A randomized controlled 5-year prospective study of two HEMA-free adhesives, a 1-step self etching and a 3-step etch-and-rinse, in non-carious cervical lesions

Abstract

Objective

The aim of this study was to evaluate the 5 year clinical dentin bonding effectiveness of two HEMA-free adhesives in Class V non-carious cervical lesions.

Material and methods

A total of 169 Class V restorations were placed in 67 patients with a self-etching adhesive (G-Bond; 67), a 3-step HEMA and TEGDMA free etch-and-rinse (cfm; 51) and a control HEMA-containing etch-and-rinse adhesive (XP Bond; 51) in non-carious cervical lesions without intentional enamel involvement. The restorations were evaluated at baseline and yearly during a 5 year follow-up with modified USPHS criteria. Dentin bonding efficiency was determined by the percentage of lost restorations.

Results

During the 5 years, 159 restorations could be evaluated. Good short time dentin retention was observed for the three adhesives, there all adhesives fulfilled at 18 months the full acceptance ADA criteria. At 5 years a cumulative number of 22 lost restorations (13.8%) was observed. The HEMA-free adhesives showed significantly higher dentin retention compared to the HEMA-containing one. Loss of retention was observed for 5 G-Bond (7.9%), 4 cfm (8.3%) and 13 XP Bond (27.1%) restorations ( p < 0.05). No post-operative sensitivity was reported by the participants. No secondary caries was observed.

Significance

The durability in non-carious cervical lesions of the HEMA-free adhesives was successful after 5 years. Despite concerns which have been raised, showed the 1-step SEA one of the best reported clinical dentin bonding effectiveness.

Introduction

Adhesive systems have revolutionized and are routinely used in operative dentistry to improve retention, sealing and esthetics of resin-based materials. The interaction with the tooth substrates is today based on the etch-and-rinse or the non-rinse self-etch approach. Self-etching adhesives (SEA) contain acidic monomers which simultaneously condition and prime the smear layer and underlying tooth tissues. Clinical advantages suggested are its decreased technique sensitivity, decreased application time and decreased risk for re-contamination of the etched tooth surfaces and/or collapse of the collagen network after air drying. Disadvantages reported are that 1-step SEA’s are more hydrophilic and can absorb rapidly water which result in higher solubility and water uptake. This may result in polymer swelling, plasticization and weakening of the polymer network . One-step SEA’s may act as semi permeable membranes, permitting water movement through the layer even after polymerization .

Diffusion of monomers into the demineralised tooth tissues to create a hybrid layer is considered to be the essential mechanism of adhesive bonding. HEMA (2-hydroxyethyl methacrylate), an effective hydrophilic methacrylate primer monomer, is frequently present in dental adhesives. It improves dentin bond strength due to its wetting enhancement effect and promotes diffusion of co-monomers by expanding the demineralised collagen . In 1-step SEA adhesives HEMA maintain the resin monomers and water in one solution and prevent phase separation . However, high HEMA content promotes water uptake and subsequent gradual hydrolytic degradation of the polymers, swelling and staining . Increased water uptake might accelerate the reduction of mechanical properties of the SEA . Omission of HEMA in adhesives leads to phase separation between water and the adhesive monomers, which requires strongly air blowing to remove the water-containing droplets from the interface .

Methacrylate monomers are potent contact allergens and especially the low weight monomer HEMA is considered as one of the most potent ones . Fast penetration of non cured monomers through the skin and gloves cause contact dermatitis in dental personal . In addition another commonly used low viscous monomer TEGDMA has been associated with cytotoxic reactions . Unpolymerized HEMA remain chemically and physically unchanged and can leach up to 30 days . Organic solvents can solve higher amounts compared to water or saliva only .

Assessing the bonding effectiveness of adhesives in vitro showed that 3-step etch-and-rinse adhesives performed best, irrespective of bond strength test . Two-step SEA conducted better than the all-in-one systems . However, laboratory tests cannot predict the clinical situation and Class-V clinical trials remain therefore the ultimate studies to test adhesives . In an earlier review of clinical Class V studies it was concluded that etch-and-rinse adhesives were more efficient than SEA’s . Lower microtensile bond strength have been reported for SEA especially to enamel . However, recent Class V clinical trials showed that 1-step SEA’s substantially improved with annual failure rates in line with the etch-and-rinse adhesives .

