Natural canal deviation and dentin thickness of mesial root canals of mandibular first molars assessed by microcomputed tomography

Abstract The aim of this study was to assess the centralization and dentin thickness of mesial root canals of the first mandibular molars by microcomputed tomography (micro-CT). Material and methods: Ninety-nine mandibular molars of Vertucci's type IV canals were scanned by micro-CT. The mesiodistal deviation and centroid were assessed, in both mesiobuccal (MB) and mesiolingual (ML) canals, for the apical 4mm and the full canal length. Results: The dentin thickness was similar for both MB and ML canals. The narrowest thickness was in the distal wall of an MB canal (0.07mm), while the widest was found in the mesial wall of an MB canal (2.46mm). In centroid analysis, both the MB and ML canals exhibited deviations when compared to the root centroid, along the full canal length and the apical 4mm. For the MB canal, the mean deviation was 0.83mm (0.02 mm-2.30 mm) for the full canal and 0.18mm (0.01 mm-1.01 mm) for apical 4mm. Similarly, for the ML canal, the mean deviation measured 0.83 mm (0.05mm-3.99mm) for the full canal and 0.21 mm (0.01mm-1.01mm) for the apical 4 mm. Overall, deviations were observed towards the mesial of the roots, with 69% for MB and 57% for ML canals for the full canal, and 51% for MB canals within the 4 mm. The exception was the ML canal, which exhibited a higher deviation towards distal in the apical 4mm, accounting for 52% of cases. The dentin thickness was consistent between the mesial canals of mandibular molars. However, there is no centrality of mesial canals in their roots, with frequent deviation to mesial.

Resumo O objetivo deste trabalho foi avaliar a centralização e a espessura da dentina dos canais radiculares mesiais de primeiros molares inferiores por meio de microtomografia computadorizada (micro-CT). Material e métodos: Noventa e nove molares inferiores com canais tipo IV de Vertucci foram escaneados por micro-TC. O desvio mesiodistal e o centroide foram avaliados para os canais mesiovestibular (MB) e mesiolingual (ML), nos 4mm apicais e em todo o comprimento do canal. Resultados: A espessura da dentina foi semelhante para os canais MB e ML. A espessura mais estreita foi encontrada na parede distal de um canal MB (0,07mm), enquanto a mais larga foi encontrada na parede mesial de um canal MB (2,46mm). Na análise centroide, tanto o canal MB quanto o ML exibiram desvios quando comparados ao centroide da raiz, ao longo de todo o comprimento do canal e nos 4 mm apicais. Para o canal MB, o desvio médio foi de 0,83mm (0,02mm-2,30mm) para canal inteiro e 0,18mm (0,01mm-1,01mm) para o apical de 4mm. Da mesma forma, para o canal ML, o desvio médio mediu 0,83 mm (0,05 mm-3,99 mm) para o canal inteiro e 0,21 mm (0,01 mm-1,01 mm) para os 4 mm apicais. No geral, foram observados desvios em direção mesial das raízes, sendo 69% para canais MB e 57% para canais ML para canal inteiro, e 51% para canais MB dentro dos 4 mm. A exceção foi o canal ML, que apresentou maior desvio para distal nos 4mm apicais, representando 52% dos casos. A espessura da dentina foi consistente entre os canais mesiais dos molares inferiores. Entretanto, não há centralidade dos canais mesiais em suas raízes, com frequente desvio para mesial.

Effect of contracted endodontic access cavity and root canal preparation by One Curve on danger zone of mesial root canal in mandibular first molars / 口腔疾病防治

