Five-year clinical evaluation of a universal adhesive: A randomized double-blind trial


  • This is the first long-term clinical study evaluating the first commercial universal adhesive.

  • The etch-and-rinse (moist or dry) strategy showed better clinical behavior than the self-etch strategy.

  • For practicing dentists, it is recommended to etch enamel when using a universal adhesive.

  • FDI and USPHS criteria showed similar results after 5 years.



To evaluate the five-year clinical performance of Scotchbond Universal Adhesive (SU; 3M Oral Care, St. Paul, MN, USA) in non-carious cervical lesions (NCCLs) using two evaluation criteria.


Thirty-nine patients participated in this study. Two hundred restorations were assigned to four groups: SU-ERm: etch-and-rinse + moist dentin; SU-ERd: etch-and-rinse + dry dentin; SU-Set: selective enamel etching; and SU-SE: self-etch. A nanofilled composite resin was placed incrementally. The restorations were evaluated at baseline and after 5 years using both the World Dental Federation (FDI) and the United States Public Health Service (USPHS) criteria. The survival rates (retention/fractures) were calculated with the Kaplan-Meier and the log-rank test. For the secondary outcomes, Friedman repeated measures analysis of variance by rank was applied ( α = 0.05).


After 5 years the recall rate was 86%. The retention/fracture rates were 93% for Er m and ER d, 88.4% for SE et and 81.4% for SE. A significant difference was observed for SE vs. ER d and SE vs. ER m (p = 0.01). Also, marginal discoloration and adaptation showed significant differences with ER m and ERd resulting in fewer marginal discrepancies than SE (p < 0.05).


After 5 years, the clinical behavior of the universal adhesive in the etch-and-rinse strategy was better when compared to the self-etch strategy. The use of selective enamel etching is highly recommended for the self-etch strategy. The FDI and USPHS evaluation criteria showed similar results after 5 years.


As the life expectancy increases, the population retains their teeth longer. All forms of tooth wear have become an important issue in clinical dentistry. In contrast to carious lesions, non-carious cervical lesions (NCCLs) correspond to a loss of hard dental tissues, usually involving enamel, dentin and cementum, on the buccal surface of teeth in the vicinity of the CEJ.

The multi-factorial etiology of NCCLs has been well established in the literature [ ]. The prevalence of NCCLs has been reported to vary from 2% to 90%, with higher prevalence in older patients [ ]. More recently, a systematic review found a higher weighed prevalence of NCCLs in populations older than 30 years (53%) compared to those younger than 30 years (43%) [ ]. Several clinical situations, including dentin hypersensitivity, possibility of pulpal exposure, patient complaining of compromised esthetics caused by the cervical lesion, and when the integrity of the tooth is threatened, would warrant restorative intervention [ ].

Restoration of NCCLs with adhesive materials is challenging, as dentin comprises the largest part of the bonding substrate, with sclerotic dentin present in many of these lesions. The complex morphology and composition of sclerotic dentin make the adhesive procedure even more difficult and prone to failure [ ]. In fact, restorations inserted in NCCLs have a high incidence of retention failure, marginal defects, and secondary caries, representing one of the least durable restorations [ , ].

Some technique-associated factors are also responsible for this poor outcome, including difficult isolation, insertion technique and contouring procedures [ ]. As a result of these issues, NCCLs are the substrate recommended for clinical trials of dentin adhesives, as restoration loss is more likely to occur than in preparations all surrounded by enamel or preparations with macro-retention.

The use of more versatile adhesive systems is appealing to clinicians. A recent generation of dental adhesive known as ”universal” was launched onto the market [ ]. The term “universal” is due to (1) the addition of resinous monomers as 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) to provide chemical bonding to hard tissue tooth and metals [ ]; (2) and also to the versatility of these universal adhesives, as dentists have the opportunity to decide which strategy to use, i.e., etch-and-rinse (ER), self-etch (SE), or selective etching of enamel margins. In addition, universal adhesives can be applied on moist or dry dentin when used in the ER mode [ ].

Randomized clinical trials have shown that the bonding strategy used with universal adhesives does not influence retention after 18–36 months [ ]. Some studies showed that the ER approach resulted in better clinical performance (higher retention rate and lower marginal discoloration) [ , ]. However, a recently review of universal adhesives suggested that long-term clinical studies are needed to assess which adhesion strategy may optimize their clinical outcomes [ ].

