The use of composite restorative materials is established due to continuing
improvements in the materials and restorative techniques.
Composite resins are widely used for the restoration of cervical lesions because of
esthetics, good physical properties and working time. There are several types of cavity
design for class V composite resin filling, but inappropriate cavity form may affect
bonding failure, microleakage and fracture during mastication.
Cavity preparations for composite materials should be as conservative as possible. The
extent of the preparation is usually determined by the size, shape, and location of the
defect. The design of the cavity preparation to receive a composite restoration may vary
depending on several factors.
In this study, 5 types of class V cavity were prepared on each maxillary central
incisor. The types are; 1) V-shape, 2) round(U) shape, 3) box form, 4) box form with
incisal bevel and 5) box form with incisal bevel and grooves for axial line angles.
After restoration, in order to observe the concentration of stress at bonding surfaces
of teeth and restorations, developing a 2-dimensional finite element model of labiopalatal
section in tooth, surrounding bone, periodontal ligament and gingiva, based on the
measurements by Wheeler, loading force from direction of 45 degrees from lingual side
near the incisal edge was applied.
This study analysed Von Mises stress with SuperSap finite element analysis
program(Algor Interactive System, Inc.).
The results were as follows : 1. Stress concentration was prevalent at tooth-resin
bonding surface of cervical side on each model.
2. In model 2 without line angle, stress was distributed evenly.
3. Preparing bevel eliminated stress concentration much or less at line angle.
4. Model with round-shape distributed stress concentration more evenly than box-type
model with sharp line angle, therefore decreased possibility of fracture.
5. Adding grooves to line angles had no effect of decreasing stress concentration to the
area.
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