[A case of high-pressure injection injury of hand complicated with deep chemical burn caused by industrial cement].

This article reports a patient with extensive high-pressure injection injury of the hand combined with deep chemical burn caused by high-pressure injection of industrial cement materials was diagnosed and treated in the Department of Hand Surgery, Xiaolan Hospital Affiliated to Southern Medical University in 2022. The nerves, tendons and blood vessels of the left hand were involved, and the ulnar skin of the left thumb was extensively necrosis, and a large number of extensive cement foreign bodies remained under the skin. Part of the cement was inserted into the joint capsule of the interphalangeal joint. After emergency surgical treatment, the patient was saved successfully, and the wound healed well without chemical poisoning and other related complications, which created conditions for the second stage of flap repair.

[A prevalence survey of cone-beam computed tomography use among endodontic practitioners].

OBJECTIVE: To investigate the clinical application of cone-beam computed tomography (CBCT) among endodontic practitioners, and to analyze the indications and reasonability of CBCT in the diagnosis and treatment of pulpal and periapical diseases. METHODS: The clinical data were collected from patients who visited the Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology and underwent CBCT examination from January to December, 2021. The data with their complete clinical information (including clinical records, radiology request forms/reports, two-dimensional and three-dimensional imaging data) were included. Those who underwent CBCT examination for orthodontic or prosthodontics were excluded. The experience and training background of the endodontic specialists, the number of patients treated in the whole year, the objective and region of interest (ROI) of CBCT examination, technical parameters, such as machine type, field of view (FoV) and radiographic reports were collected and analyzed to evaluate the impact on diagnosis. Wilcoxon and Mann-Whitney tests were used to compare the distribution of CBCT ROI. Chi-squared test and pairwise comparison were used to compare the application of CBCT by endodontic specialists with different clinical experience (senior, middle and junior). RESULTS: In 2021, a total of 3 308 CBCT scans were prescribed by 61 endodontic specialists who treated 34 952 patients throughout the year. 3 218 patients (male ∶female about 1 ∶2) amounting for 10% of the patients treated in the whole year who received CBCT scans with an median age of 35 years (28, 49). Around 98% CBCT examinations were performed after clinical examination and two-dimensional periapical radiographs were taken. The FoV of CBCT scanning less than 10 cm×10 cm accounted for 96% of the total number of the images. Among the 3 308 CBCT scans, 83% of the ROI were in posterior teeth, with a higher number of anterior teeth (Z=-2.278, P < 0.05). Maxillary and mandibular first molars accounted for 35% of the examined teeth. The objectives of CBCT scanning included three aspects: clarifying clinical diagnosis, guiding surgical and non-surgical endodontic treatment (including management of endodontic complications), and outcome assessment, accounting for 1 111 (34%), 1 745 (54%), 311 (10%), respectively. and the others 2%. In the diagnosis process, CBCT was mainly used for the diagnosis of chronic periapical periodontitis, root fracture, root resorption and dental trauma. In the study, 353 CBCT were used in the diagnosis of root fracture, with a positive diagnosis rate of 35% (125/353). 846 CBCT used to reveal the anatomy of the root canal system, of which 297 cases were used to find missed/extra canals after treatment failure, and 58% (171/297) were used to confirm the missed/extra canals. In the management of complications or errors, CBCT was mainly used to assist the diagnosis of perforation and to locate the separated instruments. In the study, 311 CBCT scans were used for outcome assessment, including 240 cases related to non-surgical treatment and 71 cases related to surgical endodontic treatment for follow-up or presence of clinical symptoms, and persistent lesions on 2D films. Among the 61 endodontic specialists who used CBCT, 23 (45%) were with senior experience, 15 (30%) with middle experience, and 23 (25%) with junior experience. The proportion of senior or junior experience prescribing CBCT examination was 10%, higher than that of middle experience (8%, χ12=39.4, χ22=29.1, P < 0.001). The application rate of chief endodontists was 18%, which was higher than that of associate chief endodontists (9%, χ12=139.4, P < 0.001). 31% (1 109/3 308) cases of diagnosis or treatment plans were changed after CBCT was taken. CONCLUSION: Use of CBCT in endodontic practice could provide more clinical information, which is helpful for diagnosis, accurate treatment and prognosis evaluation.