In spite of being used for the last 28 years [ ], clinical studies in NCCLs have reported that the ‘wet dentin’ technique does not increase the retention rate for universal adhesives when compared to dry dentin [ , , ]. In fact, for older simplified ER adhesives, active application of the adhesive increases retention rate [ , ]. However, there are no published clinical studies over 36 month follow-up testing this hypothesis.

Therefore, the aim of this randomized double-blind clinical trial was to study the influence of different application strategies on the clinical behavior of a universal adhesive over the course of five years (Scotchbond Universal Adhesive (SU), also known as Single Bond Universal, 3M Oral Care) placed in NCCLs, using two evaluation criteria, World Dental Federation (FDI) and United States Public Health Service (USPHS) criteria. The null hypotheses tested were: (1) the retention rate of restorations of NCCLs bonded with SU do not depend on the adhesive strategy when evaluated by FDI or USPHS criteria, (2) the other secondary outcomes (marginal staining, marginal adaptation, recurrence of caries and post-operative sensitivity) of restorations of NCCLs bonded with SU do not depend on the adhesive strategy when evaluated by FDI or USPHS criteria.

Material and methods

Study design

The description of the experimental design followed the Consolidated Standards of Reporting Trials (CONSORT) statements [ ].

Ethics approval

The Local University (protocol 05909/11) Ethics Committees reviewed and approved the protocol and issued a consent form for this study. Written informed consent was obtained from all participants prior to starting the treatment.

Protocol registration

This clinical trial was registered in the Brazilian Registry of Clinical Trials (REBEC), a national clinical trial registry system under protocol RBR-3BF686. All participants were informed about the nature and objectives of the study.

Trial design, settings and location of data collection

This was a randomized, double-blind clinical trial. The insertion phase of this study was carried out in the clinics of the School of Dentistry at the local University from January 2011 to November 2011.


Subjects were recruited as they sought treatment in the clinics of School of Dentistry of the local university. No advertisement was made for participant recruitment. Patients were recruited in the order in which they reported for the screening session, thus forming a sample of convenience.

Eligibility criteria

A total of 82 participants were examined by two calibrated dentists to check if the subjects met the inclusion and exclusion criteria ( Fig. 1 ). The evaluations were performed using a mouth mirror, an explorer and a periodontal probe. Participants had to be in good general health, at least 18 years old, an acceptable oral hygiene level and present at least 20 teeth under occlusion.

Fig. 1
Flow diagram of the study phases.

Participants were required to have at least four NCCLs to be restored in different teeth. The lesions had to be non-carious, non-retentive, deeper than 1 mm and involve both the enamel and dentin of vital teeth without mobility. The cavo-surface margin could not involve more than 50% of enamel [ ]. All subjects were given oral hygiene instructions before the operative treatment was performed. Patients with extremely poor oral hygiene or using orthodontic devices, severe or chronic periodontitis, or heavy bruxism habits were excluded from the study as they would receive other treatments before restorative intervention. Also, participants with known allergy to resin-based materials or any other material used in this study, pregnant or breastfeeding women, or participants under chronic use of anti-inflammatory, analgesic, and psychotropic drugs were not be included in the study.

Sample size calculation

The sample size calculation was based on the retention rate of the simplified etch-and-rinse Adper Single Bond/Adper Single Bond Plus (3M Oral Care, St. Paul, MN, USA), the predecessors of this universal adhesive from the same manufacturer. The retention was reported to be 94% at 2-years follow-up [ ]. Using an a of 0.05, a power of 80% and a two-sided test, the minimal sample size was 50 restorations in each group in order to detect a difference of 20% among the tested groups [ ].

Randomization sequence generation and allocation concealment

The randomization process was performed using computer-generated tables by a staff member not involved in the research protocol. Details of the allocated group were recorded on cards contained in sequentially numbered, opaque, sealed envelopes. These were prepared by a staff member who was not involved in any of the phases of the clinical trial.

The allocation assignment was revealed by opening the envelope on the day of the restorative procedure, which ensured the concealment of the random sequence. In all cases, the tooth with the highest FDI tooth number received the treatment described first, while the tooth with the next number in sequence received the treatment mentioned second and the next tooth received the treatment mentioned third. The participants and the examiners were blinded to the group assignment.

