Highly efficient photocathodes for dye-sensitized tandem solar cells.

Thin-film dye-sensitized solar cells (DSCs) based on mesoporous semiconductor electrodes are low-cost alternatives to conventional silicon devices. High-efficiency DSCs typically operate as photoanodes (n-DSCs), where photocurrents result from dye-sensitized electron injection into n-type semiconductors. Dye-sensitized photocathodes (p-DSCs) operate in an inverse mode, where dye-excitation is followed by rapid electron transfer from a p-type semiconductor to the dye (dye-sensitized hole injection). Such p-DSCs and n-DSCs can be combined to construct tandem solar cells (pn-DSCs) with a theoretical efficiency limitation well beyond that of single-junction DSCs (ref. 4). Nevertheless, the efficiencies of such tandem pn-DSCs have so far been hampered by the poor performance of the available p-DSCs (refs 3, 5-15). Here we show for the first time that p-DSCs can convert absorbed photons to electrons with yields of up to 96%, resulting in a sevenfold increase in energy conversion efficiency compared with previously reported photocathodes. The donor-acceptor dyes, studied as photocathodic sensitizers, comprise a variable-length oligothiophene bridge, which provides control over the spatial separation of the photogenerated charge carriers. As a result, charge recombination is decelerated by several orders of magnitude and tandem pn-DSCs can be constructed that exceed the efficiency of their individual components.

Assessment of knowledge and competencies related to implant dentistry in undergraduate and postgraduate university education.

Learning in academic settings is strongly related to the way the students are tested or examined. Assessment therefore must be integrated in the curriculum design, coordinated and should reflect the learning outcomes of the education. Assessment within the field of implant dentistry must fulfil four major objectives: complete and direct the learning process with feedback (formative), ensure that students are adequately prepared (summative), assess attitudes and skills such as critical thinking, reflection and self-assessment ability, and supply continuous feedback to teachers on curricular content and impact. Different assessment methods should be used to assess different levels of competencies throughout the curriculum. Various forms of written or oral assessment methodologies are applicable at earlier stages in the curriculum. At intermediate levels, interactive assessment methods, such as patient simulations (paper based or virtual) and more could encourage the necessary synthesis of several disciplines and aspects of the theoretical knowledge. At higher levels of competence, documentation of clinical proficiency by means of reflective portfolios and diaries is an appropriate assessment method with both formative and summative potential. The highest level of competence requires performance assessment using structured, objective, clinical criteria. The group strongly encourages the use of reflective forms of assessment methods which engage the students in a process of self-appraisal, identification of individual learning needs and self-directed learning. The ultimate goal of this would be to allow the student to develop a lifelong learning attitude.

Teaching and assessment of implant dentistry in undergraduate and postgraduate education: a European consensus.

This paper constitutes a summary of the consensus documents agreed at the First European Workshop on Implant Dentistry University Education held in Prague on 19-22 June 2008. Implant dentistry is becoming increasingly important treatment alternative for the restoration of missing teeth, as patients expectations and demands increase. Furthermore, implant related complications such as peri-implantitis are presenting more frequently in the dental surgery. This consensus paper recommends that implant dentistry should be an integral part of the undergraduate curriculum. Whilst few schools will achieve student competence in the surgical placement of implants this should not preclude the inclusion of the fundamental principles of implant dentistry in the undergraduate curriculum such as the evidence base for their use, indications and contraindications and treatment of the complications that may arise. The consensus paper sets out the rationale for the introduction of implant dentistry in the dental curriculum and the knowledge base for an undergraduate programme in the subject. It lists the competencies that might be sought without expectations of surgical placement of implants at this stage and the assessment methods that might be employed. The paper also addresses the competencies and educational pathways for postgraduate education in implant dentistry.

Analgesic dose-response relationship of ibuprofen 50, 100, 200, and 400 mg after surgical removal of third molars: a single-dose, randomized, placebo-controlled, and double-blind study of 304 patients.

