Evaluation of Root Canal Configuration of Maxillary Molars in a Brazilian Population Using Cone-beam Computed Tomographic Imaging: An In Vivo Study

Introduction

The aim of this study was to analyze and characterize root canal morphology of maxillary molars of the Brazilian population using cone-beam computed tomographic (CBCT) imaging.

Methods

Patients referred for a CBCT radiographic examination for accurate diagnosis and treatment planning were enrolled in the study. A total of 620 healthy, untreated, fully developed maxillary first and second molars were included (314 first molars and 306 second molars). The following observations were recorded: (1) number of roots and their morphology, (2) number of canals per root, (3) fused roots, and (4) primary variations in the morphology of the root canal systems.

Results

First and second molars showed a higher prevalence of 3 separate roots, mesiobuccal, distobuccal, and palatal, with 1 canal in each root (52.87% and 45.09%, respectively). Two canals in the mesiobuccal roots represented 42.63% of teeth, whereas mesiobuccal roots of second molars presented 2 canals in 34.32%. The most common anatomic variation in the maxillary first molar was related to the root canal configuration of the mesiobuccal root, whereas the root canal system of the maxillary second molar teeth showed more anatomic variables.

Conclusions

Mesiobuccal roots of maxillary molar teeth had more variation in their canal system than the distobuccal or palatal roots. The root canal configuration of the maxillary second molars was more variable than the first molars in a Brazilian population. CBCT imaging is a clinically useful tool for endodontic diagnosis and treatment planning.     

上颌第一、第二恒磨牙牙根和根管系统的锥形束CT研究

目的：运用锥形束CT（CBCT）观察中国人群双侧上颌第一、第二磨牙的牙根和根管系统的解剖形态,为临床根管治疗提供依据。方法：选择200名患者的双侧上颌第一、第二恒磨牙（上颌第一恒磨牙354颗、上颌第二恒磨牙360颗）的CBCT扫描数据,使用NNT软件分析上颌第一、第二恒磨牙的牙根数、根管数、根管分型以及双侧对称情况。结果：上颌第一、第二磨牙主要为三根（99.44%和84.44%）。上颌第二磨牙的单根和双根较多见（15.28%）,其根管系统形态复杂,在根尖区有融合趋势。上颌第一磨牙的根管系统主要为3根四根管（78.97%）。上颌第二磨牙的三根管和四根管发现率接近（分别为47.37%和51.64%）。上颌第一磨牙的近颊根管系统主要根管分型为：Ⅳ型（57.79%）、Ⅱ型（19.83%）和Ⅰ型（15.58%）。上颌第二磨牙的近颊根管系统主要根管分型为：Ⅰ型（48.14%）、Ⅳ型（30.43%）和Ⅱ型（17.39%）。上颌第一、第二磨牙的远颊根和腭根主要为单根单根管,存在少量和罕见的变异。上颌第一、第二磨牙近颊根的根管数目和根管分型左右对称。结论：上颌第一磨牙近颊根管系统变异普遍存在,MB2根管为其主要的变异形式。上颌第二磨牙牙根数目和根管形态变异类型多,单根牙和双根牙的根管走向复杂多变。CBCT可以为识别根管形态提供准确依据。     

Analisi della morfologia radicolare e canalare di molari superiori ed inferiori in una popolazione Caucasica: studio in vivo alla CBCT

AimTo investigate the root and canal morphology of maxillary and mandibular permanent molar teeth in a Caucasian population by using Cone Beam Computed Tomography (CBCT).MethodsA total of 596 permanent molars were included. The number of roots, the number of canals per root and the root canal configurations according to the method of Vertucci were recorded.ResultsAlmost all of maxillary first molars (95.7%) had three separate roots; however, 40.3% of mesiobuccal roots had two canals (MB2). Of 157 maxillary second molars, 88.5% had three roots. Among the mesiobuccal roots, 15.1% had two canals. The majority of mandibular molars (100% of first molars, 89.4% of second molars) had two separate roots. Most distal roots had a simple type I configuration, whereas mesial roots had more complex canal systems, with more than one canal.ConclusionsCBCT is an efficient method of studying root canal systems.     