Objective @#To explore the influence of a contracted endodontic access cavity on the risk of canal transportation in the danger zone of the mesial root canal of mandibular first molars (MFMs) using a one-curve preparation system, and to provide an experimental basis for the clinical selection of a better pulp approach.@*Methods@#Twenty MFMs extracted for severe periodontal disease that met the inclusion criteria, including intact coronal roots, mesial roots with two separate root canals, mesiobuccal canal (MB) and mesiolingual canal (ML), and a curvature of 0° to 20°, were selected. Subsequently, these MFMs were randomly divided into two groups based on the endodontic access design, including the traditional endodontic access cavity (TEC) group and the contracted endodontic access cavity (CEC) group. In the TEC group, the pulp chamber roof of the tooth was completely removed, while in the CEC group, the pulp chamber roof and peri-cervical dentin were preserved as much as possible. Then, the One Curve single file was adopted to conduct root canal preparation. Next, cone beam computed tomography (CBCT) was performed on extracted teeth before and after preparation, and the measurement sections were located at 0-7.0 mm below the root bifurcation of the mesial root canal at 1 mm intervals. The minimum wall thickness on the mesial and distal aspect of the root canal was measured in each section.@* Results @# ① Prepreparation CT measurements of 20 MFMs showed that the danger zone in the range 0-4 mm under root bifurcation, a mean thickness of 1.18 mm on the mesial aspect of the MB root canal and 1.08 mm on the distal aspect. The mean thickness of the ML root canal was 1.28 mm on the mesial aspect and 1.07 mm on the distal aspect. ② Compared with that of the traditional endodontic access cavity, no significant difference in the decrease of wall thickness was observed in the danger zone of mesial root canal of MFMs in the contracted endodontic access cavity (t = 1.319，P = 0.19). ③ In the mesiobuccal canal, compared with the apical transportation of the traditional endodontic access cavity, which tends to be more mesial side, the apical transportation of contracted endodontic access cavity tends to the distal side. In the mesiolingual canal, both apical transportation groups tended to be on the distal side. @*Conclusion @# When using the One Curve file, compared with traditional endodontic access, the contracted endodontic access cavity based on the minimally invasive concept does not increase the risk that the mesial root canal of mandibular first molars is transported.

Classification of furcation involvement of endodontically treated mandibular first permanent molars based on cone beam CT / 口腔疾病防治

Objective @#To classify the furcation involvement (FI) of endodontically treated mandibular first permanent molars based on cone beam computed tomography (CBCT), provide reference for individualized treatment of FI. @*Methods@#CBCT images of the FI of 164 endodontically treated mandibular first permanent molars from 163 patients in Nanjing Stomatological Hospital, Medical School of Nanjing University were collected retrospectively. On the CBCT images, the shape and extent of periapical and periodontitis bone resorption, the thickness of residual dentin in the pulp floor and root canal wall, and the periodontal bone resorption of the complete dentition were evaluated. The FI was classified into periodontal, periapical, perforated and mixed types.@* Results@#Among the 164 FIs of endodontically treated mandibular first permanent molars, the periapical type was the most common (41.5%), followed by the mixed type (26.2%), perforated type (18.3%), and periodontal type (14.0%). Among the 68 periapical-type FIs of endodontically treated mandibular first permanent molars, 48.5% were proper root canal filling, 44.1% were insufficient filling and 7.4% were overfilling. Among the 43 mixed-type FIs, the periodontal mixed periapical type was the most common (72.1%).@*Conclusion @#Detailed evaluation and classification of furcation involvement could be performed using CBCT images; therefore, the study has guiding significance for clinical treatment.

Measurement of the Radial Nerve Danger Zone in Filipino Adults: A Cadaveric Study

@#Introduction: The radial nerve danger zone (RNDZ) is an important anatomic consideration to anticipate or prevent injury in trauma assessment or surgical fixation. No published estimate currently exists for Filipinos. In this study, we sought to provide a local estimate and explore potential predictors of this anatomic region in Filipino adult cadavers. Materials and methods: Posterior dissection to expose and measure the radial nerve, from the lateral epicondyle to the lateral intermuscular septum, was performed in 60 upper limbs from 30 formalin-preserved cadavers in the laboratory of the Department of Anatomy, College of Medicine, University of the Philippines Manila. Univariate and multivariate linear regression modelling was performed with RNDZ as the dependent variable and age, sex, height and humeral length as potential independent variables individually and in combinations. Results: The mean radial nerve length from the lateral epicondyle to the lateral intermuscular septum was estimated at 10.6 cm (95% confidence interval: 10.3 cm, 10.9cm). Height and humeral length were statistically significant univariate predictors in female cadavers, while only height was significant in male cadavers. In addition, all multivariate regression models were statistically significant and accounted for more than 57% of the variability in female RNDZ estimates. In comparison, only models that included height and age were statistically significant predictors of RNDZ and accounted for at most 22% of the variability of the estimate in males. Conclusion: The estimated length of the radial nerve danger zone generated in this study should be strongly considered over other published estimates in surgical fixation procedures performed in adult Filipinos.

