下颌第一磨牙远舌根的研究进展

远舌根是位于下颌恒磨牙远中舌侧的一个部分或完全独立的额外牙根,常见于下颌第一磨牙。远舌根通常细短弯曲,它的出现增大了下颌第一磨牙根管治疗的难度。充分认识和识别远舌根,对于提高下颌第一磨牙根管治疗的成功率有重要意义。近年来,随着大家对下颌第一磨牙解剖的认识日益重视,对远舌根的研究日趋深入。下面就国内外学者对于远舌根的解剖研究作一回顾。     

The Morphologic Characteristics of the Distolingual Roots of Mandibular First Molars in a Taiwanese Population

IntroductionThe prevalence of extra distolingual (DL) roots in mandibular first molars in Chinese population is about 20%. The purpose of this study was to evaluate the difference of root length and root curvatures between distobuccal (DB) and DL roots of three-rooted mandibular first molars in a Taiwanese (Chinese) population.MethodsOf the 293 extracted mandibular first molars, DL roots were present in 29 (9.9%) teeth. Excluding teeth with fractured DB or DL roots, 21 mandibular first molars were further investigated. DB and DL root lengths were measured from the lower level of furcation at the distal surface to the root apex. The curvature of the DL root was measured on mesial-distal and buccal-lingual radiographs by Schneider's technique.ResultsThe DL roots were significantly (p < 0.001) shorter than the DB roots with an average of 1.48 ± 0.81 mm. Most DL roots had a greater curvature in a buccal-lingual orientation (36.35° ± 9.38°) than a mesial-distal orientation (9.24° ± 6.10°) and 28.57% of the curved DL roots had the curvature at the apical one third (p < 0.001).ConclusionThe results of this study verified the characteristics of shorter root length and severe buccal-lingual inclination of DL roots in three-rooted mandibular first molars.     

不同投照角度X线根尖片诊断下颌第一磨牙远中舌根的临床研究

目的评价不同投照角度X线根尖片诊断下颌第一磨牙远中舌根的作用。方法选择需行根管治疗的205颗下颌第一磨牙为研究对象。术前拍X线正位根尖片及近中20°～30°偏位根尖片,对比分析是否存在远中舌根。术中根据根管的弯曲情况把远中舌根分为3类。记录下颌第一磨牙牙根和根管的数量。结果术前X线正位、近中偏位根尖片判断48颗(48/205)下颌第一磨牙存在远中舌根,临床治疗中均确定有远中舌根,其余157颗下颌第一磨牙术中均未见远中舌根。远中舌根发生率为23.41%。48颗下颌第一磨牙远中舌根中,Ⅰ类根管22颗(45.83%);Ⅱ类根管17颗(35.41%);Ⅲ类根管9颗(18.75%)。205颗下颌第一磨牙106颗(51.70%)为3根管;98颗(47.80%)为4根管;1颗(0.48%)为5根管。结论术前多角度根尖片能准确诊断下颌第一磨牙远中舌根。     

Endodontic Management of the Three-Rooted Mandibular First Permanent Molar: a Case Report

The distal root of the mandibular first permanent molar (MFPM) contains one or two canals. More rarely, the second/third distal canal is found in a separate root in a distolingual (DL) position – a radix entomolaris (RE). In Caucasians, this occurs in less than 4% of cases, but it is equally important to be aware of this possibility. Careful examination of the preoperative periapical radiographs (orthoradial and mesially angled) and inspection of the pulp chamber floor during endodontic management may indicate that this radicular variant is present. RE’s lingual inclination and buccolingual curvature must be taken into account during cleaning and shaping of the canal within this root to avoid procedural errors, such as straightening and ledging of the root canal, perforation or instrument fracture. The aim of the present paper was to discuss a case report of a young patient, referred to an endodontic office after a ledge was created by inappropriate instrumentation of a buccolingually curved RE canal.Key words: mandibular first permanent molar, root canal therapy, radix entomolaris, supernumerary root, anatomical variants     

