Effects of diameters of implant and abutment screw on stress distribution within dental implant and alveolar bone: A three-dimensional finite element analysis

Background/purpose

Few studies have investigated the effects of abutment screw diameter in the stress of dental implants and alveolar bones under occlusal forces. In this study, we investigated how variations in implant diameter, abutment screw diameter, and bone condition affect stresses in the abutment screw, implant, and surrounding bone.

Materials and methods

Three-dimensional finite element (FE) models were fabricated for dental implants with external hex-type abutments measuring 4 and 5 mm in diameter. The models also included abutment screws measuring 2.0 and 2.5 mm in diameter. Each implant model was integrated with the mandibular bone comprising the cortical bone and four types of cancellous bone. In total, 12 finite element models were generated, subjected to three different occlusal forces, and analyzed using FE software to investigate the stress distribution of dental implant and alveolar bone.

Results

Wider implants demonstrated lower stresses in implant and bone compared with standard-diameter implants. The quality of cancellous bone has a minimal impact on the stress values of the implant, abutment screw, and cortical bone. Regardless of occlusal arrangement or quality of cancellous bone, a consistent pattern emerged: larger abutment screw diameters led to increased stress levels on the screws, while the stress levels in both cortical and cancellous bone showed comparatively minor fluctuations.

Conclusion

Wider implants tend to have better stress distribution than standard-diameter implants. The potential advantage of augmenting the abutment screw diameter is unfavorable. It may result in elevated stresses in the implant system.

The Association of Salivary Flow Rate and Sleep Quality among Head and Neck Cancer Survivors after Radiotherapy

BACKGROUND

Head and neck cancer survivors suffer from xerostomia and sleep disturbances after radiotherapy, both of which affect their quality of life. This study aimed to explore the role of salivary flow in the oral health and sleep quality of head and neck cancer survivors.

METHODS

We recruited 120 head and neck cancer survivors who were experiencing symptoms of dry mouth or sleep disturbances post-radiotherapy from a dental clinic. We gathered their socio-demographic and clinical data, measured their salivary flow rate, and recorded their dry mouth score using the summated xerostomia inventory. Additionally, a dentist collected the DMFT (Decayed, Missing, and Filled Teeth) index. The Pittsburgh Sleep Quality Index was employed to assess their sleep quality.

RESULTS

In this study, xerostomia was observed in nearly 80% of the cancer survivors. The concurrent prevalence of sleep disturbance and xerostomia was at 55%. After five years post-radiotherapy, there was a significant improvement observed in both the quality of sleep (p = 0.03) and the stimulated salivary flow rate (p = 0.04). Additionally, these improvements were noted to have commenced from the third year onwards. A significant association was found between stimulated salivary flow and dry mouth scores with poor sleep quality (p <  0.05).

CONCLUSIONS

We recommend that dental professionals prioritize managing both dental and mental health issues equally for head and neck cancer survivors who have undergone radiotherapy within the past 3 years.

Arecoline Induces ROS Accumulation, Transcription of Proinflammatory Factors, and Expression of KRT6 in Oral Epithelial Cells

Areca nut is a major contributor to the high prevalence of oral cancer in Asia. The precise mechanisms by which areca nut stimulates mucosal cells and contributes to the progression of oral cancer urgently require clarification. The current study aimed to assess the effects of arecoline on the normal human gingival epithelium cell line S-G. Cell viability, levels of reactive oxygen species (ROS), protein expression, cellular morphology, and gene expression were evaluated using the MTT test, flow cytometry, Western blot analysis, optical or confocal microscopy, and RT-qPCR. Keratin (KRT6) analysis involved matched normal and cancer tissues from clinical head and neck specimens. The results demonstrated that 12.5 µg/mL of arecoline induced ROS production, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) mRNA expression in S-G cells. This activation of the MAPK/ERK pathway increased KRT6 expression while limiting cell migration. In head and neck cancer tissues, KRT6B gene expression exceeded that of normal tissues. This study confirms that arecoline induces ROS accumulation in normal cells, leading to the secretion of proinflammatory factors and KRT6 expression. This impedes oral mucosal healing, thereby promoting the progression of oral cancer.

Association of higher transient receptor potential melastatin 8 expression with higher tumor histologic grades, lymph node metastasis, risk factors, and worse survival in patients with head and neck squamous cell carcinoma

Background/purpose

Transient receptor potential melastatin 8 (TRPM8), a thermosensitive ion channel known for its role in cold sensation and menthol response, has emerged as a potential regulator in various cancers. This study aimed to investigate expression trends of TRPM8 in head and neck squamous cell carcinoma (HNSCC) cases and oral squamous cell carcinoma (OSCC) cell lines and its association with clinicopathological features.

Materials and methods

The noncancerous matched tissues and HNSCC paired tissue samples from 84 HNSCC patients were utilized to evaluate the association of TRPM8 with HNSCC clinicopathological features. TRPM8 expression was examined in HNSCC patient tissues and OSCC cell lines treated with arecoline.

