Nature’s answer to sealing the skin barrier: characterization of dental enamel and root cementum

Objective: The human body has evolved to maintain homeostasis through the covering of skin and mucous membranes, which separate the internal environment from the harsh and variable external milieu. Few structures naturally penetrate these coverings, and teeth are the only exception in human beings. Dental enamel and root cementum at the cervical region is of interest since that area represents the interface between a tooth and gingival tissue. A better understanding of these features might give valuable insights for designing percutaneous implants. The aim of this study was to characterize dental enamel and root cementum at the cervical region of healthy human teeth by using atomic force microscopy (AFM). Field-emission scanning electron microscopy (FESEM) was used for comparison. Methods: Twenty five freshly extracted sound human maxillary first premolars extracted for orthodontic treatment reasons were included in the study. Five premolars were used for FESEM and twenty for AFM. The enamel surface on the buccal side of the tooth was analyzed in a narrow area, 1 mm coronal to the zenith of cementoenamel junction (CEJ). The cementum surface on the buccal side of the tooth was analyzed in a narrow area, 1 mm apical to the zenith of CEJ. The value of Ra and Rq was measured. Results: The gross appearance of the cervical enamel was characterized by overlapping wave-like layers. The border of each enamel layer was highly undulated and formed in most areas a distinct rounded step towards the underlying layer. The exposed surface of each enamel layer was relatively smooth with very shallow depressions of Tomes’ processes pits. The cementum was characterized by the position of the Sharpey fibers, generally present in one or both of two distinct ways; either they appear as projections above the general plane of the mineralizing front or as a depression in this front. The mean Ra and standard deviation in μm were: enamel, 0.46 ± 0.20; cementum, 0.65 ± 0.28. The mean Rq and standard deviation in μm were: enamel, 0.58 ± 0.22; cementum, 0.79 ± 0.32. There were statistically significant differences (P < 0.05) among Ra and Rq between enamel and root cementum. Conclusions: Dental enamel surface and root cementum surface at the cervical region showed a clear difference in topography. Enamel surfaces were slightly smoother than root cementum surfaces. The findings from the study of the morphology of teeth gave us valuable insights for designing percutaneous implants.