Thirteen-year randomized controlled clinical trial of a two-step self-etch adhesive in non-carious cervical lesions

Highlights

  • The mild 2-step self-etch adhesive Clearfil SE Bond showed good clinical performance in non-carious cervical lesions after 13 years.

  • Selective acid-etching of the enamel cavity margins prior to application of a mild 2-step self-etch adhesive has only a minor positive effect on marginal integrity and absence of marginal discoloration.

  • The presence of caries is rarely seen in direct composite restorations placed in non-carious cervical lesions after 13 years.

Abstract

Objective

The objective of this randomized controlled clinical trial was to evaluate the 13-year clinical performance of a mild two-step self-etch adhesive in non-carious cervical lesions with and without prior selective phosphoric acid-etching of the enamel cavity margins.

Methods

A total of 100 non-carious cervical lesions in 29 patients were restored with Clearfil AP-X (Kuraray Noritake). The composite restorations were bonded following two different approaches: (1) application of Clearfil SE Bond (Kuraray Noritake) following a self-etch approach (CSE-NE); (2) selective phosphoric acid-etching of enamel cavity margins before application of Clearfil SE Bond (CSE-E). The restorations were evaluated after 6 months, 1, 2, 3, 5, 8 and 13 years of clinical service regarding retention, marginal integrity and discoloration, caries occurrence, preservation of tooth vitality and post-operative sensitivity.

Results

The patient recall rate at 13 years was 62%. Six restorations, 4 of the CSE-NE group and 2 of the CSE-E group, were clinically unacceptable due to loss of retention (1 CSE-NE, 1 CSE-E), a severe marginal defect (2 CSE-NE, 1 CSE-E) and caries occurrence in combination with a severe marginal defect (1 CSE-NE) leading to a clinical success rate of 86% (CSE-NE) and 93% (CSE-E). Ageing of the restorations was characterized by a further increase in the percentage of restorations with a clinically acceptable small marginal defect (CSE-NE: 87%; CSE-E: 83%) and/or superficial marginal discoloration (CSE-NE: 53%; CSE-E: 56%). The presence of small marginal defects (CSE-NE: 86%; CSE-E: 68%) and superficial marginal discoloration (CSE-NE: 41%; CSE-E: 20%) at the incisal enamel side was more frequently noticed in the CSE-NE group than in the CSE-E group. The difference, however, was not statistically significant (McNemar, p > 0.05).

Significance

After 13 years, the clinical effectiveness of Clearfil SE Bond in non-carious Class-V lesions remained excellent, with selective acid-etching of the enamel cavity margins only having some minor positive effect on marginal integrity and absence of marginal discoloration.

Introduction

Although the longevity of direct composite restorations was considered as too short (3–5 years) in the previous decade , recently published randomized controlled clinical trials show a favorable clinical performance of these restorations after long-term clinical functioning . An important factor contributing to increased longevity is improved bonding efficiency of the contemporary adhesives. Adhesives used in combination with a direct composite material can be divided into 3-step and 2-step etch-and-rinse adhesives (3E&Ra, 2E&Ra), and 2-step and 1-step self-etch adhesives (2SEa, 1SEa) . The group of self-etch adhesives can be further subdivided depending on the pH of the self-etching primer. Mild/intermediate SEa (SEa_m/i) contain a self-etching primer with pH ≥ 1.5, by which the hybrid layer is not completely demineralized. In addition, they contain a functional monomer that can chemically bond to the hydroxyapatite (Hap) left in the hybrid layer. Strong SEa (SEa_s) have a self-etching primer with pH < 1.5. These adhesives do not have a chemical bonding potential .

The best lesions to test the clinical effectiveness of adhesives are non-carious cervical lesions (NCCLs). In these lesions the restoration will be bonded to both enamel and dentin. The largest part of the tooth surface to bond to consists of dentin, while at the incisal side the restoration margin ends in enamel. In addition, these restorations do not provide any or only minimal macroretention to test adhesive bonding effectiveness . A recently published systematic literature review of NCCL clinical trials evaluating the clinical effectiveness of contemporary adhesives reports that the lowest annual failure rate (AFR, expressed as loss of retention in function of time) for adhesives combined with a restorative material was recorded in the 2SEa_m/i (2.5 ± 1.5) subcategory . The most frequently tested (12 times) adhesive in this subcategory, Clearfil SE Bond (Kuraray Noritake, Tokyo, Japan), showed the lowest AFR (2.2 ± 1.2). Its high quality bonding performance in vivo can be explained by the presence of the functional monomer 10-MDP, which creates a very stable chemical bond with the Hap left in the hybrid layer . In addition, it forms a regular nano-layered structure at the Hap surface . The strong hydrophobicity of the nano-layered structure helps to protect the hybrid layer against hydrolytic bond degradation processes . This results in the well-documented favorable in-vitro durability of dentin bonds produced by 10-MDP based adhesives .

