Aim or purpose: This study aims to develop a mechanical principle for reducing the crush injury of bone in tooth extraction.[Geostatics in minimally invasive surgical exodontias. West China J of Stomatology, 2017, 35(2):119 10.7518/hxkq.2017.02.002] Materials and methods: This study was verified by IRB of West China Hospital of Stomatology (WCHSIRB-D-2020-323). The tooth and alveolar socket were considered as rigid body with definite shapes and sizes. The principles of geostatics were employed to analyze the retention of tooth roots following the theory of statically determinate structures. The principles of mechanics were applied to analyze dislocation of teeth following the theory of translatory motion and rotational motion. Those principles yield were verified in vivo if it suitable for tooth extraction. Results: Considered as deep buried static structure, the constraint of tooth root are mainly determined by geometric shape, especially tooth root curvature and cross dislocation direction. The slope principle is useful to analyze the cause of the constraint and figure out the solution. In accordance with the theory of the rotation about point, the differential motion principle was suggested for dislocation of root without compressing sockets. A well-designed root-cutting would form a rotation center that made the root dodging the obstacle-point along the direction of the differential motion. Conclusions: The slope principle and the differential motion principle derived from geostatics theory is feasible for mechanical analysis of tooth extraction, and provide practicable solution for minimal tooth extraction.

ObjectivesThis study pursued two main purposes. The first aim was to expound on the microscopic factors of radiation-related caries (RRC). Further, it aimed to compare the remineralization effect of different remineralizing agents on demineralized teeth after radiotherapy.MethodsThe enamel and dentin samples of bovine teeth were irradiated with different doses of radiation. After analysis of scanning electron microscope (SEM), X-Ray diffraction (XRD), and energy dispersive spectrometer (EDS), the samples irradiated with 50 Gy radiation were selected and divided into the demineralization group, the double distilled water (DDW) group, the Sodium fluoride (NaF) group, the Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) group, the NaF + CPP-ACP group, and the Titanium tetrafluoride (TiF4) group. After demineralization, remineralizing agents treatment, and remineralization, the samples were evaluated using SEM, atomic force microscope (AFM), EDS, and transverse microradiography (TMR).ResultsA radiation dose of 30 Gy was sufficient to cause damage to the dentinal tubules, but 70 Gy radiation had little effect on the microstructure of enamel. Additionally, the NaF + CPP-ACP group and the TiF4 group significantly promoted deposit formation, decreased surface roughness, and reduced mineral loss and lesion depth of demineralized enamel and dentin samples after radiation.ConclusionsRadiation causes more significant damage to dentin compared to enamel. NaF + CPP-ACP and TiF4 had a promising ability to promote remineralization of irradiated dental hard tissues.Advances in knowledgeThis in vitro study contributes to determining a safer radiation dose range for teeth and identifying the most effective remineralization approach for RRC.

Pregnancy is a special period for developing and treating oral diseases. Oral emergencies during pregnancy need to be handled appropriately. Changes in the physiological environments and personal habits of pregnant women increase susceptibility to some oral diseases. However, clinical treatment strategies are limited due to the need to ensure the safety of pregnant women and fetuses. Pregnant women should obtain oral health knowledge and enhance their awareness. Dentists should adhere to the principle of "prevention before pregnancy, controlling symptoms during pregnancy, and treating diseases after pregnancy" for different pregnancy periods. They should also formulate appropriate treatment plans to control emergencies, prevent disease progression, and avoid harmful effects on pregnant women by using the safest, simplest, and most effective strategies that avoid adverse effects on fetuses. Pregnant women and dentists should combine prevention and treatment while collaborating in maintaining oral health during pregnancy. This article focuses on the principles of treatment during pregnancy, and the treatment timing, clinical management, and treatment strategies of different diseases causing oral emergencies during pregnancy are reviewed.