[Relationship between auditory hallucination and regional homogeneity of functional magnetic resonance imaging in first-episode childhood and adolescence-onset schizophrenia].

Objective: To investigate the characteristics of regional homogeneity (ReHo) of the resting-state magnetic resonance imaging (fMRI) in first-episode childhood and adolescence-onset schizophrenia (CAOS) and to analyze the relationship between the severity of auditory hallucinations and ReHo. Methods: Seventy-nine cases of first-episode CAOS patients (case group) aged 10 to 16 were collected from October 2017 to December 2019 in the Second Affiliated Hospital of Xinxiang Medical University. There were 28 males and 51 females with a mean age of (14.1±1.3) years. And meantime, 32 healthy children matched with the patients in baseline data were selected as healthy controls (HCs). The patients with CAOS were divided into three groups according to the auditory verbal hallucinations (AVH) assessment of positive symptoms scale (SAPS): non-AVH group (0-1 point), 20 cases; mild-to-moderate AVH group (2-3 points), 36 cases; severe AVH group (4-5 points), 23 cases. The severity of psychiatric symptoms was evaluated using the Positive and Negative Syndrome Scale (PANSS). ReHo analysis was performed on the resting state fMRI scan data of all subjects. Covariance analysis (ages was used as a covariate) was performed between the case group and the HCs, and the three case groups were analyzed to find the different brain areas. Finally, covariance analysis (ages as a covariate) was performed on ReHo values between the case group and the HCs, and among the three groups of patients. Correlation analysis was conducted between the ReHo values in different brain regions and PANSS scores, as well as AVH scores. Results: Compared with the HCs, the decreased ReHo of patients were mainly located in the left superior frontal gyrus, right superior temporal gyrus, left central anterior gyrus, and right central anterior gyrus (all P<0.05). Besides, the ReHo deficits were in the right superior temporal gyrus, left middle frontal gyrus, precuneus lobe, and left central anterior gyrus among the three groups (all P<0.05). Moreover, the severe-AVH group showed decreased ReHo values in precuneus lobe compared with the non-AVH group (P<0.05), and showed decreased ReHo values in left middle frontal gyrus and left central anterior gyrus compared with the mild-to-moderate AVH group (both P<0.05). Furthermore, the ReHo in the right superior temporal gyrus and the left anterior central gyrus were negatively correlated with the AVH score (rs=-0.34, -0.32, P<0.05); and the positive symptom score was negatively correlated with the ReHo in the right superior temporal lobe (r=-0.23, P<0.05). Conclusion: Firstly, decreased ReHo is found in multiple brain regions in CAOS. Secondly, the occurrence of auditory hallucinations may be related to the abnormal activity of local neurons in the resting state. Consequently, Abnormal brain function may be the underlying neural basis for the first-episode CAOS.

[Association between osteoporosis and severe periodontal attachment loss in postmenopausal women].

