Direct hemoperfusion using a polymyxin B-immobilized polystyrene column for COVID-19.

OBJECTIVE: To evaluate the efficacy and safety of direct hemoperfusion using a polymyxin B-immobilized polystyrene column (PMX-DHP) in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-positive pneumonia patients. METHODS: This study was a case series conducted at a designated infectious diseases hospital. Twelve SARS-CoV-2-positive patients with partial pressure of arterial oxygen/percentage of inspired oxygen (P/F) ratio < 300 were treated with PMX-DHP on two consecutive days each during hospitalization. We defined day 1 as the first day when PMX-DHP was performed. PMX-DHP efficacy was assessed on days 7 and 14 after the first treatment based on eight categories. Subsequently, improvement in P/F ratio and urinary biomarkers on days 4 and 8, malfunctions, and ventilator and extracorporeal membrane oxygenation avoidance rates were also evaluated. RESULTS: On day 14 after the first treatment, disease severity decreased in 58.3% of the patients. P/F ratio increased while urine ß2-microglobulin decreased on days 4 and 8. Cytokine measurement pre- and post-PMX-DHP revealed decreased levels of interleukin-6 and the factors involved in vascular endothelial injury, including vascular endothelial growth factor. Twenty-two PMX-DHPs were performed, of which seven and five PMX-DHPs led to increased inlet pressure and membrane coagulation, respectively. When the membranes coagulated, the circuitry needed to be reconfigured. Circuit problems were usually observed when D-dimer and fibrin degradation product levels were high before PMX-DHP. CONCLUSIONS: Future studies are expected to determine the therapeutic effect of PMX-DHP on COVID-19. Because of the relatively high risk of circuit coagulation, coagulation capacity should be assessed beforehand.

Comparison of olfactory and gustatory disorders in Alzheimer's disease.

Patients with Alzheimer's disease (AD) develop olfactory and gustatory disorders. However, the order of failure and relevance of the pathophysiology are unclear. We compared olfactory identification and whole mouth gustation in patients with AD to those with mild cognitive impairment (MCI) and to healthy controls (HC) and assessed correlations with pathophysiology. Patients with AD (n = 40), MCI (n = 34), and HC (n = 40) were recruited. We performed the Odor Stick Identification Test for Japanese (OSIT-J), gustatory test by the intraoral dropping method using taste solutions, Mini-Mental State Examination (MMSE), Alzheimer's Disease Assessment Scale-cognitive subscale Japanese version (ADAS-J cog), Touch Panel-type Dementia Assessment Scale (TDAS), and measurement of amyloid ß (Aß) 42 and phosphorylated tau (p-tau) 181 levels in cerebrospinal fluid (CSF). Patients with AD and MCI had lower OSIT-J scores than did the HC. The OSIT-J score was correlated with the MMSE, ADAS-J cog, TDAS, and Aß42 results. There were no significant differences in the gustatory test scores among the three groups. The gustatory test score was only correlated with the MMSE, ADAS-J cog, and TDAS results. Olfactory function decreased in AD and MCI patients and was associated with CSF biomarker levels and cognitive disorders. The results suggest that olfactory function is impaired in early stage of AD. Gustatory function was not correlated with CSF biomarkers, which suggests that it may not be impaired in early stage of AD.

A modified indirect method for fabricating silicone soft-lined complete dentures.

A method is described of polymerizing silicone soft lining materials with a hard acrylic resin base by using a photoactivated spacer. The use of a photoactivated spacer is convenient because of the ease in determining the correct location covering the attached mucosa but not extending to the border margins. By using this method, the optimum shape and thickness of the spacer can also be ensured. Thus, the long-term durability of soft lining dentures is achieved without invasion by microorganisms or peeling away from the denture margin.

[Survey of Dental Treatment Situation and Needs for Prostheses in Veterinary Practice].