Results

Kaplan-Meier survival analysis of TCGA data revealed high TRPM8 expression correlated with unfavorable outcomes and higher tumor histologic grades. TRPM8 mRNA expression was upregulated in HNSCC cell lines and patients' tissue samples. Arecoline treatment led to significantly increased TRPM8 mRNA and protein expression in OSCC cell lines. Lymph node metastasis showed a significant association with upregulated TRPM8 expression in combined OSCC and oropharyngeal squamous cell carcinoma (OPSCC) cases. TRPM8 mRNA expression was upregulated in HNSCC and OSCC patients with alcohol drinking and cigarette smoking habits, but not in betel quid chewing.

Conclusion

These findings reveal the involvement of TRPM8 in HNSCC's malignant development and metastasis, suggesting that high expression of TRMP8 may be mutually causal with addiction to tobacco, alcohol, and betel nut in HNSCC patients. Further investigations are needed to determine the underlying pathways of TRPM8 in HNSCC's development and progression.

Evaluation of sagittal root position and labial alveolar bone concavity in the maxillary anterior tooth area for immediate implant placement

BACKGROUND

The anatomical characteristics of the maxillary labial alveolar bone play a crucial role in the treatment planning of immediate implant placement. The sagittal root position (SRP) and alveolar bone concavity are closely related to anatomical characteristics in determining the ideal implant position. This study evaluated the SRP and labial alveolar bone concavity in the maxillary anterior teeth area.

METHODS

Cone-beam computed tomography images of 120 samples involving 720 teeth were uploaded to the medical imaging software. The SRP was classified as Class I, II, III, or IV, and the concavity of labial alveolar bone was measured. A T-test was performed to compare measurements between the central and lateral incisors, between the central incisors and canines, and between the lateral incisors and canine.

RESULTS

The majority of the sagittal root positions of the maxillary anterior teeth were class I (engaging the labial cortical plate) with frequencies of 98.3%, 85.8%, and 81.7% for the canines, lateral incisors, and central incisors, respectively. In terms of concavity of labial alveolar bone in maxillary tooth area, canines also had the largest mean value (139.5°), followed by lateral incisors, whereas central incisors has the smallest mean value (131.7°). The results of the T-test revealed a significant difference (p<0.001) in labial alveolar bone concavity between central and lateral incisors, between central incisors and canines, and between lateral incisors and canines.

CONCLUSION

Most maxillary anterior teeth were classified as Class I SRP, Class III SRP was the least prevalent, and the concavity of the labial alveolar bone significantly differed between the central and lateral incisors, between the central incisors and canines, and between the lateral incisors and canines. In addition, the canines had the highest mean alveolar bone concavity angle, indicating that less concavity in the canines area.

Patients with periodontitis are at a higher risk of stroke: A Taiwanese cohort study

BACKGROUND

This study aimed to investigate the risk of stroke incidence in patients with periodontitis.

METHODS

Data on patients diagnosed with periodontitis were collected from Taiwan's National Health Insurance Research Database and were matched (1:1) with patients without periodontitis between 2001 and 2010. A multivariable Cox survival model was used to predict stroke between patients with and without periodontitis, and the possibility of confounders. Hazard ratios (HRs) with 95% confidence intervals (CIs) were used to explore the risk of stroke in the case and control groups. Diseases found during the follow-up period were analyzed to determine possible effects on the study. A total of 282 560 periodontitis and nonperiodontitis patients were enrolled, with most subjects aged 40 to 59 years.

RESULTS

The overall cumulative incidence of stroke was 2.14 times higher in periodontitis than in nonperiodontitis, and the highest HR was in the more than 80 years age group (HR = 9.30; 95% CI, 7.06-12.26). The multivariate Cox model indicated that the adjusted HR (aHR) between the case and control was 2.03 (95% CI, 1.99-2.08), and a higher aHR was associated with hypertension. Atherosclerosis, atrial fibrillation, obesity, kidney disease, anxiety, and gout discovered during follow-up also showed a potential risk of stroke in patients with periodontitis.

CONCLUSION

Therefore, this study suggests a high risk of stroke in patients with periodontitis.

Biomechanical Analyses of Porous Designs of 3D-Printed Titanium Implant for Mandibular Segmental Osteotomy Defects

Clinically, a reconstruction plate can be used for the facial repair of patients with mandibular segmental defects, but it cannot restore their chewing function. The main purpose of this research is to design a new three-dimensionally (3D) printed porous titanium mandibular implant with both facial restoration and oral chewing function reconstruction. Its biomechanical properties were examined using both finite element analysis (FEA) and in vitro experiments. Cone beam computed tomography images of the mandible of a patient with oral cancer were selected as a reference to create 3D computational models of the bone and of the 3D-printed porous implant. The pores of the porous implant were circles or hexagons of 1 or 2 mm in size. A nonporous implant was fabricated as a control model. For the FEA, two chewing modes, namely right unilateral molar clench and right group function, were set as loading conditions. Regarding the boundary condition, the displacement of both condyles was fixed in all directions. For the in vitro experiments, an occlusal force (100 N) was applied to the abutment of the 3D-printed mandibular implants with and without porous designs as the loading condition. The porous mandibular implants withstood higher stress and strain than the nonporous mandibular implant, but all stress values were lower than the yield strength of Ti-6Al-4V (800 MPa). The strain value of the bone surrounding the mandibular implant was affected not only by the shape and size of the pores but also by the chewing mode. According to Frost's mechanostat theory of bone, higher bone strain under the porous implants might help maintain or improve bone quality and bone strength. The findings of this study serve as a biomechanical reference for the design of 3D-printed titanium mandibular implants and require confirmation through clinical investigations.

