humedad y adhesion a esmalte y dentina

1. S 815
The Influence of Relative Humidity on the
Effect of Dentin Bonding Systems
Erik AsmussenVAnne Peutzfeldt'^
Purpose: The aim of the study was to measure the influence of reiative humidity of the ambient air on
bond strengtii to enamei and dentin of six different bonding systems, in this manner, the ro[e of the primer
solvent was assessed.
Materials and Methods: The bonding systems selected were Prime & Bond 2.1, One Step. Scotchbond
MP, Syntac Singie Component, Optibond Solo, and Perma Quick, The primers of these systems are based
on either acetone, water or ethanol. Plane enamei and dentin surfaces were placed at relative iiumidities
of 18%, 45%, 80% or 99% RiH and then treated in accordance with the recommendations of the respective
manufacturers. A resin composite was tiien bonded to tiie treated surfaces. After storage in water at 37''C
for 1 day, the bonded specimens were broi<en in shear.
Results: The bonds to enamei were either unaffected or in one case moderately increased by increasing
ambient humidity. The bonds to dentin were either unaffected or in four cases strongly reduced by increas-
ing humidity.
Conclusions: The response of the bonding systems to differences in ambient humidity were not reiated to
the solvent of the primer in a simple way. To exdude the damaging effect of high humidity on dentin bond-
ing, the use of rubber-dam is recommended.
J Adhesive Dent 2001;3:123-127. Stibmined for publication:10.05.00; acceptsd for publicaUon:26.02.01.
B
onding of resin composites to dentin is brought
about by the infiitration of resin monomers into
the surface of the dentin, as shown for the first
time by Nakabayashi et aA^ Following an acidic
conditioning of the dentin, the infiitration gives rise
to the formation of the so-called hybrid iayer. The
hybrid iayer is an intimate biend of collagen fibers
and a polymer originating from the infiltrated
monomer of the primer of the dentin bonding sys-
a Professor, Department of Dental Materials, School cf Dentistry,
Faculty of Health Sciences. University ot Copenhagen. Copen-
tiagen. Denmark.
° Associate Professor. Department of Dental Materials. School of
Dentistry. Faculty of Health Sciences. University of Copenhagen.
Copenhagen, Denmarh.
Reprint requests: Erik Asmussen, Departrrient of Denta/ Materials.
School of Dentistry. 20 Narre Alle, DK-2200 Copenhagen N. Den-
mark. Tei: +45-3532-6580, Fax: 4-45-3532-6505. e-maii: ea@
tem.^3 Later work has shown that the dryness of
the conditioned dentin may play a decisive role in
the penetration of the primerJ Excessive desicca-
tion of the dentinai surface will cause a collapse of
the coilagen fibers of the conditioned dentin sur-
face, which may interfere with the penetration of
the primer monomer."'^^ Several studies have
shown that this may be detrimental to dentin bond-
¡ng,2,6,io,i6,22 It has also been found that it is pre-
dominantly the primers based on acetone that are
susceptible to variations in the dryness of the
dentin surface, whereas primers based on water
and/or ethanol are influenced to a lesser degree by
the humidity of the dentin.i'5,6,22 Rewetting of dried
dentin before application of an acetone-based
primer has been found to restore bond strength to
the level obtained with moist dentin,i^
The humidity of the dentin may vary for several
reasons. Presumably, the principal reason is the in-
tensity of the drying procedure before the applica-
Voi 3, No 2, 2001
123

2. Asm ussen/ PeJtzfgldt
tion of the primer.^ Another source of moisture may
be tubular liquid originating from the pulpal pres-
sure.^i^is still another factor may be the humidity
of the air In the orai cavity. The relative humidity in
the oral cavity has been found to be in the range of
78% to 94% without the use of rubber-dam, and to
be close to the ambient humidity of the operatory
with the use of dam.is
The infiuence of relative humidity on the strength
of the bond between resin composite and dentin
has been investigated previously,i3'is,30 and it was
found that the bond strength decreased with in-
creasing humidity of the surrounding air. However,
these studies investigated acetone-free dentin
primers based on water and/or ethanoi. To the
knowledge of the present authors, no systematic
studies have been performed in which the influence
of relative humidity on bond strength was investi-
gated in reiation to the solvent of the primer of the
dentin bonding system.
