Vesna MileticVesna Miletic1,21,2, Ario Santini, Ario Santini11

1 1 The University of Edinburgh, Edinburgh Postgraduate Dental Institute, The University of Edinburgh, Edinburgh Postgraduate Dental Institute, United KingdomUnited Kingdom2 2 University of Belgrade, School of Dentistry, SerbiaUniversity of Belgrade, School of Dentistry, Serbia

Effect of preparation and storage Effect of preparation and storage on adhesive monomer conversionon adhesive monomer conversion

Studies investigating the degree of conversion (DC) of Studies investigating the degree of conversion (DC) of adhesives - samples prepared in a variety of waysadhesives - samples prepared in a variety of ways

Substrates such as potassium-bromide pellet/crystal, acetate Substrates such as potassium-bromide pellet/crystal, acetate strips, glass slides or dentine discsstrips, glass slides or dentine discs

Light curing with or without the use of a Mylar strip covering Light curing with or without the use of a Mylar strip covering

Variations in storage parameters such as time, temperature, Variations in storage parameters such as time, temperature, humidity and mediahumidity and media

INTRODUCTION

To study the effect of preparation and To study the effect of preparation and

storage conditions on the DC of storage conditions on the DC of

two adhesive systems using two adhesive systems using

micro-Raman spectroscopy. micro-Raman spectroscopy.

OBJECTIVEOBJECTIVE

Sample preparation:Sample preparation:

Etch-and-rinse (Excite, Etch-and-rinse (Excite, Ivoclar VivadentIvoclar Vivadent) )

and self-etch adhesive (Clearfil 3S, and self-etch adhesive (Clearfil 3S, KurarayKuraray) )

n=5n=5

Glass slides vs. Dentine discsGlass slides vs. Dentine discs

Mylar strip covering vs. No Mylar strip coveringMylar strip covering vs. No Mylar strip covering

LED light (bluephase, LED light (bluephase, Ivoclar VivadentIvoclar Vivadent) intensity 650 mW/cm) intensity 650 mW/cm22, 10 s curing , 10 s curing time, 1 mm distancetime, 1 mm distance

MATERIALS AND METHODS

Sample preparation:Sample preparation:

Etch-and-rinse (Excite, Etch-and-rinse (Excite, Ivoclar VivadentIvoclar Vivadent) )

and self-etch adhesive (Clearfil 3S, and self-etch adhesive (Clearfil 3S, KurarayKuraray) )

n=5n=5

Glass slides vs. Dentine discsGlass slides vs. Dentine discs

Mylar strip covering vs. No Mylar strip coveringMylar strip covering vs. No Mylar strip covering

LED light (bluephase, LED light (bluephase, Ivoclar VivadentIvoclar Vivadent) intensity 650 mW/cm) intensity 650 mW/cm22, 10 s curing , 10 s curing time, 1 mm distancetime, 1 mm distance

MATERIALS AND METHODS

Micro-Raman spectroscopy Micro-Raman spectroscopy (5 min post-curing, 3 random spectra per sample, top surface)(5 min post-curing, 3 random spectra per sample, top surface)

MATERIALS AND METHODSMATERIALS AND METHODS

DC=[1-Rcured / Runcured] x 100

Storage conditions:Storage conditions:

Adhesives: Excite and Clearfil3S (n=5)Adhesives: Excite and Clearfil3S (n=5)

Glass slides / Dentine discsGlass slides / Dentine discs

Mylar strip coveringMylar strip covering

LED light (bluephase) intensity 650 mW/cmLED light (bluephase) intensity 650 mW/cm22, 10 s curing time, 1 mm , 10 s curing time, 1 mm distancedistance

Micro-Raman spectroscopy 5 min post-curing and after storageMicro-Raman spectroscopy 5 min post-curing and after storage

MATERIALS AND METHODSMATERIALS AND METHODS

Storage conditions (24 hours)Storage conditions (24 hours)

Group I (22±2ºC and 45±3% humidity) - Group I (22±2ºC and 45±3% humidity) - light proof container, laboratory benchlight proof container, laboratory bench

Group II (37±1ºC and 90±2% humidity) -Group II (37±1ºC and 90±2% humidity) -light proof container with side openings, water bath with punched light proof container with side openings, water bath with punched aluminum foil coveraluminum foil cover

Group III (distilled water at 37±1ºC) -Group III (distilled water at 37±1ºC) -glass vial, 1 ml distilled water, covered water bath glass vial, 1 ml distilled water, covered water bath