下颌第一恒磨牙远舌根的临床分析

目的调查下颌第一恒磨牙远舌根的发生率及根管治疗情况。方法临床收集378颗下颌第一恒磨牙根管治疗的完整病例,包括病历记录和术前、术中、术后X线片,记录下颌第一恒磨牙的牙根数目、根管数目及根管治疗情况。结果在378颗下颌第一恒磨牙中,远舌根的发生率为26.98％（102/378）,男、女患者和左、右侧远舌根的发生率均无统计学差异（P>0.05）。在根管治疗中,远舌根根管器械分离、侧穿和欠填的发生率高于其他根管（P<0.05）。结论远舌根在下颌第一恒磨牙中的发生率较高,发生器械分离、根管侧穿以及欠填的比例也高于其他根管。     

Root and canal morphology of permanent mandibular molars in a Sudanese population

AIM: To investigate variations in the root canal systems of first and second permanent mandibular molar teeth in a Sudanese population using a clearing technique. METHODOLOGY: Two hundred extracted first and second permanent mandibular molars from three cities in the state of Khartoum were studied. Access cavities were prepared and pulp tissue was removed by immersion in 5% sodium hypochlorite under ultrasonication; Indian ink was then injected into the root canal systems assisted by a vacuum applied apically. The teeth were rendered clear by demineralization and immersion in methyl salicylate before evaluation. The following observations were made (i) number of roots and their morphology; (ii) number of root canals per tooth; (iii) number of root canals per root and (iv) root canal configuration. RESULTS: Overall 59% of mandibular first molars had four canals with 3% having a third distolingual root. Seventy-eight per cent of second mandibular molars had two separate flat roots, whilst 10% were C-shaped. The most common canal system configurations were type IV (73%) and type II (14%). Inter-canal communications were more common in the mesial roots. The prevalence of inter-canal communications was 65% in first molars and 49% in second molars. CONCLUSIONS: In this sample of Sudanese teeth, 59% of the mandibular first permanent molars had four root canals whilst 10% of the mandibular second molars had C-shaped roots/canals.     

Shape and number of the roots of the permanent molar teeth

One hundred ninety-eight mandibular first molars, 198 mandibular second molars, and 122 mandibular third molars, extracted from 99 Indian skulls were examined for the number of dental roots. The number of mandibular molar roots is increased by the appearance of the distolingual root, accessory lingual root, and bifurcation of the mesial root. The bifurcation of the mesial root was investigated in teeth in which it was more than 1/3 and less than 1/3 (apical bifurcation) of the root length. The following results were obtained. The numbers of the roots including apical bifurcation of the mesial root were 2, 3 and 4 in 72.7%, 26.8% and 0.5%, respectively, of the first molars; 1, 2 and 3 in 17.7%, 76.8% and 5.6%, respectively, of the second molars; and 1, 2 and 3 in 16.4%, 77.1% and 5.8%, respectively, of the third molars. The numbers of dental roots excluding apical bifurcation of the mesial root were 2 and 3 in 99.0% and 1.0%, respectively, of the first molars; 1, 2 and 3 in 17.7%, 81.8% and 0.5%, respectively, of the second molars; and 1, 2 and 3 in 16.4%, 77.1% and 5.8%, respectively, of the third molars.     

锥束CT对下颌第一磨牙远舌根发生率的研究

目的：利用锥束CT三维影像调查分析下颌第一磨牙远舌根的形态及发生率,以提高根管治疗质量。方法：至少具有一侧下颌第一磨牙的469例患者927颗下颌第一磨牙被纳入研究,采用锥束CT扫描获得患者的影像资料,利用NNT version 3．0软件三维影像重建,分析下颌第一磨牙远舌根的牙根形态及发生率。结果：119例共206颗下颌第一磨牙具有远舌根,远舌根在人群中的发生率为25．4％（男性65例,占27．2％;女性54例,占23．5％）,远舌根在所有牙齿中的发生率为22．2％（206颗／927颗）。绝大多数病例双侧同时具有远舌根（87例,占18．6％）,远舌根单侧出现32例（右侧27例,占5．8％;左侧5例,占1.1％）,远舌根在不同性别（P=0．678）,左右侧（P=0．870）之间的发生率没有显著性差异。结论：中国人下颌第一磨牙远舌根的发生率比较高,其形态复杂,在临床治疗中应仔细探查远舌根管是否存在,从而提高根管治疗的成功率。     

