Expert consensus on difficulty assessment of endodontic therapy

Endodontic diseases are a kind of chronic infectious oral disease. Common endodontic treatment concepts are based on the removal of inflamed or necrotic pulp tissue and the replacement by gutta-percha. However, it is very essential for endodontic treatment to debride the root canal system and prevent the root canal system from bacterial reinfection after root canal therapy(RCT). Recent research, encompassing bacterial etiology and advanced imaging techniques, contributes to our understanding of the root canal system’s anatomy intricacies and the technique sensitivity of RCT. Success in RCT hinges on factors like patients, infection severity, root canal anatomy, and treatment techniques. Therefore, improving disease management is a key issue to combat endodontic diseases and cure periapical lesions. The clinical difficulty assessment system of RCT is established based on patient conditions, tooth conditions, root canal configuration, and root canal needing retreatment, and emphasizes pre-treatment risk assessment for optimal outcomes. The findings suggest that the presence of risk factors may correlate with the challenge of achieving the high standard required for RCT. These insights contribute not only to improve education but also aid practitioners in treatment planning and referral decision-making within the field of endodontics.

Construction of a nomogram model to predict technical difficulty in performing laparoscopic sphincter-preserving radical resection for rectal cancer

BACKGROUND Colorectal surgeons are well aware that performing surgery for rectal cancer becomes more challenging in obese patients with narrow and deep pelvic cavities.Therefore,it is essential for colorectal surgeons to have a comprehensive understanding of pelvic structure prior to surgery and anticipate potential surgical difficulties.AIM To evaluate predictive parameters for technical challenges encountered during laparoscopic radical sphincter-preserving surgery for rectal cancer.METHODS We retrospectively gathered data from 162 consecutive patients who underwent laparoscopic radical sphincterpreserving surgery for rectal cancer.Three-dimensional reconstruction of pelvic bone and soft tissue parameters was conducted using computed tomography(CT)scans.Operative difficulty was categorized as either high or low,and multivariate logistic regression analysis was employed to identify predictors of operative difficulty,ultimately creating a nomogram.RESULTS Out of 162 patients,21(13.0%)were classified in the high surgical difficulty group,while 141(87.0%)were in the low surgical difficulty group.Multivariate logistic regression analysis showed that the surgical approach using laparoscopic intersphincteric dissection,intraoperative preventive ostomy,and the sacrococcygeal distance were independent risk factors for highly difficult laparoscopic radical sphincter-sparing surgery for rectal cancer(P<0.05).Conversely,the anterior-posterior diameter of pelvic inlet/sacrococcygeal distance was identified as a protective factor(P<0.05).A nomogram was subsequently constructed,demonstrating good predictive accuracy(C-index=0.834).CONCLUSION The surgical approach,intraoperative preventive ostomy,the sacrococcygeal distance,and the anterior-posterior diameter of pelvic inlet/sacrococcygeal distance could help to predict the difficulty of laparoscopic radical sphincter-preserving surgery.

Development of a novel difficulty scoring system for laparoscopic liver resection procedure in patients with intrahepatic duct stones

BACKGROUND For intrahepatic duct(IHD)stones,laparoscopic liver resection(LLR)is currently a reliable treatment.However,the current LLR difficulty scoring system(DSS)is only available for patients with hepatocellular carcinoma.AIM To explore the development of a DSS for IHD stone patients with LLR and the validation of its reliability.METHODS We used clinical data from 80 patients who received LLR for IHD stones.Forty-six of these patients were used in multiple linear regression to construct a scoring system.Another 34 patients from different centers were used as external validation.The completeness of our DSS was then evaluated in patients with varying degrees of surgical difficulty based on documented surgical outcomes in the study group of patients.RESULTS The following five predictors were ultimately included and scored by calculating the weighted contribution of each factor to the prediction of operative time in the training cohort:Location of stones,number of stones≥3,stones located in the bile ducts of several grades,previous biliary surgery less than twice,distal bile duct atrophy.Subsequently,the data set was validated using a DSS developed from the variables.The following variables were identified as statistically significant in external validation:Operative time,blood loss,intraoperative transfusion,postoperative alanine aminotransferase,and Clavien-Dindo grading≥3.These variables demonstrated statistically significant differences in patients with three or more grades.CONCLUSION Patients with IHD stones have varying degrees of surgical difficulty,and the newly developed DSS can be validated with external data to effectively predict risks and complications after LLR surgery.

