©

Operative Dentistry, 2011, 36-1, 36-42

Comparative Evaluation
of Microleakage
Among Three Different

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Glass Ionomer Types

S Abd El Halim • D Zaki

Clinical Relevance
Microleakage was evident in all restorative materials. Improvement was made when
a resin-modified glass ionomer incorporated the benefits of nanotechnology.

ABSTRACT ionomer material used: Group (A): Ketac N100

Objectives: This study compared the microleak- glass ionomer, Group (B): Vitremer glass ionomer
age and adaptation of Class V cavity prepara- and Group (C): Photac Fil Quick glass ionomer.
tions restored with three types of glass-ionomer The restorative materials were used according to
materials as a function of time. Methods and their manufacturers’ recommendations. The
Materials: A total of 144 sound, freshly-extracted teeth were placed in one increment and photo-
human premolars were used for the study. One cured for 40 seconds. All of the restored teeth
clinician prepared all the teeth for Class V-type were then stored in artificial saliva. Each group
cavities on the buccal surface of each tooth. The was subdivided into three subgroups according
preparations measured 3 mm long, 2 mm wide to the testing periods (7, 30, 60 days). Next, they
and 1.5 mm deep, with the gingival margin in were thermocycled at 5°C-55°C for 100 cycles. The
dentin and the occlusal margin in enamel. All the teeth used for the dye penetration test were
prepared teeth were randomly divided into three immersed in 1% methylene blue solution for eight
groups of 48 teeth, according to the type of glass- hours. They were then sectioned longitudinally
in a bucco-lingual direction. The extent of dye
*Sahar Abd El Halim, PhD, lecturer, Misr University for Science penetration at the occlusal and gingival margins
and Technology, Department of Operative Dentistry, Cairo of each restoration was studied under a stereo-
Egypt microscope at 25x magnification. Randomly
Dalia Zaki, PhD, National Research Center, lecturer of Dental selected samples from each group were prepared
Material in National Research Center, Giza, Egypt for scanning electron microscopic evaluation.
*Reprint request: 70 Rabaa El Estismary, Nasr City, 11371, Dye penetration scores were analyzed using the
Egypt; e-mail: s_saeed03@yahoo.com SAS program, cross tabulation and Chi square
DOI: 10.2341/10-123-LR test. Results: The difference among the three
Abd El Halim & Zaki: Microleakage of Nanoglass Ionomer in Comparison to Two Different Glass Ionomer Types 37

groups was significant after immersion for 30 not usually associated with glass ionomers because the
days at the occlusal margin. Statistical analysis filler particle size can influence strength, optical prop-
also revealed significant differences between erties and abrasion resistance.5-6
group (A) and the other groups at the occlusal The majority of cervical lesions exhibit mixed cavity
margin after immersion for 60 days (p<0.05). At margins positioned in both enamel and dentin.7
the gingival margin, statistical analysis revealed Enamel possesses an important quantity of hydroxya-
significant differences between group (C) and patite and its organic tissue is in smaller proportions.
the other groups at the gingival margin after On the other hand, dentin is made of two different sub-
immersion for 60 days (p<0.05). strates: intertubular dentin, which is less mineralized,
Conclusion: The light-curing nanofilled glass and peritubular dentin, which is more mineralized.
ionomer (Ketac N100) showed the least The presence of water in dentin decreases surface

