Karakterizacija mehaničkih i fizičko-hemijskih svojstava kompozitnih i glas-jonomernih cemenata
Characterization of mechanical and physicochemical properties of composite and glass-ionomer cements
Author
Mitrović, AleksandraMentor
Antonović, DušanCommittee members
Dimitrijević-Branković, SuzanaUskoković, Petar
Marinković, Aleksandar D.
Milošević, Miloš
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Show full item recordAbstract
U ovoj doktorskoj disertaciji ispitivana su mehaniþka i fiziþko-hemijska svojstva savremenih,
komercijalno dostupnih dentalnih cemenata. Izvršena je uporedna analiza þetiri razliþita
samovezujuüa dvojno-polimerizujuüa kompozitna cementa na bazi smole, Maxcem Elite (Kerr,
USA), Relyx U200 (3M, ESPE, Germany), Multilink Automix (Ivoclar Vivadent, Liechtenstein) i
SeT PP (SDI, Australia), glas-jonomer cementa Riva Luting (SDI, Australia) i samovezujuüeg glasjonomer cementa modifikovanog smolom Riva Luting Plus (SDI, Australia). Osnovna svrha izbora
materijala razliþitog sastava i indikacija je bila da se obuhvate sve tri grupe trajnih dentalnih
cemenata za adhezivnu tehniku cementiranja, kako bi se komparativnom karakterizacijom ispitala
svojstva što šireg spektra materijala. Kompozitni cementi na bazi smole imaju izvanredna estetska
svojstva, dobre mehaniþke i zadovoljavajuüe biološke karakteristike i koriste se za restauracije
prednjih i boþnih zuba. Meÿutim, glavni nedostaci ove grupe ...materijala su polimerizaciona
kontrakcija, nepotpuna konverzija monomera u polimer i veüi porast temperature tokom
polimerizacije koji može da prouzrokuje termiþku traumu u pulpi. Usled polimerizacione
kontrakcije, spoj zubnih tkiva i ispuna može biti ugrožen, pa se ova pojava smatra glavnim uzrokom
nastanka mikroprslina, koja dalje omoguüava prodor pljuvaþke i mikroorganizama. Neizreagovani
monomeri mogu da se naruše mehaniþka svojstva i biokompatiblnost ovih materijala. Glas-jonomer
cementi (GJC) su materijali na bazi vode i jedini pravi samovezujuüi (samoadhezivni) materijali
koji imaju antikariogeno dejstvo i sposobnost kontinuiranog oslobaÿanja fluora bez promene
fiziþkih svojstava. GJC-i nemaju široko rasprostranjenu primenu kao kompozitni cementi na bazi
smole zbog lošijih mehaniþkih svojstava i sporog vezivanja.
Metodom trodimenzionalne korelacije digitalnih slika (3D DIC) izvršena su merenja von Mizesovih
deformacija i pomeranja u svim ispitivanim materijalima. Takoÿe, kod ispitivanih materijala
izmerena je mikrotvrdoüa po Vikersu, stepen konverzije i maksimalna temperatura koju ispitivani
materijali dostižu tokom svetlosne polimerizacije LED lampom, primenom termoparova. Ispitana je
morfologija karakteristiþnih oblasti ispitivanih dentalnih materijala razliþitog hemijskog sastava
primenom skenirajuüe elektronske mikroskopije.
