Six-year clinical performance of etch-and-rinse and self-etch adhesives

Abstract

Objective

To evaluate the 6-year clinical performance of Xeno IV, Xeno III, and XP Bond adhesives in the restoration of non-carious cervical lesions (NCCLs).

Methods

This was a randomized controlled clinical trial where 39 participants met the inclusion/exclusion criteria and were enrolled. Lesions restored were notch-shaped NCCLs. Prior to adhesive procedures, NCCLs were roughened. No enamel bevel was placed and no mechanical retention was created. Adhesive systems were applied following manufacturer’s instructions and the NCCLs were restored with composite resin (TPH 3 ). Restorations were finished immediately after placement and scored with regard to retention, marginal discoloration, marginal adaptation, sensitivity, and secondary caries using modified USPHS criteria. Descriptive statistics were performed. Logistic regression models were performed for each outcome separately with compound symmetry correlation structure where teeth were clustered by participants. All analyses were conducted using SAS 9.2.

Results

The 6-year recall rate was 77.5% of the restorations (76.9% of the participants). No statistical differences were found between adhesives for retention, marginal discoloration, and marginal adaptation. Restorations failed by loss of retention (16.7%, 27.6%, and 11.8% of Xeno IV, Xeno III, and XP Bond restorations, respectively) and marginal discoloration (7.4% of Xeno IV restorations). For every unit increase in restoration volume it was 1.31 (95% C.I. 1.05, 1.63, P = 0.01) times more likely that the restoration retention would be maintained.

Significance

The tested adhesive systems presented similar clinical performance after six years of service, with annual failure rates of 2.8%, 4.6%, and 2.0% for Xeno IV, Xeno III, and XP Bond, respectively.

Introduction

Mild self-etch adhesives have been favored over other available adhesives for dentin bonding . Laboratory studies suggest that the benefit of mild (pH ≥ 1.5, i.e., less aggressive) dentin etching may be two fold: 1) mild etching allows some mineral to remain complexed with the superficial dentin which may reduce the potential for hybrid layer deterioration and subsequent dentin bond failure and 2) mild self-etch formulations that contain resin monomers with a chemical affinity for hydroxyapatite (“functional monomers”) may form more stable bonds . Hybrid layer deterioration is thought to occur through the combined effects of water entrapment, leading to subsequent resin hydrolysis, and exposure/activation of host collagenolytic enzymes, leading to collagen degradation . The combination of limited demineralization and mineral affinity of the adhesive resin may lead to more stable bonding . Improved diffusion of the resin monomers into the superficial dentin collagen matrix may increase the efficiency and stability of the adhesion process . However, it is currently unknown if the small, relatively hydrophilic resin molecule dipentaerythritol penta acrylate monophosphate (PENTA), included in two of the adhesives tested in this clinical trial, is capable of developing a stable chemical bond with calcium hydroxyapatite in tooth structure.

Other adhesive systems rely on creating conditions that result in increased demineralization of the superficial dentin collagen via the use of phosphoric acid (prior to adhesive application) or on adhesive resin compositions with very low pH. These systems rely strictly on micromechanical infiltration for attachment to the dentin substrate and appear not to have a chemical affinity for bonding to the dentin substrate. There are concerns that these more aggressive etching procedures result in a demineralized dentin layer that cannot be fully infiltrated with the adhesive resin . The resultant partial infiltration of the exposed demineralized dentin may consequently lead to the formation of a weak and vulnerable hybrid layer . Long-term clinical data, which supports the use of mild self-etch adhesives over other materials, is limited in both the number of trials and the materials tested . The need to expand the current knowledge is evident and further clinical research may lead to greater understanding of the clinical implications of limitations identified in the laboratory setting.

A recent systematic review on the clinical performance of contemporary adhesives has found mild two-step self-etch adhesives to present the best clinical bonding effectiveness in non-carious cervical lesions (NCCLs) while inadequate outcomes were found for strong self-etch (pH < 1.5) and two-step etch-and-rinse adhesives . The available literature reveals an abundance of short-term clinical studies and a shortage of long-term studies that compare mild self-etch to other adhesives when used in NCCLs . In six studies with follow-up times exceeding five years, only four materials were studied – namely Clearfil Liner Bond II (Kuraray Co. Ltd., Okayama, Japan), Clearfil SE Bond (Kuraray), G-Bond (GC Corporation, Tokyo, Japan), and AdheSE (Ivoclar Vivadent, Schaan, Principality of Liechtenstein) .

