Ceramic Corrosion as a Result of Biofilm Colonization.

Objectives: The aim of this study was to determine whether bacterial biofilms play a role in the surface degradation of lithium disilicate dental ceramics.
Methods: Six discs (12.0 mm in diameter and 2.0 mm in thickness) were made from IPS e.max Ceram.
Each disk was polished to manufacturer specifications using recommended polishing kits.
Baseline data of each disk surface prior to exposure to biofilm were recorded using scanning electron microscopy (SEM) imaging. Each disk was then immersed in bacterial biofilm and inoculated for 80 days. Biofilm was prepared using saliva samples and subgingival swab cultures from a single donor. Disk samples were incubated in the anaerobic chamber (10% H2, 5% CO2, and balance N2) at 37°C and TSB medium was changed every 2 days. Bacterial growth was observed carefully using agar plating. After the 80 days inoculation period, surface characteristics of specimens were examined using scanning electron microscopy (SEM).
Results: This study revealed that all ceramic disks had topographical and microstructural surface changes to varying degrees after being immersed in bacterial biofilm biproducts for the 80 days period. SEM photographs showed surface destruction (pits increased in number and depth by surface area) in all disks.
Conclusions: The surface degradation of the ceramic disks in this study may be attributed to changes in local chemistry due to a fluctuating pH environment and mobile ions from the bacterial metabolic byproducts. Diffusion of mobile ions across depleted leach-layers may enhance the corrosion processes in dental ceramics. Therefore, biofilms may well change the local chemistry of the adjacent ceramic surface and thereby enhance corrosion processes.