[QARS1 gene related glutaminyl-tRNA synthetase deficiency syndrome: report of three cases and a review of literature]

Objective: To investigate the clinical characteristics, treatment and prognosis of QARS1 gene related glutaminyl-tRNA synthetase deficiency. Methods: To summarize and analyze the clinical manifestations, imaging, laboratory examination, genetic variant characteristics and treatment of three patients from the Fujian Medical University Affiliated Union Hospital, the 900th Hospital of People's Liberation Army, the First Medical Center of People's Liberation Army General Hsopital carrying compound heterozygous variations in QARS1 gene with a long-term follow-up in China. A literature search was conducted using Wanfang, Weipu, China National Knowledge Infrastructure (CNKI) and Pubmed databases with the keywords "QARS", "QARS1" and "glutaminyl-tRNA Synthetase"(up to December 2019). Results: Case 1, a female 53 days of age, was admitted to the Fujian Medical University Affiliated Union Hospital for treatment because of the complaint of repetitive seizures for one month after birth and fever for one day. The seizure occurred within the first 2 hours of life with multiple forms and often had a status as persisted from hours to days. The seizures were resistant to many anti-epilepsy drugs (AED) and ketogenic diet but later controlled by clonazepam. However, she died at the age of seven years. Case 2 (younger brother of case 1), a one-hour-old boy, was hospitalized because of seizures after birth for 1 hour. Intrauterine growth retardation was discovered during late-pregnancy. The boy presented seizures and microcephaly immediately after birth, and his epilepsy was pharmacoresisitant. Case 3, an 8-month-old girl, was admitted due to recurrent convulsions for nearly two months. The girl had mild developmental retardation and hypotonia after birth. The infantile spasm was observed at her age of 6 months and disappeared under treatment with Vitamin B6, vigabatrin combined with adreno-cortico-tropic-hormone and magnesium sulfate. However, the seizure pattern turned to tonic seizures later. She was seizures free now with clobazam and zonisamide treatment. All of them manifested as a syndrome composed of severe global developmental retardation, progressive microcephaly, hypotonia from the very beginning, mild hypoproteinemia and diffuse brain atrophy. Genetic studies revealed compound heterozygous variations of QARS1 gene which were not reported previously. A review of the literature reported a total of 22 patients from 18 unrelated families all over the world. Except for 5 cases without epilepsy,all the patients shared very similar clinical manifestations as classic pentalogy. The recommended effective treatment for epilepsy has not been reported yet. Conclusions: Glutaminyl-tRNA synthetase deficiency caused by QARS1 gene variations manifested as a clinical syndrome's pentalogy, characterized by microcephaly, cerebral atrophy, intractable early-onset epileptic encephalopathy, global developmental retardation and severe muscle hypotonia.

Research Progress of Metabolomics in Forensic Pathology

Abstract

Metabolomics is an interdisciplinary subject that rose in the post-genomic era, which focuses on quantitative study of the response of living organisms to outside stimulation and pathophysiological changes, as well as multiple dynamic response of the level of in vivo metabolites caused by genetic mutation. It is extensively used in basic research of system biology, materia medica, clinical medicine, etc. In the forensic field, metabolomics mainly focuses on forensic toxicology, but with the generalization of certain techniques, it's foreseeable that metabolomics has a broad research prospect in forensic pathology. This article summarizes the major analysis techniques and methods of metabolomics, describes the research status of metabolomic techniques in the field of forensic pathology application research, including postmortem interval and death cause. Moreover, this article summarizes and discusses the potential applicable areas, in order to provide reference for relative research and application.

Oral Submucous Fibrosis: A Review on Biomarkers, Pathogenic Mechanisms, and Treatments

Oral submucous fibrosis (OSF) is a collagen deposition disorder that affects a patient’s oral function and quality of life. It may also potentially transform into malignancy. This review summarizes the risk factors, pathogenic mechanisms, and treatments of OSF based on clinical and bio-molecular evidence. Betel nut chewing is a major risk factor that causes OSF in Asia. However, no direct evidence of arecoline-induced carcinogenesis has been found in animal models. Despite identification of numerous biomarkers of OSF lesions and conducting trials with different drug combinations, clinicians still adopt conservative treatments that primarily focus on relieving the symptoms of OSF. Treatments focus on reducing inflammation and improving mouth opening to improve a patient’s quality of life. In conclusion, high-quality clinical studies are needed to aid clinicians in developing and applying molecular biomarkers as well as standard treatment guidelines.

In vitro antimicrobial and antipro-inflammation potential of honokiol and magnolol against oral pathogens and macrophages

BACKGROUND/PURPOSE

Honokiol and magnolol are natural components isolated from Magnolia bark that is used in traditional Chinese and Japanese herbal medicine. These two isomers are used as a component of dietary supplements and cosmetic products. In this study, we investigated the antimicrobial effect of honokiol and magnolol on pathogens causing oral diseases, their mechanism of action in biofilm formation and drug resistance of oral pathogens, and inflammatory regulation in mammalian cells.