Radiation therapy is applied in the treatment of head and neck cancer patients. However, oral-health-related side effects like hyposalivation and a higher prevalence of caries have been shown. This study aims to assess the influence of different radiotherapy doses on the mechanical properties, roughness, superficial microstructure, and crystallinity of the enamel and dentin of human premolar teeth. Specimens (n = 25) were categorized into five groups based on the radiation dose received (0, 10, 30, 50, and 70 Gy). The enamel and dentin of these specimens were subjected to a microhardness tester, profilometer, atomic force microscopy (AFM), scanning electron microscopy (SEM), and X‑ray diffraction (XRD) before and after different irradiation doses and compared to hydroxylapatite in each group. The data were analyzed using repeated-measures analysis of variance (ANOVA). Therapeutic radiation doses of 30, 50, and 70 Gy led to a decrease in the microhardness and an increase in the average roughness of the enamel, and rougher surfaces were observed in the mixed three-dimensional images. Moreover, in the dentin, a similar outcome could be observed for more than 10 Gy. The main crystalline phase structure remained hydroxylapatite, but the crystallinity decreased and the crystalline size increased above 10 Gy. The superficial micromorphology revealed granulation, fissures, and cracks in a dose-dependent manner. Radiation below 70 Gy had little effect on the hydroxylapatite concentration during the whole experiment. Above a radiation dose of 30 Gy, the micromorphology of the tooth enamel changed. This occurred for dentin above 10 Gy, which indicates that dentin is more sensitive to radiotherapy than enamel. The radiation dose had an effect on the micromorphology of the hard tissues of the teeth. These results illustrate the possible mechanism of radiation-related caries and have guiding significance for clinical radiotherapy.

Objectives: To investigate the characteristics of spatial changes in molars and alveolar bone resorption among patients with loss of mandibular first molars. Methods: A total of 42 CBCT scans of patients with missing mandibular first molars (3 males, 33 females) and 42 CBCT scans of control subjects without loss of mandibular first molars (9 males, 27 females) were evaluated in this cross-sectional study. All images were standardized using the mandibular posterior tooth plane with Invivo software. The following indices regarding alveolar bone morphology were measured, including alveolar bone height, bone width, mesiodistal and buccolingual angulation of molars, overeruption of maxillary first molars, bone defects, and the capability of molar mesialization. Results: The vertical alveolar bone height in the missing group was reduced by 1.42 ± 0.70 mm, 1.31 ± 0.68, and 1.46 ± 0.85 mm on the buccal, middle, and lingual side, respectively (no differences among the three sides; p > 0.05). Alveolar bone width was reduced the greatest at the buccal CEJ level and the least at the lingual apex level. Mandibular second molar mesial tipping (with mean of the mesiodistal angulation = 57.47 ± 10.34°) and lingual tipping (with mean of the buccolingual angulation = 71.75 ± 8.34°) were observed. The mesial and distal cusps of maxillary first molars were extruded by 1.37 mm and 0.85 mm, respectively. Buccal and lingual defects of alveolar bone occurred at the CEJ, mid-root, and apex levels. Through 3D simulation, the second molar cannot be successfully mesialized into the missing tooth position, and the difference between the available and required distances for mesialization was the greatest at the CEJ level. The duration of tooth loss was significantly correlated with the mesio-distal angulation (R = −0.726, p < 0.001), buccal-lingual angulation (R = −0.528, p < 0.001) and the extrusion of the maxillary first molar (R = −0.334, p < 0.05). Conclusion: Both vertical and horizontal resorption of alveolar bone occurred. Mandibular second molars exhibit mesial and lingual tipping. Lingual root torque and uprighting of the second molars are needed for the success of molar protraction. Bone augmentation is indicated for severely resorbed alveolar bone.

The mandibular ramus region is a bony platform located between the external and internal oblique ridges. The mandibular ramus was first proposed as a viable anatomical region for orthodontic temporary anchorage devices in 1998 and has been gaining popularity in the orthodontic community. In clinical practice, ramus mini-implants are mostly employed for uprighting deeply impacted mandibular molars that are refractory to routine orthodontic biomechanics. Optimal insertion sites should offer mini-implants with adequate bone quality and sufficient bone quantity. Practitioners should determine the optimal insertion site for a specific patient requiring insertion of a ramus mini-implant based on radiographic examination. Patients are often anxious about the surgery, so good communication and per-insertion reassurance are necessary. Since the ramus mini-implant is located buccally, posteriorly and superiorly to impacted mandibular molars, a buccally, distally, occlusally directed uprighting force is applied to the impacted mandibular molar.

