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Pediatric Dental Journal

journal homepage: www.elsevier .com/locate/pdj

Original Article

Application of a tooth-surface coating material to teeth withdiscolored crowns

Takashi Hashimura, Aya Yamada*, Tsutomu Iwamoto, Makiko Arakaki, Kan Saito,Satoshi Fukumoto

Division of Pediatric Dentistry, Department of Oral Health and Development Sciences, Tohoku University Graduate School of Dentistry,

Sendai 980-8575, Japan

a r t i c l e i n f o

Article history:

Received 10 December 2012

Received in revised form

4 March 2013

Accepted 6 March 2013

Available online 6 May 2013

Keywords:

Discolored teeth

Tooth coating material

S-PRG filler

Caries prevention

* Corresponding author. Tel.: þ81 22 717 838E-mail address: yamada-a@dent.tohoku.a

0917-2394/$ e see front matter ª 2013 Thehttp://dx.doi.org/10.1016/j.pdj.2013.03.011

a b s t r a c t

Crown discoloration of permanent teeth is caused by trauma, periapical lesions of the

deciduous teeth, pharmaceuticals, and systemic diseases. Crown discoloration has been

treated with bleaching or crown restoration. However, these methods are not appropriate

during the growth and development period of children.

In this study, we used BeautiCoat� (Shofu Inc., Kyoto, Japan), a tooth-surface coating

material that contains high levels of controlled-release fluoride, that temporarily im-

proves crown color. We evaluated the effect of the primer on tooth-surface characteristics

in addition to the coating agent’s shear bond strength, tooth-surface condition, and

duration of attachment. Additionally, we surveyed patients’ satisfaction with the color

improvement.

The results showed no adverse effects of the primer on the enamel surface. The coating

material itself showed a high degree of shear bond strength. Based on observations of

shedding and fracturing in clinical applications, we found that the coating material

maintained long-term attachment if applied under conditions of strict moisture prevention

and it avoided areas of occlusion. Treated children and their parents were highly satisfied

with the color improvement. These results suggest that this coating material is appropriate

for improving the color of discolored teeth during childhood.

ª 2013 The Japanese Society of Pediatric Dentistry. Published by Elsevier Ltd. All rights reserved.

1. Introduction reddish-brown coloring. Crowns can also be discolored by the

Esthetic problems due to discolored crowns are common in

pediatric clinical practice. Causes of crown discoloration

during the formation of permanent teeth include periapical

lesions due to severe cavities in deciduous teeth and enamel

formation disorders due to tooth trauma. Discoloration ranges

from white spots in mild cases to substance loss with dark

2; fax: þ81 22 717 8386.c.jp (A. Yamada).Japanese Society of Pedia

use of tetracycline antibiotics or systemic diseases during the

tooth formative period [1,2].

Such crown discoloration can be treated in adults with

crown restoration methods, such as resin, laminating ve-

neers, facing crowns, and bleaching treatments. However, it is

difficult to achieve esthetic improvement in young children

during their period of growth and development usingmethods

tric Dentistry. Published by Elsevier Ltd. All rights reserved.

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 4 4e5 0 45

intended for adults. For instance, almost all at-home and in-

office bleaching procedures are not intended for young chil-

dren. Further, the use of irreversible crown restoration treat-

ments that require tooth preparation is not appropriate in

young children, because the gingival margin height has not

stabilized while the teeth are erupting or while the alveolar

bone is still forming. Therefore, a temporary treatment for

young children with crown discoloration is needed.

One such method is the “tooth manicure,” which uses ma-

terials that improve the color of teeth in a single day. However,

the organic solvents used in nail manicures are difficult to use

insidetheoralcavity; therefore, theeffects last foronly1e2days,

and it is difficult to maintain long-term color improvement.

In 2004, White Coat� (Kuraray Medical Co., Osaka, Japan)

was developed, which is a tooth-coatingmaterial for exclusive

use in dental clinics. This material uses a self-etching primer,

and its adhesion durability is about 1 month. This product has

better durability compared to over-the-counter tooth mani-

cures [3,4].