Anatomical Danger Zone in Open Inguinal Herniorrhaphy

PURPOSE: Because of complex inguinal structures, we cannot overcome the neurogenic complications in open inguinal herniorrhaphy. Nowadays, there are few studies of anatomical danger zones in open herniorrhaphy. So, in this study we would cover the danger zones in hernia surgery with a cadaver. METHODS: We studied the anatomic structures of three male cadavers. There was no anatomical variation among them. We can ascertain the running of the ilioinguinal nerve, iliohypogastric nerve, and genitofemoral nerve. RESULTS: We can see that the ilioinguinal nerve runs anterior to the spermatic cord in the inguinal canal and lies beneath the external oblique aponeurosis. The iliohypogastirc nerve runs on the anterior surface of the internal oblique muscle, and aponeurosis medial and superior to the internal ring. The genital branch of the genitofemoral nerve lies on the iliopubic tract and accompanies the cremaster vessels to form a neurovascular bundle. In these areas, we often suture the anchor in open herniorrhaphy, increasing probability of these nerves suffering injury. CONCLUSION: In open inguinal herniorrhaphy, surgeons must have a comprehensive understanding of the neural anatomy of the groin to reduce post-operative complications. Moreover, we must consider not only anatomical understanding but also surgical procedures reducing neurogenic complications. So, we suggest certain procedures to reduce nerve injury such as three dimensional mesh or the use of fibrin glue.

Evaluation of danger zone in mesial root of mandibular first molar by cone beam computed tomography (CBCT) / 대한구강악안면방사선학회지

PURPOSE: To examine the danger zone of mesial root of mandibular first molar of patient without extraction using CBCT(cone -beam computed tomography) to avoid the risk of root perforation. MATERIALS AND METHODS: 20 mandibular first molars without caries and restorations were collected. CT images were obtained by CBCT(PSR9000N TM, Asahi Roentgen Co., Japan), reformed and analyzed by V-work 5.0 (CyberMed Inc., Korea). Distance between canal orifice and furcation was measured. In cross sectional images at 3, 4 and 5 mm below the canal orifice, distal wall thickness of mesiobuccal canal (MB-D), distal wall thickness of mesiolingual canal (ML-D), distal wall thickness of central part (C-D), mesial wall thickness of mesiobuccal canal (MB-M) and mesial wall thickness of mesiolingual canal (ML-M) were measured. RESULTS: The mean distance between the canal orifice and the furcation of the roots is 2.40 mm. Distal wall is found to be thinner than mesial wall. Mean dentinal wall thickness of distal wall is about 1 mm. The wall thickness is thinner as the distance from the canal orifice is farther. But significant differences are not noted between 4 mm and 5 mm in MB-D and C-D. MB-D is thinner than ML-D although the differences is not significant. CONCLUSION: The present study confirmed the anatomical weakness of distal surface of the coronal part of the mesial roots of mandibular first molar by CBCT and provided an anatomical guide line of wall thickness during endodontic treatment.

Evaluation of danger zone in mesial root of mandibular first molar by cone beam computed tomography (CBCT) / 대한구강악안면방사선학회지

PURPOSE: To examine the danger zone of mesial root of mandibular first molar of patient without extraction using CBCT(cone -beam computed tomography) to avoid the risk of root perforation. MATERIALS AND METHODS: 20 mandibular first molars without caries and restorations were collected. CT images were obtained by CBCT(PSR9000N TM, Asahi Roentgen Co., Japan), reformed and analyzed by V-work 5.0 (CyberMed Inc., Korea). Distance between canal orifice and furcation was measured. In cross sectional images at 3, 4 and 5 mm below the canal orifice, distal wall thickness of mesiobuccal canal (MB-D), distal wall thickness of mesiolingual canal (ML-D), distal wall thickness of central part (C-D), mesial wall thickness of mesiobuccal canal (MB-M) and mesial wall thickness of mesiolingual canal (ML-M) were measured. RESULTS: The mean distance between the canal orifice and the furcation of the roots is 2.40 mm. Distal wall is found to be thinner than mesial wall. Mean dentinal wall thickness of distal wall is about 1 mm. The wall thickness is thinner as the distance from the canal orifice is farther. But significant differences are not noted between 4 mm and 5 mm in MB-D and C-D. MB-D is thinner than ML-D although the differences is not significant. CONCLUSION: The present study confirmed the anatomical weakness of distal surface of the coronal part of the mesial roots of mandibular first molar by CBCT and provided an anatomical guide line of wall thickness during endodontic treatment.