Prevalence of three-rooted mandibular first molars among Taiwanese individuals

The purpose of this study was to evaluate the prevalence of mandibular first molars featuring a distolingual root among a Taiwanese population. A total of 731 patients' periapical radiographs were screened and examined to obtain 166 samples for this study. The gender, symmetry, and frequencies of occurrence of three-rooted mandibular first molars were recorded. The prevalence of three-rooted mandibular first molars was 21.09%. The bilateral incidence of a symmetrical distribution was 68.57%. There was a significantly greater incidence of three-rooted teeth on the right side of the mandible than on the left, but gender did not show a significant relationship with this variant prevalence. Clinicians should be aware of the high racial prevalence of the distolingual root in mandibular first molars among the Taiwanese (Chinese) population before initiating endodontic treatment.     

Evaluation of root canal morphology of human primary molars by using CBCT and comprehensive review of the literature

Objective Knowledge of primary tooth morphology is essential for clinical dentistry, especially for root canal treatment and dental traumatology. However, this has not been well documented to date with a large sample. This study was carried out to investigate the variation in number and morphology of the root canals of the primary molars, to study the applicability of cone beam computerized tomography (CBCT) in assessing the same and to provide a comprehensive review of the literature. Materials and methods A total of 343 primary molars, without any root resorption, were divided into four main groups including the maxillary first molars, maxillary second molars, mandibular first molars and mandibular second molars. All of them were analysed in CBCT images in the axial, sagittal and coronal planes. Various parameters such as the number of roots, number of canals, the root canal type, diameter of root and root canal and root canal curvature were studied. Results Primary molars in all four groups showed variability in the number of roots and root canals. As far as length of the roots was concerned, the palatal root of the maxillary molar was found to be longest, while the distobuccal root was shortest. In mandibular molars, the mesial root was longer than the distal root. The length of distobuccal root canal of the maxillary molars and the distolingual canal of the mandibular molars was found to be shortest. The number of roots and root canals varied from two to four and three to four, respectively. The maxillary molars exhibited more one-canal than two-canal roots. Conclusion The present study provides comprehensive information to the existing literature concerning the variation in root canal morphology of the maxillary and mandibular primary molar teeth. These data may help clinicians in the root canal treatment of these teeth.     

Root and canal morphology of Thai mandibular molars

AIM: To investigate the root and canal morphology of 351 mandibular permanent molars collected from an indigenous Thai population. METHODOLOGY: The cleaned teeth were accessed, the pulp dissolved by sodium hypochlorite under ultrasonication and the pulp system injected with Indian ink. The teeth were rendered clear by demineralization and immersion in methyl salicylate. The following observations were made: (i) number of roots and their morphology; (ii) number of root canals per tooth; (iii) number of root canals per root; (iv) root canal configuration in each root using Vertucci's classification, with additional modifications; and (v) presence and location of lateral canals and intercanal communications. RESULTS: Of 118 mandibular first molars, 13% had a third disto-lingual root. In three-rooted teeth, 80% of the main distal roots and 100% of the disto-lingual roots had type 1 canal systems. Of 60 mandibular second molars, 10% had C-shaped roots, the majority of which had type 1 (33%) or type IV (33%) canal systems. Of 173 third molars, 68% had two separate roots, 20% had fused roots and 11% had a single C-shaped root; the majority had two canals (61%). CONCLUSIONS: This study suggests that Thai molars exhibit features of both Caucasian and Chinese teeth.     

