Research progress on invasive cervical resorption / 口腔疾病防治

@#Tooth absorption can be divided into physiological absorption and pathological absorption. Root absorption of mature deciduous teeth is physiological absorption. Pathological absorption includes internal absorption and external absorption. Internal absorption, also known as intramedullary absorption, includes inflammatory absorption and alternative absorption. External tooth absorption originates from the outer surface of the root or the neck of the tooth and can be divided into inflammatory absorption, alternative absorption, pressure resorption and invasive cervical resorption. Invasive cervical resorption (ICR) is pathological damage caused by many factors, which usually begins in the cemento-enamel junction and extends peripherally or horizontally in the dentin. It hardly invades the pulp. Orthodontic devices, trauma, bleaching, systemic diseases, and the use of certain medications can all lead to invasive cervical resorption. The clinical manifestations of ICR are usually asymptomatic or not obvious, and most of which are found in imaging examinations. Because caries and internal absorption are often misdiagnosed through plain apical radiography, cone beam computed tomography (CBCT) can help to better understand the situation of invasive cervical resorption. Because the pathogenesis and etiology of invasive cervical resorption are not fully understood, clinical negligence and inadequate treatment of invasive cervical resorption can even cause unnecessary tooth loss. This article reviews the latest research progress on the histopathologic features, pathogenic mechanism, susceptibility factors, diagnosis and treatment of ICR, with special emphasis on susceptibility factors and their mechanisms.

Measurement of the relationship between maxillary premolar roots and the maxillary sinus floor using cone beam CT and analysis of the impact on immediate implantation / 口腔疾病防治

Objective@#To analyze the spatial relationship between the roots of maxillary anterior premolars and the maxillary sinus, thus providing an anatomical basis for timing, planning, surgical approaches, and implant selection at this site.@*Methods@#Cone beam CT (CBCT) images were collected from 264 patients (aged 20-65 years) who visited the Ruihua Dental Clinic between January 2017 and March 2023. The minimum distance from the apex of the maxillary anterior premolar roots to the lower wall of the maxillary sinus was measured on the coronal plane. The classification of the vertical relationship between the tooth root and the lower wall of the maxillary sinus was performed, and comparisons were made bilaterally, between genders, and among different age groups.@*Results@#The minimum distance (Q50) from the apex of the first maxillary premolar root to the lower wall of the maxillary sinus was 7.34 mm for the single-root type, 7.80 mm for the buccal root of the double-root type, and 7.36 mm for the palatal root. For the second maxillary premolar, the median distance was 2.56 mm for the single root type, 1.73 mm for the buccal root type, and 1.23 mm for the palatal root type. There was a significant difference in the shortest distance from the apex of the right second maxillary premolar single root to the lower wall of the maxillary sinus among the different age groups (P<0.05), with the 20-29-year-old group having the smallest median distance (1.52 mm) and the ≥ 40-year-old group having the largest (4.44 mm). There was no significant difference in the effect of sex or laterality on distance (P>0.05). The most common vertical relationship between the apex of the maxillary anterior premolar roots and the lower wall of the maxillary sinus was noncontact. There was no significant difference in the vertical relationship classification between the single-root and double-root types (P>0.05).@*Conclusion@#Most maxillary first premolar roots can provide sufficient bone height, which makes it easy to achieve immediate implantation. The maxillary second premolar root frequently involves insufficient bone, which is necessary to make full use of the bone wall of the extraction socket or the sinus floor cortical bone to achieve initial stability. The vertical relationship between the premolar root and maxillary sinus was influenced by age and dental position. Younger age groups often exhibit inadequate bone height, and the indication for immediate implantation should be carefully considered. The number of roots does not significantly affect the relationship between the sinus and root; however, double-rooted premolars offer more support for immediate implantation and socket healing due to the small root diameter and bony separation between the roots.

Cone-beam CT evaluation of bone mass in the external oblique line of the mandible in adolescents with different cervical vertebral bone ages / 中国组织工程研究

