Estudio comparativo de la bioactividad de dos materiales biocerámicos / Comparative Study of the Bioactivity of Two Bioceramic Materials

RESUMEN Los materiales a base de silicato de calcio han demostrado ser bioactivos debido a su capacidad para producir apatita carbonatada biológicamente compatible. El objetivo de este estudio fue analizar la bioactividad de Biodentine™ y MTA Repair HP® en contacto con discos de dentina humana, que se obturaron y dividieron aleatoriamente para formar cuatro grupos: grupo 1 Biodentine™, grupo 2 MTA Repair HP®, grupo control positivo MTA Angelus® y grupo control negativo IRM®, los cuales se incubaron en solución PBS durante 10 días, para posterior análisis por medio de MEB-EDS y Espectroscopía Raman. Los tres materiales a base de silicato de calcio analizados en este estudio demostraron ser bioactivos pues al entrar en contacto con una solución a base de fosfato desencadenaron la precipitación inicial de fosfato de calcio amorfo, que actúa como precursor durante la formación de apatita carbonatada.

ABSTRACT Calcium silicate-based materials have been shown to be bioactive due to their ability to produce biologically compatible carbonated apatite. The objective of this study was to analyze the bioactivity of Biodentine ™ and MTA Repair HP® in contact with human dentine discs, which were sealed and divided randomly to form four groups: group 1 Biodentine™, group 2 MTA Repair HP®, positive control group MTA Angelus® and negative control group IRM®, which were incubated in PBS solution for 10 days, for a subsequent analysis by means of MEB-EDS and Raman spectroscopy. The three calcium-based materials analyzed in this study proved to be bioactive because upon contact with a phosphate-based solution they were triggered at the onset of amorphous calcium phosphate, as the precursor during the formation of carbonated apatite.

Effect of iontophoresis on fluoride uptake in enamel with artificial caries lesion

Abstract: Iontophoresis is a noninvasive technique, based on the application of a constant low-intensity electric current to facilitate the release of a variety of drugs, whether ionized or not, through biological membranes. The objective of this research was to evaluate the effect of iontophoresis using different electric current intensities on the uptake of fluoride in dental enamel with artificial caries lesions. In this in vitro operator-blind experiment, bovine enamel blocks (n = 10/group) with caries-like lesions and predetermined surface hardness were randomized into 6 groups: placebo gel without fluoride applied with a current of 0.8 mA (negative control), 2% NaF gel without application of any current, and 2% NaF gel applied with currents of 0.1, 0.2, 0.4 and 0.8 mA. Cathodic iontophoresis was applied for 4 min. The concentration of loosely bound fluoride (calcium fluoride) and firmly bound fluoride (fluorapatite) was determined. The results were analyzed by the nonparametric Kruskal-Wallis and Dunn tests. Iontophoresis at 0.8 mA, combined with the application of fluoridated gel (2% NaF), increased fluoride uptake in enamel with caries-like lesions, as either calcium fluoride or fluorapatite.

Evaluation of low-dose dual energy computed tomography for in vivo assessment of renal/ureteric calculus composition

PURPOSE: This study aimed to assess the accuracy of low-dose dual-energy computed tomography (DECT) in predicting the composition of urinary calculi. MATERIALS AND METHODS: A total of 52 patients with urinary calculi were scanned with a 128-slice dual-source DECT scanner by use of a low-dose protocol. Dual-energy (DE) ratio, weighted average Hounsfield unit (HU) of calculi, radiation dose, and image noise levels were recorded. Two radiologists independently rated study quality. Stone composition was assessed after extraction by Fourier transform infrared spectroscopy (FTIRS). Analysis of variance was used to determine if the differences in HU values and DE ratios between the various calculus groups were significant. Threshold cutoff values to classify the calculi into separate groups were identified by receiver operating characteristic curve analysis. RESULTS: A total of 137 calculi were detected. FTIRS analysis differentiated the calculi into five groups: uric acid (n=17), struvite (n=3), calcium oxalate monohydrate and dihydrate (COM-COD, n=84), calcium oxalate monohydrate (COM, n=28), and carbonate apatite (n=5). The HU value could differentiate only uric acid calculi from calcified calculi (p80% sensitivity and specificity to differentiate them. The DE ratio could not differentiate COM from COM-COD calculi. No study was rated poor in quality by either of the observers. The mean radiation dose was 1.8 mSv. CONCLUSIONS: Low-dose DECT accurately predicts urinary calculus composition in vivo while simultaneously reducing radiation exposure without compromising study quality.

