A preliminary in vitro study of the incidence and position of the root canal isthmus in maxillary and mandibular first molars

AIM: To investigate in vitro the incidence and position of the root canal isthmus in extracted mesiobuccal roots of maxillary and mesial roots of mandibular first molars. METHODOLOGY: Fifty maxillary and 50 mandibular molars were included in the study. The mesiobuccal roots of maxillary molars and the mesial roots of mandibular molars were sectioned from their crowns in the furcation region and embedded in clear resin. Transverse serial 1-mm-thick sections from the apical 6 mm were prepared. The apical side of each section was stained with India ink and observed through a light microscope. The sample images were saved to disk using a digital camera and the root canals in terms of the number present and the incidence and classification of isthmuses. RESULTS: In the mesiobuccal root of the maxillary first molars, 70% had one canal, whereas 29.5% had two canals. In the mesial root of mandibular molars, 41% had one canal, whereas 59% had two canals. In some sections, more than two canals were found close to the apical foramen. The isthmus incidence was greatest 3-5 mm from the apex. In teeth having two canals, a complete or partial isthmus was frequently observed in the sections between 3 and 4 mm from the apex. Of the isthmuses present, 22% were complete and 37% partial in mandibular molars and 17.3% were complete and 11.7% partial in maxillary molars. CONCLUSIONS: The incidence of isthmus in the mesiobuccal root of the maxillary first molars and in the mesial root of the mandibular first molars was high, particularly in sections 3-5 mm from the apex. Cleaning the isthmus is a major challenge during root canal treatment.     

人下颌恒切牙管间峡区解剖的显微CT研究

目的研究人离体下颌恒切牙管间峡区的解剖学特点。方法选择离体下颌恒切牙拍摄近远中向X线片,选出双根管牙33颗,对距根尖6 mm以内的牙根组织进行显微CT扫描。扫描层厚20 μm,每颗牙齿获得扫描截面300个。通过三维重建观察牙根管间峡区的解剖形态。记录距根尖1、2、3、4、5、6 mm处各截面根管数目及管间峡区的出现情况,并测量根管壁的最小厚度。结果所有双根管下颌恒切牙都存在管间峡区,完全峡区占49.7%,部分峡区占4.5%。距根尖6 mm内各截面管间峡区的出现率为10.0%~85.5%,卡方检验显示距根尖1~6 mm处管间峡区出现率的差异有统计学意义（P=0.001）。距根尖3~6 mm处管间峡区出现率较高,以5 mm处最高,为85.5%。距根尖6 mm以内的根管壁最小厚度均小于0.5 mm。结论下颌恒切牙管间峡区的出现率较高,根管壁最小厚度位于峡部,在临床进行根管治疗和牙髓外科手术时应引起重视。     

成人下颌第一磨牙管间峡区的显微CT观察

目的 研究离体下颌第一磨牙近、远中根的管间峡区出现率及形态,为治疗管间峡区、提高根管治疗成功率提供解剖学依据.方法 收集5家省部级医院及1所解剖教研室的离体下颌第一磨牙36颗,经显微CT扫描及计算机三维重建后,以30 μm层厚分别获取近、远中根根尖6 mm段的横截面图像,记录各截面的根管数目及管间峡区出现情况,并对管间峡区形态进行观察.结果 下颌第一磨牙近中根的管间峡区出现率明显高于远中根,距根尖4～6 mm水平处管问峡区出现率较高,近中根为49.5%～66.1%,远中根为17.3%～17.8%,卡方检验显示近(远)中根根尖6 mm各水平管间峡区出现率的差异具有统计学意义(P＜0.01).结论 下颌第一磨牙近中根管间峡区出现率高,提示临床医师在牙髓外科手术中应有意识地探查管间峡区,降低管间峡区遗漏率,以提高牙髓外科手术的远期疗效.     

