持续性压低重力致牙根吸收动物模型的建立

目的:基于牙根吸收机制研究的需要,以持续性压低重力作用于犬上颌切牙,建立在X线片上有牙根吸收指征的动物模型.方法:选用成年杂种雄性犬6条,以种植钉为支抗,对上颌切牙(共36个)施加持续性压低重力300 g,通过X线根尖片和对作用牙齿的大体形态和组织切片观察,研究牙根吸收的发生及进展情况.结果:经X线观察,有33个实验牙出现了牙根吸收现象:2周后根尖周出现稀疏区;6周后根尖区出现牙根组织缺损性吸收.对牙根大体形态进行观察,可见牙根形态不完整,根尖区吸收后成不规则形态截面.组织切片观察,可见根尖吸收区有大量单核、多核细胞聚集.结论:通过持续性压低重力作用方法,可建立起在X线片上可见的牙根吸收动物模型;持续性过大压低重力是造成正畸过程中牙根吸收的原因之一.     

微型种植体支抗压低犬上切牙的牙根表面扫描电镜观察

目的:利用微型种植体作为支抗,建立犬上切牙压低移动的实验动物模型,研究压低移动牙牙根表面结构的变化。方法:9只犬随机分为5组,其中Ⅰ组为对照组,1只犬,未施加牵引力;Ⅱ、Ⅲ、Ⅳ、Ⅴ组每组2只,在上颌两侧第二切牙牙根和第三切牙牙根之间唇侧的牙槽间隔处植入微型种植体作为支抗,每侧施加100g的牵引力,压低上颌两侧第一切牙和第二切牙,分别于加力后1、2、4、12周(主动加力4周,撤力后保持8周)时处死动物,完整拔出实验牙,制作扫描电镜标本,观察其牙根表面形态的变化。结果:Ⅱ组在牙根尖表面可见小的吸收陷窝,较浅,面积局限;Ⅲ组在接近根尖1/3处可见融合的吸收陷窝,未见牙本质暴露;Ⅳ组在根尖1/3与根中1/3交界处可见吸收深达牙本质的陷窝,且面积广泛;Ⅴ组牙根吸收停止,吸收凹陷变浅,底部变平。结论:在持续的压低力作用下,随着施力时间的延长,牙根的吸收由根尖部向牙颈部扩展,且逐渐加重。停止加力后,吸收牙根明显修复。     

应用微型种植体支抗压低犬后牙过程中牙周组织改建的组织学研究

目的:应用微型种植体支抗压低犬第三前磨牙,观察此方法压低牙齿时牙周组织的改建情况,为种植体支抗压低牙齿的正畸临床应用提供理论依据.方法:实验犬6只,在左右两侧上颌第三前磨牙颊侧和腭侧根分叉区各植入一枚微型种植体,使橡皮链跨越牙齿(牙合)面施力,力量控制为100 g,分别于加力后0、1、3、7、14、30 d处死一只犬,取第三前磨牙及其牙周组织进行标本处理、组织切片、HE染色观察.结果:第三前磨牙根尖区、根分叉区与牙槽嵴顶部牙周组织改建最为活跃,主要表现为骨吸收;而唇腭侧与近中远中侧牙周组织改建不显著.结论:应用种植体支抗压低犬第三前磨牙时,牙齿仅发生垂直向的压低移动.若压低牙齿力值过大, 会导致根尖吸收,因此在临床应用中应注重力值大小的选择,并尽可能使用持续性的力量压低牙齿.     

骨皮质切开术对比格犬前磨牙压入移动影响的三维形态学研究

目的 评估骨皮质切开术辅助前磨牙压低的加速效应和牙根、牙槽骨改建情况。方法 8只比格犬的下颌骨两侧随机分为实验侧、对照侧,实验侧用骨皮质切开术和微种植体支抗（MIA）压低第三前磨牙（P3）和第四前磨牙（P4）,对照侧用MIA压低P3和P4。在术前和加力后2、4、8、12周分别拍摄锥形束CT,分析P3、P4的压低量、根分叉和根尖区的牙根吸收量以及周围牙槽骨高度降低量。结果 实验侧牙齿的压低量明显大于对照侧（P<0.05）;实验侧和对照侧牙齿根分叉、根尖区的牙根均出现吸收,加力后12周实验侧根尖区牙根吸收小于对照侧（P<0.05）;牙槽骨高度随着加力时间的延长而降低,加力后8、12周时,对照侧牙槽骨高度降低量明显小于实验侧（P<0.05）。结论 骨皮质切开术能加速磨牙的压低,同时能减少压低过程中的牙根吸收。     

