ACTA Acta Stomatol Croat. 2008;42(1):19-29.

STOMATOLOGICA
CROATICA
www.ascro.hr

IZVORNI ZNANSTVENI RAD

ORIGINAL SCIENTIFIC PAPER

Alena Knežević1, Mira Ristić2, Zrinka Tarle1, Goran Pichler3, Svetozar Musić2

Stupanj konverzije i temperaturni porast kod

kompozita polimeriziranih LED-uređajima
različitog intenziteta
Degree of Conversion and Temperature
Increase During Composite Polymerisation
with LED Units of Different Intensity
1 Zavod za endodonciju i restaurativnu stomatologiju Stomatološkog fakulteta Sveučilišta u Zagrebu, Gundulićeva 5, 10000 Zagreb
School of Dental Medicine, University of Zagreb, Department of Endodontics and Restorative Dentistry, Gundulićeva 5, 10000 Zagreb
2 Institut Ruđer Bošković, Bijenička cesta 54, 10000 Zagreb
Rudjer Bošković Institute, Bijenička cesta 54, 10000 Zagreb
3 Institut za fiziku, Bijenička cesta 46, 10000 Zagreb
Institute of Physics, Bijenička cesta 46, 10000 Zagreb

Sažetak Zaprimljen: 31. svibnja 2007.

LED-uređaji za polimerizaciju kompozitnih materijala gotovo su potpuno zamijeni- Prihvaćen: 6. veljače 2008.
li halogene polimerizatore. Njihov glavni nedostatak bio je porast temperature ti-
jekom postupka. Raniji LED-uređaji postizali su neznatan temperaturni porast, a Adresa za dopisivanje
uređaji novije generacije, zbog visokog intenziteta svjetla, ostvaruju viši stupanj Alena Knežević
konverzije, ali dovode u pitanje porast temperature tijekom polimerizacije kompo- Sveučilište u Zagrebu
zita. Svrha rada: bila je izmjeriti stupanj konverzije i temperaturni porast u uzorku Stomatološki fakultet
kompozitnog materijala polimeriziranog programima različitog intenziteta četiriju Zavod za endodonciju i restaurativnu
LED-uređaja. Materijal i postupci: U istraživanju su korišteni: Bluephase, Bluepha- stomatologiju
se C5, Bluephase C8 i Bluephase 16i (svi uređaji - Vivadent, Schaan, Liechtenstein). Gundulićeva 5, 10000 Zagreb
Stupanj konverzije mjeren je spektrofotometrom FTIR, a za mjerenje temperature ra- Tel. 00385 (0)1 48 02 113
bljen je termometar ELV Pyroscan (Leer, Njemačka). Rezultati: Najviši stupanj kon- Fax. 00385 (0)1 48 02 159
verzije postignut je kod polimerizacije uzoraka kompozitnog materijala soft-start ma505ak@yahoo.com
programom (SOFT) Bluephase 16i uređaja, a najniži kod polimerizacije uzoraka Blu-
ephase C5 uređajem. Najviši temperaturni porast zabilježen je tijekom polimeriza-
cije uzoraka programom visokog intenziteta (HIGH) i SOFT programom Bluephase
16i, a najniži u slučaju polimerizacije programom niskog intenziteta (LOW) Bluep-
hase C8 polimerizatora. Zaključak: Prema dobivenim rezultatima može se zaključi-
ti da veći stupanj konverzije vodi prema većem porastu temperature, bez obzira na Ključne riječi
vrstu kompozitnog materijala. kompozitne smole; polimeri

Uvod Introduction
Stupanj konverzije te temperaturni porast tije- Important parameters for assessing the efficien-
kom polimerizacije svjetlosno stvrdnjavajućih den- cy of different curing units are the degree of con-
talnih materijala važni su parametari u procjeni version and increase in temperature during photo-
učinkovitosti pojedinog uređaja za fotopolimeriza- polymerization of light cured dental materials. Both
20  Knežević i sur. Konverzija kompozita i temperaturni porast

