快速整体内收上颌前牙对犬牙根吸收影响的扫描电镜观察

目的研究牙槽外科辅助快速整体内收上颌前牙对实验犬前牙牙根的影响。方法建立牙槽外科辅助快速整体内收上颌前牙的比格犬动物模型后,连续加力12 d,速度0.5 mm/d,分别于加力停止并固定1 d,14 d,28 d后随机处死3只实验犬,拔出一侧上颌第三切牙,制备标本行扫描电镜观察。结果加力停止1 d及14 d后牙根吸收明显,停止加力28 d后,牙根吸收面积明显减小:牙根颈部28 d与1 d(t=25.075,P=0.014)、28 d与14 d(t=17.444,P=0.056)比较,差异有统计学意义;牙根尖部28 d与1 d(t=26.436,P=0.000)、28 d与14 d(t=18.229,P=0.003)比较,差异有统计学意义。结论牙槽外科辅助快速整体内收上颌前牙会造成一定程度的牙根吸收,随着加力停止后固定时间的延长,牙根吸收可明显修复。     

Root resorption after orthodontic intrusion and extrusion: an intraindividual study

The aim of this investigation was to compare root resorption in the same individual after application of continuous intrusive and extrusive forces. In nine patients (mean age 15.3 years), the maxillary first premolars were randomly intruded or extruded with a continuous force of 100 cN for eight weeks. Eleven maxillary first premolars from six randomly selected orthodontic patients served as controls. Root resorption was determined using scanning electron microscopy. Quantitative assessment of the percentage of resorbed area of the total root surface was performed on composite micrographs. The severity of root resorption was also assessed by visual scoring of the roots. Root resorption mainly occurred at the apical part of the roots in both experimental groups. A significant difference in root resorption was found between the intruded and the control teeth (P = .006) but not between the extruded and the control teeth. However, the mesial and distal root surfaces showed resorption on 5.78 +/- 3.86% of the root surface of the intruded teeth and 1.28 +/- 1.24% of the root surface of the extruded teeth, and this difference was significant (P = .004). In addition, a large individual variation was found. From this study, it can be concluded that intrusion of teeth causes about four times more root resorption than extrusion. Because the amount of root resorption due to intrusion or extrusion in the same patient is correlated, every clinician should be aware that the extrusion of teeth might also cause root resorption in susceptible patients.     

高位J钩引起牙根吸收的临床观察

目的:评价标准方丝弓配合高位J钩对正畸治疗中牙根吸收的影响。方法:随机选择60例经过标准方丝弓技术治疗的安氏Ⅰ类或Ⅱ类Ⅰ分类伴上颌前突年轻女性患者,其中30例在内收前牙阶段应用高位J钩配合治疗。治疗前后拍摄全颌曲面断层片,分别测量2组治疗前后上颌4个切牙的牙根吸收等级,并经计算机进行χ2检验。结果:2组正畸治疗后均有明显的牙根吸收,治疗前后牙根吸收等级比较,2组均有显著性差异(P<0.01)。治疗后2组间牙根吸收等级比较,差异也呈显著性(P<0.01),标准方丝弓配合高位J钩组还出现了极重度吸收。结论:标准方丝弓配合高位J钩在正畸治疗中较单纯使用标准方丝弓技术更易产生严重的牙根吸收。     

Association between ectopic eruption of maxillary canines and first molars

The purpose of this study was to elucidate a possible association between ectopic first molar eruption causing root resorption on the distal root of the primary maxillary second molar, and ectopic canine eruption causing root resorption on the permanent maxillary incisors.The subjects consisted of 30 patients, 22 females and eight males in the age range 8.3-15.0 years in whom root resorption of the permanent maxillary lateral and/or central incisor caused by the erupting permanent canine was diagnosed, and clinical and/or radiographic information concerning maxillary first molar eruption existed.It was found that of the 30 patients, seven (23.3 per cent) also had pathological root resorption of the second primary molar caused by ectopic molar eruption.It is suggested that patients with ectopic maxillary first molar eruption leading to pathological root resorption of the maxillary second primary molar are followed closely during the period of premolar and canine eruption, as the ectopic first molar could be an early warning of an increased risk of ectopic canine eruption leading to root resorption of the maxillary permanent incisors.     