下牙槽神经功能障碍是下颌正颌手术、下颌后牙种植手术以及下颌第三磨牙拔除术后的一种常见并发症.虽然大部分情况下发生率较低,但一旦发生,部分患者的持续时间可以很久,而且不适感可能较为明显.因此,这一并发症备受口腔科医生和患者关注.下牙槽神经功能障碍常表现为术侧颏部和嘴唇皮肤的感觉减退与异常感觉,伴或不伴感觉过敏、患侧下颌牙列不适感等症状.大多数患者在神经功能障碍发生后的6个月内,可得到明显缓解,也有少部分患者在随访超过6个月甚至更长的时间后,仍无明显恢复.本文对不同类型的手术后所发生的下牙槽神经功能障碍的症状及预后特点进行综述,并尝试分析其差异和相关性.

口腔及颌面部创伤在运动损伤中占比较高,儿童和青少年及残疾人是运动损伤的高发群体.通过佩戴各类防护用具能够有效降低运动创伤的发生率,但国民的运动口腔防护意识普遍较薄弱.人们应当了解口腔及颌面部运动损伤的高发性、严重性,且运动护具的使用急需进一步普及推广.本文将对现有的运动口腔及颅颌面部防护用具及其研究进展作一综述,并简述残疾人运动损伤的防护策略.

Background/purpose: At present, there are no recognized guidelines or consensus for the treatment strategy of the asymptomatic tooth with external root resorption caused by an embedded tooth (et-ERR). Most clinicians would like prophylactic or concomitant root canal therapy (RCT) along with the extraction of the embedded tooth. The purpose of this study was to report the prognosis of external root resorption (ERR) and investigate the possibility to preserve the vital pulp of ERR tooth. Materials and methods: The patients who had asymptomatic et-ERR teeth were included. After extraction of the embedded tooth, the clinical process, prognosis, and adverse events were observed, including symptoms, clinical, and radiographic examination throughout the follow-up period. Results: A total of four cases with special features were reported. Over a follow-up period of up to 12 months, on clinical examination, 3 ERR teeth preserved pulp vitality without additional intervention except for tooth extraction and have kept normal function free from any symptoms. Radiographic examination showed bone regeneration and recovery of periodontal tissue. While one case failed to keep the vital pulp and ended in intentional replantation. Conclusion: As to et-ERR, if the embedded tooth can be promptly extracted with a minimally invasive technique and effective infection control, the pulp vitality of the et-ERR tooth is likely to be preserved. In this situation, the preferred management of asymptomatic et-ERR tooth is just followed up without prophylactic RCT.

OBJECTIVES:To thoroughly understand the current dental chair equipment status of dental clinics in Sichuan Province and provide a reference for administrative departments.METHODS:Data were collected from a health administrative department and a regional social development yearbook. The number of existing dental clinics and dental chairs in Sichuan Province was investigated.RESULTS:In Sichuan Province, 7 103 dental clinics were determined to be equipped with 21 760 dental chairs. The Gini coefficients of per capita dental clinics in the province were 0.50, 0.22, and 0.06, and the Gini coefficients of per capita dental chairs were 0.68, 0.31, and 0.15; these coefficients had the same distribution as that reflected by the Lorenz curve. In consideration of geographic distribution, the Theil index for the distribution of dental clinics and dental chairs among cities and states were 0.690 7 and 0.822 3, respectively. The overall Theil index va-lues for the distribution of dental clinics and dental chairs in the province were 0.902 4 and 1.079 4, respectively. The difference in the distribution of dental clinics and dental chairs among cities and states in the province contributed 0.765 4 and 0.761 8 to the total difference, respectively.CONCLUSIONS:The allocation of oral health resources in Sichuan Pro-vince is relatively equitable in terms of population and economic distribution but uneven in geographical distribution.

目的:动物咬伤、抓伤是口腔颌面部最常见的外伤性疾病之一,但目前对口腔颌面部动物咬伤、抓伤的患者是否应进行一期缝合仍存在争议.本研究将报道 1 例口腔颌面部熊抓伤一期缝合病例的治疗效果.诊治经过:患者,男性,49 岁,因面部被熊抓伤 20 小时来院就诊,12 小时前已接种破伤风、狂犬病免疫球蛋白及狂犬疫苗,在四川大学华西口腔医院彻底清创后对其进行了一期严密缝合,随访并记录了患者术后伤口感染、瘢痕愈合等情况.结果:患者一期缝合后伤口愈合良好,未出现术后伤口感染,且瘢痕较小,面部美观性较高.结论:对于可彻底清创的口腔颌面部动物抓伤患者,一期缝合可在不增加伤口感染率的同时改善术后美观功能,进而降低创伤对患者造成的容貌、生理及心理上的创伤.

