Title Učinak jednovalne i viševalne polimerizacijske svjetlosti na fizikalna i optička svojstva različitih kompozitnih materijala Title (english) Effect of monowave and polywave curing light on physical and optical properties of different composite materials Author Igor Repušić305786398 Mentor Zrinka Tarle (mentor)Mentor Hrvoje Skenderović (komentor)Committee member Katica Prskalo (predsjednik povjerenstva)Committee member Vlatko Pandurić (član povjerenstva)Committee member Goran Pichler (član povjerenstva)Committee member Bernard Janković (član povjerenstva)Committee member Nada Galić (član povjerenstva)Granter University of Zagreb Defense date and country 2019-05-24, Croatia Scientific / art field, BIOMEDICINE AND HEALTHCARE Universal decimal classificationUDC ) 616.31 - Stomatology Abstract Stvrdnjavanje suvremenih kompozitnih materijala za izravne restoracije aktivira se vidljivom svjetlošću iz uređaja za polimerizaciju. Uređaji koji emitiraju uski raspon valnih duljina ograničen na plavu svjetlost nazivaju se jednovalnim, dok viševalni uređaji emitiraju širi spektar koji uz plavu uključuje i ljubičastu svjetlost. Svrha ovog rada bila je istražiti učinak polimerizacije jednovalnom i viševalnom svjetlošću u trajanju od 30 sekundi na sljedeća svojstva konvencionalnih i debeloslojnih kompozitnih materijala: transmisiju svjetlosti, mikrotvrdoću i porast temperature tijekom polimerizacije. Transmisija svjetlosti izračunata je kao udio intenziteta svjetlosti polimerizacijskog uređaja propušten kroz kompozitni sloj debljine od 2 i 4 mm. Porast temperature tijekom polimerizacije izmjeren je termočlankom T-tipa na dnu kompozitnog sloja debljine od 2 i 4 mm. Mikrotvrdoća je izmjerena Vickersovim testom na površini uzoraka te na dnu slojeva debljine od 2 i 4 mm. Omjer mikrotvrdoće na pojedinoj debljini i površinske mikrotvrdoće upotrjebljen je kao mjerilo za učinkovitost polimerizacije. Na transmisiju svjetlosti najznačajnije je utjecala debljina kompozitnog sloja i vrsta materijala, pri čemu su kod konvencionalnih kompozitnih materijala izmjerene značajno niže vrijednosti transmisije nego kod debeloslojnih (0,7 ‒ 16,7 % naspram 2,9 ‒ 27,0 %). Utjecaj vrste polimerizacijske svjetlosti bio je također statistički značajan, ali uz manju snagu učinka od debljine i vrste materijala. Kod svih materijala je tijekom polimerizacije opažen porast svjetlosne transmisije kojim je bilo moguće opisati kinetiku polimerizacije i procijeniti vrijeme završetka polimerizacije. Na porast temperature tijekom polimerizacije najizraženije je utjecala debljina kompozitnog sloja, a zatim vrsta i intenzitet polimerizacijske svjetlosti. Pri polimerizaciji jednovalnim uređajem izmjeren je porast temperature od 4,4 ‒ 7,0 °C, dok je polimerizacija viševalnim uređajem dovela do porasta temperature od 5,5 ‒ 9,2 °C. Na vrijednosti mikrotvrdoće je najizraženiji utjecaj imala vrsta materijala, zatim debljina kompozitnog sloja, dok je na posljednjem mjestu bila vrsta polimerizacijske svjetlosti. Statistički značajne razlike u mikrotvrdoći pri debljinama sloja od 0, 2 i 4 mm je češće opažena kod konvencionalnih kompozitnih materijala, dok su debeloslojni kompozitni materijali pri debljini sloja od 4 mm zadržali vrijednosti mikrotvrdoće iznad 91% u odnosu na površinsku mikrotvrdoću. Zaključno, polimerizacija konvencionalnih i debeloslojnih kompozitnih materijala viševalnom svjetlošću nije rezultirala praktično značajnim prednostima u usporedbi s jednovalnom svjetlošću.
