BACKGROUND:Haptics-enhanced virtual reality (VR-haptic) simulation in dental education has evolved considerably during the past decade, representing a promising resource of simulation-based training opportunities to support conventional practice. We aim to summarize current literature on the applications of VR-haptics in learning, practicing, and teaching dental education. METHODS:A literature search was performed using PubMed, focusing on research articles published between January 2010 and January 2024. Out of the 667 articles that matched the search terms (dentistry, education, haptic, teaching, training, virtual reality), 105 were screened, and 42 were eligible for full-text reading and utilization. Findings from an ongoing educator survey on the use of VR-haptics in dental education have also been provided. RESULTS:VR-haptic simulation has been shown to have a supportive role in dental simulation practice. Despite training within a digital world, hand skill transfer to the real world has been demonstrated, which affords educators more flexibility in how to train their students before and during traditional preclinical and clinical practical education. The individualized VR-haptic training and feedback help students in mastering essential working techniques, while also increasing engagement and motivation. CONCLUSIONS:VR-haptics-supported dental education can help students effectively address challenges during their preclinical and clinical training, as well as in their subsequent careers, and it may help mitigate some weaknesses of the current educational system. Validation is a key factor for the acceptance of VR-haptic simulators; thus, further research and verification are needed before VR-haptics could be considered a primary hand skill development method of learning in dental education. VR-haptic simulation may in the future be used as an assessment tool for the students' and clinicians' credentialing process.

•Primary teeth as a biomarker for past chemical exposure in critical developmental periods, both pre-and postnatally.•A total of 18 different toxic and essential trace elements detected in teeth using LA-ICP-MS.•Using primary teeth to understand the precise timing of toxic exposures on vulnerable and susceptible infants and children.•Decrease exposure during critical developmental windows and prevent development of disease.

Hovedbudskap Simulering ved hjelp av virtuell virkelighet («Virtual Realty simulators» VRS) er godt egnet som læringsverktøy i flere odontologiske prosedyrer og kan gjøre overgangen fra preklinisk til klinisk undervisning lettere. Simulering i odontologisk undervisning kan gi økt pasientsikkerhet ved at studentene blir øvet i ulike behandlingssituasjoner på forhånd. Det er ingen VRS-systemer i dag som kan erstatte alle aspekter ved preklinisk ferdighetstrening, men den hurtige teknologisk utviklingen gjør VRS stadig mer anvendelig og klinisk relevant.

Objectives: The aim of this retrieval study was to analyze the fracture features and identify the fracture origin of zirconia-based single crowns that failed during clinical use. Methods: Thirty-five fractured single crowns were retrieved from dental practices (bi-layered, n = 15; monolithic, n = 20). These were analyzed according to fractographic procedures by optical and scanning electron microscopy to identify fracture patterns and fracture origins. The fracture origins were closely examined. The crown margin thickness and axial wall height were measured. Results: Three types of failure modes were observed: total fractures, marginal semilunar fractures, and incisal chippings. Most of the crowns (23) had fracture origins at the crown margin and seven of them had defects in the fracture origin area. The exact fracture origin was not possible to identify due to missing parts in four crowns. The crown wall thickness was 20% thinner and wall height 30% shorter in the fracture origin area compared to the opposite side. Conclusions: The findings in this study show that fractography can reveal fracture origins and fracture modes of both monolithic and bi-layered dental zirconia. The findings indicate that the crown margin on the shortest axial wall is the most common fracture origin site. Clinical significance: Crown design factors such as material thickness at the margin, axial wall height and prep-aration type affects the risk of fracture. It is important to ensure that the crown margins are even and flawless

Objective. Monolithic zirconia crowns have become a viable alternative to conventional layered restorations. The aim of this study was to evaluate whether the taper, and thus wall thickness, of the abutment or pre-defined cement space affect the fracture resistance or fracture mode of monolithic zirconia crowns. Methods. A model tooth was prepared with a taper of 15 degrees and a shallow circumferential chamfer preparation (0.5 mm). Two additional models were made based on the master model with a taper of 10 degrees and 30 degrees using computer-aided design software. Twenty monolithic 3rd generation translucent zirconia crowns were produced for each model with pre-defined cement space set to either 30 mu m or 60 mu m (n = 60). The estimated cement thickness was assessed by the replica method. The cemented crowns were loaded centrally in the occlusal fossa at 0.5 mm/min until fracture. Fractographic analyses were performed on all fractured crowns. Results. The load at fracture was statistically significant different between the groups (p < 0.05). The crowns with 30 degrees taper fractured at lower loads than those with 10 degrees and 15 degrees taper, regardless of the cement space (p < 0.05). The fracture origin for 47/60 crowns (78%) was in the cervical area, close to the top of the curvature in the mesial or distal crown margin. The remaining fractures started at the internal surface of the occlusal area and propagated cervically. Significance. The fracture resistance of the monolithic zirconia crowns was lower for crowns with very large taper compared to 10 and 15 degrees taper even though the crown walls were thicker. (C) 2021 The Author(s). Published by Elsevier Inc. on behalf of The Academy of Dental Materials.

