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.

Study of pulp blood flow in normal adult first molars detected by laser Doppler flowmetry / 口腔疾病防治

Objective @#To explore the "clinical normal reference range" of pulpal blood flow (PBF) in the physiological state in an effort to provide a reference for clinical diagnosis and treatment.@* Methods@# According to the working principle and operational considerations of laser Doppler flowmetry (LDF), the PBF blood flow value of the first molars of the upper and lower mandibles of normal adults was detected by LDF, and the clinical reference value range under physiological conditions was analyzed and calculated. The differences in PBF values by sex, dental position and location (left and right side, upper and lower jaw) were analyzed. @*Results @#A total of 200 normal adult participants with an average age of (22.76 ± 3.26) years were included. The cohort included 95 males and 105 females, with a total of 800 first molars. Neither the PBF values of the left and right first molars nor the PBF values of the upper and lower first molars in males or females significantly differed (P>0.05). The PBF value for females was higher than that of males. Specifically, the clinical reference PBF values for males and females were (8.56 ± 3.25) PU and (9.51 ± 3.47) PU, respectively.@*Conclusion @#The PBF values of normal adult first molars in healthy subjects were higher in females than in males, and in the PBF values of first molars of the same sex did not significantly differ between the left side and right side or upper and lower jaw; these values could be used as a reference for the selection of control teeth.

CBCT detection of the incidence of middle mesial canal and isthmus in the mandibular first molar / 口腔疾病防治

Objective @# To analyze the morphology and incidence of middle mesial canal (MM) and isthmus in the mandibular first permanent molar by cone-beam computed tomography (CBCT).@*Methods@# Statistical analysis was performed on images from patients who underwent CBCT examination in the Department of Radiology at Stomatological Hospital, Southern Medical University. Samples exhibiting root canal treatment, root resorption and calcification were excluded. Data regarding sex, age, the presence or absence of isthmus and MM, and the number of roots and root canals were recorded.@*Results @#Of the 217 mandibular first molar samples, 8 (3.7%) had an MM, and 2 (0.9%) had an independent apical foramen. The overall incidence rate of isthmus was 57.1%; this rate was 50.7% in the cervical third of the root canal, 17.5% in the middle third, and 13.4% in the apical third. The incidence rate of isthmus was 61.8% on the left side, 52.3% on the right side, 58.7% in males, and 55.8% in females. No significant difference was found between the left and right sides or between females and males (P > 0.05). The incidence rate of isthmus in people under 60 was greater than 50% but was significantly lower in people older than 60.@*Conclusion@#Only a very small proportion of MMs have an independent apical foramen in the mandibular first molar. The incidence of isthmus in the mesial root of the mandibular first permanent molar is high, and isthmus usually occurs in the cervical third of the root canal. During root canal treatment or apical surgery, attention should be given to the physical and chemical preparation of the isthmus.

Morphology of Mesiobuccal Root Canals of Maxillary First Molars: a comparison of CBCT scanning and Cross-sectioning

Abstract: The aim of this study was to evaluate the mesiobuccal root of maxillary first molars, according to the root canal configuration, prevalence and location of isthmuses at 3 and 6 mm from the apex, comparing cone-beam computed tomography (CBCT) analysis and cross sectioning of roots by thirds. Images of the mesiobuccal root of 100 maxillary first molars were acquired by CBCT and then roots were cross-sectioned into two parts, starting at 3 mm from the apex. Data were recorded and analyzed according to Weine's classification for root canal configuration, and Hsu and Kim's classification for isthmuses. In the analysis of CBCT images, 8 root canals were classified as type I, 57 as type II, 35 as type III. In the cross-sectioning technique, 19 root canals were classified as type I, 60 as type II, 20 as type III and 1 as type IV. The classification of isthmuses was predominantly type I in both CBCT and cross-sectioning evaluations for sections at 3 mm from the apex, while for sections at 6 mm from the apex, the classification of isthmuses was predominantly types V and II in CBCT and cross-sectioning evaluations, respectively. The cross-sectioning technique showed better results in detection of the internal morphology of root canals than CBCT scanning.