Root and canal morphology of mandibular first and second molar teeth in a Jordanian population

Aim  To examine the root and canal morphology of mandibular permanent first and second molar teeth in a Jordanian population.
Methodology  A total of 685 extracted mandibular first and second permanent molar teeth were collected from dental clinics within north Jordan. The teeth were examined visually and the root number and morphology were recorded. After that, access cavities were prepared, pulp tissue dissolved by sodium hypochlorite and the root canals injected with Indian ink. Stained teeth were decalcified with 10% nitric acid, dehydrated with ascending concentrations of alcohol and rendered clear by immersion in methyl salicylate. The following observations were evaluated: (i) number of canals per root; (ii) number of root canals per tooth; (iii) canal configuration in each root; (iv) number and location of lateral canals and (v) presence of intercanal communications.
Results  Of 330 mandibular first molars, the majority had three (48%) or four (46%) canals, whilst 4% had a third disto-lingual root. Of 355 mandibular second molars, 58% had three canals, 19% two and 17% had four canals, whilst 10% had C-shaped roots. The most prevalent canal configuration in the mesial root of both first (53%) and second (40%) molars was type IV, and in distal roots was type I (54% in first and 79% in second molars).
Conclusions  Jordanian mandibular first and second molar teeth exhibit features close to the average Caucasian root and canal morphology.     

Radix entomolaris in permanent mandibular first molars: case reports and literature review

This article presents three cases involving permanent mandibular first molars with unusual root morphology. While the permanent mandibular first molar normally has two roots (one mesial and one distal), an additional root sometimes is found distolingually; this condition is known as radix entomolaris (RE). This article also reviews the literature concerning the morphology, prevalence, etiology, classification, diagnosis, and significance of RE.     

下颌第一磨牙近中根根管形态的研究

目的：评价下颌第一磨牙近中根根管形态。方法：取100个下颌第一磨牙近中根,印度墨水染色,硝酸脱钙,酒精脱水,于水杨酸甲脂透明,体式显微镜下观察。结果：Ⅰ类根管9例,Ⅱ类根管31例,Ⅲ类根管1例,Ⅳ类根管49例,Ⅴ类根管2例,Ⅵ类根管6例,无Ⅶ、Ⅷ类根管。根管侧支41例,其中75%位于根管冠1/3,21.95%位于根管中1/3,68.03%位于根管尖1/3。根管峡部58例,13.79%位于根管冠1/3,75.86%位于根管中1/3,10.34%位于根尖1/3。结论：下颌第一磨牙根管形态复杂,根管峡部多位于根管中部。     

The Radix Entomolaris and Paramolaris: A Micro–Computed Tomographic Study of 3-rooted Mandibular First Molars

Introduction

The morphology of the supernumerary third root (radix) in mandibular first molars was examined by micro–computed tomography (μCT) scanning.

Methods

Nineteen permanent mandibular first molars with radix were scanned in a μCT device to evaluate their morphology with respect to root length, root curvature direction, location of radix, apical foramen, accessory canals and apical deltas, and distance between canal orifices as well as 2- and 3-dimensional parameters of the canals (number, area, roundness, major/minor diameter, volume, surface area, and structure model index). Quantitative data were analyzed by 1-way analysis of variance and the Tukey test (α = 0.05).

Results

The mean length of the mesial, distal, and radix roots was 20.36 ± 1.73 mm, 20.0 ± 1.83 mm, and 18.09 ± 1.68 mm, respectively. The radix was located distolingually (n = 16), mesiolingually (n = 1), and distobuccally (n = 2). In a proximal view, most radix roots had a severe curvature with buccal orientation and a buccally displaced apical foramen. The spatial configuration of the canal orifices on the pulp chamber floor was mostly in a trapezoidal shape. The radix root canal orifice was usually covered by a dentinal projection. The radix differed significantly from the mesial and distal roots for all evaluated 3-dimensional parameters (P < .05). The radix canal had a more circular shape in the apical third, and the mean size of the minor diameter 1 mm short of the foramen was 0.25 ± 0.10 mm.

Conclusions

The radix root is an important and challenging anatomic variation of mandibular first molars, which usually has a severe curvature with a predominantly distolingual location, and a narrow root canal with difficult access.     

