Probing the Long- and Short-Range Structural Chemistry in the C-Type Bixbyite Oxides Th0.40Nd0.48Ce0.12O1.76, Th0.47Nd0.43Ce0.10O1.785, and Th0.45Nd0.37Ce0.18O1.815 via Synchrotron X-ray Diffraction and Absorption Spectroscopy.

The long- and short-range structural chemistry of the C-type bixbyite compounds Th0.40Nd0.48Ce0.12O1.76, Th0.47Nd0.43Ce0.10O1.785, and Th0.45Nd0.37Ce0.18O1.815 is systematically examined using synchrotron X-ray powder diffraction (S-PXRD), high-energy resolution fluorescence detection X-ray absorption near edge (HERFD-XANES), and extended X-ray absorption fine structure spectroscopy (EXAFS) measurements supported by electronic structure calculations. S-PXRD measurements revealed that the title compounds all form classical C-type bixbyite structures in space group Ia3̅ that have disordered cationic crystallographic sites with further observation of characteristic superlattice reflections corresponding to oxygen vacancies. Despite the occurrence of oxygen vacancies, HERFD-XANES measurements on the Ce L3-edge revealed that Ce incorporates as Ce4+ into the structures but involves local distortion that resembles cluster behavior and loss of nearest-neighbors. In comparison, HERFD-XANES measurements on the Nd L3-edge supported by electronic structure calculations reveal that Nd3+ adopts a local coordination environment similar to the long-range C-type structure while providing charge balancing for the formation of oxygen defects. Th L3-edge EXAFS analysis reveals shorter average Th-O distances in the title compounds in comparison to pristine ThO2 in addition to shorter Th-O and Th-Ce distances compared to Th-Th or Ce-Ce in the corresponding F-type binary oxides (ThO2 and CeO2). These distances are further found to decrease with the increased Nd content of the structures despite simultaneous observation of the overall lattice structure progressively expanding. Linear combination calculations of the M-O bond lengths are used to help explain these observations, where the role of oxygen defects, via Nd3+ incorporation, induces local bond contraction and enhanced Th cation valence, leading to the observed increased lattice expansion with progressive Nd3+ incorporation. Overall, the investigation points to the significance of dissimilar cations exhibiting variable short-range chemical behavior and how it can affect the long-range structural chemistry of complex oxides.

Functionalization of Tetraphosphido Ligands by Heterocumulenes.

Although numerous polyphosphido complexes have been accessed through the transition-metal-mediated activation and functionalization of white phosphorus (P4), the selective functionalization of the resulting polyphosphorus ligands in these compounds remains underdeveloped. In this study, we explore the reactions between cyclotetraphosphido cobalt complexes and heterocumulenes, leading to functionalized P4 ligands. Specifically, the reaction of carbon disulfide (CS2) with [K(18c-6)][(Ar*BIAN)Co(η4-P4)] ([K(18c-6)]1, 18c-6 = [18]crown-6) affords the adduct [K(18c-6)][(Ar*BIAN)Co(η3:η1-P4CS2)] ([K(18c-6)]3), in which CS2 is attached to a single phosphorus atom (Ar* = 2,6-dibenzhydryl-4-isopropylphenyl, BIAN = 1,2-bis(arylimino)acenaphthene diimine). In contrast, the insertion of bis(trimethylsilyl)sulfur diimide S(NSiMe3)2 into a P-P bond of [K(18c-6)]1 yields [K(18c-6)][(Ar*BIAN)Co(η3:η1-P4SN2(SiMe3)2)] (K(18c-6)]4). This salt further reacts with Me3SiCl to form [(Ar*BIAN)Co(η3:η1-P4SN2(SiMe3)3] (5), featuring a rare azatetraphosphole ligand. Moreover, treatment of the previously reported complex [(Ar*BIAN)Co(η3:η1-P4C(O)tBu)] (2) with isothiocyanates results in P-C bond insertion, yielding [(Ar*BIAN)Co(η3:η1-P4C(S)N(R)C(O)tBu)] (6a,b; R = Cy, Ph).

