Effects of age on secondary dentine mineralization and resin bonding capacity

Abstract

Objectives The aim of the study was to evaluate the mineralization and resin bonding capacity of coronal secondary dentine at various ages. Materials and Methods The mineral to matrix ratio (M) of mandibular incisor coronal sections classified in three age groups (I:21-40y/n=7, II: 41-60y/n=5, III: 61-80y/n=7) were measured by Fourier transform infrared microscopy (FTIRM), at incisal (MC) and pulpal (MP) secondary dentine and at primary dentine (MR). Then, the difference between MC-MP normalized by the corresponding MR was calculated (NM) per specimen. The bonding capacity of a resin composite to paired occlusal secondary and primary dentine cross-sections, mediated by a self-etch adhesive, was assessed in mandibular molars of I and III age groups (n=10/location and age) by a shear test (SBS). Statistical analysis was performed by two-way (M, SBS) and one-way (NM) ANOVA plus post-hoc tests (a=0.05). Results In the oldest age group (III), MC demonstrated significantly highervalues than MR. MP was significantly lower than MC, MR in all age groups, with the least differences observed in group III. No significant differences in MP were observed among age groups. NM values significantly increased with age. SBS showed insignificant differences between primary (all age groups) and secondary dentine (I group). Group III manifested the lowest SBS on secondary dentine. Conclusions Secondary dentine in older age groups showed higher mineralization, reducing the bonding capacity of a mild self-etch adhesive. Clinical Relevance Considering the highest mineralization and lowest bonding capacity of self-etch adhesives to older secondary dentine, more aggressive adhesive treatments applied selectively on the secondary dentine of deep cavities may be proposed for management of deep cavities.