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microleakage. energy and prevents restorations from establishing
good mechanical retention.7
INTRODUCTION
The current study evaluated microleakage and the
There has always been a keen interest in the adapta- adaptation of Class V cavity preparations restored
tion of dental restorative materials to the walls of cav- with a nanofilled glass ionomer, a resin-modified glass
ities and the retentive ability of a material to seal the ionomer and a modified synthetic glass polyalkenoate.
cavity against the ingress of oral fluids and micro-
organisms. Microleakage around dental restorative METHODS AND MATERIALS
materials is a major problem in clinical dentistry. It A total of 144 sound, freshly obtained human premolars
may be defined as the clinically undetectable passage extracted for periodontal reasons were selected and
of bacteria, fluids, molecules or ions between a cavity used for the current study. Residual soft tissue was
wall and the restorative materials applied to it.1 This removed by scaling and storing the teeth in distilled
seepage can cause hypersensitivity of the restored water containing thymol crystals during the interval
teeth, tooth discoloration, recurrent caries, pulpal between extraction and their use in this in vitro study.
injury and accelerated deterioration of some restora- One clinician prepared all the teeth for Class V-type
tive materials. Most restorative materials show vary- cavities on the buccal surface of each tooth using an
ing degrees of marginal leakage because of dimension- 835-010-4 ML cylindrical diamond bur (Diatech Dental,
al changes and a lack of adaptability to cavity walls.2 Coltène Whaldent AG, Alstätten, Switzerland) under
Over the past 50 years, many changes have occurred air-water cooling. The bur was replaced every four
in the development and availability of restorative preparations. The preparations measured 3 mm long, 2
materials. Glass ionomer cements (GICs) are adhesive mm wide and 1.5 mm deep, with the gingival margin in
bio-active restorative materials with therapeutic dentin and the occlusal margin in enamel. All the pre-
action that were developed during the late 1960s. GICs pared teeth were randomly divided into three groups of
are advantageous for use in restorative dentistry due 48 teeth according to the type of glass-ionomer materi-
to their capacity to bond to dentin, fluoride release that al used, as follows:
helps remineralization, and biocompatibility. Due to Group (A): Ketac N100 (3M ESPE, St Paul, MN,
the match in coefficient of thermal expansion between USA); Group (B): Vitremer (3M ESPE) and Group (C):
the tooth structure and GICs, they provide good mar- Photac Fil Quick (3M ESPE). The commercial name,
ginal sealing, little microleakage and a high retention composition and manufacturer of the three materials
rate. Despite these advantages, conventional GICs used in this study are listed in Table 1.
have a number of clinical limitations, including pro-
longed setting time, dehydration during initial setting The restorative materials were used according to
and a rough surface texture that can hamper mechan- their manufacturer’s recommendations. The restora-
ical resistance.3 To overcome these shortcomings, a tive materials were placed in one increment, since the
light-cured resin-modified glass ionomer (RMGIC) was depths were less than 2 mm. They were photocured for
introduced in the early 1990s, which contains poly- 40 seconds using a visible Quartz-Tungsten-Halogen
merizable monomers and a photoinitiator in addition- light-curing unit (Cromalux 7050 [Mega-PHYSIK
al polyacrylic acid. Compared with conventional GmbH & Co KG, Megadenta, Germany] at
analogs, RMGICs have a longer working time, a rapid 500mW/cm2). The restorations were finished immedi-
set, improved appearance and translucency and high- ately with fine-grit finishing diamond burs and pol-
er early strength.4 ished with a graded series of flexible discs (Sof-Lex, 3M
ESPE). All the restored teeth were stored in artificial
Recently, a light-curing Nano-Ionomer restorative saliva (0.4g NaCl–0.4g KCl–0.795g CaCl2.2H2O–0.69g
was the first resin-modified glass-ionomer material Na2HPO4–0.005g Na2S. 9H2O–1g Urea + 1 L Deionized
developed with nanotechnology. It may add benefits water) pH (7.03) at body temperature.8 Each group was
38 Operative Dentistry

Table 1: The Commercial Name, Composition and Manufacturer of the Materials Used 2- Dye penetration in dentin
midway between the dis-
Materials Manufacturer Composition tance of the DEJ to the
Ketac N100 3M ESPE, St Paul, MN, USA Deionized water, blend, including axial wall
Light-Curing HEMA, a methacrylate-modified
Nano-Ionomer polyalkenoic acid.
3- Dye penetration up to the
Restorative Filler component: methacrylate axial wall
functional-fluoroaluminosilicate SEM Analysis
glass and nanomeres and nano-
clusters. Four randomly selected sam-
Vitremer 3M ESPE, St Paul, MN, USA The powder is a radiopaque, ples from each group were
fluoroaluminosilicate glass. The prepared for scanning elec-
liquid is a light sensitive, aqueous tron microscopic evaluation.