The NCCL clinical trials evaluating Clearfil SE Bond in the systematic review of Peumans et al. only included 2 long-term clinical trials (evaluation period longer than 5 years): (1) an 8-year evaluation of van Dijken , (2) another 8-year clinical trial was carried out by our research group recording a 97% retention and success rate. Given that adhesive systems show such a high success rate after 8 years, a longer-term evaluation is interesting to gather more precise information regarding bond longevity in these NCCLs.

Therefore, the aim of this clinical trial was to evaluate the 13-year clinical performance of the mild 2SEa, Clearfil SE Bond in NCCLs. As with the 8-year recall, the influence of prior selective enamel etching of cavity margins on the restorations’ clinical performance was assessed.

Materials and methods

The clinical effectiveness of Clearfil SE (Kuraray Noritake), was evaluated when applied strictly following a self-etch approach on both enamel and dentin (according to manufacturer’s instructions; abbreviated as ‘CSE-NE’) and compared to the application of the same adhesive following the same application protocol, but after the enamel cavity margins were selectively acid-etched with 40% phosphoric acid (abbreviated as ‘CSE-E’). Clearfil AP-X (Kuraray Noritake) was used as restorative composite ( Table 1 ).

Table 1
Adhesive composition and application procedure.
Adhesive Components and composition Application procedure
Clearfil SE (Kuraray Noritake, Tokyo, Japan) Primer : 10-MDP, HEMA, hydrophilic dimethacrylate, CQ, N , N -diethanol p -toludine, water
Adhesive: 10-MDP, Bis-GMA, HEMA, hydrophilic dimethacrylate, CQ, N , N -diethanol p -toludine, silanized colloidal silica
Apply primer for 20 s; gently air-blow
Apply adhesive and light-cure for 10 s
K-etchant (Kuraray Noritake) 40% Phosphoric acid, thickener Apply etchant selectively on enamel and leave for 15 s; thoroughly rinse and gently air dry (only for C-SE etch)
Bis-GMA, bisphenol-glycidyl methacrylate; CQ, di-camphoroquinone; HEMA, hydroxyethyl methacrylate; 10-MDP, 10-methacryloyloxydecyl dihydrogen phosphate

Twenty-nine non-hospitalized patients were enrolled in the study (mean age at baseline: 58 years, 11 male and 18 female patients). They were recruited from the University Hospital Leuven, and were in need of cervical restorations. Patients with compromised medical history, severe or chronic periodontitis, extreme caries sensitivity and heavy bruxism were excluded from the study. Prior to participating in the study all patients signed a written consent. The clinical trial protocol was approved by the Commission for Medical Ethics of the Catholic University of Leuven. Essentially, the teeth were randomly assigned for restoration either following the CSE-NE or CSE-E application procedure using randomization tables. 50 restorations per group were placed in cervical non-carious erosion/abrasion/abfraction lesions of incisives, canines and premolars. Only maximum two restorations per group were placed in one patient so that per patient restorations prepared following the two different protocols were mutually compared.

The restorations were placed from September 2000 to January 2001 by two specially instructed and experienced dentists from the university dental school. All restorative procedures were done under rubberdam isolation. Regarding tooth preparation, the dentin walls of the lesions were superficially roughened with a coarse diamond and a short enamel bevel (1–2 mm) was made. The restorative procedure is described in detail in the 2-year report .

After 13 years, the clinical performance of the restorations was recorded in terms of (1) restoration retention, (2) enamel and dentin marginal integrity, (3) marginal discoloration, (4) caries occurrence, (5) post-operative sensitivity and (6) preservation of tooth vitality following a modified USPHS index system . The first four parameters were considered the key parameters for overall clinical success. Retention loss, severe marginal defects and/or discoloration that needed intervention (repair or replacement) and occurrence of caries along the restoration margins were considered as clinical failures.

Marginal integrity was evaluated using a sharp probe and mirror. Post-operative sensitivity was measured by blowing a stream of compressed air at a distance of 2–3 cm from the cervical restoration for 3 s while shielding the adjacent teeth with fingers and by moving the probe over the restored tooth surface. A persistent reaction after air-blowing or probing the restored tooth surface was recorded as post-operative sensitivity. Clinical photographs were taken at this recall. Statistical analysis compared the ratings of retention, marginal integrity, marginal discoloration and overall clinical success on a pair-wise basis between the experimental and the control group using the McNemar test ( p < 0.05).

Materials and methods

The clinical effectiveness of Clearfil SE (Kuraray Noritake), was evaluated when applied strictly following a self-etch approach on both enamel and dentin (according to manufacturer’s instructions; abbreviated as ‘CSE-NE’) and compared to the application of the same adhesive following the same application protocol, but after the enamel cavity margins were selectively acid-etched with 40% phosphoric acid (abbreviated as ‘CSE-E’). Clearfil AP-X (Kuraray Noritake) was used as restorative composite ( Table 1 ).