METHODS

We determined the minimum inhibitory concentration and minimum bactericidal concentration of honokiol and magnolol, and their stability at different temperatures and pH. We also evaluated their effect on biofilm formation, antibiotic-resistance gene expression in MRSA, and pro-inflammatory gene expression in mammalian cells.

RESULTS

Honokiol showed better antimicrobial activity than magnolol. Both honokiol and magnolol showed stable bacterial inhibitory activity over a wide range of temperature and pH, reduced biofilm formation, and antibiotic resistance in oral pathogens. The biofilm formation- and antibiotic resistance-related gene expression was consistent with the respective phenotypes. Furthermore, these two isomers repressed the expression of pro-inflammatory genes in RAW264.7 cells.

CONCLUSION

Our study provides evidence of the potential application of honokiol and magnolol in dental medicine to cure or prevent oral diseases.

Relationship between Cortical Bone Thickness and Cancellous Bone Density at Dental Implant Sites in the Jawbone

Dental implant surgery is a common treatment for missing teeth. Its survival rate is considerably affected by host bone quality and quantity, which is often assessed prior to surgery through dental cone-beam computed tomography (CBCT). Dental CBCT was used in this study to evaluate dental implant sites for (1) differences in and (2) correlations between cancellous bone density and cortical bone thickness among four regions of the jawbone. In total, 315 dental implant sites (39 in the anterior mandible, 42 in the anterior maxilla, 107 in the posterior mandible, and 127 in the posterior maxilla) were identified in dental CBCT images from 128 patients. All CBCT images were loaded into Mimics 15.0 to measure cancellous bone density (unit: grayscale value (GV) and cortical bone thickness (unit: mm)). Differences among the four regions of the jawbone were evaluated using one-way analysis of variance and Scheffe's posttest. Pearson coefficients for correlations between cancellous bone density and cortical bone thickness were also calculated for the four jawbone regions. The results revealed that the mean cancellous bone density was highest in the anterior mandible (722 ± 227 GV), followed by the anterior maxilla (542 ± 208 GV), posterior mandible (535 ± 206 GV), and posterior maxilla (388 ± 206 GV). Cortical bone thickness was highest in the posterior mandible (1.15 ± 0.42 mm), followed by the anterior mandible (1.01 ± 0.32 mm), anterior maxilla (0.89 ± 0.26 mm), and posterior maxilla (0.72 ± 0.19 mm). In the whole jawbone, a weak correlation (r = 0.133, p = 0.041) was detected between cancellous bone density and cortical bone thickness. Furthermore, except for the anterior maxilla (r = 0.306, p = 0.048), no correlation between the two bone parameters was observed (all p > 0.05). Cancellous bone density and cortical bone thickness varies by implant site in the four regions of the jawbone. The cortical and cancellous bone of a jawbone dental implant site should be evaluated individually before surgery.

Application of Convolutional Neural Network in Identifying Different Levels of Isokinetic Exercise Efforts

Objective To develop a convolutional neural network （CNN） that can identify isokinetic knee exercises moment of force-time diagrams under different levels of efforts. Methods The 200 healthy young volunteers performed concentric isokinetic right knee flexion-extension reciprocating exercises with maximal effort as well as half the effort at angular velocities of 30°/s and 60°/s twice, respectively, with an interval of 45 min. The moment of force-time diagrams were collected. The 200 subjects were randomly divided into the training set （140 subjects） and the testing set （60 subjects）. The moment of force-time diagrams from subjects in the training set were used to train CNN model, and then the fully trained model was used to predict types of curves from the testing set. Random sampling of subjects along with subsequent development of models were performed 3 times. Results Under the circumstances of isokinetic knee exercises with maximal effort and half the effort, 2 400 moment of force-time diagrams were produced, respectively. Classification accuracy rates of the CNN models after the 3 trainings were 91.11%, 90.49% and 92.08%, respectively, and the average accuracy rate was 91.23%. Conclusion The CNN models developed in this study have a good effect on differentiating isokinetic moment of force-time diagrams of maximal effort exercises from those made with half the effort, which can contribute to identifying levels of efforts exerted by subjects during isokinetic knee exercises.

Clinical assessment of the palatal alveolar bone thickness and its correlation with the buccolingual angulation of maxillary incisors for immediate implant placement

BACKGROUND

Clinicians needed to be aware of the thinness of the palatal bone plate when identifying severe protrusion of maxillary incisors, as this could result in perforation of the palatal bone plate during surgical procedures associated with immediate maxillary implant placement.

PURPOSE

This study evaluated the thickness of the palatal bone plate, the buccolingual angulation of maxillary incisors, and the correlation between these two parameters in relation to immediate implant placement.

MATERIALS AND METHODS

Cone-beam computed tomography images of 37 Asian patients (20-60 years old) with no evidence of dental treatment in the maxillary incisor area were collected and classified into groups based on sex and incisor locations. Sagittal slices were used to measure the palatal bone plate thickness at the cervical, middle, and apical levels, and the buccolingual angulation of each tooth was also measured. The intraclass correlation, Shapiro-Wilk test, descriptive analysis, Student's t-test, and Pearson correlation were used for statistical and correlation analyses, with P < .05 applied as the criterion for statistical significance.