BACKGROUND:The application of miniscrew in adolescents is increasing day by day,but at present,there are few studies on bone mass in the external oblique line of the mandible in adolescents at home and abroad,and there is no systematic study on bone mass in the external oblique line of the mandible in adolescents in different growth and development periods. OBJECTIVE:To measure the bone mass in the external oblique line of the mandible in adolescents with different cervical vertebral bone ages using a cone-beam CT and to investigate the difference of bone mass in the external oblique line of the mandible in adolescents with different cervical vertebral bone ages and the correlation between bone mass in this area and the cervical vertebral bone age. METHODS:The cone-beam CT data of 105 adolescent patients before orthodontic treatment were collected and divided into CS3 group(n=24),CS4 group(n=26),CS5 group(n=29)and CS6 group(n=26)using the cervical vertebral maturation method.The adolescent mandibular buccal shelf was reconstructed by Mimics Medical 21.0 software.The width of buccal bone at 6 and 11 mm under the cemento-enamel junction and the bone height at 4 and 5 mm buccal to the cemento-enamel junction of right mandibular first and second molars were measured.The measured data were statistically analyzed.The measurement was made on four planes:plane 1 is the plane where the proximal mesial root of the mandibular right first molar is located;plane 2 is the plane where the distal mesial root of the mandibular right first molar is located;plane 3 is the plane where the proximal mesial root of the mandibular right second molar is located;and plane 4 is the plane where the distal mesial root of the mandibular right second molar is located. RESULTS AND CONCLUSION:In each group,the bone width on the buccal side of the external oblique line increased gradually from the first molar proximally to the second molar distally in adolescents,and the width of buccal bone at 6 and 11 mm under the cemento-enamel junction showed significant difference among different layers(P<0.05).The bone width of buccal bone at 11 mm under the cemento-enamel junction was greater than that at 6 mm.The bone height on the buccal side of the external oblique line increased gradually from the first molar proximally to the second molar distally in all four groups,and the bone height at 4 and 5 mm buccal to the cemento-enamel junction showed significant differences at different layers(P<0.05).The bone height at 4 mm buccal to the cemento-enamel junction was greater than that at 5 mm.On the fourth plane,the bone width at 11 mm buccal to the cemento-enamel junction was smaller in the CS3,CS4,and CS5 groups than in the CS6 group(P<0.05).On the third plane,the bone heights at 4 mm and 5 mm buccal to the cemento-enamel junction were smaller in the CS3 and CS4 groups than in the CS6 group(P<0.05).On the fourth plane,the bone height at 5 mm buccal to the cemento-enamel junction was smaller in the CS3 and CS4 groups than in the CS6 group(P<0.05).On the fourth plane,the bone height at 4 mm buccal to the cemento-enamel junction was smaller in the CS3 group than in the CS6 group(P<0.05).Spearman correlation analysis showed that there was no correlation between bone mass and the cervical vertebral bone age,except that there was a weak correlation between bone mass at some measurement sites and cervical vertebral bone age.To conclude,the bone mass in the external oblique area of the mandible in adolescents does not change significantly with the increase of cervical vertebral bone age.The buccal side of the mesial root and distal root of the mandibular second molar in the external oblique area of CS3-CS6 adolescents meets the requirement of bone mass for miniscrew implantation,which is a site available for miniscrew implantation.

Consistency between two types of cone-beam CT transformed two-dimensional images and traditional lateral cephalometric radiographs for quantitative analysis of cervical vertebral bone age / 中国组织工程研究

BACKGROUND:Traditional lateral cephalometric radiographs always suffer from some problems,such as magnification distortion,left and right overlap inconsistency and so on,while the cone-beam CT can truly display the three-dimensional structure of the craniofacial region.Performing three-dimensional reconstruction of cone-beam CT and then transforming the cone-beam CT in the selected area into the two-dimensional image can make the overlap between the left and right sides consistent and reduce the influence of surrounding tissue structures. OBJECTIVE:To explore the consistency of quantitative analysis of cervical vertebral bone age between two kinds of cone-beam CT transformed two-dimensional images with different integrated thicknesses and traditional lateral cephalometric radiographs. METHODS:The cone-beam CT and lateral cephalometric radiograph data of 118 adolescent orthodontic patients were collected.Firstly,the cone-beam CT image was reconstructed in 3D imaging software.After reconstruction,two types of cone-beam CT images with different integrated thicknesses were selected in the sagittal interface and transformed into two-dimensional images,which were named ICB-1 and ICB-2,respectively.The Zhibeiyun system was used to measure and calculate the angle between the concave base of the second cervical vertebra and the lower edge of the vertebral body(@2),the ratio of the third cervical spine to the posterior height(AH3/PH3),the ratio of height to width of the fourth cervical spine(H4/W4)in lateral cephalometric radiograph,ICB-1,ICB-2 and the cervical vertebral bone age.After an interval of two weeks,20 adolescents were randomly selected to repeat the above measurements.The intraclass correlation coefficient(ICC)method was used to evaluate the repeatability of the three images in measuring cervical bone age.Paired t-test was used to analyze the consistency of cervical bone age measurements between the three images.The Kappa test was used to analyze the consistency of cervical vertebral bone age staging assessment between the three images. RESULTS AND CONCLUSION:(1)ICC of AH3/PH3 in the lateral cephalometric radiograph group was<0.9,and the ICC of other measurement items in each group was>0.9.(2)Paired t-test results showed that there were statistical differences in AH3/PH3 and H4/W4 between the ICB-1 group and lateral cephalometric radiograph group and between the ICB-1 group and ICB-2 group(P<0.05),and there were no statistically significant differences in the other items between the three groups(P>0.05).(3)The Kappa test results showed that the Kappa coefficients of the two groups were all more than 0.8 according to the staging of cervical vertebral bone age in three groups(P<0.001).(4)It is indicated that the repeatability of ICB-1 and ICB-2 in the measurement of cervical vertebral bone age is better than that of lateral cephalometric radiographs.Lateral cephalometric radiographs,ICB-1 and ICB-2 have good consistency in the measurement of cervical vertebral bone age,but considering the integrity of cervical vertebra structure,ICB-2 is more suitable for quantitative analysis of cervical vertebral bone age than ICB-1.