Group IV (artificial saliva at 37±1ºC) - Group IV (artificial saliva at 37±1ºC) - glass vial, 1 ml artificial saliva, covered water bath glass vial, 1 ml artificial saliva, covered water bath

MATERIALS AND METHODSMATERIALS AND METHODS

StatisticsStatistics

ANOVA and repeated measures ANOVAANOVA and repeated measures ANOVA

t testt test

significance level significance level αα=0.05=0.05

MATERIALS AND METHODSMATERIALS AND METHODS

Sample preparation - Excite

70.3

22.9

71.6

42.2

0

20

40

60

80

100

Glass, w/Mylar

Glass, w/oMylar

Dentine, w/Mylar

Dentine,w/o Mylar

Preparation method

De

gre

e o

f c

on

ve

rsio

n

(%)

RESULTS

Sample preparation - Clearfil 3S

50.0 45.3

80.270.7

0

20

40

60

80

100

Glass, w/Mylar Glass, w/o Mylar Dentine, w/ Mylar Dentine, w/o Mylar

Preparation method

Deg

ree

of c

on

vers

ion

(%

)

Sample storage Sample storage -- Excite - Excite - Glass slides Glass slides

Groups: high humidity, distilled water and artificial saliva => sample Groups: high humidity, distilled water and artificial saliva => sample deformation, impossible to obtain micro-Raman spectra from the top deformation, impossible to obtain micro-Raman spectra from the top surfacesurface

Group stored at 22±2ºC and 45±3% humidityGroup stored at 22±2ºC and 45±3% humidity

Before: DC=70.8%(1.7%)Before: DC=70.8%(1.7%)

After: DC=73.6%(1.8%) After: DC=73.6%(1.8%)

[paired t-test, p<0.05][paired t-test, p<0.05]

RESULTS

Sample storage Sample storage -- Clearfil 3S - Clearfil 3S - Glass slidesGlass slides

78.5 86.3

50.2 51.2

0

20

40

60

80

100

Before After Before After

22ºC, 45% humidity 37ºC, 90% humidity

Storage conditions

De

gre

e o

f c

on

ve

rsio

n

(%)

Group 1 Group 2

RESULTS

• Group 1: p<0.001• Group 2: p<0.001• Group 1 vs. Group 2 (before): p=0.208• Group 1 vs. Group 2 (after): p<0.001[t-test]

Sample storage Sample storage -- Excite - Excite - Dentine discsDentine discs

78.970.4 73.4 70.9 73.7 72.3 70.7

90.2

0

20

40

60

80

100

Before After Before After Before After Before After

22ºC, 45%humidity

37ºC, 90%humidity

37ºC, dist.water

37ºC, BIM

Storage conditions

De

gre

e o

f c

on

ve

rsio

n (

%) Group 1 Group 2 Group 3 Group 4

RESULTS

Before vs. After • Group 1: p=0.002• Group 2: p=0.007• Group 3: p<0.001• Group 4: p<0.001[repeated measures ANOVA and paired t test]

Sample storage Sample storage -- Clearfil 3S - Clearfil 3S - Dentine discsDentine discs

Repeated measures ANOVA Repeated measures ANOVA Factor “Medium”: p=0.507Factor “Medium”: p=0.507 Factor “Time”: p<0.001Factor “Time”: p<0.001 Interaction “Medium” x “Time”: p=0.190Interaction “Medium” x “Time”: p=0.190

79.788.9

79.189.2

80.389.9

79.592.5

020406080

100

Before After Before After Before After Before After

22ºC, 45%humidity

37ºC, 90%humidity

37ºC, dist. water 37ºC, BIM

Storage conditions

De

gre

e o

f c

on

ve

rsio

n (

%)RESULTS

Sample preparation and storage significantly affected the DC of the etch-and-rinse and self-etch adhesive

Differences in the effect of both preparation and storage were observed for the two adhesives

Oxygen inhibition on the adhesive surface was significantly reduced using Mylar strips

“Dark” cure during storage increased the initial DC due to consumption of C=C double bonds

Compared to storage in air, liquid media further increased the DC, most likely due to elution of monomers

CONCLUSIONS

Variables such as oxygen inhibition and elution should be eliminated as they do not represent the DC of the adhesive polymer

Non-dental models may be appropriate for comparing e.g. effects of curing lights/curing times on conversion but not for material comparison since the results may not be clinically relevant

CONCLUSIONS