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.

Single-nucleotide polymorphisms of methylenetetrahydrofolate reductase gene in a South Indian cohort with nonsyndromic cleft lip with or without palate.

OBJECTIVE: Clefts of the lip, with or without cleft palate and cleft palate only, collectively called as orofacial clefts (OFCs) are one of the most common congenital malformations with varying degrees of penetrance and phenotype expressions. The aim of this study was to investigate the association between methylenetetrahydrofolate reductase (MTHFR) cytosine-to-thymine (c. 677 C>T), adenine-to-cytosine (c.1298 A>C) single- nucleotide polymorphisms (SNPs) and South Indian patients with the nonsyndromic cleft lip with or without palate (NSCL ± P). METHODS: A cohort consisting of 25 cases of NSCL ± P and 18 controls from a South Indian cohort were included in this case-control study. Genetic analysis of c.677C>T and c.1298A C polymorphisms in the MTHFR gene was carried out using Sanger sequencing and analyzed from chromatogram profiles. Data interpretation was done using statistical software MedCalc Statistical Software version 16.2 and the Statistical Package for the Social Sciences (SPSS version 22.0). RESULTS: DNA sequence analysis of the MTHFR gene revealed c. 677C>T and c. 1298A>C polymorphisms in 16% and 76% of NSCL ± P cases, respectively. Heterozygous variant in MTHFR c. 1298A>C polymorphism was found to be a significant risk factor (P = 0.0164) for NSCL ± P in South Indian ethnic population. c.677C>T polymorphism, in particular, was apparently dormant overall in the study population. These results offer certain novelty in terms of the distinctive pattern in SNPs of genotypes observed in the study. CONCLUSION: NSCL ± P is one of the most common and challenging congenital malformations with complex etiological basis. Common risk factors such as MTHFR SNPs, namely c.677C>T and c.1298A>C, are subjected to variations in terms of ethnic group, geographic region and micro/macro-environmental factors. Overall, our study has explored part of South Indian ethnic population and revealed a different and unique distribution of mutations in this sample population.

Spectroscopic analyses reveal radiotherapy-induced variations in elemental composition and crystallite properties of human permanent teeth enamel.

OBJECTIVE: To study the effect of radiation therapy on the structural and elemental composition of permanent teeth enamel in vitro. METHODS: Sections from 21 noncarious healthy human teeth were exposed to a cumulative radiation dose of 20-80 Gy. The sections were subjected to electron dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis to study the elemental composition, the ratio of inorganic and organic content, and the mineralization and crystalline properties of the hydroxyapatite crystal structure respectively. All measures were taken on specified areas of enamel surface before and after radiation exposure and compared. RESULTS: In FTIR and EDS studies, the calcium to phosphorus (Ca/P) and carbonate to phosphate (CO32-/PO3-4) ratios were significantly different (P < 0.05) in teeth sections exposed to 80 Gy, indicating the deterioration of inorganic calcium and phosphorous content. The XRD spectrum data showed loss of peaks at seven specific 2θ coordinate areas, flattened peaks and an increase in the crystallite size in the radiation-exposed groups due to mineralization loss and alteration of the hydroxyapatite crystal matrix in the tooth enamel. CONCLUSIONS: Radiotherapy can induce significant variations in the inorganic and organic functional groups constituting the tooth enamel surface; and these variations are dose dependent. The mechanism responsible for delamination and radiation caries needs to be explored by studying the protein lysis pattern, which might be a leading factor causing the enamel degradation and radiation caries.

Evaluation of homocysteine levels in individuals having nonsyndromic cleft lip with or without palate.

CONTEXT: Nonsyndromic cleft lip with or without palate (NSCL ± P) is a genetic predisposition involving defects in shape and makeup of the lip and palate. Elevation of homocysteine (Hcy) levels is seen in medical complications such as developmental anomalies causing neural tube defects, congenital vascular diseases, neurodegenerative and psychiatric conditions. Evaluation of serum Hcy levels forms an important feature to look further into molecular aspects. AIMS: The aim of this study was to evaluate the Hcy levels in NSCL ± P cases by comparing with control cases having no orofacial deformities. SETTINGS AND DESIGN: This study was performed with a biochemical assay in a research laboratory. MATERIALS AND METHODS: A cross-sectional prevalence study was done to compare the concentrations of Hcy between 25 NSCL ± P patients and 15 healthy controls. Blood samples were collected from both the patients and controls and assessed for serum Hcy level using competent chemiluminescent immunoassay technique. STATISTICAL ANALYSIS USED: Student's t-test was used for statistical analysis. RESULTS: The average Hcy concentration was 9.5 µmol/L in control group. There was an increase in Hcy concentration among the NSCL ± P cases with an average value of 18.4 µmol/L. The results were found to be statistically significant using Student's t-test. CONCLUSIONS: The results of this study indicate that Hcy concentration has a significant elevation in NSCL ± P patients when compared with that of control cases.