Text Difficulty,Working Memory Capacity and Mind Wandering During Chinese EFL Learners’Reading

This experimental study investigated how text difficulty and different working memory capacity(WMC)affected Chinese EFL learners’reading comprehension and their tendency to engage in task-unrelated thoughts,that is,mind wandering(MW),in the course of reading.Sixty first-year university non-English majors participated in the study.A two-factor mixed experimental design of 2(text difficulty:difficult and simple)×2(WMC:high/large and low/small)was employed.Results revealed that 1)the main and interaction effects of WMC and text difficulty on voluntary MW were significant,whereas those on involuntary MW were not;2)while reading the easy texts,the involuntary MW of high-WMC individuals was less frequent than that of low-WMC ones,whereas while reading the difficult ones,the direct relationship between WMC and involuntary MW was not found;and that 3)high-WMC individuals had a lower overall rate of MW and better reading performance than low-WMC individuals did,but with increasing text difficulty,their rates of overall MW and voluntary MW were getting higher and higher,and the reading performance was getting lower and lower.These results lend support to WM theory and have pedagogical implications for the instruction of L2 reading.

Effect of Mouth Opening Training Stick Combined with Oral Massage on Mouth Opening Difficulty in Head and Neck Cancer Patients after Treatment

Objective: To study the application effect of mouth-opening training sticks combined with oral massage on patients with mouth-opening difficulty after treatment for head and neck cancer. Methods: Using convenient sampling, 60 patients with mouth-opening difficulty after treatment for head and neck cancer admitted to the Oncology Department from February 2022 to October 2023 were selected for a 2-week exercise and nursing program. The patients were divided into a control group (February 1, 2022 to November 30, 2022) and an observation group (December 1, 2022 to October 31, 2023), with 30 patients in each group. The control group underwent routine mouth-opening functional exercises combined with cork for oral support training, while the observation group underwent routine mouth-opening functional exercises combined with oral massage and mouth-opening training sticks for oral support training. The mouth-opening degree, mouth-opening difficulty level, comfort level, compliance, and quality of life were observed in both groups. Results: Before the intervention, there were no statistically significant differences in mouth-opening degree and mouth-opening difficulty level between the two groups (P > 0.05). After the intervention, the mouth-opening degree, mouth-opening difficulty level, oral comfort level, compliance, and QLICP-HN scores in the observation group were all better than those in the control group, with statistically significant differences (P < 0.05). Conclusion: The combination of mouth-opening training sticks and oral massage with mouth-opening functional exercises can effectively improve the degree of mouth-opening difficulty, enhance oral comfort, increase compliance with mouth-opening exercises, and improve quality of life.

Transfer learning-based super-resolution in panoramic models for predicting mandibular third molar extraction difficulty: a multi-center study

Background:This study aims to predict the extraction difficulty of mandibular third molars based on panoramic images using transfer learning while employing super-resolution(SR)technology to enhance the feasibility and validity of the prediction.Methods:We reviewed a total of 608 preoperative mandibular third molar panoramic radiographs from two medical facilities:the First Affiliated Hospital of Zhengzhou University(n=509;456 in the training set and 53 in the test set)and the Henan Provincial Dental Hospital(n=99 in the validation set).We conducted a deep-transfer learning network on high-resolution(HR)panoramic radiographs to improve the longitudinal resolution of the images and obtained the SR images.Subsequently,we constructed models named Model-HR and Model-SR using high-dimensional quantitative features extracted through the Least Absolute Shrinkage and Selection Operator method.The models’performances were evaluated using the receiver operating characteristic curve(ROC).To assess the reliability of the model,we compared the results from the test set with those of three dentists.Results:Model-SR outperformed Model-HR(area under the curve(AUC):0.779,sensitivity:85.5%,specificity:60.9%,and accuracy:79.8%vs.AUC:0.753,sensitivity:73.7%,specificity:73.9%,and accuracy:73.7%)in predicting the difficulty of extracting mandibular third molars.Both Model-HR(AUC=0.821,95%CI 0.687–0.956)and Model-SR(AUC=0.963,95%CI 0.921–0.999)demonstrated superior performance compared to expert dentists(highest AUC=0.799,95%CI 0.671–0.927).Conclusions:Model-SR yielded superior predictive performance in determining the difficulty of extracting mandibular third molars when compared with Model-HR and expert dentists’visual assessments.