ciju. Oba parametra ovise o intenzitetu svjetla emi- mentioned parameters are dependent on the light in-
tiranog iz fotopolimerizatora, spektru valnih duljina tensity emitted from the curing unit, spectrum of
te trajanju osvjetljavanja. emitted wavelength as well as illumination time.
Dosad najčešće rabljeni uređaji za fotopolime- Halogen curing units, the most commonly used
rizaciju kompozitnih materijala - halogene žaru- curing units for composite materials photopolymer-
lje, danas su gotovo potpuno zamijenjene diodnim ization, are nowadays replaced almost completely
(LED) uređajima za polimerizaciju. Halogeni uređa- by diode curing units (LED). Halogen curing units
ji proizvode svjetlo žarenjem tungstenske niti. Veći produce light by heating of the tungsten filament.
dio tako stvorene energije manifestira se kao topli- A high amount of produced energy is manifested
na, a vrlo mali postotak energije emitira se kao svje- as heat, while a very low percentage is emitted as
tlo potrebno za fotopolimerizaciju. Tijekom vreme- light appropriate for curing. Light intensity emit-
na jakost svjetla iz halogenog polimerizatora opada ted from halogen curing unit decreases over time.
zbog više čimbenika, kao sto su fluktuacije u volta- This is caused by different factors like fluctuation
ži, uništenje bulbusa, uništenje ili prljavi filtri, kon- in line voltage, deterioration of the light bulb, dete-
taminacija izlaznog optičkog voda dentalnim ma- rioration of the reflector or filter, contamination of
terijalom, oštećenje neodgovarajućim postupkom the light guide, effects of disinfection procedures on
čišćenja i održavanja samog uređaja. Prednost tih the transmission of light through the light guide and
uređaja je u tome što emitirani spektar pokriva ap- malfunction of the photoconductive fibers in the
sorpcijski spektar, ne samo kamforkinona nego i light guide. This type of curing lights emit broad
ostalih fotoinicijatora koji mogu biti u kompozitnoj spectrum of wavelengths which cover not only
smoli ili ostalim fotopolimerizirajućim restaurativ- camphorquinone, but other photoinitiators present
nim materijalima. in other light cured dental materials as well.
LED-uređaji proizvode svjetlost elektroluminis- LED curing units use electroluminescence to
cencijom, čime se proizvodi više učinkovitog svje- produce light, which produces more useful light
tla uz minimalnu proizvodnju topline. Osim toga, with minimal production of heat. Also, these cur-
za razliku od halogenih žarulja koje primarno proi- ing units produce primarily blue light as compared
zvode bijelo svjetlo koje filtriranjem daje plavu bo- to halogen units. Halogen units produce white light
ju potrebnu za polimerizaciju, ti uređaji odmah pro- which is filtered in blue light. Therefore, LED does
izvode plavo svjetlo, pa se tako izbjegava uporaba not require any filters. LEDs last for thousands of
filtara. Vijek trajanja im je nekoliko tisuća sati, za hours, whereas a conventional halogen light bulb
razliku od halogenih uređaja kojima se trajnost pro- lasts for only 30 to 50 hours (1-4). LEDs were de-
cjenjuje na 30 do 50 sati (1-4). LED-uređaji razvi- veloped through three generations with the aim to
jali su se tijekom triju generacija te se u svakoj na- increase the light intensity without a significant in-
stojao povećati intenzitet emitiranog svjetla uz što crease in temperature.
manji porast temperature. The tendency of modifying the halogen curing
Kao što su halogeni polimerizatori tijekom godi- units with different polymerization modes, in order
na prilagođeni različitim polimerizacijskim progra- to make more complete polymerizations with a low-
mima zbog što potpunije polimerizacije i manjeg er increase in temperature, was continued with the
temperaturnog porasta, ista tendencija nastavljena latest LED curing units.
je i s najnovijim LED-uređajima. Previous generations of LED curing units made
Ranije generacije imale su nešto niži stupanj kon- slightly lower degrees of conversion (49-55%), re-
verzije (49 do 55%) s manjim temperaturnim pora- sulting in lower temperature increase (1-3˚C) in
stom (1-3˚C) u odnosu prema halogenim uređajima comparison to halogen curing units (1-3). Newer
(1-3). Novije generacije LED-uređaja s većim izbo- generations of LED curing units offer a wide range
rom polimerizacijskih programa, jačim postignutim of polymerization programs, a higher intensity, and
intenzitetom te većim stupnjem konverzije, u pita- consequently a higher degree of conversion. How-
nje dovode porast temperature tijekom stvrdnjava- ever, they also endanger the temperature rise dur-
nja kompozitnog materijala. Ranije generacije dio- ing the hardening of composite material. Earlier
dnih uređaja emitirale su uži svjetlosni spektar - on generations of LED curing units emitted narrow-
se kretao u sklopu apsorpcijskog spektra kamforki- er light spectra, ranging in absorption spectrum of
nona (oko 468 nm). Kasniji diodni uređaji proširu- camforquinone (around 468 nm). Later generations
ju spektar na 460 do 490 nm, a najnovije generacije of diode curing units are widening the spectra from
Knežević et al. Conversion of Composite Materials and Temperature Rise  21
od 430 do 490 nm (4). Nekorisne niže valne dulji- 460 to 490 nm, while the latest generations have 430
ne štetno utječu na oči terapeuta, a više valne dulji- to 490 nm spectra (4). Useless lower wavelengths
ne nepotrebno zagrijavaju kako kompozitni materi- have harmful effect on clinician’s eyes, and higher
jal tako i samo zubno tkivo (5,6). wavelengths result in unnecessary heating of com-
Visok stupanj konverzije osigurava dobra fizič- posite material and dental tissue as well (5,6).
ko-mehanička svojstva kompozitnog materijala ili A high degree of conversion ensures good phys-
ispuna, a posljedica je veće polimerizacijsko sku- ical-mechanical properties of composite material, or
pljanje i polimerizacijski stres (7,8). Viši stupanj composite resin filling, but on the other hand, it leads
konverzije obično je veći kod jačeg intenziteta poli- to higher polymerization shrinkage and polymeriza-
merizacijskog svjetla te duže polimerizacije, no na- tion stress (7,8). The degree of conversion is usually
žalost i jedno i drugo prati veći temperaturni porast higher with a high intensity polymerization program
(9). S druge strane, nedovoljna jakost svjetla i ne- and longer polymerization time is used. Unfortunate-
odgovarajuće vrijeme osvjetljavnja mogu rezultirati ly, both factors are responsible for higher temperature
lošijom polimerizacijom te nepotpunom konverzi- rise (9). However, insufficient light intensity accom-
jom monomera, posebice u dubljim dijelovima ka- panied with insufficient light curing time, can lead
viteta. Posljedica je otpuštanje monomera u smo- to poor polymerization and incomplete conversion
li, što može štetno utjecati na vitalno pulpno tkivo of monomer, especially in deeper parts of the cavity.
(9-12). Consequently, non-reacted monomer present in the
Kako bi se ublažile negativne posljedice poli- resin can be released, which can be harmful for vital
merizacije kompozita, a istodobno osigurala du- pulp tissue (9-12).
gotrajnost ispuna, danas je predmet mnogih studija In order to minimize the negative consequences
primjena polimerizacijskih programa različitog in- of composite polymerization and, at the same time,
tenziteta i različitog vremena osvjetljavanja, ovisno to ensure the longevity of composite filling, the use
o kliničkoj situaciji. of polymerization programs with different light in-
Svrha ovog rada bila je odrediti stupanj konver- tensities and different curing times depending on
zije i temperaturni porast tijekom polimerizacije the clinical situation, is the object of many present
uzorka kompozitnog materijala polimerizacijskim studies.
programima različitog intenziteta četiriju LED-ure- The purpose of this study was to determine the
đaja. degree of conversion and the temperature rise in
composite materials sample polymerized by curing
modes of different light intensities from four LED
curing units.