RESULTS

At the apical level of all inspected teeth and the middle level of lateral incisors, the palatal bone was significantly thicker in males than in females. The inclination of the maxillary lateral incisor showed a moderate negative linear correlation with the palatal bone thickness at the apical level (R = -0.517 and R = -0.579 for males and females, respectively).

CONCLUSIONS

In an Asian population, an increased buccolingual angulation of the maxillary lateral incisors was correlated with a thinner palatal bone plate at the apical level.

Difference Analysis Based on 16S rRNA Sequencing of Different Soil Bacterial Communities

Abstract

Objective To study the structure and differences of bacterial communities in different soils, and to explore the effectiveness of 16S rRNA sequencing in identification of different soil. Methods Soil samples from 7 places in Shanghai were collected, then bacterial genomic DNA were extracted from them. The fragments of hypervariable region from 16S rRNA sequences were sequenced with high-throughput sequencing techniques. The results were quantified or visualized with bioinformatics software. The differences in diversity and abundance among the three kinds of bacterial communities in soil samples from grassland, forests and beaches were compared and analyzed. Results The statistical differences that existed among the alpha diversity indexes of bacterial communities in soil samples of grassland, forests and beaches had statistical significance. The relative abundance and diversity of bacterial communities in these three kinds of soil were significantly different. Grassland soil had higher Acidobacteria abundance, forest soil had higher Proteobacteria abundance, beach soil had higher Actinobacteria abundance. However, the differences in soil bacterial communities in artificial grasslands, natural grasslands and industrial district grasslands did not have statistical significance. Conclusion 16S rRNA sequencing can effectively distinguish different soils. This method may be able to provide clues for first crime scene inference in criminal cases.

Self-assembled micro-computed tomography for dental education

This study used available or purchased equipment and an image reconstruction system developed by the college of dentistry to establish a basic self-assembled micro-computed tomography (micro-CT) system. Such a system would be suitable for teaching dental radiology to dental students. Specifically, it could help students to understand the principles governing dental cone-beam computed tomography (CBCT) and provide graduate students with a system for scanning small samples (e.g., individual teeth) during the early stages of research. The self-assembled micro-CT system was constructed using a portable dental X-ray tube, an intraoral digital X-ray detector, a high-precision rotation stage, related bracket accessories, and a notebook computer. Reconstructed images and three-dimensional models of the maxillary right third molar were produced using the self-assembled micro-CT system and an advanced commercially available micro-CT system (Skyscan 2211). Subsequently, the reconstructed images and 3D models produced using the two systems were compared by two senior dentists to determine whether considerable visual differences could be observed. Finally, the signal-to-noise ratio (SNR) was used for quantitative analysis and to compare the systems. Although the self-assembled micro-CT system produced image boundaries that were not as sharp as those of Skyscan 2211, the images were nonetheless remarkably similar. In addition, the two micro-CT systems produced 3D models that were almost identical in appearance and root canal shape. Quantitative analysis revealed that Skyscan 2211 had produced a SNR that was superior to that of the self-assembled micro-CT system, with the difference ranging from 36.77% to 136.22%; enamel, which has a higher density, exhibited lower SNR differences, whereas dentin, which has a lower density, exhibited higher SNR differences. The self-assembled micro-CT system with a resolution of 36 μm was created using a portable dental X-ray tube and an intraoral digital X-ray detector. Although the scanning time was relatively long (~30 min to scan images of a tooth), the images were adequate in the preliminary stage of experiments. More importantly, students were afforded the opportunity to observe the process of assembling and disassembling each component of a micro-CT scanner and thereby achieve a more comprehensive understanding of the principles governing micro-CT and dental CBCT.

Forensic Analysis of 24 Cases of Long-term Antipsychotics Use-Induced Sudden Unexpected Deaths

OBJECTIVES

To analyze the forensic characteristics of 24 psychiatric patients who died of long-term use of psychotropic drugs.

METHODS

Cases of sudden death of psychiatric patients from 2011 to 2016 were collected. The forensic characteristics of these sudden deaths were retrospectively analyzed by systematic investigation plus results of autopsy and toxics （drugs）.

RESULTS

Among the 24 psychiatric patients who died of long-term use of psychotropic substances, the ratio of male to female was 1.7∶1, and the average age was （59.0±8.8） years. Fifteen patients had clear disease durations （14.4±8.2） years, and other the nine were known to have disease durations of over 3 years. The death time of 62.5% of patients was the daytime in working days, and 91.7% of the patients died at home. Most patients complained different degrees of physical discomfort before death. Patients with schizophrenia （20 cases） were the most common, followed by depression （4 cases）. All patients had the history of taking psychotropic drugs, with clozapine and chlorpromazine being the mostly detected ones. The causes of death were mainly circulatory diseases （15 cases）, with the most common being myocarditis （11 cases） followed by pneumonia （4 cases）.

CONCLUSIONS

Critical attention should be paid to the risk of antipsychotics-induced sudden unexpected deaths for psychiatric patients, particularly for those with schizophrenia.

[Research Progress of CircRNA and Its Application Prospect in Forensic Medicine]

Circular RNA （circRNA） is a type of noncoding RNA with tissue specificity and high stability, which forms a closed continuous loop and is abundantly expressed in tissue cells. According to recent research, the regulatory function of circRNA elucidating in the occurrence and development of disease shows a potential for diagnosing clinical disease and revealing disease mechanism. This paper reviews the biological characteristics, analysis methods of circRNA and its research progress in clinical application as biomarker, and outlooks its application in the field of forensic medicine.