PURPOSE: In today's society, pets have become important members of families since they give mental peace and healing to families. Although veterinary dentistry is recognized to be essential for animal health, there are few reports on dental treatments of animals and the relationship between veterinarians and dental technicians. The purpose of the present study was to clarify the current situation of dental treatments of animals and to discuss the involvement of dental technicians in veterinary dental treatments and their collaboration with veterinarians. METHODS: Anonymous self-administered questionnaires were mailed to 16 university hospitals for animals, 17 animal clinics, and 87 zoological gardens, and handed out to 36 participants at the oral disease seminar organized by Nippon Animal Hospital Association. The questionnaires included questions on veterinary dental treatments, ways to learn veterinary dentistry, and details of prosthodontic treatments. RESULTS: Eighty-two valid responses (51.3%) were obtained. While 93.8% of veterinarians recognized the need for veterinary dental treatments, 67.9% were actually implementing dental treatments. Only 23.5% of veterinarians who conducted dental treatments experienced prosthodontic treatments, and the major prostheses used for treatments were fillings and crowns. Most veterinarians had fewer opportunities to acquire knowledge and skills about dental treatments. In addition, the recognition of dental technicians and their specialties was low among veterinarians. CONCLUSION: The results suggested that the dental technician, as a member of a multi-disciplinary team, can contribute to animal health by providing prosthetic appliances and should make efforts to enhance awareness of their specialty.

Effect of denture adhesives on masticatory performance: Multicenter randomized controlled trial.

PURPOSE: The purpose of this study is to investigate the effects of denture adhesives on masticatory performance via a 10-center, parallel, randomized, controlled trial of complete denture wearers in Japan. METHODS: The trial was conducted between September 2013 and October 2016. The inclusion criteria were complete edentulism, willingness to undergo new complete denture treatment, and willingness to return for recall treatment. The exclusion criteria were age 90 years or older, presence of severe systemic illness, inability to understand the questionnaires, wearing metal base complete dentures, denture adhesive user, wearing prosthetics for maxillofacial defects, wearing complete dentures with tissue conditioners, and severe xerostomia. Randomization of the powder-type denture adhesive (powder), cream-type denture adhesive (cream), and control (saline) groups was performed using a sealed envelope system. Masticatory performance was measured using color-changeable chewing gum. Intervention blinding was not feasible. RESULTS: Sixty-seven control, 69 powder, and 64 cream participants are analyzed using the intention-to-treat principle. The participants in all groups show significantly improved masticatory performance at post-intervention (paired t-test with Bonferroni correction P < 0.0001). However, no significant difference in masticatory performance is detected among the three groups (one-way analysis of variance). A significant negative correlation between pre- and post-changes in masticatory performance and intraoral condition scores is observed (Pearson's correlation coefficient, P < 0.0001). CONCLUSIONS: Although denture adhesives improved the masticatory performance of complete denture wearers, their clinical effects are comparable to those of saline solution. The use of denture adhesives is more effective in complete denture wearers with unsatisfactory intraoral conditions.

Discoloration of fiber-reinforced composite resin disc for computer-aided design/computer-aided manufacturing after immersion in coffee and curry solutions.

The purpose of this study was to clarify the discoloration of fiber-reinforced composite resin (FRC) disc materials. The color differences (ΔEs) of three CAD/CAM disc materials, FRC with different fiber orientations, composite resin, and polyether-ether-ketones were evaluated after month-long immersion in water, coffee, and curry. The ΔEs of all materials after coffee and curry immersion increased with increasing immersion periods, while those after water immersion barely increased. FRC exhibited a smaller color difference and water sorption value than composite resin and a greater color difference and water sorption value than polyether-ether-ketones. The ΔEs after coffee immersion were significantly correlated with the water sorption value. The ΔE of FRC with fiber orientations perpendicular to the surface was greater than that of FRC with fiber orientations parallel to the surface, likely due to greater exposure of the matrix-fiber interface. This result suggested that the fiber orientations of FRC affected the discoloration.

Effects of build orientation and bar addition on accuracy of complete denture base fabricated with digital light projection: An in vitro study.