Materijal i postupci Material and Methods

Mjerenje stupnja konverzije The degree of conversion measurement
Za ispitivanje stupnja konverzije rabljeni su Composite materials used for analyzing the de-
kompozitni materijali Tetric Ceram (boja A3 – exp. gree of conversion measurement were: Tetric Ce-
2008-03, lot. G06853) (TCA3) i Tetric EvoCeram ram (shade A3 – exp. 2008-03, lot. G06853) (TCA3)
(boja A2 – exp. 2010-01, lot. J04088) (TECA3) and Tetric EvoCeram (shade A2 – exp. 2010-01, lot.
(oba materijala: Vivadent, Schaan, Liechtenstein). J04088) (TECA3) - (both Vivadent, Schaan, Liech-
Uzorci kompozitnih materijala polimerizirani su tenstein). The composite resin samples were polym-
programom Bluephase soft-start (SOFT)), Bluep- erized with Bluephase (soft-start polymerization
hase C5, Bluephase C8 (program visokog inten- mode (SOFT)), Bluephase C5, Bluephase C8 (high
ziteta - HIGH, niskog intenziteta - LOW i SOFT intensity mode (HIGH), low intensity (LOW) and
program) i Bluephase 16i (programi HIGH, LOW SOFT mode) and Bluephase 16i (HIGH, LOW and
i SOFT) LED-uređajem (svi Vivadent, Schaan, Li- SOFT mode) LED curing unit (all units Vivadent,
echtenstein). U Tablici 1. prikazani su jakost i vri- Schaan, Liechtenstein). Table 1 presents intensity
jeme polimerizacije za pojedini uređaj i polimeri- and polymerization time for each and polymeriza-
zacijski program. tion mode used in the experiment.
Pripremljeno je bilo ukupno 96 uzoraka - po 48 A total of 96 samples were made, 48 for each
za svaki materijal; po 6 uzoraka od svakog materi- material; 6 samples from each material were for
jala za svaki polimerizacijski program. each polymerization mode.
22  Knežević i sur. Konverzija kompozita i temperaturni porast

Tablica 1. LED-polimerizatori rabljeni u eksperimentu za polimerizaciju uzoraka kompozitnih materijala

Table 1 LED curing units used in the experiment for polymerization of composite resin samples
Polimerizacijski LED polimerizator/ LED curing unit
program •
Polymerization mode Bluephase Bluephase C5 Bluephase C8 Bluephase 16i
Program visokog
800 mW/cm2 1600 mW/cm2
intenziteta • High - -
20 s 10 s
intensity mode (HIGH)
Program niskog
500 mW/cm2 650 mW/cm2 650 mW/cm2
intenziteta • Low -
40 s 30 s 30 s
intensity mode (LOW)
Soft-start 600 mW/cm2 prvih 5 s, 650 mW/cm2 prvih 5 s, 650 mW/cm2 prvih 5 s,
polimerizacijski 1100 mW/cm2 slijedećih 800 mW/cm2 slijedećih 1600 mW/cm2 slijedećih
program • Soft-start 25 s • - 25 s • 10 s •
polymerization mode 600 mW/cm2 first 5 s, 650 mW/cm2 first 5 s, 650 mW/cm2 first 5 s,
(SOFT) 1100 mW/cm2 next 25 s 800 mW/cm2 next 25 s 1600 mW/cm2 10 s