Epidermoid cyst in the right mandible: a case report and literature review / 口腔疾病防治

Objective@#To discuss the possible etiology, pathogenesis, clinical features, diagnosis and treatment of epidermoid cysts of the jaw and to provide a reference for clinical diagnosis and treatment.@*Methods@#A case of an epidermoid cyst in the right mandible with retained deciduous teeth and succedaneous impacted teeth was reviewed and analyzed in combination with the relevant literature.@*Results@#A patient presented with a mass in the right mandible that had persisted for 1 month after being found at imaging examination. Tooth 83 was retained, and tooth 43 was unerupted. Swelling was characterized by no obvious tenderness, fluctuation, or table tennis sensation and was observed in the lingual alveoli of teeth 83, 44, and 45. Imaging revealed a low-density shadow in the apex of teeth 83, 44, 45, and 46, approximately 1.9 cm × 2.6 cm × 1.6 cm in size, which wrapped around the dental crown of tooth 43. Preliminary diagnoses were as follows: right mandibular mass thought to be a dentigerous cyst; impacted tooth 43; and retained primary tooth 83. The mass in the right mandible was removed, and teeth 43 and 83 were extracted under intravenous and inhalation anesthesia. During the operation, the mass was observed to have a thin cyst wall and contained bean-like residue. Histopathological examination indicated an epidermoid cyst in the right mandible. At the 1-week follow-up examination, the patient reported no discomfort, and the surgical area showed good recovery. According to the literature, epidermoid cysts are benign cysts originating from ectopic ectodermal tissue that can occur throughout the body but rarely in the oral cavity and are even extremely rarer in the jaw. Epidermoid cysts of the jaw, which have no specific clinical manifestations, can be confused with odontogenic cysts such as dentigerous cysts and odontogenic tumors. Dental pulp tests and other techniques can serve as a reference for clinicians. The diagnosis is confirmed via histopathology. Surgical removal is a common treatment, with a good prognosis and a low recurrence rate.@*Conclusion@#The principle of treatment for an epidermoid cyst of the jaw is similar to that for a jaw cyst. The prognosis is good when the cyst is removed completely.

Clinical analysis of orthodontic traction of impacted upper incisors / 口腔疾病防治

Objective@#To study the effect of orthodontic traction on the roots and periodontal soft and hard tissues of buried obstructed upper incisors.@*Methods@#This study was reviewed and approved by the ethics committee, and informed consent was obtained from the patients. From January 2018 to December 2022, 40 patients who underwent orthodontic traction on impacted upper incisors were selected; those whose contralateral homonymous apical foramen was not developed were placed in group A (23 cases), and those whose contralateral homonymous apical foramen was developed were placed in group B (17 cases). Software was used to measure the root length of the impacted upper incisors in groups A and B on cone beam CT (CBCT) images before and after traction and compare the changes in alveolar bone (alveolar bone width, labral bone plate thickness, and horizontal height of alveolar bone) and keratinized gingival width between each impacted upper incisor and the corresponding contralateral tooth immediately and one year after traction@*Results@#The root length of the impacted upper incisors increased after traction compared to before traction (P<0.05). The width of the alveolar bone at the completion of traction in group A was similar to that of the contralateral homonymous tooth (P>0.05), whereas the width of the alveolar bone at the completion of traction in group B did not reach that of the contralateral homonymous tooth, with a significant difference in width (P<0.05). Neither the labial bone plate height or width in group A or B reached that of the contralateral homonymous tooth after traction (P<0.05). The keratinized gingival width on the affected side was also significantly smaller than that on the contralateral side (P<0.05), but it was increased significantly in group A at the one-year follow-up visit (P<0.05).@*Conclusion@#Tooth traction is conducive to impacted upper incisor root growth, alveolar bone reconstruction and keratinized gingival growth but cannot produce complete symmetry with respect to the contralateral side.

