9%). Faculty were most likely to provide CAD/CAM instruction (87.9%), with staff (44.8%) and dental technicians (20.2%) being engaged as well. Preclinical education included video demonstrations (81.8%), demonstrations during a lecture (76.4%) or for smaller groups of students (69.2%), hands-on workshops (65.6%), and individual instruction (50.4%). Considering the digital workflow in clinics, 45.2% reported using intraoral scans. The more advanced the students were in their program, the more CAD/CAM knowledge (r = 0.27; p < 0.001) and knowledge about what can be fabricated with CAD/CAM technology they had (r = 0.25; p < 0.001). However, the student's satisfaction with the education about CAD/CAM did not increase over the years (r = -0.04; n.s.) and remained neutral, while their attitudes became more positive the longer they were in dental school (r = 0.13; p < 0.05). Their attitudes were quite positive, with most students considering that CAD/CAM is the future of dentistry (5 = most positive: Mean = 4.34), agreeing that they enjoyed working with CAD/CAM (Mean = 4.11) and that CAD/CAM has the potential of making them a better dentist (Mean = 4.07). CONCLUSIONS: The majority of students in the US dental schools appreciate CAD/CAM technology, consider it to be the future of dentistry, and believe it makes them better dentists. The fact that the majority is not satisfied with their classroom-based, preclinical and clinical CAD/CAM-related education should therefore be a call to action to rethink dental school curricula in this content area.

The effectiveness of a 3D virtual tooth identification test as an assessment tool for a dental anatomy course.

INTRODUCTION: There has been a recent demand in dental education for distance learning and the use of virtual assessment tools that can leverage technology to potentially replace physical testing facilities. However, virtual tools that evaluate student learning should be validated prior to adoption. The aim of this study was to investigate the effectiveness, efficiency and user satisfaction of a 3D tooth identification test for a dental anatomy course that can be given remotely. MATERIALS AND METHODS: First-year dental students (n = 41) enrolled in a dental anatomy course took both traditional in-person practical and virtual 3D tooth identification tests consisting of 25 test items. The test scores, average test durations, faculty time commitment and user perception were collected and analysed. Pearson product-moment correlation coefficients (p < .05) were determined for the criterion measures including real tooth identification test scores, comprehensive written examination and overall grade for the course. RESULTS: The average number of correct answers for the real and 3D virtual tooth identification examination was 21.3 ± 2.65 and 20.7 ± 2.56, respectively. The average test duration for the real and 3D virtual tooth identification test was 25:00 and 21:16 min, respectively. There was a positive correlation (p < .05) of the 3D virtual tooth identification test with the real tooth identification test (0.368), comprehensive written examination (0.334) and the overall course grade (0.646). The total faculty time commitment for the real and 3D virtual tooth identification test was 96 and 65 min, respectively. The students cited difficulty in manipulating the 3D models. CONCLUSION: This study presents evidence that the 3D virtual tooth identification test can be used to assess dental students' understanding of dental anatomy effectively and efficiently.

Preclinical assessment of Class IV proximal contacts following different teaching strategies.

INTRODUCTION: Class IV composite restorations are one of the biggest challenges in dentistry. Furthermore, replacing adequate proximal contours on Class IV restorations is crucial for the function and aesthetics. The objective of this study is to assess four different teaching strategies used to improve first-year dental students' Class IV restoration proximal contact performance over a period of 4 years. MATERIALS AND METHODS: We assessed four cohorts of first-year dental students who were exposed to four different teaching strategies during the first-year preclinical training over two consecutive academic terms. The four different teaching strategies used were: (a) two waxing exercises (control cohort, strategy 1); (b) digital dentistry and four waxing exercises (strategy 2); (c) four waxing exercises (strategy 3); and (d) four waxing exercises and live demonstrations (strategy 4). All cohorts were exposed to the same didactic lecture of Class IV restorations. RESULTS: Our results showed that all teaching strategies resulted in better student's performance and content retention compared to the control cohort. However, the teaching strategy that resulted in the best pass/fail ratio was the association of waxing exercises with live demonstrations (strategy 4). DISCUSSION: Increasing the number of waxing exercises may improve students' performance either alone or associated with different teaching strategies. However, when associated with live demonstrations, waxing exercises have significantly reduced critical errors. CONCLUSIONS: Our study demonstrated for the first time the benefits of the affordable and traditional waxing exercises associated with instructor demonstrations as a teaching strategy for first-year dental students.

