Solubility study of phytochemical cross-linking agents on dentin stiffness

Objectives: The effects of interactions between cross-linking proanthocyanidins (PA) in polar solvents and type-I collagen of demineralized dentin were investigated. Methods: Three PA-rich extracts, two from grape seed (GSEP and GSES) and one from cocoa (COE), were dissolved (water, ethanol:water and acetone:water) and analyzed for their ability to increase the modulus of elasticity of demineralized dentin. Sound dentin beams (0.5 mm x 1.7 mm x 7 mm) were fully demineralized and divided into 12 groups according to the type of cross-linking agent and solvents used. Specimens were immersed in the respective solutions and tested at baseline, 10, 30, 60, 120 and 240 min. Results: The elastic modulus (EM) of dentin was significantly increased by the PA treatment regardless of time (p < 0.05 for all times). The extracts showed different solubility in different solvents. GSEP showed the highest increase in EM when diluted in distilled water and acetone at all exposure times. Both GSEs showed superior results when diluted in distilled water and after 4 h of treatment, while COE produced strongest enhancement when dissolved in ethanol:water. Conclusions: The results indicates that herbal extraction process and other pharmacognostic parameters have an important influence on extract solubility as well as constitution and, consequently, on the PA-dentin matrix interaction. (C) 2010 Elsevier Ltd. All rights reserved.

Cross-Sectional Microhardness of Human Enamel Subjected to Erosive, Cariogenic or Combined Erosive/Cariogenic Challenges

This in situ study evaluated the interaction between caries and erosion processes. In the first phase, enamel specimens were subjected to erosion without dental plaque (EO) or to erosion with plaque (EP); in the second phase, they were subjected to erosion plus cariogenic challenge (EC) or cariogenic challenge (CO), both with plaque accumulation. Cross-sectional hardness data (10-330 mu m depth) were tested using ANOVA (alpha = 0.05). EO and EP showed surface softening to 10 mu m depth. CO and EC produced subsurface lesions, of similar depth (up to 220 mu m), with CO showing higher integrated loss of hardness than EC, indicating that cariogenic and erosive challenges did not have an additive effect. Copyright (C) 2010 S. Karger AG, Basel

Comparison of Cross-Sectional Hardness and Transverse Microradiography of Artificial Carious Enamel Lesions Induced by Different Demineralising Solutions and Gels

The aims of this study were: (1) to correlate surface (SH) and cross-sectional hardness (CSH) with microradiographic parameters of artificial enamel lesions; (2) to compare lesions prepared by different protocols. Fifty bovine enamel specimens were allocated by stratified randomisation according to their initial SH values to five groups and lesions produced by different methods: MC gel (methylcellulose gel/lactic acid, pH 4.6, 14 days); PA gel (polyacrylic acid/lactic acid/hydroxyapatite, pH 4.8, 16 h); MHDP (undersaturated lactate buffer/methyl diphosphonate, pH 5.0, 6 days); buffer (undersaturated acetate buffer/fluoride, pH 5.0, 16 h), and pH cycling (7 days). SH of the lesions (SH(1)) was measured. The specimens were longitudinally sectioned and transverse microradiography (TMR) and CSH measured at 10- to 220-mu m depth from the surface. Overall, there was a medium correlation but non-linear and variable relationship between mineral content and root CSH. root SH(1) was weakly to moderately correlated with surface layer properties, weakly correlated with lesion depth but uncorrelated with integrated mineral loss. MHDP lesions showed the highest subsurface mineral loss, followed by pH cycling, buffer, PA gel and MC gel lesions. The conclusions were: (1) CSH, as an alternative to TMR, does not estimate mineral content very accurately, but gives information about mechanical properties of lesions; (2) SH should not be used to analyse lesions; (3) artificial caries lesions produced by the protocols differ, especially considering the method of analysis. Copyright (C) 2009 S. Karger AG, Basel

Cross-Sectional Hardness of Enamel from Human Teeth at Different Posteruptive Ages