PURPOSE: We evaluated the effects of build orientation and bar addition between lingual flanges on the accuracy of mandibular denture bases fabricated using a digital light processing (DLP) device. METHODS: Mandibular denture bases with and without a bar at the lingual flanges were virtually designed and assigned to eight build orientations. Six dentures per condition were fabricated using a DLP device with a methacrylate-based photopolymerizable monomer (Dima Print denture base) (n=96). The fabricated denture surfaces were digitized, and intaglio surfaces were obtained. These digitized surfaces were compared via superimposition using graphical software (Artec studio12 profession) to their original designed files, and root mean square estimates were obtained. The trueness of the entire and intaglio data was statistically analyzed non-parametrically. RESULTS: The range of trueness of the entire and intaglio denture bases was 0.15-0.31 mm and 0.11-0.38 mm, respectively. The trueness at 135° and 270° for the entire denture base and that at 270° for the intaglio data without the bar were significantly lower than those for the other build orientations. The trueness at 270° was <0.15 mm irrespective of the conditions. The trueness with the bar of all build orientations, except that of 0° for intaglio data, was significantly smaller than or equal to the trueness without the bar of the corresponding build orientations. CONCLUSIONS: Build orientation and bar addition influenced the accuracy of the complete dentures fabricated using DLP. A build orientation of 270° is recommended for fabricating a mandibular complete denture, irrespective of the bar addition.

Effects of denture adhesives on denture retention and occlusal forces in complete denture wearers: A multicenter, randomized controlled trial.

PURPOSE: This study aimed to determine the effects of denture adhesives on denture retention and occlusal force in complete denture wearers in a multicenter, randomized, parallel-group controlled trial. METHODS: Two hundred edentulous patients wearing complete dentures were allocated to three groups: powder-type denture adhesive, cream-type denture adhesive, and control (saline solution). Denture adhesives and saline solution were applied to the dentures for 4 days. The retentive force of the dentures and occlusal force were measured using a force transducer occlusal force meter at baseline and after 4 days of intervention. In addition to between-group comparisons, subgroup analyses of denture retention and occlusal force were performed based on the level of difficulty of the edentulism treatment. The levels were ranked as I (easy), II, III, and IV (difficult). RESULTS: Cream-type denture adhesives significantly improved the retentive force of the dentures (P<0.01) and occlusal force (P<0.05), with no significant differences between baseline and post-intervention forces in the powder-type denture adhesive and control groups. In within-group comparisons, cream-type denture adhesives improved both the retentive and occlusal forces at Level II (P<0.05), and powder-type denture adhesives improved the occlusal force at Level II (P<0.01). CONCLUSIONS: Application of cream-type denture adhesives effectively improves the denture retention and occlusal force in complete denture wearers with a moderate degree of difficulty during edentulism treatment.

Genetic association of IL17 and the importance of ABO blood group antigens in saliva to COVID-19.

The outbreak of COVID-19 caused by infection with SARS-CoV-2 virus has become a worldwide pandemic, and the number of patients presenting with respiratory failure is rapidly increasing in Japan. An international meta-analysis has been conducted to identify genetic factors associated with the onset and severity of COVID-19, but these factors have yet to be fully clarified. Here, we carried out genomic analysis based on a genome-wide association study (GWAS) in Japanese COVID-19 patients to determine whether genetic factors reported to be associated with the onset or severity of COVID-19 in the international meta-GWAS are replicated in the Japanese population, and whether new genetic factors exist. Although no significant genome-wide association was detected in the Japanese GWAS, an integrated analysis with the international meta-GWAS identified for the first time the involvement of the IL17A/IL17F gene in the severity of COVID-19. Among nine genes reported in the international meta-GWAS as genes involved in the onset of COVID-19, the association of FOXP4-AS1, ABO, and IFNAR2 genes was replicated in the Japanese population. Moreover, combined analysis of ABO and FUT2 genotypes revealed that the presence of oral AB antigens was significantly associated with the onset of COVID-19. FOXP4-AS1 and IFNAR2 were also significantly associated in the integrated analysis of the Japanese GWAS and international meta-GWAS when compared with severe COVID-19 cases and the general population. This made it clear that these two genes were also involved in not only the onset but also the severity of COVID-19. In particular, FOXP4-AS1 was not found to be associated with the severity of COVID-19 in the international meta-GWAS, but an integrated analysis with the Japanese GWAS revealed an association with severity. Individuals with the SNP risk allele found between IL17A and IL17F had significantly lower mRNA expression levels of IL17F, suggesting that activation of the innate immune response by IL17F may play an important role in the severity of SARS-CoV-2 infection.

