INTRODUCTION

The advantages of self-etch adhesives are less postoperative sensitivity, fewer operative steps, faster technique, less technique sensitivity, and clinical time savings.¹ In the self-etching systems, acid monomers are combined with water, and hydrophilic solvents can condition the dental structure while simultaneously promoting the infiltration of resinous monomers, diminishing the risk of postoperative sensibility and reducing the chances of having demineralized dentin that has not being impregnated.^1,2 Additionally, there are no concerns about the total removal of the acid and overdrying of dentin in these systems.^2,4.

Although self-etching adhesives have demonstrated good performance in dentin,^5,6 some studies have suggested that their performance in enamel is lower and that their use may lead to low bond-strength values.^7,8 Another shortcoming of self-etching adhesives is that in vitro studies have shown that they are more susceptible to microleakage in enamel because of the lower bond strength.^9,10 Self-etching adhesive systems are also subject to hydrolysis caused by the high permeability of the adhesive layer (osmosis), which generates nanoleakage at the adhesive interface.^11-13

Some clinical studies have showed good clinical performance of two-step self-etching systems.^14-18 Recently, one-step self-etching adhesive systems (1-SEAs) were introduced as the seventh generation of etching systems, which combine acid conditioning, primer, and adhesive in one bottle. Some in vitro studies showed that these systems demonstrated a similar impregnation in dentin compared with two-step self-etching systems¹⁹ or total-etch systems,²⁰ although these experiments were conducted in vitro. However, clinical studies evaluating the clinical performance of the 1-SEAs are scarce.^1,2,21-24

Because of those concerns, the objective of this study was to evaluate the clinical behavior of anterior composite restorations bonded with three 1-SEAs compared with their bonding behavior in a two-step etch-and-rinse adhesive system (2-ERA).

MATERIALS AND METHODS

The São Paulo State University Committee on Investigations Involving Human Subjects reviewed and approved the protocol and consent form used for this study.

Two clinical investigators selected 50 patients according to the following inclusion criteria: presence of four Class III, IV, and/or V carious lesions or unsatisfactory restorations; teeth with pulp vitality; a good general state of health; age between 18 and 65 years; absence of periodontal disease; appropriate oral hygiene; nonsmoker; and absence of parafunctional habits.

Before participating in the study, all patients signed an informed consent. According to the treatment rules from the São José dos Campos School of Dentistry, São Paulo State University, São Paulo, Brazil, all subjects received oral hygiene instructions before treatment.

Restoration Procedures

The restorations were performed by three master's degree students under the supervision of two professors, according to a predetermined procedure that included prophylaxis using rubber cup with pumice and water, shade selection before isolation, rubber dam isolation, and cavity preparation by removing preexisting restorations or excavating carious tissue with carbide spherical burs in a slow-speed headpiece. A bevel was made at the labial cavosurface angle of the anterior teeth using a diamond bur.²⁵ The cavities were cleaned with pumice and water in a rubber cup, rinsed, and dried.

Each subject received at least four restorations in which the adhesive systems were allocated randomly using a coin toss. The adhesive systems used in this study were one 2-ERA, Adper Single Bond 2 (3M ESPE, St Paul, MN, USA), and three 1-SEAs, Futurabond M (Voco, Cuxhaven, Germany), Optibond All-in-One (Kerr Corporation, Orange, CA, USA), and Clearfil S3 Bond (Kuraray, Tokyo, Japan). The adhesive systems were used according to manufacturer's instructions and are described in detail in Table 1.

Table 1:  Materials, pH, Compositions, and Application Mode

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After the adhesive procedures, resin restorations were completed using a Mylar matrix band and wood wedges. The teeth were restored incrementally with the microhybrid composite, Amaris (Voco). After seven days, the restorations were finished with a sequential protocol using fine grit diamond burs and polishing discs (Soflex, 3M ESPE) under water cooling (Figures 1A,B and 2A,B).

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Clinical Evaluation

Evaluations were performed by the operator and at regular time intervals by other evaluators with a kappa agreement of 80%. The restorations were evaluated at baseline, 12 months, and 24 months with regard to (1) restoration retention, (2) enamel and dentin marginal integrity, (3) marginal discoloration, (4) caries occurrence, (5) postoperative sensitivity, and (6) preservation of tooth vitality. The restorations were evaluated according to the criteria introduced by Vanherle and others,²⁶ as shown in Table 2.

Table 2:  Criteria for Assessing Composite Restorations

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RESULTS

Baseline Data

Fifty subjects were enrolled. The mean age of the patients was 38.5 (±11.1) years. Two hundred composite restorations were placed, 50 with FuturaBond M, 50 with Optibond All-in-One, 50 with Clearfil S3 Bond, and 50 with Single Bond 2. The distribution of the adhesive systems according to Black's classification is listed in Table 3.

Table 3:  Distribution of the Adhesive Systems According to Black's Classification

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Recall Rate

At the one-year and two-year recalls, the recall rates were 86.0% (43 patients with 172 restorations) and 80.0% (41 patients with 162 restorations), respectively (Table 4). Table 5 summarizes the number of restorations evaluated at each recall period. A cumulative number of two restorations failed during the two years; two restorations with Single Bond 2 were lost.

Table 4:  Number of Restorations Evaluated After Each Recall

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Table 5:  Summary of Restorations Evaluated

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DISCUSSION

The 1-SEAs were developed following the recent trend of simplifying the clinical steps and saving operator time. Yet it is important to determine the longevity of these restorations and provide evidence of the safety and efficacy of the new 1-SEAs. Therefore, to that end, the current clinical study evaluated the short-term clinical effectiveness of three of the newest generation of 1-SEAs and compared them to a two-step etch-and-rinse adhesive (2-ERA).