This study evaluated, by cross-sectional hardness (CSH), enamel maturation at different depths in sound human teeth at different posteruptive ages (12 per age group): unerupted (molars; control), 2-3 years (premolars), 4-10 years (premolars) and >10 years (molars). Cross-sectional Knoop hardness was measured at 10, 30, 50, 70, 90, 110, 220 and 330 mu m depth from the surface. The data were subjected to two-way ANOVA followed by Bonferroni`s pairwise tests (alpha = 0.05). The CSH significantly increased with posteruptive age, indicating that the time of exposure in the oral cavity might result in deep enamel maturation. Copyright (C) 2009 S. Karger AG, Basel

Evaluation of the presence or absence of papilla between tooth and implant

Objective: The purpose of this study was to evaluate the papilla level adjacent to single-tooth implants in the maxillary anterior region in individuals with cleft lip, alveolus, and palate to verify whether there is correlation among the vertical distance, horizontal distance, dental/prosthetic crown shape, and periodontal/peri-implant biotype with the presence of interproximal papilla. Design: Cross-sectional. Setting: Hospital for Rehabilitation of Craniofacial Anomalies, University of Sao Paulo (HRAC/USP). Patients: 77 papillae in 40 patients. Interventions: The periodontal/peri-implant biotype was clinically evaluated and characterized as thin or thick. Intraoral photographs were used to evaluate the presence or absence of papilla. Main Outcome Measures: Classification in scores (0 to 3) and determination of length (CL) and width (CW) of crowns adjacent to papillae. The CW/CL ratio was calculated for each crown in order to characterize it as square-shaped or triangular-shaped. The vertical and horizontal distances were obtained by radiographic evaluation. Results: The correlations between vertical distance and papilla score and horizontal distance and papilla score were statistically significant (p= .02 and p = .01). There was no significant difference between crown shape and periodontal/peri-implant biotype in distinct correlations with the papilla score (p = .41 and p = .07). Conclusion: The results suggest that the vertical and horizontal distances may have independent or combined relationship with the existence of interproximal papilla; the periodontal/peri-implant biotype (phenotype) was not correlated with the presence or absence of papilla, as well as the shape of the dental/prosthetic crown.

Influence of curing protocol on selected properties of light-curing polymers: Degree of conversion, volume contraction, elastic modulus, and glass transition temperature

Objectives. The purpose of this study was to investigate the effect of light-curing protocol on degree of conversion (DC), volume contraction (C), elastic modulus (E), and glass transition temperature (T(g)) as measured on a model polymer. It was a further aim to correlate the measured values with each other. Methods. Different light-curing protocols were used in order to investigate the influence of energy density (ED), power density (PD), and mode of cure on the properties. The modes of cure were continuous, pulse-delay, and stepped irradiation. DC was measured by Raman micro-spectroscopy. C was determined by pycnometry and a density column. E was measured by a dynamic mechanical analyzer (DMA), and T(g) was measured by differential scanning calorimetry (DSC). Data were submitted to two-and three-way ANOVA, and linear regression analyses. Results. ED, PD, and mode of cure influenced DC, C, E, and T(g) of the polymer. A significant positive correlation was found between ED and DC (r = 0.58), ED and E (r = 0.51), and ED and T(g) (r = 0.44). Taken together, ED and PD were significantly related to DC and E. The regression coefficient was positive for ED and negative for PD. Significant positive correlations were detected between DC and C (r = 0.54), DC and E (r = 0.61), and DC and T(g) (r = 0.53). Comparisons between continuous and pulse-delay modes of cure showed significant influence of mode of cure: pulse-delay curing resulted in decreased DC, decreased C, and decreased T(g). Influence of mode of cure, when comparing continuous and step modes of cure, was more ambiguous. A complex relationship exists between curing protocol, microstructure of the resin and the investigated properties. The overall performance of a composite is thus indirectly affected by the curing protocol adopted, and the desired reduction of C may be in fact a consequence of the decrease in DC. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.