Interventions: restorative procedure

The same two calibrated dentists involved in the selection of participants carried out the restorative procedures. The features of the NCCLs were evaluated prior to the placement of the restorations. The degree of dentin sclerosis was evaluated according to an earlier scoring system [ ] modified by Swift et al. [ ] ( Table 1 ); the lesion dimensions in millimeters (height, width, and depth); and the geometry of the lesion (evaluated by photograph profile and labeled at <45º, 45º–90°, 90º–135º, >135º) were recorded [ ]. Other features, such as the presence of occlusion wear facet [ ], were also observed and recorded. Pre-operative sensitivity was also evaluated by applying an air stream for 10 s from a dental syringe placed 2 cm from the tooth surface (air dry) and with an explorer (touch).

Table 1
Dentin sclerosis scale.
Dentin sclerosis scale a
Category Criteria
1 No sclerosis present; dentin is light yellowish or whitish, with little discoloration; dentin is opaque, with little translucency or transparency
2 More sclerosis than in category 1 but less than halfway between categories 1 and 4
3 Less sclerosis than in category 4 but more than halfway between categories 1 and 4
4 Significant sclerosis present; dentin is dark yellow or even discolored (brownish); glassy appearance, with significant translucency or transparency evident

a Adapted from Reis and Loguercio [ ] with permission from Elsevier.

To calibrate the restorative procedure, the study director placed one restoration of each group in order to identify all steps involved in the protocol. Then, the two operators with more than five years of clinical experience in operative dentistry placed four restorations of each group in a clinical setting under the supervision of the study director. Any discrepancies of the restorative protocol were identified and discussed with the operator prior to starting the study. At this point, the operators were considered calibrated to perform the restorative procedures. The calibrated operators restored all teeth under the supervision of the study director.

A preliminary dental prophylaxis of the tooth surface was performed with pumice and water in a rubber cup prior to the restorative procedure, followed by rinsing and drying. Local anesthesia was applied with a 3% mepivacaine solution (Mepisv, Nova DFL, Rio de Janeiro, RJ, Brazil), and all restorations were placed under rubber dam isolation. Following the guidelines of the American Dental Association (ADA) [ ] the operators did not prepare any additional retention or bevel.

The NCCLs received the Scotchbond Universal Adhesive system (SU, 3M Oral Care, St. Paul, MN, USA, also known as Single Bond Universal in some countries) applied in different modes: an etch-and-rinse approach, keeping the dentin moist (ERm) or dry (ERd); and a self-etch approach with (Set) or without selective enamel etching (SE). The compositions, application modes, and batch numbers are described in Table 2 .

Table 2
Materials, compositions and application mode.
Adhesive systems Composition/batch number Application mode a
Scotchbond Universal Adhesive (3M Oral Care, St Paul, MN, USA) 1. Scotchbond Universal Etchant: 34% phosphoric acid (UXT-02/Etch-01)
2. Adhesive (UXT-02/Adh-02): methacryloyloxydecyl dihydrogen phosphate, phosphate monomer, dimethacrylate resins, hydroxyethyl methacrylate, methacrylate-modified polyalkenoic acid copolymer, filler, ethanol, water, initiators, silane.
Etch-and-rinse Apply Etchant for 15 s
Rinse for 10 s
Air dry to remove excess of water
KEEP DENTIN MOIST Apply the adhesive for 20 s with vigorous agitation.
Gently air thin for 5 s
Light-cure for 10 s
KEEP DENTIN DRY , do not overdry
Selective etching Apply Etchant ONLY ON ENAMEL for 15 s
Rinse for 10 s
Air dry to remove excess of water
Keep dentin dry, do not overdry
Self-etch DO NOT USE ETCHANT Keep dentin dry, do not overdry

a According to the manufacturer’s instructions.

In the ERm group dentin was kept visibly moist, while in the ERd group dentin was air-dried for 5 s, but not overdried. In the Set group, the lesion was air-dried after rinsing the etchant from the enamel. Dentin was kept dry in both SE groups. The adhesive was vigorously scrubbed on the entire dentin surface in all groups for approximately 20 s, according to the manufacturer’s recommendations ( Table 2 ), followed by gentle air thinning for 5 s and finally light-curing (Radii Cal, SDI, Bayswater, Victoria, Australia) for 10 s (1000 mW/cm 2 ).

After the adhesive application, the resin composite Filtek Supreme Ultra (3M Oral Care, St. Paul, MN, USA) was used in up to three increments, each one being light-cured (Radii Cal, SDI, Victoria, Australia) for 30 s. The restorations were finished immediately with fine diamond burs (KG Sorensen, Barueri, SP, Brazil). Polishing was performed with rubber points (Astropol, Ivoclar Vivadent, Schaan, Liechtenstein) one week after placement of the restorations.