A study of the distobuccal root canal orifice of the maxillary second molars in Chinese individuals evaluated by cone-beam computed tomography

As is commonly understood, the root canal morphology of the maxillary molars is usually complex and variable. It is sometimes difficult to detect the distobuccal root canal orifice of a maxillary second molar with root canal treatment. No literature related to the distobuccal root canals of the maxillary second molars has been published.

Objective

To investigate the position of the distobuccal root canal orifice of the maxillary second molars in a Chinese population using cone-beam computed tomography (CBCT).

Material and methods

In total, 816 maxillary second molars from 408 patients were selected from a Chinese population and scanned using CBCT. The following information was recorded: (1) the number of root canals per tooth, (2) the distance between the mesiobuccal and distobuccal root canal orifice (DM), (3) the distance between the palatal and distobuccal root canal orifice (DP), (4) the angle formed by the mesiobuccal, distobuccal and palatal root canal orifices (∠ PDM). DM, DP and ∠ PDM of the teeth with three or four root canals were analyzed and evaluated.

Results

In total, 763 (93.51%) of 816 maxillary second molars had three or four root canals. The distance between the mesiobuccal and distobuccal orifice was 0.7 to 4.8 mm. 621 (81.39%) of 763 teeth were distributed within 1.5-3.0 mm. The distance between the palatal and distobuccal orifice ranged from 0.8 mm to 6.7 mm; 585 (76.67%) and were distributed within 3.0-5.0 mm. The angle (∠ PDM) ranged from 69. 4º to 174.7º in 708 samples (92.80%), the angle ranged from 90º to 140º.

Conclusions

The position of the distobuccal root canal orifice of the maxillary second molars with 3 or 4 root canals in a Chinese population was complex and variable. Clinicians should have a thorough knowledge of the anatomy of the maxillary second molars.     

Root and canal morphology of Thai maxillary molars

AIM: To investigate the root and canal morphology of 268 maxillary 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 root; (iii) root-canal configuration in each root using Vertucci's classification with additional modifications; and (iv) presence and location of lateral canals and intercanal communications. RESULTS: All the maxillary first and second molars had three separate roots. Only, half (51%) of the maxillary third molars had three separate roots; the other half had fused or conical roots. The majority of the distobuccal (98.1-100%) and palatal (100%) roots had type I canals. Over half of the mesiobuccal roots of first (65%) and second (55%) molars had two canals. The most common (44.2%) canal configuration in mesiobuccal roots of first molars was type IV (two canals, two foramina). A variety of canal types were found in the mesiobuccal roots of second molars. Maxillary third molars showed the greatest diversity of canal morphology. There was an increase in the prevalence of lateral canals towards the apical part of the roots and intercanal communications were present in 16% of each of first, second and third Thai maxillary molars. CONCLUSIONS: The mesiobuccal roots of Thai maxillary molars possessed a variety of canal system types. Over 50% of the first molars had a second mesiobuccal canal. The palatal and distobuccal canals mainly had type I canals. Only, a small proportion (7.3-13.3%) of the roots exhibited lateral canals which were the most common in the apical third     

Root and root canal morphology of permanent mandibular first and second molars in a Kuwaiti population: A retrospective cone-beam computed tomography study

