The effect of elastic modulus of posts on coronal restorations

Abstract

Objectives: Root canal posts with modulus of elasticity similar to dentine have been advocated to restore severely broken-down anterior teeth. It is unknown if the inherent flexibility of these posts could affect the maintenance of marginal integrity of the final restoration under mastigatory loads. The objective of this study was to examine the leakage pattern of full-coverage restorations retained with either metallic or fiber-reinforced resin post after simulated occlusal loading. Methods: 36 maxillary central incisors were root canal-treated, and restored with a post-and-core supported crown with 1.5mm ferrule. The experimental group (n=12) was restored with fiber-post (EasyPost Lux), while the comparison group (n=12) was with metallic post (ParaPost); both were subjected to 120,000 cyclic loads up to 70N whilst being immersed in 2% Basic Fuschin. One control group (n = 12, similarly restored with fiber-post) was immersed but not loaded. Transverse serial cross-sections were cut at 1mm intervals from the tooth-core interface towards the apex. Hi-resolution digital photographs were taken for examining the leakage on the buccal, mesial, palatal and distal aspects along the depth of the post. Leakage was scored on a 5-point measuring scale: 0 – no leakage; Dye penetration 1 – luting cement interface; 2 – into superficial half of dentine; 3 – into the inner half of dentine; 4 – into the post space. Results: There was significant difference in the amount of leakage between the two experimental groups with the fiber-post group showing greater amounts of leakage than the control and the ParaPost group (ANOVA, Holm-Sidak pair-wise multiple comparison P < 0.05). Conclusion: Within the limitations of this study, the marginal integrity of the coronal restoration was affected by the modulus of elasticity of the post during repeated stresses. The use of fiber posts in teeth with minimal coronal tooth structure may require further evaluation.