Frequency and type of canal isthmuses in first molars detected by endoscopic inspection during periradicular surgery

AIM: To analyse the occurrence of canal isthmuses in molars following root-end resection. METHODOLOGY: The material consisted of 56 mandibular and 32 maxillary first molars subjected to periradicular surgery. Based on radiographic, clinical, as well as intraoperative status, only roots with associated pathological lesions were treated. In total, 124 roots were resected (80 mandibular and 44 maxillary molar roots). The cut root faces were inspected with a rigid endoscope following apical root-end resection. The number of canals as well as the presence and type of canal isthmuses were recorded. RESULTS: In maxillary first molars, 76% of resected mesio-buccal roots had two canals and an isthmus, 10% had two canals but no isthmus, and 14% had a single canal. All disto-buccal and palatal roots had one canal. In mandibular first molars, 83% of mesial roots had two canals with an isthmus. In 11%, two canals but no isthmus were present, and 6% demonstrated a single canal. Sixty-four per cent of distal roots had a single canal and 36% had two canals with an isthmus. CONCLUSIONS: This clinical study during periradicular surgery and intraoperative endoscopic examination of first permanent molars found a high frequency of canal isthmuses at the resection level. Endoscopic inspection also demonstrated that none of the isthmuses were filled, emphasizing the difficulty of orthograde instrumentation and root filling of canal isthmuses.     

Apical anatomy in mesial and mesiobuccal roots of permanent first molars

The purpose of this in vitro study was to investigate the canal configuration types, and the prevalence and location of anatomical variations in the mesiobuccal (MB) and mesial roots of permanent maxillary and mandibular first molars after instrumentation. The number and the type of canals were determined before instrumentation using conventional methods. All root canals from the 47 MB roots and 42 mesial roots were then instrumented to size #30 with ProFile .04 taper rotary instruments in a crown-down method and then filled with a single gutta-percha cone and sealer. Transverse 1 mm-thick cross-sections at 2, 3, 4, and 5 mm from the apex were obtained, stained and examined using a stereomicroscope. The canal configuration types and the prevalence and location of isthmi and accessory canals in roots with two canals were evaluated. The prevalence of two canals was 80.8% in the maxillary MB roots and 95.2% in the mandibular mesial roots. There were six types of canal configurations in the instrumented root apices. The prevalence of anatomical variations was highest at the apical 4 mm level, and was more frequent in mandibular first molars, and in roots with Weine type III canal. chi test showed that the prevalence of the anatomical variations was statistically higher in the maxillary MB roots with Weine type III canals than in those with Weine type II canals (p < 0.05). Different canal configurations were often found at different levels in the same root. The results indicate that anatomical variations persist following instrumentation of roots with two canals in first molars. These anatomical variations should be considered during surgical or nonsurgical endodontic procedures of the permanent first molars.     

Comparison of isthmus detection methods in the apical third of mesial roots of maxillary and mandibular first molars: macroscopic observation versus operating microscope

The aims of this study were to assess the presence and the frequency of isthmuses in the mesial roots of the maxillary and mandibular first molars (at two resection levels from the apex), and to compare the findings obtained by macroscopic observation (MO) and operating microscope (OM). Forty maxillary and 40 mandibular mesial roots were observed at 3 and 5 mm from the apex initially macroscopically and then with the use of an OM. The presence of an isthmus and the number of root canals detected were recorded. Data were analyzed statistically by Fisher's exact test for isthmus evaluation and Wilcoxon signed rank-test for number of root canals at a confidence interval of 95%. Comparison between MO and OM regarding the number of roots with isthmuses provided the following results: Mandibular group: At 3 mm level: MO 19 ?s. OM 27; at 5 mm level: MO 31 ?s. OM 32. Maxillary group: At 3 mm level: MO 9 ?s. OM 14; at 5 mm level: MO 19 ?s. OM 21. Significant differences (p<0.05) were found concerning the accuracy of the isthmus detection methods at both resection levels (3 and 5 mm) and both types of roots, as well as for the number of the canals inspected under the OM between the two resection levels of the mesial roots of the maxillary first molars. Under the tested conditions, OM increased the diagnostic accuracy of isthmus detection at both resection levels and root types.     

