Artificial intelligence-based analysis of the spatial distribution of abnormal computed tomography patterns in SARS-CoV-2 pneumonia: association with disease severity.

BACKGROUND: The substantial heterogeneity of clinical presentations in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia still requires robust chest computed tomography analysis to identify high-risk patients. While extension of ground-glass opacity and consolidation from peripheral to central lung fields on chest computed tomography (CT) might be associated with severely ill conditions, quantification of the central-peripheral distribution of ground glass opacity and consolidation in assessments of SARS-CoV-2 pneumonia remains unestablished. This study aimed to examine whether the central-peripheral distributions of ground glass opacity and consolidation were associated with severe outcomes in patients with SARS-CoV-2 pneumonia independent of the whole-lung extents of these abnormal shadows. METHODS: This multicenter retrospective cohort included hospitalized patients with SARS-CoV-2 pneumonia between January 2020 and August 2021. An artificial intelligence-based image analysis technology was used to segment abnormal shadows, including ground glass opacity and consolidation. The area ratio of ground glass opacity and consolidation to the whole lung (GGO%, CON%) and the ratio of ground glass opacity and consolidation areas in the central lungs to those in the peripheral lungs (GGO(C/P)) and (CON(C/P)) were automatically calculated. Severe outcome was defined as in-hospital death or requirement for endotracheal intubation. RESULTS: Of 512 enrolled patients, the severe outcome was observed in 77 patients. GGO% and CON% were higher in patients with severe outcomes than in those without. Multivariable logistic models showed that GGO(C/P), but not CON(C/P), was associated with the severe outcome independent of age, sex, comorbidities, GGO%, and CON%. CONCLUSION: In addition to GGO% and CON% in the whole lung, the higher the ratio of ground glass opacity in the central regions to that in the peripheral regions was, the more severe the outcomes in patients with SARS-CoV-2 pneumonia were. The proposed method might be useful to reproducibly quantify the extension of ground glass opacity from peripheral to central lungs and to estimate prognosis.

Combination Therapy with EGFR Tyrosine Kinase Inhibitors and TEAD Inhibitor Increases Tumor Suppression Effects in EGFR Mutation-positive Lung Cancer.

EGFR-tyrosine kinase inhibitors (TKI) are the first-line therapies for EGFR mutation-positive lung cancer. EGFR-TKIs have favorable therapeutic effects. However, a large proportion of patients with EGFR mutation-positive lung cancer subsequently relapse. Some cancer cells survive the initial treatment with EGFR-TKIs, and this initial survival may be associated with subsequent recurrence. Therefore, we aimed to overcome the initial survival against EGFR-TKIs. We hypothesized that yes-associated protein 1 (YAP1) is involved in the initial survival against EGFR-TKIs, and we confirmed the combined effect of EGFR-TKIs and a YAP1-TEAD pathway inhibitor. The KTOR27 (EGFR kinase domain duplication) lung cancer cell lines established from a patient with EGFR mutation-positive lung cancer and commercially available PC-9 and HCC827 (EGFR exon 19 deletions) lung cancer cell lines were used. These cells were used to evaluate the in vitro and in vivo effects of VT104, a TEAD inhibitor. In addition, YAP1 involvement was investigated in pathologic specimens. YAP1 was activated by short-term EGFR-TKI treatment in EGFR mutation-positive lung cancer cells. In addition, inhibiting YAP1 function using siRNA increased the sensitivity to EGFR-TKIs. Combination therapy with VT104 and EGFR-TKIs showed better tumor-suppressive effects than EGFR-TKIs alone, in vitro and in vivo. Moreover, the combined effect of VT104 and EGFR-TKIs was observed regardless of the localization status of YAP1 before EGFR-TKI exposure. These results suggest that combination therapy with the TEAD inhibitor and EGFR-TKIs may improve the prognosis of patients with EGFR mutation-positive lung cancer.

CD47 polymorphism for predicting nivolumab benefit in patients with advanced non­small­cell lung cancer.