The disadvantages of HEMA have led to the introduction of HEMA-free less hydrophilic adhesives which may show reduced water sorption, higher stability of mechanical properties, stability of the interfacial bond, improvement in bonding durability and reduced allergenic potential . Short time evaluation of HEMA-free adhesives showed a satisfactory performance .

The purpose of this study was to determine the long term clinical bonding durability of a 1-step HEMA-free SEA, a 3-step HEMA/TEGDMA-free etch-and-rinse and a 3-step HEMA containing etch-and-rinse adhesive in Class V non-carious cervical lesions without using retention of external lesion surface area. The null hypothesis tested was that there is no difference in durability of the clinical dentin bond formed with the HEMA-free and HEMA-containing adhesives.

Material and methods

During the period May 2006–October 2007, all patients attending the author’s PDHS clinic at the dental school Umeå, for who treatment of non-carious cervical lesions was indicated were requested to participate in the study. No patient was excluded because of caries activity, periodontal condition or parafunctional habits. All participants received informed consent and the study was approved by the commission for medical ethics of the University of Umeå. A total of 169 Class V restorations were placed in 67 patients, 34 men and 33 women with a mean age of 64.7 year (min–max 39–84), who needed treatment of non carious cervical lesions. All restorations were placed by one experienced operator, familiar with adhesive dentistry, in dentin lesions without any intentional enamel involvement. Pre-operatively, the lesions were categorized by the operator compared to lesion models in terms of depth (shallow, moderate, large) and size (small, moderate, large) of the lesion, the area of the dentin surface estimated as sclerotic tissue (0, <50%, >50%) ( Table 1 ) .

Table 1
Baseline data, distribution and lesion characteristics, of the lesions included.
G-Bond cfm XP Bond
Teeth
Incisor/cuspidate 25 16 23
Premolar 30 19 20
Molar 12 16 8
Jaw
Maxilla 34 40 37
Mandible 33 11 14
Lesion size
Small 11 7 18
Medium 23 33 19
Large 33 11 13
Lesion depth
Superfiscial 24 28 33
Medium 27 17 13
Deep 16 6 5
Degree of sclerosis
0% 19 25 26
<50% 6 8 10
>50% 42 18 15

A single-step, self-etching HEMA-free primer (G-Bond, GC Corp, Tokyo, Japan), a 3-step HEMA/TEGDMA free etch-and-rinse (cfm, Saremco AG, Rebstein, Switzerland) and a 2-step HEMA-containing etch-and-rinse adhesive (XP Bond, Dentsply/DeTrey, Konstanz, Germany) were evaluated in combination with two restorative resinous materials ( Table 2 ). The resin composite Gradia Direct (GC Corp) was used in combination with G-Bond, and els (extra low shrinkage; Saremco) in combination with the two other adhesives. After the operative procedure decision, the lesions were filled in randomly order by three adhesive systems. In subjects with two or more lesions, different adhesives were applied in the lesions to make intra-individual comparison possible.