AimEndodontic diseases typically affect the mandibular molars. Understanding the complex morphology of the root canal system and its variations is necessary for successful endodontic treatment. The aim of this study was to evaluate the morphology of roots and root canals of mandibular first and second permanent molar teeth in a Kuwaiti population using cone-beam computed tomography (CBCT).Materials and methodsCBCT images of 651 mandibular first and second molar teeth were obtained from specialist government dental centers. The age, sex, root canal configuration, and number and type of roots were recorded. The data were statistically analyzed.ResultsThe most common canal configuration in the mandibular first and second molars was type II (65.6% and 54.4%, respectively), with no significant difference seen between the sexes (p = 0.234). The canal configuration was significantly different between the mandibular first and second molars (p < 0.001). Most teeth had two roots (94.5%); split roots were common (92.6%) and the number thereof varied significantly. Radicular grooves were most common on the lingual side (4.9%). C-shaped canals were present in 43 (6.60%) teeth. Additionally, one tooth had a confluent middle mesial canal and nine (1.4%) had radix entomolaris.ConclusionMandibular molars in our Kuwaiti population typically had two split roots with type II and IV canal configurations. The prevalence rates of C-shaped canals, middle mesial canals, and radix entomolaris were remarkably low.     

Study of root canal accessibility in human primary molars

The aim of the present study was to provide a general scheme for pulpectomy of primary molars that may be useful for decision-making about negotiation of root canals and selection of appropriate instruments. A total of 160 vital primary molars in 85 patients (40 males, 45 females) aged 4-6 years were selected. After taking primary radiographs, local anesthesia was induced, and the teeth were isolated using a rubber dam. Canal accessibility index (CAI) and tooth accessibility index (TAI) were calculated according to initial file size. Mandibular first molars had either three canals (79.2%) or four canals (20.8%), and all second molars had four canals. Maxillary first molars had three canals and second molars had either three canals (70.9%) or four canals (29.1%). Lower accessibility of the mandibular first molar distobuccal root accounted for the lower accessibility of these teeth in comparison with mandibular second molars. While three-canal maxillary second molars were more accessible due to the lower accessibility of the distobuccal canal of the maxillary first molar, poor accessibility of the distal canal in four-canal second molars was responsible for the difficult accessibility of these teeth. In conclusion, it seems that the accessibility of a single canal in each tooth determines the difficulty of accessibility for any given tooth. Moreover, while primary second molars are more accessible than first molars, all of them are negotiable.     

A cone-beam computed tomography study of root canal morphology of maxillary and mandibular premolars in a Turkish population

Aim. The aim of this study was to evaluate the root canal number and configuration of maxillary and mandibular premolar teeth by gender, intervals for decades, tooth position and unilateral or bilateral occurrence in a Turkish population using Cone Beam Computed Tomography(CBCT) scanning. Methodology. CBCT images of 5496 maxillary and mandibular premolars from 849 patients were evaluated. The following was evaluated in all the images: numbers of roots and root canals, the morphology of the root canal configuration according to the Vertucci classification, male–female differences in the tooth position and male–female differences in unilateral or bilateral occurrence. The reliability data were analyzed with a chi-square test. Results. The most prevalent root canal frequency was the two canals (86.2%) and type IV (76.9%) configuration for maxillary first premolar, one canal (59.7%) and type I (54.5%) canal configuration for second premolar. The incidence of one canal was higher in females and the occurrence of two or three canals was more common in males. The incidence of one canal was higher on the left side of maxillary premolars and the incidence of two canals was higher on the right side. Most mandibular first (93.5%) and second (98.5%) premolars had one canal. In general, females had one root canal of the mandibular premolar, whereas males had two or three canals. The type I configuration was most common and the incidence was higher on the right side. There were some differences found in the frequency distribution of the number of root canals and configuration of maxillary and mandibular premolar teeth according to intervals for decades. Conclusion. CBCT scanning provides comprehensive information about the root canal morphology of maxillary and mandibular premolar teeth. These data may help clinicians in root canal treatment of premolar teeth.     