Immune checkpoint inhibitors (ICIs), such as nivolumab, play an essential role in non-small-cell lung cancer (NSCLC) treatment. Programmed death ligand-1 has been used as a predictive biomarker for the efficacy of ICI treatment in patients with NSCLC; however, its predictive value is considered insufficient. Therefore, there is an urgent need for better predictive biomarkers. The present study focused on the CD47 molecule, which is associated with macrophages and tumor immunity. The study aimed to investigate the association between CD47 single nucleotide polymorphism (SNP) and the therapeutic effect of nivolumab in patients with NSCLC. The CD47 SNP genotypes and clinical outcomes were retrospectively analyzed in 164 patients with NSCLC treated with nivolumab at Kyoto University Hospital (Kyoto, Japan). Patients with the G/G genotype of the CD47 SNP rs3804639 had significantly longer progression-free survival than those with the G/T or T/T genotypes [2.6 months vs. 2.1 months, hazard ratio (HR), 0.70; P=0.026]. Moreover, the G/G genotype of the CD47 SNP rs3804639 was associated with a significantly longer median overall survival than the G/T or T/T genotypes of the CD47 SNP rs3804639 (24.8 months vs. 12.0 months, HR, 0.64; P=0.021). In conclusion, CD47 polymorphism may be a novel predictive biomarker of nivolumab efficacy in patients with advanced NSCLC.

Yes-associated protein 1 mediates initial cell survival during lorlatinib treatment through AKT signaling in ROS1-rearranged lung cancer.

Tyrosine kinase inhibitors (TKIs) that target the ROS proto-oncogene 1, receptor tyrosine kinase (ROS1) gene have shown dramatic therapeutic effects in patients with ROS1-rearranged non-small-cell lung cancer (NSCLC). Nevertheless, advanced ROS1-rearranged NSCLC is rarely cured as a portion of the tumor cells can survive the initial stages of ROS1-TKI treatment, even after maximum tumor shrinkage. Therefore, understanding the mechanisms underlying initial cell survival during ROS1-TKI treatment is necessary to prevent cell survival and achieve a cure for ROS1-rearranged NSCLC. In this study, we clarified the initial survival mechanisms during treatment with lorlatinib, a ROS1 TKI. First, we established a patient-derived ezrin gene-ROS1-rearranged NSCLC cell line (KTOR71). Then, following proteomic analysis, we focused on yes-associated protein 1 (YAP1), which is a major mediator of the Hippo pathway, as a candidate factor involved in cell survival during early lorlatinib treatment. Yes-associated protein 1 was activated by short-term lorlatinib treatment both in vitro and in vivo. Genetic inhibition of YAP1 using siRNA, or pharmacological inhibition of YAP1 function by the YAP1-inhibitor verteporfin, enhanced the sensitivity of KTOR71 cells to lorlatinib. In addition, the prosurvival effect of YAP1 was exerted through the reactivation of AKT. Finally, combined therapy with verteporfin and lorlatinib was found to achieve significantly sustained tumor remission compared with lorlatinib monotherapy in vivo. These results suggest that YAP1 could mediate initial cell resistance to lorlatinib in KTOR71 cells. Thus, combined therapy targeting both YAP1 and ROS1 could potentially improve the outcome of ROS1-rearranged NSCLC.

Sarcomatoid malignant pleural mesothelioma treated with nivolumab: A case series.

Immune checkpoint therapy (ICT) with nivolumab has been widely used to treat malignant pleural mesothelioma (MPM) since clinical trials confirmed its efficacy. However, only a few clinical trials have been conducted for the treatment of sarcomatoid MPM, which is a rare histological type of MPM. Additionally, clinical reports of sarcomatoid MPM are scarce. Therefore, the benefits and risks of nivolumab treatment for sarcomatoid MPM remain unclear. The present report describes the treatment of 3 cases of sarcomatoid MPM (all 3 were men) with nivolumab monotherapy. In all three cases, nivolumab was effective despite variations in the duration of treatment, although side effects were observed in 2 patients. Programmed death ligand 1 (PD-L1) expression was positive in all 3 cases. In particular, the patient with the highest PD-L1 expression had the most rapid response of the 3 patients, and the effect lasted as long as those of the other 2, despite receiving the smallest number of doses of nivolumab. It has been reported that sarcomatoid MPM tends to respond poorly to chemotherapy and express higher levels of PD-L1 than epithelial MPM; thus, ICT may be necessary in these cases. This case series suggests that ICT with nivolumab is a promising treatment option for sarcomatoid MPM.