Pediatric Dentists' Educational Experiences, Attitudes, and Professional Behavior Concerning Resin Infiltration: Implications for Dental Education.

Minimally invasive dentistry (MID) is receiving increased attention. Resin infiltration (RI) is one micro-invasive technique for treating initial caries by sealing white spot lesions on tooth surfaces. The aims of this study were to assess pediatric dentists' RI-related educational experiences, attitudes, and professional behavior and to determine if their educational experiences were significantly related to their professional attitudes and behavior regarding RI. This cross-sectional study used an online survey to collect data from members of the American Academy of Pediatric Dentistry (AAPD) in March-April 2017. Of the 2,367 AAPD members invited to participate, 43 emails could not be delivered, and 273 surveys were completed, for a response rate of 11.8%. While only 9% of the 273 respondents reported that their classroom-based dental education had informed them about RI and only 1% that it had prepared them well to use RI with pediatric patients, higher percentages said they had been informed/prepared well by their classroom-based (24%) and clinical residency education (12%). The majority wanted to learn more about RI (71%) and would like to take a related CE course (59%). The respondents' average RI-related attitudes were positive (on five-point scale with 1=worst attitude: Mean=3.84). Regarding use of RI, 28% of respondents said they used RI sometimes and 4% often/very often, with 64% considering implementing RI in their clinics. Graduation year did not correlate with RI attitudes and use. However, the more education about RI the respondents had received during their residency (r=0.20; p<0.01) and in professional development after graduation (r=0.34; p<0.001), the more they used RI in their own work. This study found that the pediatric dentists' RI-related education was positively correlated with their professional behavior. Increasing predoctoral, resident, and continuing professional education about RI should therefore be considered.

Validity and User Experience in an Augmented Reality Virtual Tooth Identification Test.

By leveraging emerging technologies in augmented reality (AR) and virtual reality (VR), a Virtual Dental Library and AR virtual tooth identification test were developed at a U. S. dental school. The AR virtual tooth identification test is a vision- based AR application that uses three-dimensional models of extracted human teeth as test items. The aims of this study were to investigate the validity of the AR virtual tooth identification test and evaluate the users' experience with the virtual testing method. The AR virtual tooth identification test scores were compared with real tooth identification tests, scores on three quizzes, final exam, and final grade for the course to assess its validity. In addition, a survey was used to assess students' perceptions of the AR tool. In 2018, all 109 first-year dental students who had completed the dental anatomy course were invited to participate in the study. Of the 93 participants, 61 (56% of total students) were included in the correlation analysis (32 were excluded due to incomplete test answer sheets or missing criterion measures). All 93 could respond to the survey and provide comments. In the results, the AR virtual tooth identification test had a positive correlation with the real tooth identification test (r=0.410, p<0.01), a combined score of two real tooth identification tests (r=0.545, p<0.01), the final exam (r=0.489, p<0.01), and overall grade for the dental anatomy course (r=0.661, p<0.01). On the tests, the students had some difficulty in viewing and manipulating the images and experienced technical difficulties related to their smartphones, and their survey responses expressed little support for the AR tool. Nevertheless, this study demonstrated criterion validity of the AR virtual assessment tool for tooth identification.

Caries Removal by First-Year Dental Students: A Multisource Competency Assessment Strategy for Reflective Practice.