In the early days of the acid-etch technique, it
was generally accepted that the enamel shouid be
thoroughly dried after being etched and rinsed.
Without sufficient drying, it was feared that remain-
ing water in the surface of the etched enamel couid
interfere with the mechanicai interlocking of the
enamei bonding agents. With the advent of dentin
bonding agents, which are also used as enamei-
bonding agents, this situation has changed be-
cause of the hydrophilicîty of the primers. The
primer itself may be water-based, or a certain
amount of water may be absorbed into primer with-
out affecting the strength of the bond.^
It was the aim of the present study to investigate
the influence of relative humidity on bond strength
to enamel and dentin in relation to the solvent of
the primer of the bonding system. Regarding the
dentin, we hypothesized that primers based on ace-
tone wouid resuit in bond strengths increasing with
ambient humidity of the air, whiie primers based on
ethanoi or water would not be affected or show re-
duced bond strength with increasing humidity. Re-
garding the enamel, we hypothesized that the bond
strength would be unaffected by ambient humidity.
MATERIALS AND METHODS
The bond strength to enamel and dentin of a resin
composite (ZIOO, 3M, St Paul, MN, USA] was mea-
sured as described earlier in detail.i"¡' Human mo-
lars were embedded in epoxy resin. After setting, a
flat enamel or dentin surface was produced by wet
grinding on carborundum paper #1000. The bond-
ing procedure took place in a transparent glove box,
in which the relative humidity of the air could be
controlied. Four series of measurements were per-
formed, with relative humidities of 18%, 45%, 80%,
and 99% RH, An 18% RH was obtained by drying
the air inside the glove box with siiica gel placed in
a number of open containers, 45% RH was the hu-
midity of the air in the laboratory, 80% RH was es-
tabiished by means of a saturated solution of
ammonium suifate placed In open containers," and
99% RH by simiiar use of plain water. In all cases,
the reiatlve humidity was measured and checked
with a hygrometer. The temperature was 22°C ±
2°C. Six different dentin bonding systems were se-
iected for the study. They were Prime & Bond 2.1
{DeTrey/Dentsply, Konstanz, Germany), One Step
(Bisco, Schaumburg, IL, USA), Scotchbond MP Í3M),
Syntac Single Component (Vivadent, Schaan,
Liechtenstein), Optibond Soio (Kerr, Orange, CA,
USA), and Perma Quick (Uitradent, South Jordan,
UT, USA). According to Information from the manu-
facturers, the first two bonding systems involve ace-
tone-based primers, the primers of the next two
systems contain water, and the primers of the last
two systems are based on ethanoi. Scotchbond MP
distinguishes itseif from the other dental adhesives
by having two steps (primer and adhesive) after
etching, while the other systems involve only one
step (primer and adhesive in one bottle). The dentin
bonding systems, which also served as enamel
bonding systems, were used in accordance with the
recommendations of the manufacturers. A split
Teflon mold (d = 3.6 mm, h = 2.8 mm) was clamped
to the treated tooth surface and the moid filled with
resin composite which was light cured for 60 s with
a ilght-curing unit (XL3000, 3M). The bonded speci-
men was freed from the moid and stored in water at
37°C for 24 h. The shear bond strengths were de-
termined with a Universal testing machine (Instron,
High Wycombe, UK) at a crosshead speed of 1
mm/min. A mean value and standard deviation was
calcuiated for the eight specimens in each of the
48 experimental groups.
Statistical Methods
The data were statistically analyzed with the Krus-
kai-Wallis analysis of variance,^!
124 The Journal of Adhesive Dentistry

3. Asmussen/Peutzfeldt
Table 1 Bond strength (MPa) to enamel in relation to relative humidity of ambient air*
Bonding system
Prime & Bond 2.1.
One Step
Scotchbond MP
Syntac SC
Optibond Solo
Perma Quick
-Bond strenghls shown as mear
18
34 ± 8.3
24-33-38
24 ± 2.2
23-24-25
22 ±3.4
19-23-24
25 ±5.5
20-24-25
20±3.5
16-19-22
20 ± 3.5
19-19-22
± SD; 25th-5OUi-75tli percentile.