Survival impact of treatment for chronic obstructive pulmonary disease in patients with advanced non-small-cell lung cancer.

Chronic obstructive pulmonary disease (COPD) may coexist with lung cancer, but the impact on prognosis is uncertain. Moreover, it is unclear whether pharmacological treatment for COPD improves the patient's prognosis. We retrospectively investigated patients with advanced non-small-cell lung cancer (NSCLC) who had received chemotherapy at Kyoto University Hospital. Coexisting COPD was diagnosed by spirometry, and the association between pharmacological treatment for COPD and overall survival (OS) was assessed. Of the 550 patients who underwent chemotherapy for advanced NSCLC between 2007 and 2014, 347 patients who underwent spirometry were analyzed. Coexisting COPD was revealed in 103 patients (COPD group). The median OS was shorter in the COPD group than the non-COPD group (10.6 vs. 16.8 months). Thirty-seven patients had received COPD treatment, and they had a significantly longer median OS than those without treatment (16.7 vs. 8.2 months). Multivariate Cox regression analysis confirmed the positive prognostic impact of COPD treatment. Additional validation analysis revealed similar results in patients treated with immune checkpoint inhibitors (ICIs). Coexisting COPD had a significant association with poor prognosis in advanced NSCLC patients if they did not have pharmacological treatment for COPD. Treatment for coexisting COPD has the potential to salvage the prognosis.

Pneumonia Caused by Severe Acute Respiratory Syndrome Coronavirus 2 and Influenza Virus: A Multicenter Comparative Study.

BACKGROUND: Detailed differences in clinical information between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia (CP), which is the main phenotype of SARS-CoV-2 disease, and influenza pneumonia (IP) are still unclear. METHODS: A prospective, multicenter cohort study was conducted by including patients with CP who were hospitalized between January and June 2020 and a retrospective cohort of patients with IP hospitalized from 2009 to 2020. We compared the clinical presentations and studied the prognostic factors of CP and IP. RESULTS: Compared with the IP group (n = 66), in the multivariate analysis, the CP group (n = 362) had a lower percentage of patients with underlying asthma or chronic obstructive pulmonary disease (P < .01), lower neutrophil-to-lymphocyte ratio (P < .01), lower systolic blood pressure (P < .01), higher diastolic blood pressure (P < .01), lower aspartate aminotransferase level (P < .05), higher serum sodium level (P < .05), and more frequent multilobar infiltrates (P < .05). The diagnostic scoring system based on these findings showed excellent differentiation between CP and IP (area under the receiver operating characteristic curve, 0.889). Moreover, the prognostic predictors were different between CP and IP. CONCLUSIONS: Comprehensive differences between CP and IP were revealed, highlighting the need for early differentiation between these 2 pneumonias in clinical settings.

PD-L1 polymorphisms predict survival outcomes in advanced non-small-cell lung cancer patients treated with PD-1 blockade.

BACKGROUND: We previously reported that PD-L1 polymorphisms are associated with the efficacy and immune-related adverse events of PD-1 blockade with nivolumab. However, the association between PD-L1 polymorphisms and survival outcomes under PD-1/PD-L1 blockade is still uncertain. Here, we aimed to investigate whether PD-L1 polymorphisms are associated with survival outcomes in advanced non-small-cell lung cancer (NSCLC) patients treated with nivolumab. METHODS: PD-1/PD-L1 polymorphisms and survival outcomes were retrospectively analysed in two independent cohorts (133 patients treated with nivolumab and 96 patients with no treatment history of an immune checkpoint inhibitor (ICI) (the non-ICI cohort)) with advanced NSCLC. RESULTS: Among the 7 studied single-nucleotide polymorphisms, PD-L1 rs822339 and rs1411262 were associated with overall survival (OS) in patients treated with nivolumab. Patients with the A/A genotype of rs822339 had a significantly longer OS than those with A/G or G/G genotypes (not reached versus 12.0 months; hazard ratio (HR), 0.35; 95% confidence interval (CI), 0.18-0.64; p = 0.0008). A similar survival benefit with the A/A genotype was observed regardless of driver mutation status. In multivariate analysis, performance status (PS) and PD-L1 rs822339 genotype were independent prognostic factors for OS. In the non-ICI cohort, the PD-L1 rs822339 genotype did not correlate with OS (HR, 0.77; 95% CI, 0.31-1.70; p = 0.55). The T/T genotype of rs1411262 also showed a significant prolongation of OS compared to that with the C/T or C/C genotypes in patients treated with nivolumab. CONCLUSIONS: PD-L1 polymorphisms are associated with favourable OS in nivolumab-treated NSCLC patients and may be useful predictive biomarkers, regardless of driver mutation status.