Abstract (english) The setting reaction of contemporary resin composites is activated by visible light produced from curing units. A wide variety of curing units is available on the dental market, among which the light emission diodes (LED)-based curing units representing state of the art of dental photocuring are recommended for use with modern resin composites. The LED curing units differ by emission spectra, which is the foundation for their general division into narrow-spectrum (monowave) and wide-spectrum (polywave). The curing units from monowave group produce blue light which is efficient for light-curing of composites containing camphorquinone. Most of the resin composites on the dental market nowadays pertain to this group. On the other hand, polywave curing units emit in both violet and blue wavelength range, thus being beneficial for curing of resin composites with alternative photoinitiators. The absorption spectrum of these alternative photoinitiators is typically shifted towards lower wavelengths, rendering blue light produced by monowave units less effective for their activation. According to clinical handling and application, resin composite materials can be divided into conventional and bulk-fill. While conventional reins composites require an application and separate curing of layers which should not exceed 2 mm in thickness, bulk-fill resin composites enable making the whole restoration in a single layer which can reach 4-5 mm in thickness. Most of the bulk-fill resin composites contain classical photoinitiator system based on camphorquinone and tertiary amine, whereas some materials employ additional violet light-absorbing photoinitiators. The aim of this study was to assess the effect of light curing using monowave and polywave curing units on the following properties of conventional and bulk-fill resin composite materials: light transmission, microhardness, and temperature rise during polymerization.
Materials and methods
Three conventional resin composites (Tetric EvoCeram, Gradia Direct Posterior, and Grandio) and three bulk-fill resin composites (Tetric EvoCeram Bulk Fill, X-tra Fil, and Filtek Bulk Fill) were investigated. Discoid resin composite specimens (diameter = 6 mm, height = 2 and 4 mm) were light cured using a monowave curing unit (Bluephase Style M8) or a polywave curing unit (Bluephase Style). Light transmission through resin composite layers of 2 and 4 mm thickness was measured during light curing in real-time using a charge-coupled device visible light spectrometer. Light transmission was calculated as a fraction of
incident curing light intensity which was transmitted through resin composite specimens. Real-time light transmission curves were used to describe polymerization kinetics and to determine the time of polymerization completeness. The temperature rise during light curing was measured in real-time using a T-type thermocouple at the bottom of resin composite layers of 2 and 4 mm in thickness. The specimens for microhardness measurements were stored for 24 hours at 37 °C prior to testing, in order to complete the post-cure polymerization. Microhardness was assessed using a Vickers test at specimen surface and at the bottom of 2 and 4 mm thick resin composite specimens. On each specimen, three indentations were performed using a load of 100 g and dwell time of 15 seconds. The ratio of microhardness at a certain depth and surface microhardness was used as an indicator of polymerization effectiveness. Statistical analysis was performed using a three-way analysis of variance (ANOVA), mixed model ANOVA, and Pearson correlation analysis. Partial eta-squared statistics were used to determine the practical significance of each independent factor from three-way ANOVA. Tukey post-hoc adjustment was used for multiple comparisons. The level of significance for all statistical analyses was set at 0.05.
Results
The greatest effect on light transmission was exerted by layer thickness and resin composite type. Significantly lower light transmission values were measured for conventional resin composites (0.7 ‒ 16.7%) compared to the group of bulk-fill resin composites (2.9 ‒ 27.0%). The influence of curing unit type was statistically significant but with lower effect size compared to layer thickness and material type. An increase in light transmission of various extents was observed during polymerization in all resin composite materials. The curves obtained by plotting the light transmission as a function of time were used to describe polymerization kinetics and to develop a method for assessing the time of polymerization completeness. For clinically relevant layer thickness (2 mm for conventional and 4 mm for bulk-fill resin composites), the time of polymerization completeness ranged between 15.3 and 42.1 seconds. The strongest effect on the temperature increase during light curing was exerted by layer thickness, which was followed by the type and intensity of the curing light. Curing with a monowave unit resulted in a temperature rise of 4.4 ‒ 7.0 °C, whereas specimens cured using polywave unit showed a temperature rise of 5.5 ‒ 9.2 °C. Microhardness values were the most strongly influenced by material type, followed by layer thickness and curing unit type. Statistically significant differences in microhardness values among layer thicknesses of 0, 2, and 4 mm were more frequently identified in conventional
resin composites, while bulk-fill resin composites maintained more than 91% of their surface microhardness at 4 mm thick layers.
Conclusions
Light transmittance, microhardness, and temperature rise during polymerization were most strongly affected by layer thickness and differences in material composition. Although the effect of curing light type on the evaluated properties was formally identified by statistical analysis, the effect size was small compared to other factors, leading to the conclusion that there was no clinically relevant benefit in using polywave over monowave light for the curing of conventional and bulk-fill resin composites evaluated in this study.
Keywords
dentalni kompozitni materijali
uređaji za polimerizaciju
debeloslojni kompozitni materijal
mikrotvrdoća
temperatura
transmisija
Keywords (english)
dental resin composites
curing units
bulk-fill resin composites
microhardness
temperature
light transmission
Language croatian URN:NBN urn:nbn:hr:127:330711 Study programme Title: dental medicine Type of resource Text File origin Born digital Access conditions Open access Terms of use Created on 2020-01-24 11:39:46