Objective: To investigate the association between osteoporosis and severe periodontal attachment loss in postmenopausal women. Methods: One hundred and ninety-five postmenopausal women aged 50-65 years old were included in the present study. The participant were recruited from patients in the Peking University International Hospital and through website from March, 2017 to August, 2018. Periodontal examination, filling out a structured questionnaire and bone mass density (BMD) examination were completed to each of the participants. The clinical attachment loss (CAL), oral hygiene index simplified (OHI-S), and bleeding on probing (BOP) were examined and recorded as periodontal parameters. The structured questionnaire was used to collect information of the physical activity, socioeconomic status, marital status, oral health habits, and so on. Bone mass density of the lumbar spine and left hip were scanned by using standardized dual energy X-ray absorptiometry. Based on the T-score of BMD (difference between the measured BMD and the mean value of young white women in terms of standard deviations), osteoporosis was defined as T-score≤-2.5 (according to the World Health Organization criteria). Fourteen risk factors were preliminarily screened by chi-square test, including age, duration of menopause, body mass index (BMI), exercise habit, economic status, marital status, level of education, habit of dental visit, tooth brushing habit, usage of interdental tools, OHI-S, BOP(+)%, osteoporosis in hip and osteoporosis in lumbar. Factors with P<0.05 were selected for multivariate Logistic regression analysis. Logistic regression was used to analysis the risk factors of severe periodontal attachment loss. Results: The mean age of 195 postmenopausal women was (57.8±4.3) years. After adjusting for ages, the economic status, habit of dental visit, OHI-S and BOP(+)%, there was an association of osteoporosis in hip and severe periodontal attachment loss in postmenopausal women [odds ratios (OR)=2.466, 95% confidence intervals (CI) was 1.173-5.185, P=0.017]. Conclusions: Postmenopausal women with osteoporosis in hip has a greater chance of presenting severe periodontal attachment loss.

LncRNA HANR aggravates the progression of non-small cell lung cancer via mediating miRNA-140-5p.

OBJECTIVE: The aim of this study was to elucidate the function of long non-coding ribonucleic acids (lncRNAs) HANR in aggravating non-small cell lung cancer (NSCLC) progression via targeting microRNA-140-5p (miRNA-140-5p). PATIENTS AND METHODS: The relative expression level of HANR in NSCLC tissues and cell lines was determined by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The correlation between HANR expression and the prognosis of NSCLC was analyzed. The regulatory effects of HANR on cellular behaviors of NSCLC cells were evaluated by Cell Counting Kit-8 (CCK-8), transwell and wound healing assay. Meanwhile, the relative expression of miRNA-140-5p in NSCLC tissues and cell lines was determined by qRT-PCR. In addition, rescue experiments were carried out to evaluate the potential influence of HANR/miRNA-140-5p on the progression of NSCLC. RESULTS: HANR expression was significantly up-regulated in NSCLC tissues and cell lines. HANR expression was positively correlated with lymphatic metastasis and distant metastasis of NSCLC patients, whereas it was negatively correlated with the overall survival of NSCLC patients. Knockdown of HANR markedly suppressed the proliferative, migratory and invasive abilities of NSCLC cells. In NSCLC tissues, the miRNA-140-5p level was negatively associated with HANR level. Furthermore, inhibited cellular behaviors of NSCLC cells transfected with sh-HANR were partially reversed after miRNA-140-5p knockdown. CONCLUSIONS: LncRNA HANR accelerates the proliferative, migratory and invasive abilities of NSCLC via negatively mediating miRNA-140-5p. Furthermore, HANR is closely correlated with lymphatic metastasis, distant metastasis and poor prognosis of NSCLC.

The effect of orbital-lattice coupling on the electrical resistivity of YBaCuFeO5 investigated by X-ray absorption.

Temperature-dependent X-ray absorption near-edge structures, X-ray linear dichroism (XLD) and extended X-ray absorption fine structure (EXAFS) spectroscopic techniques were used to investigate the valence state, preferred orbital and local atomic structure that significantly affect the electrical and magnetic properties of a single crystal of YBaCuFeO5 (YBCFO). An onset of increase of resistivity at ~180 K, followed by a rapid increase at/below 125 K, is observed. An antiferromagnetic (AFM)-like transition is close to the temperature at which the resistivity starts to increase in the ab-plane and is also observed with strong anisotropy between the ab-plane and the c-axis. The XLD spectra at the Fe L3,2-edge revealed a change in Fe 3d eg holes from the preferential [Formula: see text] orbital at high temperature (300-150 K) to the [Formula: see text] orbital at/below 125 K. The analysis of the Fe K-edge EXAFS data of YBCFO further revealed an unusual increase in the Debye-Waller factor of the nearest-neighbor Fe-O bond length at/below 125 K, suggesting phonon-softening behavior, resulting in the breaking of lattice symmetry, particularly in the ab-plane of Fe-related square pyramids. These findings demonstrate a close correlation between electrical resistivity and coupling of the preferred Fe 3d orbital with lattice distortion of a single crystal of YBCFO.