实验性犬乳牙根尖周炎组织病理学观察

目的：观察犬乳牙根尖周组织在开髓封内毒素状态下的组织病理学动态过程。方法：3只本地杂种幼犬乳牙分别于第1、7、14、21天开髓，封内毒素溶液，第28天处死，拍根尖周X线片，测量根尖周稀疏区面积；组织经HE染色进行观察分析。结果：自封药3周开始出现根尖周稀疏区；组织学变化显示封药1周即可见炎症细胞浸润，毛细血管扩张，部分受试牙出现尖周脓肿；2周后炎症细胞浸润加重，可见骨吸收；3周后根尖周牙骨质和牙槽骨的吸收较重。结论：犬乳牙开髓封内毒素后可建成实验性乳牙根尖周炎模型，炎症随时间延长而加重。     

前突患者上切牙内收前的牙根吸收状况及因素分析

目的 调查前突患者上切牙内收前的牙根吸收状况,并且对该阶段牙根吸收的影响因素进行初步的探索.方法 选择上颌需要拔除双侧第一前磨牙且需要强支抗的前突患者50名,分别于正畸治疗前（T1）和上切牙内收前（T2）拍摄上颌切牙的平行投照根尖片和头颅侧位片,通过测量和评价,得到每颗切牙的牙根吸收量、治疗前牙根形态及上中切牙的角度位置及变化量,并记录其他诊断和治疗因素.对牙根吸收量作描述性统计,对各因素作多因素分析.结果 ①前突患者上切牙内收前,中切牙的牙根吸收平均为（0.73±0.53）mm,侧切牙为（0.84±0.70）mm.②有3％的中切牙和6％的侧切牙牙根吸收大于2mm.③多元线性回归表明T1期牙根形态异常、内收前疗程长、上中切牙根尖距唇侧骨皮质的距离减小量大、T1期U1/PP角小、上颌前部拥挤为中切牙牙根吸收的危险因素.T1期牙根形态异常、上颌前部拥挤、内收前疗程长、T1期牙齿长度长为侧切牙牙根吸收的危险因素.结论 前突患者上切牙内收前有一定量的牙根吸收,个别高危患者其牙根吸收状况较严重.我们的研究因素中存在此阶段与上切牙牙根吸收相关的因素,但这些因素对于牙根吸收的解释仅为30％左右.     

短根牙急性挫伤后发生牙根内吸收1例

有研究报道,对于根尖发育完成的牙齿,嵌入性挫伤可导致牙髓失活,以及牙根吸收。而根尖形态异常或短根在受到外力后发生牙根吸收几率会大大增加[1]。本文报道短根牙急性挫伤后发生牙根内吸收以致最后拔除1例。患者女,12岁,因左侧上颌前牙变色发红来我院就诊。自诉病史:半年前进食时无意被筷子硌到左上侧切牙,疼痛3 d左右;近3个月发现该牙牙色逐渐变暗变红。否     

上切牙内收治疗与牙根吸收

上颌前突是正畸常见的错牙合畸形。正畸治疗过程中需要内收上前牙,而且很多病例需要增强上颌磨牙支抗来增加上切牙内收的程度。在此治疗过程中,上切牙是移动距离最大的牙齿,也是最容易发生牙根吸收的牙齿。上切牙在内收过程中其牙根吸收的发生状况究竟如何,牙根吸收与切牙移动有怎样的关系,许多学者对此进行了研究,现对以往的文献作一回顾。1上切牙内收治疗中牙根吸收的发生情况Simplicio等[1]使用内收前后的根尖片进行评价观察,拔     

