Indistinguishable telecom band photons from a single Er ion in the solid state.

Atomic defects in the solid state are a key component of quantum repeater networks for long-distance quantum communication1. Recently, there has been significant interest in rare earth ions2-4, in particular Er3+ for its telecom band optical transition5-7 that allows long-distance transmission in optical fibres. However, the development of repeater nodes based on rare earth ions has been hampered by optical spectral diffusion, precluding indistinguishable single-photon generation. Here, we implant Er3+ into CaWO4, a material that combines a non-polar site symmetry, low decoherence from nuclear spins8 and is free of background rare earth ions, to realize significantly reduced optical spectral diffusion. For shallow implanted ions coupled to nanophotonic cavities with large Purcell factor, we observe single-scan optical linewidths of 150 kHz and long-term spectral diffusion of 63 kHz, both close to the Purcell-enhanced radiative linewidth of 21 kHz. This enables the observation of Hong-Ou-Mandel interference9 between successively emitted photons with a visibility of V = 80(4)%, measured after a 36 km delay line. We also observe spin relaxation times T1,s = 3.7 s and T2,s > 200 µs, with the latter limited by paramagnetic impurities in the crystal instead of nuclear spins. This represents a notable step towards the construction of telecom band quantum repeater networks with single Er3+ ions.

Optically Unstable Phase from Ion-Ion Interactions in an Erbium-Doped Crystal.

Optical many-body systems naturally possess strong light-matter interactions and are thus of central importance for photonic applications. However, these applications are so far limited within the regime of intrinsic dynamically stable phases, and the possibility of unstable phases remains unidentified. Here we experimentally revealed a new dynamical phase of intrinsic optical instability by using a continuous-wave laser to drive an erbium-doped crystal. The transmission through the sample became unstable for intense laser inputs, and transient net gain was observed if the light passed the sample twice. The phase transition, between states in and out of a dynamical equilibrium, was induced by the dipole-dipole interactions between nearby erbium ions.

A simple experimental method for measuring the thermal sensitivity of single-mode fibers.

We present a simple technique to experimentally determine the optical-path length change with temperature for optical single-mode fibers. Standard single-mode fibers act as natural low-finesse cavities, with the Fresnel reflection of the straight cleaved surfaces being ∼3%, for the laser light coupled to them. By measuring the intensity variations due to interference of light reflected from the fiber front and end surfaces, while ramping the ambient temperature, the thermal sensitivity of the optical-path length of the fiber can be derived. Light was generated by a narrow linewidth, low drift laser. With our fairly short test fibers, we found that it was possible to reach a relative precision of the temperature sensitivity, compared to a reference fiber, on the 0.4%-2% scale and an absolute precision of 2%-5%, with the potential to improve both by an order of magnitude. The results for single-acrylate, dual-acrylate, and copper- and aluminum-coated fibers are presented. Values are compared with analytic models and results from a finite element method simulation. With the aid of these measurements, a simple fiber-interferometer, which is insensitive to thermal drifts, could be constructed.

Prosthetic protocols in implant-based oral rehabilitations: A systematic review on the clinical outcome of monolithic all-ceramic single- and multi-unit prostheses.

AIM: The purpose of this systematic review was to assess the clinical performance of implant-supported monolithic all-ceramic single- and multi-unit restorations. MATERIALS AND METHODS: The electronic databases of MEDLINE via PubMed, the Cochrane Library (CENTRAL) and EMBASE were searched for clinical studies on monolithic all-ceramic single and multi-unit implant-supported fixed dental prostheses. Human studies with a mean follow-up of at least 2 years and published in English or German language peer-reviewed journals up until August 2016 were included. Two independent examiners conducted the literature search and review process. RESULTS: The search resulted in 2510 titles and of these, 57 studies were selected for full-text evaluation. Three studies were included on the basis of the pre-determined criteria. Two articles reported on monolithic lithium disilicate implant-supported single crowns (SC) and revealed a survival rate of 97,8 and 100% after 3 years. One study investigated implant- supported monolithic zirconia SCs and fixed partial dentures (FPD) and showed a survival rate of 100% after 5 years. No studies could be identified on the clinical performance of monolithic resin matrix ceramic restorations. Clinical studies are lacking on the long-term outcome of implant-supported monolithic all-ceramic single- and multi-unit restorations. CONCLUSIONS: Preliminary clinical data indicate high short-term survival for implant-supported monolithic lithium disilicate and zirconia single- and multi-unit restorations. Randomised clinical studies and observations with a longer duration are necessary to validate the broad application of this therapy. Conflict-of-interest statement: The authors declare no conflict of interest.