Computer-assisted system on mandibular canal detection

BACKGROUND

A dentist always checks a patient by using panoramic radiography (PR) initially. The measurement of the minimal distance (MD) between the alveolar crest and the mandibular canal (MC) superior border is critically important before the dental implant surgery, extraction of 3rd molar teeth or any surgery in the posterior area of minimal distance (MD). However, the image of MC is not always clear to identify.

OBJECTIVE

A software is needed for training dentists as well as a tool of demonstration to patients in clinics precisely and quickly. Moreover, it should be able to calculate the MD between the alveolar crest and the MC superior border before dental implant.

METHODS

A computer-aided software system to semi-automatically detect the MC and mental foramen (MF) in the PR with minimal human interference is proposed.

RESULTS

The result shows that the averaged relative error (RE) is 1.83% with a standard deviation of 2.31%.

CONCLUSION

The results show that the proposed algorithm is able to detect the MC superior and inferior borders. This system has the potential to train young clinicians and to replace the manual work in measuring the MD between the alveolar crest and the MC superior border with a minimal human intervention.

Impacts of 3D bone-to- implant contact and implant diameter on primary stability of dental implant

BACKGROUND/PURPOSE

This study investigated the effects of three three-dimensional (3D) bone-to-implant contact (BIC) parameters-potential BIC area (pBICA), BIC area (BICA), and 3D BIC percentage (3D BIC%; defined as BICA divided by pBICA)-in relation to the implant diameter on primary implant stability, as well as their correlations were also evaluated.

METHODS

Dental implants with diameters of 3.75, 4, 5, and 6 mm and artificial bone specimens were scanned by microcomputed tomography to construct 3D models for calculating pBICA, BICA, and 3D BIC%. Indexes of the primary implant stability including the insertion torque value (ITV), Periotest value (PTV), and implant stability quotient (ISQ) were measured after implants with various diameters were placed into bone specimens. The Kruskal-Wallis test, Wilcoxon rank-sum test with Bonferroni adjustment, and Spearman correlations were all performed as statistical and correlation analyses.

RESULTS

The implant diameter significantly influenced pBICA and BICA, but not 3D BIC%. ITV and PTV were more sensitive to implant diameter than was ISQ. The coefficients of determination were high (>0.92) for the correlations between pBICA (or BICA) and indexes of the primary implant stability.

CONCLUSION

This study revealed how the implant diameter and the three-dimensional (3D) BIC influence the primary stabilities of dental implant. ITV and PTV were more sensitively influenced by the implant diameter than ISQ. The pBICA and BICA seem to be more important than 3D BIC % for using wider implant in treatment plan, since those two parameters are highly predictive of variations in the primary stability of dental implant.

Variations in crestal cortical bone thickness at dental implant sites in different regions of the jawbone

BACKGROUND

Dental implants have become reliable and predictable tools for treating missing teeth. The survival rate of dental implants is markedly influenced by the host bone quality and quantity of the jawbone. A better host bone provides higher initial stability of the dental implant, resulting in better osseointegration and a higher success rate. Host bone quality and quantity are determined by the crestal cortical bone thickness and inner cancellous bone density.

OBJECTIVE

The purpose of this study was to determine the crestal cortical bone thickness at dental implant sites in different regions of the jawbone through the use of dental cone-beam computed tomographic (CBCT) images.

MATERIALS AND METHODS

A total of 661 dental implant sites (81 in the anterior mandible, 122 in the anterior maxilla, 224 in the posterior mandible, and 234 in the posterior maxilla) were obtained from the jawbones of 173 humans. The data were subjected to statistical analysis to determine any correlation between crestal cortical bone thicknesses and jawbone regions using one-way analysis of variance with Tukey's post-test.

RESULTS

The crestal cortical bone thicknesses at dental implant sites in the four regions decreased in the following order: posterior mandible (1.07 ± 0.47 mm, mean ± SD) >anterior mandible (0.99 ± 0.36 mm) >anterior maxilla (0.82 ± 0.30 mm) >posterior maxilla (0.75 ± 0.35 mm).

CONCLUSION

The dental CBCT data demonstrate that crestal cortical bone thickness varies markedly between dental implant sites in the four regions of the jawbone.

Biomechanical investigation of thread designs and interface conditions of zirconia and titanium dental implants with bone: three-dimensional numeric analysis

PURPOSE

Bone stress and interfacial sliding at the bone-implant interface (BII) were analyzed in zirconia and titanium implants with various thread designs and interface conditions (bonded BII and contact BIIs with different frictional coefficients) for both conventional and immediately loaded treatments.

MATERIALS AND METHODS

A total of 18 finite element models comprising two implant materials (zirconia and titanium), three thread designs (different shapes and pitches), and three interface conditions (bonded and contact BIIs) were analyzed to assess the effects on bone stresses and on sliding at the BII. The material properties of the bone model were anisotropic, and a lateral force of 130 N was applied as the loading condition.

