Microscopic Observation of Morphology and Composition of Canine Calculus Using SEM, TEM and EPMA: A Case Study

Abstract

Dental calculus is one of the risk factors of periodontal diseases and tooth loss in humans and some animals. However, present authors noticed that calculus adhering to the canine surfaces, which naturally came off the jaws due to periodontal diseases, could be removed easily by hand with little breakage. Few studies on differences in physicochemical properties of calculus between humans and animals are available. Thus, the purpose of this study was to investigate calculus interface with the tooth surface in canine and its mineral characteristics for seeking the ease when removing canine calculus. Calculus specimens involving longitudinally cut surface of the calculus and tooth, and its back surface of the naturally detached from the tooth were observed using SEM. Elemental analysis of calcium (Ca) and phosphorus (P) was performed by EPMA on the cut surface from the top surface toward the bottom. Then the molar ratios of Ca/P were measured to estimate the mineral composition. Moreover, TEM observation was performed to characterize the morphology of calculus minerals. SEM observation showed that the naturally detached back surface was smooth, indicating no apparent breakage. In addition, an apparent gap without breakage of calculus at the interface was observed, which is rarely reported in human calculus. EPMA analysis provided various Ca/P molar ratios with a lower (1.0) to higher values (3.2-3.4). Ca and P contents observed in EPMA color images showed that the mineral content of the calculus near the bottom seemed to be lower than that in the inner body of the calculus. TEM observation revealed morphologically different types of the minerals; aggregated cubic substances, rod-like and spherical substances. A stronger radio-opacity was noted in rod-like and spherical substances compared to the cubic substances, suggesting the former was non-apatitic and the latter apatitic minerals.