Relative iiumidity {%)
45
31 ± 4.5
26-31-34
25 ± 3.1
22-24-28
23 ± 3.4
20-22-35
24 ± 4.4
18-24-27
20 ± 1.5
18-20-21
24 ±2.7
22-24-25
80
37 ± 6.4
34-39-40
23 ±2.2
21-22-23
25 ±3.9
20-25-28
21 ± 1.8
19-21-22
22 ± 3.6
19-24-25
23 ±4.9
19-22-26
99
35 ± 7.0
29-33-35
23 ± 4.3
22-23-24
20 ±4.1
17-20-22
20 ±3.8
18-19-31
26 ± 2.4
33-26-27
19 ± 3.8
16-20-21
Tabie 2 Bond strength (MPa) to dentin in relation to relative humidity of ambient air*
Bonding system
Prime & Bond 2.1
18
11 ± 2.2
9-12-12
10 ± 3.9
5-7-13
17 ± 4.6
12-16-17
22 ± 3.0
19-22-24
27 ± 2.8
25-27-30
10 ± 8.1
4-6-10
»Bond strenghts shown as mean t SD; 25t^^50tll-75th percentile.
Relative humidity (%)
45
12 ± 5.3
8-11-14
12 ± 4.7
1-9-16
16 ± 9.8
10-16-19
20 ±2.9
19-21-22
27 ± 1.5
26-26-28
17 ± 8.7
11-16-20
80
11 ±2.3
9-11-13
10 ± 2.6
8-911
15 ±5-2
11-13-17
13 ± 3.2
10-13-15
33 ±3.3
21-22-25
5 ±2.8
2-5-7
99
12 ±4.0
9-12-13
5 ±2.4
3-6-6
11 ± 5.9
4-13-15
8 ±2.8
4-7-10
18 ±3.9
15-17-20
5 ±4.3
Statistical
p > 0.05
p>0.05
p > 0.05
p > 0.05
p < 0.01
p>0.05
Statistical
p > 0.05
p<0.01
p>0.05
RESULTS
The results of the bond strength measurements are
presented in Tables 1 and 2. Table 1 gives the re-
sults of bonding to enamel; Table 2 gives the re-
sults of bonding to dentin. A statistical analysis by
means of Bartlett's test^ showed that the standard
deviations in many of the series could not be con-
sidered to be of equal size. Accordingly, the data
were treated with nonparametric statistics.^i
It oan be seen from Table 1 that the bond
strengths to enamel varied only moderately with the
relative humidity. Kruskal-Wallis analysis of vari-
ance showed a significant influence of humidity in
the case of Optibond Solo {p < 0.01), while the ef-
fect was not significant in the other groups.
Regarding the bond strengths to dentin shown in
Table 2. some of the bonding systems exhibited a
considerable variation in relation to humidity.
Kruskal-Wallis analysis of variance showed a signifi-
cant influence of humidity with four of the investi-
gated bonding systems: One Step (p < 0.01), Syntac
SC (p < 0.001), Optibond Solo (p < 0,01), and
Perma Quick (p < 0.001]. The influence was not sta-
Vol 3, No 2, 2001
125

4. Asmjssen/ PeutzfeIctt
tistically significant with Prime & Bond 2.1 or
Scotchbond MP{p>0.05).
DISCUSSION
it is evident from Tables 1 and 2 that the primer soi-
vent is not the oniy factor determining the effect of
humidity on the efficacy of the bonding systems in-
vestigated. Regarding bonding to enamei, it was
shown that the reiative humidity of the surrounding
air had an infiuence on the bonding in oniy one of
the six cases , and that this infiuence may be char-
acterized as moderate. On the otber hand, in four
out of six cases the humidity exerted a decisive in-
fiuence on bonding to dentin. This difference in be-
havior between enamei and dentin is probably
related to the fact that the prisms of the etched
enamei surface do not collapse or expand as a
function of water content as is the case with the
collagen fibers of the dentin surface, it may be as-
sumed that more water is adsorbed onto the
enamei surface as the humidity increases. The find-
ing that this water gave rise to a rather moderate In-
terference with bonding is in agreement with an
eariier study.^ As mentioned in the introduction, it
is probabie that the reason for this relative insensi-
tivity is the ability of the hydrophiiic bonding sys-
tems to absorb water in smali amounts, in the case
of Optibond Solo, an increase in bond strength was
found at 99% RH. The primer of Optibond Solo is
based on acetone and thus has a water-chasing ca-
pacity. But the observed increase in bond strength
in comparison to the drier conditions is difficult to
explain, and may tentativeiy be ascribed to a statis-
tlcai fiuotuation, however uniikeiy that may be.
