Advance Online Publication

ODEP Vol. 1, No. 1

Original Article

Clinical Assessment of Resin-coating Technique for Dentin
after Cavity Preparation
TSURUTA Hanemi, KUSAKABE Shusuke,
BURROW Michael F＊ and NIKAIDO Toru
Department of Operative Dentistry, Division of Oral Functional Science and Rehabilitation,
Asahi University School of Dentistry＊

Restorative Dental Sciences, Faculty of Dentistry, University of Hong Kong

Abstract
Purpose: Many studies have been conducted on the resin-coating technique for indirect restorations, andits efficacy has been reported. This study investigated the clinical course of cases with the resin-coating
technique for dentin after inlay cavity preparation and examined the efficacy of the technique clinically.
Methods: Twenty cases in 18 patients visiting one of three dental clinics that were collaborating with thisinvestigation between September 2014 and October 2019 were evaluated. The patients were treated using
the resin-coating technique by applying a thin coating material（Hybrid Coat Ⅱ, HC Ⅱ）after inlay cavity
preparation. Patient dental and medical records as well as clinical information that included tooth site, procedures, materials used, and clinical symptoms before, during, and after the procedures and at the time ofrecall were obtained using set clinical evaluation criteria.
Results: Fifty percent of the restorations were performed in premolars and 50％ in molars. Local anesthesia was used in all cases except one. Resin coating was performed using HC Ⅱ alone in 40％ of cases and HC
Ⅱ combined with a flowable resin in 60％ of cases. After inlay placement, 95％ of the cases（19 cases）had afavorable outcome. Of the 10 cases（50％）where the patient experienced pain on cold water stimulation
before treatment, nine cases had a favorable outcome; however, in one case pain on drinking cold water persisted and the patient then presented with pulpal symptoms, thereby requiring a pulpectomy.
Conclusion: The results demonstrate the clinical efficacy of the resin-coating technique using HC Ⅱ on
inlay cavity preparations.
Key words: resin-coating technique, Hybrid Coat Ⅱ, inlay cavity preparation

Corresponding author: Dr. KUSAKABE, Department of Operative Dentistry, Division of Oral Functional Science and Rehabilitation, Asahi University School of Dentistry, 1851, Hozumi, Mizuho, Gifu 501 0296, Japan.
TEL & FAX: ＋81 58 329 1442, E-mail: kusakabe@dent.asahi-u.ac.jp
Received for Publication: May 15, 2021/Accepted for Publication: August 11, 2021
DOI: 10.11471/odep.2021-005

Advance Online Publication

ODEP Vol. 1, No. 1

resin coating is a reliable treatment 21）. However, noclinical study has evaluated the resin coating for cavity

Introduction

preparations. Therefore, this retrospective study invesIn recent years, the use of direct composite resto-

tigated the clinical performance of inlay restorations

rations in molars has improved with the advancement

placed using a resin-coating technique in collaborationof adhesive materials and technologies. Currently, awith three dentists who routinely employ the res-composite restoration can be promptly performed byin-coating technique for vital teeth, and assessed the

preparing the cavity such that only the caries-infectedvalidity and efficacy of the procedure.

dentin is removed and caries-affected dentin is preserved, thereby protecting the remaining dentin andMaterials and Methods

pulp. However, for extensive carious lesions in molars
where the restoration is subjected to greater occlusal

1 ．Materials for resin coating

loading and the restorations may need to protect cusps,

The composition of Hybrid Coat Ⅱ（HC Ⅱ Sun Med-an indirect restoration such as an inlay or onlay can beical, Moriyama, Japan）, a resin coating material used inselected. Generally, the degree of dentin exposure after

this study, is shown in Table 1. HC Ⅱ is the next ver-preparation for an indirect restoration is much greater.