Xeno IV (Dentsply Caulk, Milford, DE, USA) is a one-step mild self-etch adhesive that was introduced in the mid-2000s. An in vitro study has shown that the material can maintain its bond strengths to dentin after two years of water storage , which, in another study, sufficed to retain Class V restorations in place after artificial aging . The translation of these findings into clinical practice is yet to be shown as no clinical data on this material is available. Its antecessor Xeno III (Dentsply Caulk), is a one-step two-bottle self-etch adhesive with pH < 1 (strong) compared to the pH ∼ 2.1 of Xeno IV . Xeno III has shown retention rates of at least 83% over two years of clinical service in NCCLs . When Xeno III is applied using scrubbing/rubbing motion, retention rates of 83.8% after seven years of clinical service have been reported . Dentsply Caulk also has produced XP Bond, a two-step etch-and-rinse adhesive system that has been evaluated in several clinical trials. This material has demonstrated retention rates ranging from 100% at six months to 72.9% at five years . Peumans and colleagues conducted a systematic review that suggested that mild one-step self-etch adhesives (e.g., Xeno IV) may outperform strong one-step self-etch (e.g., Xeno III) as well as two-step etch-and-rinse adhesives (e.g., XP Bond) .

The need for long-term clinical data comparing mild one-step, strong one-step and two-step etch-and-rinse materials from the same manufacturer led to the design and implementation of this clinical trial. The present study evaluated the 6-year clinical performance of Xeno IV, Xeno III, and XP Bond adhesives in the restoration of NCCLs. No selective etching of enamel was performed as there is no clinical data supporting that extra step . The hypothesis tested was that Xeno IV would demonstrate better clinical performance than Xeno III and XP Bond with regard to retention, marginal discoloration, and marginal adaptation. Restorations were evaluated using modified USPHS criteria.

Materials and methods

This was a randomized controlled clinical trial that evaluated the clinical performance of three dental adhesives used with a microhybrid composite resin in the restoration of NCCLs in permanent teeth. The Institutional Review Board (IRB) of the University of North Carolina at Chapel Hill (UNC-CH) approved the study, protocol # 07-0673. Participants were recruited using IRB-approved fliers posted around the UNC-CH campus and from the patient pool at the Dental Faculty Practice at the UNC-CH.

Adults (18+ years of age) who were in need of the restoration of at least one NCCL and that fulfilled inclusion criteria were enrolled in the study. To participate in the study, individuals could not have fewer than 20 teeth, exhibit poor oral hygiene or uncontrolled periodontal disease, be pregnant or lactating mothers, have known allergies to resin-based materials, or have medical conditions that contraindicate dental treatment. Teeth to be restored had to have NCCLs with no undercuts, be notch-shaped with internal angles of not more than 135° (saucer-shaped lesions were excluded), have not more than 50% of the cavosurface margins involving enamel, and have at least one occlusal contact. At enrollment, the participants were informed of their health information privacy rights in accordance with the Health Insurance Portability and Accountability Act (HIPAA) of 1996. Informed consent was obtained.

Included teeth were allocated to be restored with three different dental adhesives: 1) the one-step self-etch adhesive Xeno IV (one-bottle), 2) the one-step self-etch adhesive Xeno III (a mixture of equal amounts from two bottles that is applied as one-step), and 3) the two-step etch-and-rinse adhesive XP Bond. A maximum of two restorations using each type of adhesive per participant were allowed in order to minimize the potential for strong participant-related effects on research study outcomes. The Universal Numbering System (# 1 – # 32) was used to identify each individual tooth. Teeth were allocated (randomized) for treatment as participants were enrolled in the research study as follows: The first tooth in need of restoration was assigned to the Xeno IV group. The next tooth to be restored was selected in ascending order and restored with Xeno III. This was then followed by a restoration with XP Bond and so on. The adhesive used for the first restoration in the next participant was the next in queue, respecting the Xeno IV–Xeno III–XP Bond order.