不同力值下犬牙移入牵张成骨再生区的模型建立

目的 建立牵张成骨后在不同力值下将实验牙移入骨再生区的动物模型,并观察实验牙移动速度及牙根、牙周组织的改变.方法 选取8只beagle犬随机分AB两组,每组4只.行下颌骨牵张成骨术,保持期6周后分别施加50g、100g力值将实验牙向远中移入骨再生区,每2周加力一次,在实验牙移动的第0、1、2、3、4周后行根尖X线片,并测量移动距离;实验牙移动4周后处死动物,标本作大体观察,拍摄X线片以及根尖周片.结果 实验动物均耐受手术,牵张区间隙内被新生骨组织替代,基本获得预期牵张距离.测量计算实验牙移动的距离发现100g比50g力值移动实验牙的速度快,牙根未见明显吸收,牙周膜轻度增宽.结论 在牙齿移动的研究中,该系的犬可以建立稳定可靠的牵张成骨后牙齿移动的模型,为进一步研究提供了较好的平台.     

上颌阻生尖牙牵引治疗后邻近切牙牙根吸收情况的研究

目的 分析上颌阻生尖牙正畸牵引治疗后邻近切牙的牙根吸收情况及可能的相关因素。方法 选取上颌尖牙阻生且符合标准的43例患者,年龄10～23岁,共60颗上颌埋伏阻生尖牙。上颌阻生尖牙正畸牵引治疗前后分别拍摄锥形束CT,分析阻生尖牙邻近切牙的牙根吸收程度,并对可能存在的相关因素进行分析。结果 上颌阻生尖牙正畸牵引治疗后,上颌中切牙发生轻、中、重度牙根吸收的概率分别为71.7%、15.0%、13.3%,上颌侧切牙发生轻、中、重度牙根吸收的概率分别为48.3%、36.7%、15.0%,上颌中切牙与侧切牙牙根吸收严重程度存在差异(P<0.05)。位于腭侧及颌骨内、低位且靠近面中线的阻生尖牙,在正畸牵引治疗后,侧切牙牙根吸收程度较重(P<0.05)。低位阻生尖牙牵引治疗后,中切牙牙根吸收较重(P<0.05)。牵引时间较长时,中切牙牙根吸收程度较重(P<0.05)。治疗前已发生牙根吸收的切牙,在阻生尖牙牵引治疗后发生的牙根吸收程度较重(P<0.05)。结论 上颌侧切牙在阻生尖牙正畸牵引治疗后,发生的牙根吸收程度较重。上颌阻生尖牙正畸牵引治疗后,邻近切牙牙根吸收情况与阻生尖...     

Radiographic features of vertically fractured, endodontically treated maxillary premolars.

OBJECTIVE: The purpose of this study was to evaluate the most frequent radiographic appearance of bony lesions associated with vertically fractured roots of endodontically treated maxillary premolars. STUDY DESIGN: The radiographic features of 102 endodontically treated teeth and their periradicular areas (51 with and 51 without vertically fractured roots) were evaluated and compared. RESULTS: The predominant appearance of the periradicular area in the teeth with vertically fractured roots was the "halo" lesion (57%); by contrast, in the non-vertically fractured roots group, a "periapical" radiolucent lesion was most frequently found (55%). Angular bone loss (14%) and periodontal radiolucency (14%) were also typical radiolucent lesions in the vertically fractured teeth. CONCLUSIONS: "Halo" lesion, perilateral radiolucency, and angular resorption of the crestal bone, combined with diffuse or defined but not corticated borders, indicated a high probability of vertical root fracture in maxillary premolars.     

Late term complications of intruded permanent incisors: 2 case reports

This report describes 2 cases of intrusive luxation injuries of maxillary immature permanent central incisors. In both cases, intruded teeth were left for spontaneous re-eruption. During periodic follow-ups for up to 2 years the teeth did not show any sign, clinically or radiographically, of pulp necrosis with apical periodontitis. However, in the first case tenderness to percussion and periapical radiolucency developed after 2.5 years and endodontic treatment was started. In the second case, the patient returned after 2 years 9 months with complaint and periapical radiolucency was observed radiographically. Endodontic therapy was performed. These late-term complications highlight the need for regular long-term follow-up in cases of intrusive luxation in permanent teeth.     