MCL1 inhibition is effective against a subset of small-cell lung cancer with high MCL1 and low BCL-XL expression.

There have been few advances in the treatment of small-cell lung cancer (SCLC) because of the lack of targets. MCL1, a member of the anti-apoptotic BCL-2 family, may be a treatment target in several cancers, including SCLC. However, whether the expression profile of the anti-apoptotic BCL-2 family affects MCL1 inhibition strategy is unknown. A tissue microarray (TMA) was created from consecutive patients who were diagnosed with SCLC and had previously undergone surgery at Kyoto University Hospital (Kyoto, Japan) between 2001 and 2017. We used S63845, a MCL1 inhibitor, to assess the cytotoxic capacity in SCLC cell lines including a patient-derived cell line in vitro and in vivo. The combination of S63845 with navitoclax, a double BCL-XL/BCL-2 inhibitor, was also employed to examine the comprehensive inhibition of the anti-apoptotic BCL-2 family. Immunohistochemistry of a TMA from patients with surgically resected SCLC demonstrated high MCL1 expression with low BCL-XL and BCL-2 to be the most common expression profile. S63845 was effective in high MCL1- and low BCL-XL-expressing SCLC cell lines. S63845 induced BAK-dependent apoptosis in vitro, and the anti-tumor efficacy was confirmed in an in vivo model. Although knockdown of BCL-XL and BCL-2 improved the cytotoxic activity of S63845 and its combination with navitoclax increased the anti-tumor cytotoxicity, the therapeutic range of S63845 with navitoclax was narrow in in vivo studies. Our study suggests MCL1 inhibition therapy be applied for high MCL1- and low BCL-XL-expressing SCLC patients.

YAP1 mediates survival of ALK-rearranged lung cancer cells treated with alectinib via pro-apoptotic protein regulation.

Despite the promising clinical efficacy of the second-generation anaplastic lymphoma kinase (ALK) inhibitor alectinib in patients with ALK-rearranged lung cancer, some tumor cells survive and eventually relapse, which may be an obstacle to achieving a cure. Limited information is currently available on the mechanisms underlying the initial survival of tumor cells against alectinib. Using patient-derived cell line models, we herein demonstrate that cancer cells survive a treatment with alectinib by activating Yes-associated protein 1 (YAP1), which mediates the expression of the anti-apoptosis factors Mcl-1 and Bcl-xL, and combinatorial inhibition against both YAP1 and ALK provides a longer tumor remission in ALK-rearranged xenografts when compared with alectinib monotherapy. These results suggest that the inhibition of YAP1 is a candidate for combinatorial therapy with ALK inhibitors to achieve complete remission in patients with ALK-rearranged lung cancer.

Impact of urinary tract infection on nursing and healthcare-associated pneumonia.

Nursing and healthcare-associated pneumonia (NHCAP), a concept of pneumonia proposed by the Japanese Respiratory Society, mostly occurs among elderly people in long-term care facilities. Similarly, the risk of urinary tract infection (UTI) also increases with age, with UTIs common among those in long-term care. Therefore, NHCAP is sometimes complicated by the presence of a UTI. However, pneumonia complicated by a UTI has not been clinically well characterized. We retrospectively analyzed 376 patients with NHCAP admitted to our hospital over a three-year period. Sixty-seven patients (17.8%) showed complications by a UTI. Patients with a UTI had lower renal function (higher blood urea nitrogen [P = 0.001], higher creatinine [P = 0.001]), lower systolic blood pressure (P = 0.04), higher A-DROP scores (P = 0.005) and higher positive blood culture rates (P = 0.03) than those without a UTI. Furthermore, based on urine, sputum and blood culture results, nearly half of the microorganisms (4/7) in blood cultures were identical with those of urine, suggesting that a concurrent UTI increases positive blood culture rates. Multivariate analysis showed that UTI was not an independent factor associated with 30-day mortality (P = 0.17), although patients with a UTI showed higher 30-day mortality (P = 0.04) than those without a UTI in univariate analysis. In summary, patients with NHCAP and a UTI were more prone to complications than those without a UTI, although UTI itself did not affect the prognosis of patients with NHCAP. A concurrent UTI had a negative impact on the severity of NHCAP.