Multivariate analysis reveals oral health-related quality of life of complete denture wearers with denture adhesives: a multicenter randomized controlled trial.

Purpose To investigate the difference in improvement of oral health-related quality of life (OHR-QoL) depending on the oral and denture conditions of a complete denture wearer when using a cream or powder type denture adhesive in a 10-center parallel randomized clinical trial.Methods Two hundred edentulous subjects who wore complete dentures were allocated to each of the three groups according to denture adhesive type: cream, powder, and control (saline solution). The materials were applied to the mucosal surface of the dentures for 4 days, and baseline data and data after the intervention were collected. OHR-QoL was assessed using the Japanese version of the modified Oral Health Impact Profile for Edentulous Patients (OHIP-EDENT-J) scale for outcome. Multivariate analysis was used to investigate improvements in OHR-QoL according to participant characteristics among complete denture wearers using these materials.Results OHIP-EDENT-J scores were significantly decreased in all groups after the intervention (p < 0.05); however, there were no statistically significant differences among the groups. Multiple logistic regression analysis revealed a significant association between the vertical height of the maxillary and mandibular alveolar ridge and OHIP-EDENT-J scores in the cream-type denture adhesive group. In contrast, there were no significant association between participant characteristics and OHIP-EDENT-J scores in the powder-type adhesive and control groups.Conclusions The use of denture adhesives could improve OHR-QoL for complete denture wearers. The cream-type denture adhesives may be expected to improve OHR-QoL in patients with poor residual ridge conditions compared with patients with good residual ridge conditions.

Morphologic classification and stress analysis of the mandibular bone in the premolar region for implant placement.

PURPOSE: The objective of this study was to assess the influence of mandibular morphology on the stress and strain distributions in the bone supporting an implant. MATERIALS AND METHODS: Subjects were selected from patients with missing mandibular premolar teeth. Computed tomographic scans of the premolar region were classified into nine groups based on the overall bone morphology and the relative position of the alveolar crest. Finite element models of the bone on the basis of this classification, with inserted implants and superstructures, were constructed. A load of 200 N applied 30 degrees buccal from the vertical axis was directed toward the occlusal surface. RESULTS: One hundred two partially (n = 98) and completely (n = 4) edentulous subjects were recruited. Their ages ranged from 40 to 79 years (mean age, 60.5 years; 41 men and 61 women). Approximately 56% of the patients showed bone widening in the caudal direction. The maximum compressive stresses were shown in the lingual cervical regions. An influence of overall bone morphology on stress distribution was not observed; however, the alveolar crest contour clearly affected the maximum stress and strain values. Compressive microstrain above 4,000 was observed only when the alveolar crest was lingually located relative to the body of the mandible. These high strain levels were concentrated at the lingual cervical margin, with volumes ranging from 0.04 to 0.07 mm3. CONCLUSION: The contour of the alveolar crest potentially plays a critical role in maintaining the bone levels surrounding implants.

Reduction in maxillary complete denture deformation using framework material made by computer-aided design and manufacturing systems.

The aim of this study was to investigate the effects of framework materials manufactured by dental CAD/CAM systems on complete denture deformation. Four materials were used for the maxillary complete denture framework: fiber-reinforced composite (FRC), nano-zirconia (N-Zr), cobalt-chromium-molybdenum alloy (CCM), and polyether-ether-ketone (PEEK). The framework materials were prepared using CAD/CAM systems. Six dentures of each material were fabricated, using polymethyl-methacrylate (PMMA) as a control. The thickness of the palatal area was 1.0 mm for PMMA and PEEK and 0.5 mm for FRC, N-Zr, and CCM. The denture deformation during occlusal load was monitored using four rosette strain gauges placed on the midline of the denture. The maximum principal strain (MPS) of each gauge, except that at the labial frenum, increased proportionally with increasing applied load. The directions of MPS were predominantly perpendicular to the midline of the denture. When a 200-N load was applied, the MPS at the incisive papilla in N-Zr and CCM was half that of PMMA; there was no significant difference among MPSs of PEEK, PMMA and FRC. The MPS at the end point of the denture in FRC, N-Zr, and CCM was significantly smaller than that of PMMA. The MPSs of the complete denture decreased when the CAD/CAM fabricated framework was used. The effects of the CAD/CAM fabricated framework on complete denture deformation varied due to the material used; however, a CAD/CAM fabricated framework material is considered to be effective for reducing complete denture deformation.