Multisource assessment (MSA) uses multiple assessors to provide feedback. Little is known about the validity of using MSA feedback for improving students' ability to self-assess in a preclinical environment. Therefore, the aim of this study was to measure the validity of using a defined reflective process involving an MSA tool for building skill in dental students' self-evaluation of caries excavation on extracted teeth. As part of this process, 104 first-year students at one U.S. dental school used a self-generated study plan (SGSP) for structured reflection on MSA feedback during the 2013-14 academic year. Interrater agreement, determined through calculation of percentage-agreements in scoring, was measured among three assessor groups (self-, peer, and expert assessors) in formative assessment and between two assessor groups (self- and expert assessors) in summative assessment two weeks apart, allowing for reflective practice and completion of an SGSP between assessments. Validity for improving self-assessment was determined by measuring significance in positive shifts of agreement between self- and expert assessors. The results showed that interrater agreement between the self- and expert assessors increased significantly: from a 28% agreement in formative assessment to a 60% agreement in summative assessment. Significance in percentage shifts between assessments was demonstrated with a McNemar score of 0.26 (p<0.001). These results suggest that the described MSA tool and reflective process in an SGSP may be valid methods for improving skill in student self-evaluation of competence in caries excavation on extracted teeth.

Cross talk initiated by endothelial cells enhances migration and inhibits anoikis of squamous cell carcinoma cells through STAT3/Akt/ERK signaling.

It is well known that cancer cells secrete angiogenic factors to recruit and sustain tumor vascular networks. However, little is known about the effect of endothelial cell-secreted factors on the phenotype and behavior of tumor cells. The hypothesis underlying this study is that endothelial cells initiate signaling pathways that enhance tumor cell survival and migration. Here, we observed that soluble mediators from primary human dermal microvascular endothelial cells induce phosphorylation of signal transducer and activator of transcription 3 (STAT3), Akt, and extracellular signal-regulated kinase (ERK) in a panel of head and neck squamous cell carcinoma (HNSCC) cells (OSCC-3, UM-SCC-1, UM-SCC-17B, UM-SCC-74A). Gene expression analysis demonstrated that interleukin-6 (IL- 6), interleukin-8 (CXCL8), and epidermal growth factor (EGF) are upregulated in endothelial cells cocultured with HNSCC. Blockade of endothelial cell-derived IL-6, CXCL8, or EGF by gene silencing or neutralizing antibodies inhibited phosphorylation of STAT3, Akt, and ERK in tumor cells, respectively. Notably, activation of STAT3, Akt, and ERK by endothelial cells enhanced migration and inhibited anoikis of tumor cells. We have previously demonstrated that Bcl-2 is upregulated in tumor microvessels in patients with HNSCC. Here, we observed that Bcl-2 signaling induces expression of IL-6, CXCL8, and EGF, providing a mechanism for the upregulation of these cytokines in tumor-associated endothelial cells. This study expands the contribution of endothelial cells to the pathobiology of tumor cells. It unveils a new mechanism in which endothelial cells function as initiators of molecular crosstalks that enhance survival and migration of tumor cells.

Bcl-2 orchestrates a cross-talk between endothelial and tumor cells that promotes tumor growth.

The current understanding of the interaction between the endothelium and cancer cells is fundamentally based on the concept that endothelial cells are responsive to differentiation and survival signals originating from the tumor cells. Whereas the effect of tumor cell-secreted factors on angiogenesis is well established, little is known about the effect of factors secreted by endothelial cells on tumor cell gene expression and tumor progression. Here, we show that bcl-2 gene expression is significantly higher in the tumor-associated endothelial cells of patients with head and neck squamous cell carcinomas (HNSCC) as compared with endothelial cells from the normal oral mucosa. Bcl-2 induces vascular endothelial growth factor (VEGF) expression in neovascular endothelial cells through a signal transducer and activator of transcription 3 (STAT3)-mediated pathway. Endothelial cell-derived VEGF signals through VEGFR1 and induces expression of Bcl-2 and the proangiogenic chemokines CXCL1 and CXCL8 in HNSCC cells. Notably, inhibition of Bcl-2 expression in neovascular endothelial cells with RNA interference down-regulates expression of Bcl-2, CXCL8, and CXCL1 in HNSCC cells, and is sufficient to inhibit growth and decrease the microvessel density of xenografted HNSCC in immunodeficient mice. Together, these results show that Bcl-2 is the orchestrator of a cross-talk between neovascular endothelial cells and tumor cells, which has a direct effect on tumor growth. This work identifies a new function for Bcl-2 in cancer biology that is beyond its classic role in cell survival.

Level of endothelial cell apoptosis required for a significant decrease in microvessel density.