Thirty-nine participants with age ranging from 30 to 75 years (mean of 55.4 ± 9.5) received 120 restorations ( n = 40 for Xeno IV group, n = 39 for Xeno III group, and n = 41 for XP Bond group). Participants were 26 females and 13 males. The following parameters for sample size calculation were considered: type 1 error = 5%, power = 80%, difference of the probability = 0.10, drop out = 20%, with each participant having an average of three restored teeth. With these parameters considered, it was found that 35 participants would be needed. The clinical variables of restoration volume (as determined by height, width, depth of the NCCL) and degree of dentin sclerosis of each NCCL (as measured by the UNC Sclerosis Scale ) were determined preoperatively and were included as covariates in the statistical analysis.

The six operating dentists in this study placed the same number of total restorations with similar numbers of each adhesive system being evaluated ( Table 1 ). Preparation procedures included roughening of the internal aspect of the NCCLs with a diamond only. After roughening, preparations were washed and lightly dried with the aid of an air–water syringe. The tooth surfaces remained slightly hydrated with no signs of desiccation prior to adhesive application. No bevels or other type of macro mechanical retention features were added. Operators were blinded to the adhesives brand names but for obvious reasons (number of steps) were not blinded to the type of adhesive (self-etch vs. etch-and-rinse). Restorative procedures were generally performed using cotton roll isolation. A proper-sized gingival retraction cord was placed and the adhesive was applied according to manufacturer’s instructions ( Table 2 ). The NCCLs were restored with the composite resin TPH 3 (Dentsply Caulk) using a freehand technique (no matrix materials were used). Increments up to 2 mm in thickness were placed and light polymerized for 20 s. Light polymerization procedures were performed using the SmartLite iQ2 (Dentsply Caulk) and consistent light output was verified. Restorations were immediately finished using 12-bladed carbide burs and polished using points/cups.

Table 1
Descriptive statistics for a total number of 120 teeth restored in 39 participants. Data is listed as frequency (percentage) at year 6 for the outcomes retention, marginal discoloration and marginal adaptation; frequency for the covariates of gender, dentist, tooth type and sclerotic dentin; and mean volume (+/- SD) of restorations placed for each adhesive system. Percentages shown represent percentage of restorations that received a specific modified USPHS score relative to number of restorations evaluated. “Missing” restorations (unavailable for evaluation), which are included in this table, were excluded from the calculations of the percentages shown.
Type Variable Total
( n = 120)
Xeno IV
( n = 40)
Xeno III
( n = 39)
XP Bond
( n = 41)
Outcome Retention Alfa 76 (81.7%) 25 (83.3%) 21 (72.4%) 30 (88.2%)
Charlie 17 (18.3%) 5 (16.7%) 8 (27.6%) 4 (11.8%)
Missing 27 10 10 7
Marginal discoloration Alfa 62 (79.5%) 21 (77.8%) 15 (71.4%) 26 (86.7%)
Bravo 14 (17.9%) 4 (14.8%) 6 (28.6%) 4 (13.3%)
Charlie 2 (2.6%) 2 (7.4%) 0 (0.0%) 0 (0.0%)
Missing 42 13 0/18 0/11
Marginal adaptation Alfa 68 (87.2%) 22 (81.5%) 20 (95.2%) 26 (86.7%)
Bravo 10 (12.8%) 5 (18.5%) 1 (4.8%) 4 (13.3%)
Charlie 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%)
Missing 42 13 18 11
Covariate Gender Female 84 29 28 27
Male 36 11 11 14
Dentist AW 20 5 7 8
ES 20 8 5 7
HH 20 8 5 7
JS 20 6 8 6
LB 20 6 7 7
RW 20 7 7 6
Tooth type Canine 11 3 4 4
Incisor 5 2 1 2
Molar 28 12 8 8
Premolar 76 23 26 27
Sclerotic dentin 1 34 14 10 10
2 62 18 21 23
3 21 7 7 7
4 3 1 1 1
Mean volume (mm 3 ) 10.71 ± 10.80 11.49 ± 11.94 10.08 ± 10.71 10.55 ± 9.89

