Structural characterization of salivary calculi

Abstract

The microstructure, local chemistry, crystallography and mechanical properties of submandibular sialoliths have been characterized by powder X-ray diffraction, electron microscopy combined with X-ray spectroscopy and ultramicro-indentation assays. The sialoliths presented highly mineralized, lamellar and globular regions. The fairly homogeneous mineralized regions are constituted by hydroxyapatite, whitlockite and brushite. Lamellar regions consisted of alternating layers of mineralized material and organic matter, with a concentric morphology pointing to a chronologic cyclic formation. Globular regions are composed of organic matter globules presenting high sulphur content. The Young modulus and hardness increased with the mineralization degree of the sialoliths. Nevertheless the relatively high amounts of compliant and soft organic matter present in the sialoliths may play a major role in the relatively low success of shock wave therapeutics for sialolith fragmentation.

Structure and Growth of Sialoliths: Computed Microtomography and Electron Microscopy Investigation of 30 Specimens

“…The mineral components of sialoliths consist essentially of (carbonated) calcium phosphates, whereas the organic components consist of proteins, glycoproteins, mucopolysaccharides, and lipids (Boskey et al, 1981; Ashby, 1995; Kinoshita et al, 2008; Sabot et al, 2012). In addition, the organic matter has been shown to present a significant amount of sulfur (Alves de Matos et al, 2007; Nolasco et al, 2012) the origin of which has not been clearly evaluated. A relatively high fraction and fine distribution of organic matter in sialoliths is likely to enhance their mechanical toughness, which would contribute to a reported resistance to lithotripsy (Escudier, 2001; Escudier et al, 2003; Capaccio et al, 2004; Zenk et al, 2004; Schmitz et al, 2008; Iro et al, 2009).…”

“…Globules of organic matter have been found on external surfaces (Lustmann & Shteyer, 1981; Giray et al, 2007), fracture surfaces, and polished cross-sections of sialoliths (Alves de Matos et al, 2007; Nolasco et al, 2012). When dispersed throughout the internal mineralized structure of the sialoliths, the organic globules present interfaces showing self-similarity at different scales (Alves de Matos et al, 2007).…”

“…The mineral components of sialoliths consist essentially of~carbonated! calcium phosphates, whereas the organic components consist of proteins, glycoproteins, mucopolysaccharides, and lipids~Boskey et al, 1981;Ashby, 1995;Kinoshita et al, 2008;Sabot et al, 2012!. In addition, the organic matter has been shown to present a significant amount of sulfur~Alves de Matos et al, 2007;Nolasco et al, 2012! the origin of which has not been clearly evaluated.…”

“…A relatively high fraction and fine distribution of organic matter in sialoliths is likely to enhance their mechanical toughness, which would contribute to a reported resistance to lithotripsy~Escudier, 2001; Escudier et al, 2003;Capaccio et al, 2004;Zenk et al, 2004;Schmitz et al, 2008;Iro et al, 2009!. However, only limited information exists on the fraction and distribution of the organic matter~Anneroth et al, 1979; Escudier, 2001; Alves de Matos et al, 2007!. Globules of organic matter have been found on external surfaces~Lustmann & Shteyer, 1981;Giray et al, 2007!, fracture surfaces, and polished cross-sections of sialoliths Alves de Matos et al, 2007;Nolasco et al, 2012!. When dispersed throughout the internal mineralized structure of the sialoliths, the organic globules present interfaces showing self-similarity at different scales~Alves de Matos et al, 2007!. The invariant scaling concept of fractal analysis can be empirically used to describe features that are self-similar over extended, but finite, scales, with applications ranging from the characterization of metallic microstructures~Hornbogen, 1989! to pharmacokinetic investigations~Pereira, 2010!.…”