Study of mineral and matrix maturation in dentin

Spectroscopic analysis was used to study the patterns of changes in the mineral and matrix properties of dentin during maturation of the tissue. Fourier Transform Infrared Imaging (FTIRI) analyses on undecalcified semi-thin sections from fetal bovine incisors and developing mouse molars were performed. In addition, fetal bovine microdissected mantle and circumpulpal dentin specimens of successive tissue age were analyzed by Fourier Transform Infrared (FTIR) analysis and by amino acid and matrix phosphate assays. In the initial studies, the formation of mantle and circumpulpal dentin as two distinct dentin compartments in the developing fetal incisors was established through analysis of distribution of mineral:matrix and mineral crystallinity values. Changes in the mineral:matrix, mineral crystallinity, acidic phosphate substitution and carbonate substitution in the mineral of mantle and circumpulpal dentin during maturation were subsequently quantitatively analyzed from FTIRI results. In this study, separate patterns of changes in mineral properties were found for mantle and circumpulpal dentin, in terms of initial and final levels and rates of increase or decrease of mineral properties values. Spectroscopic analysis of different maturation stages microdissected mantle and circumpulpal dentin specimens showed a great decrease in the dentin relative water content, affecting the dentin matrix conformation. Chemical analyses of similar microdissected specimens showed a significant increase in the organic phosphate of dentin matrix occurring during maturation. This increase was associated with continuing phosphorylation of existing phosphoproteins without further changes in the protein density. Finally, the study of dentin maturation using 6 day-old mouse molars by FTIRI was validated. Reproducibility in the pattern of changes in the mineral properties examined was found to be highly dependent on the sectioning orienation of molars. It is likely that higher resolution analytical methods and/or slightly older animal age would enhance the analytical outcome in such studies

Root canal hydrophobization by dentinal silanization: Improvement of silicon-based endodontic treatment tightness

A new strategy to improve silicon-based endodontic treatment tightness by dentine hydrophobization is presented in this work: root dentine was silanized to obtain a hydrophobic dentine-sealer interface that limits fluid penetration. This strategy was based on the grafting of aliphatic carbon chains on the dentine through a silanization with the silane end groups [octadecyltrichlorosilane (OTS) and octadecyltriethoxysilane]. Dentine surface was previously pretreated, applying ethylenediaminetetraacetic acid and sodium hypochlorite, to expose hydroxyl groups of collagen for the silane grafting. Collagen fibers exposure after pretreatment was visible with scanning electron microscopy, and Fourier transform infrared (FTIR) spectroscopy showed their correct exposition for the silanization (amide I and II, with 1630, 1580, and 1538 cm⁻¹ peaks corresponding to the vibration of C=O and C--N bonds). The grafting of aliphatic carbon chains was confirmed by FTIR (peaks at 2952 and 2923 cm⁻¹ corresponding to the stretching of C--H bonds) and by the increasing of the water contact angle. The most efficient hydrophobization was obtained with OTS in ethyl acetate, with a water contact angle turning from 51° to 109°. Gas and liquid permeability tests showed an increased seal tightness after silanization: the mean gas and water flows dropped from 2.02 × 10⁻⁸ to 1.62 × 10⁻⁸ mol s⁻¹ and from 10.8 × 10⁻³ to 5.4 × 10⁻³ µL min⁻¹, respectively. These results show clear evidences to turn hydrophilic dentine surface into a hydrophobic surface that may improve endodontic sealing. Copyright © 2013 Wiley Periodicals, Inc

Maturational changes in dentin mineral properties

In this study the changes in properties of the maturing mantle and circumpulpal dentin were quantitatively analyzed. Sections from six fetal bovine undecalcified incisors were used. Regions of mantle and circumpulpal dentin of sequential maturation stages were identified on spectroscopic images acquired by Fourier Transform Infrared Imaging. Spectroscopic parameters corresponding to mineral properties at these stages were analyzed and reported as a function of distance from the cervix of the incisor, the latter representing tissue age. Mineral parameters were correlated with distance from the cervix. Values of these parameters in mantle and circumpulpal dentin were compared. A multi-phasic pattern of changes was found for all the parameters examined, with most of the alterations occurring in the initial maturation period. The patterns of temporal variation in mantle and circumpulpal dentin mineral properties show distinct developmental stages and were not identical for the two dentin compartments. The study showed that mineral maturation in dentin is not a linear process and that mantle dentin is developmentally distinct from circumpulpal dentin, presenting at certain stages different physicochemical events during the maturation of the tissue

