Agenesis of maxillary lateral incisors: Bone formation by orthodontic tooth movement and long-term stability of the edentulous alveolar ridge at 12-15 years after treatment.

Introduction: The primary aim of this study was to assess the amount and long-term stability of orthodontically created bone in patients with agenesis of maxillary lateral incisors after canine distalization. The secondary aim was to explore the impact of patient age on the process of alveolar bone resorption.

Methods: A group of patients with agenesis of the maxillary permanent lateral incisor was examined at 4 time points: the beginning of orthodontic treatment (T1, n = 80), the end of treatment (T2, n = 80), 2-5 years after treatment (T3, n = 79), and 12-15 years after treatment (T4, n = 32).

Stereoselective Synthesis of 1,n-Dicarbonyl Compounds Through Palladium-Catalyzed Ring Opening/Isomerization of Densely Substituted Cyclopropanols.

We report a highly diastereoselective protocol for the synthesis of 1,4- and 1,5-dicarbonyl compounds from densely substituted cyclopropanols. The methodology involves a palladium-catalyzed ring opening reaction followed by a "metal-walk" and oxidation of a remote hydroxyl group. The methodology represents a new application of cyclopropanols as initiation sites for chain walking remote functionalization.

Copper-Catalyzed Carbomagnesiation of 1-Halocyclopropenes.

We report a versatile copper-catalyzed carbomagnesiation reaction of poly- and fully substituted 1-halocyclopropenyl esters. By fine-tuning the regioselectivity of the addition, we were able to access configurationally stable fully substituted cyclopropyl carbenoid intermediates. These intermediates were subsequently trapped with electrophiles to furnish stereodefined poly- and fully substituted halocyclopropyl esters.

Stereoinvertive S1 Through Neighboring Group Participation.

Neighboring group participation, the assistance of non-conjugated electrons to a reaction center, is a fundamental phenomenon in chemistry. In the framework of nucleophilic substitution reactions, neighboring group participation is known to cause rate acceleration, first order kinetics (S1), and retention of configuration. The latter phenomenon is a result of double inversion: the first one when the neighboring group displaces the leaving group, and the second when a nucleophile substitutes the neighboring group.

Synthesis of Stereodefined Polysubstituted Bicyclo[1.1.0]butanes.

We report a highly diastereoselective synthesis of polysubstituted bicyclobutanes possessing up to three stereodefined quaternary centers and five substituents. Our strategy involves a diastereoselective carbometalation of cyclopropenes followed by a cyclization to furnish the bicyclobutane ring system. This straightforward approach allows for the incorporation of a diverse range of substituents and functional groups, notably without the need for electron-withdrawing functionalities.

Stereoselective Nucleophilic Halogenation at CF-Substituted Nonclassical Carbocation.

CF-substituted cyclopropyl carbinol derivatives undergo regioselective and diastereoselective nucleophilic halogenation at the quaternary carbon center to provide acyclic products as a single diastereomer. The selectivity of the substitution is rationalized by the formation of a nonclassical cyclopropylcarbinyl cation intermediate, reacting at the most-substituted carbon center. Tertiary alkyl chlorides, bromides, and fluorides adjacent to a stereogenic C-CF-motif are diastereomerically pure and can be obtained in few catalytic steps from commercially available alkynes.

Highly Diastereoselective Preparation of Tertiary Alkyl Thiocyanates en Route to Thiols by Stereoinvertive Nucleophilic Substitution at Nonclassical Carbocations.

An effective InBr-catalyzed nucleophilic thiocyanation of cyclopropyl alcohols has been developed. The reaction takes place at the quaternary carbon stereocenter of the cyclopropyl carbinol with a complete inversion of configuration, offering a novel pathway for the creation of complex tertiary alkyl thiocyanates with high diastereopurity. These substitution reactions proceed under mild reaction conditions and tolerate several functional groups.

Comparison of spontaneous eruption and modified closed eruption technique with palatal traction in alignment of impacted maxillary central incisor teeth.

Background: Central incisor impaction is a rare condition with potentially severe clinical and psychological implications for the patient. Treatment techniques vary according to the pretreatment situation and individual factors. The aim of this study was to compare the esthetic outcomes and treatment times between two different approaches.