sion of HC（Sun Medical）, which has been available in

The resin-coating technique was introduced based on

the market since January 2010. HC Ⅱ was developed

the idea of direct composite resin restorations and theon the concept of a one-step bonding agent, which con-application of a reliable adhesive system for indirect

sists of a one-bottle bonding agent and a dedicatedrestorations. The resin-coating technique is used tosponge22）. When HC Ⅱ is used, a dedicated sponge con-cover the dentinal surface exposed after cavity prepa-

taining adhesion promoters is used to apply the bonding

ration for an indirect restoration such as an inlay ormaterial to the tooth surface. In Japan, HC Ⅱ has beencrown with an adhesive system for protecting thecovered under the Japanese national health insurance

exposed dentin and pulp1 4）. Specifically, coating thesystem since December 2019 as a material for resin

exposed dentinal surface immediately before impres-coating of prepared surfaces of vital abutment teeth.

sion-taking with an adhesive system aims to form a thin

2 ．Methods for investigation

film on the dentinal surface which helps protect theThis study was approved by the Ethics Committee ofpulp and improves adhesion of the resin cement to the

Asahi University School of Dentistry（approval number

dentin, thereby improving the marginal seal1）. By using

32007）. The study was conducted in collaboration withthe resin-coating technique, few adhesive failures of res-three dentists in private practice who frequently per-torations at the dentinal interface occur due to theform vital tooth inlay restorations using the resin-coat-

improvement in the adhesion of the resin cement to theing technique. The outline of the clinical study and its

dentin. This also leads to a decrease in the frequency of

methods were explained to the dentists and their con-marginal and bacterial leakage which has been

sent to join the study was obtained.

r e p o r t e d 2 , 5 1 3）. C o n s e r v a t i o n o f t o o t h s t r u c t u r e ,The study included 18 patients（ten males, eightdecreased patient discomfort, and a favorable clinicalfemales; mean age, 51.4 years old）visiting one of thecourse of indirect restorations have also been

three dentists between September 2014 and October

reported

1,2,14 19）

2019. Patient records were identified for those who.

In Japan, the resin-coating technique for preparing

received an inlay for a vital tooth. The age of thevital abutment teeth has been covered under the Japa-

patients is shown in Table 2. Nineteen cases in 18

nese national health insurance system since December

patients who could be followed up after the restoration

2019 and its use is expected to become more common.

and who also consented to join the investigation wereOn the other hand, the clinical application of the res-investigated.

20）

in-coating technique is still being improved . Labora-

Immediately after the cavity preparation, the pre-tory studies have demonstrated its superior perfor-

pared tooth was resin-coated using HC Ⅱ followed bymance; a clinical study on the resin-coating techniqueimpression-taking. At the next visit, an inlay was placedfor crown preparation of vital teeth reported that thewith a resin cement.

Table 1
Brand
Hybrid Coat Ⅱ（HC Ⅱ）

Composition and usage of resin-coating material

Manufacturer

Composition

Sun Medical（Moriyama, Japan）

Procedure

liquid：acetone, MMA, 4-META others, water ①Liquid stirring and mixing with acoat sponge/micro-brush sponge
Powder in coat sponge/micro-brush sponge： ②After applying the mixed solution
aromatic amine, aromatic sulfinate
for 10 s, air-blowing for 5 s③Light irradiation for 5 s

MMA：methyl methacrylate, 4-META：4-methacryloxyethyl trimellitate anhydride

Table 2Sex

Category
Number of cases（Percentage）

Baseline information of the participants

Male

Age（yrs）
Female10（55.6） 8（44.4）

Treatment tooth

20 29

30 39

40 49

50 59

60 69

1（5.6）

3（16.7）4（22.2）3（16.7）7（38.9） 10（50.0） 10（50.0）

Total 18

We used a clinical investigation proforma to obtainbasic information about each patient（age, sex）, theAverage 51.4

Premolar

Molar

Total 20

11 days and 289 days, respectively. The total period of
the investigation was 10 months on average.

intervention site and investigated procedures such as

Before commencing the cavity preparation, local

whether local anesthesia had been administered, if pulp

anesthesia was used in all cases except one. Also, local

protection had been provided, methods for resin coat-anesthesia was used for inlay placement in 10％ of theing, the resin cement used for adhesion, and any clinicalcases.