Progress has since beenmade in developingmaterials with

better durability and good physical properties that cause little

damage to the tooth. Surface reaction type pre-reacted glass

ionomer (S-PRG) filler has been developed, which possesses

physical strength and high levels of controlled-release fluo-

ride [5]. The tooth-surface coating material BeautiCoat�(Shofu Inc., Kyoto, Japan) contains this filler and is currently

used to treat discolored crowns [6]. Dental materials using S-

PRG filler include sealant materials [7], composite resin, or-

thodontic resin bonding system [8], denture base resin [9,10],

and root canal sealer [11]. Through the release and recharge of

fluoride and various other ions, cavities can be prevented in

the area of repair and neighboring teeth, and the adhesion of

plaque to the tooth surface can be suppressed [12,13].

This study investigated the shear-adhesion strength and

durability of BeautiCoat� in the oral cavity aswell as the effect

of its tooth-surface primer on enamel surface characteristics.

Finally, a survey of patient satisfaction with color improve-

ment was also conducted.

2. Materials and methods

2.1. Effect of the primer used in the tooth-surfacecoating material on enamel surface characteristics

Bovine tooth enamel specimens were subjected to no treat-

ment, the BeautiCoat� Primer treatment (3 s), or 37% phos-

phoric acid etching treatment (30 s). Enamel surface

characteristics were then observed and analyzed with a

scanning electronmicroscope (SEM; VE-7800, Keyence, Osaka,

Japan) under gold-evaporated conditions.

2.2. Evaluation of shear bond strength of the tooth-surface coating material

Enamel, dentin, metal, and porcelain were prepared under the

following conditions before shear bonding strength (SBS) test.

A bovine tooth surface was placed in an acrylic ring, and the

ring was embedded in epoxy resin. The bovine tooth surface

was polished using #600 SiC paper to expose enamel or dentin.

Precious metal (a gold-silver-palladium alloy) was polished

using #600 SiC paper, and the sandblast was applied to the

surface of metal using alumina-sand of 50e100 mm. Porcelain

was polished using #600 SiC paper to expose flat surface.

The surface of bonding specimen was treated according to

the bonding method recommended by the manufacturer. A

mold (4 mm diameter, 0.2 mm height) was fitted onto the

treated surface, filled with the coating material paste (BW2)

and light-cured to obtain a test specimen for SBS testing. After

being stored in water at 37 �C and 2000 thermal cycling

(4e60 �C), the specimen was evaluated for its SBS before and

after thermal cycling using a universal testing machine.

2.3. Clinical evaluation of the tooth-surface coatingmaterial

BeautiCoat� was applied to the teeth of 30 subjects (38 teeth;

upper central incisors and upper lateral incisors) with crown

discoloration believed to be caused by trauma or periapical

lesions of the deciduous teeth under the informed consent

from all parents. The patients were treated at the pediatric

dentistry department of Tohoku University Hospital (Miyagi

Japan) and Hashimura Dental Clinic (Saga, Japan).

The surfaces of the affected teeth were cleanedwith a low-

speedconebrush. PrimerAandprimerBwereplaced inadish1

drop at a time and mixed with a disposable chip brush. The

mixed liquid was applied to the surface of the teeth. It was left

in place for 3 s or more and was then dried with low-pressure

air. Next, the previously selected color-tone paste (white

base, BW1e4; white opaque, WO/paint color; yellowish, A0.5,

A3) was applied uniformly to the surface of the tooth using a

special BCapplicator. Thiswas irradiated for 20 susingavisible

light-curing unit (G-light, GC, Tokyo, Japan), and the non-

polymerized layers were removed with dry gauze. Finally,

Gloss Refine (Shofu Inc., Kyoto, Japan) was applied to the tooth

surface, which was then polished with a buffing disk and

washed.

For the clinical evaluation of the tooth-surface coating

material, shedding and partial fracturing of the tooth surface

were observed at 1 week, 1 month, and 3 months after coating

treatment. Photographs of the oral cavity were taken to eval-

uate fractures. Fractured areas covering less than 5% of the

surface area of the labial side of the tooth were classified as

small fractures, and those covering 5% or more of the surface

were classified as fractures.

