Potential complications of CAD/CAM-produced resin composite crowns on molars: A retrospective cohort study over four years.

PURPOSE: Evaluation of the clinical performance of computer-aided design/computer-aided manufacturing-produced resin composite crowns (CAD/CAM composite crowns) on molars with a particular focus on placement location. METHODS: A retrospective cohort study was performed based on the clinical records of patients with CAD/CAM composite crowns on molars (June 2016 to March 2021). The hazard ratios (HRs) and 95% confidence intervals (95% CIs) were estimated based the Cox proportional hazard model to evaluate the effect of tooth location on complication type and occurrence. Covariates included crown location (maxilla/mandible, distalmost tooth/not distalmost tooth, and first molar/second or third molar) and endodontically treated (nonvital) or untreated (vital) tooth. RESULTS: Overall, 362 crowns were evaluated (mean follow-up: 378 days, median: 286 days), and 106 crowns (29.3%) showed complications, most frequently crown debonding. The cumulative success and survival rates were 70.9% and 93.7%, respectively, after 1 year and 49.5% and 86.5%, respectively, after 3 years. There was no significant difference in the HRs and log-rank tests in the Kaplan-Meier curves based on crown location parameters (P > 0.05). However, placement on vital teeth was associated with higher risks than on nonvital teeth (HR, 1.55; 95% CI, 1.03-2.23). In addition, the cement as a covariate yielded a high HR. CONCLUSIONS: The location of CAD/CAM composite molar crowns is unlikely a risk factor for complications; therefore, these crowns can be clinically applied to all molars. However, the application of such molar crowns to vital teeth and the use of a cement other than adhesive resin cement present risks.

Corrigendum: A Glycosylphosphatidylinositol-Anchored α-Amylase Encoded by amyD Contributes to a Decrease in the Molecular Mass of Cell Wall α-1,3-Glucan in Aspergillus nidulans.

[This corrects the article DOI: 10.3389/ffunb.2021.821946.].

Clinical evaluation of monolithic zirconia crowns: a failure analysis of clinically obtained cases from a 3.5-year study.

PURPOSE: The primary purpose of this study was to examine the clinical performance of monolithic zirconia single crowns in terms of short-term failure or complications. The secondary purpose was to detect the originating flaws of clinically failed monolithic zirconia crowns to find the causes of failure. METHODS: A short-term prospective cohort study based on record evaluation and clinical examination of patients treated with tooth-supported monolithic zirconia crowns was performed in the Department of Fixed Prosthodontics, Tohoku University Hospital, Japan. The crowns were prepared during the follow-up period from April 2014 to July 2018. The 3.5-year cumulative success and survival rates were set as primary endpoints. Fractures of the crown or fragments were inspected under a scanning electron microscope for descriptive fractography. RESULTS: During the study period, 40 monolithic zirconia crowns were placed. Four crowns experienced clinical complications, including: 1) fracture of the crown (two crowns), 2) abrasion of the crown (one crown), and 3) fracture of the antagonist tooth (one crown). The estimated Kaplan-Meier 3.5-year success and survival rates were 90.5% (95% confi dence interval [CI]: 73.1-97.1) and 92.8% (95% CI: 74.1-98.3), respectively. Fractography revealed that all fractures were initiated from the wear phase on the occlusal surface. CONCLUSIONS: The results of this study suggest that the molar application of monolithic zirconia crowns requires detailed attention to interocclusal clearance and the restoration of the antagonist tooth.

A Glycosylphosphatidylinositol-Anchored α-Amylase Encoded by amyD Contributes to a Decrease in the Molecular Mass of Cell Wall α-1,3-Glucan in Aspergillus nidulans.