Uzorci kompozitnog materijala za mjerenje stup- The composite resin samples for the degree of
nja konverzije pripremljeni su bili na sljedeći način: conversion measurement were prepared as follows: a
na foliju Mylar veličine 3x3 cm stavljen je uzorak sample of unpolymerized composite material, 40 mg
nepolimeriziranoga kompozitnog materijala težine in weight, was placed on a Mylar sheet 3x3 cm in size,
40 mg, te je prekriven drugom folijom iste veličine. and covered with another Mylar sheet of the same
Zatim je sve stavljeno između dviju okruglih ploča size. After that, the sample was placed between two
od inoksa promjera 2 cm i stlačeno u ručnoj preši round inox plates, 2 cm in diameter, and pressed in a
pod tlakom od 107 Pa do debljine 0,1 mm. Tako pri- hand press at 107 Pa to 0,1 mm thickness. Inox plates
premljen uzorak kompozitnog materijala polimeri- were used to keep the sample in the same position. Af-
ziran je izvorom svjetla priljubljenog uz gornju foli- ter pressure applied in hand press, the inox plates were
ju Mylar. Uzorci su mjereni nakon polimerizacije i removed and the blue light source was applied on the
odvajanja od folije. upper Mylar sheet of the unpolymerized sample and
Stupanj konverzije mjeren je FT-IR spektrome- polymerized. The samples were measured after po-
trom (Perkin-Elmer, model 2000, Beaconsfield, Uje- lymerization and separation from the Mylar sheet.
dinjeno Kraljevstvo) u transmisijskom modu nepo- The degree of conversion of the composites used
sredno nakon polimerizacije uzoraka. FT-IR spektri in this study was measured using a FT-IR spectrom-
snimani su na sobnoj temperaturi (RT) u IR spek- eter (Perkin-Elmer, model 2000, Beaconsfield, UK)
tru od 4000 do 400 cm-1, s rezulucijom 4 cm-1 i 20 operating in transmittance mode immediately af-
skenova po uzorku. Prosječno 2 mg nepolimerizira- ter the end of polymerization of the resin sample
nog uzorka razrijedjeno je u ~100 mg spektroskop- with curing device. The FT-IR spectra were taken at
ski čistog KBr-a te sprešano u male pastile koristeći room temperature (RT) in the IR range 4000 - 400
se standardnom prešom s pritiskom od 5 t/cm2. Za cm-1, with the resolution of 4 cm-1 and 20 scans per
obradu spektra uzoraka koristio se IRDM (IR Da- sample. Approximately 2 mg of uncured samples
ta Manager) program. Spektri su prebačeni u ap- were diluted in ~100 mg of spectroscopically pure
sorpcijski mod te je stupanj konverzije bio određen KBr matrix in agate mortar and then pressed into
standardnom metodom prema Rueggebergu (13): small discs using a standard press with the pressure
% konverzije = (1- (polimerizirani uzorak / nepoli- of 5 t/cm2. The IRDM (IR Data Manager) program
merizirani uzorak)) x 100%. was used to process the obtained spectra. The spec-
tra were converted into absorbance mode and the
degree of conversion was determined by the stan-
dard method by Rueggeberg (13):
% conversion = (1- (polymerized sample / unpo-
lymerized sample)) x 100%.
Mjerenje temperaturnog porasta The temperature rise measurement
Za mjerenja temperature koristio se tvornički For the temperature measurement, a prefabricat-
plastični kalup u obliku kruga promjera 2 cm i de- ed plastic mould circular in shape, 2 cm in diameter
Knežević et al. Conversion of Composite Materials and Temperature Rise  23
bljine 4 mm. U sredini je bio napravljen četvrtasti and 4 mm thick, was used. In the center of the cir-
otvor veličine 4x4x4 mm, otvoren s gornje i s donje cle a quadrangular opening 4x4x4 mm was made,
strane kalupa. Otvor je ispunjen kompozitnim ma- opened from upper and lower side of the mould.
terijalom te je na donju površinu uzorka kroz otvor The opening was filled with composite material. A
na donjoj strani kalupa prislonjen termometar (ELV thermometer (ELV Pyroscan, Infrared Thermometer
Pyroscan, Infrared Thermometer PF 1000, PS 140/ PF 1000, PS 140/ PS 300, Leer, Germany) attached
PS 300, Leer, Njemačka), a na gornju izvor svje- on the lower sample surface through the opening in
tla. Osjetljivost rabljenog termometra iznosila je od the mould, and a light source on the upper surface
-20˚C do +300˚C. in the same manner. The thermometer sensitivity
Pripremljen je bio isti broj uzoraka kao i za mje- range used was from -20˚C to +300˚C.
renje stupnja konverzije. Temperatura za svaki uzo- The same number of samples as for the degree
rak očitavala se na početku i kraju iluminacije, a ra- of conversion measurement were prepared. Temper-
zlika između početne i krajnje vrijednosti koristila ature was recorded in the beginning and in the end
se za daljnju statističku obradu. of illumination for each sample. The difference be-
Za statističku obradu podataka koristila se de- tween incipient and terminal value was used for fur-
skriptivna statistika, jednosmjerna analiza varijan- ther statistical analysis.
ce (ANOVA), post hoc Tukeyev test i t-test spare- For statistical analysis of data descriptive statis-
nih uzoraka. tical methods were used, a one-way variance analy-
sis (ANOVA), post hoc Tukey test and paired sam-
ples t-test.