Prevalencia del segundo conducto en dientes anteroinferiores usando Tomografía Computadorizada Cone Beam / Second root canal prevalence in lower anterior teeth using Cone Beam Computed Tomography

Introducción: Es un error común pensar que los dientes anteroinferiores, por lo general, tienen un solo conducto radicular con una sola raíz. Sin embargo, un estudio realizado por Vertucci et. al., (1974), mostraron una alta prevalencia (13%) de dos conductos radiculares en los dientes anteroinferiores, lo que estimuló más investigaciones. Objetivo: El propósito de este estudio fue determinar la prevalencia del segundo conducto radicular en los dientes anteroinferiores en una población nicaragüense, estos fueron detectados por medio de tomografía computadorizada (Cone Beam). Materiales y Métodos: En el estudio se analizaron 293 piezas dentales, de canino a canino de la arcada inferior. Para realizar el análisis se utilizó el software libre Radiant DICOM Viewer 2021.2.2, se realizaron cortes sagitales, axiales y coronales para ver la prevalencia del segundo conducto radicular. Resultados: De las 293 piezas dentarias analizadas se encontró que 259 presentaban un solo conducto que correspondía al 88.4% y 34 dientes presentaban dos conductos que correspondían al 11.6%. De acuerdo con el análisis tomográfico, se encontró que en los cortes axiales y sagitales fue donde se observó la presencia del segundo conducto. Con respecto a la presencia del segundo conducto de acuerdo al tercio del canal radicular se identificó que la mayoría se presentó en el tercio medio (52.94%), seguido por coronal (29.41%) y por último el tercio apical (17.65%). De acuerdo con la clasificación de Vertucci se encontró que se presenta un mayor porcentaje del tipo I con 88.40%, seguido por el tipo III con 4.44%, después el tipo V con 3.41%, y el tipo II con 2.39%. El de menor porcentaje fue el tipo VI con 1.37%, mientras que, en las piezas analizadas, no se encontraron los tipos IV, VII y VIII. Conclusión: Basados en los resultados obtenidos en este estudio, la prevalencia de un segundo conducto en dientes anteroinferiores fue de 11.6%.

Title The prevalence of a second root canal in mandibular anterior teeth using Cone Beam Computed Tomography. Abstract Introduction: It is a common misconception that the mandibular anterior teeth usually have a single root canal with a single root. However, a study by Vertucci et. al., (1974), showed a high prevalence (13%) of two root canals in the lower anterior teeth, which stimulated further investigations. Objective: The purpose of this study was to determine the prevalence of the second root canal in the mandibular anterior teeth in a Nicaraguan population, these were detected by means of computed tomography (Cone Beam). Materials and methods: In the study, 293 teeth were analyzed, from canine to canine of the mandibular teeth. To perform the analysis, the free software Radiant DICOM Viewer 2021.2.2 was used, sagittal, axial and coronal views were made to see the prevalence of the second root canal. Results: Of the 293 teeth analyzed, it was found that 259 had a single root canal corresponding to 88.4%, and 34 teeth had two root canals corresponding to 11.6%. According to the tomographic analysis, it was found that the presence of the second root canal was observed only in the axial and sagittal views. Regarding the presence of the second canal according to the third of the root canal, it was identified that the majority presented in the middle third (52.94%), followed by coronal (29.41%) and finally the apical third (17.65%). According to the Vertucci classification, it was found that there is a higher percentage of type I with 88.40%, followed by type III with 4.44%, then type V with 3.41%, and type II with 2.39%. The one with the lowest percentage was type VI with 1.37%, while in the pieces analyzed, types IV, VII and VIII were not found. Conclusion: Based on the results obtained in this study, the prevalence of a second root canal in lower anterior teeth was 11.6%.

Conventional quality control and evaluation of Leksell Icon Gamma Knife cone-beam CT / 中华放射医学与防护杂志

Objective:To analyze the conventional quality control result of Leksell Icon Gamma Knife cone-beam CT and evaluate long-term stability of cone-bem CT.Methods:QA TOOL Plus was used to verify the accuracy of cone-beam CT. The phantom Catphan 503 was scanned, and the image spatial resolution, contrast to noise ratio and homogeneity were analyzed.Results:The maximum deviation in image volume of cone-beam CT was 0.09-0.17 mm, which passed the accuracy test. At the scanning patterns with CT dose index of 2.5 and 6.3 mGy, the spatial resolution was very stable at 7 and 8 lp/cm respectively. The contrast noise ratio and uniformity meet the reference requirements.Conclusions:The conventional quality control results of Leksell Icon Gamma Knife cone-beam CT are stable in 12 months. In addition to referring to the manufacturer′s baseline value, the unified analysis and evaluation standard for Gamma Knife need to be further improved for the quality control of cone-beam CT.

Research on con-beam CT images segmentation method / 中华放射医学与防护杂志

Image-guided radiation therapy (IGRT) is a visual image-guided radiotherapy technique that has many advantages such as increasing the dose of tumor target area and reducing the dose of normal organ exposure. Cone beam CT (CBCT) is one of the most commonly used medical images in IGRT, and the rapid and accurate targeting of CBCT and the segmentation of dangerous organs are of great significance for radiotherapy. The current research method mainly includes partitioning method based on registration and segmentation method based on deep learning. This study reviews the CBCT image segmentation method, existing problems and development directions.