Calibration procedures for clinical evaluation

Two experienced and calibrated dentists who were not involved with the restoration procedures performed the clinical evaluation. An inter-examiner and inter-examiner agreement of at least 85% was necessary before beginning the evaluation [ ].


The examiners were not involved with the restoration procedures and therefore blinded to the group assignment. Subjects were also blinded to group assignment in a double-blind randomized clinical trial design.

Clinical evaluation

All evaluation parameters were recorded using a standardized paper case report form. The evaluation form was sent to the research staff after each observation, so that evaluators were blinded to group assignment during follow-up recalls. The restorations were evaluated using two criteria: the FDI [ , ] and the USPHS criteria (adapted by Dalton Bittencourt et al. and Perdigão et al.) [ , ] immediately after restorative procedure (baseline), and after 6, 18, 36-months and five years of clinical service.

For either of the two criteria, only the clinically relevant measures of the performance of the adhesives were evaluated ( Tables 3 and 4 ). The primary outcome was retention/fracture, but the following secondary outcomes were also evaluated: marginal staining, marginal adaptation, post-operative sensitivity and recurrence of caries. The post-operative sensitivity was performed one week after the restorative procedure, by applying an air stream from a dental syringe for 10 s at 2 cm from the tooth surface.

Table 3
World Dental Federation (FDI) criteria used for clinical evaluation [ , ].
Esthetic Property Functional Properties Biological Properties
1. Staining margin 2. Fractures and retention 3. Marginal adaptation 4. Postoperative (hyper-) sensitivity 5. Recurrence of caries
1. Clinically very good 1.1 No marginal staining 2.1 Restoration retained, no fractures/cracks 3.1 Harmonious outline, no gaps, no discoloration. 4.1 No hypersensitivity. 5.1 No secondary or primary caries
2. Clinically good (after correction very good 1.2 Minor marginal staining, easily removable by polishing. 2.2 Small hairline crack. 3.2.1 Marginal gap (50 μm). 4.2 Low hypersensitivity for a limited period of time 5.2 Very small and localized demineralization.
3.2.2 Small marginal fracture removable by polishing. No operative treatment required
3.Clinically sufficient/satisfactory (minor shortcomings with no adverse effects but not adjustable without damage to the tooth) 1.3 Moderate marginal staining, not esthetically unacceptable. 2.3 Two or more or larger hairline cracks and/or chipping (not affecting the marginal integrity). 3.3.1 Gap <150 μm not removable 4.3.1 Premature/slightly more intense 5.3 Larger areas of demineralization, but only preventive measures necessary (dentine not exposed)
3.3.2. Several small enamel or dentin fractures 4.3.2 Delayed/weak sensitivity; no subjective complaints, no treatment needed.
4. Clinically unsatisfactory (repair for prophylactic reasons) 1.4 Pronounced marginal staining; major intervention necessary for improvement 2.4 Chipping fractures which damage marginal quality; bulk fractures with or without partial loss (less than half of the restoration). 3.4.1 Gap >250 μm or dentine/base exposed. 4.4.1 Premature/very intense 5. 4 Caries with cavitation (localized and accessible and can be repaired
3.4.2. chip fracture damaging margins 4.4.2 Extremely delayed/weak with subjective complaints 4.4.3 Negative Sensitivity Intervention necessary but not replacement.
3.4.3 Notable enamel or dentine wall fracture
5. Clinically poor (replacement necessary) 1.5 Deep marginal staining not accessible for intervention. 2.5 (Partial or complete) loss of restoration. 3.5 Filling is loose but in situ. 4.5 Very intense, acute pulpitis or non vital. Endodontic treatment is necessary and restoration has to be replaced. 5.5 Deep secondary caries or exposed dentine that is not accessible for repair of restoration.
Acceptable or not acceptable (n, % and reasons Aesthetic criteria Functional criteria Biological criteria

Table 4
Modified United States Public Health Service (USPHS) criteria according to Dalton Bittencourt et al. [ ] and Perdigão et al. [ ].
Marginal staining Retention Fracture Marginal adaptation Postoperative sensitivity Recurrence of caries
Alfa No discoloration along the margin Retained None Restoration is continuous with existing anatomic form. No postoperative sensitivity directly after the restorative process and during the study period No evidence of caries contiguous with the margin
Bravo Slight and superficial staining (removable, usually localized) Partially retained Small chip, but clinically acceptable Detectable V-shaped defect in enamel only. Catches explorer going both ways.
Charlie Deep staining cannot be polished away Missing Failure due to bulk restorative fracture Detectable V-shaped defect to dentin-enamel junction Sensitivity present at any time during the study period Evidence of presence of caries