Enamel crystals of mice susceptible or resistant to dental fluorosis: an AFM study

Objective: This study aimed to assess the overall apatite crystals profile in the enamel matrix of mice susceptible (A/J strain) or resistant (129P3/J strain) to dental fluorosis through analyses by atomic force microscopy (AFM). Material and Methods: Samples from the enamel matrix in the early stages of secretion and maturation were obtained from the incisors of mice from both strains. All detectable traces of matrix protein were removed from the samples by a sequential extraction procedure. The purified crystals (n=13 per strain) were analyzed qualitatively in the AFM. Surface roughness profile (Ra) was measured. Results: The mean (±SD) Ra of the crystals of A/J strain (0.58±0.15 nm) was lower than the one found for the 129P3/J strain (0.66±0.21 nm) but the difference did not reach statistical significance (t=1.187, p=0.247). Crystals of the 129P3/J strain (70.42±6.79 nm) were found to be significantly narrower (t=4.013, p=0.0013) than the same parameter measured for the A/J strain (90.42±15.86 nm). Conclusion: enamel crystals of the 129P3/J strain are narrower, which is indicative of slower crystal growth and could interfere in the occurrence of dental fluorosis. .

Use of laser fluorescence in dental caries diagnosis: a fluorescence x biomolecular vibrational spectroscopic comparative study

The aim of this work was to verify the existence of correlation between Raman spectroscopy readings of phosphate apatite (∼960 cm−1), fluoridated apatite (∼575 cm−1) and organic matrix (∼1450 cm−1) levels and Diagnodent® readings at different stages of dental caries in extracted human teeth. The mean peak value of fluorescence in the carious area was recorded and teeth were divided in enamel caries, dentin caries and sound dental structure. After fluorescence readings, Raman spectroscopy was carried out on the same sites. The results showed significant difference (ANOVA, p<0.05) between the fluorescence readings for enamel (16.4 ± 2.3) and dentin (57.6 ± 23.7) on carious teeth. Raman peaks of enamel and dentin revealed that ∼575 and ∼960 cm−1 peaks were more intense in enamel caries. There was significant negative correlation (p<0.05) between the ∼575 and ∼960 cm−1 peaks and dentin caries. It may be concluded that the higher the fluorescence detected by Diagnodent the lower the peaks of phosphate apatite and fluoridated apatite. As the early diagnosis of caries is directly related to the identification of changes in the inorganic tooth components, Raman spectroscopy was more sensitive to variations of these components than Diagnodent.

O objetivo desse estudo foi verificar por meio da espectroscopia Raman, a existência de correlação entre os níveis de apatita fosfatada (∼960 cm−1), apatita fluoretada (∼575 cm−1) e matriz orgânica (∼1450 cm−1) e as leituras do Diagnodent® em diferentes estágios de cárie dental em dentes humanos extraídos. O valor médio do pico de fluorescência na área da cárie foi anotado e os dentes divididos em cárie de esmalte, dentina e dente hígido. Após as leituras de fluorescência, foi realizada a espectroscopia Raman nos mesmos sítios. Os resultados mostraram diferença significante (ANOVA p<0,05) entre as leituras de fluorescência para esmalte (16,4 ± 2,3) e dentina (57,6 ± 23,7) nos dentes cariados. Os picos Raman para esmalte e dentina evidenciaram que os picos ∼575 e ∼960 cm−1 foram mais intensos em cárie de esmalte. Houve correlação negativa e significante (p<0,05) entre os picos ∼575 e ∼960 cm−1 e cárie de dentina. Pode-se concluir que quanto maior a fluorescência detectada pelo Diagnodent menor o pico da apatita fosfatada e fluoretada. O diagnóstico precoce da cárie está diretamente relacionado com a identificação de mudanças nos componentes inorgânicos do dente, assim a espectroscopia Raman foi mais sensível para variações desses componentes quando comparada ao Diagnodent.