Research progress in the average glandular dose during mammography / 中华放射医学与防护杂志

Mammography has played an essential role in the screening and treatment of breast cancer. However, the application of X-rays will also increase the risks of breast cancer while improving its detection rate. Moreover, the risks will increase with an increase in the radiation dose. Since the glandular tissue in breasts is sensitive to radiation, the evaluation of the average glandular dose (AGD) in mammography has attracted considerable international attention. Compared to relatively mature dosimetric studies on traditional two-dimension mammography and digital breast tomosynthesis, the method for the dose evaluation of the new cone beam CT for breasts are still subjected to research. This paper reviews and explores the current status of studies on the assessment method and relevant influencing factors of AGD under different types of mammography equipment.

Dose reconstruction of volumetric modulated arc therapy for nasopharyngeal carcinoma based on log files and CBCT / 中华放射肿瘤学杂志

Objective:To reconstruct the dose of nasopharyngeal carcinoma and verify the results of the whole-process radiotherapy plan based on log files and cone beam CT (CBCT).Methods:A total of 15 patients with nasopharyngeal carcinoma who received volumetric modulated arc therapy (VMAT) with Halcyon accelerator in the Cancer Center of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology from February to September 2022 were retrospectively selected. Log files and CBCT for all fractionated radiotherapy were recorded. The errors of monitor unit (MU), gantry angle, and multi-leaf collimator (MLC) leaf position per control point were analyzed. The adaptive CT (aCT) were generated according to CBCT and planned CT (pCT) using a commercial software Velocity TM, and the similarities among aCT, pCT and CBCT were analyzed. The original plan was modified from the log files and imported into the treatment planning system to calculate the delivered dose on the corresponding fractionated aCT to reconstruct the fractionated dose. And all the reconstructed doses were mapped back to pCT to obtain the cumulative dose. Theγpass ratios with criteria of 2 mm/2% and 2 mm/3% and the dose differences between the planned dose and the cumulative dose in the planning target volume (PTV) and organs at risk (OAR) were compared. Results:The root mean square (RMS) and the 95th percentile of the errors of MU, gantry angle and MLC leaf position errors were within an acceptable range. The aCT generated by Velocity TM had the anatomical structure of CBCT and the resolution, contrast, noise characteristics of pCT, which could be directly used for dose calculation. Compared with the planned dose, the changes of V 70 Gy of nasopharyngeal primary tumor (PTV nx), V 68 Gy of cervical glands (PTV nd) and V 60 Gy of planning target volume (PTV1) were -0.88%±1.91%, -2.99%±2.99% and -0.63%±0.93%, respectively, and V 40 Gy of parotid gland was increased to 2.65%±2.63%. Cumulative dose showed different degrees of PTV dose decrease ( P<0.05) and parotid dose was increased ( P<0.05). The γ pass ratio (2 mm/3%) between the cumulative dose and planned dose was 97.3%±2.7% and >95.0% in 86.7% of patients. Conclusions:Based on the log files and CBCT, the whole-process dose reconstruction of nasopharyngeal carcinoma patients can be carried out. According to the results of dose reconstruction, the radiotherapy effect of the target area and OAR can be quantitatively evaluated. In the case of high dose coverage and conformity of the original plan, the reconstruction results show that the cumulative dose coverage of the target area is decreased, whereas that of the parotid gland is increased.

Effects of changes in bladder volumes derived from CT simulation on set-up errors during radiotherapy for prostate cancer / 中华放射医学与防护杂志

Objective:To explore the effects of bladder volumes from CT simulation on bladder volume consistency and set-up errors during radiotherapy for prostate cancer, aiming to provide a reference for clinical practice.Methods:A retrospective analysis was conducted for of 66 prostate cancer patients treated with intensity-modulated radiation therapy in the Sun Yat-sen University Cancer Center from August 2015 to November 2020. They underwent CT scan or radiotherapy after voluntarily holding in urine. Cone beam computed tomography (CBCT) scans were performed for them to measure their set-up errors in left-right (L-R), superior-inferior (S-I), and anterior-posterior (A-P) directions before each treatment. The bladder contours of the patients were delineated on CT simulation images and CBCT images. Accordingly, bladder volumes were calculated. Based on the calculated bladder volumes derived from the CT simulation images, the patients were divided into three groups: 18 cases in the 200-300 ml group, 24 cases in the 300-400 ml group, and 24 cases in the >400 ml group. Finally, this study analyzed the effects of bladder volumes derived from CT simulation on set-up errors and the changes of CBCT-derived bladder volumes relative to planned volumes during radiotherapy.Results:The bladder volumes in the 200-300 ml, 300-400 ml, and >400 ml groups during radiotherapy were reduced by 15%, 26%, and 32%, respectively. The pairwise comparison indicates statistically significant differences in the changes of bladder volumes among the three groups ( Z=3.43, 7.97, 4.83, P<0.05). Regarding the three-dimensional set-up errors, there were statistically significant differences in S-I set-up errors among the three groups ( H=26.72, P<0.05), but there was no statistically significant difference in L-R and A-P set-up errors ( P>0.05) among these groups. The 200-300 ml, 300-400 ml, and >400 ml groups exhibited S-I set-up errors of 0.00 (-0.20, 0.20) cm, 0.00 (-0.20, 0.30) cm, and -0.10 (-0.30, 0.20) cm, respectively. Therefore, the >400 ml group displayed larger the S-I set-up errors than other two groups, with statistically significant differences ( Z=4.17, 4.66, P< 0.05), while there was no statistically significant differences in S-I set-up errors between other two groups ( P> 0.05). Conclusions:Controlling the bladder filling volumes at 200-300 ml in CT simulation is beneficial for maintaining bladder volume consistency and reducing set-up errors of patients during radiotherapy.

