Title Učinak bioaktivnoga stakla 45s5 na fizikalna i kemijska svojstva eksperimentalnih kompozitnih materijala Title (english) The effect of bioactive glass 45s5 on the physical and chemical properties of experimental composite materials Author Nika Španović Mentor Zrinka Tarle (mentor)Mentor Hrvoje Skenderović (komentor)Committee member Goranka Prpić-Mehičić (predsjednik povjerenstva)Committee member Katica Prskalo (član povjerenstva)Committee member Eva Klarić Sever (član povjerenstva)Committee member Bernard Janković (član povjerenstva)Committee member Ozren Gamulin (član povjerenstva)Granter University of Zagreb Defense date and country 2018-07-11, Croatia Scientific / art field, BIOMEDICINE AND HEALTHCARE Universal decimal classificationUDC ) 616.31 - Stomatology Abstract Remineralizirajući kompozitni materijali temeljeni na bioaktivnom staklu (BG, engl. bioactive glass) pokazuju potencijal za prevenciju sekundarnog karijesa s pomoću površinske precipitacije sloja hidroksiapatita te otpuštanja kalcijevih i fosfatovih iona, koji se mogu ugraditi u tvrda zubna tkiva. Svrha ovog rada bila je priprema serije eksperimentalnih kompozitnih materijala s različitim udjelima BG-a i istraživanje njihova potencijala za precipitaciju hidroksiapatita, stupanj konverzije, dubinu polimerizacije, transmitanciju svjetlosti, porast temperature tijekom polimerizacije, apsorpciju vode i solubilnost.
Nakon sedmodnevne imerzije polimeriziranih uzoraka BG kompozita u fosfatima puferiranoj fiziološkoj otopini, na površini se formirao precipitat hidroksiapatita čija je debljina i morfologija ovisila o udjelu BG-a u kompozitu. Kod BG kompozita izmjeren je klinički prihvatljiv stupanj konverzije koji je bio u rasponu komercijalnih kompozita. Pri osvjetljavanju od 20 s svi BG kompoziti postigli su dubinu polimerizacije veću od 2 mm, koliko je propisano standardom za konvencionalne kompozite ISO 4049. Dodatak BG punila u eksperimentalne kompozitne materijale smanjio je maksimalni ostvarivi stupanj konverzije i doveo do strmijeg opadanja stupnja konverzije s porastom debljine kompozitnog sloja. Dodatak BG punila pri težinskom udjelu od 5 % doveo je do značajnog smanjenja svjetlosne transmitancije u usporedbi s materijalom koji je sadržavao samo ojačavajuća punila. Daljnje povećanje težinskog udjela BG do 40 % imalo je relativno malen učinak na svjetlosnu transmitanciju. Porast temperature tijekom svjetlosno aktivirane polimerizacije BG kompozita bio je usporediv ili viši od porasta temperature izmjerenog kod komercijalnih kontrolnih materijala. Povećanje težinskog udjela BG punila u eksperimentalnim kompozitima rezultiralo je nižim porastima temperature. Apsorpcija vode i solubilnost kod eksperimentalnih BG kompozita bile su značajno veće od referentnih vrijednosti propisanih standardom ISO 4049. Vrijednosti apsorpcije vode i solubilnosti kod eksperimentalnih kompozita rasle su s porastom težinskog udjela BG punila. Kontinuirani gubitak mase tijekom 287 dana imerzije u vodi izmjeren kod eksperimentalnih kompozita s težinskim udjelom BG-a od 10 % i više ukazuje na dugoročni remineralizacijski potencijal. Zaključno, istražena svojstva eksperimentalnih BG kompozita pokazuju potencijal za kliničku primjenu.
Abstract (english) Aim
Secondary caries is one of the main reasons for the failure of contemporary composite restorations. Bioactive composite materials based on bioactive glass (BG) offer the potential to prevent secondary caries via the release of remineralizing ions and precipitation of the hydroxyapatite layer at their surface. The aim of this study was to prepare a series of experimental composite materials containing variable filler ratios of BG and test some of their basic properties which are important for clinical applicability. The following properties of experimental BG-containing composites were tested: the potential to precipitate hydroxyapatite when immersed in a phosphate buffered saline (PBS) solution, degree of conversion, depth of cure, light transmittance, temperature rise during light curing, water sorption and solubility.