The purpose of this single-dose, randomized, placebo-controlled, and double-blind study was to evaluate the analgesic dose-response relationship of 50-mg, 100-mg, 200-mg, and 400-mg doses of ibuprofen after third molar surgery. Patients were instructed to take a single dose of either placebo or 50 mg, 100 mg, 200 mg, or 400 mg of ibuprofen when the postoperative pain was moderate to severe. Acetaminophen 500 mg was used as a rescue medication. Pain intensity, pain relief, and any possible adverse events were recorded on self-administered questionnaires hourly for 6 hours after intake of study medication. If rescue medication was taken, the time of intake was registered. A total of 304 patients entered the study, and 258 complied with the protocol. A positive analgesic dose-response relationship of 50-mg, 100-mg, 200-mg, and 400-mg doses of ibuprofen was observed when evaluated by pain intensity difference, sum of pain intensity difference, pain relief, total pain relief, and survival distribution of patients not taking rescue medication. Although significant pain relief was seen after a dose of 50 mg ibuprofen, ibuprofen 400 mg provided maximum pain relief and the longest duration of analgesic effect. Mild transient adverse events were reported by 6.8% of the patients. However, there was no significant difference in frequency between the placebo and 50 mg, 100 mg, 200 mg, and 400 mg ibuprofen dose groups.

Mandibular autorotation in orthognathic surgery: a new method of locating the centre of mandibular rotation and determining its consequence in orthognathic surgery.

Rotation of the mandible is simulated through the centre of the condyle in planning orthognathic surgery. Previous studies have suggested that the initial mandibular movement is better characterized as multiple parts of the segments of a circle with the average centre located below and behind the centre of the condyle. This paper describes a method of locating the centre of mandibular rotation by computer-analysis of two lateral cephalograms with different degrees of opening. The method was used on 10 normal individuals showing an average centre of mandibular rotation 14.9 mm below and 5.0 mm behind the superior midsurface of the condyle for movements from occlusion to an opening of 10 mm. The implications of the located centre of rotation on orthognathic surgery was determined by simulating a closure of a 9.5 mm open bite. An error of up to 9.3 mm in the horizontal position of the maxilla would occur if the centre of the condyle was used. A retrospective study on 10 patients with increased anterior facial height was undertaken and a mean centre of rotation 8.4 mm behind and 25.1 mm below the centre of the condyle was found. Simulating the rotation of the mandible through the centre of the condyle would have resulted in a difference between the predicted and actual horizontal position of the maxilla ranging from 0.4-10.4 mm. It was concluded that using the centre of the condyle as the centre of mandibular rotation in the planning of superior maxillary movement with a Le Fort I osteotomy may cause considerable error in the horizontal position of the maxilla in most cases.

Pulp sensibility and pulp necrosis after Le Fort I osteotomy.

A longitudinal study comprising 617 teeth in 51 patients was carried out to determine the frequency of pulp necrosis and loss of pulpal sensibility after Le Fort I osteotomy. A negative pulpal sensibility was found in 39 (6%) teeth after an average follow-up period of 28 months, range 11-59 months. Development of pulp necrosis, determined by pulp testing and periapical radiolucency, was only demonstrated in 3 (0.5%) teeth. The extent of horizontal or vertical displacement of the maxilla had no influence on pulpal sensibility. Teeth adjacent to a vertical interdental osteotomy showed a significantly higher frequency of negative reactions compared to the group without an interdental osteotomy (p = 0.002). The canines demonstrated a significantly greater number of teeth with a negative sensibility reaction compared to the other tooth types. A close relationship between the apex of the canines and a wire osteosynthesis was demonstrated to have significant importance for pulpal sensibility.

The significance of an erroneous recording of the centre of mandibular rotation in orthognathic surgery.