Avaliação do desgaste da zona de perigo de molares inferiores utilizando o sistema rotatório ProTaper / Evaluation of the flaring in mandibular molars danger zone using ProTaper rotatory system

O objetivo deste estudo foi avaliar in vitro o desgaste da zona de perigo em molares inferiores, após utilização do sistema de instrumentação rotatória ProTaper. Foram utilizadas 60 raízes mesiais de molares inferiores, as quais foram divididas em 4 grupos experimentais. Um grupo foi mantido como controle e os demais foram respectivamente instrumentados com as limas SX; SX e S1; SX, S1 e S2. Os resultados foram submetidos à análise estatística, demonstrando uma diferença significante no nível de 1% entre os grupos experimentais, com um aumento do desgaste da zona de perigo diretamente proporcional ao aumento do diâmetro dos instrumentos ProTaper. Conclui-se que por não ter acontecido nenhum caso de perfuração radicular a segurança desses instrumentos no preparo de molares inferiores foi demonstrada

The aim of this study was to evaluate in vitro the flaring in mandibular molars danger zone, after root canal instrumentation with the ProTaper rotatory instrument system. Sixty extracted mandibular molars with fully formed apices had the mesial roots sectioned. The specimens were divided into four groups and instrumented until Shaping X, Shaping 1 and Shaping 2 files,respectively. One group was kept as control with no instrumentation. The results submitted to statistical analysis, showed a 1% significant difference among experimental groups, with an enlargement of the flaring in danger zone being directly proportional to the diameter of ProTaper instruments. Itis concluded that the use of this instruments on the preparation of mandibular molars is safe because there isnt any report of root perforation.

Shaping ability of four rotary nickel-titanium instruments to prepare root canal at danger zone / 대한치과보존학회지

The aim of this study was to evaluate the shaping abilities of four different rotary nickel-titanium instruments with anticurvature motion to prepare root canal at danger zone by measuring the change of dentin thickness in order to have techniques of safe preparation of canals with nickel-titanium files. Mesiobuccal and mesiolingual canals of forty mesial roots of extracted human lower molars were instrumented using the crown-down technique with ProFile, GT(TM) Rotary file, Quantec file and ProTaper(TM). In each root, one canal was prepared with a straight up-and-down motion and the other canal was with an anticurvature motion. Canals were instrumented until apical foramens were up to size of 30 by one operator. The muffle system was used to evaluate the root canal preparation. After superimposing the pre- and post-instrumentation canal, change in root dentin thickness was measured at the inner and outer sides of the canal at 1, 3, and 5 mm levels from the furcation. Data were analyzed using two-way ANOVA. Root dentin thickness at danger zone was significantly thinner than that at safe zone at all levels (p 0.05). ProTaper removed significantly more dentin than other files especially at furcal 3 mm level of danger and safe zones (p < 0.05) Therefore, it was concluded that anticurvature motion with nickel-titanium rotary instruments does not seem to be effective in danger zone of lower molars.

Analysis of Danger Zone of the Posterior Column of Acetabulum and Morphological Data of the Isehial Tuberosity / 대한정형외과학회잡지

Ten emhalmed cadaveric adult bony hemipelvis specimens were ohtained to evaluate the configuration of the posterior column of acetabulum and to find a safe path for screw placement into it as well as to report on the morphological data of the ischial tuherosity and to determine the most optimaI technique for ischial tuberosity screw placement for open reduction and internal fixation of posterior acetabular fracture. Cadaveric studies were performed analyzing icm cross-sections through the acetabulum for the purpose of studying the anatomical configuration of the danger zone. The plane of the cross-section was perpendicular to the posterior column. Each cross-section had the medial boundary ot the acetabulum projected onto the posterior column. By analysing the projections on the posterior column, the exact configuration of the danger zone was determined. In this study, the average width of the posterior column at the mid-acetabular Ievel was 3.9cm. Computed tomography scan of the acetabulum yielded valuable int'ormation regarding screw placement in the posterior column. The average width, height and depth of the ischial tuberosity were 25.7 mm, 33. 1 mm and 31.7mm, respectively. The average angles hetween the posterior and medial aspects and hetween the posterior and lateral aspects of the ischial tuherosities were 79.5degreesand 111.5degrees, respectively. The entry point of the screw should be Smm or 10mm medial to the lateral margin of the ischial tuherosity and the screws should be directed 35-40degrees, 45-50degrees and 50-55degrees caudally at the level of the inferior acetahular margin and lcm and 2cm below it, respectively. to obtain the most favorable bony purchase.