Information-Theoretic Analysis for the Difficulty of Extracting Hidden Information

The difficulty of extracting hidden information, which is essentially a kindof secrecy, is analyzed by information-theoretic method. The relations between key rate, messagerate, hiding capacity and difficulty of extraction are studied in the terms of unicity distance ofstego-key, and the theoretic conclusion is used to analyze the actual extracting attack on LeastSignificant Bit(LSB) steganographic algorithms.

Analysis of drilling difficulty of extended-reach wells based on drilling limit theory

With the continuous increase in vertical depths and horizontal displacements of directional wells,the difficulties of drilling operations continue to increase,and more accurate methods of drilling difficulty evaluation are needed.In this paper,a drilling difficulty evaluation method is built by combining drilling limit model and expert evaluation.Firstly,the concept of drilling difficulty index is introduced,and the method to calculate drilling difficulty index is established.Next,the meanings of five drilling difficulty levels are explained and the optimization design method with drilling difficulty as the target is built.At last,the theoretical model is applied to the extended-reach drilling of the Liuhua oilfield in the South China Sea,in which drilling difficulties are evaluated and the relationship between drilling difficulty and development control radius is revealed.The results indicate that extended-reach drilling in the Liuhua oilfield is on the“normal”difficulty level on average,rotary drilling in 8_(1/2)-in.section is the most difficult,and the main constraint conditions are excessive torque and high friction.Through technology upgradation,the drilling difficulties are decreased,the development control radius increases from 6.6 to 11.4 km,and the maximum horizontalto-vertical ratio increases from 5.3 to 8.7.Then,the development wells in marginal oilfields and adjustment wells in old oilfields can be drilled on“normal”difficulty level.Therefore,technology upgradation,especially drilling rig upgradation,is the most important development direction for extended-reach drilling in the South China Sea.

Study on fasART neuro-fuzzy networks for distinguishing the difficulty degree of top coal caving in steep seam

Distinguishing the difficulty degree of top coal caving was a precondition of the popularization and application of the roadway sub-level caving in steep seam. Because of complexity and uncertainty of the coal seam, the expression of influence factors was diffi-culty with exact data. According to the fuzzy and uncertainty of influence factors, triangular fuzzy membership functions were adopted to carry out the factors ambiguity, of which the factors not only have the consistency of semantic meaning, but also dissolve sufficiently expert knowledge. Based on the properties and structures of fasART fuzzy neural net-works of fuzzy logic system and practical needs, a simplified fasART model was put for-ward, stability and reliability of the network were improved, the deficiency of learning sam-ples and uncertainty of the factors were better treated. The method is of effective and practical value was identified by experiments.

The Effect of Topic Familiarity and Linguistic Difficulty on EFL Listening Comprehension

As a highly integrative and demanding receptive skill,listening comprehension presents a challenge to both learners and researchers.The study reported in this paper is listening comprehension objective-factor research.Manipulating topic factors,the study investigated the effect of topic familiarity and linguistic difficulty on EFL(English as a foreign language)listening comprehension of learners at different proficiency levels.

Is effect of transcranial direct current stimulation on visuomotor coordination dependent on task difficulty?