Periapical condition of anterior teeth after surgical correction of mandibular prognathism. A radiographic study.

Extrusion and root resorption of the mandibular anterior teeth have been reported after surgical correction of mandibular prognathism by horizontal osteotomy of the rami. The aim of the present study was to find out whether oblique sliding osteotomy also has such side effects. Intraoral radiographs of the maxillary and mandibular anterior teeth of 61 patients were studied. Enlargement of the periodontal space and signs of root resorption were estimated postoperatively and at a later review 1 1/2-5 years after the operation. Enlargement of periodontal space occurred postoperatively in 16.2% of the maxillary incisors and 52.2% of the mandibular incisors. The enlargements were mostly reversible and at the final review only 1.1 and 8.5% of the maxillary and mandibular incisors, respectively, showed such enlargements. Root resorption was rarely found in radiographs from the postoperative control. At the final review, however, there were signs of root resorption of 1.6 and 20.8% of the maxillary and mandibular incisors, respectively. It appears warranted to conclude that the anterior teeth, especially the mandibular incisors, are exposed to strong forces also after oblique sliding osteotomy of the mandibular rami.     

Orthognathic treatment case after severe root resorption in the early treatment stage

This article presents an orthognathic treatment case after severe apical root resorption of maxillary anterior teeth using anterior segmental osteotomy.This case involved a 20-year-old female with the chief complaint of maxillary protruding and irregularly aligned mandibular anterior teeth. Her medical history showed no allergies or medical problems. The overbite was +3.0 mm, and the overjet +3.0 mm. After extraction of the four first premolars, a multi-bracket treatment was started. A severe root resorption of the maxillary anterior teeth was found 12 months after active treatment. The maxillary anterior segmental osteotomy was chosen as the compensatory treatment. The total treatment period was 2 years and 7 months. The post-retention panoramic radiograph showed no developmental root resorption.     

Physiological root resorption of primary molars.

Physiological root resorption of primary molars was assessed using bitewings and orthopantomograms. Thirty-six per cent of teeth examined demonstrated reduced root resorption of one or more roots. Excepting the lower first primary molar, the present study recorded a relatively high incidence of uneven root resorption during the exfoliative process, particularly evident for the upper second primary molar. Discrepancy in size between the premolar and its predecessor, as well as the position of the developing permanent tooth in relation to primary root structure influences the pattern of root resorption. Therefore, constant monitoring of teeth demonstrating uneven resorption is required to avoid the complications associated with over-retained teeth.     

Apical root resorption after orthodontic treatment in patients with unilateral cleft lip and palate

Clinical Oral Investigations - The aims of this retrospective longitudinal study were to present the incidence of external apical root resorption (EARR) in the maxillary anterior teeth of patients...     

Patterns of incisor root resorption before and after orthodontic correction in cases with anterior open bites.

External root resorption is a frequent iatrogenic consequence of orthodontic treatment, particularly in the maxillary anterior teeth. Since resorption also occurs is a normal function of aging and since altered behaviors such as bruxism and chronic nailbiting accelerate resorption even in the absence of treatment, it was hypothesized that the long-term orthopedic forces of tongue thrusting leading to anterior open bites would also enhance the rates of clastic activity. In a series of 32 adolescents with open bites, the roots of permanent maxillary central incisors were significantly shorter and exhibited higher modal grades of periapical resorption than a matched series with deep bites before treatment. The open bite group also had less facial bony support for these teeth. Both series experienced discernible resorption during full-banded treatment but to comparable extents so that, after active treatment, the open bite series continued to possess significantly greater degrees of resorption. Consequently, the oral forces leading to apertognathia are themselves destructive of root integrity and merit early recognition and interception.     

Analysis of stress in the periodontium of the maxillary first molar with a three-dimensional finite element model.