Influence of Layer Thickness and Shade on the Transmission of Light through Contemporary Resin Composites.

BACKGROUND: Material-dependent parameters have an important impact on the efficiency of light polymerization. The present in vitro study aimed to investigate the influence of the increment thickness and shade of nano- and nanohybrid resin composites on the transmission of curing light. METHODS: Three contemporary resin composites were evaluated: Tetric EvoCeram® (TEC); Venus Diamond® (VD); and Filtek Supreme XTE® (FS XTE). Light transmission (LT) was recorded in accordance with the sample thickness (0.5 to 2.7 mm) and the shade. Polymerized samples were irradiated for 10 s each using the high-power LED curing light Celalux 2 (1900 mW/cm2). LT was simultaneously recorded using the MARC Patient Simulator (MARC-PS). RESULTS: LT was strongly influenced by the composite layer thickness. For 0.5 mm-thick samples, a mean power density of 735 mW/cm2 was recorded at the bottom side. For the 2.7 mm samples, a mean power density of 107 mW/cm2 was measured. Only LT was markedly reduced in the case of darker shades. From A1 to A4, LT decreased by 39.3% for FS XTE and 50.8% for TEC. Dentin shades of FS XTE and TEC (A2, A4) showed the lowest LT. CONCLUSIONS: The thickness and shade of resin composite increments strongly influences the transmission of curing light. More precise information about these parameters should be included in the manufacture manual.

Effect of Different Primers on Shear Bond Strength of Base Metal Alloys and Zirconia Frameworks.

Ensuring a secure bond between a framework structure and layering composite resin veneer is essential for a long-lasting dental restoration. A variety of primer systems are available to facilitate the adhesive bonding. Nevertheless, the growing preference for efficiency and simplicity in dentistry has made the one-bottle universal primers a desirable option. This study aims to compare the effectiveness of universal primers on the shear bond strength (SBS) of base metal alloy (BMA) and zirconia to layering composite resin. Each 160 BMA and zirconia 20 × 10 × 5 mm test specimen was fabricated. Eight different primers (SunCera Metal Primer, Metal Primer Z, Reliance Metal Primer, Alloy Primer, MKZ Primer, Monobond Plus, ArtPrime Plus, and Clearfil Ceramic Primer Plus) were applied to 20 specimens in each group. Subsequently, a 5 × 2 mm composite resin build-up was applied. SBS tests were performed after 24 h of water storage and after thermocycling (25,000 cycles, 5-55 °C). On BMA, after water storage for 24 h, the bond strength values ranged from 26.53 ± 3.28 MPa (Metal Primer Z) to 29.72 ± 2.00 MPa (MKZ Primer), while after thermocycling, bond strength values ranged from 25.19 ± 1.73 MPa (MKZ Primer) to 27.69 ± 2.37 MPa (Clearfil Ceramic Primer Plus). On a zirconia base, after 24 h, the bond strengths values ranged from 22.63 ± 2.28 MPa (Reliance Primer) to 29.96 ± 2.37 MPa (MKZ Primer) and from 23.77 ± 3.86 MPa (Metal Primer Z) to 28.88 ± 3.09 MPa (Monobond Plus) after thermocycling. While no significant difference in bond strength was found between the primers on the BMA base, five primer combinations differed significantly from each other on zirconia (p = 0.002-0.043). All primers achieved a bond strength greater than 23 MPa on both framework materials after thermocycling. Thus, all primers tested can be applied to both framework materials with comparable results.

GDF15 Contributes to the Regulation of the Mechanosensitive Responses of PdL Fibroblasts through the Modulation of IL-37.

