Glutaraldehyde collagen cross‐linking stabilizes resin–dentin interfaces and reduces bond degradation

This study evaluated the stability of resin–dentin interfaces treated with glutaraldehyde‐containing agents, and assessed collagen degradation in dentin matrices treated with Gluma. Microtensile bond strength (μTBS) was evaluated 24 h and 6 months after treatment with three desensitizers (Gluma Desensitizer, Gluma Desensitizer Power Gel, and MicroPrime G) and two etch‐and‐rinse adhesives (Comfort Bond & Desensitizer and iBond TE). Demineralized beams of human dentin were treated with water or Gluma, and the degradation of collagen in these beams was assessed by quantification of the dry mass loss and of the amount of hydroxyproline released from hydrolyzed specimens after 1 or 4 wk. All groups demonstrated significant reduction in μTBS after 6 months, except for Gluma Desensitizer and iBond TE groups, which showed decreases of 7.2% and 10.8%, respectively. The most prevalent failure mode was ‘mixed’. Significantly less hydroxyproline was released from Gluma‐treated beams than from control beams after 4 wk. Beams treated with Gluma yielded significantly less dry mass loss than did beams in the control group. Collagen cross‐linking with glutaraldehyde‐containing agents may assist in the stabilization of resin–dentin bonds by reducing the amount of collagen solubilized from dental matrices in the hybrid layer. In turn, this may contribute to the preservation of adhesive interfaces.     

Droit à mourir et suicide assisté : état des lieux et analyse critique

ObjectivesIn the context of the present re-examination of the French bioethical laws by the National Advisory Ethics Committee (“Comité consultatif national d’éthique”: CCNE), a recent survey indicated a request of the public opinion to obtain a medical aid in end of life and a so-called “assisted suicide”. This led psychiatrists to re-consider their role and deontological position which usually led them to consider a request for an assistance in suicide as – a priori – a pathological demand, occurring within a suicidal crisis. The present article intends to: 1) describe the laws and practices of countries which allow medically assisted end of life help procedures; 2) clarify the definitions of “assisted suicide”, “assistance to suicide” and “euthanasia”; 3) consider available epidemiological data and the roles given to doctors and, more specifically psychiatrists, in these procedures; 4) analyse the rationale behind these demands. These considerations should enable French psychiatrists to clarify their position when facing requests for a medical aid in dying.MethodsFour European countries (Switzerland, the Netherlands, Belgium, Luxemburg) and Oregon (the first US state to introduce legislation) were considered, since they accumulated and published a large amount of experiences and data about “assisted suicide” and medical help in dying. In total, 127 articles were selected, mainly from PubMed and Cairn databases, published between 1997 and 2020. These articles deal with legal considerations, epidemiological data, ethical and sociological considerations.ResultsLaws and practices differ notably according to the state/country. In Belgium, the Netherlands and Luxemburg, as in Oregon, the medical help in dying has been de-criminalized, as long as certain legal criteria are met. In Switzerland, where no specific law exists in the penal code, non-governmental associations have benefited from the legal vacuum and organized the practice of “assisted suicide” for “altruistic motives”. In the scientific and legal literature, the terms used to describe and define the medical help in dying upon request differ greatly. In France, the National Advisory Ethics Committee defines euthanasia (“euthanasie”), assisted suicide (“suicide assisté”) and suicide assistance (“assistance au suicide”). Available epidemiological data, whatever the country considered, indicate that requests for a medical aid in dying are expressed mainly by patients aged over 60 years and suffering from cancer. Psychiatric diseases account for only 1% to 3%. Most often, systematic assessment by a psychiatrist is neither requested nor made, when the demand does not occur during a primary psychiatric illness. In the case of an existing primary psychiatric pathology, a psychiatrist assesses the case against formal legal predefined criteria. This latter practice was only recently introduced, after some feedback and after legal actions had been brought to Court. When the underlying motivations of the request are considered, it appears that, even in the absence of an evolving psychiatric condition, several psychological or psychopathological reasons prevail such as spirituality, attachment style, social isolation, despair, depression… which should greatly benefit psychiatric exploration, investigation and expertise.ConclusionIn some countries, the request for medically assisted help in dying has become a legal and social reality. In France, where the public debate is still open, it should be emphasized that a psychiatric assessment and interview should be systematically provided to any person requesting medical assistance to die or commit suicide. It is the commitment of psychiatrists to understand the implicit demands and unexpressed motives underlying this request which have strong links with the unique life-events and emotional experiences of the person. The psychiatrist has a unique role in the contextualization of such a request.     

