Ceramic Reconstruction (CEREC®) - an Ingenious Concept in Restorative Dentistry?

CEREC is a computerized method to produce ceramic reconstructions chairside. It had been developed in the Eighties by Professor Dr.med.dent. Werner H. Mörmann und Dr. sc. techn. El. Ing Marco Brandestini at the University of Zürich in Switzerland. The most actual version in the CEREC-Series is CEREC 3. It is a robot in which CAD/CAM-techniques are applied and prefabricated dental materials (ceramics and polymers) are used. Target group are primarily dentists; since CEREC InLab is on the market dental technicians also. According to the general CEREC-principle, an optical impression is used as “worksheet” to construct every restoration in/on any single tooth - from a simple class I-or class V-restoration to any partial or full crown - in a very simple but sophisticated manner: The CEREC-user only has to design the so-called “bottom line”, all other constructions are generated automatically. Besides that every modification may be introduced manually. The milling process is fully automatic. The restorations are adapted to the tooth structures by modern adhesive techniques. From survival analyses it could be shown, for example by the study of Reis and Walther (2000), that from 1,010 inlays which were applied to the posterior teeth in 299 patients in a routine dental practice, after 9 -12 years the probability of success (calculated by Kaplan-Meier Analysis) decreased to 90% after 10 years (s = .018) and 85% after 11.8 years with no further loss until the 12-year termination point. Measuring parameter as inlay fracture, cusp fracture, new proximal lesion, recurrent caries, persistent hypersensitivity, endodontic complications, prosthetic and unknown causes (with replacement alio loco) respectively showed no significant difference in clinical success between maxillary and mandibulare teeth, neither between the sizes and the outlines of the restoration. However, premolars rated better than molars, vital teeth better than non-vital teeth. The application of dental adhesive techniques increased the probability of success. Only 81 (8%) failures were recorded, mainly due to fractures of the ceramic and tooth structure (50%). In summary, CEREC using simple but sophisticated hard- and software in combination with trustworthy modern dental materials is an ingenious and clinical reliable concept in restorative dentistry with the potency of an enormous impact at high quality dentistry and dental education. Indeed, CEREC is an ingenious concept in restorative dentistry

Effect of worksheet scaffolds on student learning in problem-based learning

The purpose of this study was to investigate the effect of worksheets as a scaffolding tool on students’ learning achievement in a problem-based learning (PBL) environment. Seventeen PBL classes (N = 241) were randomly assigned to two experimental groups—one with a worksheet provided and the other without. Students’ learning of the topic at hand was evaluated by comparing results from pre- and post-lesson concept recall tests. We also obtained information about students’ perceptions of factors impacting their learning using a Learning Impact Questionnaire. The data was analyzed by means of analyses of variance. Results of the study indicated that there was no statistically significant difference between the levels of understanding for both groups of students. In addition, survey results revealed that the strongest factor perceived by students to impact their learning in a PBL context is the tutor followed by team and class dynamics, while the influence of the worksheet was rated lowest. These findings suggest that scaffolds such as worksheets may not play a significant role in enhancing students’ learning within the social constructivist framework of problem-based learning. On the other hand, the importance of the role of tutor and collaborative small group learning which are key features of PBL is reinforced

Elucidation of the Structure of Solanoeclepin A, a Natural Hatching Factor of Potato and Tomato Cyst Nematodes, by Single-crystal X-ray Diffraction

Potato crops can be severely damaged by potato cyst nematodes Globodera rostochiensis and Globodera pallida, nematodes highly specific to potatoes and some other Solanaceae. Hatching of juveniles is controlled by agents excreted by the roots of some Solanaceae species. Over seventy years much effort has been expended by many groups to isolate these agents and to determine their structures. However, all attempts have failed. We report here the structure determination of a hatching factor excreted from potato and tomato roots. The hatching factor bears some resemblance to Glycinoeclepins as found by Masamune et al.2-5 and is hence designated as Solanoeclepin A.1 C27H30O9.3H2O, Mr = 498.5, monoclinic, P21, a = 11.289(2), b = 20.644(4), c = 11.632(12) Å, β = 90.81(4), V = 2711(3) Å3, Z = 4, Dx = 1.35 g cm–3, λ(Cu-K&alpha ) = 1.5418 Å, μ(Cu-Kα ) = 9.0 cm–1, F(000) = 1176, –60 °C. Final R = 0.117 for 3721 observed reflections

The relationships between problem characteristics, achievement-related behaviors, and academic achievement in problem-based learning

This study investigated the influence of five problem characteristics on students' achievement-related classroom behaviors and academic achievement. Data from 5,949 polytechnic students in PBL curricula across 170 courses were analyzed by means of path analysis. The five problem characteristics were: (1) problem clarity, (2) problem familiarity, (3) the extent to which the problem stimulated group discussion, (4) self-study, and (5) identification of learning goals. The results showed that problem clarity led to more group discussion, identification of learning goals, and self-study than problem familiarity. On the other hand, problem familiarity had a stronger and direct impact on academic achievement

Quality assurance, benchmarking, assessment and mutual international recognition of qualifications

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