Microarchitecture and Crystalline Composition: A Comprehensive Exploration of Salivary Gland Stones

Objective: To investigate the microarchitecture and crystalline composition of sialoliths and to explore their formation mechanisms.

Methods: Sixty-six sialolith samples (51 from the submandibular glands and 15 from the parotid glands) were retrospectively collected. Their diameter and quality were measured. Micro-computed tomography, scanning electron microscopy, and polycrystalline X-ray diffractometer (XRD) were utilized to determine their microstructure and crystalline composition.

Results: Stone diameter and weight averaged at 9.6 mm and 0.31 g, respectively. Submandibular stones showed larger size and weight than parotid stones. Microstructurally, the main stones were concentric (n = 51) or mixed (n = 15). Most concentric stones occurred at submandibular glands, while 80% of the mixed stones were parotid stones. Stone surface exhibited three microscopic structures: lamellar, grape-like, and porous, indicating their differences in mineralization process and composition. XRD revealed that all stones contained hydroxyapatite, with 57 containing whitlockite. Concentration of hydroxyapatite in concentric stones was significantly higher than that in mixed stones (p = 0.036) and correlated positively with stone diameter (p = 0.001). The microstructure and crystalline composition of multiple and recurrent stones were similar to that of single stones.

Conclusion: Sialoliths display pronounced diversity in microarchitecture and crystalline composition, reflecting the differences in mineralization process and local microenvironments among stones.