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The fraction of organic matter present affects the fragmentation behavior of sialoliths; thus, pretherapeutic information on the degree of mineralization is relevant for a correct selection of lithotripsy procedures. This work proposes a methodology for in vivo characterization of salivary calculi in the pretherapeutic context. Sialoliths were characterized in detail by X-ray computed microtomography (μCT) in combination with atomic emission spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Correlative analysis of the same specimens was performed by in vivo and ex vivo helical computed tomography (HCT) and ex vivo μCT. The mineral matter in the sialoliths consisted essentially of apatite (89 vol%) and whitlockite (11 vol%) with average density of 1.8 g/cm3. In hydrated conditions, the mineral mass prevailed with 53 ± 13 wt%, whereas the organic matter, with a density of 1.2 g/cm3, occupied 65 ± 10% of the sialoliths’ volume. A quantitative relation between sialoliths mineral density and X-ray attenuation is proposed for both HCT and μCT.

Lithotripsy methods show relatively low efficiency in the fragmentation of sialoliths compared with the success rates achieved in the destruction of renal calculi. However, the information available on the mechanical behavior of sialoliths is limited and their apparently tougher response is not fully understood. This work evaluates the hardness and Young’s modulus of sialoliths at different scales and analyzes specific damage patterns induced in these calcified structures by ultrasonic vibrations, pneumoballistic impacts, shock waves, and laser ablation. A clear correlation between local mechanical properties and ultrastructure/chemistry has been established: sialoliths are composite materials consisting of hard and soft components of mineralized and organic nature, respectively. Ultrasonic and pneumoballistic reverberations damage preferentially highly mineralized regions, leaving relatively unaffected the surrounding organic matter. In contrast, shock waves leach the organic component and lead to erosion of the overall structure. Laser ablation destroys homogeneously the irradiated zones regardless of the mineralized/organic nature of the underlying ultrastructure; however, damage is less extensive than with mechanical methods. Overall, the present results show that composition and internal structure are key features behind sialoliths’ comminution behavior and that the organic matter contributes to reduce the therapeutic efficiency of lithotripsy methods.

This article presents a detailed study of the microstructure of Iberian expanded clay lightweight aggregates (LWA). Other than more commonly used mercury porosimetry (MP) and water absorption methods, the experimental study involves optical microscopy, scanning electron microscopy (SEM), and microtomography (μ-CT). Pore connectivity and how it is deployed are shown to some degree, and the pore size spectrum is estimated. LWA are in general characterized by a dense outer shell up to 200 μm thick, encasing an inner cellular structure of 10–100 times bigger pore size. Aggregate pore sizes may span from some hundreds of nanometers up to over 1 mm, though the range of 1–25 μm is more typical. A noteworthy fraction of these pores is closed, and they are mainly up to 1 μm. It is also shown that macropore spatial arrangement is affected by the manufacturing process. A step forward is given to understanding how the outer shell and the inner pore network influence the mechanical and physical LWA properties, particularly the density and water absorption. The joint consideration of μ-CT and SEM seems to be the most appropriate methodology to study LWA microstructure. MP analysis is likely to distort LWA pore spectrum assessment.