Key Parameters of Hybrid Materials for CAD/CAM-Based Restorative Dentistry.

Hybrid materials are a recent addition to the dental armamentarium for computer-assisted design/ computer-assisted manufacturing (CAD/CAM)-based restorative dentistry. They are intended to provide dentists with the capability of restoring single teeth in one appointment with a material that emulates the structure and physical properties of natural teeth. This article aims to provide an overview of currently available hybrid materials and offer the reader further understanding of their key clinical parameters and possible limitations.

Adhesive Bonding to Hybrid Materials: An Overview of Materials and Recommendations.

Recently, hybrid materials have been introduced to the dental market. Together with computer-assisted design/computer-assisted manufacturing (CAD/CAM) composite resins, they form a new class of dental CAD/CAM materials that combine the positive effects of ceramics and composites. As bonding is essential for their clinical longevity, it is crucial to have a good understanding of their material properties and cementation protocols. This review offers clinicians an overview of available hybrid materials and recommendations for their respective adhesive placements.

Comprehensive Spectroscopic Determination of the Crystal Field Splitting in an Erbium Single-Ion Magnet.

The electronic structure of a novel lanthanide-based single-ion magnet, {C(NH2)3}5[Er(CO3)4]·11H2O, was comprehensively studied by means of a large number of different spectroscopic techniques, including far-infrared, optical, and magnetic resonance spectroscopies. A thorough analysis, based on crystal field theory, allowed an unambiguous determination of all relevant free ion and crystal field parameters. We show that inclusion of methods sensitive to the nature of the lowest-energy states is essential to arrive at a correct description of the states that are most relevant for the static and dynamic magnetic properties. The spectroscopic investigations also allowed for a full understanding of the magnetic relaxation processes occurring in this system. Thus, the importance of spectroscopic studies for the improvement of single-molecule magnets is underlined.

Three-dimensional analysis of the correlation between anterior tooth form and face shape.

Traditional esthetic guidelines and denture-tooth selection protocols suggest a correlation between a patient's face and anterior tooth shapes. This study examined the correlation between face shape, maxilla shape, and maxillary anterior tooth form with fully automated algorithms. Three-dimensional digital datasets of the faces and maxillae were obtained from 117 people. Correlation was analyzed using canonical correlation analysis, ridge regression, and the Hausdorff-distance. A weak but not statistically significant correlation between face and tooth shape could be identified. However, a good prediction of tooth shape from the facial data was not possible. The described approach revealed a weak correlation between face shape and tooth shape, but the outcome was not accurate enough for clinical use.

Analysis of select facial and dental esthetic parameters.

This clinical study examined objective smile parameters in the natural anterior dentition. Standardized intraoral and extraoral photographs were taken of 106 Caucasian adults (54 women, 52 men) with a healthy dentition. The following parameters were analyzed: correlation of dental and facial midline, upper lip position and curvature, relationship of the maxillary anterior incisal curve with lower lip, number of teeth displayed in a smile, distance between maxillary anterior teeth and lower lip, slope of tooth, and lip arc. The simple frequency distribution of measured variables revealed an average smile with coinciding dental and facial midlines, an average smile line, and a straight upper lip curvature. With an average smile, the maxillary anterior teeth did not touch the lower lip, teeth were displayed up to the second premolar, and the maxillary anterior incisal curve was parallel to the lower lip. Oval was the most prevalent tooth form. A slope of 9 degrees was detected for the mean tooth arc and 13 degrees for the mean lip arc. The outcomes of this clinical study provide a quantifiable frame for esthetic evaluation, treatment planning, and restoration fabrication.

Resin bond to indirect composite and new ceramic/polymer materials: a review of the literature.

