Demineralization of tooth enamel following radiation therapy; An in vitro microstructure and microhardness analysis

Objective: The objective of this study is to evaluate the effects of radiotherapy doses on mineral density and percentage mineral volume of human permanent tooth enamel. Materials and Methods: Synchrotron radiation Xray microcomputed tomography (SRμCT) and microhardness testing were carried out on 8 and 20 tooth samples, respectively. Enamel mineral density was derived from SRμCT technique using ImageJ software. Microhardness samples were subjected to Vickers indentations followed by calculation of microhardness and percentage mineral volume values using respective mathematical measures. Data were analyzed using paired t-test at a significance level of 5%. Qualitative analysis of the enamel microstructure was done with two-dimensional projection images and scanned electron micrographs using μCT and field emission scanning electron microscopy, respectively. Results: Vickers microhardness and SRμCT techniques showed a decrease in microhardness and an increase in mineral density, respectively, in postirradiated samples. These changes were related to mineral density variation and alteration of hydroxyapatite crystal lattice in enamel surface. Enamel microstructure showed key features such as microporosities and loss of smooth homogeneous surface. These indicate tribological loss and delamination of enamel which might lead to radiation caries. Conclusions: Tooth surface loss might be a major contributing factor for radiation caries in head-and-neck cancer patients prescribed to radiotherapy. Such direct effects of radiotherapy cause enamel abrasion, delamination, and damage to the dentinoenamel junction. Suitable measures should, therefore, be worked out to protect nontarget oral tissues such as teeth while delivering effective dosages to target regions

Vitamin C inhibits crystallization of struvite from artificial urine in the presence of Pseudomonas aeruginosa

ABSTRACT Background: Formation of struvite stones is associated with urinary tract infection by urease-producing bacteria. Biogenic crystal growth in natural and synthetic materials is regulated by the action of inhibitors, ranging from small ions, molecules to large macromolecules. Materials and Methods: We report the dynamics of in vitro crystallization of struvite in presence of vitamin C in synthetic urine using single diffusion gel growth technique. Sodium metasilicate gel of specific gravity 1.05 and the aqueous solution of ammonium dihydrogen phosphate were used as the medium for growing the struvite crystals. The crystallization process was induced by a urease positive struvite stone associated Pseudomonas aeruginosa to mimic the infection leading to stone formation. The grown crystals were characterized by ATR-FTIR and powder XRD. The surface morphology was analysed through FE-SEM for comparison between treatments. Results: We observed decrease in number, dimension, and growth rate of struvite crystals with the increasing concentrations of vitamin C. Crystals displayed well-defined faces and dendritic morphology of struvite in both control and biogenic systems. Conclusion: The results strongly suggest that, vitamin C can modulate the formation of struvite crystals in the presence of uropathogenic bacteria.

Association of serum biochemical panel with mineralogical composition of kidney stone in India

Purpose: The aim is to study the diversity in the composition of kidney stones and its association with the basic biochemical metabolic panel in patients with kidney stone disease (KSD). Methods: A cross-sectional prospective study enrolling consecutive patients with KSD attending a tertiary care hospital in Mangalore (India) was undertaken. Mineral compositions of kidney stones were analyzed using attenuated total reflection-Fourier transform infrared spectroscopy. Kidney stones were classified into different groups according to the composition. Metabolic status was assessed to analyze possible association with the kidney stone. Results: A total of 369 patients (male 305 and female 64) in the age group of 43.05 ± 14.3 years were included in the study and showed a high diversity of kidney stone types with >50% with mixed compositions. A significant association was found between pure stone type and gender as well with age group (P < 0.001). Serum calcium levels in the calcium oxalate stone formers were significantly higher (P < 0.001) than others. Similarly, uric acid stone formers showed higher random blood sugar, blood urea, uric acid, and serum creatinine levels (P < 0.001). Urine pH was also found to be a contributing factor for the stone formation (P < 0.001). Stone recurrence did not differ significantly concerning stone composition as well as metabolic status. Conclusion: The study reports a high diversity of the kidney stone types among patients. This finding highlights the increased cases of mixed stones that may be because of various lifestyle factors resulting in altered metabolic status. This finding warrants mechanistic studies to understand the etiology of stone formation. This will enable to develop novel noninvasive interventional strategies and proper preventive strategies to reduce the risk of KSDs.