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一、引言 1896年,G.V BLack在一个金箔充填的根管内插入一根金螺纹桩作为义齿的固位,桩冠开始应用于临床。从此,随着新技术的不断发展,人们越来越多地用桩核修复无髓牙,尤其是牙体严重缺损,如残根、残冠等。但是,由于无髓牙硬组织脱水,牙本质小管水分丧失而失去弹性,牙齿变脆;根管治疗时机械性制备进一步削弱了牙齿硬组织;牙胶充填侧向压力过大,都使牙齿的抗折力降低。本文对桩核系统引起根折的原因进行综述。 二、不同设计的桩核系统在牙根内的应力情况 1.桩核系统在根管内的应力情况 人们用光弹法、有限元法等研究了桩核系统在根管内的应力情况,发现当根内无桩时,斜行压力及侧向压力集中在冠部和牙根的中1/3处,唇侧略大些,垂直压力下,压力集中在牙本质的颈部和冠部。根管内放置桩核以后,根内的压力模式发生了改变。斜行和侧方压力集中在唇侧颈部的牙根及牙槽骨以及舌侧桩孔末端牙根和根尖端1/3处牙槽骨处;垂直压力时,应力呈对称分布,主要集中于根面与根管壁夹角处的牙本质中,其应力以剪切力和压应力为主。载荷的大部分由核传到牙根(根面),小部分由桩传到桩孔底部(根尖),形成应力集中区,尤其是桩核交界的舌侧,是应力最集中的区域。
I. INTRODUCTION In 1896, G.V BLack inserted a gold thread post as a denture in a gold-filled canal, and the crown began to be used clinically. Since then, with the continuous development of new technologies, more and more people use post-and-core restoration of non-myelinated teeth, especially for serious dental defects such as residual roots and residual crowns. However, due to dehydration of pulpless pulp tissue, loss of elasticity and loss of elasticity of the dentinal tubules, teeth become brittle; mechanical preparation during root canal treatment further weakens the hard tissue of the teeth; lateral pressure of the filling of the gums is too large, Reduced resistance to stress. This article reviews the causes of root fracture caused by post-core system. Second, the different design of the stress in the root system of post-core system 1. Stress in the root canal of the post-core system People used the light-bomb method and finite element method to study the stress in the root canal of the post-core system. When no root in the pile, the oblique pressure and lateral pressure concentrated in the crown and root of 1/3, slightly larger lip side, vertical pressure, the pressure concentrated in the dentin neck and crown. After placing the post core in the root canal, the pressure pattern inside the root changed. Oblique and lateral pressure concentrated in the labial and alveolar bone of the lip side of the mouth and apical end of the root and apical root tip 1/3 alveolar bone; vertical stress, the stress was symmetrical distribution, mainly in the root Surface and root canal at the corner of dentin, the stress to shear stress and stress-based. Most of the load is transmitted from the nucleus to the root (root surface), and a small part of the load is transmitted from the pile to the bottom of the pile hole (apical root) to form the stress concentration area, especially the lingual side of the junction of the pile core, which is the stress concentration area.