Table 2
Manufacturer’s instructions for application of Xeno IV, Xeno III, and XP Bond.
Xeno IV
One-step, single bottle, self-etch adhesive
1. Apply adhesive with scrubbing motion for 15 s
2. Apply second coat with scrubbing motion for 15 s
3. Remove excess solvent with gentle stream of air for at least 5 s
4. Re-apply adhesive if surface is not glossy
5. Light cure for 10 s
Xeno III
One-step, two-bottle, self-etch adhesive
1. Dispense equal amounts of liquids A and B
2. Mix for ∼5 s
3. Apply adhesive and leave undisturbed for 20 s
4. Spread adhesive with gentle stream of air for at least 2 s until no movement is noticed
5. Re-apply adhesive if surface is not glossy
6. Light cure for 10 s
XP Bond
Two-step, etch-and-rinse adhesive
1. Apply Caulk 34% Tooth Conditioner Gel to enamel and dentin for 15 s
2. Rinse for 10 s and blot
3. Apply adhesive and leave undisturbed for 20 s
4. Remove excess solvent with gentle stream of air for at least 5 s
5. Re-apply adhesive if surface is not glossy
6. Light cure for 10 s

Two examiners used modified USPHS criteria to evaluate the restorations for retention, marginal discoloration, marginal adaptation, sensitivity, and secondary caries at baseline and at each reevaluation appointment (6, 18, 36, and 72 months) ( Table 3 ). The first examiner evaluated the restoration chairside while the second examiner evaluated the restoration using digital photographs. The two examiners worked independently. A third examiner reviewed the rating of the two examiners and developed a consensus rating.

Table 3
Modified USPHS direct evaluation criteria.
Criteria Classification
Retention Alfa = Retained
Charlie = Mobile or missing
Marginal discoloration Alfa = No discoloration at margins
Bravo = Shallow discoloration (localized or generalized)
Charlie = Deep discoloration (localized or generalized)
Marginal adaptation Alfa = No visible evidence of a crevice along the margin into which the explorer will penetrate.
Bravo = Visible evidence of a crevice along the margin, dentin not exposed, clinically acceptable
Charlie = Explorer penetrates into crevice, dentin is exposed, clinically unacceptable
Sensitivity Alfa = No
Bravo = Yes
Secondary caries Alfa = No
Charlie = Yes

The overarching goal of this research study was to assess the ability of these systems to create a lasting, uncompromised adhesive interface with tooth structure. A compromised interface may result in any or all of the following: 1) loss of the restoration (retention = Charlie), 2) loss of some of the adhesive interface and resultant staining (either localized or generalized, shallow or deep) along the periphery of the restoration (marginal discoloration = Bravo or Charlie), or 3) loss of some of the adhesive interface, as well as superficial restorative material, resulting in a crevice (various levels of defect detectable by sight or explorer) along the periphery of the restoration (marginal adaptation = Bravo or Charlie). Therefore, for the purposes of this research study, the primary outcome was restoration retention and the secondary outcomes were marginal discoloration and marginal adaptation. The primary outcome variable was binary at year 6: Restoration retention (Alfa score at both baseline and year 6) vs. loss of restoration retention (Alfa at baseline but Charlie at year 6). The secondary outcome variable of marginal discoloration was binary at year 6: No discoloration (Alfa score at both baseline and year 6) vs. the presence of marginal discoloration (Alfa at baseline but Bravo or Charlie at year 6). The secondary outcome variable of marginal adaptation was binary at year 6: Optimal marginal adaptation (Alfa score at both baseline and year 6) vs. sub-optimal marginal adaptation (Alfa at baseline but Bravo or Charlie at year 6). The goal of the statistical analysis was to compare adhesive effect on the outcome variables at year 6 adjusted for the covariates volume of restoration and sclerotic dentin classification . The approximate volume of the restorations was measured by multiplying the recorded width, height, and depth and reported in mm 3 . Descriptive statistics on the outcome variables (retention, marginal discoloration, marginal adaptation) and covariates (patient gender, dentist/restoration distribution, tooth type/restoration distribution, sclerotic dentin and restoration volume) were performed ( Table 1 ). Annual failure rates were calculated by dividing the percentage of failures in each adhesive group by the number of years. Logistic regression models were developed for each outcome, separately, with compound symmetry correlation structure where teeth were clustered by participants. All analyses were conducted using SAS 9.2 (SAS Ins, Cary, NC).