Rezultati dobijeni 3D DIC metodom su pokazali da je kod svih ispitivanih materijala uoþeno
nehomogeno deformaciono polje i da su veüe maksimalne vrednosti von Mizesovih deformacija u
perifernom delu uzoraka, a manje maksimalne vrednosti u centralnom delu. Najveüe vrednosti
maksimalnih deformacija imao je kompozitni cement Multilink Automix, a najmanje vrednosti
pokazao je glas-jonomer Riva Luting. Na osnovu izmerenih vrednosti pomeranja za sve ispitivane
kompozitne cemente dobijeno se usled polimerizacione kontrakcije materijala naspramna površina
uzorka u odnosu na površinu uzorka osvetljenu LED lampom kontrahuje u pravcu centra mase
materijala. Korišüenjem 3D DIC metoda izmerene su promene polja deformacija i posle
preporuþenog vremena polimerizacije. Najveüe izmerene vrednosti pomeranja imao kompozitni
cement Multilink Automix, a najmanje vrednosti pomeranja pokazao je kompozitni cement Relyx
U200. Statistiþkom analizom dobijeno je da su vrednosti Mizesove deformacije u perifernom delu
uzorka bile su u znaþajnoj korelaciji sa pomeranjem. Veüa vrednost deformacije je bila povezana i
sa veüom vrednošüu pomeranja (Pearsonov koeficijent r=0,639; p<0,001). Pozitivna korelacija je
registrovana i izmeÿu Mizesove deformacije u centralnom delu uzorka i pomeranjem (Pearsonov
koeficijent r=0,493; p=0,006). Rezultati mikrotvrdoüe su pokazali najveüe vrednosti mikrotvrdoüe
neposredno posle polimerizacije kod materijala Relyx U200, a nakon 24h najveüe vrednosti
mikrotvrdoüe bile su kod materijala Riva Luting. Porast vrednosti mikrotvrdoüe bio je prisutan kodsvih ispitivanih materijala nakon 24h, što je ukazalo na dugotrajnu reakciju oþvršüavanja materijala.
Statistiþkom analizom dobijeno je da su vrednosti Relyx U200, Maxcem Elite i Multilink Automix
pokazali su statistiþki znaþajno veüe vrednosti tvrdoüe u poreÿenju sa materijalima Riva Luting i
Riva Luting Plus, dok je SeT PP imao statistiþki znaþajno niže vrednosti tvrdoüe u odnosu na ostale
dentalne cemente, osim Riva Luting (p<0,05). Nakon 24 h Riva Luting i Riva Luting Plus su
pokazali statistiþki znaþajno veüu vrednost tvrdoüe u poreÿenju sa ostalim dentalnim cementima
(p<0,05). Vrednosti tvrdoüe materijala Relyx U200 su bile statistiþki znaþajno veüe u odnosu na
Multilink Automix, Maxcem Elite i SeT PP (p<0,05). SeT PP je, sliþno kao i u merenju neposredno
posle polimerizacije, imao statistiþki najnižu vrednost tvrdoüe od svih ispitivanih materijala
(p<0,05). Vrednosti tvrdoüe dentalnih cemenata neposredno posle polimerizacije i nakon 24 h nisu
bile statistiþki znaþajno razliþite samo u sluþaju materijala Maxcem Elite (p>0,05). Svi ostali
ispitivani materijali su imali statistiþki znaþajno veüe vrednosti mikrotvrdoüe nakon 24 h u odnosu
na vrednosti dobijene neposredno posle polimerizacije (p<0,05). Ispitivani kompozitni materijali su
pokazali znaþajno poveüanje konverzije nakon upotrebe LED lampe u trajanju od 20 s. Najveüe
vrednosti stepena konverzije imali su Multilink Automix i Relyx U200, respektivno, što je i u
skladu sa rezultatima dobijenim 3D DIC metodom korelacije digitalnih slika i mikrotvrdoüe po
Vikersu. Mikografije ispitivanih materijala ukazuju na nehomogenu stukturu koja se sastoji od
aglomerata veüih i manjih dimenzija, veliþine od 2 do 15 ȝm što znaþi da u ispitivanim materijalima
punioci nisu monodisperzni. Svi ispitivani materijali su procentualno najviše imali veliþine preþnika
þestica punioca u opsegu 1,0-2,0 ȝm...