Table 2
Composition and application methods of the adhesive systems tested.
Adhesive Composition Manufacturer Application
G-Bond 1-step SEA 4-MET, UDMA, TEGDMA, phosphoric acid monomer, photo-initiator, stabilizer, fumed silica filler, acetone, water pH = 2.0 GC Corp, Tokyo, Japan lot 0506141 Apply adhesive on the air dried dentin surface. Agitating for 5 s and reapply if necessary. Leave undisturbed for 10 s.
Dry strongly with air with maximum pressure for 5 s.
cfm adhesive system cmf etch : buffered phosphoric acid (pH = 1.5)
cmf primer : metacrylated phosphoric salt, alcohol, aceton, CQ, co-initiator
cmf bonding : hydrophilic ethoxylated Bis-GMA, silanized barium glass, CQ, co-initiator.
Saremco AG, Rebstein, Switzerland
primer lot 06.2011.01
bonding lot 06.2011.05
Etch for 15 s enamel and dentin
Rinse for 30 s
Air dry for 5 s
Apply cmf primer using a rubbing motion for 30 s, dry for 5 s and light cure for 20 s
Apply cmf bonding using a rubbing motion for 20 s
Light cure for 30 s
XP Bond 2-step etch-and-rinse Conditioner: 36% phosphoric acid: primer: TCB, PENTA, UDMA, TEGDMA, HEMA, butylated benzenediol (stabilizer), ethyl-4-dimethylaminobenzoate, CQ, amorphous silica, tertiary butanol DeTrey Dentsply, Konstanz, Germany lot 0701000 Apply conditioner to the lesion surface for 15 s
Rinse thoroughly for 10 s and dry but do not desiccate
Apply adhesive and leave undisturbed for 20 s
Air blow for min 5 s.
Light cure for 20 s.
els (extra low shrinkage) resin composite Bis-GMA, Bis-EMA, silanized barium glass, catalysts, inhibitors, pigment Saremco AG, Rebstein, Switzerland
lot 10.2010-006
Gradia Direct resin composite GC Corp, Tokyo, Japan
lot 121222
Abbreviations : HEMA, 4-MET 4-methacryloxyethyl trimetellitic acid; PENTA, phosphoric acid modified acrylate resin; TCB, resin carboxylic acid modified dimethacrylate; TEGDMA, triethyleneglycol dimethacrylate; Bis GMA, bisphenol A-glycidyl methacrylate; Bis EMA, Bisphenol A ethoxylate dimethacrylate; UDMA, urethane dimethacrylate; CQ, camphorguinone.

Operative procedure

After randomization, the lesions were slightly roughened by a diamond bur before application of the adhesive systems to create a surface smear layer. The operative field was isolated with cotton rolls and a saliva suction device. The adjacent gingiva was retracted by gingival retraction instruments when necessary to secure unrestricted contamination free access to the field. In order not to enlarge the retention area, according to the ADA guidelines, no enamel bevels were placed or enamel etched, nor were other ways used to get extra mechanical retention. The materials were applied on the dentin lesions according to the manufacturer’s instructions ( Table 2 ). After cure of the adhesive, the lesions were in many cases filled with an oblique incremental layering technique there the first oblique layer was placed in the incisal/occlusal part of the lesion. Each layer was cured for 20–40 s using a well controlled light-curing device (Astralis 7, Vivadent, Schaan, Liechtenstein; Demetron light meter, Kerr, Orange, CA, USA). After polymerization, the restorations were finished with fine diamond burs (DZ, Berlin, Germany) and polishing stones under water spray (Brownie, Shofu Dental Co, Ratingen, Germany).

Evaluation

The restorations were evaluated at baseline, and then blindly at, 6, 12, 18 and 24 months and then yearly during the 5 years by the operator and at regular intervals by two calibrated evaluators (inter- and intra-examiner Cohen’s Kappa values of loss of retention criteria were >0.94). During evaluation, the dental assistant wrote the scores in the participants form. The evaluator(s) had no knowledge of the materials to be evaluated or earlier evaluation scores. Slightly modified USPHS criteria were used ( Table 3 ) . Postoperative sensitivity was registered by questioning the participants at the evaluation visits or by self-reporting in between the visits.

Table 3
Criteria for direct clinical evaluation with slightly modified USPHS criteria (van Dijken, 1986).
Category Score Criteria
Acceptable Unacceptable
Marginal adaptation 0 Restoration is contiguous with existing anatomic form, explorer does not catch
1 Explorer catches, no crevice is visible into which explorer will penetrate
2 Crevice at margin, enamel exposed
3 Obvious crevice at margin, dentin or base exposed
4 Restoration mobile, fractured partially or totally
Color match 0 Very good color match
1 Good color match
2 Slight mismatch in color, shade or translucency
3 Obvious mismatch, outside the normal range
4 Gross mismatch
Marginal discoloration 0 No discoloration evident
1 Slight staining, can be polished away
2 Obvious staining can not be polished away
3 Gross staining
Surface roughness 0 Smooth surface
1 Slightly rough or pitted
2 Rough, cannot be refinished
3 Surface deeply pitted, irregular grooves
Caries 0 No evidence of caries
1 Caries is evident contiguous with the margin of the restoration

Statistical analysis

The IBM SPSS (Statistical Package for the Social Sciences) statistics version 19 was used to process the data. The characteristics of the restorations were described by descriptive statistics using frequency distributions of the scores. Cumulative retention failures were calculated by dividing the number of lost restorations at the recalls by the total number evaluated at each of the recalls. Survival functions were given by descriptive statistics. Differences in loss of retention between the adhesives were tested with Friedman two-way analysis of variance test. The null hypothesis was rejected at 5% level.