Ten-year experience of smoking cessation in a single center in Japan.

BACKGROUND: Long-term, real-world data, as opposed to academic or research data, on outcomes of smoking cessation clinics are scarce. We assessed patient outcomes over a 10-year period at a smoking cessation clinic in a community teaching hospital in Japan and explored predictors of successful smoking cessation. METHODS: We used data from a prospective registry of cigarette smokers who participated in a 3-month smoking cessation program comprising combined pharmacological treatment and cognitive behavioral therapy and explored factors associated with program execution and successful smoking cessation. The primary outcome was smoking cessation, defined by quitting completely between the 8-week and 12-week sessions, with verification according to exhaled carbon monoxide (CO) level of ≤10 ppm. RESULTS: Between August 2007 and December 2017, 813 patients with nicotine dependence participated in the program. The number of participants decreased after Japan׳s 2010 tobacco tax increase. Among participants, 433 (53.3%) completed the program. In multivariate analysis, the number of cigarettes smoked daily (odds ratio [OR] 0.98, 95% confidence interval [CI] 0.96, 0.99), cardiovascular disease (OR 1.75, 95% CI 1.16, 2.68), chronic obstructive pulmonary disease (OR 1.74, 95% CI 1.10, 2.78), and gastric/duodenal ulcer (OR 1.77, 95% CI 1.04, 3.08) were significantly associated with program completion. Among program completers, 288 (66.5%) achieved smoking cessation. Exhaled CO level (OR 0.94, 95% CI 0.93, 0.97) and mental disorders (OR 0.53, 95% CI 0.33, 0.85) were negatively associated with successful smoking cessation. CONCLUSIONS: Baseline exhaled CO level and mental disorders were significantly associated with either success or failure of smoking cessation.

Simultaneous presence of lung adenocarcinoma and malignant pleural mesothelioma: A case report.

The co-presence of malignant pleural mesothelioma (MPM) and lung cancer is rare. We report a 70-year-old male with exposure to asbestos. Chest computed tomography revealed a right mediastinal mass combined with an enlarged ipsilateral lymph node and left pleural effusion. Transbronchial lung biopsy revealed lung adenocarcinoma. Thoracoscopic examination revealed multiple left pleural nodules, leading to the diagnosis of MPM. Despite aggressive anticancer drug therapy, he expired due to disease progression 2.5 years after diagnosis. Autopsy confirmed an epithelioid MPM in the left pleura. MPM comorbidity in patients diagnosed with lung cancer should be considered, especially in those exposed to asbestos.

Acute exacerbation of idiopathic pulmonary fibrosis: a 10-year single-centre retrospective study.

INTRODUCTION: In 2016, an international working group proposed a revised definition and new diagnostic criteria for the acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF). Based on these criteria, AE-IPF was diagnosed regardless of the presence or absence of a known trigger and categorised as triggered (T-AE) or idiopathic (I-AE) AE-IPF. However, the clinical characteristics of the newly defined AE-IPF and clinical differences between T-AE and I-AE are unresolved. METHODS: We retrospectively analysed 64 patients with AE-IPF (I-AE (42), T-AE (22)) admitted to our hospital over a 10- year period. RESULTS: I-AE and T-AE cases did not show differences in in-hospital and long-term outcomes (in-hospital mortality: I-AE 52.4%, T-AE 59.1%, p=0.61; long-term mortality: p=0.68). In the I-AE group, significantly more patients received corticosteroid therapy before an AE (I-AE 35.7%, T-AE 4.5%; p=0.01). Significantly more patients in the T-AE group had lung cancer (I-AE 7.1%, T-AE 59.1%, p<0.001). I-AE occurred more frequently in winter while T-AE did not show seasonality. The white blood cell (WBC) count and haemoglobin (Hb) level were independent predictors of in-hospital deaths in I-AE (WBC: OR 1.87; 95% CI 1.09 to 4.95, p=0.01; Hb: OR 0.26, 95% CI 0.04 to 0.78, p=0.01) but not T-AE. DISCUSSION: With the introduction of new criteria for AE-IPF, a retrospective study over a 10-year period showed a lack of prognostic difference between I-AE and T-AE. The WBC count and Hb level predicted in-hospital outcome in I-AE cases.