Investigation of the root canal configuration of mandibular first molars in a Taiwan Chinese population

Aim  To investigate the root form and canal morphology of mandibular first molar teeth in a Taiwan Chinese population.
Methodology  A total of 183 mandibular first molars were collected and examined visually through a dissecting microscope after rendering the teeth transparent. The number of roots, number of canals and canal configuration were recorded. The root canal morphology was categorized and compared according to Vertucci (1984).
Results  Overall 46% of the mandibular first molars had four canals and 20% had extra-distal roots (distolingual root). In addition, 97% of the specimens had two mesial canals and 46% had two distal canals. In total, 68% of teeth with two mesial canals had two separated apical foramina, and 33% of teeth with two distal canals had two apical foramina. The most common canal configurations (Vertucci, 1984) of mesial roots were type 4 (46%) and type 2 (23%). Type 1 was encountered in 54% of the distal roots.
Conclusions  The frequency of the extra-distal root on the mandibular first molar was 20%, and the incidence of three canals (Vertucci's type 8 classification) with separate apical foramina at the apex of the mesial root was 6%. The three-rooted variation of the mandibular first molar appears to be a genetic characteristic of an Asiatic racial background.     

In vivo debridement efficacy of ultrasonic irrigation following hand-rotary instrumentation in human mandibular molars

This study histologically compared the in vivo debridement efficacy of hand/rotary canal preparation versus a hand/rotary/ultrasound technique in mesial root canals of vital mandibular molars. Group 1 consisted of 16 teeth prepared with a hand/rotary technique whereas group 2 consisted of 15 teeth prepared in similar fashion but followed by 1 min of ultrasonic irrigation, per canal, utilizing an ultrasonic needle in a MiniEndo unit. Five uninstrumented mandibular molars served as histologic controls. After extraction and histologic preparation, 0.5 microm cross-sections, taken every 0.2 mm from the 1- to 3-mm apical levels, were evaluated for percentage of tissue removal. Nonparametric analysis revealed mean percent canal and isthmus cleanliness values to be significantly higher for group 2 at all levels evaluated, except one. In conclusion, the 1 min use of the ultrasonic needle after hand/rotary instrumentation resulted in significantly cleaner canals and isthmuses in the mesial roots of mandibular molars.     

下颌第一恒磨牙根尖形态的显微CT研究

目的:使用显微CT研究下颌第一恒磨牙根尖5 mm形态。方法:采用显微CT对152颗离体下颌第一恒磨牙进行扫描,利用3-D软件三维重建根尖5 mm形态。记录根尖孔和侧副孔数目、峡区发生和分型。结果:94.08%下颌第一恒磨牙有两个单独牙根,61.84%有3个根管。60.91%的近中根有两个根尖孔。37.27%的近中根和33.01%的远中根有侧副孔。73.68%的牙出现峡区,峡区形态以IV型最为常见。结论:下颌第一磨牙根尖形态复杂,常规根管治疗和根尖手术应考虑其复杂性。     

Canal and Isthmus Debridement Efficacy of the VPro EndoSafe Negative-pressure Irrigation Technique

Introduction

This study compared canal and isthmus debridement efficacies between side-vented needle irrigation (SNI) and the VPro EndoSafe (VPro) negative-pressure device (Vista Dental, Racine, WI) in mesial roots of mandibular first molars with narrow isthmuses in a closed-canal design.

Methods

Twenty teeth with narrow isthmuses were selected using micro–computed tomography scanning. Collagen solution was reconstituted with 1% NH₄OH to simulate debris and injected into canals via vacuum. Canals were instrumented to size 40/.04. Final irrigation was performed with 17% EDTA and 6% NaOCl using SNI with a 30-G needle or the VPro system. Roots were demineralized, and Masson trichrome–stained sections were prepared at 1.2 to 3.2 mm from the anatomic apex for a total of 6 canal levels. Debris-filled areas within the canals and isthmuses were measured using ImageJ software (National Institutes of Health, Bethesda, MD) and statistically analyzed using repeated-measures analysis.