During orthodontic tooth movement (OTM), areas of compressive and tensile forces are generated in the periodontal ligament (PdL), a mechanoreactive connective tissue between the teeth and alveolar bone. Mechanically stimulated PdL fibroblasts (PdLFs), the main cell type of PdL, express significantly increased levels of growth differentiation factor 15 (GDF15). In compressed PdL areas, GDF15 plays a fundamental role in modulating relevant OTM processes, including inflammation and osteoclast activation. However, the specific function of this factor in tensile areas has not yet been investigated. Thus, the aim of this study was to investigate the role of GDF15 in the mechanoresponse of human PdLFs (hPdLFs) that were exposed to biaxial tensile forces in vitro. Using siRNA-mediated knockdown experiments, we demonstrated that GDF15 had no impact on the anti-inflammatory force response of elongated hPdLFs. Although the anti-inflammatory markers IL1RN and IL10, as well as the activation of immune cells remained unaffected, we demonstrated an inhibitory role of GDF15 for the IL-37 expression. By analyzing osteogenic markers, including ALPL and RUNX2, along with an assessment of alkaline phosphatase activation, we further showed that the regulation of IL-37 by GDF15 modulates the osteogenic differentiation potential of hPdLFs. Despite bone resorption in tensile areas being rather limited, GDF15 was also found to positively modulate osteoclast activation in those areas, potentially by adjusting the IL-37 levels. In light of our new findings, we hypothesize that GDF15 modulates force-induced processes in tissue and bone remodeling through its various intra- and extracellular signaling pathways as well as interaction partners. Potentially acting as a master regulator, the modulation of GDF15 levels may hold relevance for clinical implications.

Grazing-incidence synchrotron radiation diffraction studies on irradiated Ce-doped and pristine Y-stabilized ZrO2 at the Rossendorf beamline.

In this work, Ce-doped yttria-stabilized zirconia (YSZ) and pure YSZ phases were subjected to irradiation with 14 MeV Au ions. Irradiation studies were performed to simulate long-term structural and microstructural damage due to self-irradiation in YSZ phases hosting alpha-active radioactive species. It was found that both the Ce-doped YSZ and the YSZ phases had a reasonable tolerance to irradiation at high ion fluences and the bulk crystallinity was well preserved. Nevertheless, local microstrain increased in all compounds under study after irradiation, with the Ce-doped phases being less affected than pure YSZ. Doping with cerium ions increased the microstructural stability of YSZ phases through a possible reduction in the mobility of oxygen atoms, which limits the formation of structural defects. Doping of YSZ with tetravalent actinide elements is expected to have a similar effect. Thus, YSZ phases are promising for the safe long-term storage of radioactive elements. Using synchrotron radiation diffraction, measurements of the thin irradiated layers of the Ce-YSZ and YSZ samples were performed in grazing incidence (GI) mode. A corresponding module for measurements in GI mode was developed at the Rossendorf Beamline and relevant technical details for sample alignment and data collection are also presented.

GDF15 Modulates the Zoledronic-Acid-Induced Hyperinflammatory Mechanoresponse of Periodontal Ligament Fibroblasts.