Objectve.Several pre-cementation procedures have been advocated to enhance adhesion between zirconia and resin-based cement.There is, however, limited documentation on how these pre-treatments affect the strength of zirconia crowns as most tests are performed on discs or bars.The aim was to assess the effect of pre-cementation procedures on fracture mode, fracture strength and cement retention on zirconia.Methods.Two dental zirconia materials with different yttria content were assessed (<4 and>5 mol%).Both discs (n = 45) and crown-shaped specimens (n = 30) of the two materials were pretreated with either air-abrasion or hot-etching with KHF 2 and compared with untreated controls with regards to surface roughness, crystallography, wettability, cement adhesion and fracture strength.Results and Significance.Air-abrasion improves adhesion and strength of zirconia with moderate yttria content (<4 mol%).Acid etching with heated KHF 2 showed the best effect on strength and cement retention on zirconia with higher yttria content (>5 mol%).Application of KHF 2 was, however, complicated on crown-shaped specimens.Pre-treatment and cementation protocols should be optimized for different dental zirconias to improve both strength and retention.

AIM:The aim of this study was to evaluate the effect of cement on the fracture load of monolithic zirconia crowns with different yttria content (3 and 5 mol%).METHODS:A total of 62 monolithic zirconia crowns, 40 3Y-zirconia crowns (Prettau® Zirconia, Zirkonzahn) and 22 5Y-zirconia crowns (Prettau® 4 Anterior®, Zirkonzahn) were produced to a shallow chamfer molar preparation. The 3Y-crowns were divided into four groups and attached to composite abutment duplicates (SDR® flow+, Dentsply DeTrey GmbH) using the following four cementation techniques; (1) Self-adhesive resin-based cement, (2) Pre-treatment with air-abrasion and self-adhesive resin-based cement, (3) Zinc phosphate cement, (4) Glass-ionomer cement. The 5Y-crowns were divided into two groups and attached to the duplicates with; (1) Self-adhesive resin-based cement, or (2) Air-abrasion pre-treatment and self-adhesive resin-based cement. All crowns were loaded axially (0.5 mm/min) on the occlusal surface until fracture occurred.RESULTS:Among the 3Y-zirconia groups, the zinc phosphate cement group fractured at lower loads compared to the resin-based cement groups, with and without air-abrasion, (p < .012). Among the 5Y-groups the air-abraded crowns fractured at statistically significant lower loads compared to the untreated crowns (p < .028). Load at fracture values were significantly different between the two zirconia materials (p < .001), with fracture loads ranging from 3873 to 7500 N in the 3Y-groups, and 2100 to 4948 N in the 5Y-groups.CONCLUSIONS:Resin-based cementation increased the fracture load compared to non-adhesive cementation. The 3Y-crowns fractured at almost twice the loads of the 5Y-crowns. Pre-treatment with air abrasion reduced the strength of the 5Y-crowns only, showing the importance of differentiating the treatment of the two materials.

HovedbudskapIngen enkelt sement på markedet i dag dekker alle indikasjonsområder.Riktig diagnostikk og kunnskap om interaksjoner mellom forskjellige protesematerialer, sement- og tannvevstyper er forutsetninger for å velge riktig sement i en gitt behandlingssituasjon.Kliniske momenter som ligger til grunn for valg av riktig sement er, i kronologisk rekkefølge, vurdering av resttannsubstans, valg av restaurering og utforming av tannprepareringen, valg av restaureringsmateriale (metall, keram, polymer), en egnet overflatebehandling av resttannvev og protese og en vurdering av passform og bredde på sementspalten.Det er viktig å kjenne til ulike egenskaper ved sementer og å overholde korrekte arbeidsprosedyrer i henhold til faglige normer og produsentenes bruksanvisninger.