Transcranial direct current stimulation （tDCS）, an emerging technique for non-invasive brain stimulation, is increasingly used to induce changes in cortical excitability and modulate motor behavior, especially for upper limbs. The purpose of this study was to investigate the effects of tDCS of the primary motor cortex on visuomotor coordination based on three levels of task difficulty in healthy subjects. Thirty-eight healthy participants underwent real tDCS or sham tDCS. Using a single-blind, sham-controlled crossover design, tDCS was applied to the primary motor cortex. For real tDCS conditions, tDCS intensity was 1 mA while stimulation was applied for 15 minutes. For the sham tDCS, electrodes were placed in the same position, but the stimu- lator was turned off after 5 seconds. Visuomotor tracking task, consisting of three levels （levels 1, 2, 3） of difficulty with higher level indicating greater difficulty, was performed before and after tDCS application. At level 2, real tDCS of the primary motor cortex improved the accurate index compared to the sham tDCS. However, at levels 1 and 3, the accurate index was not significantly increased after real tDCS compared to the sham tDCS. These findings suggest that tasks of mod- erate difficulty may improve visuomotor coordination in healthy subjects when tDCS is applied compared with easier or more difficult tasks.

Effect of rehabilitation education on pain, knee stiffness and performance difficulty in patients undergoing knee replacement surgery: A randomized clinical trial

Objective:To determine the effect of rehabilitation education on pain,knee stiffness and performance difficulty in patients undergoing knee replacement surgery.Methods:This randomized clinical trial study was performed on 96 patients undergoing knee replacement surgery,who were randomly divided into two groups:the control group and the intervention group,with 48 patients in each group.In the intervention group,the patients received educational intervention in four stages one day before surgery,24 h and 48 h later,upon discharge from the hospital.In the control group,only the routine of the hospital was performed.Questionnaires were completed before and 6 weeks after the intervention.Results:The mean scores of pain,knee stiffness and performance difficulty were significantly decreased in the intervention group(P=0.01).Compared to the control group,the intervention group had a better outcome of the illness,including pain,knee stiffness and performance difficulty(P=0.001).Conclusion:Rehabilitation education could be a suitable way to improve the surgical outcomes of patients undergoing total knee replacement.

Rxamining the relationships between medical students'preferred online instructional strategies,course difficulty level,learning performance and effectiveness

Students'preferences and engagement with online educational resources and activities are crucial for academic success in the context of online medical education.This study investigated the preferences of Chinese medical students regarding the teaching strategies used by instructors and their relationship with course difficulty level,students'academic performance and perceived effectiveness.Survey data(n=375)was collected from the medical students from one of the largest medical schools in Southern China during the spring semester of 2020.

Prediction difficulty, financial strength and debt maturity

In order to have the optimal capital structure, the company with higher volatility of return adjusts the capital structure more frequently and has shorter debt maturity. Investors also have shorter investment cycle on these companies. Investment cycle is also affected by information asymmetry. The less asymmetric the information is, the more information investors get and the longer the investment cycle is. The adjustment frequency is also restricted by financial strength. This paper measures the debt maturity structure of the firm as the weighted average of debt maturity, and it is more precise than the ratio of long term debt to total debt. In empirical tests on debt maturity, the results show that financial strength, volatility of return and asymmetric information all have negative impacts on debt maturity.

A Note on the Validity of the Shannon Formulation for Fitts’ Index of Difficulty

The three most common variations of Fitts’ index of difficulty are the Fitts formulation, the Welford formulation, and the Shannon formulation. A recent paper by Hoffmann [1] critiqued the three and concluded that the Fitts and Welford formulations are valid and that the Shannon formulation is invalid. In this paper, we challenge Hoffmann’s position regarding the Shannon formulation. It is argued that the issue of validity vs. invalidity is ill-conceived, given that Fitts’ law is a “model by analogy” with no basis in human motor control. The relevant questions are of utility: Does a model work? How well? Is it useful? Where alternative formulations exist, they may be critiqued and compared for strengths and weaknesses, but validity is an irrelevant construct. In a reanalysis of data from Fitts’ law experiments, models built using the Shannon formulation are (re)affirmed to be as good as, and generally better than, those built using the Fitts or Welford formulation.