During observation, affected teeth in which fractures

occurredwere re-coated; at thispoint, these teethwereexcluded

from the study. Moreover, if a tooth’s color made it difficult to

determine the presence of fractures through photographs or

surveys, a replica was made from a silicone impression, which

was then observed with a stereomicroscope (SZX12, Olympus,

Tokyo, Japan).

2.4. Satisfaction survey regarding the tooth-surfacecoating material

A questionnaire was administered to the 30 affected children

and their parents. The questionnaire contained questions

concerning the level of satisfaction with the tooth-surface

coating material treatment of discolored teeth. The subjects

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 4 4e5 046

were surveyed immediately after the coating treatment, 1

month after treatment, and 3 months after treatment. The

possible responses were: a) very satisfied, b) satisfied, c)

neutral, and d) not satisfied.

Fig. 2 e The shear bond strength of the tooth-surface

coating material to enamel, dentin, precious metal,

porcelain, and resin were evaluated.

3. Results

3.1. Effect of the primer used in the tooth-surfacecoating material on enamel surface characteristics

We evaluated the effect of the primer that is used before

applying the tooth-surface coating material on enamel sur-

face characteristics. To examine the effect of primer on tooth,

the primer was applied to the enamel surface of bovine teeth.

After performing gold-evaporation treatment, the enamel was

observed under a SEM. The enamel surfaces treated with a

37% phosphoric acid solution displayed decalcification, and

the enamel rods were exposed as in previous reports (Fig. 1C).

However, in the group treated with the primer, there was no

marked decalcification of the enamel surface, and the surface

characteristics were similar to the control (untreated) group

(Fig. 1A and B). These results suggest that this primer has few

adverse effects on the enamel.

3.2. Evaluation of shear bond strength of the tooth-surface coating material

In order to evaluate the SBS of the tooth-surface coating ma-

terial, the material was bonded to enamel, dentin, precious

metal, and porcelain using a brass ring, after which the SBS

wasmeasured. SBS of 10MPa ormorewas observed in enamel

and dentin 24 h after adhesion. Maintenance of high bond

strength was confirmed in the group that received thermal

Fig. 1 e Scanning electron microscope micrographs of the enam

are the enamel surfaces after treatment by BeautiCoat� Primer (

30 s respectively.

cycle treatment as well. SBS in precious metal and porcelain

was inferior to that of enamel and dentin (Fig. 2), but the

tooth-surface coating material displayed sufficient SBS more

than 10 MPa after a thermal cycle.

3.3. Clinical evaluation of the tooth-surface coatingmaterial

After applying the tooth-surface coating material, shedding

and fracturing of the tooth surface were investigated. The

coating material was applied to the teeth of 32 subjects (38

teeth). Of these, investigations were conducted in 30 subjects

(36 teeth) 1 week after application, in 26 subjects (31 teeth) 1

month after application, and in 21 subjects (25 teeth) 3months

after application. Shedding and fracturing were observed in 5

of 36 teeth (13.9%) 1 week after applying the tooth-surface

el surface. (A) is the non-treated enamel surface. (B) and (C)

Shofu Inc., Kyoto, Japan) for 3 s and 37% phosphoric acid for

Table 1 e Frequency of shedding and fracturing of thetooth-surface coating material.

Patientno.

Toothno.

None Fracture(5%<)

Fracture(5%>)

Fallout

1 week 30 36 31 (86.1%) 3 (8.3%) 2 (5.6%) 0 (0%)

1 month 26 31 21 (67.7%) 8 (25.8%) 1 (3.2%) 1 (3.2%)

3 months 21 25 17 (68.0%) 5 (20.0%) 3 (12.0%) 0 (0%)

Fig. 4 e Satisfaction with the tooth-surface coatingmaterial

was investigated immediately after the procedure, and 1

month after, and 3 months after.