The aim of this doctoral dissertation is investigation of the mechanical, physical and chemical
properties of contemporary, commercially available dental cements. Comparative analysis of four
different self-adhesive resin based dual-curing composite cements, Maxcem Elite (Kerr, USA),
Relyx U200 (3M, ESPE, Germany), Multilink Automix (Ivoclar Vivadent, Liechtenstein) and SeT
PP (SDI, Australia), the glass-ionomer cement Riva Luting (SDI, Australia) and the self-adhesive
resin-modified glass-ionomer Riva Luting Plus r (SDI, Australia) was performed. The main purpose
of selection of material with different composition and indications was to cover all three groups of
permanent dental cements for adhesive cementation, in order to investigate the properties of a wide
range of materials by comparative characterization. Resin-based composite cements have
outstanding aesthetic properties, good mechanical and acceptable biological characteristics and they
are used for restorations of the anterio...r and lateral teeth. However, the major disadvantages of this
material group are polymerization shrinkage, incomplete monomer to polymer conversion, and a
higher temperature increase during polymerization that can cause thermal trauma to the pulp. Due to
polymerization shrinkage, the contact area between dental tissues and restorative material can be
compromised, and this phenomenon is considered to be the main cause of the marginal microcracks
formation, which further allows penetration of saliva and microorganisms. Unreacted monomers
can impair the mechanical properties and biocompatibility of these materials. Glass-ionomer
cements (GJCs) are water-based materials and the only real self-adhesive materials that have
anticarcinogenic effect and the ability to release fluorine continuously without changing physical
properties. GJCs don’t have widespread application as resin-based composite cements due to poorer
mechanical properties and slow bonding.
Three-dimensional Digital Image Correlation (3D DIC) was used to measure von Mises strain and
displacements in all tested materials. Also, Vickers micro hardness, the degree of conversion and
the maximum materials’ temperature reached during LED light polymerization, using
thermocouples was measured. The morphology of characteristic areas of the examined dental
materials of different chemical composition was investigated using scanning electron microscopy
(SEM).
The results obtained with the 3D DIC method showed that in all the tested materials a nonhomogeneous strain field was observed. Also, maximum values of von Mises strain were observed
in the peripheral part of the samples and smaller in the central part. Multilink Automix composite
cement had the highest values of maximum strain, and the glass-ionomer Riva Luting showed the
lowest strain values. Based on the measured displacement values for all tested composite cements,
due to the polymerization shrinkage of the material, the opposite surface of the specimen relative to
the specimen surface illuminated by the LED lamp shrinks towards the center of material mass. The
changes in the deformation and displacement fields, even after the recommended polymerization
time, were measured with 3D DIC method. Multilink Automix composite cement had the highest
measured displacement values, and the Relyx U200 composite cement showed the lowest
displacement values. Statistical analysis showed that Mises strain values in the peripheral part of the
sample were significantly correlated with displacement. A higher deformation value was also
associated with a higher displacement value (Pearson coefficient r = 0.639; p <0.001). A positive
correlation was also registered between Mises deformation in the central part of the sample and
displacement (Pearson coefficient r = 0.493; p = 0.006). The micro hardness results showed that
material Relyx U200 had the highest micro hardness values immediately after polymerization, andafter 24 h the highest micro hardness values were found with the Riva Luting material. An increase
in micro hardness values was present in all tested materials after 24 h, which indicated a longlasting material curing reaction.
Statistical analysis showed that Relyx U200, Maxcem Elite and Multilink Automix values showed
statistically significantly higher hardness values compared to Riva Luting and Riva Luting Plus
materials, while SeT PP had statistically significantly lower hardness values compared to other
dental cements except Riva Luting (p <0.05). After 24 h, Riva Luting and Riva Luting Plus showed
significantly higher hardness values compared to other dental cements (p <0.05). The hardness
values of material Relyx U200 were statistically significantly higher compared to Multilink
Automix, Maxcem Elite and SeT PP (p <0.05). The SeT PP had statistically the lowest hardness
value of all the materials tested (p <0.05). The hardness values of dental cements immediately after
polymerization and after 24 h were not statistically significantly different except in the case of
material Maxcem Elite (p> 0.05). All other tested materials had statistically significantly higher
micro hardness values after 24 h than micro hardness values obtained immediately after
polymerization (p <0.05). The tested composite materials showed a significant increase in
conversion after using an LED lamp for 20 s. Multilink Automix and Relyx U200 had the highest
degree of conversion, respectively, which is in compliance with the results obtained by the 3D DIC
method and Vickers micro hardness. The micrographs of the tested materials indicate a nonhomogeneous structure consisting of agglomerates of larger and smaller sizes, ranging from 2 to 15
ȝm which means that the fillers in the tested materials are not mono dispersed. All tested materials
had highest percent of the diameter filler particle in the range of 1.0–2.0 ȝm...