Chairside fabrication of provisional crowns on FDM 3D-printed PVA model.

PURPOSE: The purpose of this study was to evaluate the dimensional accuracy of crowns fabricated using a polyvinyl alcohol (PVA) dental model. METHODS: An intraoral scanner (LAVA TDS) was used to scan a prepared molar abutment as a master model. The STL file obtained from the scanning process was transferred into the FDM 3D printer (Value 3D Magix MF-1000) and then models were fabricated with PVA filament. In order to compare with the conventional method, an impression of the master model was taken using silicone impression material to fabricate the conventional stone cast model (Conv). An indirect resin composite (Gradia) and self-cured acrylic resin (Curergrace) were used to fabricate crowns (n = 20) according to the manufacturer's instructions. Surface accuracy of the Conv and PVA models and internal accuracy of the crowns set on the models were measured using two methods; 3D digital analysis and silicon-fitting evaluation. Statistical analysis of the results was done using t-test and Willcoxon signed rank test with Bonferroni correction at 5% significance. RESULTS: Digital analysis showed the Root Mean Square (RMS) value of PVA model surface was higher than that of Conv, while there was no significant difference between the two crown materials. However, the silicon-fitting analysis showed marginal discrepancy of crowns fabricated on PVA model were within 100 µm. CONCLUSION: 3D printed PVA model can be used for chairside crown fabrication with an acceptable accuracy.

Effect of denture adhesives on oral moisture: A multicenter randomized controlled trial.

PURPOSE: The purpose of this study was to investigate the effect of denture adhesives on oral moisture in a 10-center parallel randomized clinical trial. METHODS: Two hundred edentulous subjects wearing complete dentures were allocated into three groups: cream-type adhesive, powder-type adhesive and control groups. The adhesives (and saline solution in the control group) were applied to the mucosal surface of the dentures for 4 days, and baseline data and data after the intervention for eight meals over 4 days were obtained. For the main outcome, oral moisture was measured with a moisture checking device. Secondary outcomes were denture satisfaction, masticatory performance, denture retention, and occlusal force. In addition to between-group and within-group comparisons of oral moisture, investigations for secondary outcomes were undertaken in subgroups classified according to the degree of oral moisture at baseline (normal subgroup and dry mouth subgroup). Intention-to-treat analysis was also performed. RESULTS: Between-group and within-group comparisons of oral moisture showed no significant differences. The cream-type and powder-type denture adhesives were significantly effective in the dry mouth group for denture satisfaction ratings of ability to masticate, stability, retention, and comfort of mandibular dentures (p<0.05). The masticatory performance and retentive force of the dry mouth denture adhesive using groups were significantly improved after intervention (p<0.05). CONCLUSIONS: The oral moisture of complete denture wearers was not influenced by the use of denture adhesives. Our findings showed that denture adhesives improved subjective denture satisfaction, masticatory performance, and retention for complete denture patients with oral dryness.

Effect of bending on the mechanical properties of gold wrought-wire clasps: a non-linear finite element analysis.

The purpose of this study was to assess the effect of bending of dental gold alloy wires on the mechanical characteristics of wrought-wire clasps. We conducted a simulation of large deformation in straight wires by means of non-linear finite element (FE) analysis. A bending force increased the principal tensile stress on the outer surface of the bending corner and the compressive stress on the inner surface of the bending corner to their maximum values. After unloading with springback, a residual tensile stress was produced on the inner surface. A gold alloy wire clasp exhibited a relatively greater flexibility with small permanent deformation after the clasp tip deflection as compared to previously reported data for Co-Cr wires; this suggests that it is suitable for periodontally compromised teeth. Wire clasps are more susceptible to failure as compared to straight wrought wires because of the residual stress produced during the bending process.

