Conservative Dentistry Unit, School of Dental Sciences, Universiti Sains Malaysia, Health Campus, Kubang Kerian, 16150, Kota Bharu, , Kelantan, Malaysia.
Odontology. 2021 Jul;109(3):672-678. doi: 10.1007/s10266-021-00589-1. Epub 2021 Jan 17.
To compare the microhardness and crack formation in root dentine presented with butterfly effect in lower premolars. Sixty mature lower premolars were selected and divided into the control and experimental groups. Teeth in the experimental group were instrumented up to size 30/.04. The roots were cut horizontally into twelve parts of 1-mm-thick cross-section and were numbered accordingly. They were divided into coronal, middle, and apical root sections. Sections were then viewed under a microscope to determine the presence of butterfly effect and subsequently scored. 8 teeth from both control and experimental groups with the highest and lowest score were selected. Crack formation was inspected and classified into four different types of cracks. Microhardness test was performed using a Vickers hardness test. Higher frequency of butterfly effect was found in the apical root section and root dentine with butterfly effect were harder mesiodistally. The middle and apical root sections with butterfly effect were harder than the coronal section. No significant difference of dentine hardness between the control and experimental groups. Cracks only occurred in the experimental group and presented in buccolingual direction with a higher rate of Type 1 and Type 2 cracks. Prevalence of butterfly effect in lower premolars increased from coronal to apical with increased hardness mesiodistally. More buccolingual cracks were found in radicular dentine with butterfly effect and most of them exhibited Type 1 and Type 2 cracks. Roots of lower premolar with butterfly effect may be susceptible to a higher rate of vertical root fracture in buccolingual direction, especially after root canal treatment. Thus, special attention should be given not to overload instruments during root canal preparation.
比较下颌前磨牙出现蝴蝶效应时的根管牙本质的显微硬度和裂纹形成。选择 60 颗成熟的下颌前磨牙，分为对照组和实验组。实验组的牙齿扩至 30/.04 号。将根部分为 12 个 1 毫米厚的横截面，并按顺序编号。将其分为冠部、中部和根尖部。在显微镜下观察是否存在蝴蝶效应，并随后进行评分。从对照组和实验组中各选择 8 颗得分最高和最低的牙齿。检查裂纹形成并分为 4 种不同类型的裂纹。使用维氏硬度试验进行显微硬度测试。根尖部蝴蝶效应的发生率较高，有蝴蝶效应的牙本质在近远中向更硬。有蝴蝶效应的中、根尖部比冠部更硬。对照组和实验组的牙本质硬度无显著差异。只有实验组出现裂纹，呈颊舌向分布，且 1 型和 2 型裂纹发生率较高。下颌前磨牙的蝴蝶效应从冠部向根尖部增加，硬度也随之增加。有蝴蝶效应的根内牙本质出现更多的颊舌向裂纹，其中大多数为 1 型和 2 型裂纹。有蝴蝶效应的下颌前磨牙的根可能更容易发生颊舌向的垂直根裂，尤其是在根管治疗后。因此，在根管预备过程中应特别注意不要使器械过载。
