Investigating the surface topography of human acellular and cellular tooth cementum by atomic force microscopy

Introduction: Dental cementum plays a key role in maintaining the health and functional integrity of teeth throughout an individual's life. While different cementum types are distinguished according to location and function, their specific properties are not yet fully understood. Objective: The study aimed to compare the structural properties of different types of tooth cementum by analysing their surface texture using tapping mode atomic force microscopy (TM-AFM). Methods: Transverse and longitudinal sections of five anterior teeth extracted from four male individuals were prepared and analysed by TM-AFM (Core AFM) both with and without hydrochloric acid etching. The TM-AFM measurements were further analysed using the Gwyddion software to determine the roughness parameters (root mean square of height irregularities and mean roughness). Results: The acid-etched sections exhibited distinctive features with regard to fibre structure and orientation compared to the unetched sections, with fundamental differences between acellular and cellular cementum. In contrast to acellular extrinsic fibre cementum (AEFC), cellular intrinsic fibre cementum (CIFC) showed increased roughness values after acid etching, with some variability, both between teeth and between subjects. The relative percentage difference (RPD) between the cementum types varied between 11.4 % in unetched transverse sections and up to 89.8 % in etched sections. The AEFC images revealed finely branched fibres between radial Sharpey's fibre bundles. Conclusion: Our results show that TM-AFM imaging combined with acid etching is a suitable technique for characterising the surface texture of different types of tooth cementum.