Feasibility analysis of digital method for measuring supracrestal tissue height crest around implant / 华西口腔医学杂志

OBJECTIVES@#This study aimed to investigate the feasibility of measuring the soft tissue height of bone cristae around implant by digital method.@*METHODS@#A total of 36 patients with dental implants were selected from the Dental Medicine Center of the First Affiliated Hospital of University of Science and Technology of China (Anhui Provincial Hospital) from August 2022 to December 2022. A total of 43 dental implants were enrolled. All postoperative cone beam CT (CBCT) imaging data and intraoral digital impressions obtained before surgery were immediately obtained by the patients on the day of completion of oral implant surgery and they were imported into oral implant surgery planning software for image fitting. Then, virtual implants of the same specification were placed in the planting area, and the implant position was adjusted to overlap with the implant shadow in the CBCT image. Supracrestal tissue height (STH) was measured at the implant view interface (digital group). During the operation, implant holes were prepared step by step in accordance with the standard preparation method, and implants were implanted. The upper edge of the implant was flushed with the crest of the alveolar ridge. STH was measured by perio-dontal probing (periodontal probe group). Paired t-test was used to compare the STH differences between the digital and periodontal probe groups. Bland-Altman test was used to analyze the consistency of the two methods. Intra-group correlation coefficient (ICC) was used to verify the reliability of the results measured by different surveyors using di-gital methods.@*RESULTS@#No statistical significance was observed in the STH difference between the two methods (P>0.05). Bland-Altman test showed good consistency between the two methods, but the measurement of mandibular posterior teeth showed that the results of periodontal probe were greater than those of digital method. The ICC and 95%CI of the STH results measured digitally by different surveyors are 0.992 (0.986-0.996).@*CONCLUSIONS@#The digital me-thod is in good agreement with the periodontal probe method in measuring the soft tissue height of the bone cristae around the implant.

Actinomycotic osteomyelitis in the maxilla and the zygomatic bone: a case report and literature review / 口腔疾病防治

Objective@# To investigate the clinical features, diagnosis and treatment of osteomyelitis of the jaw caused by an actinomycotic infection and to provide a reference for clinical diagnosis and treatment.@*Methods@#A case of osteomyelitis in the bilateral maxilla and the left zygomatic bone and arch caused by a mixed bacterial infection dominated by Actinomycetes was reviewed and analyzed in combination with the literature. @*Results @#The patient had left upper posterior tooth pain with repeated left facial swelling for 7 months. The patient's left face was swollen before surgery, the left maxillary alveolar bone was necrotic, and the upper palate showed fistula discharge. A maxillofacial magnetic resonance imaging scan excluded tumors and other space-occupying lesions. According to CBCT images, the initial diagnoses were left infraorbital space infection and osteomyelitis of the bilateral maxillary, the left zygomatic bone, the left zygomatic arch and the lateral orbital wall. Necrosis of the left maxilla and the zygomatic bone was excised, the focus was cleared and the focal tooth was extracted under general anesthesia. Histopathological results confirmed osteomyelitis and actinomycotic infection. Anti-inflammatory therapy with penicillin sodium was given before surgery, and piperacillin sodium and tazobactam sodium, dexamethasone sodium phosphate, tranexamic acid and mecobalamine were given after surgery. The patients' 6-month follow-up results showed that the maxillofacial shape was basically symmetrical; no ulceration, pus or abnormal secretion was found in the skin or intraoral mucosa; and the surgical area showed good recovery. A review of the relevant literature showed that Actinomyces is an opportunistic pathogen, and factors such as trauma and dental infection have been implicated in the pathogenesis of osteomyelitis. In addition to surgery, antibiotics are used to treat the disease and multidisciplinary symptomatic treatment combined with supportive treatment is required to achieve a better prognostic effect. @*Conclusion @# Actinomycotic osteomyelitis occurring in the maxilla and the zygomatic bone is an extremely rare disease that can be diagnosed by clinical manifestations, bacteriological examination and biopsy. Appropriate and effective penicillin drugs should be given at the initial stage of treatment, more sensitive antibiotics should be selected according to the results of the drug sensitivity test, and the lesions should be surgically removed when the patient's condition improves. Active symptomatic and supportive treatment should be performed during the treatment period.