Orthodontic tooth movement (OTM) is thought to be impeded by bisphosphonate (BP) therapy, mainly due to increased osteoclast apoptosis and changes in the periodontal ligament (PdL), a connecting tissue between the alveolar bone and teeth. PdL cells, mainly fibroblasts (PdLFs), are crucial regulators in OTM by modulating force-induced local inflammatory processes. Recently, we identified the TGF-ß/BMP superfamily member GDF15 as an important modulator in OTM, promoting the pro-inflammatory mechanoresponses of PdLFs. The precise impact of the highly potent BP zoledronate (ZOL) on the mechanofunctionality of PdLFs is still under-investigated. Therefore, the aim of this study was to further characterize the ZOL-induced changes in the initial inflammatory mechanoresponse of human PdLFs (hPdLFs) and to further clarify a potential interrelationship with GDF15 signaling. Thus, two-day in vitro treatment with 0.5 µM, 5 µM and 50 µM of ZOL altered the cellular properties of hPdLFs partially in a concentration-dependent manner. In particular, exposure to ZOL decreased their metabolic activity, the proliferation rate, detected using Ki-67 immunofluorescent staining, and survival, analyzed using trypan blue. An increasing occurrence of DNA strand breaks was observed using TUNEL and an activated DNA damage response was demonstrated using H2A.X (phosphoS139) staining. While the osteogenic differentiation of hPdLFs was unaffected by ZOL, increased cellular senescence was observed using enhanced p21Waf1/Cip1/Sdi1 and ß-galactosidase staining. In addition, cytokine-encoding genes such as IL6, IL8, COX2 and GDF15, which are associated with a senescence-associated secretory phenotype, were up-regulated by ZOL. Subsequently, this change in the hPdLF phenotype promoted a hyperinflammatory response to applied compressive forces with an increased expression of the pro-inflammatory markers IL1ß, IL6 and GDF15, as well as the activation of monocytic THP1 cells. GDF15 appeared to be particularly relevant to these changes, as siRNA-mediated down-regulation balanced these hyperinflammatory responses by reducing IL-1ß and IL-6 expression (IL1B p-value < 0.0001; IL6 p-value < 0.001) and secretion (IL-1ß p-value < 0.05; IL-6 p-value < 0.001), as well as immune cell activation (p-value < 0.0001). In addition, ZOL-related reduced RANKL/OPG values and inhibited osteoclast activation were enhanced in GDF15-deficient hPdLFs (both p-values < 0.0001; all statistical tests: one-way ANOVA, Tukey's post hoc test). Thus, GDF15 may become a promising new target in the personalized orthodontic treatment of bisphosphonatepatients.

Influence of the orthodontic bonding procedure on biofilm formation.

INTRODUCTION: In orthodontics, white spot lesions are a persistent and widespread problem caused by the demineralization of buccal tooth surfaces around bonded brackets. The remaining adhesive around the brackets leads to surface roughness, which might contribute to demineralization. The present in vitro study aimed to compare a conventional and a modern adhesive system (APC Flash-Free technology) for orthodontic brackets with regard to the adhesion of Streptococcus sobrinus, a leading caries pathogen. METHODS: This in vitro study included 20 premolar teeth and compared 10 APC Flash-Free adhesive-coated ceramic brackets (FF)with 10 conventionally bonded (CB) ceramic clarity brackets. Specimens were incubated in an S. sobrinus suspension for 3 h. To evaluate the bacterial formation, samples were analysed with a scanning electron microscope (SEM). Imaging software was used to quantify and statistically compare percentage values of colonization (PVC) in both groups' adhesion and transition areas. RESULTS: We found a significant difference in biofilm formation between the groups for the adhesive and transition areas. PVC in the adhesive area was approximately 10.3-fold greater for the CB group compared with the FF group (median: 3.2 vs 0.31; P < 0.0001). For the transition area, median PVC was approximately 2.4-fold greater for the CB group compared with the FF group (median: 53.17 vs 22.11; P < 0.01). CONCLUSIONS: There was a significantly lower level of S. sobrinus formation around the FF bracket system than there was surrounding the conventionally bonded group. This study suggests that the FF adhesive bracket system can help reduce the occurrence of bacterial growth around orthodontic brackets.

Orthognathic Surgery with Interdisciplinary Digital Planning in Patients with Geroderma Osteodysplasticum: A Case Report.

Patients with geroderma osteodysplasticum (GO) often times have dentofacial deformities and benefit from orthognathic surgery. Because of generalized osteopenia, operations must be prepared even more meticulously than usual, and the higher risk of unfortunate fractures (bad splits) should be explained to the patients in detail. This case report is intended to portray a digital, interdisciplinary and patient-individualized planning of orthognathic surgery. It points out the individual steps that must be considered and how they can be advantageously used in patients with underlying diseases or syndromes such as GO. Through a careful digital representation of the surgical options, production of the digitally modeled splints, 3D printing and good manual surgical implementation, the quality of life of patients with GO can be increased through orthognathic surgery. Both the functions in the oral, maxillofacial region and the patient's appearance in the case presented here benefited from the interdisciplinary, individualized and digital treatment approach.

A Newly Developed Orthodontic-Logopedic Screening Procedure for Myofunctional Dysfunctions-A Pilot Study.