Periodontal healing after mandibular third molar surgery--A comparison of distolingual alveolectomy and tooth division techniques

The purpose of this study was to compare the periodontal healing of mandibular second molars after the removal of impacted mandibular third molars using distolingual alveolectomy and tooth division techniques. A total of 120 consecutive healthy patients who presented with bilaterally impacted mandibular third molars were included in this study. The same operator removed the impacted third molars on both sides in all patients. The third molar on one side was removed by distolingual alveolectomy using a chisel, whereas the contralateral tooth was removed by the tooth division technique using burs. Attachment level, periodontal pocket depth and bone healing distal to the mandibular second molars were assessed at 7 days, 3 months and 6 months after surgery. The results showed better periodontal healing and bone healing when distolingual alveolectomy was employed, especially in the removal of deeply impacted mandibular third molars.     

Mandibular first molar with three distal root canals

CASE REPORT: A right mandibular first molar requiring root canal treatment was found to have one mesial and two distal roots and a total of five canals. The mesial and distobuccal root had two separate canals; the distolingual root had one. This case demonstrates a rare anatomical configuration and supplements previous reports of the existence of such configurations in mandibular first molars.     

Pathfile根管预备系统在下颌第一磨牙远中舌根预备中的应用研究

目的 研究应用Pathfile根管预备系统预备下颌第一磨牙远中舌根对器械分离、根尖偏移及根充效果的影响。方法 选取2014年12月26日至2015年9月25日就诊于天津市河西口腔医院治疗诊科患者104人,共104颗具有远中舌根的下颌第一磨牙,随机分为2组,A组（试验组）采用PathFile和ProTaper联合预备,B组（对照组）采用Protaper单独预备,分别记录两组的器械分离、根尖偏移、根管恰填的个数,进行统计学分析。结果 与对照组相比,A组具有较少的器械分离率及根尖偏移率（P<0.05）,2组的根管恰填率未见统计学差异（P>0.05）。结论 联合运用PathFile和ProTaper对下颌第一磨牙远中舌根进行预备可以有效减少器械分离率及根尖偏移率,值得临床推广。     

正畸治疗中磨牙的拔除和保留（四十二）——下颌第三磨牙获得性间隙对其生长发育的意义

目的：揭示第三磨牙在牙根发育完成前受正畸治疗干预而获得充足的发育空间，其牙根生长发育的特征及意义。方法：随访21例第三磨牙牙根未发育完成前接受拔除第一或第二磨牙进行正畸治疗的青少年，调查其下颌第三磨牙牙根发育完成后的牙根融合率、根分又程度及根长，并与下颌第二磨牙对应数值进行比较。结果：下颌第三磨牙在牙根生长完成发育前获得充足的生长空间后其牙根的分叉率、分叉程度均高于下颌第二磨牙，其牙根长度与下颌第二磨牙相仿。结论：下颌第三磨牙牙根融合可能是因空间不足受挤压所致，利用第三磨牙代替第二磨牙的正畸治疗应尽量选择在第三磨牙牙根未发育完成前进行。     

Influence of several factors on the success or failure of removal of fractured instruments from the root canal

The influence of several factors on the success rate of removal procedures of fractured endodontic instruments was evaluated postoperatively. In 105 teeth with 113 fragments removal attempts were undertaken using a wide range of techniques and instruments. All cases were analyzed with special regard to the following factors: type of tooth and root canal, site of fragment in relation to root canal curvature, length of fragment, and type of fractured instrument. Success of treatment was defined as removal or complete bypassing of the fragment. Of 82 instruments in molars (maxillary: 32, mandibular: 50), 56 were removed or bypassed (max.: 26, mand.: 30). Of 16 fragments in premolars (max.: 12, mand.: 4), 8 could be removed or bypassed (max.: 6, mand.: 2). Of 14 fragments in canines and incisors (max.: 7, mand.: 7), 13 could be removed completely (max.: 6, mand.: 7). When the fragment was localized before the curvature 2 of 18 cases failed, when localized inside the curvature 13 of 31 cases failed and when localized beyond the curvature 15 of 33 cases failed. Anatomical factors favorable for removal were: straight canals, incisors and canines, localization before the curvature, length of fragment more than 5 mm, localization in the coronal or mesial third of the root canal, reamer or lentulo spirales. In molars removal procedures were most successful in the palatal canals of maxillary molars.