Rezultati Results
Rezultati mjerenja stupnja konverzije Results of the degree of conversion measurements
Rezultati mjerenja stupnja konverzije prikazani Results of the degree of conversion measure-
su u Tablicama 2. i 3. ments are shown in Table 2 and 3.
ANOVA je pokazala statistički znatne razlike u ANOVA showed statistically significant differ-
stupnju konverzije kod obaju kompozitnih materi- ences in the degree of conversion in composite ma-
jala, ovisno o vrsti polimerizatora i polimerizacij- terials depending on the polymerization device, as
skog programa (p<0,001). U Tablici 3. su rezulta- well as on the polymerization mode (p<0,001). In
ti Tukeyeva post-hoc testa za razlike u stupnjevima Table 3 the results of Tukey post-hoc test for dif-
konverzije kod osvjetljavanja različitim polimeriza- ferences in degrees of conversion for TC and TEC
cijskim programima za materijale TC i TEC. composite material illuminated with curing modes
Najviši stupanj konverzije postignut je kod oba- of different intensity are given.
ju kompozitnih materijala tijekom polimerizacije The highest degree of conversion was achieved
uzoraka SOFT programom Bluephase 16i uređaja in the case of polymerization of both composite ma-
(TC 68,60%, TEC 64,55%), a najniži stupanj zabi- terial samples with SOFT mode of Bluephase 16i
lježen je kod polimerizacije uzoraka Bluephase C5 curing unit (TC 68,60%, TEC 64,55%), while the
uređajem (TC 58,87%, TEC 57,31%). lowest degree of conversion was recorded in the
Paired samples T-test upozorio je da postoje sta- case of polymerization with Bluephase C5 curing
tistički velike razlike u stupnju konverzije između unit (TC 58,87%, TEC 57,31%).
obaju kompozita osvjetljavanih istim svjetiljkama. Paired samples T-test showed statistically signifi-
Za Bluephase C8 HIGH p=0,010, LOW p=0,015; cant differences in the degree of conversion between
SOFT p=0,004, za Bluephase 16i uređaj HIGH both composite materials illuminated with the same
p<0,001, LOW p<0,001, SOFT p<0,001, te za Blu- light sources: for Bluephase C8 HIGH p=0,010,
ephase C5 p=0,035 TEC ima statistički znatno niže LOW p=0,015; SOFT p=0,004, for Bluephase 16i
stupnjeve konverzije od TC-a, a samo kod polime- curing unit HIGH p<0,001, LOW p<0,001, SOFT
rizacije programom Bluephase SOFT nema razlika p<0,001, and for Bluephase C5 p=0,035. TEC has a
u stupnju konverzije između tih dviju vrsta kompo- statistically significant lower degree of conversion
zita. than TC, and only in the case of polymerization us-
ing Bluephase SOFT mode. No statistical signifi-
cant difference in the degree of conversion between
tested composite materials was found. With all oth-
24  Knežević i sur. Konverzija kompozita i temperaturni porast

Tablica 2. Rezultati mjerenja stupnja konverzije

Table 2 Results of the degree of conversion measurements
Stupanj konverzije (srednja vrijednost) •
Kompozitni materijal • LED polimerizator •
Degree of conversion (mean value) Std.Dev. p*
Composite material LED curing unit
(%)
Bluephase C8 HIGH 65,00 0,96
Bluephase C8 LOW 62,63 1,43
Bluephase C8 SOFT 65,51 1,75
Bluephase 16i HIGH 67,90 0,69
TC <0,001
Bluephase 16i LOW 67,87 0,77
Bluephase 16i SOFT 68,59 0,42
Bluephase C5 58,87 2,86
Bluephase SOFT 63,06 3,48
Bluephase C8 HIGH 61,53 2,74
Bluephase C8 LOW 60,43 0,70
Bluephase C8 SOFT 60,24 1,42
Bluephase 16i HIGH 61,44 0,45
TEC <0,001
Bluephase 16i LOW 62,32 1,25
Bluephase 16i SOFT 64,55 0,46
Bluephase C5 57,31 3,19
Bluephase SOFT 60,31 0,62
*ANOVA; TC - Tetric Ceram; TEC - Tetric EvoCeram

Tablica 3. Rezultati Tukeyeva post-hoc testa za razlike u stupnjevima konverzije kod osvjetljavanja raznim izvorima svjetla za
materijale TC i TEC
Table 3 Results of Tukey post-hoc test for differences in degree of conversion for TC and TEC composite materials
polymerized with curing units of different light intensity
Bluephase Bluephase Bluephase Bluephase Bluephase Bluephase Bluephase Bluephase
C8 HIGH C8 LOW C8 SOFT 16i HIGH 16i LOW 16i SOFT C5 SOFT
Bluephase
TC#, TEC# TC*, TEC#
C8 HIGH
Bluephase
TC* TC* TC*, TEC# TC#
C8 LOW
Bluephase
TEC# TC*
C8 SOFT
Bluephase
TC* TEC# TC*, TEC# TC*
16i HIGH
Bluephase
TC* TC*, TEC* TC*
16i LOW
Bluephase
TC#, TEC# TC*, TEC# TEC# TEC# TC*, TEC* TC*, TEC*
16i SOFT
Bluephase
TC*, TEC# TC# TC* TC*, TEC# TC*, TEC* TC*, TEC* TC#
C5
Bluephase
TC* TC* TC*, TEC* TC*
SOFT
Tukey post-hoc test *p≤0.001, #p<0.05; TC - Tetric Ceram; TEC - Tetric EvoCeram

er polymerization modes there are statistically sig-

nificant differences in the degree of conversion be-
tween tested composite materials.
Rezultati mjerenja temperaturnog porasta Results of temperature measurements
Rezultati mjerenja temperature prikazani su u Results of temperature measurements are shown
Tablicama 4. i 5. in Table 4 and 5.
Najviši temperaturni porast zabilježen je tijekom The highest temperature rise was recorded in
polimerizacije uzoraka uređajem Bluephase 16i, i to the case of polymerization of composite resin sam-
Knežević et al. Conversion of Composite Materials and Temperature Rise  25
Tablica 4. Rezultati mjerenja temperature
Table 4 Results of temperature measurements
Temperatura (sr.vrijednost) •
Kompozitni materijal • LED polimerizator •
Temperature (mean value) Std. Dev. p*
Composite material LED curing unit
(˚C)
Bluephase C8 HIGH 7,25 ,33
Bluephase C8 LOW 6,15 ,28
Bluephase C8 SOFT 7,53 ,49
Bluephase 16i HIGH 8,11 1,26
TC <0,001
Bluephase 16i LOW 6,71 ,68
Bluephase 16i SOFT 8,35 ,48
Bluephase SOFT 7,85 ,47
Bluephase C5 7,05 1,08
Bluephase C8 HIGH 6,80 ,62
Bluephase C8 LOW 4,98 ,63
Bluephase C8 SOFT 6,58 ,11
Bluephase 16i HIGH 8,10 1,24
TEC <0,001
Bluephase 16i LOW 6,88 ,43
Bluephase 16i SOFT 6,33 ,70
Bluephase SOFT 6,38 ,68
Bluephase C5 5,08 ,62
*ANOVA; TC - Tetric Ceram; TEC - Tetric EvoCeram