Micropatterning of a 2-methacryloyloxyethyl phosphorylcholine polymer surface by hydrogenated amorphous carbon thin films for endothelialization and antithrombogenicity.

The existing first-generation drug-eluting stent (DES) has caused late and very late stent thrombosis related to incomplete stent endothelialization. Hence, biomaterials that possess sufficient anti-thrombogenicity and endothelialization with the controlled drug release system have been highly required. In this work, we have developed a newly designed drug-release platform composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, a non-thrombogenic polymer, and micropatterned hydrogenated amorphous carbon (a-C:H), a cell-compatible thin film. The platelet adhesion and the endothelial cell adhesion behavior on the micropatterned substrates were investigated in vitro. The results indicated that the micropatterned a-C:H/MPC polymer substrates effectively supported the human umbilical vein endothelial cell (HUVEC) proliferation, while suppressing the platelet adhesion. Interestingly, the HUVEC exhibited different shape and behavior by changing the island size of the micropatterned a-C:H. By introducing both a non-thrombogenic polymer and cell-compatible thin films through a simple patterning method, we demonstrated that the platform had the potential to be utilized as a base material for DES with cell controllability. STATEMENT OF SIGNIFICANCE: The current first-generation drug-eluting stents (DES) would cause late and very late stent thrombosis due to the incomplete endothelialization of the metal stent material. In this work, we have developed a new DES platform composed of a 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer micropatterned by hydrogenated amorphous carbon (a-C:H). Two types of differently micropatterned a-C:H stent surface were made. Our studies revealed that the micropatterned a-C:H/MPC polymer substrates could effectively enhance the endothelial cell (EC) proliferation, simultaneously suppressing the platelet adhesion, becoming a highly biocompatible material especially for indwelling devices including a drug-release device. The new drug-release platform could be utilized as a base material for cell-controllable coating on DES.

Effects of number of metal restorations and mandibular position during computed tomography imaging on accuracy of maxillofacial models.

PURPOSE: Computed tomography (CT) imaging for three-dimensional (3D) printed models may improve the quality of surgical preoperative plans. Although metal objects can cause artifacts in CT images, integration of CT and digital dental arch imaging may solve this problem. The present study aimed to evaluate effects of the number of metal restorations and mandibular position during CT imaging on accuracy of reproduced models. METHODS: Stereolithography datasets from three sets of dental models having different numbers of metal restorations were obtained using a laboratory digitizing device (control) and CT equipment (nonintegrated data). CT scanning was performed under two conditions: intercuspal position (closed) and separated using paraffin wax (open). Nonintegrated data after metal artifact removal were separated into maxillary and mandibular dentition groups. The occlusal part of the control dentition and nonintegrated data were superimposed and integrated (integrated data). The root mean square (RMS) between the control and stereolithography data was calculated and analyzed with three-way analysis of variance and t-test with Bonferroni correction. RESULTS: Increasing numbers of metal restorations resulted in increase in metal artifacts and RMS values. Moreover, the RMS of the closed dataset was significantly greater than that of the open dataset because of the creation of artificial occlusal surfaces. The RMSs of the integrated datasets were significantly smaller than those of the nonintegrated datasets, except for the open model without metal restorations. CONCLUSIONS: Accuracies of reproduced maxillary and mandibular models decreased with increasing numbers of metal restorations and in the closed mandibular position during CT scanning.

The development of new image receptor-holding instruments with appropriate horizontal X-ray beam angulation for periapical radiographs.