The effect of post-operative jaw position of an error in locating the true centre of mandibular rotation was evaluated using a computer-simulation model and a mock surgery model. The centre of the condyle serves as a reference point in surgical procedures involving the maxilla. The purpose of this study was to describe the amount of malpositioning of the jaws at surgery due to a discrepancy between a simulated true centre of rotation and the centre of the condyle. The results showed, that a 20 mm error in location of the true centre of rotation could result in a 3 mm horizontal malpositioning of the maxilla.

Soft tissue changes after advancement genioplasty performed as pedicled or free transplants.

The influence of soft tissue attachment in augmentation genioplasty on postoperative soft tissue changes was studied in 25 patients. The soft tissue was completely detached from the advanced genial segment in 14 patients and lingual soft tissue was maintained in 11 patients. The patients were followed for a minimum of 1 year after operation and the soft tissue and bone changes were analysed by measuring linear distances and areas on lateral cephalograms. The result indicated that the soft tissue changes after surgery were significantly different between the two types of graft. In the free grafts there was found to be an increased risk of creating a larger interlabial gap and exposure of the labial surface of mandibular incisors. The higher correlations between hard and soft tissue changes in the pedicled grafts indicated that the predictability is better with this operative technique.

Bone resorption after advancement genioplasty. Pedicled and non-pedicled grafts.

The influence of soft tissue attachment in augmentation genioplasty on the amount of postoperative bone remodelling was studied in 29 patients. The soft tissue was completely detached from the advanced genial segment in 15 patients and the lingual soft tissue was maintained in 14 patients. The advancement of the chin and postoperative bone remodelling was analysed by measuring linear distances and areas on lateral cephalograms. The genial segments with a soft tissue pedicle underwent significantly less resorption than the free grafts (p less than 0.01). The difference in postoperative infection between the two groups (p less than 0.05) indicates that the likelihood of postoperative infection is significantly reduced by maintaining the soft tissue pedicle. Considerably less variation in amount of bone resorption was also observed in the patients with a pedicled graft.

Pitfalls in orthognathic model surgery. The significance of using different reference lines and points during model surgery and operation.

The planning of orthognathic surgery usually involves a simulation of jaw movements in a semi-adjustable articulator. The use of vertical and horizontal references during model surgery and operation have previously been described in great detail. The purpose of the present study was to quantify the errors resulting from using different reference lines and points in model surgery and operation. The results indicate that clinically significant differences between the planned and surgical jaw movement can result from the erroneous transfer of reference lines and points between model surgery and operation. Solutions to some of the problems discussed are suggested.

Marginal bone level after Le Fort I osteotomy.

The object of the study was to assess the effect of Le Fort I osteotomy and maxillary interdental osteotomy on the marginal bone level. Forty patients (25 female, 15 male, mean age 24 years, range 15-46) treated for dentofacial deformities comprised the subjects of the study and underwent Le Fort I osteotomy with or without simultaneous interdental osteotomy. Outcome was measured by marginal bone level measured in radiographs before and 1 year after operation. All patients had good oral hygiene. There was an overall significant mean marginal bone loss of 0.2 mm at surfaces without interdental osteotomy (P = 0.001). When the bone loss of the different types of teeth was considered separately, only those of central incisors (0.5 mm, P = 0.0001) and canines (0.4 mm, P = 0.004) were significant. Interdental osteotomy caused an overall mean marginal bone loss of 0.4 mm, but this was not significantly different from that of teeth without interdental osteotomy (P = 0.07). When the bone loss of different types of teeth after interdental osteotomy was considered separately, the only difference that achieved significance was that of premolars (0.3 mm, P = 0.04). Though there were significant differences, none of them was large enough to have any clinical relevance. Le Fort I osteotomy and interdental osteotomy may only in a few instances cause marginal bone loss of clinical relevance. However, the present study was performed on patients with good oral hygiene. The above conclusions may therefore not be valid for patients who, prior to surgery, already have a compromised marginal bone level.

Photocatalytic degradation of methyl orange by CeO2 and Fe-doped CeO2 films under visible light irradiation.