A.J. Anjos*, P. Nolasco**, J.M. Aquino Marques*, F. Cabrita***, M.F.C. Pereira****, A.P. Alves de Matos***** and P.A. Carvalho** *Faculdade de Medicina Dentaria, Universidade de Lisboa, Cidade Universitaria, 1649-003 Lisboa, Portugal **ICEMS, Instituto Superior Tecnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal ***Servico de Cirurgia Maxilo-Facial, Centro Hospitalar de Lisboa Central, R. Jose Antonio Serrano 1150-199 Lisboa, Portugal ****CEGPIST, Departamento de Engenharia Civil, Arquitectura e Georrecursos, Instituto Superior Tecnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal *****Anatomia Patologica, Centro Hospitalar de Lisboa Central - HCC, Rua da Beneficencia 8, 1069-166 Lisboa; Centro de Estudos do Ambiente e do Mar (CESAM/FCUL) - Faculdade de Ciencias da Universidade de Lisboa and Centro de Investigacao Interdisciplinar Egas Moniz (CiiEM), Quinta da Granja , Monte de Caparica, 2829-511 Caparica, Portugal The oral cavity is susceptible to several calcifications such as salivary calculi (sialoliths), dental calculus (tartar) and tonsillar concretions (tonsilloliths). Although several individual studies had been already carried out, a comprehensive morphological and elemental comparison between them is still missing. Sialoliths are most commonly found in the submandibular glands [1] and are composed of regions rich in Ca and P minerals, namely hydroxyapatite, whitlockite and brushite [1], and regions consisting of organic matter with high-sulphur content [1]. These regions are organized in alternating concentric layers [1]. Several bacterial species have also been identified in sialoliths microstructure showing that infection occurs recurrently throughout the stone formation [2]. Generally, tartar presents an inorganic structure rich in Ca and P minerals, such as brushite, octacalcium phosphate, hydroxyapatite and whitlockite, and an organic matrix, mainly constituted by aerobic bacteria and yeast or just anaerobic bacteria [3]. Tonsilloliths occur most commonly on the crypts of the palatal tonsils and are composed of a mixture of organic matter, namely bacterial cells and epithelial debris, as well as inorganic material rich in Ca and P minerals such as hydroxyapatite. Volatile sulphur compounds produced by anaerobic bacteria are usually associated to these, in general, innocuous structures [4]. The current study involved the ultrastructure and chemical characterization of the calcified structures by scanning electron microscopy (SEM) combined with energy dispersive spectroscopy carried out with a JEOL JSM 7001F instrument with an INCA pentaFetx3 Oxford spectrometer operated at 15 kV. Higher resolution characterization has been performed by transmission electron microscopy (TEM) using a H8100 Hitachi instrument operated at 200 kV. SEM samples were prepared following metallographic procedures [1], whereas TEM samples were obtained following standard biological sample preparation procedures [5]. The results show that sialoliths present the most complex structure, with a central core surrounded by concentric layers, while tartar and tonsilloliths do not have a distinctive architecture (Figures 1 (a), 2 (a) and 3 (a). At higher magnifications, layered structures, as well as crystals could be found in sialoliths and tartar (Figures 1 (b) and 2 (b). Bacteria were common in all the calcified structures, although in tonsilloliths their abundance is higher (Figure 3 (b)). All calcifications have similar elemental constitution, with Ca and P, indicating the presence of calcium phosphates (Figures 1 (c), 2 (c) and 3 (c). Sulphur was also found associated with the organic matter in sialoliths and tonsilloliths, though the amounts found in the latter were much smaller than initially expected. Based on the similarities found, new correlations between these calcification will be available. For instance, the mineralization process described in tartar can help understand the similar processes occurring in sialoliths and tonsilloliths, while the association between bacteria and sulphur in tonsilloliths can be a clue for their presence in

Several theories have been put forward regarding the aetiology and pathogenesis of salivary calculi, although a comprehensive understanding of the nucleation and growth mechanisms involved in the formation of these structures is still lacking.In general, sialoliths present one core partially or highly mineralized surrounded by concentric layers of organic and mineralized matter that alternate in succession following a chronologic sequence. The layers consist of fine mineralized strata intercalated with fine organic ones and threaded globular structures with variable degrees of mineralization.The exact mechanism involved in the genesis of sialoliths remains largely unknown, theories defending an initial organic nidus or an initial precipitation of minerals, with subsequent deposition of organic and inorganic layers, can be found in the literature. Nevertheless, it remains object of discussion the etiologic factors responsible for the formation of the first nidus or the initial precipitation, since infection, inflammation of the gland, viscous nature of the mucous secretions or naturally existing sialomicroliths have all have been implicated.Aiming at an exhaustive systematization of salivary calculi morphogenesis, their morphology has been studied by micro-computed tomography (bCT) and scanning electron microscopy (SEM). CCT studies were done on as-extracted dried samples using uCT SkyScan 1172 instrument with a 1.3 Megapixel camera, operated at the maximum available power of the source (10W). Radiographs acquisition was performed with a rotational step in the 0.70-1° range, until a maximum of 180º, with an exposure time in the 3.1-5 s range. Microscopy observations were carried out with backscattered electron (BSE) signals using a JEOL JSM 7001F operated at 15 kV, samples were previously prepared following metallographic procedures.The submandibular and parotid calculi investigated presented similar growth patterns, which can follow either concentric (Figure 1) or perturbed-growth typologies (Figure 2), although in most situations a gradation between them has been found. Nevertheless, a single well-defined core constituted by material with low mineralization was frequently present, supporting the nucleation hypothesis of an initial organic nidus.The combination of TCT with SEM enabled a comprehensive characterization of the sialoliths: (i) the former technique allowed for a precise localization of the core and other morphological features within the calculus volume, while (ii) investigation of details at higher resolution could be achieved with the latter method. However, due to the friable nature of the sialoliths, handling during sample preparation results often in material loss (compare (a) and (b) in both Figures).The work was carried out with financial support of the Portuguese Foundation for Science and Technology through PTDC/SAU-ENB/111941/2009 and PEst-OE/CTM-UI0084/2011 grants.