Effect of occlusal loading and mechanical properties of resin composite on stress generated in posterior restorations

摘要

Purpose: To investigate the effect of the occlusal load condition in association with the mechanical properties of resin composite, expressed by elastic modulus and post-gel shrinkage, on stresses in a premolar restored with various composites. Methods: Five resin composites (4 Seasons, Beautifil II, Filtek LS, Filtek Z250, and Z100) indicated for restoring posterior teeth were tested. Elastic modulus was measured using Knoop indentation tests (n=5). Post-gel shrinkage was measured with strain gouges (n=10). Finite element analysis was used to calculate the stresses in a twodimensional pre-molar model under four conditions: (Wc, without occlusal contact, representing stresses due to composite shrinkage only, Ct: contact generated between enamel of restored tooth and antagonist tooth; Cm: contact on tooth/composite restoration margin; Cc: stable centric contact on the composite restoration). Results: Elastic modulus varied between 12.6 (Filtek LS) and 21.5 (Z100) GPa; post-gel shrinkage varied between 0.11 (Filtek LS) and 0.96 (Z100) vol%. Composites with higher elastic modulus and post-gel shrinkage increased stress in the restored tooth. Occlusal contact on the tooth/composite restoration margin increased the stresses around the margin of the restoration. Stable centric contact on the restoration resulted in better stress distribution. CLINICAL SIGNIFICANCE: Stresses in the restored tooth increased with increasing elastic modulus and post-gel shrinkage. Contact close to the restoration margin increased the local stress concentration regardless of composite properties. Occlusal adjustment after posterior restoration to prevent contact at the margin is important to improve stress distribution and preserve the restoration integrity.