α-1,3-Glucan is one of the main polysaccharides in the cell wall of Aspergillus nidulans. We previously revealed that it plays a role in hyphal aggregation in liquid culture, and that its molecular mass (MM) in an agsA-overexpressing (agsAOE) strain was larger than that in an agsB-overexpressing (agsBOE) strain. The mechanism that regulates its MM is poorly understood. Although the gene amyD, which encodes glycosylphosphatidylinositol (GPI)-anchored α-amylase (AmyD), is involved in the biosynthesis of α-1,3-glucan in A. nidulans, how it regulates this biosynthesis remains unclear. Here we constructed strains with disrupted amyD (ΔamyD) or overexpressed amyD (amyDOE) in the genetic background of the ABPU1 (wild-type), agsAOE, or agsBOE strain, and characterized the chemical structure of α-1,3-glucans in the cell wall of each strain, focusing on their MM. The MM of α-1,3-glucan from the agsBOE amyDOE strain was smaller than that in the parental agsBOE strain. In addition, the MM of α-1,3-glucan from the agsAOE ΔamyD strain was greater than that in the agsAOE strain. These results suggest that AmyD is involved in decreasing the MM of α-1,3-glucan. We also found that the C-terminal GPI-anchoring region is important for these functions.

Draft genome sequence and nomenclature adjustment of Rhodococcus qingshengii CS98, a cesium-accumulating strain isolated in Japan.

Strains within the Rhodococcus genus have the ability to endure a range of recalcitrant compounds and metabolise a variety of pollutants. As a result there is increasing interest in these robust prokaryotes for their applications in bioremediation of contaminated environments and bioconversion of industrial wastes. In this announcement we present the draft genome sequence of R. qingshengii CS98, a soil isolate from Japan with the demonstrated ability to accumulate both stable and radioactive caesium.

Both Galactosaminogalactan and α-1,3-Glucan Contribute to Aggregation of Aspergillus oryzae Hyphae in Liquid Culture.

Filamentous fungi generally form aggregated hyphal pellets in liquid culture. We previously reported that α-1,3-glucan-deficient mutants of Aspergillus nidulans did not form hyphal pellets and their hyphae were fully dispersed, and we suggested that α-1,3-glucan functions in hyphal aggregation. However, Aspergillus oryzae α-1,3-glucan-deficient (AGΔ) mutants still form small pellets; therefore, we hypothesized that another factor responsible for forming hyphal pellets remains in these mutants. Here, we identified an extracellular matrix polysaccharide galactosaminogalactan (GAG) as such a factor. To produce a double mutant of A. oryzae (AG-GAGΔ), we disrupted the genes required for GAG biosynthesis in an AGΔ mutant. Hyphae of the double mutant were fully dispersed in liquid culture, suggesting that GAG is involved in hyphal aggregation in A. oryzae. Addition of partially purified GAG fraction to the hyphae of the AG-GAGΔ strain resulted in formation of mycelial pellets. Acetylation of the amino group in galactosamine of GAG weakened GAG aggregation, suggesting that hydrogen bond formation by this group is important for aggregation. Genome sequences suggest that α-1,3-glucan, GAG, or both are present in many filamentous fungi and thus may function in hyphal aggregation in these fungi. We also demonstrated that production of a recombinant polyesterase, CutL1, was higher in the AG-GAGΔ strain than in the wild-type and AGΔ strains. Thus, controlling hyphal aggregation factors of filamentous fungi may increase productivity in the fermentation industry.

A possible risk of CAD/CAM-produced composite resin premolar crowns on a removable partial denture abutment tooth: a 3-year retrospective cohort study.

PURPOSE: To evaluate the early performance of computer-aided design/computer-aided manufacturing (CAD/CAM)-produced composite resin crown (CAD/CAM composite crown) treatment on premolars, specifically, placement on a removable partial denture (RPD) abutment tooth, and the distalmost tooth in the dental arch, as possible clinical risk factors. METHODS: A retrospective cohort study (April 2014 to July 2017) was performed utilizing the clinical records of patients who received a premolar CAD/CAM composite crown treatment. The variables of time of treatment for (1) successful crowns (complication event-free) and (2) surviving crowns (clinically functional including re-luted) were estimated using Kaplan-Meier analysis. Survival distributions regarding "RPD abutment tooth" and "distalmost tooth" were analyzed with the log-rank test. Multilevel survival analyses were used to identify hazard ratios and associated risk factors. RESULTS: Five hundred and forty-seven crowns were evaluated (mean follow-up time 1.3±0.9years) in 327 patients. A total of 87 crowns had at least one complication, with loss of crown retention being the most common (70 crowns). Estimated success and survival rates at 3 years were 71.7% and 96.4%, respectively. The risk of complications was significantly higher for an RPD abutment tooth than for a non-RPD abutment tooth. There was no significant difference between the distalmost tooth and non-distalmost tooth in the dental arch. CONCLUSIONS: The demonstrated complication rate for CAD/CAM composite crowns placed on premolars was 15.9% over a period of up to 3 years. There was a substantial risk of complications with placement of such a crown on an RPD abutment tooth.