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solution of a modified polyalkenoic
acid.
The specimens were dehy-
drated and mounted on alu-
Photac Fil Quick 3M ESPE, St Paul, MN, USA The powder contains highly
polishable, radiopaque glass minum stubs, then gold-
particles (Na-Ca-Al- sputter coated. The SEM
Lafluorosilicate-glass) and amines (JEOL JXA-840A Electron
as activators for light-curing. probe Micro-analyzer SEM,
The liquid component contains
JOEL, Ltd, Tokyo, Japan)
copolymer acids (maleic and
acrylic acid), camphorquinone as was then used to assess mar-
an initiator of the light-curing and ginal adaptation of the three
selected glass ionomer compatible tested materials to tooth
monomers and oligomers. structure at 1500x magnifi-
cation.
then divided into three subgroups according to the test- Statistical Analysis
ing periods (7, 30, 60 days). They were then thermocy- The data were analyzed using the SAS program (SAS,
cled at 5°C-55°C for 100 cycles with a 20-second dwell 1988). Cross-tabulation and the Chi-square test were
time at each temperature and a 10-second transfer used to test the effects of the material within each time
time, for a total of 50 seconds per cycle. and the effect of time within each material on the dye
Preparation of the Teeth for Dye Penetration penetration score.
Test
RESULTS
The apices of the roots were sealed with modeling wax
and the whole tooth was covered with two layers of nail Figures 1 and 2 show the percentage of leakage scores
polish, leaving a 1 mm window all around the cavity at the occlusal and gingival margins for the three types
margin. The teeth were immersed in a 1% aqueous of glass ionomer that were examined after immersion
solution of methylene blue for eight hours, then for three different time periods and thermocycling.
removed from the dye, brushed thoroughly under tap Comparison of the dye penetration scores of the three
water for 30 seconds and the wax was removed with a glass-ionomer types (groups A, B and C) revealed no
wax knife.
The teeth were sectioned longitudinally in a bucco-lin-
gual direction through the center of the restorations
using a water-cooled low-speed diamond saw (Isomet,
Buehler, Ltd, Lake Bluff, IL, USA).
The section with the greater leakage was evaluated
with a stereomicroscope (M9, Wild Heerbrugg,
Switzerland) at 25x magnification by a single operator
who was blinded as to which group each sample came
from to determine the extent of dye penetration at the
occlusal and gingival margins. Scoring was done
according to the following criteria suggested by
Koenigsberg and others:9
0- No dye penetration
1- Dye penetration in enamel to the dentino-enamel
junction (DEJ) Figure 1. Prevalence of dye penetration scores of the three tested glass-
ionomer types during the follow-up period (occlusal).
Abd El Halim & Zaki: Microleakage of Nanoglass Ionomer in Comparison to Two Different Glass Ionomer Types 39

significant differences at the occlusal margin or the

gingival margin after immersion for seven days
(p<0.05). However, the difference was significant
among the three groups after immersion for 30 days at
the occlusal margin. Statistical analysis also revealed
insignificant differences between groups B and C,
while the difference was significant between these two
groups and group A at the occlusal margin after
immersion for 60 days (p<0.05).
At the gingival margin, statistical analysis revealed
no significant difference between groups A and B,

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while the difference was significant between these two
groups and group C after immersion for 30 days.
Statistical analysis also revealed insignificant differ-
ences between groups A and B, while the difference
Figure 2. Prevalence of dye penetration scores of the three tested glass- was significant between these two groups and group C
ionomer types during the follow-up period (gingival).
at the gingival margin after
immersion for 60 days
(p<0.05).
Regarding Ketac N100 (3M
ESPE) and Vitremer (3M
ESPE) glass-ionomer types,
the difference was significant
between specimens immersed
for 7 days, 30 days and 60 days
(p<0.05) at both the occlusal
and gingival margins, where
Figure 3. High resolution SEM micrograph of marginal adaptation of Ketac N100 glass ionomer type after leakage increased by increas-
immersion for Figure 3a: 7 days; Figure 3b: 30 days and Figure 3c: 60 days. (K) Ketac N100. (I) K/dentin ing the immersion time. On
interface. (D) Dentin. (G) Gap (1500x). the other hand, Photac-Fil
Quick (3M ESPE) revealed a
significant difference between
specimens immersed for seven
days and those immersed for
30 and 60 days, where no sig-
nificant difference resulted
between them at the occlusal
margins. The difference was
significant after the immer-
sion of Photac-Fil Quick for 7
Figure 4. High resolution SEM micrograph of marginal adaptation of Vitremer glass ionomer type after days, 30 days and 60 days at
immersion for Figure 4a: 7 days; Figure 4b: 30 days and Figure 4c: 60 days. (V) Vitremer. (I) V/dentin inter- the gingival margin.
face. (D) Dentin. (G) Gap (1500x). Figures 1 and 2 show that
Ketac N100 (3M ESPE)
allowed the least leakage at
both margins, followed by
Vitremer, then Photac-Fil
Quick.
Finally, statistical analysis
comparing the prevalence of
dye penetration scores at the
occlusal versus the gingival
Figure 5. High resolution SEM micrograph of marginal adaptation of Photac Fil Quick glass ionomer type
after immersion for Figure 5a: 7 days; Figure 5b: 30 days and Figure 5c: 60 days. (PH) Photac Fil Quick. (I)
margin within each material
PH/dentin interface. (D) Dentin. (G) Gap (1500x). and immersion time revealed a
significant difference between
40 Operative Dentistry