PURPOSE:High-translucent dental zirconia has been introduced as a suitable material for anterior monolithic restorations. The material composition differs from traditional 3Y-TZP both with regard to yttria content and grain size. Little is known regarding how these alterations affect other properties than translucency and flexural strength. The aim of this study was to evaluate the crack propagation resistance and hardness of dental zirconias with different yttria content and different manufacturing methods.MATERIALS AND METHODS:Measurement of hardness (HV2/5) and crack propagation from the indents (damage tolerance) was performed using a hardness tester(Vicker) on a flat polished surface of five crowns from six different commercial dental zirconias; one hard-machined 3Y-TZP, three soft-machined 3-5% yttria-stabilized zirconias and two soft-machined zirconias with ≥5% yttria content.RESULTS:Damage control varied greatly among dental zirconias with different compositions and fabrication methods. The hard-machined 3Y-TZP had better crack propagation resistance than soft-machined, 3-5% yttria-stabilized zirconias.CONSLUSION:The ultra-translucent zirconias with ≥5% yttria content had the lowest crack propagation resistance. Hardness is not a suitable indicator for damage tolerance.

Hovedbudskap Covid-19 pandemien utløste stor grad av bekymring for studieprogresjon og læringsutbytte blant studentene. De fleste studentene opplevde mindre læringsutbytte av digital undervisning sammenlignet med klinisk tjeneste, men opplevde samme eller bedre læringsutbytte av digitale forelesninger sammenlignet med tradisjonelle forelesninger. Studentene ønsket en videreføring av digital teoriundervisning etter covid-19 pandemien.

Higher yttria content enhances the translucency and appearance of dental zirconia materials. Alterations in material composition also affect mechanical properties. The aim of this study was to compare the fracture load after artificial short‐term aging of monolithic, full‐contour zirconia crowns with different amounts of yttria‐stabilization. Sixty crowns (thirty super high translucent crowns (5Y‐Z) and thirty high translucent crowns (3Y‐Z)) were produced to fit a model of a premolar with a shallow chamfer preparation. The crowns were cemented with self‐adhesive resin cement on composite abutments. For each zirconia type, three groups of crowns (n = 10) were allocated to: (i) cyclic loading (200 N, 1 Hz, 30,000 cycles), (ii) hydrothermal aging (3 × 20 min, 134°C 3.2 bar), or (iii) no treatment (control). Surviving crowns from the aging process were quasistatically loaded until fracture. The 3Y‐Z crowns had statistically significantly higher fracture values (3,449 N) than the 5Y‐Z crowns (1,938 N). The aging procedures did not affect load at fracture. Fractographic analysis showed that fractures started either at the crown margin or at the occlusal intaglio area. Higher yttria content leads to a reduction in material strength and damage tolerance, and this should be reflected in recommendations for clinical use.

Additive manufacturing (AM) of ceramics, particularly of zirconia, is becoming of increasing interest due to the substantial freedom available in the design and fabrication process. However, due to the novelty of the field and the challenges associated with printing dense bulk ceramics suitable for structural applications, thorough investigations that explore the effects of printing on the mechanical performance are limited. Previous work has identified anisotropy in the mechanical properties and attributed it to the layer-by-layer deposition. However, substantiated fractographic evidence detailing the origins and effects of layer lines on the probability of failure are limited. This study investigates the mechanical properties of a dense (>99 %TD), partially stabilized zirconia fabricated by a digital light projection printing method following ASTM standards. Hardness and strength evaluations were conducted, followed by a Weibull analysis and fractography. The investigation entailed five unique build directions and a conventionally manufactured reference material that was used as a control. Although the strengths were comparable to the reference material for some orientations, fracture frequently initiated at layer lines and related defects in all orientations. The findings indicate that if the layer lines can be prevented or engineered, the strength of vat printed ceramics can be improved substantially.

Objectives. This study investigated the effects of tungsten-carbide grinding on the surface characteristics and mechanical strength of dental 3 mol% yttria-stabilized zirconia (3Y-TZP). Methods. Two types of tungsten-carbide burs (TC), 6-blade (TC1) and 8-blade (TC2) were used to grind 3Y-TZP, in a dental air-turbine handpiece with water-cooling and were also subjected to air-particle abrasion (APA): TC1 + APA and TC2 + APA; and rubber polishing (RP): TC1 + RP and TC2 + RP; one group received only rubber-polishing RP. The control group received no treatment. Surface characterization was examined by surface roughness (R-a) and atomic force microscopy. Specimens were also observed with scanning electron microscopy (SEM) and X-ray-diffraction (XRD) for microstructure and crystalline phases. A piston-on-three-balls biaxial-flexural strength (BFS) test was performed with 15 samples-per-group and the broken specimen were observed under SEM to investigate the fracture origin pattern. Oneway ANOVA, Kruskal-Wallis test and Weibull analysis were performed at alpha = 0.05. Results. Groups TC1 and TC2 had the lowest mean BFS (p < 0.05) with up to 74 % reduction in strength. APA and RP both significantly increased the mean BFS after tungsten-carbide grinding but was still less than the control (p < 0.05). Compared to the control, the mean BFS was significantly reduced for all groups except for the RP group (p < 0.05). APA and rubber-polishing following TC2 grinding had significant higher mean BFS than those following TC1 grinding respectively (p < 0.05). SEM revealed distinct micro-cracks after tungsten-carbide grinding. Significance. Tungsten-carbide burs (6- and 8-blade) are not recommended for zirconia grinding due to the significant reduction of biaxial-flexural strength and observed microstructural surface and subsurface damage. (C) 2020 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