新疆地区人群上颌第二磨牙牙根和根管形态的CBCT研究

目的 采用锥形束CT研究新疆地区人群上颌第二磨牙的牙根和根管形态，为本地区口腔临床诊疗提供参考依据。方法 对纳入研究的539例新疆地区人群的上颌第二磨牙，利用CBCT对其牙根形态、数目，根管形态、数目和弯曲度，牙冠颊舌径和近远中径以及对称性进行观察、分析和统计。结果 在1017颗上颌第二磨牙中，三根牙的检出率最高为85.2%，四根牙检出率最低为3.2%，不同牙位和性别在牙根形态上的分布存在统计学差异；MB2的检出率与年龄无统计学差异；56岁及以上年龄组的四根牙检出率最高。颊舌径、近远中径的平均测量值越大，其对应的根管数目越多。上颌第二磨牙的牙根数目和形态对称、根管形态及四种特征均对称方面较高，上颌第二磨牙近颊根管和远颊根管68%为重度弯曲，弯曲位于根中1/3较多。结论 新疆地区人群上颌第二磨牙以三根牙为主，对称率较高，弯曲程度大，但存在一些牙根和根管的变异，临床上可以运用CBCT来指导诊疗。     

牙科数字成像系统、锥形束CT及透明牙对离体第一恒磨牙根管系统诊断价值的对比性研究

目的 对比分析牙科数字成像系统（RVG）、锥形束CT（CBCT)及透明牙3种检查方法在诊断离体第一磨牙根管系统的价值,分析第一磨牙根管影像解剖学与根管解剖学的对应关系,为第一磨牙根管治疗提供影像解剖依据。方法 拍摄269颗离体第一磨牙颊舌向、近远中向RVG和CBCT后,再制作根管染色透明牙,应用RVG、CBCT和透明牙对各牙根中上2/3、根尖1/3区根管系统和管间交通支进行分类统计,以评估CBCT在根管诊断中的应用价值。结果 CBCT对第一磨牙主根管中上2/3区的显示率达96.55%;CBCT、透明牙对第一磨牙根尖1/3区根管系统的显示差异有统计学意义（P<0.05）。上、下颌第一磨牙近中根变异较大,双或多根管与管间交通支发生率均较高。结论CBCT与透明牙在显示第一磨牙主根管系统（牙根中上2/3区）方面基本等效;在根尖1/3区透明牙对细小分歧根管的显示明显优于CBCT;RVG对多根管牙根、根尖细小分歧根管的显示明显受限;上、下颌第一磨牙近中根双或多根管与管间交通支发生率均较高。CBCT对牙根、根管的显示具有清晰直观、准确快捷的优点,是目前无创诊断根管疾病最可靠方法。     

上颌第一磨牙根管系统的研究

目的 观察上颌第一磨牙的根管系统。方法 制备50个上颌第一磨牙透明牙标本,显露根管系统的空间构型,在体视显微镜下观察并记录根管系统的形态,结合应用加以统计。结果 ①上颌第一磨牙近中颊根单根管率为66%,其中Ⅰ型占38%,双根管率为34%,远中颊根Ⅰ型占74%,腭根Ⅰ型占94%。②根管侧支、根尖分歧、根尖分叉多见于近颊根,在近颊根的发生率为40%, 远颊根的发生率为24%,腭根的发生率为6%,发生部位多见于根尖1/3。结论 上颌第一磨牙近颊根的根管系统最为复杂,根管变异较远颊根多,腭根变异最少。     

The root and root canal anatomy of maxillary molars in a Chinese population

Abstract The purpose of this investigation was to study the prevalence of fused roots, C-shaped roots, C-shaped root canal orifices and C-shaped root canals in the maxillary molars of a Chinese population. A total of 305 first molars and 309 second molars were collected in Taiwan. The teeth were demineralized and placed in methyl salicylate to make them transparent. Root fusion was examined and the pulp chamber floor was checked for C-shaped orifices. Chinese ink was then injected into the root canal system to demonstrate possible C-shaped canals. The maxillary first molars had the palatal root fused with the mesiobuccal root in 0.3% of the cases, and with the distobuccal root in 2.0%. Teeth with C-shaped roots existed in only 0.3% of maxillary first molars, while 6.2% of the maxillary first molars and 40.1% of the maxillary second molars had fused roots. The maxillary second molars had the palatal root fused with the mesiobuccal root in 18.1% and with the distobuccal root in 2.6%; the palatal root was fused with the mesiobuccal and distobuccal root in 8.1% of the material. The maxillary second molars had a C-shaped root in 4.5% and C-shaped root canal orifices with C-shaped root canals in 4.9% of the cases. Fused roots or incompletely separated roots are common in the maxillary second molars amongst Chinese people, while C-shaped roots and root canals in maxillary molars are not frequently seen.     