[Relationship between periodontitis and osteoporosis in postmenopausal women].

OBJECTIVE: To explore the relationships of periodontal parameters, cortical width on mental foramen and osteoporotic condition in postmenopausal women. METHODS: Ninetyeight postmenopausal women between 50 to 65 years old were recruited. General conditions, such as age, menopausal age, duration of menopause, and body mass index (BMI) were recorded. Periodontal parameters were examined, including oral hygiene index simplified (OHI-S), probing depth (PD), clinical attachment loss (CAL), gingival recession (GR) and bleeding on probing (BOP). Panoramic radiograph was taken and the cortical width (CW) of mental foramen was measured on images. The examiner was celebrated. Bone mass density (BMD) of left hip and lumbar spine was assessed using standardized dual energy X-ray absorptiometry. According to World Health Organization, based on the T-score of BMD (difference of the measured BMD and the mean value of young white women in terms of standard deviations), the subjects were divided into osteoporotic group (T-score<-2.5) and non-osteoporotic group (T-score≥-2.5). These parameters were compared between the groups. RESULTS: The number of osteoporotic group was 47 (47.96%). Ages and duration of menopause were significantly different between the groups. Osteoporotic group presented older ages [(59.64±4.58) years vs. (56.94 ± 4.26) years, P<0.05], and longer duration of menopause [(10.17± 5.37) years vs. (6.02 ±4.48) years, P<0.05]. There was no significant difference in menopausal age and BMI between the groups. BOP% was statistically significantly higher in osteoporotic group (29.43±21.12) than in non-osteoporotic group (21.43±17.09), with a P-value of 0.046. The other periodontal parameters, including OHI-S, PD, CAL, and GR were not statistically significantly different in the groups. The CWs were statistically significantly lower in osteoporotic group compared with non-osteoporotic group, with a P-value of 0.001. The mean values of CWs were (3.61±1.04) mm (osteoporotic group) and (4.25±0.77) mm (non-osteoporotic group), respectively. CONCLUSION: The study demonstrated absence of a significant association between periodontal parameters and BMD. However, the CWs were found to be related with the BMD, which may be used to detect BMD abnormal in maxillofacial imaging. The dentists should pay attention not only to the oral health, but also to the general bone mass density, which may be detected on panoramic images.

[Effects of different methods on drying root canal by near-field microwave detection system].