Endothelial cell apoptosis plays a critical role in the disruption of blood vessels mediated by natural inhibitors of angiogenesis and by anti-vascular drugs. However, the proportion of endothelial cells required to mediate a significant decrease in microvessel density is unknown. A system based on an inducible caspase (iCaspase-9) offers a unique opportunity to address this question. The dimerizer drug AP20187 induces apoptosis of human dermal microvascular endothelial cells stably transduced with iCaspase-9 (HDMEC-iCaspase-9), but not control cells (HDMEC-LXSN). Here, we generated blood vessels containing several HDMEC-iCaspase-9:HDMEC-LXSN ratios, and developed a mathematical modeling involving a system of differential equations to evaluate experimentally inaccessible ratios. A significant decrease in capillary sprouts was observed when at least 17% of the endothelial cells underwent apoptosis in vitro. Exposure to vascular endothelial growth factor (VEGF(165)) did not prevent apoptosis of HDMEC-iCaspase-9, but increased the apoptotic requirement for sprout disruption. In vivo experiments showed the requirement of at least 22% apoptotic endothelial cells for a significant decrease in microvascular density. The combined use of biological experimentation with mathematical modeling allowed us to conclude that apoptosis of a relatively small proportion of endothelial cells is sufficient to mediate a significant decrease in microvessel density.

Avaliação do tratamento intensivo com clorexidina na redução das contagens salivares de estreptococos grupo mutans na fase de dentadura mista / Assessment of chlorhexidine intensive treatment on salivary mutans streptococci during mixed dentition

Introdução - Clorexidina tem demonstrado efetividade na redução das contagens de Estreptococos Grupo Mutans (SM) na saliva e placa dentária. Entretanto, poucos estudos clínicos avaliaram seus efeitos na dentadura mista. O objetivo deste trabalho foi avaliar o tratamento intensivo com clorexidina (gel a 1%) em comparação com o tratamento com flúor fosfato acidulado a 1, 23%, na redução das contagens salivares de SM em crianças ente 5 a 11 anos. Materiais e Métodos - Os participantes receberam tratamento odontológico na clínica de Odontologia Pediátrica do Hospital Universitário de Brasília - (HUB), Brasília - Brasil. Trinta e cinco crianças saudáveis foram alocadas em dois grupos formados por randomização simples (G1 /G2). O Grupo 1 (G1) recebeu seis aplicações de Clorexidina em dois dias consecutivos. O Grupo 2 (G2) recebeu duas aplicações de flúor durante 4 minutos, também em dois dias consecutivos. As contagens salivares foram realizadas através do Kit CARITEST SM - Herpo Produtos Odontológicos - Rio de Janeiro - Brasil, antes do tratamento (baseline) e após 4, 12 e 24 semanas. A análise estatística foi realizada pelo teste de Tukey (p<0,05). Resultados - Os resultados mostraram que somente no G1 as médias das contagens salivares foram significantemente reduzidas (82,14%). Após 24 semanas, houve aumento nas contagens salivares no G2 (não significativo) e tendência à redução nas contagens do G1, em comparação com a baseline. Conclusão - Os resultados permitem concluir que o tratamento intensivo com Clorexidina foi efetivo na redução das contagens salivares de SM durante 4 e 12 semanas após dupla aplicação, havendo, no entanto, retorno aos níveis iniciais ao final de 24 semanas.

Introduction - Chlorhexidine has been shown effective in reducing mutans streptococci (SM) counts in saliva and dental plaque. To date, few studies have compared its effects in mixed dentition children. The aim of the study was to assess the effects of an intensive treatment of 1% Chlorhexidine gel in comparison to a conventional fluoride preventive treatment on MS counts in saliva of children from 5 to 11 years old. Materials and Methods - All the participants received general dental care in the Pediatric Clinic at the Hospital of the University of Brasília - DF, Brazil . Thirty-five healthy children were randomly assigned in 2 groups. Group 1 (G1) received 6 applications of Chlorhexidine in 2 consecutive days. Group 2 (G2) received 2 applications of 1,23% sodium fluoride gel during 4 minutes. The MS salivary counts were determined by CARITEST SM Kit (Herpo Dental Products - Rio de Janeiro - Brazil) at the baseline, prior to treatments, and after 4, 12 and 24 weeks. The data were statistically analyzed by Tukey test (P<0,05). Results - Results showed that in G1 the MS mean counts were significantly reduced by chlorhexidine treatment at 4 and 12 weeks (82, 14%), while the G2 mean counts were not significantly affected. After 24 weeks there was a slight increase in MS counts in G2 (non significant) and a reduction tendency in G1, compared to the baseline counts. Conclusion - It was concluded that chlorhexidine intensive treatment was effective at reducing SM salivary counts during 4 and 12 weeks after double application, however there was a return to the baseline counts after 24 weeks.

