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Concept: Crown

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SUMMARY Fracture resistance of inlays and onlays may be influenced by the quantity of the dental structure removed and the restorative materials used. The purpose of this in vitro study was to evaluate the effects of two different cavity preparation designs and all-ceramic restorative materials on the fracture resistance of the tooth-restoration complex. Fifty mandibular third molar teeth were randomly divided into the following five groups: group 1: intact teeth (control); group 2: inlay preparations, lithium-disilicate glass-ceramic (IPS e.max Press, Ivoclar Vivadent AG, Schaan, Liechtenstein); group 3: inlay preparations, zirconia ceramic (ICE Zirkon, Zirkonzahn SRL, Gais, Italy); group 4: onlay preparations, lithium-disilicate glass-ceramic (IPS e.max Press); and group 5: onlay preparations, zirconia ceramic (ICE Zirkon). The inlay and onlay restorations were adhesively cemented with dual polymerizing resin cement (Variolink II, Ivoclar Vivadent AG). After thermal cycling (5° to 55°C × 5000 cycles), specimens were subjected to a compressive load until fracture at a crosshead speed of 0.5 mm/min. Statistical analyses were performed using one-way analysis of variance and Tukey HSD tests. The fracture strength values were significantly higher in the inlay group (2646.7 ± 360.4) restored with lithium-disilicate glass-ceramic than those of the onlay group (1673.6 ± 677) restored with lithium-disilicate glass-ceramic. The fracture strength values of teeth restored with inlays using zirconia ceramic (2849 ± 328) and onlays with zirconia ceramic (2796.3 ± 337.3) were similar to those of the intact teeth (2905.3 ± 398.8). In the IPS e.max Press groups, as the preparation amount was increased (from inlay to onlay preparation), the fracture resistance was decreased. In the ICE Zirkon ceramic groups, the preparation type did not affect the fracture resistance results.

Concepts: Touring car racing, FIA, Teeth, Analysis of variance, Crown, Dental restoration, CAD/CAM Dentistry, Inlays and onlays

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In dental applications, precision attachments have been used to retain removable partial dentures (RPDs) for several decades. Various types of extracoronal attachments are commonly used in combination with fixed partial dentures and RPDs to achieve retention and stability. Fracture of the framework, fracture of the roots or teeth, and irretrievable decrease of retention are common reasons for a failed attachment-retained RPD. Another complication of metal ceramic crowns with precision attachment is decementation of the crowns. When fixed components of the attachment-retained RPD fail, the traditional treatment approach requires remaking both the fixed and removable components of the attachment-retained RPD. This technique describes retrofitting of a metal ceramic crown to a resilient attachment-retained RPD.

Concepts: The Roots, Crown, Oral hygiene, Dentures, Restorative dentistry, Removable partial denture, Prosthodontology, Precision attachment

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The restoration of endodontically treated teeth involves a difficult decision-making process, especially when it comes to more complex prosthetic rehabilitations. Regarding singletooth restoration, there are high-level requirements for the restorative components and the application of all necessary treatment steps to achieve the final restoration. So when is there a need for a single-crown restoration or when might a composite resin restoration also be sufficient? For the assessment of endodontically treated teeth as abutment teeth for prosthetic restorations, there are no clear guidelines beyond single-tooth restorations. The aim of this article is to compile important aspects of the restoration of endodontically treated single teeth, including more complex prosthetic reconstructions, based on the scientific literature.

Concepts: Composite material, Crown, Dental composite, Composite materials

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Marginal adaptation is essential for the long-term success of dental restorations. Studies comparing the marginal gaps of computer-aided design/computer-aided manufacturing (CAD/CAM) restorations made from conventional and digital impressions are limited.

Concepts: Crown, Dental restoration, Zirconium dioxide

24

The objective of this prospective study was to assess clinical and patient-centered outcomes of esthetic crownn lengthening surgery for the treatment of altered passive eruption.

Concepts: Crown

23

Preclinical dental students must demonstrate aptitude in the preparation of teeth for treatment with several types of fixed dental prostheses. The optimal sequence of instruction and examination of these crown preparations in preclinical fixed prosthodontics is unknown. The aim of this study was to determine if grading scores by faculty and students were affected by changing the sequence of crown type preparations. Practical exams of two successive student cohorts (n=89 in 2014; n=92 in 2015) at one U.S. dental school using three crown preparations (full cast, porcelain fused to metal, and all-ceramic) in different order were analyzed by faculty grades and student self-assessment. All of the models indicated that the sequence in which the crown type preparations were taught did have an effect on the grades. The 2014 cohort had overall higher grades and particularly higher grades for the all-ceramic crown preparations. Evaluation scores were affected by the sequence in which the different crown type preparations were taught and tested. Although the overall results suggested that students may perform better if the all-ceramic crown preparation is taught last, this tendency may differ between years.

Concepts: Crown, Dental restoration, Restorative dentistry, CAD/CAM Dentistry, Bridge, Prosthodontology, Inlays and onlays, Fixed prosthodontics

2

Dental burs are used extensively in dentistry to mechanically prepare tooth structures for restorations (fillings), yet little has been reported on the bur debris left behind in the teeth, and whether it poses potential health risks to patients. Here it is aimed to image dental bur debris under dental fillings, and allude to the potential health hazards that can be caused by this debris when left in direct contact with the biological surroundings, specifically when the debris is made of a non-biocompatible material. Non-destructive micro-computed tomography using the BioMedical Imaging & Therapy facility 05ID-2 beamline at the Canadian Light Source was pursued at 50 keV and at a pixel size of 4 µm to image dental bur fragments under a composite resin dental filling. The bur’s cutting edges that produced the fragment were also chemically analyzed. The technique revealed dental bur fragments of different sizes in different locations on the floor of the prepared surface of the teeth and under the filling, which places them in direct contact with the dentinal tubules and the dentinal fluid circulating within them. Dispersive X-ray spectroscopy elemental analysis of the dental bur edges revealed that the fragments are made of tungsten carbide-cobalt, which is bio-incompatible.

Concepts: Fragment, Teeth, Crown, Dental restoration, Dental composite, Dental materials, Amalgam, Dental amalgam controversy

2

Resin-based dental materials may intraorally release their chemical components and bisphenol A. The New England Children’s Amalgam Trial found that children randomized to amalgam had better psychosocial outcomes than those assigned to composites for posterior tooth restorations. The objective of this study was to examine whether greater exposure to dental composites is associated with psychosocial problems in children.

Concepts: Composite material, Epoxy, Crown, Dental restoration, Dental composite, Dental materials, Composite materials, Amalgam

0

Development of antibacterial dental composites is the ultimate goal to decrease carious disease occurrence and increase the restoration longevity. For this purpose, the quaternary ammonium dimethyl-hexadecyl-methacryloxyethyl-ammonium iodide (DHMAI) and the methacryloyloxyethylphosphorylcholine (MPC) have been incorporated in experimental methacrylate-based composite resins. This aims to first investigate the effect of each alone and then their combined effect.

Concepts: Effectiveness, Composite material, Ammonium, Crown, Dental composite, Dental materials, Composite materials, Amalgam

0

Radiographs aid in clinically determining crown fit, specifically interproximal margins where tactile and visual methods may be limited. However, investigations of the utility of digital radiographs as a tool for evaluating the marginal openings of ceramic crowns are lacking.

Concepts: Medical imaging, Radiography, Crown