변위 허용 정도에 따른 복합레진 중합수축력의 변화

Abstract

As a tooth restoration material, the composite resin undergoes polymerization shrinkage, and polymerization shrinkage generates polymerization shrinkage force on the teeth under confinement due to bonding to cavity walls. Clinically, polymerization shrinkage and shrinkage force can cause debonding, marginal gap formation, microleakage, secondary dental caries, post-operative hypersensitivity, and cuspal deflection. In this study, especially with regard to cuspal deflection, the author investigated how the polymerization shrinkage forces of composite resins change with change in deflection. Five composites, SDR® (Dentsply Caulk, Milford, DE, USA), EcuSphere-Shape (DMG, Hamburg, Germany), Tetric N-Ceram® Bulk Fill (Ivoclar Vivadent, Schaan, Liechtenstein), CLEARFIL™ AP-X (Kuraray Noritake Dental Inc., Sakazu, Kurashiki, Okayama, Japan), and Filtek™ Z350 XT (3M Dental Products, St Paul, MN, USA), were tested in this experiment. The polymerization shrinkage forces of the composites were measured using a custom-made tooth deflection-mimicking device and software (R & B Inc., Daejon, Korea). In all measurements, six modes were tested, comprising maximum-deflection, zero-deflection, and four deflection-controlled modes. For each deflection mode, the shrinkage forces were recorded continuously every 0.1 for 180 s. Polymerization shrinkage and flexural modulus were also measured. Eight specimens of each material were allocated for each test. For each material, six groups of shrinkage force values were compared using one-way ANOVA and Tukey's post hoc tests at a 95% confidence level. The polymerization shrinkage force of each material in each of the six deflection modes was analysed with 95% confidence using one-way ANOVA and Tukey's post hoc tests. The relationship between the force measured in the six deflection modes and the linear polymerization shrinkage and flexural modulus was analysed with 95% confidence using Pearson’s correlation analysis. For each material, the following held true: the shrinkage force was highest in zero-deflection mode, the force decreased as deflection increased, and the smallest force appeared in maximum-deflection mode (P<0.05). There was a high negative correlation between allowable deflection and shrinkage force in all materials. Polymerization shrinkage forces and the differences in such forces between composite resins decrease with increasing cuspal deflection. When high deflection is expected, controlling composite volume with a base material or use of a layer filling technique are more practical than trying to choose a composite with low polymerization shrinkage force.