Analisi alla Cone Beam Computed Tomography della simmetria anatomica in molari superiori ed inferiori

AimTo analyze the symmetry in root canal configurations in the maxillary and mandibular permanent molar teeth of a Caucasian population using Cone Beam Computed Tomography (CBCT).ResultsOf 45 patients who had both maxillary first molars, 32 (71.1%) had perfect symmetry in the root and canal morphology of homonym teeth on the opposite side. As regards the maxillary second molars, the symmetry was observed in 43 patients (79.6%) of 54. Of 34 patients who had both mandibular first molars, 24 (70.6%) showed a perfect symmetry in the root and canal morphology of homonym teeth on the opposite side. As regards the mandibular second molars, the symmetry was observed in 47 patients (81%) of 58.ConclusionsCBCT is an exciting and clinically useful tool in studying root canal morphology and so the symmetry between homonym teeth.     

Use of cone-beam computed tomography to evaluate root and canal morphology of mandibular first and second molars in Turkish individuals

Objective: The aim of this study was to investigate the root and canal morphology of mandibular first and second molars in a Turkish population by using cone beam computed tomography (CBCT). Study design: CBCT images of mandibular first (n = 823) and second molar (n = 925) teeth from 605 Turkish patients were analyzed. The root canal configurations were classified according to the method of Vertucci. Results: The majority of mandibular molars (95.8% of first molars, 85.4% of second molars) had two separate roots; however, three roots were identified in 2.06% of first molars and 3.45% of second molars. C-shaped canals occurred 0.85% of first molars and 4.1% of second molars. Three canals were found in 79.9% of first molars and 72.8% of second molars. Most distal roots had a simple type I configuration, whereas mesial roots had more complex canal systems, with more than one canal. The most common root morphology of first and second molars is the two rooted morphology with three canals. Both the mesial and distal roots showed wide variations in canal anatomy with type IV and type I canal configuration predominating in the mesial and distal roots, respectively. Conclusion: Vertucci type I and IV canal configurations were the most prevalent in the distal and mesial roots, respectively, of both the mandibular first and second permanent molar teeth. Key words:Cone-beam CT, Turkish, mandibular molars, root and canal morphology.     

Symmetry of Root and Root Canal Morphology of Maxillary and Mandibular Molars in a White Population: A Cone-beam Computed Tomography Study In Vivo

Introduction

The aim of the present study was to use cone-beam computed tomography (CBCT) to analyze root canal anatomy and symmetry of maxillary and mandibular first and second molar teeth of a white population.

Methods

A total of 201 patients who required CBCT examinations as part of their dental diagnosis and treatment were enrolled in the present study. Overall, 596 healthy, untreated, well-developed maxillary and mandibular molar teeth (161 maxillary first molars, 157 maxillary second molars, 117 mandibular first molars, and 161 mandibular second molars) were examined by CBCT to establish the symmetry in root and canal anatomy between right and left sides in the same patient by evaluating the number of roots and root canals and the root canal configuration.

Results

Three separate roots with 3 separate canals was the normal anatomy of maxillary first and second molars. Most mandibular first and second molars had 2 separate roots, and the majority had 3 canals. In the present study, first molars, both maxillary and mandibular, exhibited greater asymmetry than the second molars. Maxillary first molars were found to be symmetrical in 71.1% of patients, whereas maxillary second molars were symmetrical in 79.6%. The remaining 28.9% and 20.4% of patients, respectively, showed asymmetry. Around 30% of the mandibular first molars and 20% of the mandibular second molars showed asymmetry.