Material and methods

During the period May 2006–October 2007, all patients attending the author’s PDHS clinic at the dental school Umeå, for who treatment of non-carious cervical lesions was indicated were requested to participate in the study. No patient was excluded because of caries activity, periodontal condition or parafunctional habits. All participants received informed consent and the study was approved by the commission for medical ethics of the University of Umeå. A total of 169 Class V restorations were placed in 67 patients, 34 men and 33 women with a mean age of 64.7 year (min–max 39–84), who needed treatment of non carious cervical lesions. All restorations were placed by one experienced operator, familiar with adhesive dentistry, in dentin lesions without any intentional enamel involvement. Pre-operatively, the lesions were categorized by the operator compared to lesion models in terms of depth (shallow, moderate, large) and size (small, moderate, large) of the lesion, the area of the dentin surface estimated as sclerotic tissue (0, <50%, >50%) ( Table 1 ) .

Table 1
Baseline data, distribution and lesion characteristics, of the lesions included.
G-Bond cfm XP Bond
Teeth
Incisor/cuspidate 25 16 23
Premolar 30 19 20
Molar 12 16 8
Jaw
Maxilla 34 40 37
Mandible 33 11 14
Lesion size
Small 11 7 18
Medium 23 33 19
Large 33 11 13
Lesion depth
Superfiscial 24 28 33
Medium 27 17 13
Deep 16 6 5
Degree of sclerosis
0% 19 25 26
<50% 6 8 10
>50% 42 18 15

A single-step, self-etching HEMA-free primer (G-Bond, GC Corp, Tokyo, Japan), a 3-step HEMA/TEGDMA free etch-and-rinse (cfm, Saremco AG, Rebstein, Switzerland) and a 2-step HEMA-containing etch-and-rinse adhesive (XP Bond, Dentsply/DeTrey, Konstanz, Germany) were evaluated in combination with two restorative resinous materials ( Table 2 ). The resin composite Gradia Direct (GC Corp) was used in combination with G-Bond, and els (extra low shrinkage; Saremco) in combination with the two other adhesives. After the operative procedure decision, the lesions were filled in randomly order by three adhesive systems. In subjects with two or more lesions, different adhesives were applied in the lesions to make intra-individual comparison possible.

Table 2
Composition and application methods of the adhesive systems tested.
Adhesive Composition Manufacturer Application
G-Bond 1-step SEA 4-MET, UDMA, TEGDMA, phosphoric acid monomer, photo-initiator, stabilizer, fumed silica filler, acetone, water pH = 2.0 GC Corp, Tokyo, Japan lot 0506141 Apply adhesive on the air dried dentin surface. Agitating for 5 s and reapply if necessary. Leave undisturbed for 10 s.
Dry strongly with air with maximum pressure for 5 s.
cfm adhesive system cmf etch : buffered phosphoric acid (pH = 1.5)
cmf primer : metacrylated phosphoric salt, alcohol, aceton, CQ, co-initiator
cmf bonding : hydrophilic ethoxylated Bis-GMA, silanized barium glass, CQ, co-initiator.
Saremco AG, Rebstein, Switzerland
primer lot 06.2011.01
bonding lot 06.2011.05
Etch for 15 s enamel and dentin
Rinse for 30 s
Air dry for 5 s
Apply cmf primer using a rubbing motion for 30 s, dry for 5 s and light cure for 20 s
Apply cmf bonding using a rubbing motion for 20 s
Light cure for 30 s
XP Bond 2-step etch-and-rinse Conditioner: 36% phosphoric acid: primer: TCB, PENTA, UDMA, TEGDMA, HEMA, butylated benzenediol (stabilizer), ethyl-4-dimethylaminobenzoate, CQ, amorphous silica, tertiary butanol DeTrey Dentsply, Konstanz, Germany lot 0701000 Apply conditioner to the lesion surface for 15 s
Rinse thoroughly for 10 s and dry but do not desiccate
Apply adhesive and leave undisturbed for 20 s
Air blow for min 5 s.
Light cure for 20 s.
els (extra low shrinkage) resin composite Bis-GMA, Bis-EMA, silanized barium glass, catalysts, inhibitors, pigment Saremco AG, Rebstein, Switzerland
lot 10.2010-006
Gradia Direct resin composite GC Corp, Tokyo, Japan
lot 121222
Abbreviations : HEMA, 4-MET 4-methacryloxyethyl trimetellitic acid; PENTA, phosphoric acid modified acrylate resin; TCB, resin carboxylic acid modified dimethacrylate; TEGDMA, triethyleneglycol dimethacrylate; Bis GMA, bisphenol A-glycidyl methacrylate; Bis EMA, Bisphenol A ethoxylate dimethacrylate; UDMA, urethane dimethacrylate; CQ, camphorguinone.