BACKGROUND:An orthodontic traction technique with a miniscrew-anchored cantilever spring was used for the traction of a deeply impacted maxillary third molar to substitute its adjacent second molar with severe root resorption.CASE DESCRIPTION:A 30-year-old woman sought multidisciplinary treatment planning for a second molar with severe root resorption caused by a deeply impacted third molar. Panoramic radiographs and cone-beam computed tomographic images showed that the third molar was located on the apical and palatal side of the second molar and that the second molar had severe root resorption. The second molar was removed, and the impacted third molar was orthodontically tractioned occlusally with the aid of a miniscrew-anchored cantilever spring. After 12 months of orthodontic treatment, the maxillary left third molar was successfully tractioned occlusally and well aligned with adjacent teeth for the substitution of the second molar. The patient was satisfied with the treatment outcome.PRACTICAL IMPLICATIONS:A palatal miniscrew-anchored cantilever spring is an effective and viable technique for the orthodontic traction of deeply impacted third molars to substitute second molars with severe root resorption.

Abstract Purpose：The aim of this study was to compare and analyze the change of xerostomia and caries risk under the protection of the personalized PMMA oral stents before, during and after radiotherapy, and to determine its effectiveness in prevention of xerostomia.Methods：A total of 15 nasopharyngeal carcinoma (NPC) patients, who were receiving Intensity-modulated radiation therapy (IMRT) were included. Each patient was given a personalized polymethyl methacrylate (PMMA) oral stent. Assessment of xerostomia and caries risk was done before, during and after radiotherapy, at 1-month and 3-month intervals. Xerostomia was estimated by measurement of unstimulated and stimulated salivary flow rates (objective evaluation) and xerostomia questionnaire (subjective evaluation). Cariostat was used to assess Caries risk. The significance level was set at 0.05.Results：The average unstimulated saliva flow rate of patients in this study decreased gradually from Pre-RT (0.48ml/min) to Post-RT-3m (0.12ml/min). And the average stimulated saliva flow rate decreased gradually from Pre-RT (0.78ml/min) to Post-RT-1m (0.18ml/min) and followed by minimal recovery trend at Post-RT-3m (0.23ml/min). As for the percentage change of stimulated saliva, it dropped to 53.9% at Mid-RT and 41.7% at Post-RT-1m, but recovered to 44.6% at Post-RT-3m compared to the baseline. The average values of Cariostat scores are 1.292 at Pre-RT, 1.417 at Mid-RT, 1.583 at Post-RT-1m and 1.708 at Post-RT-3m. The score of Xerostomia questionnaire was negatively correlated with the percentage of unstimulated and stimulated saliva change(P<0.05).Conclusion：After radiotherapy, all NPC patients were troubled by xerostomia, and caries risk of most patients have increased. Stimulated salivary flow rate can be used as an objective indicator to evaluate xerostomia induced by radiotherapy. The patient-rated xerostomia may be an acceptable indicator of reduced saliva flow. The personalized PMMA oral stents can decrease the severity of xerostomia and improve the quality of life of NPC patients after radiotherapy.

Introduction: This prospective study was designed to determine the prognosis of second molars with external root resorption (ERR-M2s) caused by embedded third molars (EM3s) following EM3 removal and explore related predictors. Methods: This study consecutively enrolled 58 participants who had asymptomatic second molars with apical external root resorption caused by EM3s. EM3s were extracted, and follow-up examinations were conducted at 1 week, 4 weeks, and 6 months. The primary outcome was prognosis of ERR-M2s after third molar extraction without any further intervention, as assessed via clinical and radiographic examinations. Potential predictors (sex, age, number of roots, EM3s posi-tion, type and degree of external root resorption) of prognosis were analyzed via univariable and multivariable analyses. Results: A total of 63 ERR-M2s from 58 patients (16 males and 42 females; 19-57 years of age) were evaluated. At the last follow-up, 56 teeth (89%) remained asymptomatic and normal response to heat and cold tests. According to univariable analyses, ERR-M2s were more likely to remain normal response to heat and cold tests in younger patients. In the multivariable analysis, older age (odds ratio, 1.118; 95% confidence interval, 1.026-1.219; P < .05) and the type of all roots affected (odds ratio, 0.073; 95% confidence interval, 0.007-0.754; P < .05) were significantly associated with poor prognosis. Conclusions: Asymptomatic ERR-M2s have a high probability of remaining normal pulp without further intervention after EM3 extraction, especially in younger patients. No inter-vention except follow-up and observation is necessary. (J Endod 2022;48:1113-1120.)