Undoped CeO2 and 0.50-5.00 mol% Fe-doped CeO2 nanoparticles were prepared by a homogeneous precipitation combined with homogeneous/impreganation method, and applied as photocatalyst films prepared by a doctor blade technique. The superior photocatalytic performances of the Fe-doped CeO2 films, compared with undoped CeO2 films, was ascribed mainly to a decrease in band gap energy and an increase in specific surface area of the material. The presence of Fe(3+) as found from XPS analysis, may act as electron acceptor and/or hole donor, facilitating longer lived charge carrier separation in Fe-doped CeO2 films as confirmed by photoluminescence spectroscopy. The 1.50 mol% Fe-doped CeO2 film was found to be the optimal iron doping concentration for MO degradation in this study.

The global network on dental education: a new vision for IFDEA.

The advent of globalization has changed our perspectives radically. It presents increased understanding of world affairs, new challenges and exciting opportunities. The inequitable distribution and use of finite energy resources and global warming are just two examples of challenges that can only be addressed by concerted international collaboration. Globalization has become an increasingly important influence on dentistry and dental education. The International Federation for Dental Educators and Associations (IFDEA) welcomes the challenges it now faces as a player in a complex multifaceted global community. This report addresses the new circumstances in which IFDEA must operate, taking account of the recommendations made by other working groups. The report reviews the background and evolution of IFDEA and describes the extensive developments that have taken place in IFDEA over the past year with the introductions of a new Constitution and Bylaws overseen by a newly established Board of Directors. These were the consequence of a new mission, goals and objectives for IFDEA. An expanded organization is planned using http://www.IFDEA.org as the primary instrument to facilitate the exchange of knowledge, programmes and expertise between colleagues and federated associations throughout the world, thereby promoting higher standards in oral health through education in low-, middle- and high-income countries of the world. Such aspirations are modified by the reality and enormity of poverty-related global ill health.

Curriculum content, structure and ECTS for European dental schools. Part II: methods of learning and teaching, assessment procedures and performance criteria.

This paper presents a brief context of dental undergraduate curricular structure and content and lays out the Association for Dental Education in Europe's views on requirements and recommendations for learning, teaching and assessment procedures/performance.

Curriculum structure and the European Credit Transfer System for European dental schools: part I.

This paper presents a proposed curriculum structure and system of European Credit Transfer (ECTS) for undergraduate dental schools throughout Europe. It is the result of the work of a Taskforce ('Taskforce II'), appointed by DentEd, a thematic network of European dental schools and the Association for Dental Education in Europe (ADEE). There has been pan-European discussion of the document in draft stages (it was distributed to 200 dental schools) and following amendment, it was agreed formally at the National Assembly of ADEE in Athens, Greece, in September 2005. The main elements of the paper relate to: (i) a description of the framework proposed with relevance to the Bologna recommendations and common directive on recognition for professional qualifications as they apply to Dentistry; (ii) the structure of an undergraduate dental curriculum; (iii) student exchange and ECTS. In addition, the paper presents a series of requirements, guidelines and recommendations for action. ADEE expects that the 'requirements' proposed will be followed by dental schools in Europe, whilst the 'guidelines' and 'recommendations' also provided are open to local interpretation. The paper is also published on the ADEE website.

A comparative evaluation of computer literacy amongst dental educators and students.

A task-oriented questionnaire was designed, aiming to quickly assess competence with the use of computers. The questionnaire consisted of distinct computer-related skills, representing various competences in educational computer use. A total score from 0 to 49 was calculated upon completion of the questionnaire, based on the sum of all the positively identified competences. The questionnaire was distributed to an international group of leading dental educators during the DentEd Global Congress in Prague in 2001 and to a cohort of first year dental students (2001) in the Dental Faculty, University of Malmo, Sweden. Certain attitudes towards the role of information and communication technology (ICT) in dental education were also measured through Visual Analogue Scales in the educator's group. A total of 149 questionnaires were collected from the educators' group and 58 from the dental students. There was no significant difference in the average computer competence score between the two groups. The educators' group average score was 20.7 (SD 9.9) and students' average was 18.1 (SD 8.5). A significant positive correlation (r = 0.395277, P < 0.0001) was found between the competence measured by the questionnaire and the year of graduation in the educators' group. The attitudes towards the role of ICT in dental education amongst the educators were very positive, regardless of their competence with computers, year of graduation or academic position. The results from this study indicate that there is wide diversity in computer competence amongst both students and academic staff. In addition, students' actual competence in the use of computers might not be as high as is often perceived through self-assessment and ordinal scales.