Effects of disulfide bonds formed during isolation process on the structure of the postsynaptic density

The biochemical, morphological and structural properties of rat postsynaptic densities (PSDs) isolated under conditions where disulfide bond formation was allowed or curtailed were studied here. Biochemical analyses revealed that the isolated PSDs were composed by a similar set of proteins regardless of the differences in their isolation processes. The PSDs isolated under the conditions where disulfide bond formation was curtailed were more easily dissociated by treatments with urea, guanidine hydrochloride and deoxycholate than the PSDs isolated under conditions where disulfide bond formation was allowed. Consistently, the structure of the PSDs isolated under the former condition appeared to be more fragmented than those isolated under the latter condition, as revealed by electron microscopy. The results indicate that the disulfide bonds formed during the isolation process significantly tighten the PSD structure and further suggest that the PSD in vivo is a protein aggregate whose constituent proteins be held together primarily by non-covalent interactions.     

Alpha,beta hybrid peptides: a polypeptide helix with a central segment containing two consecutive beta-amino acid residues

Conformational studies on the synthetic 11-aa peptide t-butoxycarbonyl (Boc)-Val-Ala-Phe-alpha-aminoisobutyric acid (Aib)-(R)-beta3-homovaline (betaVal)-(S)-beta3-homophenylalanine (betaPhe)-Aib-Val-Ala-Phe-Aib-methyl ester (OMe) (peptide 1; betaVal and betaPhe are beta amino acids generated by homologation of the corresponding l-residues) establish that insertion of two consecutive beta residues into a polypeptide helix can be accomplished without significant structural distortion. Crystal-structure analysis reveals a continuous helical conformation encompassing the segment of residues 2-10 of peptide 1. At the site of insertion of the betabeta segment, helical hydrogen-bonded rings are expanded. A C15 hydrogen bond for the alphabetabeta segment and two C14 hydrogen bonds for the alphaalphabeta or betaalphaalpha segments have been characterized. The following conformational angles were determined from the crystal structure for the beta residues: betaVal-5 (= -126 degrees, = 76 degrees, and psi = -124) and betaPhe-6 (=-88 degrees, = 80 degrees, and psi =-118). The N terminus of the peptide is partially unfolded in crystals. The 500-MHz 1H-NMR studies establish a continuous helix over the entire length of the peptide in CDCl3 solution, as evidenced by diagnostic nuclear Overhauser effects. The presence of seven intramolecular hydrogen bonds is also established by using solvent dependence of NH chemical shifts.     

Lithium di silicate ceramic surface treated with Er,Cr:YSGG and other conditioning regimes bonded to orthodontic bracket

AimTo assess bond integrity and modes of failure of metallic brackets to lithium disilicate ceramics (LDC) conditioned with Er,Cr:YSGG laser (ECL).Material and methodsSixty LDC were arbitrarily allocated into six groups (n = 15) according to the type of ceramic surface conditioning treatment. Group 1 surface treated with silane (S) only, group 2 surface etched with hydrofluoric acid (HF)+ S, group 3 surface conditioned with HF+ ultrasonic bath (UB)+ S, group 4 sand blasting (SB) of glass ceramic surface with 50 µm Al₂O₃, group 5 surface conditioned with self-etch ceramic primer (SECP) and in group 6 surface treated with ECL + S. After conditioning, the specimens were positioned in a universal testing device for shear bond strength (SBS) testing. Adhesive Remnant Index (ARI) was used to determine sites of bond failure. Among experimental groups analysis of variance (ANOVA) and Tukey multiple comparison test was used at a significance level of (p < 0.05).ResultsThe highest SBS values were observed in group 3 HF+ UB + S (18.21 ± 1.241) and the lowest SBS values were displayed group 1 surface treated with S only (5.21 ± 0.23). Specimens surface conditioned in group 2 with HF+ S (17.85 ± 1.25), group 3 HF+ UB + S (18.21 ± 1.241) and group 6 ECL + S (17.09 ± 1.114) unveiled comparable SBS values (p > 0.05).ConclusionLDC conditioned with ECL at (4.5 W and 30 Hz) has a potential to be used in clinical settings alternate to HF acid.     

中医临床研究治疗前后数据比较存在的问题与对策

目的 对当前中医药防治病毒性肝炎临床科研文献中治疗前后数据比较所采取的统计方法进行辨析.方法 模拟某慢性乙型肝炎临床研究的前后治疗数据,分别应用两样本t检验和配对样本t检验进行统计分析,比较结果.结果 由于两样本t检验和配对样本t检验主要针对独立样本之间的差异作出;统计推断,而治疗前后数据比较属于来自同一样本的前后2次...     

Structure–properties relationships in dental adhesives: Effect of initiator,matrix monomer structure,and nano-filler incorporation

Objectives

This is a confirmatory study to evaluate the effect of photoinitiator type and concentration, matrix monomer chemical structure, and nanoparticle incorporation on the physical and mechanical properties of an experimental dentin bonding agent.