背景:下颌磨牙的中内侧(MM)管的制备是一个挑战,因为它通常是弯曲的,狭窄,靠近根部凹面。这项研究的目的是使用3D打印树脂牙齿复制品评估3种镍钛(NiTi)旋转系统在MM管中的离体成形能力。
方法:从拔出的牙齿池中获取带有MM管的下颌第一磨牙,并通过3D打印机进行复制。将树脂牙齿复制品(n=18)平均分配给3组,以评估3个NiTi旋转系统的成形能力(OneShape[OS],扭曲的文件[TF],和ProTaperGold[PTG])根据制造商的建议。在插入近颊(MB)之前和之后,通过显微计算机断层扫描(micro-CT)扫描牙齿复制品两次,间舌(ML),和MM根管。三维重建后,运河矫直,根管体积和表面积的变化,评估了分叉以下1,2和3mm水平的中管和远管壁厚度以及运河运输。单向方差分析和土耳其的事后检验用于比较不同组之间的均值,并使用配对t检验比较中根的内侧和远端。
结果:与OS和TF相比,在MM管的制备中使用PTG导致明显更多的根管曲率变直(p<0.05),更大的仪器后管道容积和表面积,分叉以下1、2和3mm处的中部和远端剩余管壁厚度较薄(均p<0.05)。关于根管在近端方向的运输,制备MB和ML管后,3种仪器之间没有显着差异(均p>0.05)。然而,在MM运河里,在分叉下方2mm处的PTG组中检测到更明显的运输,与其他2个系统相比,TF组在分叉以下3mm处(均p<0.05)。
结论:3D打印的牙齿复制品具有一致性的优点,可以成为评估MM管中不同器械的塑形能力的理想模型。类似地执行的OS和TF文件,两者都适合于塑造MM渠道,而PTG可能会导致过度和不均匀的树脂去除,尤其是在分叉附近,并可能导致根的脆弱性和程序错误。
BACKGROUND: The preparation of the middle mesial (MM) canal of mandibular molars represents a challenge because it is often curved, narrow, and close to the root concave. The purpose of this study was to evaluate the ex vivo shaping ability of 3 nickel-titanium (NiTi) rotary systems in the MM canal using 3D printed resin tooth replicas.
METHODS: A permanent mandibular first molar with a MM canal was acquired from a pool of extracted teeth and reproduced by a 3D printer. The resin tooth replicas (n = 18) were equally assigned to 3 groups for the evaluation of the shaping abilities of 3 NiTi rotary systems (OneShape [OS], Twisted Files [TF], and ProTaper Gold [PTG]) according to the manufacturer\'s recommendations. The tooth replicas were scanned by micro-computed tomography (micro-CT) twice before and after instrumentation of the mesiobuccal (MB), mesiolingual (ML), and MM root canals. After 3D reconstruction, the canal straightening, change of root canal volume and surface area, the mesial and distal canal wall thickness and canal transportation at the levels of 1, 2, and 3 mm below furcation were assessed. One-way variance analysis and Turkey\'s post hoc test were used for comparisons of the means among different groups, and paired-t test was used to compare the mesial and distal sides of the mesial roots.
RESULTS: As compared with OS and TF, the use of PTG in preparation of MM canals resulted in significantly more straightening of canal curvature (p < 0.05), greater post-instrumentation canal volume and surface area, and thinner mesial and distal remaining canal wall thickness at 1, 2 and 3 mm below furcation (all p < 0.05). Regarding the root canal transportation in the mesiodistal direction, there was no significant difference among the 3 instruments (all p > 0.05) after the preparation of the MB and ML canals. However, in the MM canal, more pronounced transportation was detected in the PTG group at 2 mm below furcation, and in the TF group at 3 mm below furcation as compared with the other 2 systems (both p < 0.05).
CONCLUSIONS: 3D printed tooth replicas have the advantages of consistency and can be an ideal model to evaluate the shaping ability of different instruments in the MM canal. OS and TF files performed similarly and both are appropriate for shaping the MM canal, while PTG may cause excessive and uneven resin removal, especially near the furcation, and may lead to root fragility and procedural errors.