Electrochemical Decalcification-Exfoliation of Two-Dimensional Siligene, SiGe: Material Characterization and Perspectives for Lithium-Ion Storage.

A two-dimensional (2D) silicene-germanene alloy, siligene (SiGe), a single-phase material, has attracted increased attention due to its two-elemental low-buckled composition and unique physics and chemistry. This 2D material has the potential to address the challenges caused by low electrical conductivity and the environmental instability of corresponding monolayers. Yet, the siligene structure was studied in theory, demonstrating the material's great electrochemical potential for energy storage applications.

Selective Terminal Functionalization of Linear Alkanes.

A two-step sequential strategy involving a biocatalytic dehydrogenation/remote hydrofunctionalization, as a unified and versatile approach to selectively convert linear alkanes into a large array of valuable functionalized aliphatic derivatives is reported. The dehydrogenation is carried out by a mutant strain of a bacteria Rhodococcus and the produced alkenes are subsequently engaged in a remote functionalization through a metal-catalyzed hydrometalation/migration sequence that subsequently react with a large variety of electrophiles. The judicious implementation of this combined biocatalytic and organometallic approach enabled us to develop a high-yielding protocol to site-selectively functionalize unreactive primary C-H bonds.

Tetrazole Diversification of Amino Acids and Peptides via Silver-Catalyzed Intermolecular Cycloaddition with Aryldiazonium Salts.

Selective structural modification of amino acids and peptides is a central strategy in organic chemistry, chemical biology but also in pharmacology and material science. In this context, the formation of tetrazole rings, known to possess significant therapeutic properties, would expand the chemical space of unnatural amino acids but has received less attention. In this study, we demonstrated that the classic unimolecular Wolff rearrangement of α-amino acid-derived diazoketones could be replaced by a faster intermolecular cycloaddition reaction with aryldiazonium salts under identical practical conditions.

Highly Diastereoselective Preparation of Tertiary Alkyl Isonitriles by Stereoinvertive Nucleophilic Substitution at a Nonclassical Carbocation.

A highly efficient SnCl-catalyzed nucleophilic isocyanation of cyclopropyl ethers has been developed. The reaction proceeds at the quaternary carbon stereocenter of the cyclopropane with a complete inversion of configuration, providing a new avenue for the construction of synthetically challenging tertiary alkyl isonitriles with high diastereopurity. The diversity of the incorporated isocyanide group has been demonstrated by the transformation of tertiary alkyl isonitriles into the corresponding tertiary alkyl amines, amides, and cyclic ketoimines.

Ultrafine-Grained Zn-Mg-Sr Alloy Synthesized by Mechanical Alloying and Spark Plasma Sintering.

Zinc materials are considered promising candidates for bioabsorbable medical devices used for the fixation of broken bones or stents. Materials for these applications must meet high mechanical property requirements. One of the ways to fulfil these demands is related to microstructure refinement, particularly the decrease in grain size.

Stereoselective Preparation of CF-Containing Cyclopropanes.

A regio- and diastereoselective carbometalation of easily accessible CF-substituted cyclopropenes is developed with a diastereoselectivity of the addition opposite to the CF group. This simple strategy allows the preparation of polysubstituted (up to penta-) cyclopropyl rings possessing two adjacent quaternary carbon stereocenters with excellent diastereoselectivities.

Synthesis and Functionalization of Tertiary Propargylic Boronic Esters by Alkynyllithium-Mediated 1,2-Metalate Rearrangement of Borylated Cyclopropanes.

Implementing the use of alkynyllithium reagents in a stereospecific 1,2-metalate rearrangement-mediated ring opening of polysubstituted cyclopropyl boronic esters provides a variety of tertiary pinacol boranes bearing adjacent tertiary or quaternary carbon stereocenters with high levels of diastereomeric purity. The potential of this strategy was demonstrated through a selection of α- and γ-functionalization of the propargyl boronic esters.

Stereoselective Construction of Tertiary Homoallyl Alcohols and Ethers by Nucleophilic Substitution at Quaternary Carbon Stereocenters.

