Testing General Relativity with the Reflection Spectrum of the Supermassive Black Hole in 1H0707-495.

Recently, we have extended the x-ray reflection model relxill to test the spacetime metric in the strong gravitational field of astrophysical black holes. In the present Letter, we employ this extended model to analyze XMM-Newton, NuSTAR, and Swift data of the supermassive black hole in 1H0707-495 and test deviations from a Kerr metric parametrized by the Johannsen deformation parameter α_{13}. Our results are consistent with the hypothesis that the spacetime metric around the black hole in 1H0707-495 is described by the Kerr solution.

A note on the observational evidence for the existence of event horizons in astrophysical black hole candidates.

Black holes have the peculiar and intriguing property of having an event horizon, a one-way membrane causally separating their internal region from the rest of the Universe. Today, astrophysical observations provide some evidence for the existence of event horizons in astrophysical black hole candidates. In this short paper, I compare the constraint we can infer from the nonobservation of electromagnetic radiation from the putative surface of these objects with the bound coming from the ergoregion instability, pointing out the respective assumptions and limitations.

A randomized clinical trial comparing at-home and in-office tooth whitening techniques: A nine-month follow-up.

Background: The aim of this split-mouth, randomized controlled trial was to compare the whitening results of at-home and in-office tooth bleaching techniques and the longevity of their effects at nine months after teeth had been bleached.

Methods: The authors conducted a study involving a 14-day bleaching period, during which the first maxillary premolars of 17 participants, who were 20 to 25 years of age, were bleached by means of either an at-home technique involving 10 percent carbamide peroxide or an in-office technique involving 38 percent hydrogen peroxide. The authors recorded color variables as proposed by the Commission Internationale de l'Eclairage-lightness (L*), redness (a*) and yellowness (b*)-by using a spectrophotometer at baseline and at one week, one month and nine months after bleaching.

Color stability of bleached teeth over time: an in vitro study.

Objective: The aim of this study was to evaluate the in vitro color stability of bleached teeth by means of a 6-day staining procedure.

Material And Methods: 20 caries-free randomly divided into two groups. Test group: a bleaching agent (Zoom 2, Discus Dental) was applied to the labial surfaces following the manufacturer's instructions.

Double microtensile bond strength test: an alternative methodology for sample preparation.

The aim of the present study was to compare the technique currently used for carrying out the microtensile bond strength (muTBS) test with an alternative method. Six human molars were sectioned transversally to obtain two specimens from each tooth: a 0.75-mm-thick slab of mid-coronal dentin, which presented an occlusal and a cervical surface (DS specimen); and the remaining section of the tooth with an exposed dentin surface (SS specimen).

Gravitational particle production in braneworld cosmology.

Gravitational particle production in a time variable metric of an expanding universe is efficient only when the Hubble parameter H is not too small in comparison with the particle mass. In standard cosmology, the huge value of the Planck mass M{Pl} makes the mechanism phenomenologically irrelevant. On the other hand, in braneworld cosmology, the expansion rate of the early Universe can be much faster, and many weakly interacting particles can be abundantly created.

An 8-year follow-up of a fractured endodontically treated incisor restored with a modified laminate veneer.

This clinical report describes the restoration of a left maxillary first incisor using an all-ceramic one-piece coronal post and a laminate veneer feature. This proposed restoration technique represents an alternative to traditional restoration procedures such as metal-ceramic restorations, all ceramic crowns and porcelain laminate veneers. This restoration preserves the remaining tooth structure, re-establishes function and offers good esthetic results.

Influence of operator skill on microleakege of total-etch and self-etch bonding systems.

Objectives: To evaluate the influence of operator skill on microleakage in class V restorations using simplified bonding systems.

Methods: Two cavities were carried out on the buccal and lingual surfaces of 50 human bicuspid teeth. The teeth were randomly assigned to two groups according to the operator's skill: student group and expert group.

A rational use of dental materials in posterior direct resin restorations in order to control polymerization shrinkage stress.

One of the main problems when using resin-based composites is the resulting polymerization shrinkage stress. Composite strain is hindered every time the composite is bonded to the tooth's walls. In the pre-gel phase the shrinkage stress is reduced by the composite flow from the free to the bonded surface areas.

A review of polymerization shrinkage stress: current techniques for posterior direct resin restorations.

In general excellent results cannot be guaranteed when using resin-based composites for posterior restorations. This is due to polymerization shrinkage which can still be regarded as the primary negative characteristic of composite resins. A review of available literature regarding the polymerization process, its flaws, and suggested strategies to avoid shrinkage stress was conducted.

SEM qualitative evaluation of four self-etching adhesive systems.

Aim: Recently, there has been a tendency to simplify bonding procedures. Current self-etching adhesives combine conditioning, priming and bonding functions thus reducing technique-sensitivity as well as the risk of making errors. Another important advantage of this approach is that it allows the resin to etch and infiltrate the substratum simultaneously thus reducing the risk of any discrepancy between these 2 processes.

[Sclerotic dentin: aetio-pathogenetic hypotheses].

The situation with regard to current knowledge concerning dentinal sclerosis is examined. SEM and TEM examination of specimens of sclerotic dentin showed changes in diameter and tubular content leading to various degrees of obstruction of the lumen. There is agreement that this is due to the neo-apposition of peri-tubular dentin associated with intra-tubular deposition of crystals of Whitelockite, although the debate is still open on how such deposition may come about.