Changes in matrix phosphorylation during bovine dentin development

Phosphorylation of the organic matrix proteins of dentin is important for the initiation of mineralization, but its relevance in later mineralization stages is controversial. The objective of this study was to analyze changes in the total matrix phosphate content during dentin development and to identify their origin. Amino acid and total matrix phosphate analyses of microdissected developing mantle and circumpulpal fetal bovine dentin specimens were performed. The amino acid composition showed few changes during mantle and circumpulpal dentin maturation. However, the total matrix phosphate content showed a significant, positive correlation with tissue maturation in both mantle and circumpulpal dentin, with a two- and a three-fold increase, respectively, being observed. The data indicate that changes occur in the pattern of phosphorylation of matrix proteins during dentin maturation, which we suggest may play a functional role in later stages of tooth mineralization

Effect of HIP/ribosomal protein L29 deficiency on mineral properties of murine bones and teeth

Mice lacking HIP/RPL29, a component of the ribosomal machinery, display increased bone fragility. To understand the effect of sub-efficient protein synthetic rates on mineralized tissue quality, we performed dynamic and static histomorphometry and examined the mineral properties of both bones and teeth in HIP/RPL29 knock-out mice using Fourier transform infrared imaging (FTIRI). While loss of HIP/RPL29 consistently reduced total bone size, decreased mineral apposition rates were not significant, indicating that short stature is not primarily due to impaired osteoblast function. Interestingly, our microspectroscopic studies showed that a significant decrease in collagen crosslinking during maturation of HIP/RPL29-null bone precedes an overall enhancement in the relative extent of mineralization of both trabecular and cortical adult bones. This report provides strong genetic evidence that ribosomal insufficiency induces subtle organic matrix deficiencies which elevates calcification. Consistent with the HIP/RPL29-null bone phenotype, HIP/RPL29-deficient teeth also showed reduced geometric properties accompanied with relative increased mineral densities of both dentin and enamel. Increased mineralization associated with enhanced tissue fragility related to imperfection in organic phase microstructure evokes defects seen in matrix protein-related bone and tooth diseases. Thus, HIP/RPL29 mice constitute a new genetic model for studying the contribution of global protein synthesis in the establishment of organic and inorganic phases in mineral tissues

Exploitation of backup Generator sets for load curve smoothening of the Athens Olympic Stadium