Interdisciplinary, patient-specific cooperation between orthodontics and speech therapy plays an important role in the therapy of myofunctional dysfunctions. The following orthodontic-logopedic screening procedure is intended to objectify the diagnosis of such dysfunctions and the progress of therapy. A diagnostic questionnaire was prepared based on existing diagnostic questionnaires for myofunctional dysfunction. It contains 32 questions, with a clinical weighting of 0 to 50 points in total. This results in a point score. The lower the score is, the lower the need for therapy is. The study included 108 patients between the ages of 6 and 50 years. After screening, the patient population was divided into Group 0 (score < 15; no speech therapy need; n = 36) and Group 1 (score ≥ 15; a speech therapy need; n = 72). Group 1 was additionally randomized into Subgroups A (with speech therapy; n = 36) and B (without speech therapy; n = 36). After a treatment interval of 6 months, all patients in Group 1 were examined again with the help of the screening procedure. Statistical analysis (SPSS) and significance testing (Mann-Whitney U test) were performed. At baseline, there was no significant difference between patients in Subgroups A and B (p = 0.157). Subgroup A had a median score of 25, and Subgroup B had a median score of 30. However, after the treatment interval, a significant improvement (p = 0.001) for Subgroup A with a median score of 11 (mean score difference = 14.67) over Subgroup B with a median score 23 (mean score difference of 7.08) was observed. The developed screening procedure was shown to be equally applicable to all patients and treatment providers. With the help of the scores in point form, the need for speech therapy and the progress of such therapy can be objectified.

Influence of Different Bracket Adhesive Systems on Enamel Demineralization-An In Vitro Study.

BACKGROUND: enamel demineralization is a common side effect of orthodontic therapy with fixed braces. The aim of the present in vitro study was to compare a conventional adhesive system and a modern adhesive system (APC Flash-Free [FF] technology) with regard to the demineralization of enamel by Streptococcus sobrinus (S. sobrinus). METHODS: this in vitro study included premolar teeth and compared APC FF adhesive brackets (Group A, n = 15) with conventional adhesive brackets (Group B, n = 15) from the same company. Specimens were incubated with a positive control group (PCG, n = 5) and a negative control group (NCG, n = 5) in an S. sobrinus suspension for three weeks. To evaluate the grade of enamel demineralization, the samples were analyzed using a polarizing microscope. RESULTS: the test specimens of group B with conventionally bonded bracket adhesive showed significantly greater (+10.8 µm) demineralization with regard to the penetration depth of the demineralization than the PCG (p = 0.012). Thus, there was a difference from group A with the new bracket adhesive of the FF brackets (+7.29 µm). Significantly, demineralization was more pronounced cervically than coronally in both groups, and it occurred cervically more frequently than grade 3 demineralization (p = 0.001). CONCLUSIONS: it seems plausible that new orthodontic bracket adhesives and the modern FF adhesive system positively contribute to the reduction in enamel demineralization during orthodontic treatment.

Influence of Root Post Materials and Aging on Fracture Strength and Marginal Gap Quality of Ceramic Crowns-An In Vitro Study.

The design of and materials for prosthodontic abutments and posts have significant influences on the fracture resistance of restored teeth. This in vitro study compared the fracture strength and marginal quality of full-ceramic crowns as a function of the inserted root posts via simulation of a five-year period of use. Test specimens were prepared from 60 extracted maxillary incisors using titanium L9 (A), glass-fiber L9 (B), and glass-fiber L6 (C) root posts. The circular marginal gap behavior, linear loading capacity, and material fatigue after artificial aging were investigated. The marginal gap behavior and material fatigue were analyzed using electron microscopy. The linear loading capacity of the specimens was investigated using the Zwick Z005 universal testing machine. None of the tested root post materials showed statistically significant differences in marginal width values (p = 0.921), except in the case of marginal gap location. For Group A, there was a statistically significant difference from the labial to the distal (p = 0.012), mesial (p = 0.000), and palatinal (p = 0.005). Similarly, Group B showed a statistically significant difference from the labial to the distal (p = 0.003), mesial (p = 0.000), and palatinal (p = 0.003). Group C showed a statistically significant difference from the labial to the distal (p = 0.001) and mesial (p = 0.009). Linear load capacity reached mean values of 455.8-537.7 N, and micro-cracks occurred after artificial aging, predominantly in Groups B and C. Through the chosen experimental design, it was shown that the root post material and root post length had no influence on the fracture strength of the test teeth before or after artificial aging. However, the marginal gap location depends on the root post material and its length, which is wider mesially and distally and also tends to be greater palatinally than labially.