Conclusions

The results of the present study reported a percentage of symmetry that varied from 70%–81%. These variations in symmetry should be taken in high consideration when treating 2 opposite molars in the same patient, because their anatomy may be different in up to 30% of the cases.     

Morphology of Mandibular First Molars Analyzed by Cone-beam Computed Tomography in a Korean Population: Variations in the Number of Roots and Canals

Introduction

The aim of this study was to determine the root and canal morphology of the mandibular first molars in a Korean population of Mongolian origin by retrospective analysis of a large number of cone-beam computed tomography (CBCT) images.

Methods

A total of 976 subjects with bilateral mandibular first molars were examined by using in vivo CBCT methods. The number and configuration of roots, the number of root canals, and the canal configuration based on Vertucci's classification were determined.

Results

Overall, 25.82% of examined molars had 3 roots, 73.51% had 2 roots, and 0.67% had 1 root. The incidence of fourth canal was 50.36%. A right-sided predominance was noted for extra distal roots (P < .001), whereas a left-sided predominance was observed for extra distal canals (P < .001). No significant sex-related differences were shown for their prevalence. The bilateral prevalence rate was 69.13% for extra distal roots and 78.08% for extra distolingual (DL) canals. In the mesial roots, type IV canal was the most frequent (76.86% for 2-rooted molars and 72.96% for 3-rooted molars). In the distal roots, type l was the most common (66.62% for 2-rooted molars and 99.40%–100% for 3-rooted molars). The incidence of 2 canals in distobuccal roots, first reported in this study, was 0.15%.

Conclusions

Among mandibular first molars, there is a high prevalence of a separate DL root and/or a separate DL canal, and such molars commonly have 4 canals in the Korean population. CBCT is a useful tool for determining root and canal morphology.     

Root Canal Morphology of Permanent Maxillary Teeth in the Han Nationality in Chinese Guanzhong Area: A New Modified Root Canal Staining Technique

IntroductionThe purpose of this study was to investigate the canal morphology of 504 maxillary permanent teeth of subjects of Han nationality in Chinese Guanzhong area.MethodsMaxillary permanent teeth were randomly collected in Guanzhong area. After regular preparation, the teeth were immersed into ink without preparing access cavities and then put into hyperbaric oxygen chamber (0.6 Mpa) for 2 hours to let the ink penetrate into root canal from apical foramen, apical deltas and foramen of lateral canals under stable positive pressure. After demineralization and clearing, the following observations were made: (1) number of root canals, (2) root canal configuration by using Vertucci's classification, (3) presence of lateral canals, and (4) frequency of apical deltas.ResultsAll the teeth were well-stained, and the fine details were well-revealed. Apical deltas (12.2%–83.3%) and lateral canals (13.7%–68.8%) could be frequently found in all types of maxillary teeth. Most of central incisors (95.8%), lateral incisors (91.4%), and canines (75.4%) displayed type I canal configuration, whereas most of first premolars (87.3%) and second premolars (72.3%) possessed 2 canals with type II, IV, or VI canal configuration. The majority of distobuccal roots and palatal roots of first molars (88.9%, 97.8%), second molars (92.0%, 94.0%), and third molars (87.5%, 91.6%) possessed type I canal configuration. The prevalence of mesiobuccal roots with type I configuration was 66.7% in maxillary first molars, 82% in second molars, and 62.5% in third molars.ConclusionsThe modified technique of canal staining can effectively reveal detailed root canal system. The canal configuration of maxillary teeth in subjects of Han nationality in Chinese Guanzhong area is consistent with previous reports in other races.     

