Tian Shi Yu, Bai Wei, Jiang Wei Ran, Liang Yu Hong
Chin J Dent Res. 2019;22(3):197-202. doi: 10.3290/j.cjdr.a43114.
To measure the fracture resistance of mandibular premolar roots following root canal instrumentation with different sizes.
A total of 100 human permanent mandibular premolars with a straight single canal were decoronated and assigned to 10 groups (n = 10) by block randomisation. In the control group, the roots were uninstrumented, whereas roots in the nine experimental groups were instrumented to different master apical files (MAF) and tapers (MAF/taper): 40/0.05, 45/0.05, 50/0.05, 55/0.05, 60/0.05, 40/0.10, 40/0.15, 45/0.10 and 45/0.15. All roots were subjected to vertical loading until fracture.
Fracture load values for instrumented roots were lower than the intact roots of the control group. In 50/0.05, 55/0.05, 60/0.05, 40/0.15 and 45/0.15 groups, the fracture load values were significantly lower than the fracture load value for the control group (P < 0.05) with a 30% decrease. No significant differences in the fracture modes were detected among the 10 groups (P > 0.05).
Mechanical instrumentation adversely affects the fracture resistance of roots. When the roots of mandibular premolars were instrumented to a MAF equal to or larger than 50 with a taper of 0.05 or to a MAF of 40 or 45 with a taper of 0.15, the fracture load values significantly decreased.
测量不同规格根管预备后下颌前磨牙牙根的抗折性。
选取100颗具有单一直根管的人类恒牙下颌前磨牙，去除牙冠，通过区组随机化分为10组（每组n = 10）。对照组牙根未进行预备，而9个试验组的牙根分别预备至不同的主尖锉（MAF）和锥度（MAF/锥度）：40/0.05、45/0.05、50/0.05、55/0.05、60/0.05、40/0.10、40/0.15、45/0.10和45/0.15。所有牙根均进行垂直加载直至折断。
预备后牙根的折断载荷值低于对照组的完整牙根。在50/0.05、55/0.05、60/0.05、40/0.15和45/0.15组中，折断载荷值显著低于对照组的折断载荷值（P < 0.05），降低了30%。10组之间的折断模式未检测到显著差异（P > 0.05）。
机械预备对牙根的抗折性有不利影响。当下颌前磨牙牙根预备至MAF等于或大于50且锥度为0.05，或MAF为40或45且锥度为0.15时，折断载荷值显著降低。