GDF15 Promotes the Osteogenic Cell Fate of Periodontal Ligament Fibroblasts, thus Affecting Their Mechanobiological Response.

Periodontal ligament fibroblasts (PdLFs) exert important functions in oral tissue and bone remodeling following mechanical forces, which are specifically applied during orthodontic tooth movement (OTM). Located between the teeth and the alveolar bone, mechanical stress activates the mechanomodulatory functions of PdLFs including regulating local inflammation and activating further bone-remodeling cells. Previous studies suggested growth differentiation factor 15 (GDF15) as an important pro-inflammatory regulator during the PdLF mechanoresponse. GDF15 exerts its effects through both intracrine signaling and receptor binding, possibly even in an autocrine manner. The extent to which PdLFs are susceptible to extracellular GDF15 has not yet been investigated. Thus, our study aims to examine the influence of GDF15 exposure on the cellular properties of PdLFs and their mechanoresponse, which seems particularly relevant regarding disease- and aging-associated elevated GDF15 serum levels. Therefore, in addition to investigating potential GDF15 receptors, we analyzed its impact on the proliferation, survival, senescence, and differentiation of human PdLFs, demonstrating a pro-osteogenic effect upon long-term stimulation. Furthermore, we observed altered force-related inflammation and impaired osteoclast differentiation. Overall, our data suggest a major impact of extracellular GDF15 on PdLF differentiation and their mechanoresponse.

Radiation Exposure and Frequency of Dental, Bitewing and Occlusal Radiographs in Children and Adolescents.

Dental radiographs are valuable diagnostic aids for oral healthcare, but exposure to ionizing radiation carries health risks, especially in children due to their high radio-sensitivity. Valid reference values for intraoral radiographs in children and adolescents are still missing. This study aimed to investigate the radiation dose values and underlying justifications of dental, bitewing and occlusal X-rays in children and adolescents. Data from routinely executed intraoral radiographs between 2002 and 2020 with conventional and digital tube-heads were extracted from the Radiology Information System. The effective exposure was calculated from technical parameters and statistical tests performed. A total number of 4455 intraoral (3128 dental, 903 bitewing and 424 occlusal) radiographs were investigated. For dental and bitewing radiographs, the dose area product (DAP) was 2.57 cGy × cm2 and the effective dose (ED) 0.77 µSv. For occlusal radiographs, the DAP was 7.43 cGy × cm2 and the ED 2.22 µSv. Overall, 70.2% of all intraoral radiographs were dental, 20.3% bitewing and 9.5% occlusal radiographs. The most frequent indication for intraoral radiographs was trauma (28.7%), followed by caries (22.7%) and apical diagnostics (22.7%). Moreover, 59.7% of all intraoral radiographs were taken in boys, especially for trauma (66.5%) and endodontics (67.2%) (p ≤ 0.00). Girls were significantly more frequently X-rayed for caries diagnostics than boys (28.1% vs. 19.1%, p ≤ 0.00). The average ED of 0.77 µSv for intraoral dental and bitewing radiographs in this study was within the range of other reported values. The technical parameters of the X-ray devices were found at the lowest recommended levels to best limit the radiation exposure and to assure acceptable diagnostic efficacy. Intraoral radiographs were performed predominantly for trauma, caries and apical diagnostics-reflecting general recommendations for the use of X-rays in children. For improved quality assurance and radiation protection, further studies are necessary to determine the meaningful dose reference level (DRL) for children.