Materials and methods

This was a randomized controlled clinical trial that evaluated the clinical performance of three dental adhesives used with a microhybrid composite resin in the restoration of NCCLs in permanent teeth. The Institutional Review Board (IRB) of the University of North Carolina at Chapel Hill (UNC-CH) approved the study, protocol # 07-0673. Participants were recruited using IRB-approved fliers posted around the UNC-CH campus and from the patient pool at the Dental Faculty Practice at the UNC-CH.

Adults (18+ years of age) who were in need of the restoration of at least one NCCL and that fulfilled inclusion criteria were enrolled in the study. To participate in the study, individuals could not have fewer than 20 teeth, exhibit poor oral hygiene or uncontrolled periodontal disease, be pregnant or lactating mothers, have known allergies to resin-based materials, or have medical conditions that contraindicate dental treatment. Teeth to be restored had to have NCCLs with no undercuts, be notch-shaped with internal angles of not more than 135° (saucer-shaped lesions were excluded), have not more than 50% of the cavosurface margins involving enamel, and have at least one occlusal contact. At enrollment, the participants were informed of their health information privacy rights in accordance with the Health Insurance Portability and Accountability Act (HIPAA) of 1996. Informed consent was obtained.

Included teeth were allocated to be restored with three different dental adhesives: 1) the one-step self-etch adhesive Xeno IV (one-bottle), 2) the one-step self-etch adhesive Xeno III (a mixture of equal amounts from two bottles that is applied as one-step), and 3) the two-step etch-and-rinse adhesive XP Bond. A maximum of two restorations using each type of adhesive per participant were allowed in order to minimize the potential for strong participant-related effects on research study outcomes. The Universal Numbering System (# 1 – # 32) was used to identify each individual tooth. Teeth were allocated (randomized) for treatment as participants were enrolled in the research study as follows: The first tooth in need of restoration was assigned to the Xeno IV group. The next tooth to be restored was selected in ascending order and restored with Xeno III. This was then followed by a restoration with XP Bond and so on. The adhesive used for the first restoration in the next participant was the next in queue, respecting the Xeno IV–Xeno III–XP Bond order.

Thirty-nine participants with age ranging from 30 to 75 years (mean of 55.4 ± 9.5) received 120 restorations ( n = 40 for Xeno IV group, n = 39 for Xeno III group, and n = 41 for XP Bond group). Participants were 26 females and 13 males. The following parameters for sample size calculation were considered: type 1 error = 5%, power = 80%, difference of the probability = 0.10, drop out = 20%, with each participant having an average of three restored teeth. With these parameters considered, it was found that 35 participants would be needed. The clinical variables of restoration volume (as determined by height, width, depth of the NCCL) and degree of dentin sclerosis of each NCCL (as measured by the UNC Sclerosis Scale ) were determined preoperatively and were included as covariates in the statistical analysis.

The six operating dentists in this study placed the same number of total restorations with similar numbers of each adhesive system being evaluated ( Table 1 ). Preparation procedures included roughening of the internal aspect of the NCCLs with a diamond only. After roughening, preparations were washed and lightly dried with the aid of an air–water syringe. The tooth surfaces remained slightly hydrated with no signs of desiccation prior to adhesive application. No bevels or other type of macro mechanical retention features were added. Operators were blinded to the adhesives brand names but for obvious reasons (number of steps) were not blinded to the type of adhesive (self-etch vs. etch-and-rinse). Restorative procedures were generally performed using cotton roll isolation. A proper-sized gingival retraction cord was placed and the adhesive was applied according to manufacturer’s instructions ( Table 2 ). The NCCLs were restored with the composite resin TPH 3 (Dentsply Caulk) using a freehand technique (no matrix materials were used). Increments up to 2 mm in thickness were placed and light polymerized for 20 s. Light polymerization procedures were performed using the SmartLite iQ2 (Dentsply Caulk) and consistent light output was verified. Restorations were immediately finished using 12-bladed carbide burs and polished using points/cups.

Nov 23, 2017 | Posted by in Dental Materials | Comments Off on Six-year clinical performance of etch-and-rinse and self-etch adhesives
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