上颌第三磨牙根管形态的CBCT研究

目的：应用锥形束CT（cone?beam computed tomography ,CBCT）技术研究上颌第三磨牙的根管形态,为临床治疗提供解剖学依据。方法随机调取397颗上颌第三磨牙的CBCT资料,分析上颌第三磨牙的牙根数目、根管数目、根管分类等。结果397颗上颌第三磨牙中,三根牙最多,占43.07%;融合根牙次之,占40.30%。分析根管数目显示,三根管最多,占47.86%;单根管次之,占28.21%。根据Vertucci根管分类,89.6%的牙根以Ⅰ型根管为主,但仍会出现根管治疗时较难操作的Ⅱ型、Ⅲ型、Ⅴ型、其他型等根管。结论上颌第三磨牙根管解剖形态多样,根管系统复杂、变异大。     

Root and canal morphology of the mesiobuccal and distal roots of permanent first molars in a Kuwait population--a clinical study

Aim To identify the number of roots and canal configurations in permanent first molars of the indigenous Kuwaiti sub‐population and compare them against a similar group of non‐Kuwaiti population in different age groups and gender, and to determine the frequency of a second canal in the mesiobuccal root of maxillary first molars and distal root of mandibular first molars that could be located and treated in routine practice without using magnification or special lighting conditions. Methodology A total of 220 permanent first molar teeth of patients scheduled for root canal treatment over a period of 1 year were included. Patients were identified and grouped according to their nationality as Kuwaiti and non‐Kuwaiti (which included Filipinos, Indonesian Indians, Srilankans, Egyptians, Saudi Arabians and Syrians). In both nationality groups, patients were successively distributed into four groups based on their age. The first age group included patients below 20 years, the second 21–30 years, the third 31–40 years and the fourth were over 40 years. The first three groups comprised of 15 male and 15 female patients whilst the fourth group had 10 patients of each gender. Teeth with open apices, resorptions and calcification were excluded from the study. The teeth included were both clinically and radiographically examined for number of roots, the canal configuration and the presence of the additional mesiobuccal and distal canals and recorded. The simplified classification of canal configurations proposed by Weine was utilized. Results The incidence of a second canal in the mesiobuccal (MB) root of maxillary first molars and the distal root of mandibular first molars was not influenced significantly by nationality and gender. All the 110 maxillary first molars treated had three roots; 58% of MB root had one canal and 42% had two canals. The majority of the mesial roots had Weine type II canal configuration when the second mesiobuccal canal was present. All distobuccal and palatal roots had a single or type I canal configuration. Of the 110 mandibular first molars that were treated, 96% had two roots and 4% had three roots. When present, the third root was located either buccal or lingual to the main distal root. Overall 51% of the single distal roots had one canal whilst 49% had two canals. The mesial root frequently had a Weine type II canal configuration as did the distal root when a second canal was present. Pearson’s correlation analysis of both molars revealed a significant (P < 0.05) negative correlation (r = ?0.274, r = ?0.144) between age and number of canals as well as the type of canal. Conclusions The incidence of a second canal in distal roots of permanent mandibular first molars was 49% in the Kuwaiti population and this was similar to other Asian ethnic populations. Adopting modified access and troughing procedures revealed a 42% frequency of MB2 canals in maxillary first molars. The incidence of a second canal in both mesiobuccal roots of maxillary molars and distal roots of mandibular molars decreased significantly with age; no differences were noticed amongst the nationalities and gender studied. The possibility of extra roots should be anticipated in mandibular molars.     

下颌第二恒磨牙牙根及根管形态的锥形束CT研究

目的 使用锥形束CT扫描评估下颌第二恒磨牙牙根和根管解剖形态.方法 收集354例患者双侧下颌第二恒磨牙的锥形束CT图像,统计下颌第二恒磨牙牙根数目、根管数目和构型,以及C形根管的发生率.结果 下颌第二恒磨牙以双根最多,发生率为57.34%,C形根的发生率为38.28%;双根者近中根多为2-2型(80.54%),远中根多为1-1型(96.06%);C形根管的发生率为25.99%,左、右下颌的发生率没有统计学差异(P>0.05).结论 下颌第二恒磨牙牙根和根管解剖形态复杂多样,锥形束CT能为根管治疗提供参考.