the occlusal and gingival margin in group A after cate glass and the polycarboxylic acid and 2) a light-
immersion for 7 and 30 days, while the difference was activated free radical polymerization of the methacry-
insignificant between the two margins after immersion late groups of the polymer and HEMA (2-hydrox-
for 60 days. On the other hand, there was insignificant yethylmethacrylate).13-15 Moreover, the actual bonding
difference between the two margins in groups B and C mechanism of RMGIs to tooth tissues has recently
at all the tested immersion time periods (p<0.05). been determined to be twofold by micromechanical
SEM Results interlocking 16-17 and chemical interaction.18-19
The basic bonding mechanism was an ionic attraction
Gaps between the tooth structure and cements were between two carboxyl (COO-) groups in the cement to
less in the Ketac N100 glass-ionomer type (Figure 3) calcium (Ca++) in enamel and dentin.20
than gaps found in the other two tested glass-ionomer Micromechanical interlocking is achieved by impreg-
types (Figures 4 and 5), regardless of the immersion nation of a partially-demineralized layer on the top of

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period. This finding was inconsistent with the dye pen- the dentin substrate, with a high-molecular-weight
etration values achieved. More gaps appeared in the polycarboxyl-based polymer.21 Additional bonding
Photac Fil Quick glass-ionomer type immersed for 60 mechanisms have been explored for the RM-GICs,
days (Figure 5c) than the other tested material types since the presence of resin suggests that bonding anal-
immersed for the same period (Figures 3c and 4c). In ogous to resin composite may occur; that is, resin tags
the three tested types of materials, the gaps were more into enamel and the establishment of a hybrid layer
obvious when increasing the immersion period. Higher from the hydrophilic HEMA.22
magnification of the bond interface of Ketac N100 spec- Light-activated polymerization is accompanied by a
imens stored for seven days showed an indistinct inter- certain degree of polymerization shrinkage that takes
face between the margin of the tooth structure and the place in the three tested materials.6-23 Vitremer and
restoration, suggesting that a chemical bond had Photac Fil Quick contain fluoroaluminosilicate glass,
formed between the GIC and tooth structure (Figure while the nanofilled glass-ionomer type contains fluo-
3a). It was also difficult to distinguish between the roaluminosilicate glass, together with nanomers and
tooth structure and Ketac N100 GIC-type due to its nanoclusters in the filler loading, which is approx-
nano microstructure. imately 69% by weight. The higher filler loading in the
nanofilled type may result in lower polymerization
DISCUSSION
shrinkage and lower coefficient of thermal expansion
The current study examined the microleakage of dif- of this type of glass ionomer, improving the long-term
ferent types of glass-ionomer restorations placed in bonding to tooth structure. An in vitro study has shown
Class V cavities using a dye penetration test. that a controversy exists as to whether slight polymer-
Microleakage is an important property that has been ization shrinkage is significant enough to disrupt the
used in assessing the success of any restorative mate- margin seal.24
rial used in tooth restorations.2-10 The higher leakage produced by the Photac Fil Quick
Thermocycling is a standard protocol in the restora- type may be due to the fact that no primer was used
tive literature when bonded materials are evaluated, with this type of glass ionomer, while the other types
simulating in vivo aging by subjecting bonded materi- get the benefit of using primer that is acidic in nature.
als to cyclic exposures of hot and cold temperatures.11 A Its function is to modify the smear layer and ade-
novel RMGI restorative filling material, Ketac N100 quately wet the tooth surface to facilitate adhesion of
(3M ESPE), has been developed, incorporating the ben- the material to the hard tissue; this is in agreement
efits of nanotechnology.12 with other studies that concluded conditioning plays a
As regards the occlusal margin, the results of the cur- greater role in achieving effective bonding with resin-
rent study showed no significant difference among the modified glass-ionomer cements.25 The Photac Fil
three tested types of glass ionomer after immersion for Quick type showed initial low leakage scores, but the
seven days. On the other hand, the difference was sig- leakage scores increased by increasing storage time,
nificant among the three tested groups after immer- indicating unstable bonding to tooth structure.
sion for 30 days. Moreover, there was a significant dif- With all of the tested materials, the results showed
ference between Ketac N100 and the other two tested higher leakage scores at the gingival margin than the
glass-ionomer types after immersion for 60 days. The occlusal margin and at different tested immersion
nanofilled type of glass ionomer (Ketac N100) showed times. This finding is in agreement with other studies
the lowest microleakage scores, followed by the resin- that concluded, while cavity preparations with enamel
modified glass ionomer (Vitremer), then the modified margins result in consistently stronger bonds, unique
synthetic glass polyalkenoate (Photac Fil Quick). challenges are encountered with dentin surface bond-
These types of glass ionomers are resin-modified glass ing due to enamel that is 92% inorganic hydroxyap-
ionomers, where two types of setting reactions occur: 1) atite and dentin that is 45% inorganic by volume.26-27
the acid-base reaction between the fluoroaluminosili- Statistical analysis showed a statistically significant
Abd El Halim & Zaki: Microleakage of Nanoglass Ionomer in Comparison to Two Different Glass Ionomer Types 41