Sensitivity Analysis on the Negative Degree of Difficulty Geometric Programming Problem

The range of optimal values in cost optimization models provides management with options for decision making. However, it can be quite challenging to achieve feasible range of optimality in Geometric programming (Gp) models having negative degrees of difficulty. In this paper, we conduct sensitivity analysis on the optimal solution of Geometric programming problem with negative degree of difficulty. Using imprest data, we determine the optimal objective function, dual decision variables, primal decision variables;the range of values, the cost coefficient and RHS constraint must lie for the solution to stay optimal. From the analysis, we established that incremental sensitivity analysis has the functional form .

The Reasons of Students’ Difficulty in Improving Their Listening in China

With the promoting of world integration,the role of English listening and speaking is becoming more and more important.English listening is attached more importance to in higher education.Although many universities and college students take different measures to improve the students’English listening abilities,it is found that it is difficult to improve the students’English listening abilities effectively.This article will analyze the reasons of students’difficulty in improving their listening in the aim at discussing the measures to improve the students’listening effectively with other educators.

Prof.Larry Benowitz:the future of optic nerve regeneration and the difficulty of keeping retinal ganglion cells alive

Editor’s note Guangzhou Glaucoma Forum(GZGF)was successfully held in the Zhongshan Ophthalmology Center on April 21-22,2018.The forum gathered domestic and international experts from all over the world,including Prof.Larry Benowitz from Harvard Medical School,Prof.Leopold Schmetterer from Singapore Eye Research Institute,Prof.Anuj Chauhan from University of Florida,Prof.Shlomo Melamed from Israel,and Prof.Keith Barton from Moorfields Eye Hospital.AME editorial team had the honor to interview Prof.Benowitz.

A Cognitive Study of the Difficulty of Writing Test Tasks

If a task is to be included in a reliable test, its features and the level of difficulty should be specified so that we know it is appropriate to the examinees. Beginning from Skehan＇s （1998） cognitive perspective of task features in L2 instruction, the study compares the performance of two kinds of writing tasks from CET （College English Test） in China in order to verify whether the hypothesized task difficulty set by Skehan＇s cognitive framework can predict the actual performance of the examinees in testing context. The study also investigates the examinee＇s own perception of test tasks and the relationship between such perception and their performance. The results of the study show that more cognitively demanding tasks tend to generate greater level of task difficulty and thus elicit poorer examinee performance. However, it does not find enough evidence that there is some systematic competition between accuracy, fluency and complexity in the performance. It also shows the examinees＇ own perception of difficulty is variable and cannot be relied on. There is some reasonable self-awareness of the quality of their performance in terms of accuracy and fluency, but not complexity. It concludes to suggest that the two types of tasks should not be treated as parallel in CET in view of the observed difference on the examinees＇ performance.

Influencing program satisfaction for undergraduate students in STEM areas: The impact of interdisciplinary features, disciplinary connectedness, faculty support, and examination difficulty

Ensuring program satisfaction for undergraduate students in the areas of science,technology,engineering and mathematics(STEM)matters in student retention and education quality improvement.This study explores how four rarely examined variables support from faculty members,interdisciplinary features of STEM program courses,disciplinary connectedness of STEM program core courses,and examination difficulty impact Chinese STEM undergraduates’program satisfaction.With data from 619 Chinese STEM undergraduates,structural equation modeling shows that course satisfaction partially mediates the impact of support from faculty members on program satisfaction,while fully mediating that of interdisciplinary features of STEM program courses and disciplinary connectedness of STEM program core courses on program satisfaction.Examination difficulty exerts no significant impact on program satisfaction neither directly nor indirectly.Support from faculty members impact course satisfaction significantly stronger for junior and senior students than for freshmen and sophomores,while interdisciplinary features of STEM program courses impact course satisfaction stronger for freshmen and sophomores than for juniors and seniors.The study ends with practical implications for the higher education reform in relevant areas.