Analytical investigation of salivary calculi, by mid-infrared spectroscopy

Abstract

Sialolithiasis is common in salivary glands, especially in the submandibular and parotid ducts. X-Ray diffractometry was the principal technique used for their analysis, sometimes associated with scanning electron microscopy. Hydroxyapatite was the most frequently described constituent, in association with whitlockite and other calcium phosphates as brushite or octocalcium phosphate. Proteic matter was detected, as mucoproteins, albumin, nucleoproteins or as degenerative bacterial matter. This study presents the identification of constituents by mid-infrared spectrometry of 74 sialoliths. Their successive layers are analyzed from their crust to the nucleus, using absorbance measurements. Spectra are compared with reference mixtures of two or more constituents. Approximately 99% of sialoliths are constituted of calcium phosphates, under carbonated forms. More than three-quarters contain proteins, in which mucins represent the majority and albumin is found in 10% of all the specimens. Only 7% calculi are an association of two constituents, 66% are made of three and 27% have four or more components. For the 74 studied sialoliths, no specimen contains hydroxyapatite; but they are composed of carbonate apatites with irregular microcrystallized forms, even if proteins are present. Some of them have a pure protein nucleus, surrounded by carbonate apatite layers; the other stones are made of internal layers of apatites and covered with a dense and varnished crust of proteins.

A comprehensive analysis of sialolith proteins and the clinical implications

“…Teymoortash et al [18] analyzed sialoliths from Wharton's duct (a duct of the submandibular salivary gland) and discovered that the organic materials were predominantly concentrated in the outer shell of the stones and their components were glycoproteins, mucopolysaccharides, lipids, and cellular detritus (Phospholipids). Considerable research carried out by several groups such as Sabot et al in 2012 [19]; Szalma et al 2012 [20]; Faklaris et al 2013 [21]; and Kraaji et al 2014 [22]) have also advanced our understanding of stone architecture by showing that some can have a pure protein nucleus surrounded by mixed organic and carbonate apatite layers; whereas others can have internal layers of apatite covered by a dense and varnished crust of proteins and other organic compounds. In addition, Yiu et al [23] and Ho et al [24] recently reported that bone forming mechanisms involved in the early stages of kidney stone development and arterial calcification also require the participation of proteins and transcription factors.…”

Computational fluid dynamics analysis of salivary flow and its effect on sialolithogenesis

“…It has been reported that round stones often occur during the early phase of sialolithiasis, are generally small in size and shape, and are composed of a fairly round mineralized core surrounded by few concentric layers (Sabot et al , 2012). Owing to their high tendency for rolling and low strength of fixation to the ductal wall, round sialoliths are considered easily removable by surgical procedures (Yu et al , 2005; Luers et al , 2011).…”

“…The formation and development mechanisms of calculi have been explored, mainly from a microperspective, since the beginning of the 19th century (Sabot et al , 2012). Calculi development in the salivary extraglandular system frequently causes salivary gland obstruction, which manifests as pain and swelling (Jardim et al , 2011).…”

“…Generally, the etiologies of sialolith retention can be divided into morpho-anatomic (Nagra et al , 2010) and saliva composition factors (Grases et al , 2003). These, in combination with other physiologic and physical factors, shape salivary calculi into fairly round micronuclei surrounded by concentric circled layers consisting of mucin and various other protein and mineral constituents, especially apatites (Sabot et al , 2012). …”

Composition and morphological characteristics of sialoliths

“…Detailed knowledge of the composition of the sialoliths can contribute to a further understanding of the formation mechanism and possibly can provide the basis for dissolution or prevention of stone recurrence. Studies on the structural characterization of sialoliths include the use of FTIR spectroscopy, Raman microspectroscopy, thermal analysis, mass spectroscopy, X‐ray diffraction and X‐ray photoelectron spectroscopy . Since Lustman suggested his hypothesis that bacterial involvement in the etiology of sialoliths, the microstructural characterization of sialoliths through scanning electronic microscopy have gained considerable attention .…”