101 σ.Σκοπος της διπλωματικής αυτής εργασίας είναι να μελετήσει τρόπους για τη βέλτιστη αξιοποίηση της υφιστάμενης υποδομής του ΟΑΚΑ, και κυριότερα των εφεδρικών ΗΖ. Η αξιοποίηση αυτή αφορά τόσο στην εξαγωγή κέρδους από αυτά όσο και στην βελτίωση της αξιοπιστίας του δικτύου. Η σημερινή τους χρήση περιορίζεται στο να αναλαμβάνουν μόνο κάποια φορτία ανάγκης σε περίπτωση διακοπής της παροχής. Αθροιστικά η εγκατεστημένη ισχύς τους όμως υπερβαίνει την αιχμή του δικτύου. Συνεπώς προτείνεται να αλλαχθεί ο τρόπος χρήσης τους ώστε να μπορεί να δημιουργείται ένα ενιαίο μικροδίκτυο που να καλύπτει πλήρως τις ανάγκες της εγκατάστασης σε περίπτωση διακοπής της παροχής και γίνεται αναφορά στα προβλήματα προστασίας και ελέγχου που αυτό συνεπάγεται. Οι κατανάλωση του δικτύου είναι χρονικά εντοπισμένη γύρω από τα αθλητικά γεγονότα και τις εκδηλώσεις που πραγματοποιούνται στο συγκρότημα του ΟΑΚΑ. Για το λόγο αυτό η καμπύλη φορτίου παρουσιάζει μεγάλες αιχμές και σχετικά χαμηλό συντελεστή χρησιμοποίησης. Κατά συνέπεια δαπανάται μεγάλο ποσό από τους λογαριασμούς ηλεκτρικής ενέργειας στις χρεώσεις ισχύος. Προτείνεται λοιπόν να χρησιμοποιηθούν τα ΗΖ ώστε να παράγουν ένα μέρος της ισχύος κατά τις στιγμές που παρουσιάζεται αιχμή, ώστε να εξομαλυνθεί η καμπύλη φορτίου και να μειωθεί το κόστος της ηλεκτρικής ενέργειας. Για το σκοπό αυτό κατασκευάστηκε ένα πρόγραμμα που υπολογίζει τον βέλτιστο τρόπο που πρέπει να παράγουν τα ΗΖ ώστε να μεγιστοποιείται το οικονομικό όφελος, η γλώσσα που χρησιμοποιήθηκε ήταν η PASCAL και τα δεδομένα προέκυψαν από τα καταγραφικά μηχανήματα της ΔΕΗ. Ακόμα παίρνοντας δεδομένα από το SCADA του ΟΑΚΑ, βρέθηκε μέσω ενός προγράμματος MATLAB η βέλτιστη συνδεσμολογία του δικτύου και στη συνέχεια έγινε ξανά υπολογισμός των αναμενώμενων κερδών από την εφαρμογή της εξομάλυνσης της καμπύλης με την χρήση των ΗΖ συνυπολογίζοντας τα τεχνικά τους χαρακτηριστικά όπως η κατανάλωσή τους και ο περιορισμός τεχνικού ελαχίστου.The purpose of this thesis is to study ways to optimally exploit the infrastructure of the Athens Olympic Stadium (AOS) and most importantly the backup generator sets intalled, in order to gain profit and to improve the network reliability. Today their use is limited to supply power to emergency loads. However, their cumulative installed capacity excedes the total power peak of the network. Therefore, it is proposed to make all the needed changes to create a microgrid and there is reference to the problems of protection and control that this entails. The highest consumption of the network happens during the sports events and the venues at the AOS. For this reason, the load curve has very sharp edges and relatively low utilization rate. Consequently, a large proportion of electricity cost is spent on power charges. It is therefore proposed to use the HZ to produce power during peak times and smoothen the load curve. For this purpose a program was made to calculate the optimum way to operate the Gen-Sets in order to maximize the economic profit, the language used was PASCAL and the data was acquired from the power supplier. What is more, after acquiring further data from the SCADA of the network, a program in MATLAB was made to find the optimal topology of the network that minimizes power costs and the profit from the application of the peak-shaving scheme was recalculated taking into account the technical specifications of the gen-sets.Δημήτριος Φ. Βερδελή

The effect of universal adhesives on dentine collagen

Objectives: The purpose of the study was to evaluate the integrity of dentine type I collagen after self-etching (SE) treatments with strong and mild universal adhesives. Methods: Coronal dentine specimens (n = 10/product) were imaged by optical microscopy and analyzed by ATR-FTIR spectroscopy before and after treatment with 32% phosphoric acid gel (PA-negative control), 17% neutral EDTA (ED-positive control) conditioners and Adhese Universal (AD), Clearfil Universal Bond Quick (CQ), G-Premio Bond (GP), Prelude One (PR) and Scotchbond Universal (SB) adhesives. From the spectroscopic analysis the following parameters were determined: a) Extent of dentine demineralization (DM%) and b) percentage area of the Amide I curve-fitted components of β-turns, 310-helix/β-turns, α-helix, random coils, β-sheets and collagen maturation (R) index. Statistical analysis was performed by one-way ANOVA (DM%), paired t-test/Wilcoxon test (Amide I components) and Spearman correlation coefficient (DM% vs Amide I components) at an a = 0.05 level. Results: PA, ED and GP removed the smear-layer and opened tubule orifices, whereas all other treatments removed only the intratubular smear-layer fraction. The ranking of the statistically significant differences in DM% was PA > GP > ED > AD, SB, CQ, PR, with AD being significantly different from PR. Regarding the Amide I components, PA demonstrated a significant reduction in β-turns, α-helices and an increase in β-sheets, GP a reduction in β-turns, AD an increase in β-turns and random coils, and CQ an increase in β-turns. PR, SB and ED showed insignificant differences in all the Amide I components. Significant correlations were found between DM%-random coils and DM%-R. Significance: The universal adhesives used in the SE mode induced none to minimal changes in dentine collagen structure, without evidence of the destabilization pattern observed after conventional phosphoric acid treatments. © 2021 The Academy of Dental Material