difference in leakage between the occlusal and gingival 7. Santini A, Plasschaert A & Mitchell S (2000) Marginal leak-
margins with Ketac N100 after immersion for 7 and 30 age of filled dentin adhesives used with wet and dry bonding
days, while the difference was insignificant after techniques American Journal of Dentistry 13(2) 93-97.
immersion for 60 days. This may be explained by the 8. Robin A & Meirelis JP (2007) Influence of fluoride concen-
fact that the nanostructure of the nanofilled glass- tration and pH on corrosion behavior of titanium in artificial
saliva Journal of Applied Electrochemistry 37(4) 511-517.
ionomer type allowed for excellent wetting and adapt-
ability to the tooth surface, hence enhancing the chem- 9. Koenigsberg S, Fuk A & Grajower R (1989) The effect of
ical bonding. This fact was inconsistent with the scan- three filling techniques on marginal leakage around Class II
composite resin restorations in vitro Quintessence
ning electron microscope results, where it was difficult International 20(2) 117-121.
to distinguish between the nanofilled glass ionomer
and tooth structure. Since chemical bonding takes 10. Hollan JR, Nystrom GF, Douglas WH & Phelps RA (1990)
Microleakage and marginal placement of a glass-ionomer
place through a chelation reaction with calcium on the

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liner Quintessence International 21(2) 117-122.
surface of the tooth, its effect was more significant on
11. Nalcaci A & Ulusoy N (2007) Effect of thermocycling on
the occlusal side with an enamel margin than the gin-
microleakage of resin composites polymerized with LED cur-
gival side with only a dentin margin. The difference ing techniques Quintessence International 38(616) 433-439.
was insignificant between the occlusal and gingival
12. Croll TP (2007) Nanofilled resin-modified glass ionomer
margins after immersion for 60 days, indicating an restorative cement Contemporary Esthetics 11(9) 14-17.
unstable bonding where leakage eventually increased
at the occlusal margin. 13 Quo BC, Drummond JL & Koerber A (2002) Glass ionomer
microleakage from preparations by an Er/YAG laser or a
CONCLUSIONS high-speed handpiece Journal of Dentistry 30(4) 141-146.
Within the limitations of the current study, it could be 14. Rossi RR, Aranha AC, Eduardo CP, Ferreira LS, Navarro RS
concluded that: & Zezell DM (2008) Microleakage of glass ionomer restora-
tion in cavities prepared by Er,Cr:YSGG laser irradiation in
1- Leakage will eventually occur with all types of primary teeth Journal of Dentistry for Children 75(2) 151-
glass ionomer with an increase in immersion 157.
time. 15. Berzins DW, Abey S, Costache MC, Wilkie CA & Roberts HW
2- Photac Fil Quick glass ionomer showed the (2010) Resin-modified glass-ionomer setting reaction compe-
tition Journal of Dental Research 89(1) 82-86.
most leakage, followed by Vitremer glass
ionomer. The light-curing nanofilled type of 16. Tay FR, Smales RJ, Ngo H, Wei SH & Pashley DH (2001)
glass ionomer (Ketac N100) showed the least Effect of different conditioning protocols on adhesion of a