A thick frame decreases the fracture toughness of veneering ceramics used for zirconia-based all-ceramic restorations.

PURPOSE: To investigate the influence of firing condition and thickness of a yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) frame on the fracture toughness of veneering ceramics. METHODS: Layering and pressable ceramics without frames or on 0.8- and 1.2-mm-thick Y-TZP frames were fired with 5 schedules (normal and 4 customized conditions). The fracture toughness of the ceramics was measured at 0.5-2.5mm from the frame by the indentation fracture method. Crystal structures at the measurement points were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). RESULTS: Under customized firing conditions, the fracture toughness of the layering ceramic significantly decreased, particularly near the frame. Use of a 1.2-mm-thick frame significantly decreased the fracture toughness of both layering and pressable ceramics compared to ceramics without the frame. The decreased fracture toughness only occurred close (0.5 and 1.0mm) to the frame. XRD analysis showed identical diffraction patterns between points near and far from the frame, suggesting that the decreased fracture toughness was not due to crystal defects or impurities. SEM revealed many microcracks and large crystals in layering ceramic near the 1.2-mm-thick frame, possibly resulting from the thermal properties of the zirconia frame, such as large heat capacity and low thermal conductivity. CONCLUSIONS: Modification of the firing conditions from the manufacturer's instructions and inclusion of a thick Y-TZP frame decreased the fracture toughness of veneering ceramics at the interface, suggesting that a thick frame would pose a potent fracture risk in veneering ceramics used for zirconia-based all-ceramic restorations.

Molecular Mass and Localization of α-1,3-Glucan in Cell Wall Control the Degree of Hyphal Aggregation in Liquid Culture of Aspergillus nidulans.

α-1,3-Glucan is one of the main polysaccharides in the cell wall of filamentous fungi. Aspergillus nidulans has two α-1,3-glucan synthase genes, agsA and agsB. We previously revealed that AgsB is a major α-1,3-glucan synthase in vegetative hyphae, but the function of AgsA remained unknown because of its low expression level and lack of phenotypic alteration upon gene disruption. To clarify the role of α-1,3-glucan in hyphal aggregation, we constructed strains overexpressing agsA (agsAOE ) or agsB (agsBOE ), in which the other α-1,3-glucan synthase gene was disrupted. In liquid culture, the wild-type and agsBOE strains formed tightly aggregated hyphal pellets, whereas agsAOE hyphae aggregated weakly. We analyzed the chemical properties of cell wall α-1,3-glucan from the agsAOE and agsBOE strains. The peak molecular mass of α-1,3-glucan from the agsAOE strain (1,480 ± 80 kDa) was much larger than that from the wild type (147 ± 52 kDa) and agsBOE (372 ± 47 kDa); however, the peak molecular mass of repeating subunits in α-1,3-glucan was almost the same (after Smith degradation: agsAOE , 41.6 ± 5.8 kDa; agsBOE , 38.3 ± 3.0 kDa). We also analyzed localization of α-1,3-glucan in the cell wall of the two strains by fluorescent labeling with α-1,3-glucan-binding domain-fused GFP (AGBD-GFP). α-1,3-Glucan of the agsBOE cells was clearly located in the outermost layer, whereas weak labeling was detected in the agsAOE cells. However, the agsAOE cells treated with ß-1,3-glucanase were clearly labeled with AGBD-GFP. These observations suggest that ß-1,3-glucan covered most of α-1,3-glucan synthesized by AgsA, although a small amount of α-1,3-glucan was still present in the outer layer. We also constructed a strain with disruption of the amyG gene, which encodes an intracellular α-amylase that synthesizes α-1,4-glucooligosaccharide as a primer for α-1,3-glucan biosynthesis. In this strain, the hyphal pellets and peak molecular mass of α-1,3-glucan (94.5 ± 1.4 kDa) were smaller than in the wild-type strain, and α-1,3-glucan was still labeled with AGBD-GFP in the outermost layer. Overall, these results suggest that hyphal pellet formation depends on the molecular mass and spatial localization of α-1,3-glucan as well as the amount of α-1,3-glucan in the cell wall of A. nidulans.