The aim of this study was to simulate the stress response in the periodontium of the maxillary first molar to different moment to force ratios, and to determine the moment to force ratio for translational movement of the tooth by means of the finite element method. The three-dimensional finite element model of the maxillary first molar consisted of 3097 nodes and 2521 isoparametric eight-node solid elements. The model was designed to dissect the periodontal ligament, root, and alveolar bone separately. The results demonstrate the sensitivity of the periodontium to load changes. The stress pattern in the periodontal ligament for a distalizing force without counterbalancing moments showed high concentration at the cervical level of the distobuccal root due to tipping and rotation of the tooth. After various counterrotation as well as countertipping moments were applied, an even distribution of low compression on the distal side of the periodontal ligament was obtained at a countertipping moment to force ratio of 9:1 and a counterrotation moment to force ratio of 5:1. This lower and uniform stress in the periodontal ligament implies that a translational tooth movement may be achieved. Furthermore, high stress concentration was observed on the root surface at the furcation level in contrast with anterior teeth reported to display high concentration at the apex. This result may suggest that the root morphology of the maxillary first molar makes it less susceptible to apical root resorption relative to anterior teeth during tooth movement. The stress patterns in the periodontal ligament corresponded with the load types; those on the root appeared to be highly affected by bending and the high stiffness of the root.     

Predicting and preventing root resorption: Part II. Treatment factors.

The main objective of this study was to determine which treatment factors are most clearly identified with external apical root resorption that is detectable on periapical radiographs at the end of orthodontic treatment. The records of 868 patients who completed fixed, edgewise treatment from experienced clinicians in private practice were examined. The horizontal and vertical displacement of the root apex of the maxillary central incisor was measured on cephalometric radiographs. Patients who underwent first premolar extraction therapy had more resorption than those patients who had no extractions or had only maxillary first premolars removed. Duration of treatment and the horizontal (but not vertical) displacement of the incisor apices were significantly associated with root resorption. No differences were found for slot size, archwire type, use of elastics, and types of expansion. However, there was considerable variation among the 6 offices that were surveyed; 1 office averaged nearly a full millimeter more of resorption per anterior tooth than the office with the least amount of root resorption. We conclude that the clinician should exercise caution with those patients in whom extraction therapy is planned for overjet correction that requires above average treatment time. Finally, each clinician should be aware that the root resorption seen in one practice may be different from the root resorption found in another practice.     

2种阻生牙拔除法联合即刻种植的效果评价

目的 评价高速涡轮机微创技术与传统技术联合即刻种植对阻生牙术后镇痛、开口度及牙槽骨吸收的效果。方法 选择2014年1月—2018年12月在宿迁市人民医院进行治疗的阻生牙患者80例作为研究对象,使用数字表将患者随机分为实验组和对照组,每组40例。实验组患者采取高速涡轮机微创手术联合即刻种植治疗,对照组患者采用传统手术联合即刻种植治疗,观察2组患者术后牙槽骨吸收、疼痛、肿胀、开口受限、拔牙窝完整性以及并发症之间的差异。采用SPSS 19.0软件包对数据进行统计学分析。结果 术后3个月,实验组患者的上颌前牙区、上颌磨牙区、下颌前牙区以及下颌磨牙区的种植体高度均显著低于对照组。术后1 d,实验组患者的VAS评分显著低于对照组（P<0.05）;术后3个月,2组患者VAS评分之间的差异无统计学意义（P>0.05）。术后3个月,实验组患者的拔牙窝完整性、肿胀度以及开口受限程度显著低于对照组;实验组患者的术后牙根折断、邻牙松动、牙龈撕裂和舌侧骨板骨折均显著低于对照组。结论 阻生牙拔除术中采用高速涡轮机微创治疗联合即刻种植,患者术后牙槽骨吸收、肿胀以及拔牙窝完整性显著改变,术后疼痛感降低,并发症较少,值得推广应用。     

Is mild dental invagination a risk factor for apical root resorption in orthodontic patients?