GIC to dentin Journal of Adhesive Dentistry 3(2) 153-167.
microleakage.
17. Yip HK, Tay FR, Ngo HC, Smales RJ & Pashley DH (2001)
Bonding of contemporary glass ionomer cements to dentin
(Accepted 1 November 2010) Dental Materials 17(5) 456-470.
18. Yoshida Y, Van Meerbeek B, Nakayama Y, Snauwaert J,
Hellemans L & Lambrechts P (2000) Evidence of chemical
References
bonding at biomaterial-hard tissue interfaces Journal of
1. Morabito A & Defabianis P (1997) Marginal seal of various Dental Research 79(2) 709-714.
restorative materials in primary molars Journal of Clinical
Pediatric Dentistry 22(1) 51-54. 19. Fukuda R, Yoshida Y, Nakayama Y, Okazaki M, Inoue S &
Sano H (2003) Bonding efficacy of polyalkenoic acids to
2. Mali P, Deshpande S & Singh A (2006) Microleakage of hydroxyapatite, enamel and dentin Biomaterials 24(11)
restorative materials: An in vitro study Journal of Indian 1861-1867.
Society of Pedodontics and Preventive Dentistry 24(1) 15-18.
20. Tyas MJ & Burrow MF (2004) Adhesive restorative materi-
3. Bona A D, Pinzetta C & Rosa V (2009) Microleakage of acid als: A review Australian Dental Journal 49(3) 112-121.
etched glass ionomer sandwich restorations Journal of
Minimum Intervention in Dentistry 2(1) 36-43. 21. Van Meerbeek B, De Munck J, Yoshida Y, Inoue S, Vargas M
& Vijay P (2003) Buonocore Memorial Lecture. Adhesion to
4. Katleen I M, Peter J & Mieke AA (2008) Microleakage of four enamel and dentin: Current status and future challenges
different restorative glass ionomer formulations in Class V Operative Dentistry 28(3) 215-235.
cavities: Er:YAG laser versus conventional preparation
Photomedicine and Laser Surgery 26(6) 541-549. 22. Coutinho E, Van Landuyt K, De Munck J, Poitevin A,
Yoshida Y, Inoue S, Peumans M, Suzuki K, Lambrechts P &
5. Xie D, Brantley WA & Culbertson BM (2000) Mechanical Van Meerbeek B (2006) Development of a self-etch adhesive
properties and microstructures of glass ionomer cements for resin-modified glass ionomers Journal of Dental
Dental Materials 16(2) 129-138. Research 85(4) 349-353.
6. Wadenya R, Smith J & Mante F (2010) Microleakage of 23. Chong BS, Ford TR & Watson TF (1991) The adaptation and
nano-particle-filled resin-modified glass ionomer using sealing ability of light-cured glass ionomer retrograde root
atraumatic restorative technique in primary molars New fillings International Endodontic Journal 24(5) 223-232.
York State Dental Journal 76(4) 36-39.
42 Operative Dentistry

24. Sidhu SK & Watson TF (1995) Resin-modified glass ionomer 26 Phair CB & Fuller JL (1985) Microleakage of composite resin
materials. A status report for the American Journal of restorations with cementum margins Journal of Prosthetic
Dentistry American Journal of Dentistry 8(1) 59-67. Dentistry 53(3) 361-364.
25. Cho S & Cheng AC (1999) A review of glass ionomer restora- 27. Swift E, Perdigão J & Heymann HO (1995) Bonding to
tions in the primary dentition Journal of the Canadian enamel and dentin: A brief history and state of the art
Dental Association 65(9) 491-495. Quintessence International 26(2) 95-110.

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