Regarding bonding to dentin, no systematic dif-
ferences were found between the two acetone-
based systems and the water- or ethanoi-containing
systems. Contrary to what we hypothesized, the
bond strengths to dentin of Prime & Bond 2.1 and
One Step did not increase with increasing reiative
humidity, but rather decreased in the case of One
Step. One explanation may be that when the recom-
mendations of the manufacturers were followed,
the dentin surface was sufficientiy moist to prevent
collapse of collagen fibers, even in the driest of the
conditions. Thus, at high humidity too much water
would be present to give optimum bond strength,
as discussed below. Another tentative expianation
is that the dentin surface was left with coilapsed
collagen after drying, and that the "soaking time" at
high humidity before the primer was appiied was in-
sufficient to restore the collagen to an expanded
state. This expianation is backed by the results of a
pilot study in which we found the bond strength of
One Step to dentin to be significantiy higher when
the dentin was only blot dried, as opposed to the
drying procedure recommended by the manufac-
turer ("a brief burst of air").
Aithough not statistically significant in the case
of Scotchbond MP, the systems based on water or
ethanol suffered from significant reductions in
bond strength to dentin under the more humid con-
ditions. The reiativeiy smail reduction in bond
strength measured with Scotchbond MP may be re-
lated to the fact that this system is a muitistep
system, while the other systems are "One-bottie'
systems. The observed reductions in bond strength
are in agreement with eariier investigations of
water-based dentin bonding systems.^'^'^*' The rea-
son for the iow bond strengths may be that at high
humidity, the dentinai surface is insufficiently freed
of the water of the acid conditioning agent, with the
effect that too much water is present to give good
penetration and poiymerization of the primer mono-
mer. A possibility suggested by Nystrom et al^^ is
that the surface of the primer may be contaminated
with water at high humidity, with the effect of reduc-
ing the adherence to the resin composite, in fact,
when drying the primer with a stream of air, the
evaporation of soivent wiii cause the temperature
to drop, and the possibiiity exists that it may drop
beiow the dew point of the air. On the other hand, if
this were the case, it shouid also have occurred
when bonding to enamei, but a reduction in bond
strength to enamei with increasing humidity was de-
tected only in one case.
Since ail the investigated systems gave maxi-
mum bond strength at 45% RH of the operatory,
use of rubber-dam^s may be advisable in temperate
climates. This recommendation is in agreement
with that of a previous work. In countries with high
humidity, the data of the present investigation shew
that optimum bonding may be difficuit to achieve
uniess special precautions are taken.
REFERENCES
1. Charlton DG, Beatty MW. The effect of dentin surface mois-
ture or hond strength to dertin bonding agents. Opet Dert
1994;19;154-158.
126 The Journal of Adhesive Dentistry

5. Asmussen/ Peutzfeldt
De Goes MF, Pachane GCF, Garcia Godoy F. Resin bond
strength with different methods to remove excess water from
the dentin. Am J Dent 1997; 10;298-310,
Halo A. Statistical theory with engineering applications. New
York: John Wiley & Sons, 1952:290-299.
Handbook of Chemistry and Physics. Cleveland OH: The
Chemical Rubber Company, 1972-1973;E40,
Iwami y, Yamamoto H, Kawai K, Ebisu S, Effect of enamel
and dentin surface wetness on shear bond strength of com-
oosites. J Prosthet Dent 1998;S0.20-26,
Jacobsen T Söderholm K-J. Effect of primer solvent, primer
agitation, and dentin dryness on shear bond strength to
dentin. Am J Dent 1998; 11:225-228,
Kanca III J. Resin bonding to wet substrate, I. Bonding to
dentin. Quintessence Int 1992;23;39-41.