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 4 4e5 0 47

coating material, 10 of 31 teeth (32.2%) 1 month after, and 8 of

25 teeth (32.0%) 3months after (Table 1). Most of the fracturing

was observed on the incisal margin and cervix of the incisors

(Fig. 3). In 1 case, there was complete shedding of the coating

material from the tooth surface, which occurred at 1 month

after application. In this case, the child was not satisfied with

the color of the application. The child attempted to remove

the coating material, which resulted in complete shedding of

the material. Thus, there were no cases of complete shedding

under normal conditions.

3.4. Satisfaction with the tooth-surface coating material

The affected teeth mainly involved white turbidness of the

labial surface of the upper incisors, tooth substantial defect in

the crown, or generalized crown discoloration caused by pulp

necrosis due to trauma. The subjects reported being “very

satisfied” and “satisfied” in 23 of 24 cases (95.8%) immediately

after the procedure, in 19 of 20 cases (95.0%) 1 month after,

and in 17 of 17 cases (100%) 3 months after (Fig. 4).

Although this is a preliminary study, color improvements

after treatment with the tooth-surface coating material were

examined in different cases. In one case involving white

turbidness of the labial surface of the tooth, there was a

marked difference in color on the borders of the turbid and

normal areas. Applying a highly transparent paint did not

Fig. 3 e Shedding and fracturing of the tooth-surface coating ma

is frontal view of fractured materials, and (B) is another case. (B

sufficiently improve the tooth color, and the parent was not

satisfied with the result. Therefore, a white base with a lower

level of transparency was applied to the border areas to

obscure their edges, and the paint colorwas then applied. This

improved the parents’ level of satisfaction.

In a case involving brown-colored enamel hypoplastic

defect accompanied by substance loss of the labial surface of

the tooth, the white base with the lowest transparency, BW3,

was applied. After this, paint color A3 was used, which

resulted in color improvement (Fig. 5).

Fig. 6 shows a case inwhich trauma to the upper-left lateral

and central deciduous incisors at age 1 year 6 months led to

early loss of the tooth from pulp necrosis, which caused early

eruption of the permanent tooth (upper central incisor) at age

4 years 3 months. The prior trauma caused spots on areas of

low enamel formation. As there was a difference in color

terial from the tooth were observed using replica model. (A)

-a): frontal view and (B-b) is incisal view.

Fig. 5 e Clinical cases before and after treatment by the tooth-surface coating material to the case with white-colored

enamel hypoplastic defect.

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 4 4e5 048

between the crown of the permanent tooth and the deciduous

teeth, the subject desired color improvement of the anterior

teeth. Paint color A0.5, which was close to the crown color of

the deciduous teeth, was applied to the surface of the per-

manent tooth. Coating of the permanent tooth crown with A3

led to an even higher level of satisfaction. In this case, because

the tooth-surface coating was performed during eruption of

Fig. 6 e Clinical cases before and after treatment by the tooth-s

permanent tooth caused by the trauma of deciduous tooth.

the tooth, a difference in level between the tooth-gingival

margin and the coating material was observed on the labial

side of the tooth cervix 10 months after application. Further, a

microscopic fracture was observed on the mesial periphery of

the coating material. This fractured area was re-coated, and

no fracturing was observed 4 months later. However, a new

fracture was observed in the incisal margin (Fig. 7).

urface coating material to the case with discolored

Fig. 7 e Clinical progress of the case treated by the tooth-surface coating material for the erupting tooth. This is the same

case as that shown in Fig. 6.

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 4 4e5 0 49

4. Discussion

S-PRG filler was developed as an advanced material that can

recharge and release fluoride and other ions. This PRG filler

possesses the excellent characteristics of both resins and glass

ionomer cements through its incorporation of resin-type

materials [14]. These materials are generally termed “giomer

products,” which are currently sold as composite resin,

bonding material, resin cement, sealant material, tooth-

surface coating material, and bonding material for use in

teeth straightening [15]. Furthermore, recent developments in

tooth-surface treatment agentshave led to the development of

tooth-surface coating materials that use self-etching primers.

These have allowed for relatively long-term retention of the

coatingmaterials on the tooth surface. This study investigated

a tooth-surface coating material that uses a self-etching

primer containing this S-PRG filler to treat teeth with dis-

colored crowns, which are frequently observed in pediatric

clinical practice.