STATEMENT OF THE PROBLEM: Resin bonding is essential for clinical longevity of indirect restorations. Especially in light of the increasing popularity of computer-aided design/computer-aided manufacturing-fabricated indirect restorations, there is a need to assess optimal bonding protocols for new ceramic/polymer materials and indirect composites. PURPOSE OF THE STUDY: The aim of this article was to review and assess the current scientific evidence on the resin bond to indirect composite and new ceramic/polymer materials. MATERIALS AND METHODS: An electronic PubMed database search was conducted from 1966 to September 2013 for in vitro studies pertaining the resin bond to indirect composite and new ceramic/polymer materials. RESULTS: The search revealed 198 titles. Full-text screening was carried out for 43 studies, yielding 18 relevant articles that complied with inclusion criteria. No relevant studies could be identified regarding new ceramic/polymer materials. Most common surface treatments are aluminum-oxide air-abrasion, silane treatment, and hydrofluoric acid-etching for indirect composite restoration. Self-adhesive cements achieve lower bond strengths in comparison with etch-and-rinse systems. Thermocycling has a greater impact on bonding behavior than water storage. CONCLUSIONS: Air-particle abrasion and additional silane treatment should be applied to enhance the resin bond to laboratory-processed composites. However, there is an urgent need for in vitro studies that evaluate the bond strength to new ceramic/polymer materials. CLINICAL SIGNIFICANCE: This article reviews the available dental literature on resin bond of laboratory composites and gives scientifically based guidance for their successful placement. Furthermore, this review demonstrated that future research for new ceramic/polymer materials is required.

The correlation between anterior tooth form and gender - a 3D analysis in humans.

This study examined the correlation between maxillary anterior tooth form and gender with three-dimensional data. Three-dimensional digital models of the area between the maxillary right central incisor and the maxillary right canine were obtained from 120 Caucasian subjects (60 males and 60 females) with healthy dentitions. Correlation between gender and tooth form was assessed applying logistic regression, with and without size standardization. Success rates were estimated using 10-fold cross-validation. Principal components that correlated with gender were evaluated with a Wald test. Values for the significance of the predictors were provided with a likelihood ratio test (P < 0.05). Significant correlation between gender and tooth shape was found for the maxillary central incisor (P = 0.003), lateral incisor (P ≤ 0.001), and canine individually (P ≤ 0.001), and for the three teeth combined (P ≤ 0.001) without size standardization. For the maximillary right lateral incisor (P=0.004), canine (P ≤ 0.001), and a correlation of the teeth (P ≤ 0.001), a correlation was also established after size standardization. Prediction of gender was not possible without information on tooth size for the maxillary right central incisor (P =0.15). maxillary anterior teeth have gender-specific differences. Differences in tooth size account for part of the correlation. However, tooth shapes are also gender specific.

Minimally invasive restoration of a maxillary central incisor with a partial veneer.

Minimally invasive treatment modalities allow for the preservation of sound tooth substance. However, by limiting the preparation to the extent of a defect, the transition between restoration and natural tooth may be moved to more visible areas. The materials available for the restoration of a limited defect in the anterior area are either resin composite materials or porcelain. A patient was presented who asked for the replacement of a discolored filling on the maxillary right central incisor. Tooth preparation was limited to the extent of the old filling, and a porcelain partial veneer restoration was fabricated. Despite the horizontal finish line in the middle of the clinical crown, a result could be achieved that was regarded as a success by the patient. This type of restoration proves to be a suitable alternative to direct composite restorations in the anterior area for the reconstruction of a limited defect, eg, due to a dental trauma.

Rehabilitation of an extensive anterior explantation defect--a case report.

This article illustrates the surgical and prosthetic rehabilitation of an extensive defect in the area of a mandibular lateral incisor following explantation of a dental implant. Bone and soft tissue defects existed after removal of the implant. Guided bone regeneration, a subepithelial connective tissue graft, and gradual pontic contouring were used to attempt correction of the defect. The missing tooth was replaced by a single-retainer, all-ceramic, resin-bonded fixed partial denture. The gingival contours were reestablished, but without complete regeneration of the interdental papillae. This article describes the use of several regenerative techniques in the treatment of dental defects and underscores the difficulty of complete correction of papilla deficiencies.