Kanca III J. Effect of resin primer solvents and surface wet-
ness on resin composite bond strength to dentin. Am J Dent
1992;5:213-215,
Kanca III J. Wet bonding: Effect of drying time and distance.
Am J Dent 1996;9:273-276.
Kanca III J, Sandrik J. Bonding to dentin. Clues to the mecha-
nism of adhesion. Am J Dent 1998; 11:154-159.
Mitchem JC, Terkia LG, Gronas DG, Bonding of resin dentin
adhesives under simulated physiological conditions. Dent
Mater 198S;4;351-353,
Nakabayashi N, Kojima K, Masuhara E, The promotion of ad-
hesion by the infiltration of monomers into tooth substrates,
J Blomed Mater Res 1982; 16:265-273.
Nystrom GP, Holtan JR, Phelps II RA, Becker WS, Anderson
TB, Temperature and humidity effects on bond strength of a
dentinal adhesive. Cper Dent 1998;23:138-143,
Pashley DH, Ciucchi B, Sano H, Horner JA, Permeability of
dentin to adhesive agents. Quintessence Int 1993;24:618-
631.
Pashley DH, The smear layer: Physiological considerations,
Oper Dent 1984;3;13-29.
Perdigäo J, Swift EJ, Heymann HO, Malek MA. Effect of s
rewetting agent on the performance of acetone-based dentin
adhesives. Am J Dent 1998;ll:207-213,
Peutzfeldt A. Asmussen E, Influence of eugenol-containing
temporary cement on efficacy of dentin bonding agents, Eur
J Oral Sei 1999;107:65-69,
Plasmans PJJM, Reukers EAJ, Vollenbrook-Kuipers L, Vollen-
brock HR, Air humidity: a detrimental factor in dentine adhe-
sion, J Dent 1993;21;22S-233,
Plasmans PJMM, Creugers NHJ, Hermsen RJ, Vrijhoef MMA.
Intraofal humidity during operative procedures. J Dent
1994;22:89-91,
Plasmans PJJM, Creugers NHJ, Hermsen RJ, Vrijhoef MMA.
The influence of absolute humidity on shear bond adhesion.
J Dent 1996;24;425-428,
Siegel S, Nonparametrio Statistics, Tokyo; McGraw-Hill, 1956,
Swift EJ, Bayne SC, Shear bond strength of a new one-bottle
dentin adhesive. Am J Dent 1997;10;184-18S.
Van Meerbeek B, Inokoshi S, Braem M, Lambrechts P, Van-
herle G, Morphological aspects of the resin-dentin interdiffu-
sion zone with different dentin adhesive systems, J Dent Res
1992;71; 1530-1540,
20.
Vol 3, No 2, 20Q1 127
New Frontiers in
Adhesive Dentistry
HYBRIDIZATION OF
DENTAL HARD TISSUES
HYBRIDIZATION OF DENTAL HARD TISSUES
Nobuo Nakabayashi and David ti. Pashley
The hybridization of dentin—a process that cre-
ates a molecular-level mixture of adhesive poly-
mers and dental hard tissues—gives dinicians a
versatile new material, useful in a wide array of
advanced dental treatments. As the first in-depth
exploration of the subject, this book covers the
development, present understanding, and future
research areas of this multifunctional dental mate-
rial. A thorough review of the current literature
rounds out the text.
Valuable for students, researchers, and clini-
cians seeking a greater understanding of resin
hybridization of tooth structure.
CONTENTS
7 Evolution of Dentin-Rcsin Bonding
2 Properties of Dencin
.Î Ac:id Conditioning and Hybridization of
Substrates
4 Characterization of the Hybrid Layer
5 The Quality of the Hybridized Dentin
6 Clinical Applications of Hybrid Layer
Formation
129 pp: 80 illus (some in color):
ISBN 0-874 ¡7-575-9 C3047; US S'IO/£26
To ORDER
Call+44 (0)2089496087
or Fax +44 (0)20 83 3614 84 book/
Visit our web site http://www.quintpub.com
Quintessence Publishing Co, Inc