Operative procedure

After randomization, the lesions were slightly roughened by a diamond bur before application of the adhesive systems to create a surface smear layer. The operative field was isolated with cotton rolls and a saliva suction device. The adjacent gingiva was retracted by gingival retraction instruments when necessary to secure unrestricted contamination free access to the field. In order not to enlarge the retention area, according to the ADA guidelines, no enamel bevels were placed or enamel etched, nor were other ways used to get extra mechanical retention. The materials were applied on the dentin lesions according to the manufacturer’s instructions ( Table 2 ). After cure of the adhesive, the lesions were in many cases filled with an oblique incremental layering technique there the first oblique layer was placed in the incisal/occlusal part of the lesion. Each layer was cured for 20–40 s using a well controlled light-curing device (Astralis 7, Vivadent, Schaan, Liechtenstein; Demetron light meter, Kerr, Orange, CA, USA). After polymerization, the restorations were finished with fine diamond burs (DZ, Berlin, Germany) and polishing stones under water spray (Brownie, Shofu Dental Co, Ratingen, Germany).

Evaluation

The restorations were evaluated at baseline, and then blindly at, 6, 12, 18 and 24 months and then yearly during the 5 years by the operator and at regular intervals by two calibrated evaluators (inter- and intra-examiner Cohen’s Kappa values of loss of retention criteria were >0.94). During evaluation, the dental assistant wrote the scores in the participants form. The evaluator(s) had no knowledge of the materials to be evaluated or earlier evaluation scores. Slightly modified USPHS criteria were used ( Table 3 ) . Postoperative sensitivity was registered by questioning the participants at the evaluation visits or by self-reporting in between the visits.

Table 3
Criteria for direct clinical evaluation with slightly modified USPHS criteria (van Dijken, 1986).
Category Score Criteria
Acceptable Unacceptable
Marginal adaptation 0 Restoration is contiguous with existing anatomic form, explorer does not catch
1 Explorer catches, no crevice is visible into which explorer will penetrate
2 Crevice at margin, enamel exposed
3 Obvious crevice at margin, dentin or base exposed
4 Restoration mobile, fractured partially or totally
Color match 0 Very good color match
1 Good color match
2 Slight mismatch in color, shade or translucency
3 Obvious mismatch, outside the normal range
4 Gross mismatch
Marginal discoloration 0 No discoloration evident
1 Slight staining, can be polished away
2 Obvious staining can not be polished away
3 Gross staining
Surface roughness 0 Smooth surface
1 Slightly rough or pitted
2 Rough, cannot be refinished
3 Surface deeply pitted, irregular grooves
Caries 0 No evidence of caries
1 Caries is evident contiguous with the margin of the restoration
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Nov 25, 2017 | Posted by in Dental Materials | Comments Off on A randomized controlled 5-year prospective study of two HEMA-free adhesives, a 1-step self etching and a 3-step etch-and-rinse, in non-carious cervical lesions
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