Tablica 5. Rezultati Tukeyeva post-hoc testa za razlike u temperaturi kod osvjetljavanja raznim izvorima svjetla za materijale TC
i TEC
Table 5 Results of Tukey post-hoc test for differences in degree of conversion for TC and TEC composite materials
polymerized with curing units of different light intensity
Bluephse Bluephase Bluephase Bluephase Bluephase Bluephase Bluephase Bluephase
C8 HIGH C8 LOW C8 SOFT 16i HIGH 16i LOW 16i SOFT SOFT C5
Bluephase
TEC# TEC#
C8 HIGH
Bluephase
TEC# TEC# TC#, TEC* TEC# TC* TC#
C8 LOW
Bluephase
TEC# TEC# TEC#
C8 SOFT
Bluephase
TC#, TEC* TEC# TEC# TEC# TEC#
16i HIGH
Bluephase
TEC# TC# TEC#
16i LOW
Bluephase
TC* TEC# TC#
16i SOFT
Bluephase
TC# TEC#
SOFT
Bluephase
TEC# TEC# TEC# TEC#
C5
Tukey post-hoc test *p≤0.001, #p<0.05; TC - Tetric Ceram; TEC - Tetric EvoCeram

za TC s programom SOFT (8,35 ˚C), a za TEC s ples with Bluephase 16i curing unit, especially for
programom HIGH (8,10 ˚C). Najniži porast tempe- TC using SOFT mode (8,35 ˚C), and for TEC using
rature postignut je kod polimerizacije programom HIGH mode (8,10 ˚C). The lowest temperature rise
LOW Bluephase C8 polimerizatora za oba kompo- was achieved using LOW polymerization mode of
zitna materijala (TC 4,98 ˚C, TEC 6,15 ˚C). Bluephase C8 curing unit for both composite mate-
ANOVA je istaknula statistički velike razlike u rials (TC 4,98 ˚C, TEC 6,15 ˚C).
porastu temperature kod materijala TC, ovisno o vr- ANOVA showed statistically significant differ-
sti svjetla (p<0,001). U Tablici 5. navedene su stati- ences in temperature rise for TC composite material
26  Knežević i sur. Konverzija kompozita i temperaturni porast

stički znatne razlike između pojedinih izvora svje- depending on the curing unit used (p<0,001). In Ta-
tla. ble 5 statistical significant differences between cur-
Kompozitni materijal TEC pokazuje također sta- ing units, i.e. polymerization programs, are given.
tistički velike razlike u utjecajima polimerizacijskih Composite material TEC also shows statistical-
programa na temperaturni porast (p<0,001), a razli- ly significant differences in temperature rise influ-
ke su češće i veće nego kod TC-a (Tablica 5.). enced by polymerization modes (p<0,001), and the
differences are more common and greater than in
TC (Table 5).