OBJECTIVE: To set up near-field microwave detection system, to evaluate the accuracy of measuring water and to compare the effects of different methods on drying root canal. METHODS: Known and quantitative distilled water in Eppendorf tube and root canal was detected by near-field microwave detection system which was set up first. The microwave reflection coefficient was recorded so as to evaluate the accuracy of the measuring water. 12 single-rooted mandibular premolar teeth with apical matureness and a curvature less than 10° were decoronated, leaving roots 14 mm in length. After instrumentation to F3, the root canals were air-dried and injected with 10 µL distilled water each. Then all the root canals were assigned to 4 groups (n=12) according to different methods on root canal drying. Near-field microwave detection system was used to detect the change of water after air-drying and root canal drying so as to evaluate the effects of different root canal drying methods: (1) negative control group, the canals were injected with 10 µL distilled water and no root canal drying method was performed; (2) paper points drying experimental group, four #60 paper points were used to blot-dry the middle and upper part of the canal, followed by #40 paper points blot-drying the apical area. The above step was repeated with the tip of paper point that appeared with no water under microscope as finished; (3) 95% (volume fraction) ethanol drying experimental group, after the distilled water was removed with paper points (similar to paper points experimental group), 10 µL 95% ethanol was injected into the canal and was left in place for 10 s, then paper points were used to dry the canal; (4) 70% (volume fraction) isopropyl alcohol drying experimental group, after the distilled water was removed with paper points (similar to paper points experimental group), 10 µL 70% isopropyl alcohol was injected into the canal and was left in place for 10 s, then paper points were used to dry the canal. The linear correlation analysis was used to test the accuracy of the measuring water by near-field microwave detection method and physical measurement. The Pearson correlation coefficient was calculated based on the data. The effects of different methods on drying root canal were analyzed by Chi square test. RESULTS: The R2 for the microwave reflection coefficient and the physical measurement of the water in Eppendorf tube and root canal were 0.991 and 0.970. The microwave reflection coefficient in all the experimental groups showed significant difference (P<0.05). After drying with paper points, the residual water was the most, and the microwave reflection coefficient was the highest: 0.023. While after 70% isopropyl alcohol drying root canal, the residual water was the least with the microwave reflection coefficient 0.006, showing that the effect of drying was the best. CONCLUSION: Near-field microwave detection system could detect the change of water in root canal. The effect of root canal drying by 70% isopropyl alcohol was superior to 95% ethanol and paper points.

[A discussion on three-dimensional digital imaging technology: application of cone-beam CT in endodontics].

Cone-beam CT (CBCT) is a relatively novel digital imaging technology to provide undistorted, three-dimensional information of teeth and surrounding tissues for aiding the diagnosis procedure and improving clinical decision-making. The use of CBCT in endodontics is widely and rapidly increasing. The aim of this review article is to introduce not only the current endodontic applications but also the limitations of CBCT such as artefacts and concerns on radiation dose. Furthermore, the evidenced-based guidelines on the reasonable application of CBCT in endodontics is also presented and re-considered. Clinicians should be more conscious neither to take CBCT as a substitute for two-dimensional radiography nor as a routine examination. With the continuous improvement of equipment and technology, it is urgent to establish and update guidelines in clinical practice. Endodontists should strengthen training, update knowledge, familiarize with CBCT technology and cooperate with radiologists to fulfill their diagnostic responsibilities.

[Construction of swept source optical coherence tomography imaging system for root canal endoscopy and application in diagnosis of root fractures].

OBJECTIVE: To construct swept source optical coherence tomography (SS-OCT) imaging system for root canal endoscopy, and to evaluate the accuracy of diagnosing artificial root fractures. METHODS: An ultra-high-speed (40 kHz) swept laser source was developed based on the piezoelectric tuning filter and the Fourier domain mode locking (FDML) swept laser technology (patent number: 200620135940.2). Ultra-miniature gradient index lens technology (patent number: 201320241218.7) was used to create a thin endoscopic probe with a diameter of 0.86 mm for real-time image transmission. The SS-OCT light source had a wavelength of 1 310 nm and a bandwidth of 100 nm. The axial and transverse image resolutions were 15 µm and 25 µm, respectively. Artificial fractures were created on human mandibular premolars with single root and the premolar roots were prepared to 41 horizontal sections (1 mm thick). 27 root sections with fractures (width: 52-284 µm) and 14 the sections without fractures were observed under an optical stereomicroscope with a cold light source as the gold standard. The horizontal root sections were scanned by self-developed SS-OCT imaging system for root canal endoscopy with a central wavelength of 1 310 nm and bandwidth of 100 nm. The data were reconstructed with 30 µm thick slices at an interval of 30 µm. Two observers, a radiologist and an endodontist, were trained and independently evaluated all the reconstructed images blindly. The diagnostic performance of SS-OCT imaging system was calculated, and statistical analysis was performed. RESULTS: SS-OCT root canal endoscopic imaging system composed of high-speed swept laser source, fiber coupler, endoscopic probe, reference arm and differential detector. Root sections could be scanned by SS-OCT and imaged in realtime at a depth of 1 to 2 mm. The kappa value for interobserver agreement was 0.792, and the intraobserver agreement was 1.000 and 0.709 for two observers respectively. All of 27 fractured root sections and 12 of 14 root sections without fractures were accurately diagnosed while 2 unfractured root sections were misdiagnosed. The sensitivity was 1.000 and the specificity was 0.857 for diagnosis of artificial root fractures by SS-OCT. The positive predictive value (PPV), negative predictive value (NPV) and the overall accuracy rate were 0.931, 1.000 and 0.951 respectively. CONCLUSION: The swept source optical coherence tomography imaging system for root canal endoscopy is a promising imaging method for observing root fractures．.

