The Degradation of Resin Materials Bonded to Dentine in the Root Canal by the Activation of Matrix Metalloproteinases

Abstract

Despite all the improvements resin based adhesive dental restorative materials have gone through in the last two decades, leakage in the resin-dentine interface is still a major limitation of resin based dental restorative materials. Dentine matrix metalloproteinases have been associated with this leakage through their involvement in the proteolytic degradation of the resin-dentine hybrid layer. The inhibitory effect of chlorhexidine on this enzymatic activity is well established. Bioactive glass materials can also reduce the resin-dentine interface leakage through biomimetic remineralisation of the dentine.

In this study the commercially available self-adhesive self-cure resin cement RelyX^TM Unicem Aplicap^TM was modified by incorporating chlorhexidine and Bioglass 45S5 into
the cement composition.

The evaluation of the physical properties of the modified cement has shown that the original physical properties of the RelyX^TM Unicem Aplicap^TM cement were not adversely affected by these modifications.

One hundred and fifty dentine specimens were obtained from human permanent single-rooted teeth and restored with the test cements. The test cements’ push-out bond strength was measured and statistically analysed after ageing the specimens in artificial saliva for one week and after nine months. The matrix metalloproteinases activity was
also quantified after each storage period.

The study results showed that incorporating chlorhexidine and Bioglass 45S5 jointly or separately into the composition of RelyX^TM Unicem Aplicap^TM did reduce MMP-2 activity after the short- and long-term storage. It was also shown by the results of this work that incorporating chlorhexidine and Bioglass 45S5 jointly, and chlorhexidine separately into the composition of the cement also reduced MMP-9 activity after short and long-term storage.

Statistical analyses of the test results has shown that incorporating chlorhexidine and Bioglass 45S5 into the RelyX^TM Unicem Aplicap^TM cement composition significantly preserves the push-out bond strength after up to nine months of storage (p=0.02). This indicates that incorporating chlorhexidine and bioglass into the composition of RelyX^TM Unicem Aplicap^TM can in the long-term preserve the strength of the bond formed between the cement and the dentine.

Date of Award	2017
Original language	English
Supervisor	Sarah Jones (Supervisor), William Saunders (Supervisor), Mervyn Lyons (Supervisor) & Graham Chadwick (Supervisor)