The Investigation On Pulp Chamber And Root Canal System Morphology Of Permanent Molars

[Objects]338permanent maxillary and mandibular first and second molars were collected from Yunnan province:maxillary first molar (92), maxillary second molar(81), mandibular first molar (80), mandibular second molar(85). X-radiograph, clearing techniques, dental operating microscope and micro-CT scanning with three dimensional reconstruction methods had been used to detect anatomy of pulp cavity and root canal system of the molars, to establish the technical criterion of root canal therapy (RCT), and evaluate of quality control and therapeutic effect. Meanwhile, this result will be provided for teaching references or guidance information of clinical teaching.[Methodology]1.X-radiograph, the specimens were shot by the parallel radiographic technique, and the distance between chosen location were measured by digital vernier caliper (0.01mm):Occlusion surface to pulp chamber ceiling, Occlusion surface to pulp chamber floor, Occlusion surface to furcation, pulp chamber floor to furcation, pulp chamber ceiling to furcation, pulp chamber height.2.Clearing techniques:the specimens were made into cleared tooth, the root canal number, type, structure, shape were observed and recorded, canal type following vertucci’s classification.3.Dental operating microscope:observe the number of root canal、shape of the pulp chamber floor and measure of root canal orifice spacing of the specimens under the dental operating microscope after pulp chamber open and pulp top remove. 4. Micro-CT:The specimens were scanned by micro-CT (30μm) and the root canal system had been reconstructed by VGS software, taken pictures and made into a three-dimensional video to analyze the internal structure and type of root canal.[Results]1.The most present type in maxillary first molar was4canals (46.3%) or3canals (42.86%),5canals type (3.18%) and6canals type (1.59%) present also. MB2presents a high incidence of54%。The mesiobuccal root structure is the most complicated, typeVI, type I and "Y+λ" shape,"Ⅰ" shape were common types. Type I went most frequently in distobuccal root and palatal root, followed by type V. The average distance of MB2-MB canal orifice was2.12±0.5mm.2.The most present type in maxillary second molar is three canals (61.4%) or four canals (35.1%). MB2had a higher incidence of35.1%. The main canal types and shape of mesiobuccal root were type Ⅰ,type Ⅱ,type Ⅴ and "Ⅰ ","Y","λ" shape. Type I goes most frequently in distobuccal root and palatal root. The average distance of MB2-MB canal orifice was1.62±0.50mm.3.The primary type in the mandibular first molar are four canals (56.4%) and three canals (41.8%).The main canal types and shape of mesial roots were typeVI,type Ⅳ,type Ⅱ and "H","Ⅱ","Y"shape. Distal root were type Ⅰ,type Ⅱ,type Ⅳ. The average distance of pulp chamber height and pulp chamber floor to furcation were1.10±0.55mm,2.65±0.45mm, respectively.4. The most present type in the mandibular second molar was three canals (62.7%), two canals (20.3%) or four canals(17%).C shaped canal incidence was29.4%. The main canal types and shape of mesial roots were type Ⅰ,type Ⅵ,type Ⅳ and "Ⅰ ","H","Ⅱ" shape. Distal root was type Ⅰ. The average distance of pulp chamber height and pulp chamber floor to furcation were1.25±0.57mm,2.65±0.56mm, respectively.[Conclusion] MB2had a higher incidence in maxillary first and second permanent molar. The structure of mesiobuccal root canal is complicated and variant. Four canals type of mandibular first molar presents a higher incidence, to which more attention should be paid. Clinical operation difficulties could be caused by high-incidence of C shaped canal of mandibular second molar and morphological diversity. Micro-CT is more efficient,complete and accurate compared with X-Ray,clearing tooth and dental operating microscope technique, in the mean time, it does no damage to the tooth structure, but it is too expensive that it is not widely used in clinical. Magnification and lighting of dental operating microscope, combined with ultrasound and CT, can provide effective help for clinical diagnosis and therapy.