An efficient method for the stereoselective construction of tertiary C-O bonds via a stereoinvertive nucleophilic substitution at the quaternary carbon stereocenter of cyclopropyl carbinol derivatives using water, alcohols and phenols as nucleophiles has been developed. This substitution reaction proceeds under mild conditions and tolerates several functional groups, providing a new access to the stereoselective formation of highly congested tertiary homoallyl alcohols and ethers.

Directed Diastereoselective Cyclopropanation and Epoxidation of Alkenyl Cyclopropyl Carbinol Derivatives.

We report the directed diastereoselective Simmons-Smith cyclopropanation and vanadium-catalyzed epoxidation reactions of alkenyl cyclopropyl carbinol derivatives. The reaction furnished densely substituted stereodefined bicyclopropanes and cyclopropyl oxiranes as a single diastereomer in each case. The remarkable selectivity is obtained thanks to the rigidity of the cyclopropyl core, allowing diastereoselective reactions on the alkenyl moiety.

Regio- and Diastereoselective Carbometalation Reaction of Cyclopropenes.

The various facets of the chemistry of cyclopropane derivatives, the smallest carbocycle, are amazingly diverse and continue to fascinate theoreticians, synthetic or structural chemists having interest in fundamental physical, medicinal chemistry, and natural product synthesis. The challenges generated by this intriguing cyclic arrangement of only three tetravalent carbons represent a wide area of the chemical spectrum. From fundamental aspects of bonding through the synthesis of highly strained molecules, the understanding of the mode of action in biological systems to the selective cleavage into acyclic substrates makes the chemistry of these small rings fascinating.

Stereoselective Synthesis of Polysubstituted Spiropentanes.

A new approach to polysubstituted spiropentanes is developed through a regio- and diastereoselective carbometalation of sp-disubstituted cyclopropenes. The control of selectivity originates from a combined -facial diastereoselective carbometalation with a regio-directed addition. The regio-controlling element subsequently serves as a leaving group in an intramolecular nucleophilic substitution.

Borylated Cyclopropanes as Spring-Loaded Entities: Access to Vicinal Tertiary and Quaternary Carbon Stereocenters in Acyclic Systems.

Herein, we present the formation of acyclic frameworks bearing two consecutive stereocenters of either tertiary or quaternary nature starting from easily accessible cyclopropenes. This holistic approach involves a regio- and diastereoselective hydro- or carboborylation of substituted cyclopropenyl esters. Formation of boronate complexes of the latter via the addition of nucleophiles and subsequent stereospecific 1,2-migration with carbon-carbon bond cleavage delivered the title compounds.

Advanced Zinc-Magnesium Alloys Prepared by Mechanical Alloying and Spark Plasma Sintering.

Zinc and its alloys are considered as promising materials for the preparation of biodegradable medical devices (stents and bone fixation screws) due to their enhanced biocompatibility. These materials must achieve an ideal combination of mechanical and corrosion properties that can be influenced by alloying or thermomechanical processes. This paper presents the effects of different mechanical alloying (MA) parameters on the composition of Zn-1Mg powder.

Intrusion of overerupted molars with temporary anchorage devices before prosthetic reconstruction: A case report.

Extraction of teeth without adequate prosthetic rehabilitation frequently can lead to overeruption of opposing teeth, which may cause occlusal disturbances and complicate dental restoration. Equilibration with consequent need of endodontic treatment, surgical intrusion or extraction are often indicated as a remedy in such cases. The article proposes a method of orthodontic intrusion with the use of temporary anchorage devices as a predictable and less invasive option.

Ectodermal dysplasia: important role of complex dental care in its interdisciplinary management.

Aim: Despite the fact that ectodermal dysplasia (ED) is a rare disease, it is often seen in a tertiary clinic. ED affects ectodermal tissues such as skin, hair, teeth, nails, and sweat glands. Patients usually have sparse light hair, deformed nails, and dry skin.

Preparation of Distant Quaternary Carbon Stereocenters by Double Selective Ring-Opening of 1,1-Biscyclopropyl Methanol Derivatives.

The diastereoselective double carbometalation reaction of cyclopropenes provides, in a single-pot operation, two ω-ene-[1,1]-bicyclopropyl ester derivatives. One regioisomer then undergoes a Pd-catalyzed addition of aryl iodide to provide skipped dienes possessing several distant stereocenters including two congested quaternary carbon centers with excellent diastereoselectivity.