Prognosis of luxated non-vital maxillary incisors treated with calcium hydroxide and filled with gutta-percha. A retrospective clinical study.

A material of 885 luxated, non-vital incisors was evaluated radiographically with respect to healing of periodontal tissues including inflammatory root resorption and occurrence of ankylosis and cervical root fractures. The results were assessed after completion of calcium hydroxide treatment and 4 years after filling of the root canal with gutta-percha. After treatment with calcium hydroxide, periapical healing occurred in 95% of the teeth. Four years after filling with gutta-percha, periapical healing was present in 91% of the teeth. In the remaining teeth, recurrent or persistent periapical radiolucency was more frequent in overfilled than adequately filled teeth (P = 0.0001). There was no difference between immature and mature teeth. Inflammatory root resorption healed in 192 of 197 teeth (97%); in 5 teeth it developed into ankylosis. Ankylosis occurred in 13 teeth, all of which were intruded into the alveolar bone at the time of injury. The frequency of cervical root fractures was markedly higher in immature than mature teeth (P greater than 0.0001). Among immature teeth, the frequency of fractures was dependent on the stage of root development (chi 2 = 31.6) and ranged from 77% in teeth with the least to 28% in teeth with the most developed roots. The frequency of fractures was also related to the defects after healing of inflammatory root resorption in the cervical area of the root, significant at P less than 0.0001.     

Prognosis of luxated non-vital maxillary incisors treated with calcium hydroxide and filled with gutta-percha. A retrospective clinical study

Abstract A material of 885 luxated, non-vital incisors was evaluated radiographically with respect to healing of periodontal tissues including inflammatory root resorption and occurrence of ankylosis and cervical root fractures. The results were assessed after completion of calcium hydroxide treatment and 4 years after filling of the root canal with gutta-percha. After treatment with calcium hydroxide, periapical healing occurred in 95% of the teeth. Four years after filling with gutta-percha, periapical healing was present in 91% of the teeth. In the remaining teeth, recurrent or persistent periapical radiolucency was more frequent in overfilled than adequately filled teeth (P = 0.0001). There was no difference between immature and mature teeth. Inflammatory root resorption healed in 192 of 197 teeth (97%); in 5 teeth it developed into ankylosis. Ankylosis occurred in 13 teeth, all of which were intruded into the alveolar bone at the time of injury. The frequency of cervical root fractures was markedly higher in immature than mature teeth (P>0.0001). Among immature teeth, the frequency of fractures was dependent on the stage of root development [x²= 31,6) and ranged from 77% in teeth with the least to 28% in teeth with the most developed roots. The frequency of fractures was also related to the defects after healing of inflammatory root resorption in the cervical area of the root, significant at P< 0.0001.     

Mineral trioxide aggregate as an alternative treatment for intruded permanent teeth with root resorption and incomplete apex formation

Abstract – A case of extensive crown fracture associated with intrusion of the permanent maxillary central incisors in an 8‐year‐old boy is reported. The treatment of both injured teeth included attempts of apexification and arrest of root resorption with calcium hydroxide. After 8 months of the trauma, there was no calcified barrier formation in the apex. Mineral trioxide aggregate (MTA) was then used as a filling material. At 15‐month follow up, the teeth were asymptomatic and correctly sealed, the external inflammatory root resorption had stopped, and the radiolucent image had disappeared, which meant the initial healing of the periapical lesion. MTA may be considered as an alternative option for the treatment of traumatized and immature permanent teeth.     

Rate and predictability of pulp revascularization in therapeutically reimplanted permanent incisors

Abstract The aim of the present investigation was to study the frequency of pulp revascularization in therapeutically reimplanted incisors as well; is its relationship with the following factors: width of apical foramen, duration of extra-alveolar lime, storage conditions and postoperative administration of antibiotics. Out of 72 immature teeth (width of apical foramen 1.1–5.0 mm) the pulp was revascularized in 13 (18%), while in 88 mature teeth (width of apical foramen 1.0 mm or less) no revascularization occurred. Among parameters tested statistically in immature teeth, a significantly increased frequency of revascularization (p < 0.05) was only found in teeth reimplanted within 45 minutes after avulsion, when compared with teeth reimplanted after a longer extra-alveolar time, and in mandibular incisors when compared with maxillary incisors (p < 0.01). All teeth in which revascularization did not occur exhibited a periapical radiolucency and/or external inflammatory root resorption.     

