A Study as to How the Shape of Curved Root Canal After Preparation Exerts Influence on Lateral Condensation

本研究的目的是阐明在弯曲的根管上实现紧密根管吞噬的必要因素。在本实验中，通过改变根管的直径、锥度和曲率制备透明的根管模型。侧向冷凝采用不锈钢拉伸器(SS)和镍钛拉伸器(NT)。在根管模型表面评价牙胶尖的凝固性。对于弯曲根管且根管准备不充分的情况，也采用同样的方法评估侧向压缩的充填情况。根管直径的影响：发现根管厚度(直径)影响封闭剂向根尖方向的残留情况。结论：1.SS组和NT组均较易向根管深处插入较厚的根管，且较易在根尖处形成牙胶尖凝聚。…对根管的影响：在根管锥度较低的模型中，SS组和NT组的根管顶端大部分封闭剂残留在根管壁上，随着根管锥度的增大，扩张器可以插入到根管的深度，具有更好的固结效果。这导致了封闭剂在根管壁上的残留量减少。NT的充填情况稍差于SS，这可能与NT直径稍厚于SS，根管充填效果差，弹性差，不能达到充分的根管内凝聚有关。根管弯曲度的影响：SS和NT根管弯曲度对充填情况的影响较小，而NT根管弯曲度对扩张器插入性能的影响较小。根管预备不充分对根管形态的影响：根管预备不充分的根管，根管壁上可见不同类型的切割痕迹，不同的预备方法不同。胶粘剂在这一部分上残留较多，胶尖的凝结不足。在拉链上，由于扩张器的充填作用，根尖外弯曲过度切割，出现根尖弯曲现象，提示在弯曲根管的情况下，根管预备时要有足够的锥度，才能达到满意的根管充填效果。较少

The persent study was designed with the purpose of elucidating the factors necessary for achieving close and tight root canal swaling on the curved root canal. For the experiment, transparent root canal models were prepared by varying diameter, taper and curvature of the root canal. For lateral condenstation, stainless stell spreader (SS) and nickel-titanium spreader (NT) were used. Condensation of gutta-percha point was evaluated on the surface of root canal model. For the case of curved root canal with inadequate root canal preparation, the filling situation of lateral condensation was also evaluated by the same procedure.1. Influence of root canal diameter : It was found that the thickness (diameter) of root canal gave influence on the remaining condition of the sealer in the direction toward root canal tip. Thick root canal could be more easily inserted to the depth of root canal in both SS and NT, and condensation of gutta-percha point at root canal tip could be easily achieved.2. … More Influence of root canal : In a model with lower root canal taper, much of the sealer remained on root canal wall at root canal tip in both SS and NT.When the root canal taper was increased, it was possible to insert the spreader to the depth of root canal and it provided better effect on condensation. This contributed to the decrease of the amount of the sealer remaining on root canal wall. Filling condition was somewhat poorer in NT than SS.This may be attributed to the fact that NT showed poorer performance of insertion into root canal because it was slightly thicker in diameter than SS and also that its flexibility exerted reverse effect and sufficient condensation could not be attained.3. Influence of curvature of root : It appeared that the curvature of root canal exerted less influence on the filling condition in both SS and NT.However, when NT was used, there was less difference in the performance of insertion of the spreader due to the curvature.4. Influence of the inadequate shape of root canal preparation : In case of root canal with inadequate root canal preparation, different types of cutting marks were observed on root canal wall depending on the types of preparation methods. Sealer remained much on this part, and condensation of gutta-percha point was insufficient. On the zip, excessive cutting on outer curve of root canal tip, meander phenomenon of the point due to plugger effect of the spreader was observed.These results suggest that, in case of curved root canal, it is important to give adequate taper in root canal preparation for the purpose of achieving satisfactory root canal filling. Less