Results

There was no significant difference between techniques and debridement efficacy among the 6 levels within the canal (P = .108). The debridement efficacy at 1.6 mm differed significantly from that at 3.2 mm. VPro had significantly more debris at isthmus levels 2.0 and 2.4 mm than SNI (P = .009). A significant difference was observed between the canal and the isthmus (P < .001). Neither VPro nor SNI removed debris completely from the apical third or isthmus.

Conclusions

VPro EndoSafe did not differ significantly from SNI in the overall debridement efficacy in the apical third of mesial roots of mandibular first molars.     

Deviations of Mesial Root Canals of Mandibular First Molar Teeth at the Apical Third: A Micro–computed Tomographic Study

Introduction

The present study aimed to quantitatively analyze apical foramen deviations of mesial root canals of mandibular first molar teeth by means of micro–computed tomographic (micro-CT) imaging.

Relationships between pain-related mediators and both synovitis and joint pain in patients with internal derangements and osteoarthritis of the temporomandibular joint

OBJECTIVES: Routine dental CT scans were used to describe mandibular first premolar root configurations and canal variations. STUDY DESIGN: One hundred twenty dental CT examinations were evaluated for mandibular first premolar root configurations and canal variations regarding shape of root and root canal, incidence of multiple canals, and level of bifurcation. RESULTS: A total of 17 teeth in 12 patients showed mesial invagination of the root of the mandibular first premolar. One root displayed 3 canals with 3 apical foramina. In 2 teeth, a single canal divided into 2 canals, but merged into 1 apical foramen. One root showing 2 root canals finally divided into 2 roots near the apex. Thirteen roots had 2 canals and 2 apical foramina. The distance from the cementoenamel junction to the level of bifurcation was between 4 and 13 mm (mean, 7.4 mm). CONCLUSION: The occurrence of incidentally found mandibular first premolar root variations should be an important component of dental CT reports.     

Comparison of the Canal Master endodontic instrument and K-type files for enlargement of curved root canals

Twenty mandibular molars with 40 mesial curved root canals were instrumented with a circumferential technique using K files and the Canal Master instrumentation technique by junior dental students whose only endodontic experience had been completion of a preclinical endodontic course. Preoperative and postoperative radiographs were taken facially and mesially with instruments in place. The canals were evaluated radiographically for transportation 1 mm and 4 mm from the apex. The mesial roots were cross-sectioned at the same level. The sections were evaluated for roundness of the canal preparation. It was concluded that the Canal Master instrumentation technique transported the root canal less and produced rounder preparations than the K file circumferential technique. There appears to be a greater tendency for breakage with the Canal Master.     

Histologic evaluation of canal and isthmus debridement efficacies of two different irrigant delivery techniques in a closed system

Introduction

This study compared canal and isthmus debridement efficacies between side-vented needle irrigation (SNI) and continuous ultrasonic irrigation (CUI) in the mesial root of mandibular first molars with narrow isthmuses using a closed-canal design.

Methods

Micro-computed tomography scanning was used to select 20 teeth, each containing a narrow isthmus. Each root was sealed at the apex; embedded in polyvinylsiloxane to simulate a closed-canal system; and instrumented to size 40, 0.04 taper. Final irrigation was performed with either SNI or CUI (N = 10). Masson trichrome-stained sections were prepared from demineralized roots at 10 canal levels between 1.0 and 2.8 mm from the anatomic apex. The areas and debris occupied by the canals and isthmus were measured using ImageJ software (National Institutes of Health, Bethesda, MD) and statistically analyzed using repeated-measures analysis.