Effect of finish line design on stress distribution in bilayer and monolithic zirconia crowns: a three-dimensional finite element analysis study.

This study evaluated the influence of different finish line designs and abutment materials on the stress distribution of bilayer and monolithic zirconia crowns using three-dimensional finite element analysis (FEA). Three-dimensional models of two types of zirconia premolars - a yttria-stabilized zirconia framework with veneering ceramic and a monolithic zirconia ceramic - were used in the analysis. Cylindrical models with the finish line design of the crown abutments were prepared with three types of margin curvature radius (CR): CR = 0 (CR0; shoulder margin), CR = 0.5 (CR0.5; rounded shoulder margin), and CR = 1.0 (CR1.0; deep chamfer margin). Two abutment materials (dentin and brass) were analyzed. In the FEA model, 1 N was loaded perpendicular to the occlusal surface at the center of the crown, and linear static analysis was performed. For all crowns, stress was localized to the occlusal loading area as well as to the axial walls of the proximal region. The lowest maximum principal stress values were observed when the dentin abutment with CR0.5 was used under a monolithic zirconia crown. These results suggest that the rounded shoulder margin and deep chamfer margin, in combination with a monolithic zirconia crown, potentially have optimal geometry to minimize occlusal stress.

Clinical evaluation of zirconia-based all-ceramic single crowns: an up to 12-year retrospective cohort study.

OBJECTIVES: This study aims to investigate the incidence of clinical complications with tooth-supported zirconia-based all-ceramic single crowns and identify pertinent risk parameters. MATERIALS AND METHODS: A retrospective cohort study (May 2004 to April 2016) utilizing clinical records of patients receiving yttrium-oxide-partially stabilized zirconia (Y-TZP)-based all-ceramic crowns placed at Tohoku University Hospital was performed. The length of time of treatment success (complication event-free) and restoration survival (including minor complication events and remaining clinically functional) were estimated using Kaplan-Meier analysis. Multilevel survival analysis was used to identify risk factors. RESULTS: One hundred thirty-seven crowns were evaluated (mean follow-up time, 7.0 years). A total of 21 crowns experienced at least one complication with fracture of veneering ceramic being the most common (16 crowns). Estimated success and survival rates at 5 years (96.9 and 98.5%, respectively) decreased at 10 years to 62.1 and 67.2%, respectively. The risk of complications was significantly higher for molar crowns compared to anterior crowns (p < 0.01). A significant association of complications with metal antagonist restorations was shown by univariate analysis (p < 0.01). CONCLUSIONS: Given the study limitations, Y-TZP single crowns placed on anterior teeth demonstrated encouraging clinical results over a period of up to 10 years. However, there is a substantial risk of complications with posterior teeth within 10 years of restoration placement. CLINICAL RELEVANCE: Treatment with zirconia-based all-ceramic crowns for molar teeth with metal antagonist occlusion should be undertaken with caution.

Three-dimensional finite element analysis of zirconia all-ceramic cantilevered fixed partial dentures with different framework designs.

The purpose of this study were: to perform stress analyses using three-dimensional finite element analysis methods; to analyze the mechanical stress of different framework designs; and to investigate framework designs that will provide for the long-term stability of both cantilevered fixed partial dentures (FPDs) and abutment teeth. An analysis model was prepared for three units of cantilevered FPDs that assume a missing mandibular first molar. Four types of framework design (Design 1, basic type; Design 2, framework width expanded buccolingually by 2 mm; Design 3, framework height expanded by 0.5 mm to the occlusal surface side from the end abutment to the connector area; and Design 4, a combination of Designs 2 and 3) were created. Two types of framework material (yttrium-oxide partially stabilized zirconia and a high precious noble metal gold alloy) and two types of abutment material (dentin and brass) were used. In the framework designs, Design 1 exhibited the highest maximum principal stress value for both zirconia and gold alloy. In the abutment tooth, Design 3 exhibited the highest maximum principal stress value for all abutment teeth. In the present study, Design 4 (the design with expanded framework height and framework width) could contribute to preventing the concentration of stress and protecting abutment teeth.