Resumo: O objetivo do presente estudo foi avaliar a raiz mésio-vestibular de primeiros molares superiores, de acordo com a configuração do canal radicular e com a prevalência e localização de istmos a 3 e a 6 mm do ápice, comparando a análise realizada em tomografia computadorizada de feixe cônico (TCFC) com a técnica de seccionamento transversal por terços. Foram obtidas imagens tomográficas das raízes mésio-vestibulares de 100 primeiros molares superiores, e em seguida, as raízes foram seccionadas em dois segmentos, iniciando nos 3 mm a partir do ápice. Os dados foram analisados de acordo com a classificação de Weine para configuração de canais radiculares, e de acordo com a classificação de Hsu e Kim para avaliação dos istmos. Na análise das imagens das TCFCs, 8 canais radiculares foram classificados como tipo I, 57 como tipo II, e 35 como tipo III. Na técnica de seccionamento transversal, 19 canais radiculares foram classificados como tipo I, 60 como tipo II, 20 como tipo III, e 1 como tipo IV. Na avaliação dos istmos, houve predominância do tipo I tanto na TCFC quanto na técnica de seccionamento transversal a 3 mm do ápice. Entretanto, a 6 mm do ápice, a classificação dos istmos foi predominantemente tipo V e II, na avaliação em TCFC e na técnica de seccionamento transversal, respectivamente. A técnica de seccionamento transversal demonstrou melhores resultados na detecção da morfologia interna dos canais radiculares avaliados do que a TCFC.

Bilateral three-rooted primary lower molars.

The dental literature contains a small number of reports of primary multi-rooted anomalies. Among these reports the majority are regarding three-rooted primary mandibular second molar anomalies. The presence of bilateral three-rooted primary mandibular first and second molars is uncommon. There have been no reports of three-rooted primary molars from India. Here, we present a case of an 8-year-old boy with bilateral three-rooted primary mandibular first and second 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 percent. 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.

Os objetivos deste estudo foram avaliar a presença e a freqüência de istmos nas raízes mesiais de primeiros molares superiores e inferiores (em dois níveis de ressecção a partir do ápice), e comparar os achados obtidos por observação macroscópica (OM) e microscópio operativo (MO). Quarenta raízes mesiais superiores e inferiores foram examinadas a 3 e 5 mm do ápice, inicialmente macroscopicamente e em seguida com o uso do MO. A presença de istmo e o número de canais radiculares detectado foram registrados. Os dados foram analisados estatisticamente usando o teste exato de Fisher para avaliação do istmo e o teste de Wilcoxon (signed rank-test) para o número de canais radiculares, com um intervalo de confiança de 95 por cento. A comparação entre OM e MO com relação ao número de raízes com istmos forneceu os seguintes resultados: Grupo mandibular: 3 mm: OM 19 vs. MO 27; 5 mm: OM 31 vs. MO 32. Grupo maxilar: 3 mm: OM 9 vs. MO 14; 5 mm: OM 19 vs. MO 21. Diferenças significantes (p<0,05) foram encontradas com relação à precisão dos métodos de detecção de istmos em ambos os níveis de ressecção (3 e 5 mm), e ambos os tipos de raízes, bem como quanto ao número de canais radiculares inspecionados sob MO entre os dois níveis de ressecção das raízes mesiais dos primeiros molares superiores. Nas condições testadas, MO aumentou a precisão diagnóstica na detecção de istmos em ambos os níveis de ressecção e tipos de raízes.

Clinical study of the three mesial root canals of mandibular first molars / 实用口腔医学杂志

Objective:To investigate the clinical incidence of the three mesial root canals of mandibular first molars. Methods: Incidence and morphology of the three mesial root canals of mandibular first molars were determined by probing the fissure or grooves between the mesiobuccal and mesiolingual root canal orifices and X-ray analysis. Results: Of the 222 mandibular first molars, 13 of the molars had three mesial root canals. The incidence rate was 5.85 %. Conclusion: Although the incidence rate of the three mesial root canals of mandibular first molars was very low, the dental operative microscope was helpful for the diagnosis.