Mycoplasma hominis empyema following caesarean section.

Mycoplasma hominis as a cause of empyema is rare. We report a case of empyema caused by M. hominis following a caesarean section. A 28-year-old woman at 39 weeks and one day of pregnancy was admitted to our hospital and underwent an emergency caesarean section because of premature rupture of membranes. On postoperative day 2, she developed a fever, and flomoxef was administered. A pleural effusion developed on the right side. A diagnosis of empyema was made, and sulbactam/ampicillin was administered. However, the patient's clinical condition did not improve. Numerous small pinpoint colonies, which did not yield visible bacteria on a Gram stain, were observed on a plate of pleural fluid culture, and M. hominis empyema was suspected. Based on this result, antibiotic therapy was switched to clindamycin, and the patient's clinical condition improved rapidly. M. hominis was detected in the pleural fluid by polymerase chain reaction (PCR) assay. M. hominis should be considered a causative pathogen for empyema following a caesarean section.

Significance of blood cultures in nursing home-acquired pneumonia.

The significance of blood cultures in nursing home-acquired pneumonia (NHAP) is incompletely understood. We retrospectively analyzed the clinical and laboratory features of 515 patients with NHAP admitted to our hospital over an 11-year period. Blood cultures were obtained from 336 patients (65.2%). We compared 13 and 323 patients with positive and negative blood cultures, respectively. The former showed lower systolic blood pressure and higher blood urea nitrogen (BUN), creatinine, C-reactive protein (CRP), and A-DROP scores than the latter. With regard to A-DROP parameters, patients with positive blood cultures showed significantly higher rates of dehydration (BUN ≥ 21 mg/dL) and low blood pressure (systolic blood pressure ≤ 90 mmHg). Multivariate analysis identified CRP values and low blood pressure as independent predictors of bacteremia: CRP (odds ratio [OR] 1.11; 95% confidence interval [CI] 1.04-1.19, P = 0.003) and low blood pressure (OR 6.03; 95% CI 1.06-34.25, P = 0.04). A receiver operating characteristic curve indicated that CRP was of moderate accuracy (area under the curve = 0.75), and its diagnostic accuracy was optimal at a cut-off point of 19.2 mg/dL (sensitivity 69%, specificity 87%). Since the probability of true bacteremia is very low in NHAP, obtaining blood cultures from all patients with NHAP is unnecessary. However, our results suggest blood cultures are warranted from patients with high CRP values (≥20 mg/dL) or low blood pressure.

Study of corrosion of combinations of titanium/Ti-6Al-4V implants and dental alloys.

Metal ions released in 1% lactic acid solution from combinations of titanium fixtures with superstructures made of dental precious metal alloys (dental alloys) and titanium and differences based on the fixing method were investigated. In combinations of titanium with dental alloys, the level of Ti release was influenced by micro-structure of titanium: it was lower when the grain size was smaller. In titanium-titanium combinations, differences in the micro-structure of metal also markedly influenced the dissolution: the level of release increased when the micro-structure of titanium was different. The Ti and V release levels were higher in combination with titanium alloy and titanium than with titanium alloy and dental alloys. Regarding the superstructure-fixture fixing method, the level of Ti release was significantly lower in cement than in direct fixation.

Construction of database for three-dimensional human tooth models and its ability for education and research--Carious tooth models -.

To construct a human teeth database which is freely available to researchers and students, three-dimensional human tooth models were generated in a previous study, by means of micro-CT, from 35 human teeth extracted during orthodontic treatment. In this study, X-ray images of 55 extracted human teeth were acquired using three-dimensional micro-CT at a resolution of 50x50x50 microm, and then visualized using a numerical data visualization software. These carious tooth models provided insight into the morphology and progression of carious defects as well as a rare insight into the morphology of carious tooth pulp, therefore rendering them as a useful tool and efficient method for dental students' learning. Moreover, these three-dimensional models could be simultaneously observed and used by many students and researchers at any one time, which was a superior advantage than having only one actual tooth for learning and study by many.