Results

Overall, a significant difference was identified between SNI and CUI in the amount of debris remaining in the isthmus (P = .006) but not in the canal (P = .940). There was significantly more debris in the most apical three canal levels (1.0-1.4 mm) regardless of the irrigation technique (P < .001). The isthmus harbored significantly less debris in the CUI group between isthmus levels 1.0 to 2.2 mm when compared with SNI (P < .001 and P = .029). Neither technique removes debris completely from the canal or isthmuses.

Conclusions

Compared with SNI, CUI removes significantly more debris from narrow isthmuses of mandibular mesial roots.     

Residual dentin thickness in mesial roots of mandibular molars prepared with Lightspeed rotary instruments and Gates-Glidden reamers

OBJECTIVE: We sought to measure the residual dentin thickness (RDT) in the mesial roots of mandibular molars after instrumentation with Lightspeed and Gates-Glidden rotary instruments.Study design Thirty extracted, untreated human mesial roots of mandibular molars were separated from the distal roots and embedded in clear polyester resin. The roots were cut horizontally at 1, 4, and 7 mm short of the anatomic apex. The diameter of each mesiobuccal canal was measured by using a stereo measuring microscope at each level in the buccolingual and mesiodistal directions. The dentin thickness was measured in each level in the mesial, distal, buccal, and lingual directions. Sections were reassembled with a muffle. The canals were enlarged to the working length with Lightspeed rotary instruments, of which the average size used was a No. 50 file. The coronal third was flared with No. 2 Gates-Glidden reamers. Slices were separated again, and the RDT and canal diameters were measured. RESULTS: The minimal measured RDT after instrumentation at the 1-, 4-, and 7-mm levels was 0.70 +/- 0.28 mm, 1.04 +/- 0.18 mm, and 1.09 +/- 0.19 mm, respectively. The average diameter of the canals after instrumentation at the 1-, 4-, and 7-mm levels was 0.50 +/- 0.04 mm, 0.52 +/- 0.05 mm, and 0.74 +/- 0.08 mm, respectively. The canal diameter did not exceed one third of the root diameter at all levels. CONCLUSIONS: Root canal preparation of mandibular mesial roots with Lightspeed instruments to No. 50 in the apical third and Gates-Glidden reamers to No. 2 in the coronal third does not significantly decrease the RDT.     

Micro-computed tomography study of the internal anatomy of mesial root canals of mandibular molars

Introduction

The aim of this study was to determine the mesiodistal and buccolingual diameter, apical volume, and the presence of isthmuses at the apical level of mesial root canals of mandibular molars.

Methods

Sixty extracted first and second mandibular molars were scanned by using a SkyScan 1076 micro-computed tomography system with a voxel size of 18 μm. The apical thirds of the samples were reconstructed to allow a perpendicular section of the apical third by using the multiplanar reconstruction tool of the OsiriX software. The mesiodistal and the buccolingual distances of root canals were measured between the 1- to 4-mm levels. The type of root canal isthmuses present at these levels was classified by using modified criteria of Hsu and Kim. The volume of the root canal anatomy between the 1- to 3-mm apical levels was obtained by using the CTAN-CTVOL software.

Results

The medians of the mesiodistal diameter at the 1-, 2-, 3-, and 4-mm levels in the mesiobuccal and mesiolingual canals were 0.22 and 0.23 mm, 0.27 and 0.27 mm, 0.30 and 0.30 mm, and 0.36 and 0.35 mm, respectively. The buccolingual lengths at the 1-, 2-, 3-, and 4-mm levels were 0.37-0.35 mm, 0.55-0.41 mm, 0.54-0.49 mm, and 0.54 and 0.60 mm, respectively. The presence of isthmuses was more prevalent at the 3- to 4-mm level. However, 27 cases presented complete or incomplete isthmuses at the 1-mm apical level. The mean of the volume of the apical third was 0.83 mm³, with a minimum value of 0.02 and a maximum value of 2.4 mm³.

