Влияние ориентации призм края кариозной полости на распределение напряжений в эмали

Abstract

Under the functional load on teeth the surface enamel is exposed to internal stresses and deformations. Further, the load is transmitted to the prisms, and then is redistributed to the morphological structure of the tooth. In carious enamel on the edge of defect with filling material the orientation of prisms change, which leads to disruption of the internal stress distribution. The aim of the research was to study the stresses in enamel in the formation of the edge of carious cavity with a different course of prisms. Methods. The finite element models were built with computer simulation. In the center of the test tooth it was simulated the vertical unidirectional load of 100 MPa. It was calculated the tension in the enamel of intact tooth when the edge of the enamel was formed in the form of direct and inverse cone. The characteristic of the stress state was expressed by the von Mises equivalent stress in MPa. Results. In intact teeth in the place of vertical load the maximum stress of enamel (74.2 MPa) occurs. In the contact zone of the restorative material with the edge of the enamel in teeth where the enamel edge of I class carious cavity are formed vertically without skew, the maximum stress from 220.0 to 241.5 MPa occurs. When the edge of the enamel is formed in the form of an inverted cone the beams of enamel prisms are cut at their course so the restorative material contacts with the side surface of prisms, the maximum stress in the surface enamel occurs in the contact zone (246.1-290.9 MPa). The most favourable state of stress in the enamel occurs in the formation of the edges in the form of direct cone, when prisms intersect transversely -121.6-162.1 MPa. Conclusions. The lowest stress, in the tooth enamel in the formation of I class Black cavities, occurs under the load on the physiologically oriented course of enamel prisms, transversely to their axis. This is achieved by the formation of a direct cone in the enamel edge of carious cavity.