The chestnut blight fungus for studies on virus/host and virus/virus interactions: from a natural to a model host.

The chestnut blight fungus, Cryphonectria parasitica, is an important plant pathogenic ascomycete. The fungus hosts a wide range of viruses and now has been established as a model filamentous fungus for studying virus/host and virus/virus interactions. This is based on the development of methods for artificial virus introduction and elimination, host genome manipulability, available host genome sequence with annotations, host mutant strains, and molecular tools. Molecular tools include sub-cellular distribution markers, gene expression reporters, and vectors with regulatable promoters that have been long available for unicellular organisms, cultured cells, individuals of animals and plants, and certain filamentous fungi. A comparison with other filamentous fungi such as Neurospora crassa has been made to establish clear advantages and disadvantages of C. parasitica as a virus host. In addition, a few recent studies on RNA silencing vs. viruses in this fungus are introduced.

Fit of zirconia all-ceramic crowns with different cervical margin designs, before and after porcelain firing and glazing.

The purpose of this study is to investigate the fit of zirconia cores and all-ceramic crowns prepared with different cervical margin designs. The radius of curvature between the axial wall and the occlusal surface was set to 1 mm in an abutment using the cervical shoulder marginal design (S) and to 0.2 and 0.5 mm in abutments with round shoulders (0.2RS and 0.5RS, respectively). The internal gaps of the cores were 45-138 µm (S), 41-141 µm (0.2RS), and 43-133 µm (0.5RS). The internal gaps of the all-ceramic crowns were 40-115 µm (S), 45-113 µm (0.2RS), and 42-126 µm (0.5RS). There were no significant differences in one-way ANOVA for any region in any marginal design before and after firing the porcelain. The marginal gaps between the all-ceramic crowns and dies were 27 ± 25 (S), 30 ± 29 (0.2RS), and 24 ± 27 µm (0.5RS), again with no significant differences in one-way ANOVA.

An approach to medical knowledge sharing in a hospital information system using MCLink.

Clinicians often need access to electronic information resources that answer questions that occur in daily clinical practice. This information generally comes from publicly available resources. However, clinicians also need knowledge on institution-specific information (e.g., institution-specific guidelines, choice of drug, choice of laboratory test, information on adverse events, and advice from professional colleagues). This information needs to be available in real time. This study characterizes these needs in order to build a prototype hospital information system (HIS) that can help clinicians get timely answers to questions. We previously designed medical knowledge units called Medical Cells (MCs). We developed a portal server of MCs that can create and store medical information such as institution-specific information. We then developed a prototype HIS that embeds MCs as links (MCLink); these links are based on specific terms (e.g., drug, laboratory test, and disease). This prototype HIS presents clinicians with institution-specific information. The HIS clients (e.g., clinicians, nurses, pharmacists, and laboratory technicians) can also create an MCLink in the HIS using the portal server in the hospital. The prototype HIS allowed efficient sharing and use of institution-specific information to clinicians at the point of care. This study included institution-specific information resources and advice from professional colleagues, both of which might have an important role in supporting good clinical decision making.

Functional analysis of the α-1,3-glucan synthase genes agsA and agsB in Aspergillus nidulans: agsB is the major α-1,3-glucan synthase in this fungus.

Although α-1,3-glucan is one of the major cell wall polysaccharides in filamentous fungi, the physiological roles of α-1,3-glucan remain unclear. The model fungus Aspergillus nidulans possesses two α-1,3-glucan synthase (AGS) genes, agsA and agsB. For functional analysis of these genes, we constructed several mutant strains in A. nidulans: agsA disruption, agsB disruption, and double-disruption strains. We also constructed several CagsB strains in which agsB expression was controlled by the inducible alcA promoter, with or without the agsA-disrupting mutation. The agsA disruption strains did not show markedly different phenotypes from those of the wild-type strain. The agsB disruption strains formed dispersed hyphal cells under liquid culture conditions, regardless of the agsA genetic background. Dispersed hyphal cells were also observed in liquid culture of the CagsB strains when agsB expression was repressed, whereas these strains grew normally in plate culture even under the agsB-repressed conditions. Fractionation of the cell wall based on the alkali solubility of its components, quantification of sugars, and (13)C-NMR spectroscopic analysis revealed that α-1,3-glucan was the main component of the alkali-soluble fraction in the wild-type and agsA disruption strains, but almost no α-1,3-glucan was found in the alkali-soluble fraction derived from either the agsB disruption strain or the CagsB strain under the agsB-repressed conditions, regardless of the agsA genetic background. Taken together, our data demonstrate that the two AGS genes are dispensable in A. nidulans, but that AgsB is required for normal growth characteristics under liquid culture conditions and is the major AGS in this species.