白血病是一类较易出现口腔病变的全身性疾病,甚至以口腔表征为首发症状首诊于口腔科.口腔医生正确鉴别以口腔表征为首发症状的白血病,避免漏、误诊的发生,是保证这类患者获得早期诊断、早期治疗、提高白血病疗效的关键.正确鉴别白血病,是口腔住院医师规范化培训期间需要学习的重要内容,是培养具有临床胜任力的合格的口腔医生的必经之路.漏、误诊病例分析作为一种特殊的案例教学法,不仅可以作为"反面教材"提醒住院医师避免发生相同的错误,同时分析的过程也可以培养住院医师的逆向及全局思维.应用于以口腔表征为首诊的白血病初筛的教学,能够提高住院医师临床综合思维能力,达到培养住院医师胜任力的目的.

RoB2(revised version 2019), an authoritative tool for assessing the risk of bias in randomized controlled trials, has been updated and improved based on the original version. This article elaborated and interpreted the background and main content of RoB2(revised version 2019), as well as the operation process of the new software.Compared with the previous version of RoB2(revised version 2018), RoB2(revised version 2019) has the advantages of rich content, complete details, accurate questions, and simple operation, etc. Additionally, it is more user-friendly for researchers and beginners. The risk bias assessment of randomized controlled trials is more comprehensive and accurate,and it is an authoritative, trustworthy, and popular tool for evaluating the risk of bias in randomized controlled studies in medical practice.

目的 探讨CBL(case-based learning)联合MDT(multidisciplinary treatment)教学模式在口腔全科住院医师规范化培训(规培)中的应用效果.方法 将2018年9月和2019年9月各招收的20名口腔全科规培医师自动分为对照组和实验组.对照组采用传统教学模式,实验组采用CBL联合MDT教学模式.教学结束后采用理论考试、实践技能考试及问卷调查的方式评价教学效果.结果 实验组在实践技能考试及教学满意度上都明显优于对照组,差异具有统计学意义(P<0.05).结论 CBL联合MDT教学模式更好地调动了学生的积极性,锻炼了学生的全科思维,具有很好的教学示范及现实意义.

随着氧化锆陶瓷的广泛应用,氧化锆陶瓷的粘接问题一直是研究热点.本文就近年来研究的几种提高氧化锆陶瓷粘接性能的技术,从3个方面来进行综述:物理处理改变氧化锆的表面形貌;化学涂层提高氧化锆的表面性能;表面清洁去除唾液等污染.在传统处理方式的基础上,总结几项研究比较热门的表面处理方式,从技术原理、临床应用等方面进行阐述,为提高氧化锆陶瓷的粘接性能提供理论基础.

An orthodontic extraction technique with a ramus mini-screw was used to remove a deeply impacted mandibular third molar contacting the inferior alveolar nerve, avoiding damage to the inferior alveolar nerve and relieving postsurgery inflammation. Case presentation: A 24-year-old man was required to extract impacted third molars for orthodontic treatment. Panoramic radiographs and CBCT images showed that his mandibular left third molar penetrated into the inferior alveolar nerve canal and a distomolar was inverted and impacted distally to the third molar. The distomolar was directly removed and the impacted third molar was extruded with the aid of a ramus mini-screw. After 4 months of traction, the mandibular left third molar was successfully moved away from the inferior alveolar nerve canal. No nerve injury occurred after the surgical extraction and the patient was very satisfied with the treatment outcome. Conclusion: Orthodontic extraction, with the aid of ramus mini-screws, is a safe, effective, and efficient technique for the removal of high-risk impacted molars contacting the inferior alveolar nerve.