Deconvoluting Cr states in Cr-doped UO2 nuclear fuels via bulk and single crystal spectroscopic studies.

Cr-doped UO2 is a leading accident tolerant nuclear fuel where the complexity of Cr chemical states in the bulk material has prevented acquisition of an unequivocal understanding of the redox chemistry and mechanism for incorporation of Cr in the UO2 matrix. To resolve this, we have used electron paramagnetic resonance, high energy resolution fluorescence detection X-ray absorption near energy structure and extended X-ray absorption fine structure spectroscopic measurements to examine Cr-doped UO2 single crystal grains and bulk material. Ambient condition measurements of the single crystal grains, which have been mechanically extracted from bulk material, indicated Cr is incorporated substitutionally for U+4 in the fluorite lattice as Cr+3 with formation of additional oxygen vacancies. Bulk material measurements reveal the complexity of Cr states, where metallic Cr (Cr0) and oxide related Cr+2 and Cr+32O3 were identified and attributed to grain boundary species and precipitates, with concurrent (Cr+3xU+41-x)O2-0.5x lattice matrix incorporation. The deconvolution of chemical states via crystal vs. powder measurements enables the understanding of discrepancies in literature whilst providing valuable direction for safe continued use of Cr-doped UO2 fuels for nuclear energy generation.

Effects of reducing excess dental adhesive on bacterial adhesion in the bracket periphery.

OBJECTIVES: White spot lesions are one of the most common side effects of orthodontic therapy with a multibracket appliance and may indicate a preliminary stage of caries, also known as initial caries. Several approaches may be utilized to prevent these lesions, such as reducing bacterial adhesion in the area surrounding the bracket. This bacterial colonization can be adversely affected by a number of local characteristics. In this context, the effects of excess dental adhesive in the bracket periphery were investigated by comparing a conventional bracket system with the APC flash-free bracket system. MATERIALS AND METHODS: Both bracket systems were applied to 24 extracted human premolars, and bacterial adhesion with Streptoccocus sobrinus (S. sobrinus) was performed for 24 h, 48 h, 7 d, and 14 d. After incubation, bacterial colonization was examined in specific areas by electron microscopy. RESULTS: Overall, significantly fewer bacterial colonies were found in the adhesive area around the APC flash-free brackets (n = 507 ± 13 bacteria) than the conventionally bonded bracket systems (n = 850 ± 56 bacteria). This is a significant difference (**p = 0.004). However, APC flash-free brackets tend to create marginal gaps with more bacterial adhesion in this area than conventional bracket systems (n = 265 ± 31 bacteria). This bacterial accumulation in the marginal-gap area is also significant (*p = 0.029). CONCLUSION: A smooth adhesive surface with minimal adhesive excess is beneficial for reducing bacterial adhesion but also poses a risk of marginal gap formation with subsequent bacterial colonization, which can potentially trigger carious lesions. CLINICAL RELEVANCE: To reduce bacterial adhesion, the APC flash-free bracket adhesive system with low adhesive excess might be beneficial. APC flash-free brackets reduce the bacterial colonization in the bracket environment. A lower number of bacteria can minimize white spot lesions in the bracket environment. APC flash-free brackets tend to form marginal gaps between the bracket adhesive and the tooth.

Frequency of Dental X-ray Diagnostics in Children and Adolescents: What Is the Radiation Exposure?

Children are exposed to ionizing radiation through radiographs during their development for various reasons. At present, there are no officially valid reference values for dental X-rays in children and adolescents for dental X-ray diagnostics. This study retrospectively examined 9680 extraoral dental radiographs in pediatric patients between 2002 and 2020. The aim was to analyze the radiation doses in pediatric patients, which indications were used, and whether there were specific age and gender differences. The evaluation showed that radiation doses were considered low, with dose area products of 2.2 cGy × cm2 for a lateral cephalogram, 14 cGy × cm2 for an orthopantomogram (OPG), and 45 cGy × cm2 for cone beam computer tomography (CBCT). This corresponds to an effective dose of 1.5 µSv for a lateral cephalogram, 7 µSv for an OPG, and 33.8 µSv for CBCT. Of the 9680 images, 78% were orthopantomograms, and only 0.4% were CBCT images. OPG has become more important over the years, as reflected in the indication. Approximately one-third of all extraoral exposures are orthodontic indications. Overall, the indications were similar for both genders. According to the dental indications, boys were X-rayed slightly more frequently than girls (54.5-45.5%). A future publication of dose guide values and corresponding guidelines is of high priority.