Mechanical properties of hard resins for crowns and bridges.

PURPOSE: Hard resins for crowns and bridges are widely used for esthetic restorations. The objective of this study was to evaluate the mechanical properties of new commercial hard resins and to compare the results with those of the other hard resins previously investigated. METHODS: Dentin and enamel made with two new hard resins (Epricord: EP, Kuraray, Co., Ltd., Osaka, Japan and Prossimo: PR, GC, Co., Ltd., Tokyo, Japan) were used in this study. Regarding the fundamental characteristics, the thermal expansion/shrinkage coefficient, the filler content, the polymerization shrinkage, and the wear were examined. Regarding the strength of resin, the bending strength, hardness, compression strength, elastic modulus, and fracture strength of a jacket crown were measured. RESULTS: These resins showed comparatively lower levels than the other hard resins regarding the bending strength, hardness, compression strength, and fracture strength of the jacket crown. The total filler content rate and wear amount of these resins exhibited similar values to those of the other resins. The thermal expansion/ shrinkage coefficients of these resins exhibited higher values than those of the other resins. EP showed a different tendency from PR about the compression strength, elastic modulus, and polymerization shrinkage. CONCLUSIONS: PR and EP did not show dramatically better physical properties. However, the results of each examination in this study may be acceptable clinically. The results of each investigation changed according to the products used, and proper use for each case and application was suggested.

Quantitative evaluation of axial wall taper in prepared artificial teeth.

The purpose of this study was to quantitatively evaluate the axial wall taper of prepared artificial teeth using a non-contact three-dimensional shape measuring system. A total of 54 artificial teeth prepared by pre-clinical dental students for complete cast restorations were evaluated. For quantitative analysis, five cross sections were computer-graphically placed perpendicularly to the z-axis. The surface coordinate values (x, y, z) of each cross section were converted into polar coordinate values (r, theta), which were then graphically rendered to a two-dimensional plane. At four points, each 90 degrees from the distal center point of the cross section, the axial wall taper was quantitatively calculated using a formula based on the differences in radius between the highest and lowest positions of the cross sections of the prepared tooth. The average calculated taper was 5.8 degrees in the distal region, 21.7 degrees in the buccal region, 14.9 degrees in the mesial region and 12.5 degrees in the lingual region. These results suggest that the axial wall taper of prepared teeth can be quantitatively evaluated using this measuring system.

An ordered collection of expressed sequences from Cryphonectria parasitica and evidence of genomic microsynteny with Neurospora crassa and Magnaporthe grisea.

Cryphonectria parasitica, the causative agent of chestnut blight, has proven to be a tractable experimental system for studying fungal pathogenesis. Moreover, the development of infectious cDNA clones of C. parasitica hypoviruses, capable of attenuating fungal virulence, has provided the opportunity to examine molecular aspects of fungal plant pathogenesis in the context of biological control. In order to establish a genomic base for future studies of C. parasitica, the authors have analysed a collection of expressed sequences. A mixed cDNA library was prepared from RNA isolated from wild-type (virus-free) and hypovirus-infected C. parasitica strains. Plasmid DNA was recovered from individual transformants and sequenced from the 5' end of the insert. Contig analysis of the collected sequences revealed that they represented approximately 2200 individual ORFs. An assessment of functional diversity present in this collection was achieved by using the BLAST software utilities and the NCBI protein database. Candidate genes were identified with significant potential relevance to C. parasitica growth, development, pathogenesis and vegetative incompatibility. Additional investigations of a 12.9 kbp genomic region revealed microsynteny between C. parasitica and both Neurospora crassa and Magnaporthe grisea, two closely related fungi. These data represent the largest collection of sequence information currently available for C. parasitica and are now forming the basis of further studies using microarray analyses to determine global changes in transcription that occur in response to hypovirus infection.