Discussion on the evaluation of radiation protection of “four-in-one” dental X-ray equipment / 中国辐射卫生

Objective To evaluate the radiation protection of “four-in-one” dental X-ray equipment and to investigate the safety interlock of the equipment by measuring the scattered radiation at the position of the patient during operation. Methods A cone-beam CT dental phantom was used to simulate the patient’s head. The intra-oral and extra-oral components of the “four-in-one” X-ray equipment were installed in a 5 m2 room. The scattered radiation at patient position was measured using a γ/X-ray survey meter, and the effects of intra-oral and extra-oral components were compared. Results For a 5 m2 room, when CBCT was exposed under typical conditions, the dose at the patient's position was 10.70 uSv/h when there was an intra-oral component and 10.60 uSv/h when there was no intraoral component. The intra-oral part did not affect the radiation dose at the patient's position. When the intra-oral component was exposed, the dose rate at the patient's position was 4.05-6.85 uSv/h, and the extra-oral part did not affect the scattered dose of the patient examined with intra-oral components. Conclusion The evaluation of radiation protection of new equipment must comprehensively consider radiation safety and equipment operation safety. The results of this study provide suggestions for clinical radiation protection supervision and evaluation of “four-in-one” dental X-ray equipment.

Achieved intrusion amount of the maxillary incisors and the influencing factors in clear aligner extraction cases / 口腔疾病防治

Objective @#To investigate the achieved intrusion amount of the maxillary incisors and the influencing factors in clear aligner cases treated with extraction of premolars. @*Methods @#This study has been reviewed and approved by the Ethics Committee, and informed consent has been obtained from patients. Thirty adult female patients who underwent extraction of the bilateral maxillary first premolars followed by clear aligner therapy were included. CBCT data before and after treatment were obtained, and three-dimensional reconstruction with registration alignment was performed. A spatial coordinate system was established, and the achieved intrusion amount was measured, followed by calculation of the intrusion efficacy. The factors related to the achieved intrusion amount were investigated through multiple linear regression analysis.@*Results @#The overall efficacy of maxillary incisor intrusion was 54%, with the maxillary central incisors (48%) lower than the lateral incisors (59%), which was statistically significant (P<0.001). Regression analysis showed that the designed intrusion amount and the stepwise intrusion design were positively correlated with the achieved intrusion amount. The designed retroclination amount and use of class Ⅱ intermaxillary elastics were negatively correlated with the achieved intrusion amount. The initial overbite, overjet, crowding, upper central incisor inclination, amount of the first series of aligners, canine attachment type, posterior teeth attachment type and bite ramps had no significant correlation with the achieved intrusion amount.@*Conclusion@# In maxillary first premolar extraction cases treated with clear aligners, the upper central incisors have lower efficacy of intrusion movement than the lateral incisors. The achieved intrusion amount of maxillary incisors was influenced by multiple factors, which should be considered comprehensively for better vertical control in such cases.

A method for sensitivity analysis of deviation factor for geometric correction of cone-beam CT system / 南方医科大学学报

OBJECTIVE@#To propose a sensitivity test method for geometric correction position deviation of cone-beam CT systems.@*METHODS@#We proposed the definition of center deviation and its derivation. We analyzed the influence of the variation of the three-dimensional spatial center of the steel ball point, the projection center and the size of the steel ball point on the deviation of geometric parameters and the reconstructed image results by calculating the geometric correction parameters based on the Noo analytical method using the FDK reconstruction algorithm for image reconstruction.@*RESULTS@#The radius of the steel ball point was within 3 mm. The deviation of the center of the calibration parameter was within the order of magnitude and negligible. A 10% Gaussian perturbation of a single pixel in the 3D spatial coordinates of the steel ball point produced a deviation of about 3 pixel sizes, while the same Gaussian perturbation of the 2D projection coordinates of the steel ball point produced a deviation of about 2 pixel sizes.@*CONCLUSION@#The geometric correction is more sensitive to the deviation generated by the three-dimensional spatial coordinates of the steel ball point with limited sensitivity to the deviation generated by the two-dimensional projection coordinates of the steel ball point. The deviation sensitivity of a small diameter steel ball point can be ignored.