symptoms before, during, and after the restorative pro-

The resin-coating technique was performed on eachcedure and at the time of latest recall based on thecavity using a single application of HC Ⅱ in eight cases

dental records. Personal information including patient（40％）
and a combination of HC Ⅱ with a flowable resinname and address was excluded from the data forms tocomposite in 12 cases（60％）. No case required direct
pulp capping during the cavity preparation. The resto-

maintain anonymity.
3 ．Data collection and analysis

rations comprised inlays covered under insurance in 14

After the investigation was completed, the evaluation

cases（70％）（metal inlay in 12 cases and a resin com-forms were collected from the dentists. When there

posite inlay in one case）and self-financed inlays in six

was any doubt about the information provided in thecases（30％）（hybrid resin inlay in one case, gold alloy

form, the dentist who completed it was asked directly

inlay in two cases, ceramic inlay in two cases, and a zir-for confirmation and clarification. Thereafter, all data

conia inlay in one case）.

were collated and analyzed.

In 19 cases（95％）, a dual-cure resin cement was used
for the cementation, SA Luting Plus（Kuraray Noritake

Results

Dental, Tokyo, Japan）, G-Luting（GC, Tokyo, Japan）, andother dual-cure resin cements described as listed in the

The results of the investigation are shown in Table 3.

clinical data forms. In one case（5％）, Super-Bond C &In this study, the restorations were performed on pre-B（Sun Medical）, a methyl methacrylate-based resin

molars in 10 cases（50％）（five cases on maxillary pre-cement, was used.

molars and five cases on mandibular premolars）andAfter inlay placement, the clinical outcome wasmolars in 10 cases（50％）（three cases on maxillary

determined to be favorable in 19 cases（95.0％）.

molars and seven cases on mandibular molars）. The

Although discomfort such as pain on drinking cold

average period between cavity preparation and inlay

water was observed before treatment in nine cases

placement and between inlay placement and recall was（45％）, the outcome was determined to be favorable

Advance Online Publication
Table 3

Evaluation outcomes collected from the protocols
Number of cases

Content of survey
Local anesthesia

ODEP Vol. 1, No. 1（Percentage of cases）

Cavity preparation

Yes
No
Yes
No

Inlay placement19（95.0）1（5.0）
2（10.0）18（90.0）

Resin-coating procedure

Single application of HC Ⅱ
Combination of HC Ⅱ with a flowable resin8（40.0）12（60.0）

Resin cement

MMA-based resin cement
Dual-cure resin cement1（5.0）
19（95.0）

Restoration category under the national insurance system

Approved
Not approved

14（70.0）6（30.0）Adverse event after placement of the restorationNo
Yes

19（95.0）1（5.0）

after treatment in eight of the nine cases. Of the cases

placement of the restoration in 95％ of cases was deter-where discomfort was experienced before treatment,

mined, which indicated that the resin-coating techniquepain on drinking cold water persisted after treatment

was effective after cavity preparation in vital teeth.

and even at the time of recall occurred in only one case,

The clinical outcomes were favorable in 8/9 cases thatwhich subsequently required a pulpectomy 155 days

originally presented with pain upon cold water stimula-

after the commencement of treatment（Table 3）.

tion before the treatment. The resin-coating technique
was able to protect the prepared dentin surface andisolated it from pain-causing stimuli. However, one case

Discussion

still experienced pain on cold water exposure at the
The results of this study showed that as cavity

time of recall and finally presented with pulpal symp-

preparation for vital teeth was accompanied by the cut-toms, thereby requiring a pulpectomy. Currently, it isting of intact dentin, local anesthesia needed to be usedchallenging to accurately diagnose the pulp response offor cavity preparation in almost all cases. Some studies

a tooth where the patient experiences discomfort. In

have indicated that damage to the pulp is associatedcases requiring a pulpectomy, it is difficult to diagnosewith the cutting of vital dentin when using an air-tur-

the pulpal condition for an inlay restoration. Under the

23,24）. If protecting the vital tooth struc-current circumstances, in cases with discomfort due totures is prioritized based on the idea of minimally inva-

pulpal sensitivity, the restoration should be performed

sive dentistry, a direct composite restoration should beafter recovery from the discomfort. In cases requiring a

selected for caries treatment. However, when an inlay

restoration, it is crucial to carefully perform the restor-

restoration is inevitably selected as the treatment of

ative procedures after providing the patient with an

choice, the tooth preparation should be carefully per-adequate explanation of the benefits and risks of theformed while using air-water spray from the handpiece

procedure and then obtaining consent.