Rasprava Discussion
Polimerizacijski programi visokog intenzite- The desire to cure composite materials faster has
ta danas su zanimljivi zbog uštede vremena. No, lead to a growing interest in polymerization modes
pokazalo se da oni - ako je vrijeme osvjetljavanja of high intensity. However, it has been shown that
kratko - dovode do dostatnog ili čak nižeg stupnja these modes with short curing time lead to inade-
konverzije i lošijih fizičko-mehaničkih svojstava u quate or even lower degrees of conversion and poor-
odnosu prema kompozitnom materijalu polimerizi- er physical-mechanical characteristics compared to
ranom srednjim intenzitetom i dužim osvjetljava- composite materials polymerized with medium in-
njem (14). tensity and longer curing times (14).
Rezultati ispitivanja pokazali su najveći stupanj The results of this study have confirmed that the
konverzije kod uzoraka kompozitnog materijala po- highest degree of conversion was in composite res-
limeriziranog SOFT programom Bluephase 16i ure- in samples polymerized with SOFT mode of Blue-
đaja (68,59% za TC), što se i moglo očekivati, jer phase 16i curing unit (68,59% for TC), because the
je najveći intenzitet dulje primijenjen. Najniži stu- highest intensity was applied in a longer time. The
panj konverzije dobiven je tijekom polimerizacije lowest degree of conversion was achieved in the
uređajem najnižeg intenziteta i primijenjene ener- case of composite resin samples polymerized with
gije - Bluephase C5 (57,31% za TEC). Ne uzimaju- a curing unit of low intensity, or low applied energy
ći u obzir vrstu kompozitnog materijala, nego samo - Bluephase C5 (57,31% for TEC). When only con-
polimerizacijski program i intenzitet, iste rezulta- sidering the polymerization mode and light intensi-
te stupnja konverzije nalazimo i kod drugih auto- ty, not the type of composite material, the same re-
ra (4,5). sults of degree of conversion are found in studies by
Osim svojstava izvora svjetla, na kvalitetu po- other authors (4,5).
limerizacije znatno utječu sastav kompozitnog ma- Besides the light source characteristics, the com-
terijala te vrsta fotoinicijatora. Kamforkinon (468 position of composite material and the type of pho-
nm) je najčešći fotoinicijator u sastavu kompozit- to initiator, also significantly influence the polym-
nih materijala. Osim njega, fenil propan dion i luci- erization quality. Camforquinone (468 nm) is the
rin ( aktiviraju se na nižim valnim duljinama od 410 most common photo initiator in composite mate-
do 430 nm) također mogu biti u sastavu kompozit- rials. However, phenyl propane dion and lucirin,
nih materijala, posebice tzv. “bleching” boja i tran- which are activated at lower wavelengths (410-430
sparentne nijanse (15). Kod takvih materijala upit- nm), can also be found in composite materials, es-
na je polimerizacija nekim starijim LED-uređajima pecially in bleaching and transparent shades (15).
s užim spektrom emitiranih valnih duljina, čime je For these materials, polymerization with LED cur-
bila onemogućena aktivacija spomenutih fotoinici- ing units of earlier generation is questionable, due to
jatora. To bi moglo biti objašnjenje za niži stupanj narrower spectra of the emitted wavelengths, which
konverzije kod polimerizacije TEC kompozitnog enables activation of the mentioned photo initiators.
materijala, bez obzira na to o kojem se izvoru svje- This could be the explanation for lower degree of
tla i polimerizacijskog programa radi. Naime, TEC conversion of TEC composite material polymeriza-
prema uputama proizvođača, u svojem sastavu, tion, regardless of the light source or polymeriza-
osim kamforkinona, ima i lucirin kao koinicijator. tion mode. Besides camforquinone, TEC has lucirin
Energija emitirana iz polimerizatora ima isti as a co-initiator, as instructed by the manufacturer.
utjecaj na temperaturni porast kao što ga ima i na Energy emitted from the curing unit has the same
stupanj konverzije. Prema stajalištu Loneya i Pri- influence on temperature rise as it has on the degree
ca (10), razlika u energiji znatno utječe na tempera- of conversion. According to Loney and Price (10)
Knežević et al. Conversion of Composite Materials and Temperature Rise  27
turni porast, ovisno o primijenjenom polimerizacij- the energy difference has a high impact on temper-
skom programu. ature rise depending on the polymerization mode
Rezultati ovog ispitivanja pokazali su povezanost used. The results of this study have shown the con-
stupnja konverzije i temperaturnog porasta - najveći nection between degree of conversion and tem-
temperaturni porast zabilježen je kod polimerizacije perature rise; the highest temperature increase and
SOFT i HIGH polimerizacijskim programom Blu- highest degree of conversion were recorded in the
ephase 16i, uređaja kod kojeg je postignut i najve- polymerization with SOFT and HIGH polymeriza-
ći stupanj konverzije. Isto tako, najniži stupanj kon- tion modes of the Bluephase 16i curing unit. At the
verzije i najniža temperatura postignuti su tijekom same time, the lowest degree of conversion and the
polimerizacije uzoraka kompozitnog materijala ure- lowest temperature rise were achieved in polymer-
đajima najnižeg intenziteta - Bluephase C5 te LOW ization of composite resin samples with curing units
programom Bluephase C8 uređaja. Zanimljivo je of lowest light intensity - Bluephase C5 and LOW
istaknuti isti način ponašanja SOFT i HIGH poli- mode of Bluephase C8 curing unit. It is interesting
merizacijskog programa, bez obzira na to o kojoj se to note almost equal behavior of SOFT and HIGH
vrsti svjetla ili točnije, intenziteta radi. Tako se, na polymerization programs despite the curing unit
primjer, analizirajući rezultate postignute polimeri- or light intensity used. For instance, observing the
zatorom Bluephase C8 za SOFT i HIGH program, Bluephase C8 curing unit, the same conclusion for
može izvesti isti zaključak kao i za SOFT i HIGH SOFT and HIGH program as for SOFT and HIGH
program Bluephase 16i uređaja - kako za tempera- programs of the Bluephase 16i unit can be made, for
turu tako i za stupanj konverzije. Rezultati ovog is- both temperature rise and degree of conversion. The
pitivanja slažu se s rezultatima mjerenja temperatu- results of this study match the results of tempera-
re Aguiara i njegovih suradnika (16) - oni su također ture measuring reported by Aguiara et al. (16), who
dobili najveći porast temperature tijekom polimeri- also recorded the highest temperature rise when
zacije uzoraka SOFT programom. Razlog za to su, SOFT polymerization mode was used for photo po-
osim jakosti polimerizatora, i produljeno vrijeme lymerization of composite resin. Reasons for this
osvjetljavanja iako je taj polimerizacijski program are: a long curing light intensity and the extended
prema istraživanjima nekih autora, pokazao najbo- curing time. However, this polymerization mode
lje rezultate za ublažavanje polimerizacijskog sku- showed the best results in decreasing polymeriza-
pljanja i stresa nastalog zbog skupljanja (7,16-20). tion shrinkage and stress produced during shrink-
Ranije generacije LED-uređaja imale su manji age (7,16-20).
porast temperature u odnosu prema rezultatima no- Earlier generations of LED curing units record-
vijih LED polimerizatora dobivenih u ovoj studiji ed lower temperature rise compared to the results of
(4,98 do 8,35 ˚C) (1,21). Prema istraživanjima Za- recent LED curing units gain in this study (4.98 to
cha i Cohena (22), već porast temperature od 5,5 8.35 ˚C) (1,21). According to research by Zach and
˚C može rezultirati ireverzibilnim promjenama u Cohen (22), temperature rise of 5.5 ˚C could already
pulpnom tkivu. result in irreversible changes in pulp tissue.
Velik utjecaj na vitalnost pulpe, osim karakteri- Aside from the curing unit characteristics and
stika polimerizatora i sastava kompozitnog materi- the composition of the composite material, other
jala, ima dubina kaviteta te debljina preostalog den- important influences on pulp vitality are: the cavity
tina. Što je veća debljina zaostalog dentina, to je depth and the thickness of dentine towards pulp. The
manja mogućnost termičkog oštećenja pulpnog tki- thicker the dentine layer is, the lesser the chance for
va (15,22-24). thermic damage of the pulp tissue (15,22-24).
Samo na temelju rezultata mjerenja temperatu- Observing only the results of temperature and
re i stupnja konverzije, teško se može zaključiti ko- the degree of conversion measurement, it is diffi-
ji je od polimerizacijskih programa bolji. Za kona- cult to conclude which polymerization program is
čan zaključak potrebno je obaviti dodatna mjerenja the one with the best performance. For the final
polimerizacijskog skupljanja i stresa koji pritom na- and complete conclusion, polymerization shrinkage
staju. Iz svega spomenutoga jasno je da niz parame- and polymerization shrinkage stress should be per-
tara na koje je moguće donekle utjecati, pridonose formed. When all this is considered, it is clear that
kvaliteti i dugotrajnosti kompozitne restauracije. Na many relatively easy to influence parameters con-
kliničaru je da - ovisno o situaciji - prilagodi vrije- tribute to quality and longevity of composite res-
me i jakost polimerizacije kako bi se uz maksima- in restoration. Depending on the clinical situation,
28  Knežević i sur. Konverzija kompozita i temperaturni porast