Efficacy of various eugenol and non-eugenol root canal sealers in the treatment of teeth with periapical radiolucent area--a clinical and radiological study

A clinical and radiological study was conducted to compare the efficacy of various eugenol containing Viz. Zinc oxide eugenol, CRCS and Rosen's Cement and non eugenol containing sealers and N2 on forty eight non-vital anterior teeth, with a periapical radiolucent area of 1-7mm in diameter. The patients were recalled after 30,90,150 and 210 days On radiological examination after 210 days CRCS showed maximum decrease in periapical radiolucency from 4.39 mm. to 1.80mm. The teeth treated with N2 as root canal sealer showed minimum decrease in the periapical radiolucency from 3.0 mm. to 2.15mm. On clinical examination the results were 100% successful in both the eugenol and non-eugenol groups. The radiological findings indicate that the eugenol containing are better as compared to non-eugenol containing root canal sealer. Out of eugenol containing root canal sealers CRCS showed maximum decrease in radiolucency and from non-eugenol containing group N2.     

Effect of calcium hydroxide-based materials on periapical tissue healing and orthodontic root resorption of endodontically treated teeth in dogs

Abstract – This study evaluated periapical tissue healing and orthodontic root resorption of endodontically treated teeth sealed with calcium hydroxide in dogs. The sample consisted of three contralateral pairs of maxillary incisors and two contralateral pairs of mandibular incisors in each of two dogs using a split mouth design. After biomechanical preparation of the teeth in the first group (n = 10), a Ca(OH)₂ dressing was placed for 14 days before root canal filling with Ca(OH)₂‐based sealer (Sealapex) and gutta‐percha points. In the second group (n = 10), root canals were obturated immediately after the mechanical preparation with gutta‐percha points and zinc oxide and eugenol (ZOE)‐based sealer (Endofill). After completion of endodontic treatment, the teeth were moved with an orthodontic appliance with a calibrated force of 200 g, reactivated every 21 days. After 105 days, the animals were killed and the teeth were removed upon completion of active treatment, without a period of recovery, and prepared for histomorphological analysis. All sections of each tooth were graded subjectively on a scale from one to four to obtain the average of the 16 histomorphological parameters analysed. Evaluation of the differences between the two treatment protocols was made with Mann–Whitney U‐test. It was observed that the teeth treated with Ca(OH)₂‐based materials provided better outcomes (P = 5%), with complete repair of all root resorption areas, high rate of biological closure of the main canal and apical accessory canals by newly formed cementum, less intense and extensive chronic inflammatory infiltrate, and better organization of the periodontal ligament. Under the tested conditions, Ca(OH)₂‐based materials had a favourable action on periapical tissue healing and repair of orthodontic root resorption in endodontically treated dogs’ teeth.     

Effects of intrusion combined with anterior retraction on apical root resorption

This study evaluated the influence of intrusion mechanics combined with anterior retraction on root resorption of the maxillary incisors. A sample of 56 patients was divided into two groups: group 1 comprised 28 patients (12 females and 16 males), presenting with an increased overjet and deep overbite (6.48 and 4.78 mm, respectively) treated with reverse curve of Spee intrusion mechanics and group 2 comprised 28 patients (12 females and 16 males) with an increased overjet of 5.67 mm and a normal overbite of 1.12 mm. The initial mean ages for groups 1 and 2 were 13.41 and 13.27 years, respectively. Pre- (T1) and post- (T2) treatment periapical radiographs were used to evaluate root resorption. The groups were compared using the Mann-Whitney U-test. Correlation between root resorption and tooth movement was investigated with Spearman's correlation coefficient. The subjects in group 1 had statistically greater root resorption (P < 0.05) than those in group 2. The initial overbite severity and the amount of correction had significant positive correlations with root resorption (r = 0.324 and r = 0.320, respectively). The combination of anterior retraction with intrusive mechanics causes more root resorption than anterior retraction of the maxillary incisors alone.     

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.