The purpose of this retrospective study was to assess if dental invagination is a risk factor for root resorption during orthodontic treatment. The sample consisted of 91 patients (32 males, 59 females) with a mean age of 13.1 years (range 9.3-32.1 years) with complete orthodontic records, including periapical radiographs of the maxillary incisors before and after treatment. Forty-nine patients had at least one maxillary incisor invaginated, whilst the remaining 42 patients were free of dental invaginations. Variables recorded for each patient included gender, age, Angle classification, extraction or non-extraction therapy, ANB angle, overjet, overbite, trauma, habits, agenesis, tooth exfoliation, treatment duration, Class II elastics, body-build, general factors, impacted canines, and root form deviation. Crown and root length of the maxillary incisors were measured on pre- and post-treatment long cone periapical radiographs corrected for image distortion. The percentage of root shortening and root length loss in millimetres was then calculated. Most of the invaginated teeth were minor type 1. Statistical analysis revealed no significant difference in the severity of apical root resorption between invaginated and non-invaginated incisors in patients without dental invaginations, nor was the extent of dental invagination related to the severity of apical root resorption. However, invaginated teeth had malformed roots more often than non-invaginated teeth. Dental invagination, and particularly type 1, cannot be considered a risk factor for apical root resorption during orthodontic tooth movement.     

不同牙槽骨高度的磨牙压低时牙周膜应力分析

目的：通过建立具有不同牙槽骨高度的上颌第一磨牙三维有限元模型,在压力载荷下,计算分析其牙周膜应力的大小和分布,为正畸治疗提供力学参考。方法：采用CT对上颌第一磨牙进行扫描,建立牙槽骨发生不均衡水平吸收的上颌第一磨牙的三维有限元数字模型,计算加载垂直向的压低力时,牙周膜应力的大小和分布。结果：当牙槽骨从正常高度降低3.5 mm时,加载产生的牙周膜应力增加平缓,高应力集中部位在根分叉处;而牙槽骨降低超过6.0 mm,根分叉部分暴露时,牙周膜应力明显增加,应力集中的部位转移至根尖及根1/3处。结论：当牙槽骨高度降低未超过6 mm时(牙槽骨吸收未超过根长的48%),应根据牙槽骨的丧失程度来减小矫治力值;当牙槽骨高度降低6 mm以上时(牙槽骨吸收超过根长48%),磨牙的根分叉完全暴露,则应显著减小矫治力值。     

Bilateral root resorption of maxillary first permanent molars by unerupted second molars associated with orthodontic distalisation

Root resorption is a common but undesirable side-effect of orthodontic treatment. It is a well-recognised phenomenon largely associated with impacted or unerupted teeth and in most cases, is mild and does not affect longevity of the affected teeth. This case report of a medically fit and healthy Caucasian boy who was undergoing orthodontic treatment at the Eastman Dental Hospital, UCLH (EDH) for management of his severe hypodontia, presents an unusual incident of bilateral resorption of his maxillary first permanent molars by the unerupted second molars. The near end-of treatment radiographs showed that both upper second molars were mesio-angularly impacted and resorbing the first molars; however, the patient reported no associated signs or symptoms. Bilateral Cone Beam Computed Tomography radiographs were requested for the posterior maxillary arch in the area of the molar dentitions and extensive root resorption affecting the first molars caused by the crown of the mesio-angularly impacted second molars was evident. This unusual bilateral root resorption of maxillary first molars associated with unerupted second molars is an uncommon presentation, with no similar case reports found in the literature. Great emphasis should be placed on informed valid consent and potentially making the patient aware of the small but potential risk of resorption of erupted terminal molars where orthodontic molar distalisation is considered.     

Intrusion of overerupted molars by corticotomy and orthodontic skeletal anchorage

This article describes the orthodontic treatment of a 26-year-old female patient with overerupted left maxillary molar teeth. Her chief complaint was that the maxillary left first and the second molar intruded into the space required for the mandibular left first and the second molars, preventing prosthodontic treatment. The authors performed a corticotomy and used orthodontic skeletal anchorage with a miniplate and orthodontic miniscrews with a head modified to provide a specially designed hook. With this approach, they were able to achieve a sufficient amount of molar intrusion without discomfort, root resorption, or extrusion of the adjacent teeth. The first molar was intruded 3.0 mm and second molar was intruded 3.5 mm during 2 months of treatment. These results have been maintained for 11 months.     

