Microtensile Bond Strength Between Resin-Matrix CAD/CAM Ceramics and Resin Cement after Various Surface Modifications and Artificial Aging.

PURPOSE: To evaluate the effect of different surface modification methods on the microtensile bond strength (µTBS) of four resin-matrix CAD/CAM ceramics after artificial aging. MATERIALS AND METHODS: Specimens of four CAD/CAM materials (Shofu Block HC, Lava Ultimate, Brilliant Crios, and Vita Enamic) were prepared and divided into four groups. Each group received one of the following treatments: group 1 (INT): no surface modification; group 2: sandblasting with 29-µm Al2O3 particles (SB); group 3: hydrofluoric acid etching (9%) + silane (HF+Si); group 4: sandblasting with 30-µm particles of the CoJet system (CJ). The specimens of each group were luted together in pairs using resin cement (RelyX Ultimate). After one week of water storage (37°C), the sandwich specimens were sectioned into rectangular microspecimens and half of them were immediately subjected to µTBS testing, while the other half was tested after six months. Data were statistically analyzed using FFANOVA including the factors of material, treatment, and storage time, with α = 0.05. RESULTS: After one week, the lowest µTBS was observed for INT, while the highest was found for either mechanical (SB and CJ) or chemical (HF+Si) treatments (p < 0.05). After six months, a significant decrease in µTBS was observed depending on treatment (p < 0.05), while artificial aging significantly influenced the µTBS of all experimental groups (p < 0.05). During the two storage periods, the failure type was mainly interfacial and was associated with the type of surface modification. CONCLUSION: After artificial aging, the µTBS appeared to depend on srface modification, while the parameter "material" did not influence the results. Consequently, adhesive strategies should be oriented towards surface modification techniques.

Evaluation of the Surface Characteristics of Dental CAD/CAM Materials after Different Surface Treatments.

Computer-aided design/computer-aided manufacturing (CAD/CAM) technology was developed to ensure the sufficient strength of tooth restorations, to improve esthetic restorations with a natural appearance and to make the techniques easier, faster and more accurate. In the view of the limited research on the surface treatments of the CAD/CAM materials and the need to evaluate the ideal surface characteristics of a material to achieve the best adhesion to tooth tissues, this study aimed to investigate the surface roughness and morphology of four different CAD/CAM materials using four different surface treatments. The CAD/CAM materials used in this study were three composites (Shofu Block HC, Lava Ultimate and Brilliant Crios) and a hybrid ceramic (Enamic). The surface of the specimens of each material received one of the following treatments: no surface treatment, sandblasting with 29 µm Al2O3 particles, 9% hydrofluoric acid etching and silane application, and the tribochemical method using CoJet System. Surface roughness was evaluated using optical profilometry, and surface morphology was observed by means of scanning electron microscopy. All surface treatments resulted in higher surface roughness values compared to the control group. Different treatments affected the surface properties of the materials, presumably due to discrepancies in their composition and structure.

Fracture strength of minimally prepared resin bonded CEREC inlays.

PURPOSE: This study compared the structural integrity and fracture mode of teeth restored with traditionally and minimally prepared resin-bonded CAD/CAM inlays fabricated from the same material. METHODS: Forty intact maxillary premolars were used and divided into four groups. Two groups were prepared according to a traditional inlay preparation design (2.0 mm occlusal reduction, a 1.5 mm wide proximal box and divergent walls) and two groups were prepared according to a newly proposed minimal preparation design (round shaped cavity with 1.0 mm occlusal reduction, a U-shaped proximal box 1.0 mm wide and parallel walls). Two restorative systems were tested: a composite system comprised of Paradigm MZ100 (3M ESPE) blocks and RelyX Unicem (3M ESPE) resin cement and a ceramic system comprised of ProCAD blocks (Ivoclar-Vivadent) and Variolink II (Ivoclar-Vivadent) resin cement. The inlays were cemented according to the manufacturers' instructions. Each specimen was loaded axially to its occlusal surface at a crosshead speed of 0.5 mm/minute in a universal testing machine until fracture. The fracture load data were analyzed using ANOVA, comparing inlays of the same restorative material. Also, the mode of fracture of the inlays was recorded and analyzed using a non-parametric test (Kruskal-Wallis). RESULTS: In the composite system case, the mean fracture load and SD were 1322 N (+/- 445) for the traditional inlays and 1511 N (+/- 395) for the minimal inlays, while in the ceramic system case, those values were 1135N (+/- 450) for the traditional inlays and 1761 N (+/- 494) for the minimal inlays. Statistical analysis of the results showed that there was no statistically significant difference between the two designs for the composite system, while for the ceramic system, the minimally prepared teeth showed higher mean fracture strength. Non-parametric analysis (Kruskal-Wallis) of the mode of fracture showed that there was no statistically significant difference between traditionally and minimally prepared inlays for both systems (p > .05). CONCLUSIONS: Under the conditions of this experimental study, only the ceramic inlays, when prepared with a minimal preparation design, demonstrated a higher fracture strength as compared to the traditionally prepared teeth. Use of the proposed minimal preparation design did not compromise the immediate post-operative structural integrity of teeth restored either with resin composite or ceramic inlays.

A blended learning course taught to different groups of learners in a dental school: follow-up evaluation.

This article reports the results of a follow-up study conducted to investigate students' perceptions about a blended learning health informatics course that combined online and traditional classroom instruction. The course is taught to five different groups of students at the School of Clinical Dentistry of the University of Sheffield each academic year: first-, third-, and fourth-year dental students, dental hygiene and therapy students, and postgraduate dental students. The goal of the study was to determine the impact of the modifications made to the course after the first year of implementation. To accomplish this goal, students' perceptions of this blended learning course were compared after the first and second implementations. The methodology used for this study was action research. The data were collected using three processes: questionnaires were used to collect contextual data from the students taking the course; a student-led, nominal group technique was used to collect group data from the participants; and a non-participant observer technique was used to record the context in which certain group and individual behaviors occurred. Depending on group assignment, between 41.5 and 91.5 percent of students believed that the blended-learning course had added to their skills. The online learning environment was perceived as a useful resource by 75 percent of students in four of the five student groups, but only 45 percent of the fourth-year dental students indicated it was a useful resource. The perceived lack of sufficient online support material was one of the main concerns of the students at the nominal group evaluation sessions. The non-participant observer technique identified different engagement levels among the student groups. Discernible differences were identified, with improvement in some areas and a decline in others compared to a previous evaluation. The change in the delivery method influenced the students' comprehension of the material negatively and the learning environment positively, but did not influence online collaboration among students.

Evaluating a blended-learning course taught to different groups of learners in a dental school.

The purpose of this study was to present and evaluate a blended-learning course developed for undergraduate (B.D.S.), postgraduate, and diploma (hygiene and therapy) students at the University of Sheffield School of Clinical Dentistry. Blended learning is the integration of classroom face-to-face learning with online learning. The overall methodology used for this study was action research. The data were collected using three processes: questionnaires to collect contextual data from the students taking the course; a student-led, nominal group technique to collect group data from the participants; and a non-participant observer technique to record the context in which certain group and individual behaviors occurred. The online component of the course was accepted as a valuable resource by 65 percent of those responding. While online information-sharing occurred (31 percent of the students posted in forums), there was no evidence of online collaboration, with only 8 percent replying to forum postings. Accessibility of the online environment was one of the main concerns of the students at the nominal group sessions. Differences regarding overall engagement with the course between the student groups (years) were observed during the sessions. The majority of the students were satisfied with the Information and Communication Technologies (ICT) course. No statistically significant differences between males and females were found, but there were differences between different student cohorts (year groups).