Conclusions

Mesial root canals of mandibular molars do not present a consistent pattern. A high variability of apical diameters exists. The presence of isthmuses at the apical third was not uncommon even at the 1-mm apical level.     

Morphometric study of the apical anatomy of C-shaped root canal systems in mandibular second molars

AIM: To investigate the apical anatomy of C-shaped canal systems in mandibular second molars by micro-computerized tomography (microCT) and stereomicroscopy. METHODOLOGY: Forty-four permanent mandibular second molars with a C-shaped root canal systems from a native Chinese population were scanned at 100 microm intervals by microCT at a resolution of 30 x 30 microm. The apical 5 mm of each tooth was reconstructed three-dimensionally for visualization and classification of the canal configuration using Vertucci's criteria. The main and auxiliary (accessory) foramina were examined under a stereomicroscope. RESULTS: Type IV and VIII canal configurations were most often found in the apical 5 mm of these canal systems. The prevalence of accessory canals, lateral canals, inter-canal communications and apical delta were 41%, 25%, 27% and 11%, respectively. Approximately 80% of C-shaped canals had 1-3 apical foramina; the prevalence of accessory foramina was about 48%. The mean distance between the main foramen and the anatomic root apex was 0.84 mm, and that between the accessory foramen and the apex was 1.61 mm. The mean (shortest and longest) diameters of major and accessory foramina were 0.19 - 0.32 mm and 0.07 - 0.10 mm, with a mean form factor of 0.73 and 0.82, respectively. CONCLUSION: The apical anatomy of C-shaped root canal systems in mandibular second molars is extremely complex with many anatomical variations.     

Stereomicroscopic evaluation of canal shape following hand, sonic, and ultrasonic instrumentation

This study evaluated the root canal shape after using sonic, ultrasonic, and hand instrumentation on the mesial canals of extracted human mandibular first and second molars. One-hundred and five mesial roots were randomly divided into six experimental groups and one untreated control group of 15 roots each. The following instrumentation techniques were evaluated in the experimental groups: hand instrumentation with K-Flex files, sonic instrumentation with the Endostar 5, sonic instrumentation with the Sonic Air MM 3000, and ultrasonic instrumentation with the Cavi-Endo unit. Each technique was directly compared with each other. The mesial roots were instrumented alternating the techniques between the buccal and lingual canals in each group so that a direct comparison could be made. All canals were instrumented to a size corresponding to a #30 K-Flex file 1 mm from the anatomical apex. The roots were then sectioned perpendicular to the long axis so the apical and middle thirds could be evaluated with the stereomicroscope for canal shape. The control group was sectioned and examined without instrumentation. A significantly more regular shape was obtained at both levels with hand instrumentation than was obtained with either sonic or ultrasonic techniques. The comparisons between the sonic and ultrasonic techniques showed significantly better shapes were obtained with the Sonic Air MM 3000 instrument.     

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。     

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目的观察下颌第二磨牙牙根、牙根不同部位根管数目及形态,为根管治疗提供依据。方法选取2006年1月至2008年4月首都医科大学附属北京中医医院口腔科门诊中因各种原因拔除的下颌第二磨牙166颗,观察牙根数目及形态后,将牙根切为根上1/3,根中1/3和根尖1/3。观察不同部位的根管数目及形态。结果下颌第二磨牙单根12颗(7.2),双根101颗(60.8),其中近中根1-1型根管48颗(47.5),2-1型30颗(29.7),1-2型18颗(17.8),2-2型5颗(5)。远中根1-1型根管88颗(87.1),2-1型2颗(2.0),1-2型4颗(4.0),2-2型7颗(6.9)。C形根53颗(32.0),其中只有26颗具有C形根管(49)。166颗患牙中C形根管的总检出率为15.7。结论下颌第二磨牙牙根及根管数目、形态变异较多,C形根管的存在给根管治疗带来困难,不利于根管的彻底清理和充填。