The nature of π-hole interactions between iodide anions and quinoid rings in the crystalline state.

The investigated co-crystal of 3-chloro-N-methylpyridinium iodide with tetrabromoquinone (3-Cl-N-MePy·I·Br4Q) reveals a π-hole interaction between an iodide anion and a quinoid ring involving an n → π* charge transfer. The quinoid ring has a partial negative charge (estimated to be in the range 0.08-0.11e) and a partial radical character, which is related to the black colour of the crystals (crystals of neutral tetrabromoquinone are yellow). A detailed X-ray charge density study revealed two symmetry-independent bond critical points between the iodide anions and carbon atoms of the ring. Their maximum electron density of 0.065 e Å-3 was reproduced by quantum chemical modelling. The energy of the interaction is estimated to be -11.16 kcal mol-1, which is comparable to the strength of moderate hydrogen bonding (about -10 kcal mol-1); it is dominantly electrostatic in nature, with a considerable dispersion component.

Shear Wave Elastography in Bruxism-Not Yet Ready for Clinical Routine.

Ultrasound shear wave elastography (SWE) is an emerging modality for the estimation of stiffness, but it has not been studied in relation to common disorders with altered stiffness, such as bruxism, which affects almost one-third of adults. Because this condition could lead to an increased stiffness of masticatory muscles, we investigated SWE in bruxism according to a proof-of-principle and feasibility study with 10 patients with known bruxism and an age- and gender-matched control group. SWE of the left and right masseter muscles was estimated under three conditions: relaxed jaw, 50% of the subjective maximal bite force, and maximal jaw opening. Rejecting the null hypothesis, SWE was significantly increased during relaxed jaw (bruxism 1.92 m/s ± 0.44; controls 1.66 m/s ± 0.24), whereas for maximal mouth opening, the result was vice versa increased with 2.89 m/s ± 0.93 for bruxism patients compared with 3.53 m/s ± 0.95 in the healthy control, which could be due to limited jaw movement in chronic bruxism patients (bruxism 4.46 m/s ± 1.17; controls 5.23 m/s ± 0.43). We show that SWE in bruxism is feasible and could be of potential use for diagnostics and monitoring, though we also highlight important limitations and necessary methodological considerations for future studies.

Refinement of anomalous dispersion correction parameters in single-crystal structure determinations.

Correcting for anomalous dispersion is part of any refinement of an X-ray dif-fraction crystal structure determination. The procedure takes the inelastic scattering in the diffraction experiment into account. This X-ray absorption effect is specific to each chemical compound and is particularly sensitive to radiation energies in the region of the absorption edges of the elements in the compound. Therefore, the widely used tabulated values for these corrections can only be approximations as they are based on calculations for isolated atoms. Features of the unique spatial and electronic environment that are directly related to the anomalous dispersion are ignored, although these can be observed spectroscopically. This significantly affects the fit between the crystallographic model and the measured intensities when the excitation wavelength in an X-ray diffraction experiment is close to an element's absorption edge. Herein, we report on synchrotron multi-wavelength single-crystal X-ray diffraction, as well as X-ray absorption spectroscopy experiments which we performed on the mol-ecular compound Mo(CO)6 at energies around the molybdenum K edge. The dispersive (f') and absorptive (f'') terms of the anomalous dispersion can be refined as independent parameters in the full-matrix least-squares refinement. This procedure has been implemented as a new feature in the well-established OLEX2 software suite. These refined parameters are in good agreement with the independently recorded X-ray absorption spectrum. The resulting crystallographic models show significant improvement compared to those employing tabulated values.