Use of High-Frequency Ultrasound for the Correlation of Epithelial Rete Peg Variation

Objective: Rete pegs are projections of the oral epithelium into connective tissue. Their dimensions change during pathological conditions and may correlate with wound-healing status. Non-invasive, high-frequency ultrasound (US) may be able to capture these changes and aid in early detection of histopathological changes. The aim of this preclinical study is to correlate US images with histology and quantify epithelial layers at different tooth sites. Methods: Sagittal B-mode images of mid-facial and interproximal oral soft tissue sites were recorded in a preclinical minipig model using a linear array in second harmonic mode (12/24 MHz). Histology samples from the same locations were stained (hematoxylin and eosin), digitized and registered with US images. Manual annotations were used to measure distances D-1 (thickness of epithelium on histology vs. hyperechoic zone on US) and D-2 (sum of epithelial thickness and length of rete pegs on histology vs. sum of hyperechoic and hypoechoic zone on US) to statistically analyze them. Results: Ultrasonic-derived dimensions yielded a mean bias of-0.64 (55% coefficient of variance [COV]: -180 to +180 mu m) and-12 mu m (39% COV: -260 to +240 mu m) for D-1 and D-2, respectively. Individualized analysis of D-1 and D-2 by tooth type showed similar tends in the ability to differentiate between epithelium at different tooth locations, on both histology and US. Conclusion: Assessing soft tissue dimensions on a sub-millimeter scale using clinical imaging hardware is still a developing area. Future research might open doors for diagnosis of oral pathologies and abnormal wound healing, and may limit false-positive indications for biopsies.