lan učinak konverzije postigle najmanje moguće ne- it is up to the practitioner to adapt polymerization
gativne posljedice fotopolimerizacije kompozitnog time and intensity, which ensures maximal degree
materijala. of conversion and minimal negative effects of com-
posite material photopolymerization.

Zaključak Conclusion
Rezultati ovog ispitivanja pokazali su jedna- Results of this study show the same behavior for
ko ponašanje rezultata stupnja konverzije i tempe- the degree of conversion and temperature rise with
raturnog porasta kod pojedinih polimerizacijskih individual polymerization modes. The highest de-
programa. Najveći stupanj konverzije i temperatu- gree of conversion and the highest temperature rise
re zabilježen je kod uzoraka kompozitnih materijala was recorded when composite resin samples were
polimeriziranih polimerizacijskim programom naj- polymerized with curing modes of the highest in-
višeg intenziteta, a najniži kod programa najslabi- tensity, while the lowest results were recorded when
jeg intenziteta. the lowest light intensity mode was used.

Zahvala Acknowledgement
Rad je pripremljen u sklopu projekata 065- The study was supported by Grants 065-0352851-
0352851-0410, 098-0982904-2952 i 035-0352851- 0410, 098-0982904-2952 and 035-0352851-2857,
2857 Ministarstva znanosti, obrazovanja i športa of the Ministry of Science, Education and Sports of
Republike Hrvatske. Zahvaljujemo Ivoclar Viva- the Republic of Croatia. The authors would like to
dentu (Schaan, Liechtenstein) za kompozitne ma- thank Ivoclar Vivadent (Schaan, Liechtenstein) for
terijale i polimerizatore korištene u eksperimentu. composite materials and curing units used in the ex-
Flaviju Panduru sa Stomatološkog fakulteta Južno- periment. The authors also express their gratitude
kalifornijskoga sveučilišta (University of Southern to Flavia Panduru (University of Southern Califor-
California, Dental School) zahvaljujemo za ispra- nia, Dental School) for the English language cor-
vak engleske verzije teksta. rections.

Abstract Received: May 31, 2007

The appearance of LED curing units for composite materials polymerization has al- Accepted: February 6, 2008
most completely replaced halogen curing units. The main disadvantage of halogen
curing units was a temperature rise during the polymerization. Earlier generations Address for correspondence
of LED devices made the temperature rise negligible. The newest generation of LED Alena Knežević
curing units makes a higher degree of conversion due to higher light intensity, but School of Dental Medicine
also brings to question the temperature rise during the composite materials polym- University of Zagreb
erization. Aim: The purpose of this study was to measure the degree of conversion Department of Endodontics and
and temperature rise in composite resin samples. Material and Methods: The sam- Restorative Dentistry
ples were polymerized by curing modes of different light intensity of four LED units: Gundulićeva 5, 10000 Zagreb
Bluephase, Bluephase C5, Bluephase C8 and Bluephase 16i (all units Vivadent, Tel. 00385 (0) 1 48 02 113
Schaan, Liechtenstein). The degree of conversion was measured by FTIR spectro- Fax. 00385 (0) 1 48 02 159
photometer, while for the temperature it was measured using the thermometer ELV ma505ak@yahoo.com
Pyroscan (Leer, Germany). Results: The highest degree of conversion was achieved
in the case of composite resin samples polymerized with soft-start mode (SOFT) of
Bluephase 16i unit, while the lowest degree of conversion was achieved in the case
of polymerization with Bluephase C5 curing unit. The highest temperature rise was
recorded in the case of composite samples polymerization with high intensity mode
(HIGH) and SOFT mode of Bluephase 16i, while the lowest in the case of polymeriza-
tion with low intensity mode (LOW) of Bluephase C8 unit. Conclusion: According to
the results of this study, it can be concluded that higher degree of conversion brings Key words
higher temperature rise, regardless of composite material used. Composite Resin; Polymers
Knežević et al. Conversion of Composite Materials and Temperature Rise  29
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