Bcl-2 acts in a proangiogenic signaling pathway through nuclear factor-kappaB and CXC chemokines.

Vascular endothelial growth factor (VEGF) induces expression of Bcl-2 in tumor-associated microvascular endothelial cells. We have previously reported that up-regulated Bcl-2 expression in microvascular endothelial cells is sufficient to enhance intratumoral angiogenesis and to accelerate tumor growth. We initially attributed these results to Bcl-2-mediated endothelial cell survival. However, in recent experiments, we observed that conditioned medium from Bcl-2-transduced human dermal microvascular endothelial cells (HDMEC-Bcl-2) is sufficient to induce potent neovascularization in the rat corneal assay, whereas conditioned medium from empty vector controls (HDMEC-LXSN) does not induce angiogenesis. These results cannot be attributed to the role of Bcl-2 in cell survival. To understand this unexpected observation, we did gene expression arrays that revealed that the expression of the proangiogenic chemokines interleukin-8 (CXCL8) and growth-related oncogene-alpha (CXCL1) is significantly higher in HDMEC exposed to VEGF and in HDMEC-Bcl-2 than in controls. Inhibition of Bcl-2 expression with small interfering RNA-Bcl-2, or the inhibition of Bcl-2 function with small molecule inhibitor BL-193, down-regulated CXCL8 and CXCL1 expression and caused marked decrease in the angiogenic potential of endothelial cells without affecting cell viability. Nuclear factor-kappaB (NF-kappaB) is highly activated in HDMEC exposed to VEGF and HDMEC-Bcl-2 cells, and genetic and chemical approaches to block the activity of NF-kappaB down-regulated CXCL8 and CXCL1 expression levels. These results reveal a novel function for Bcl-2 as a proangiogenic signaling molecule and suggest a role for this pathway in tumor angiogenesis.

Avaliaçäo do tratamento intensivo com clorexidina e flúor na reduçäo das contagens salivares de estreptococos grupo mutans

A cárie tem sido considerada uma doença multicausal, tendo em sua etiopatogenia básica influência direta da microbiota bucal. Os principais microrganismos relacionados com o surgimento das lesões de cárie são os estreptococos grupos mutans. A prevenção e o controle da doença representa um grande desafio para a odontologia, pois as seqüelas ainda são detectáveis em grande parte das crianças brasileiras. O fator microbiota pode ser controlado com uso de antimicrobianos, entre eles iodo, xilitol, penicilina, própolis, flúor e clorexidina. A clorexidina é a substância melhor documentada e que apresenta melhores resultados, sendo ainda considerada como padrão-ouro para comparação de novas substâncias testadas. O objetivo deste trabalho foi comparar os tratamentos intensivos com cloreidina e flúor em relação à redução das contagens salivares de estreptococos grupo mutans. Para isso, foram analisados 2 grupos de crianças de 05 a 11 anos, com dentadura mista, que receberam o tratamento com clorexidina, grupo 1, e com flúor, grupo 2. Foram efetuadas 04 contagens salivares de cada grupo: a primeira antes do tratamento, a segunda após 04 semanas do tratamento, a terceira após 12 semanas e a quarta após 24 semanas. Além do tratamento químico, todas as crianças receberam 02 profilaxias dentais antes da aplicação da clorexidina e do flúor. Os resultados demonstraram que os tratamentos são distintos independentemente do tempo de observação, e que o uso da clorexidina levou à menor contagem média de estreptococos grupo mutans em relação ao uso do flúor. Concluiu-se que o tratamento com clorexidina exerceu efeito redutor significativo (p=0,05) nas contagens do microorganismo acima, e em ambos os grupos houve uma