The clinical efficacy of the systems tested was determined by evaluating the restorative retention, marginal integrity, marginal discoloration, caries occurrence, and tooth vitality.^23,26 In most of the restorations evaluated, few changes were noted from baseline to the two-year evaluation visit. No statistically significant differences were observed between the 2-ERA and the 1-SEAs in terms of retention or any of the other evaluation criteria.

The American Dental Association requires a retention rate of at least 90% of the restorations placed after 18 months to obtain full acceptance.²⁷ Because of the retention loss of two Class IV restorations belonging to the Single Bond 2, the overall clinical success rate was 95.0% for Single Bond 2 after two years. Therefore, all systems evaluated in this study demonstrated good clinical performance and full acceptance. It is possible that the Single Bond 2 restorations failed because large resin composite restorations have a higher failure rate.²⁸ Additionally, Moura and others²⁹ observed that Class IV restorations had a high prevalence of failures in a three-year clinical performance of composites. With regards to bonding performance and longevity, in vitro investigations found that 1-SEAs presented similar tensile bond strengths to dentin when compared with two-step self-etching systems¹⁹ or total-etch systems.²⁰

Corroborating the current results, Zhou and others²⁴ and Brackett and others,²¹ at one-year and two-year recalls, respectively, evaluated the clinical performance of two-bottle and one-bottle self-etching adhesives and observed no statistically significant differences between the systems. Van Landuyt and others²³ and Ermis and others,²² after one-year and two-year clinical evaluations, respectively, found that a one-step self-etch adhesive and a three-step etch-and-rinse adhesive were equally clinically successful. Fron and others¹ observed that the effectiveness of a one-step self-etch adhesive was very good after two years of clinical service.

Slightly more restorations exhibited marginal discoloration at the two-year recall when bonded with Single Bond 2 (10%) than when bonded with Optibond All-in-One (7.5%) and Futurabond M (2.5%), but no statistically significant differences were observed. The differences among all of the adhesive systems were not statistically significant. All restorations that exhibited marginal discoloration were classified with a bravo score, “the visual evidence of marginal discoloration between tooth structure and restoration, but the discoloration does not penetrate in the interface in pulp direction” (Table 2). Rates were high for this short period of time. These results could be due to the fact that the patients enrolled have great difficulty in finding access to dental services because they have low incomes and probably have worse oral health than the general population.

Marginal discoloration usually results from defects present between the tooth-colored restoration and the cavity margins and walls, and the etiology can be inadequate restoration placement, finishing procedures, and unsatisfactory bonding.³⁰ According to some studies, 1-SEAs are more susceptible to microleakage in enamel tissue because of their lower bond strength.^9,10 However, the current results showed good clinical performance of 1-SEAs compared with a 2-ERA, as also observed by Van Landuyt and others²³ and Ermis and others.²²

At the one-year recall, alpha scores for marginal integrity were 97.0% for restorations bonded with Single Bond 2. At the two-year recall, alpha scores for marginal integrity (marginal adaptation) were 97.5% for restorations bonded with Single Bond 2, Clearfil S3 Bond, and Optibond All-in-One. Statistical differences between the adhesive systems were not significant. These results demonstrate that the tested adhesive systems showed good marginal integrity during the evaluated period, which is desirable, because restorations with deteriorating margins are more likely to fail than restorations with ideal margins.³¹ However, in vitro studies have shown that 1-SEAs are subject to hydrolysis, which is caused by the high water content of the dentin surface, which can generate a phenomenon called water treeing.³² Water trees are water canals at the adhesive interface created by the highly osmolarity of the adhesive solution generating nanoleakage.^11-13 In vivo studies are in agreement with the current results, showing good results of 1-SEAs for marginal integrity.^1,21,22,24

With regards to postoperative sensitivity, one restoration bonded with Clearfil S3 Bond, one with Single Bond 2. and one with Optibond All-in-One showed postoperative sensitivity at the one-year recall. At the two-year recall, one restoration bonded with Clearfil S3 Bond and one with Optibond All-in-One showed sensitivity. One of the advantages of the self-etching adhesives is a reduction of postoperative sensitivity, as they are less technique sensitive, which reduces possible failures caused by imperfections in the adhesion that result from overetching or drying of the dentin.^1,22,33 However, the current results showed no significant differences in postoperative sensitivity between the systems, corroborating the findings of Van Landuyt and others²³ and Ermis and others.²² According to Van Landuyt and others,²³ the reduction of postoperative sensitivity can be explained by the protective effect of the restoration combined with the passage of time.

The excellent short-term clinical performance of 1-SEAs in the present study can be attributable to (1) the experience of the operators in performing adhesive dentistry; (2) the presence of a bevel at the labial cavosurface angle, which can improve retention and reduce marginal discoloration of restorations;^3,34 and (3) the low pH of the systems and functional monomers in their composition (ie, manufacturers have developed products with lower pH, which increases their acidity, and consequently, they produce an acceptable enamel etching pattern.)⁶

In conclusion, after a two-year recall, the 1-SEAs Clearfil S3 Bond, Futurabond M, and Optibond All-in-One performed similarly to a 2-ERA (Single Bond 2) in terms of restorative retention, marginal integrity, marginal discoloration, caries occurrence, and tooth vitality. However, further studies are necessary to evaluate the long-term clinical performance of these systems.

CONCLUSIONS

There were no statistically significant differences between the 2-ERA and the 1-SEAs with regards to the evaluated parameters. The 1-SEAs showed good clinical performance at the end of 24 months.