The recovery effect of proanthocyanidin on microtensile bond strength to sodium hypochlorite-treated dentine.

AIM: To evaluate the recovery effect of proanthocyanidin (PA) on microtensile bond strength (µTBS) to sodium hypochlorite (NaOCl)-treated dentine. METHODOLOGY: Fifty-five freshly extracted third molars with intact dental crowns, no caries or restorations were sectioned to expose a sound middle layer of dentine and were randomly divided into 11 groups. In the blank control group, dentine surfaces were immersed in deionized water for 20 min. In the negative control group, dental surfaces were immersed in 5.25% NaOCl for 20 min. In the other nine experimental groups, after immersion for 20 min in 5.25% NaOCl, followed by PA (5%, 10%, or 15%) treatment for 1, 5 min or 10 min. The NaOCl solution was renewed every 5 min. Then dentine surfaces were bonded using SE bond. Bonded samples were sectioned into dentine-resin sticks (n = 45) for microtensile bond strength testing (MPa). Failure modes were observed and classified into three types with a stereomicroscope. Microtensile bond strength data were analysed using one-way anova. The confidence interval test was performed to analyse the recovery effect of PA on bond strength to NaOCl-treated dentine. The chi-squared test was used to analyse failure mode distribution. RESULTS: After use of 5.25% NaOCl for 20 min, microtensile bond strength in the negative control group decreased significantly compared with that of the untreated group (P < 0.05). After a recovery treatment of 10% PA for 10 min or 15% PA for more than 5 min, the bond strength was restored to at least 90% of baseline (P < 0.05). No recovery effect on bond strength was detected after the application of 5% PA for 1 min (P > 0.05). Adhesive fracture was found to be the most common failure mode in the NaOCl-treated group. After the recovery application of PA, the proportion of mixed failures increased significantly (P < 0.05). CONCLUSIONS: Microtensile bond strength to NaOCl-treated dentine recovered after the application of either 5% PA for more than 5 min or 10% or 15% PA for more than 1 min. The application of PA before an adhesive procedure may immediately restore the compromised bond strength of NaOCl-treated dentine.

[Effect of long-term deep slow-wave sleep deprivation on the reproductive system in male rats].

Objective: To investigate the effect of long-term deep slow-wave sleep deprivation on the gonad axis, sperm abnormality rate, and structure of the testis in male rats and possible mechanisms. Methods: A total of 30 specific pathogen-free male Wistar rats aged 5 weeks were randomly divided into slow-wave sleep deprivation group 1 (SD1 group) , slow-wave sleep and sleep time deprivation group 2 (SD2 group) , and control group, with 10 rats in each group. The flower pot method was used to establish a model of sleep deprivation. In addition to 12-hour sleep deprivation at night, the rats in the SD1 group were given interference once every 24 minutes, and those in the SD2 group were deprived of sleep for 8 minutes every 24 minutes; the rats in the control group were given 12-hour light illumination and then placed in dark environment for 12 hours. All rats were sacrificed by exsanguination from the femoral artery, and the testis, the epididymis, and blood were collected for analysis. Sperm abnormality rate and sperm motility rate were measured, and cauda epididymal sperm counting was performed. ELISA was used to measure the serum levels of testosterone (T) , follicle-stimulating hormone (FSH) , and luteinizing hormone (LH) . Results: Compared with the control group, the SD2 group had a significant increase in organ coefficient of the epididymis (P<0.05) and a significant reduction in sperm motility rate (P<0.05) . There were significant differences between the SD1 group and the SD2 group in the increase in sperm abnormality rate (P<0.05) and the reduction in cauda epididymal sperm count (P<0.05) . The levels of FSH and T tended to increase, and the level of LH tended to decrease. Pathological examination showed degeneration and vacuolization of a small amount of spermatogenic cells in the SD1 group; in the SD2 group, there were significant degeneration, edema, and vacuolization of most spermatogenic cells, some spermatogenic cells were observed in the lumen, and there were no sperms in the lumen. Conclusion: Long-term deep slow-wave sleep deprivation impairs the structure of the testis, affects sperm motility rate and sex hormones, and increases the risk of sperm abnormality.