OBJECTIVES: This study aimed to develop new image receptor-holding instruments with appropriate horizontal X-ray beam angulation, based on the anatomical data of posterior region interproximal surfaces derived from archived CT images. METHODS: CT images of 92 patients with sound upper and lower dental arches were collected from our CT database and analyzed to determine the angles between the tangential interproximal contact line and the central groove line of posterior teeth. The average angle for each site was calculated and used to modify instruments using a three-dimensional printer. The utilities of the conventional and the modified instruments for viewing proximal surfaces were compared using two dry skulls. RESULTS: The right and left sides of each site, except for the lower second premolar and first molar sites, did not differ significantly. The difference between the sites was 2.0°; hence, we calculated mean values for the two sides at each site. In the maxilla, the angles of the first and second premolar, second premolar and first molar, and first and second molar to the groove line were 83.9° (±5.4°), 84.4° (±3.9°), 81.6° (±5.1°), while those in the mandible were 85.0° (±9.2°), 85.0° (±4.0°), and 90.6° (±4.9°), respectively. The holding instruments modified to 80° demonstrated better proximal viewing ability in the upper molar region than conventional instruments. CONCLUSIONS: The mean angles of the interproximal surfaces were determined from CT data. The image receptor holding-instruments were modified according to these angles to allow appropriate X-ray angulation, which facilitated improved observation of the proximal surfaces of teeth in the posterior region in this pilot in vitro study.

Effect of fiberglass orientation on flexural properties of fiberglass-reinforced composite resin block for CAD/CAM.

A fiberglass-reinforced composite resin (FRP) block using a plain woven fiberglass sheet for CAD/CAM has been introduced in dental practice. The aim of the present study was to evaluate the effects of the fiberglass sheet orientation on the flexural properties of an FRP block. The flexural properties of five types of fiberglass sheet-assigned specimens were examined using a three-point bending test. A one-way analysis of variance revealed that the orientation of fiberglass sheet significantly influenced the flexural strength, 0.2% yield strength, and flexural modulus. The values of the flexural properties of the FRP were the largest when the fiberglass sheets were perpendicular to the applied force, and the smallest when the fiberglass was parallel to the same. The flexural properties of the FRP block were anisotropic and they were significantly influenced by the orientation of fiberglass sheet.

Evaluation of mechanical properties of new elastomer material applicable for dental 3D printer.

PURPOSE: Digital technology has advanced and changed clinical dentistry. The utility of various thermoplastic materials for 3D dental printing has not been thoroughly explored. The aim of this study was to evaluate mechanical properties of a new thermoplastic elastomer material applicable for a dental 3D printer. MATERIAL & METHOD: Three thermoplastic elastomers: ABS, PLA and an acrylic block copolymer (KUR) and a dental self-curing resin (PMMA) were used in this study. Physical properties were evaluated by measuring water sorption (WS), dimensional accuracy (DA), ultimate tensile strength (UTS) and shear bond strength (SBS) to PMMA. For WS and DA, specimens were measured by weight and length, respectively after desiccation and immersion in 37 °C distilled water for 1 day, 1 week and 1 month. For UTS, the specimens were prepared according to ISO 527-2-5A and loaded to test the UTS at a crosshead speed of 5 mm/min after storage in 37 °C distilled water for 24 h and 1 month. For SBS, MMA self-curing resin was filled in a Teflon ring which was mounted onto polished specimens to make the adhesive area. The prepared specimens were tested for SBS after storage in 37 °C distilled water for 24 h and 37 °C distilled water for 24 h followed by 10000 times thermal cycling. The data were analyzed by repeated measures ANOVA, two-way ANOVA and t-test with Bonferroni correction at 95% confidence level. RESULT: The WS value of PMMA was significantly higher than those of the other materials after 1 day (p < 0.05), while the WS values of KUR were significantly higher than those of the other materials after 1 week and 1 month (p < 0.05). The DA values were influenced by water storage periods except for KUR. There were no significant differences among ABS, PLA and PMMA in SBS before thermal cycling (p > 0.05). The SBS of KUR was the lowest among the materials before thermal cycling (p < 0.05). However, there was no significant difference between PMMA and KUR after thermal cycling (p > 0.05). CONCLUSION: The acrylic block copolymer demonstrated acceptable physical properties, suggesting the potential to be a material to make provisional restorations for a dental 3D printer.