Root canal systems of the mandibular and maxillary first permanent molar teeth of south Asian Pakistanis

AIM: The purpose of the present ex vivo study was to investigate variations in the root canal systems of mandibular and maxillary first permanent molar teeth of South Asian Pakistanis. METHODOLOGY: The root canal systems of a sample of 30 mandibular and 30 maxillary first permanent molar teeth extracted from South Asian Pakistanis were studied using a clearing technique. RESULTS: The mesial roots of the mandibular molar teeth typically presented with two canals (97%) of type II, IV or VI configuration. The distal roots of these teeth presented with a single canal (50%) of type I or V configuration or with two canals (50%) of type II, IV or VI. The prevalence of four root canals in two-rooted mandibular first permanent molar teeth was 47%. In maxillary molar teeth the mesial roots with a single canal (47%) were type I or type V; those with two canals (53%) were type II, IV or type VI. The distal and palatal roots that presented as a single canal (100%) were type I or type V configuration. The prevalence of four root canals in three-rooted maxillary first permanent molar teeth was 53%. CONCLUSION: It is concluded that four root canals in mandibular and maxillary first permanent molar teeth of South Asian Pakistanis is a common occurrence. The distribution of the different configurations of root canal systems in this population differed from that in Caucasian groups, suggesting that variations in root canal systems may be attributed to racial divergence.     

Primary teeth in adults--a pilot study

Remaining primary teeth are occasionally found in adults. The cause and the long-term survival may vary.The aim of this investigation was to study the occurrence and condition of primary teeth in adults in a county in Sweden. All dentists in general practice were asked to send in radiographs showing remaining primary teeth in patients aged 18 years and more. The following variables were registered: 1) age, 2) gender, 3) year of exposure of the radiograph, 4) location of the primary tooth, 5) impaction of the permanent successor, 6) fillings or caries in the primary tooth, 7) amount of root resorption and 8) infraocclusion of the primary tooth. 35 dentists contributed with radiographs from 65 subjects showing 89 retained primary teeth.The most commonly found tooth was the second primary molar in the mandible, followed by the primary canine in the maxilla. Except for maxillary molars, most of the primary teeth showed a moderate degree of root resorption. No relationship was found between the degree of root resorption and gender, fillings/caries or infraocclusion. For the mandibular primary molars, there was a statistically significant correlation between root resorption and age. The mesial root of the molar in the mandible was more affected by root resorption than the distal, and the degree of root resorption of the mesial and distal roots was found to be closely correlated. Also, the results indicated a symmetrical pattern of root resorption in bilateral cases of remaining mandibular second primary molars.     

Root resorption associated with autotransplanted maxillary canine teeth

A brief review of the published results of autotransplanting maxillary canine teeth has been presented together with the results of a prospective study in which 141 maxillary canine teeth were surgically repositioned in 113 patients, but not root-treated unless resorption occurred. Attention was given to assessing factors (age, sex, tooth positions, surgical difficulty, time out of mouth, acute infection, periodontal disease, caries, occlusion, formation of lamina dura) associated with root resorption of the transplanted teeth but no particular factor of significance emerged. It has been speculated that early post-operative root canal treatment and/or a two-stage technique might reduce the incidence of root resorption of autotransplanted teeth.     

新型压低下颌磨牙矫治器的临床应用

目的 评估新型压低下颌磨牙矫治器压低下颌磨牙的疗效及应用价值.方法 选择7例需要压低下颌磨牙治疗的前牙开患者,治疗前、后通过临床检查、牙颌模型分析及采用Winceph7.0数字化X线片分析软件测量头颅侧位片,评价临床压入效果,使用SPSS 17.0统计软件包对数据进行分析.结果 7例患者经过平均4个月的治疗,均取得比较明显的治疗效果.治疗前、后头影测量分析表明:下颌第一磨牙的平均压入量为(1.92±0.44)mm,矫治前、后相对于基准平面(MP平面)的垂直距离差异有统计学意义(P<0.05).上颌第一磨牙平均压入量为(0.36±0.25)mm,矫治前、后相对于基准平面(PP平面)的垂直距离差异没有统计学意义(P>0.05).X片显示被压低的下颌磨牙未出现明显的牙根吸收.结论 新型下颌磨牙压低矫治器用于压入下颌磨牙治疗前牙开畸形效果明显,压入治疗未引起明显的牙周及牙根损害.