[Computer aided design and three-dimensional printing for apicoectomy guide template].

OBJECTIVE: To establish an apicoectomy guide template design and manufacturing method, based on multi-source data fusion, computer aided design (CAD) and fused deposition modeling (FDM). The feasibility of the guide template was preliminary evaluated by the in vitro model experiment. METHODS: An extracted upper anterior tooth, after root canal treatment, was optical scanned, after which the extracted upper anterior tooth was poured in an apicoectomy plaster model. Cone-beam computed tomography (CBCT) scanning of the apicoectomy plaster model was performed, after which optical scanning of the plaster model for apical resection surgery was carried out. All of the relevant CBCT and optical scanning data of the extracted upper anterior tooth and the apicoectomy plaster model were introduced into the Geomagic Studio 2012 software. The multi-source data fusion technology was used to virtually simulate the three-dimensional positional relationship of the extracted tooth, the dentition, the alveolar bone and the gingival, based on which, the three-dimensional design of the apicoectomy guide template was completed in the Geomagic Studio 2012 software. With the technology of fused deposition modeling, the apical resection surgical guide template was three-dimensionally printed with the material of polylactic acid (PLA). Under the guidance of the surgical guide template, the root apical resection was performed on the plaster model. After the apicoectomy, the extracted upper anterior tooth was taken off from the apicoectomy plaster model and then was given the optical scanning. The apical resection length and angle were calculated by the function of distance measurement and angle measurement, and the results were compared with the preset values. RESULTS: The length of the apical resection was 2.88 mm along the direction of the long axis of the tooth, which was 0.12 mm lower than the preset 3 mm. The included angle between the apical resection plane and the long axis of the tooth was 77.9°, 12.1° lower than the preset 90°. CONCLUSION: This study successfully established a digital design and production method of apicoectomy guide template by combing the multi-source data fusion, CAD and FDM technology. The design route and the production method are feasible. The study will provide a technology and methodology reference for the development of domestic special software for the digital design of apicoectomy guide template.

[Detection of root cracks after root canal preparation using rotary NiTi systems by optical coherence tomography (OCT) scan].