RESULTS

In the immediately loaded implant, the stress was highly concentrated at one site of the peri-implant bone. The peak bone stress was more than 20% lower in zirconia implants than in titanium implants for a bonded BII and 14% to 20% lower for a contact BII. The bone stresses did not differ significantly between implants with V-shaped threads and square threads. However, sliding at the BII was more than 25% lower with square-thread implants than with V-shaped-thread implants for titanium implants and 36% lower for zirconia implants. Reducing the thread size and pitch in cortical bone (via two V-shaped threads with different pitches) decreased the bone stress by 13%. Increasing the frictional coefficient reduced sliding at the BII in both zirconia and titanium implants.

CONCLUSIONS

As an implant material, zirconia can reduce the bone stress in the crestal cortical region. Bone stress and sliding at the BII are heavily dependent on the thread design and the frictional coefficient at the BII of immediately loaded implants.

Comparisons of maximum deformation and failure forces at the implant-abutment interface of titanium implants between titanium-alloy and zirconia abutments with two levels of marginal bone loss

Background

Zirconia materials are known for their optimal aesthetics, but they are brittle, and concerns remain about whether their mechanical properties are sufficient for withstanding the forces exerted in the oral cavity. Therefore, this study compared the maximum deformation and failure forces of titanium implants between titanium-alloy and zirconia abutments under oblique compressive forces in the presence of two levels of marginal bone loss.

Methods

Twenty implants were divided into Groups A and B, with simulated bone losses of 3.0 and 1.5 mm, respectively. Groups A and B were also each divided into two subgroups with five implants each: (1) titanium implants connected to titanium-alloy abutments and (2) titanium implants connected to zirconia abutments. The maximum deformation and failure forces of each sample was determined using a universal testing machine. The data were analyzed using the nonparametric Mann–Whitney test.

Results

The mean maximum deformation and failure forces obtained the subgroups were as follows: A1 (simulated bone loss of 3.0 mm, titanium-alloy abutment) = 540.6 N and 656.9 N, respectively; A2 (simulated bone loss of 3.0 mm, zirconia abutment) = 531.8 N and 852.7 N; B1 (simulated bone loss of 1.5 mm, titanium-alloy abutment) = 1070.9 N and 1260.2 N; and B2 (simulated bone loss of 1.5 mm, zirconia abutment) = 907.3 N and 1182.8 N. The maximum deformation force differed significantly between Groups B1 and B2 but not between Groups A1 and A2. The failure force did not differ between Groups A1 and A2 or between Groups B1 and B2. The maximum deformation and failure forces differed significantly between Groups A1 and B1 and between Groups A2 and B2.

Conclusions

Based on this experimental study, the maximum deformation and failure forces are lower for implants with a marginal bone loss of 3.0 mm than of 1.5 mm. Zirconia abutments can withstand physiological occlusal forces applied in the anterior region.

Bone stress and interfacial sliding analysis of implant designs on an immediately loaded maxillary implant: a non-linear finite element study

OBJECTIVES

This study investigated the surrounding bone stress and the implant-bone interfacial sliding of implant designs and implant sizes of immediately loaded implant with maxillary sinus augmentation by using three-dimensional (3D) non-linear finite element (FE) analysis.

METHODS

Twenty-four FE models including four implant designs (cylindrical, threaded, stepped and step-thread implants) and three implant dimensions (standard, long and wide threaded implants) with a bonded and three levels of frictional contact of implant-bone interfaces were analyzed. The maxillary model was constructed from computer tomography (CT) images of a human skull and all 3D implant models were created via the computer-aided design (CAD) software.

RESULTS

The use of threaded implants decreased the bone stress and sliding distance obviously about 30% as compared with non-threaded (cylindrical and stepped) implants. Increasing the implant's length or diameter reduced the bone stress by 13-26%. Employing a immediately loaded implant with smooth machine surface (mu=0.3, mu represents frictional coefficient) increased the bone stress by 28-63% as compared with the osseointegrated (bonded interfaces) implants. Roughening the implant surface (mu>0.3) did not reduced the bone stress, however it did decrease the interfacial sliding between implant and bone.

CONCLUSIONS

For an immediately loaded implant placed with sinus augmentation, using threaded implant could decrease both the bone stress and implant-bone sliding distance which may improve the implant initial stability and long-term survival. Rough surface of implants shows no benefit to reduce the bone stress but they could lower the interfacial sliding. On the contrary, employing long or wide implants decrease the bone stress but they cannot diminish the interfacial sliding.

[Experimental study of mechanism and measures of prevention and treatment of hypothermal vasoconstriction]

OBJECTIVE

To investigate the mechanism and to explore the measures of prevention and treatment of hypothermal vasoconstriction.

METHODS

By the techniques of endothelial cell culture and scanning electron microscopy, and vasomotor functional test of isolated vascular vessels, the relation of hypothermal vasoconstriction and the release of endothelium-derived contractile and vasodilative factors were observed.

RESULTS

Hypothermia obviously induced vasoconstriction of isolated vascular vessels, whether endothelium was intact or removed, the lower the temperature, the higher the vascular tension. Removal of endothelium could decrease the effect of vasoconstriction by hypothermia. The conditioned medium of bovine aortic endothelial cell could induce significantly vasoconstriction of isolated rat common neck arterial ring in hypothermia. It indicated that the bovine aortic endothelial cells secreted contractile factors into the medium. Reheating to 37 degrees C or vasodilator or reheating plus vasodilator did not obviously influence the hypothermia-induced vasoconstriction within 2 hours. When reheating to 50 degrees C, vascular tension was decreased, but only changed in range of 28% to 42%.