Computer-mediated instructional video: a randomised controlled trial comparing a sequential and a segmented instructional video in surgical hand wash.

BACKGROUND: Video-based instructions for clinical procedures have been used frequently during the preceding decades. AIM: To investigate in a randomised controlled trial the learning effectiveness of fragmented videos vs. the complete sequential video and to analyse the attitudes of the user towards video as a learning aid. MATERIALS AND METHODS: An instructional video on surgical hand wash was produced. The video was available in two different forms in two separate web pages: one as a sequential video and one fragmented into eight short clips. Twenty-eight dental students in the second semester were randomised into an experimental (n = 15) and a control group (n = 13). The experimental group used the fragmented form of the video and the control group watched the complete one. The use of the videos was logged and the students were video taped whilst undertaking a test hand wash. The videos were analysed systematically and blindly by two independent clinicians. The students also performed a written test concerning learning outcome from the videos as well as they answered an attitude questionnaire. RESULTS: The students in the experimental group watched the video significantly longer than the control group. There were no significant differences between the groups with regard to the ratings and scores when performing the hand wash. The experimental group had significantly better results in the written test compared with those of the control group. There was no significant difference between the groups with regard to attitudes towards the use of video for learning, as measured by the Visual Analogue Scales. Most students in both groups expressed satisfaction with the use of video for learning. CONCLUSION: The students demonstrated positive attitudes and acceptable learning outcome from viewing CAL videos as a part of their pre-clinical training. Videos that are part of computer-based learning settings would ideally be presented to the students both as a segmented and as a whole video to give the students the option to choose the form of video which suits the individual student's learning style.

Local CD-ROM in interaction with HTML documents over the Internet.

The internet and computer assisted learning have enhanced the possibilities of providing quality distance learning in dentistry. The use of multimedia material is an essential part of such distance learning courses. However the Internet technology available has limitations regarding transmission of large multimedia files. Therefore especially when addressing undergraduate students or geographically isolated professionals, large download times make distance learning unattractive. This problem was technically solved in a distance learning course for undergraduate students from all over Europe. The present communication describes a method to bypass the problem of transmitting large multimedia files by the use of a specially designed CD-ROM. This CD-ROM was run locally on the students' PC interacting with HTML documents sent over the Internet.

A virtual classroom for undergraduate periodontology: a pilot study.

The Integrated Distributed Learning Environments or virtual classrooms constitute a new promising structure in education of health care personnel. A virtual classroom was developed aiming to teach periodontology to an international group of 28 dental students using a problem-based learning (PBL) approach. The course was web-based and included synchronous and asynchronous communication, on-line libraries and multimedia material. Students were organised in 4 independent groups and each group was appointed a tutor. The results of the study indicate that one of the most positive effects students experienced was competence in using the computer. They also rated highly the use of multimedia for learning of clinical procedures. It was found that web boards and email were too slow to allow group work in the virtual classroom. Real time communication programs were found to be superior for problem discussion and hypothesis formulation. However, email and the web board played a significant role during certain steps of the PBL method. The students expressed a positive attitude for the combined use of network-based learning and problem-based education. Our present experience suggests that distance learning should be organised with a mixture of different media, allowing communication of knowledge and skills between the resources and the students, as well as cooperation between the students. Computer literacy among teachers and students is limited and should be enhanced. Finally, personal contact between the resource persons and the students before the distant learning course commences helps the learning process.