OBJECTIVE: To evaluate the accuracy of optical coherence tomography (OCT) in detecting root cracks after root canal instrumentation using histological gold standard. METHODS: Twenty complete extracted human mandibular incisors that were free of caries, calculus, and root treatment were chosen and accessed coronally with a diamond bur, then mounted in resin blocks with alginate impression material using simulated periodontal ligaments, and the apex was exposed 3 mm. The teeth were stored in water at room temperature. Then the teeth were then instrumented to the major apical foramen (AF) at #30/0.09 using ProTaper Universal rotary nickel titanium system (Dentsply Maillefer, Ballaigues, Switzerland), irrigation with 1% sodium hypochlorite (NaOCl) by using a 26-gauge needle followed after each instrument. The apical root was scanned with 360° of rotation by Swept-Source Optical Coherence Tomography (SS-OCT) (wavelength: 1 310 nm, scan rate: 20 kHz, axial resolution: 16 µm) with driving device (stepper motor and lifting platform). The reconstruction images of axial planes 1, 2 and 3 mm from the apex were examined and the root cracks were blindly diagnosed by two observers. The horizontal section was performed at 1, 2 and 3 mm from the apex using low speed disc saw (Leica SP1600, Wetzlar, Germany). The presence of cracks was noted under an optical stereomicroscope (ZOOM-630E) with a cold light source using as gold standard to evaluate the accuracy of OCT in detecting root cracks after root canal instrumentation. RESULTS: After canals instrumentation with ProTaper Universal rotary nickel titanium system to #30/0.09, root cracks were detected in 9 of 20 teeth by histological examination. Crack lines were observed on 13 of 60 horizontal sections and cracks on 12 of the 13 sections were detected by OCT. No cracks were observed in the other 47 of the 60 horizontal sections,none of which was misdiagnosed by OCT. The overall accuracy rate for detection of root cracks with OCT was 0.983, the sensitivity was 0.923, the specificity was 1.000, the positive predictive value (PPV) was 1.000 and the negative predictive value (NPV) was 0.979. CONCLUSION: OCT may be a promising nondestructive imaging method for diagnosing root canal cracks after canal instrumentation.

[Cleaning efficacy of different solvents on sealer-contaminated dentin surface].

OBJECTIVE: To evaluate the influence of an epoxy resin-based sealer on the bond strength of adhesive resins to dentin and the cleaning efficacy of different solvents in removing sealer residues. METHODS: The occlusal enamel of 25 freshly extracted human third molars without caries were removed to expose flat surfaces of dentin. The teeth were randomly divided into five groups according to the treatment received: For negative control group, the dentin surfaces were not contaminated with AH-Plus; For the other 4 experimental groups, the samples were contaminated with AH-Plus for 5 min and different measures were taken: For positive control group, the sealer were wiped with dry cotton pellets; For solvents experimental groups: cotton pellets saturated with 95% (volume fraction) ethanol, 99.5% (volume fraction) acetone or 99% (volume fraction) amyl acetate were used to wipe the sealer until the surface appeared clean when viewed through a stereomicroscope under ×10 magnification, then rinsed with de-ionized water for 3 s. After sealer removal, a self-etching adhesive system was applied on the surfaces with resin composite. The samples were sectioned into 1.0 mm×1.0 mm stick specimens (n=45) for microtensile test. Failure modes at the dentin-resin interface were observed using a stereomicroscope. The samples were sectioned into 1.0 mm piece specimens (n=4) for scanning electron microscope observation. The microtensile bond strength data were analyzed by one-way ANOVA. Chi-square test were used to analyse the failure modes between the groups. RESULTS: There was significant difference among the five groups (P<0.001). For dry cotton pellet group (38.69±8.60) MPa and the ethanol group (37.14±12.01) MPa, the microtensile bond strength significantly declined when compared with negative control group (43.86±7.99) MPa (P<0.05). No significant difference of bond strength was found between the dry cotton pellet group and the ethanol group (P=0.426). There was no statistical significant difference among acetone group, amyl acetate group and negative control group (P>0.05). The bond strength of acetone group and amyl acetate group were (45.94±10.37) MPa and (43.99±7.01) MPa, respectively. The ethanol group exhibited lower bond strength than that of acetone group and amyl acetate group (P<0.05). Scanning electronic microscope observation revealed that in dry cotton pellet group and ethanol group, the resin tags were short and loose. Moreover, sealer residues were identified in the interface in the ethanol group samples, while the resin tags in the acetone and amyl acetate group were as dense and uniform as in negative control group. The distribution of failure modes showed no significant difference in the five groups (P=0.086). CONCLUSION: The microtensile bond strength of dentin to composite resin was lower after exposure to sealer. Compared with ethanol and dry cotton pellets, the cleaning effect of acetone and amyl acetate on sealer-contaminated dentin surface were better.