INTRODUCTION:Although the strength and toughness of dentin decrease with age, no study has explored if restorative treatments are a contributing factor. METHODS:Multiple extracted teeth were obtained from randomly selected donors and categorized according to donor age and prior root canal treatment. The microstructure and chemical composition of radicular dentin were evaluated using scanning electron microscopy and Raman spectroscopy, respectively, and the strength was evaluated in 4-point flexure to failure. Data were compared using the Student t test. RESULTS:Dentin from the root canal-restored teeth exhibited significantly lower strength (P < .05) than tissue from age- and donor-matched unrestored tooth pairs. Although there was no significant difference in the mineral-to-collagen ratio between the 2 groups, dentin obtained from the root canal-treated teeth exhibited more extensive collagen cross-linking and lower tubule occlusion ratios than the unrestored tooth pairs. CONCLUSIONS:There is a decrease in the strength of radicular dentin with aging, but prior root canal treatment increases the extent of degradation.

Abstract Purpose: The aim of this study was to evaluate the effect of wall thickness on load at fracture of monolithic zirconia dental crowns after aging. Materials and Methods: Seventy translucent monolithic zirconia crowns (DD Bio ZX2, Dental Direkt GmbH) were produced to fit a second upper premolar preparation with a circumferential shallow chamfer. Thirty crowns had a minimum wall thickness of 0.4 mm and 40 had 0.8 mm. TwentyAQ4 of the thick-walled crowns were glazed. The remaining crowns were polished. Ten crowns from each group functioned as controls, while the remaining were subjected to an aging procedure of alternation between dynamic loading and autoclaving. The surviving crowns were assessed for margin damages and surface wear before beeing subjected to quasi-static loading until fracture. All fractures were analyzed by fractographic methods. Results: There were statistically significant differences among the test groups concerning the effects of aging and surface wear. All thick-walled and eight of the thin-walled crowns survived the aging procedure. All fracture origins both from dynamic and quasi-static loading were located in the cervical margin with crack propagation corresponding to cervical hoop stress as observed in clinical failures. Conclusions: Thin-walled translucent monolithic zirconia crowns were more affected by the aging procedure than thick-walled crowns.

BACKGROUND:Promising results of initial clinical trials with yttria-stabilized zirconia have led to more extensive use of zirconia in dental implant superstructures. The applications have extended to abutments and complex individually designed crown-abutment one-piece structures. Little is known about their clinical success and the primary cause of failures. PURPOSE:The aim of this study was to identify the cause of fracture of retrieved implant-retained one-piece prostheses that failed during clinical use. METHODS:Nine fractured restorations were analyzed with fractographic methods and their fracture origins were identified. RESULTS:All but two of the fractures originated in an area of tight contact between the implant or titanium screw and the abutment base. Results of the evaluation showed that zirconia-based implant restorations with very thin walls in the region connecting the prosthesis to the implant are vulnerable to damage from the screw retaining process and fracture from non-axial loads. Two restorations failed due to veneer fractures. SIGNIFICANCE:The findings suggest that large crowns on narrow implants or implants with internal fixation should preferably not be made with zirconia abutments, or that a new design approach should be considered.

Kravene til manuelle ferdigheter, nøyaktighet, taktilitet og romforståelse er fremdeles essensielle for tannlegestudenter, men læringsmetodene og de tekniske hjelpemidlene er i stadig endring. Digitale læringsmidler, som for eksempel virtuelle virkelighetssimulatorer (VRS), er svært aktuelle. Hvordan en best skal implementere ny teknologi, holdninger og forventninger blant instruktører og studenter, har man per i dag begrenset kjennskap til. Det samme gjelder læringsmidlenes pedagogiske effekt. Hensikten med studien var å evaluere VRS (Moog Simodont® Dental Trainer) som et pedagogisk verktøy i odontologisk undervisningssammenheng.

Two zirconia-based 4-unit restorations intended for the same patient fractured during the veneering process even though the prolonged cooling protocol recommended by the manufacturers was used. Fractographic analyses revealed that both restorations fractured as a result of thermal shock, but at different times during production. Further investigation is necessary to optimize the firing protocols for large zirconia-based restorations and avoid fracture due to thermal shock.