CONCLUSION

Hypothermia vasoconstriction is relative to vasoconstrictor factors secreted by endothelium. Reheating to 37 degrees C or vasodilator does not antagonize the constriction of vascular vessels. Reheating to 50 degrees C only partially eliminates the constrict effect of blood vessels, so the prevention of hypothermia vasoconstriction should be emphasized.

[The foundation of the injury model on cultured human fetal lung fibroblasts and its immunohistochemistry research]

Cultured human fetal lung Fbs was first used to study the relationship between wound age and the change of cFn synthesized by Fbs in Vitro. A sterilized injector was applied to scrap the cultured confluent Fbs and a "wound" was obtained. Fbs around the wound was seen to change from a stationary stage to an active stage. Using the method of immunochemistry and image analysis system (IAS), cFn synthesized by Fbs around the wound was observed at once, 30 min, 1 h, 3 h and 6 h after injury. It was found that cFn began to change 1 h after injury and increased continually within 6 h. It suggests that the change of cFn synthesized by Fbs is time-dependent after injury and this approach breaks a new path in the study on estimation of wound age.

[Clinical significance of changes in ophthalmic arterial flow in pregnancy induced hypertension monitored by color Doppler imaging]

Ophthalmic arterial flow parameters were measured by color doppler imaging in 30 cases of healthy non-pregnant women, 30 cases of normal pregnancy and 37 cases of pregnancy induced hypertension (PIH), together with left ventricular output determination. An elevation of 2nd peak, B/A ratio and all parameters but RI was recognized as the characteristics of ophthalmic arterial flow spectrum in PIH. A positive correlation was observed between these changes and severity of PIH. All parameters returned to normal as PIH was controlled either after treatment or after delivery. Ophthalmic arterial flow monitoring might be useful in diagnosis of PIH (sensitivity 82%, specificity 98%). and for prognosis of PIH.

A new family of fucose-containing gangliosides isolated from human senile cataracts

Gangliosides were isolated from human cataracts by solvent extraction, silicic acid chromatography, thin-layer chromatography and gas-liquid chromatography. A total of 11 resorcinol-positive bands were revealed by thin-layer chromatography. Bands 1, 5 and 7 were partially identified as hematoside. GM1 ganglioside and disialoganglioside by gas-liquid chromatography as the O-trimethylsilylated methylglycosides. In addition to galactose and glucose, fucose was found to be present in seven ganglioside fractions (bands 3, 4, 6 and 8-11). All these fucolipids contained N-acetylglucosamine in addition to sialic acid. Fucogangliosides G-3, G-4 and G-6 contained a 2:1 molar ratio of galactose to glucose, while G-8 had a galactose/glucose molar ratio of 1:1. Long-chain fatty acids constituted 60-77% of the total normal fatty acids in N-acetylgalactosamine-containing gangliosides, whereas the fucogangliosides contained primarily palmitate, although significant amounts of long-chain acids were also detected. The major long-chain base of the fucoganglioside was sphinganine (dihydrosphinogosine). The role of fucose-containing gangliosides in maintaining adhesions between lens membranes in cataracts is discussed with reference to glycosphingolipids in other tissues.

The presence of ceramide hydrolase and synthetase in pig lens epithelium

An enzyme that catalyzes the synthesis of ceramide and its degradation to sphingosine and fatty acid has been found in pig lens epithelium. The enzyme has been partially purified fivefold by subcellular fractionation. It is activated by Triton X-100 and sodium cholate. The pH optimum for both hydrolase and synthetase has occurred at alkaline range. The enzymatic hydrolysis of ceramide has an apparent Km of 1.0 x 10(-4) M, and its reverse reaction (via the free-acid pathway) has an apparent Km of 8.2 X 10(-5) M and 2.45 X 10(-4) M for palmitic acid and sphingosine, respectively. The hydrolysis of ceramide by this enzyme was stimulated approximately 75% in the presence of fatty acid-free bovine serum albumin at the concentration of 3.33 X 10(-5) M.

Isolation and partial characterization of fucose- and N-acetylglucosamine-containing neutral glycosphingolipids from human senile cataracts

Five neutral glycosphingolipids were isolated from human cataracts using silicic acid column chromatography and preparative thin-layer chromatography. Three of these glycolipids were partially identified by gas-liquid chromatography as glucosylceramide, lactosylceramide, and trihexosylceramide. Two glucosamine-containing glycosphingolipids (one of which contained fucose) were also detected. One of these two lipids contained galactose, glucose, N-acetylglucosamine in the molar ratio of 2:1:1, while the other contained fucose, galactose, glucose, and N-acetylglucosamine with the molar ratio of 1:2:1:1. Dihydrosphingosine (sphinganine) was the major long-chain base detected in all these fractions. The fatty acids of these neutral glycosphingolipids were variable in chain length, although the majority of them were greater than 20 carbons. This represents the first time whereby a family of neutral glycosphingolipids has been detected in human cataracts. This is also the first demonstration of the existence of a neutral fucolipid in the lenses of any species.