Non-Destructive 3D Quantitative Analysis of Residual Periodontal Ligament on Extracted Human Premolars Using Intraoral Scanning.

Intentional tooth replantation is a valuable treatment for preserving natural teeth with endodontic lesions. Its success critically depends on the viability and structural integrity of the residual periodontal ligament (PDL). Traditional evaluation methods, such as histological sectioning or two-dimensional photography, are either destructive or limited by projection errors. To address these limitations, this protocol presents a non-destructive, quantitative method for evaluating residual PDL using high-precision intraoral scanning. Extracted teeth were stained to visualize the PDL tissue and three-dimensionally scanned to generate high-fidelity digital models. The data were analyzed using reverse engineering software, where a region of interest was defined, and residual PDL coverage was quantified via color thresholding. This approach calculated the true 3D coverage area of the PDL without compromising the biological sample. To evaluate the sensitivity and utility of this protocol, it was applied to compare minimally invasive (MI) extractions using periotomes against conventional forceps extractions. Digital analysis revealed that the MI method preserved significantly more PDL tissue (61.99%) than the conventional method (50.46%). Furthermore, a subsequent cell viability assay corroborated the digital findings, demonstrating significantly higher metabolic activity in the MI group. Ultimately, this work establishes a proof-of-concept workflow for ex vivo quantitative PDL assessment, providing a robust methodological basis for comparing extraction techniques in preclinical research.