Materials and methods
Five experimental composite materials were prepared with 0 – 40 wt% of BG 45S5 in a resinous matrix of Bis-GMA/TEGDMA in a ratio of 60:40. The experimental composites also contained reinforcing fillers comprising silanized barium glass and silica, up to a total filler load of 70 wt%. To assess the hydroxyapatite precipitation, composite specimens were immersed in PBS for 7 days and examined using Fourier-transform infrared spectroscopy, FT-Raman spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. The degree of conversion was examined as a function of curing time (20 and 40 s) and composite layer thickness (0 – 4 mm) using FT-Raman spectroscopy. The depth of cure was assessed according to the ISO 4049 method and alternatively by determining the depth at which the degree of conversion declined to 80% of the maximum attainable value. Light transmittance was evaluated by real-time measurements of the light transmitted through 2 mm thick composite specimens during light-curing by means of a uv-vis spectrometer. Temperature rise during light curing was assessed at the bottom of 2 mm thick composite layers using a T-type thermocouple. Water sorption and solubility were measured according to a modified ISO 4049 protocol. Statistical analysis was performed using one-way and mixed model analysis of variance (ANOVA), Welch ANOVA with Tukey, Bonferroni and Games-Howell post-hoc adjustments, as appropriate. Correlations were tested using the Pearson correlation analysis. The global level of statistical significance for all tests was set at 0.05.
Results
Cured specimens of BG-composites formed a surface hydroxyapatite precipitate which was confirmed using infrared spectroscopy and visualized by a scanning electron microscope. Energy dispersive spectroscopy indicated that the precipitate was calcium-deficient hydroxyapatite. The thickness and morphology of the precipitate depended on the ratio of BG fillers in experimental composites. The BG-composites showed a clinically acceptable degree of conversion values which were in the range of commercial composites. For the curing time of 20 s, all of the BG-composites attained the depth of cure higher than 2 mm, as stipulated by the ISO 4049 requirements for conventional composites. The presence of BG fillers in experimental composites decreased the maximum attainable degree of conversion and caused a steeper decline of the degree of conversion values through increasing layer thicknesses. This effect was unrelated to the influence of the BG ratio on light transmittance and could be attributed to a hypothesized direct inhibitory effect of BG fillers on the free radical-mediated polymerization reaction. The addition of 5 wt% of BG fillers caused a significant decline in light transmittance in comparison with the experimental composite containing only reinforcing fillers, whereas a further increase in the BG load of up to 40 wt% showed a minor effect on light transmittance. Temperature rise during light curing of BG-composites was comparable or higher to that measured in commercial control materials. However, the temperature rise produced by BG-composites was within the range of commercial composites reported in the literature. Higher amounts of BG fillers in experimental composites resulted in lower temperature rise and later times at which temperature peak was attained, suggesting a possible effect of BG fillers on polymerization kinetics. Water sorption and solubility in experimental composites were significantly higher than the maximum values stipulated by the ISO 4049. Water sorption and solubility values increased with the increasing amount of BG fillers in the experimental composite series. A continuous decline in specimen mass during 287 days of water immersion, which was observed in experimental composites with a BG load of 10 wt% or more, indicates a long-term remineralizing potential.
Conclusions
The tested properties of experimental BG-containing composite materials indicate their potential for clinical applicability. Further studies should address mechanical properties and the remineralizing effect on dental hard tissues.
Keywords
bioaktivno staklo 45S5
bioaktivni dentalni kompoziti
hidroksiapatit
stupanj konverzije
transmitancija svjetlosti
dubina polimerizacije
temperatura
apsorpcija vode
solubilnost
ISO 4049
Keywords (english)
bioactive glass 45S5
bioactive dental composites
experimental composites
hydroxyapatite
degree of conversion
light transmittance
depth of cure
temperature
water sorption
solubility
ISO 4049
Language croatian URN:NBN urn:nbn:hr:127:729150 Study programme Title: dental medicine Type of resource Text File origin Born digital Access conditions Open access Terms of use Created on 2018-11-29 08:08:07