These variables were ranked according to the criteria in the following scores: (1) FDI criteria (clinically very good [VG]; clinically good; clinically sufficient/satisfactory; clinically unsatisfactory [UN] and clinically poor) and (2) USPHS criteria (Alfa – good, Bravo – satisfactory and Charlie – poor). Both examiners evaluated all the restorations once and independently. When disagreements occurred during the evaluations, they had to reach a consensus before the participant was dismissed. The restoration retention rates were calculated according to the ADA guidelines [ ]. Cumulative failure percentage = [(PF + NF)/(PF + RR)] × 100, where PF is the number of previous failures before the current recall, NF is the number of new failures during the current recall, and RR is the number of currently recalled restorations.

Statistical analysis

The statistical analyses followed the intention-to-treat protocol according to CONSORT (Consolidated Standards of Reporting Trials) suggestion [ ] Descriptive statistics were used to describe the distributions of the evaluated criteria.

The survival rates (retention/fracture data) of different groups of restorations were calculated by the Kaplan–Meier procedure, estimating the Hazard Ratios (HR) and 95% confidence intervals. The log-rank test was used to compare the survival distributions of these restorations ( α = 0.05).

For the secondary outcome (marginal staining, marginal adaptation, postoperative sensitivity, and recurrence of caries), in each overall parameter (FDI and USPHS), the differences between the ratings of the four groups after 5 years were tested by Friedman’s repeated measures analysis of variance rank ( α = 0.05). Cohen’s kappa statistics were used to test the inter-examiner agreement ( α = 0.05) (MedCalc Software, Version 19.1, Ostend, Belgium).


Forty-three out of 82 subjects were excluded from the study because they did not fulfill the inclusion criteria. Thus, a total of 39 subjects (24 male and 15 female), with a mean age of 40 years were enrolled in this study. Two hundred restorations were placed, 50 for each group. All baseline details relative to the research subjects and characteristics of the restored lesions are displayed in Table 5 .

Table 5
Characteristics of the research subjects and the non-carious cervical lesions (NCCLs) per group.
Characteristics of research subjects Number of lesions
Gender distribution
Male 24
Female 15
Age distribution (years)
20–29 05
30–39 12
39–49 12
>49 10

Characteristics of NCCLs Number of lesions
ER m ER d SE et SE
Shape (degree of angle)
45–90 14 14 12 12
90–135 34 34 38 38
>135 02 02
Cervico-incisal height (mm)
<1.5 06 03 05 07
1.5–2.5 29 36 29 30
2.5–4.0 12 10 14 12
>4.0 03 01 02 01
Degree of sclerotic dentin
1 20 18 17 19
2 12 14 13 10
3 12 12 09 09
4 06 06 11 12
Presence of antagonist
Yes 50 50 50 50
No 00 00 00 00
Attrition facet
Yes 24 22 18 26
No 26 28 32 24
Pre-operative sensitivity (spontaneous)
Yes 50 50 50 50
No 00 00 00 00
Pre-operative sensitivity (air dry)
Yes 24 26 30 28
No 26 24 20 22
Tooth distribution
Incisor 02 02 02 02
Canines 04 08 06 08
Premolar 32 26 34 28
Molar 12 14 08 12
Arc distribution
Maxillary 25 26 30 28
Mandibular 25 24 20 22

The overall Cohen’s Kappa statistics (0.92) showed good agreement between the examiners. All research subjects were evaluated at the baseline and at the 6 month recalls. One subject did not attend the 18 months recall, four subjects did not attend the 36 months recall and two other subjects did not attend the 5-years recall. All of them had moved to another city.


All the data regarding follow-up times are depicted in Tables 6 and 7 . However, only the 5-year data are described here. After 5 years of clinical evaluation, 19 restorations were lost (3 for ER m , 3 for ER d , 5 for SE et and 8 for SE). According to FDI and USPHS criteria, the 5-year retention/fracture rates (95% confidence interval) was 93% (95% CI 81.4–97.6%) for ER m , 93% (95% CI 81.4–97.6%) for ER d, 88.4% (95% CI 75.5–94.9) for SE et and 81.4% (95% CI 67.4–90.3%) for SE ( Table 8 ).

Jan 10, 2021 | Posted by in Dental Materials | Comments Off on Five-year clinical evaluation of a universal adhesive: A randomized double-blind trial

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