The primer for the tooth-surface coating material used in

this study uses a methacrylate monomer 6-methacryloxyhex-

ylphosphonoacetate with an acidic base and an adhesive

monomer that is resistant to moisture. Observation under a

SEM demonstrated that this primer did not cause marked sur-

face decalcification of the enamel, and there was little damage

to the enamel. Thus, this gentle tooth-surface treatment ma-

terial is appropriate for use in the immature permanent teeth of

childhood. Further, the tooth-surface coating material had

sufficiently high bonding strength in shear bond tests and even

possessed high bonding strength with metal and porcelain

surfaces. This material is applicable for the repair of porcelain

fractures or discoloration as well as the esthetic improvement

of metal repairs. However, as this material has less bonding

than resin-type materials, it is a temporary method.

In actual clinical applications, apart from a single case where

the child intentionally removed the coating, no cases of natural

sheddingwere observed during 3months of observation. In cases

where fracturing occurred, the fractures appeared mostly in the

incisal margins involved in occlusion. However, there were no

malocculusions, suchastheedge-to-edgeocclusionandcrossbite

in these subjects. This suggests that fracture of coatingmaterials

could be prevented by avoiding the incisal margin during the

coating procedure. In fractures near the gingival margin, perme-

ation of liquid from the gingival sulcus likely influenced bonding

strength;however, fractureswereprevented inthisareawhenthe

procedure was conducted under complete moisture prevention.

Therefore, more stable, long-term tooth-surface coating can be

achieved by completely preventingmoisture using a rubber dam

and adjusting the extent of coating in the incisal margin area.

Furthermore, this tooth-surface coating material contains

S-PRGfiller, which can suppress bacterial plaque adhesion and

can recharge and control the release of fluoride and other ions.

The cavity-preventing effect of fluoride ions iswell known, but

of other ions released by this filler, strontium ions are partic-

ular in their ability to resist acid release from dental plaque,

inhibit bone resorption, promote bone formation, induce

calcification in dentin, and seal dentinal tubules [7,16e19].

Based on these functions, coating tooth surfaces with this

material not only achieves esthetic improvement, but also can

increase acid resistance, remineralization, and suppress adhe-

sion of plaque and bacteria to the tooth surface [6]. Further, this

material showed higher fluoride release compared with con-

ventional sealant, but not glass ionomer cement (data not

shown). Thus, this coatingmaterial not only covers the surface,

but can also contribute to cavity prevention in the surrounding

area, which makes it appropriate for use in childhood. Indeed,

discolored portions of teeth have low calcification, and the

cavity rate tends to be high. Nevertheless, therewere no cavities

observed in the affected teeth treated with this tooth-surface

coating or in the neighboring teeth.

Moreover, tooth discoloration caused by tetracycline anti-

biotics darkens over time due to the effect of ultra-violet rays

[20]. Although no such cases were included in this study,

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 4 4e5 050

application of this tooth-surface coating material could limit

the progression of discoloration by blocking ultra-violet rays

[21]. The degree of satisfaction with the tooth-surface coating

material among affected children and their parents was

extremely high in this study. Even in cases that involved frac-

tures, the fractures themselves did not influence the degree of

satisfaction, since the subjects were informed beforehand that

the procedure is a temporary method. Rather, because the

coating could be removed from the tooth to return it to its

normal state with almost no damage, the coating could be used

without worry, and color improvement could be tested easily.

Further, in a case of partial fracture of coating material, since it

is easily removable, it may be re-coated after removal.

In addition to the subjective evaluation of patient satis-

faction, further research on chronological changes for prog-

nosis prediction, such as quantification of color changes,

abrasion by tooth brush, and effect of the thickness of coating

material and occlusion is important in the future.

5. Conclusion

The results from the present study suggest that this tooth-

surface coating material is extremely useful for improving

color in teeth with discolored crowns in pediatric dental

practice. It is a valuable dental material that can improve es-

thetics as well as prevent cavities and strengthen teeth.

Disclosure

None of the authors has any conflicts of interest that should

be declared.

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