Comprehensive orthodontic treatment of impacted teeth / 口腔疾病防治

@#Impacted teeth are a kind of complex malocclusion, and their incidence differs among different races, sexes and dental positions. The causes of impacted teeth include systemic factors and local factors, such as endocrine disorders, malnutrition, and acute and chronic infectious diseases. Local factors can cause abnormal tooth development or eruption during the process from tooth development to tooth eruption, such as damaged permanent tooth embryos caused by local inflammation or trauma, insufficient eruption space caused by premature loss of deciduous teeth, and eruption disorders caused by local lesions for example hyperplasia or odontoma. The clinical manifestation of impacted teeth is the absence of a permanent tooth in a normal position. We can use cone beam CT (CBCT) to locate the impacted teeth. Comprehensive orthodontic treatment includes surgical-assisted eruption, extraction of retained deciduous teeth or supernumerary teeth, removal of lesions such as odontomas and cysts, and expansion of the orthodontic space. When the dysfunctional local soft and hard tissues are removed during a surgical operation, the tooth still cannot sprout smoothly, and it needs to be assisted by orthodontic traction-guided eruption or extracted and autotransplantation. A clear diagnosis, evaluation of the difficulty of treatment and appropriate treatment are the keys to improving the success rate of treatment. In this paper, the epidemiology, etiology, diagnosis and corresponding treatment methods of impacted teeth will be reviewed, and the orthodontic treatment of impacted teeth will be comprehensively described to provide a reference for clinicians about the treatment of impacted teeth.

3D finite element analysis of the influence of upper lip pressure on the maxilla for patients with unilateral alveolar cleft / 口腔疾病防治

Objective @#To investigate the biomechanical effects of upper lip pressure on the maxilla in patients with a unilateral alveolar cleft and provide evidence for clinical diagnosis and treatment. @*Methods @#A 3D finite element maxillary model was generated based on cone beam CT (CBCT) data from an 11-year-old female patient with a unilateral alveolar cleft. Two different kinds of upper lip pressure, postsurgery pressure and normal pressure, were applied to the model. The displacement and stress of each reference node were compared and analyzed. @*Results @# By loading upper lip pressure, the maxillary alveolar crest rotated toward the defect and was displaced downward and backward. The displacement of the noncleft side was greater than that of the cleft side and it decreased gradually from the anterior to the posterior. The stress was concentrated on the anterior portion of the alveolar crest. The stress on the noncleft side was greater than that on the cleft side and it decreased gradually from the anterior to the posterior. The maximum stress was concentrated on the palate around the defect. The displacement and stress in the postsurgery group were greater than those of the normal group (P<0.05). @*Conclusion @#By loading upper lip pressure, the maxilla demonstrated asymmetry three-dimensionally. The adverse effects on the maxilla could be mitigated by reducing the upper lip pressure.

Application of SGRT Combined with IGRT Isocenter Dual-guided Resetting in IMRT for Breast Cancer / 中山大学学报(医学科学版)

ObjectiveThe objective is to investigate the possibility of isocenter dual-guided resetting of surface guided radiation therapy （SGRT） combined with image guided radiation therapy （IGRT） in postoperative radiotherapy for breast cancer. To assess the setup error accuracy between the new resetting mode and the traditional resetting mode. MethodsRetrospective analysis was performed on breast cancer patients who underwent ELEKTA infinity accelerator radiotherapy in sun yat-sen university cancer center from July 13， 2021 to October 15， 2022. According to different reset methods， the patients were divided into a simulation group （41 cases） and a dual-guided group （40 cases）. The simulation group was reset using a simulator， CBCT scans were performed and setup errors were recorded during the first treatment； The dual-guided group was guided by AlignRT and combined with CBCT for isocenter dual-guided resetting， and the setup error obtained by CBCT registration was recorded. The global setup errors of chest region of interest （CROI） ， the local residual errors of supraclavicular region of interest （SROI） and the resetting time of the two reset methods were calculated and compared respectively. The advantages of the CBCT error distribution in the dual-guided resetting of SGRT combined with IGRT were analyzed. ResultsThe median of the global setup errors （X/cm， Y/cm， Z/cm， Rx°， Ry°， Rz°） of the simulation group and the median of the dual-guided group in the CROI were statistically significant （P<0.05） except the Rz and Ry directions. The local residual errors of the two groups of the SROI were calculated. The median of the errors of X/cm， Y/cm， Z/cm， Rx°， Ry°， Rz° were statistically significant （P<0.05） except the X and Y axis. The resetting time of the simulation group was significantly longer than that of the dual-guided group （238.64±28.56） s， t=-24.555， P=0.000， and the difference was statistically significant （P<0.05）. The CBCT error distribution of the dual-guide group was analyzed， and it was found that the absolute values of translation errors of X， Y and Z axis were all within 0.4 cm， while the proportions of ≤ 0.3 cm were 95%， 93% and 93%， respectively. The proportions of rotation errors of Rx， Ry and Rz ≤ 1.5 ° were 90%， 93% and 90%， respectively. ConclusionIn postoperative radiotherapy of breast cancer， SGRT combined with IGRT for isocenter dual-guided resetting can effectively correct the rotational setup errors and residual errors， and improve the accuracy of radiotherapy with less resetting time and high feasibility， which compared with the traditional simulator resetting mode. This precise， unmarked resetting method can be widely used in clinical practice.