bine hand piece

and a very light touch preparation to minimize damage

The resin-coating technique may improve the bond-to the pulp. On the other hand, local anesthesia was noting performance of resin cement to dentin for indirectused in one case. The reason was not unclear, but cut-

restorations and also enhance the marginal sealting intact dentin might have been minimal in this case.

between the restoration and the cavity wall26 28）. This

According to Fusayamaʼs concept25）, local anesthesia isevaluation used dual cure resin cements for luting res-not necessary if cutting is limited only for

torations in most cases. Such cements are routinely

fectedandcaries-affected

caries-in-

dentin.

A favorable outcome free of any discomfort afterused for the luting of tooth-colored restorations, such as
resin composite and ceramic inlay/onlay restorations,because the light-curing of the cement effectively
improves the bond strength of the tooth-colored resto-

Conclusion

rations to the underlying tooth structure. On the other
hand, self-cure resin cements, such as Super-Bond C &B, should ideally be used for metal inlay restorations. It

1．Local anesthesia was used for cavity preparation
in a vital tooth in almost all cases.

was reported, however, that the immediate dentin bond

2．The outcome was favorable after placing the res-strength of Super-Bond C&B was significantly lower

toration with the resin-coating technique using HC Ⅱ

than that of dual-cure resin cements, but after 24 h aalone and HC Ⅱ combined with a flowable resin in 95％

29）high bond strength could be achieved . Further inves-of cases.

tigation of the clinical outcomes of restorations

3．Of the nine patients who experienced discomfort

cemented with various types of resin cement, including

before the procedure, the clinical outcome was favor-

cement removal after restoration placement, is requiredable in eight cases（89％）; however, discomfort per-to expand the current evidence base30,31）.

sisted in one case, which required a pulpectomy（11％）.

Resin coating was performed by using HC Ⅱ alone in

4．These results revealed that the resin-coating

37％ of cases and HC Ⅱ combined with a flowable resin

technique using HC Ⅱ was effective in protecting thein 63％ of cases. As the coating with HC Ⅱ forms a

dentin and pulp after cavity preparation.

thin coating of approximately 5 μm thickness per application, HC Ⅱ does not alter the overall contour of the

Conflict of Interest

prepared surface18,32,33）. Meanwhile, when HC Ⅱ is com-

The authors declare that there are no potential conflictsof interest with regard to the publication of this article.

bined with a flowable resin, any undercuts within thecavity preparation can be easily blocked out by placement of the flowable resin. In this study, interviews
after collecting the evaluation forms confirmed that thecavity morphology had been modified by the additionaluse of a flowable resin. In addition, it has been reported
that HC Ⅱ combined with a flowable resin improved
the adhesion of a resin cement to dentin4,10,11,34,35）. Resincoating using HC Ⅱ alone is suitable for cases requiringhigh-precision preparation methods, such as crown
preparation of abutment teeth for a fixed prosthesis. On
the other hand, resin coating using HC Ⅱ combinedwith a flowable resin is suitable for cases requiringsmooth and stress concentration-free cavity forms suchas resin or ceramic inlays.
The resin-coating technique has been covered by theJapanese national health insurance system for the
preparation of vital teeth since 2019, however, it does
not include inlay and onlay cavities. The results of thisstudy revealed the efficacy of the resin-coating technique on inlays and onlays. It is strongly hoped that theresin-coating technique will be covered within theinsurance system for inlay and onlay cavities in the
future. This study verified the short-term clinical outcomes of the resin-coating technique; however, its longterm clinical outcomes need to be investigated.

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