Table 1
Adhesive composition and application procedure.
Adhesive Components and composition Application procedure
Clearfil SE (Kuraray Noritake, Tokyo, Japan) Primer : 10-MDP, HEMA, hydrophilic dimethacrylate, CQ, N , N -diethanol p -toludine, water
Adhesive: 10-MDP, Bis-GMA, HEMA, hydrophilic dimethacrylate, CQ, N , N -diethanol p -toludine, silanized colloidal silica
Apply primer for 20 s; gently air-blow
Apply adhesive and light-cure for 10 s
K-etchant (Kuraray Noritake) 40% Phosphoric acid, thickener Apply etchant selectively on enamel and leave for 15 s; thoroughly rinse and gently air dry (only for C-SE etch)
Bis-GMA, bisphenol-glycidyl methacrylate; CQ, di-camphoroquinone; HEMA, hydroxyethyl methacrylate; 10-MDP, 10-methacryloyloxydecyl dihydrogen phosphate

Twenty-nine non-hospitalized patients were enrolled in the study (mean age at baseline: 58 years, 11 male and 18 female patients). They were recruited from the University Hospital Leuven, and were in need of cervical restorations. Patients with compromised medical history, severe or chronic periodontitis, extreme caries sensitivity and heavy bruxism were excluded from the study. Prior to participating in the study all patients signed a written consent. The clinical trial protocol was approved by the Commission for Medical Ethics of the Catholic University of Leuven. Essentially, the teeth were randomly assigned for restoration either following the CSE-NE or CSE-E application procedure using randomization tables. 50 restorations per group were placed in cervical non-carious erosion/abrasion/abfraction lesions of incisives, canines and premolars. Only maximum two restorations per group were placed in one patient so that per patient restorations prepared following the two different protocols were mutually compared.

The restorations were placed from September 2000 to January 2001 by two specially instructed and experienced dentists from the university dental school. All restorative procedures were done under rubberdam isolation. Regarding tooth preparation, the dentin walls of the lesions were superficially roughened with a coarse diamond and a short enamel bevel (1–2 mm) was made. The restorative procedure is described in detail in the 2-year report .

After 13 years, the clinical performance of the restorations was recorded in terms of (1) restoration retention, (2) enamel and dentin marginal integrity, (3) marginal discoloration, (4) caries occurrence, (5) post-operative sensitivity and (6) preservation of tooth vitality following a modified USPHS index system . The first four parameters were considered the key parameters for overall clinical success. Retention loss, severe marginal defects and/or discoloration that needed intervention (repair or replacement) and occurrence of caries along the restoration margins were considered as clinical failures.

Marginal integrity was evaluated using a sharp probe and mirror. Post-operative sensitivity was measured by blowing a stream of compressed air at a distance of 2–3 cm from the cervical restoration for 3 s while shielding the adjacent teeth with fingers and by moving the probe over the restored tooth surface. A persistent reaction after air-blowing or probing the restored tooth surface was recorded as post-operative sensitivity. Clinical photographs were taken at this recall. Statistical analysis compared the ratings of retention, marginal integrity, marginal discoloration and overall clinical success on a pair-wise basis between the experimental and the control group using the McNemar test ( p < 0.05).

Results

The 1, 5, 8 and 13-year clinical data for the various parameters evaluated are summarized in Table 2 .

Table 2
Evaluation results in percentage at 1, 5, 8 and 13 years.
1 Year 5 Years 8 Years 13 Years
CSE-E CSE-NE CSE-E CSE-NE CSE-E CSE-NE CSE-E CSE-NE
Recall rate (restoration) 96 96 84 84 76 76 62 62
Retention rate 100 100 100 98 97 97 96 96
Absence of marginal defects 70 72 52 17 16 8 16 4
Enamel marginal defect 9 13 34 64 65 86 72 86
Small enamel marginal defect 9 13 34 64 65 86 68 86
Severe enamel marginal defect 0 0 0 0 0 0 4 0
Dentin marginal defect 22 15 29 41 54 62 77 65
Small dentin marginal defect 22 15 29 41 54 62 77 54
Severe dentin marginal defect 0 0 0 0 0 0 0 11
Absence of marginal discoloration 96 100 83 68 72 56 47 41
Superficial localized marginal discoloration 4 0 17 32 28 44 53 55
Deep generalized restoration discoloration 0 0 0 0 0 0 0 4
Absence of post-operative sensitivity 98 98 100 100 100 100 100 100
Absence of caries occurrence 100 100 100 100 100 100 100 96
Overall clinical success rate 100 100 100 100 97 97 93 86
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Nov 23, 2017 | Posted by in Dental Materials | Comments Off on Thirteen-year randomized controlled clinical trial of a two-step self-etch adhesive in non-carious cervical lesions
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