A 6-year prospective evaluation of a one-step HEMA-free self-etching adhesive in Class II restorations

Abstract

Objective

The aim of this study was to evaluate the clinical effectiveness of a one-step HEMA-free self-etching adhesive (SEA) placed with a micro-fine hybrid resin composite in Class II restorations. The restorations were compared intraindividually with 2-step HEMA containing SEA-giomer restorations.

Material and methods

Fifty-four patients with at least one pair of two similar Class II cavities participated (30 men, 24 women; mean age 57.1 yrs). A total of 115 Class II composite restorations were placed with (1) a one step HEMA-free adhesive and a micro-fine hybrid resin composite (Gbond/Gradia Direct: 60; GG) and (2) a 2-step HEMA-containing SEA and a giomer (FL Bond/Beautifil: 55; FB). Each participant received in a randomized way at least one restoration with each of the experimental materials. The restorations were evaluated at baseline and yearly during a 6 year followup using modified USPHS criteria.

Results

During the 6 years, 111 restorations could be evaluated. No post-operative sensitivity was reported by the participants. Fourteen failed restorations (12.6%) were observed during the follow up, 5 GG (8.5%; 4 premolar and 1 molar teeth) and 9 FB (17.7%; 1 premolar and 8 molar teeth) ( p < 0.05). Annual failure rate at 6 years were 1.4% for GB and 3.0% for FB. Main reasons of failure were bulk fracture of resin composite for FB and tooth fracture for GB.

Significance

The HEMA-free SEA-hybrid RC restorations showed good clinical durability in Class II cavities after 6 years. The HEMA-containing SEA-giomer restorations showed a rather high failure frequency.

Introduction

Self-etching adhesives (SEA) are supposed to make the bonding procedure more user-friendly, eliminating the risk of over-etching and over-drying. However, the hybrid layer of the SEA is much thinner compared to the traditional etch-and-rinse systems. HEMA (2-hydroxyethyl methacrylate), an effective hydrophilic methacrylate primer monomer, is frequently present in dental adhesives. HEMA improves immediate dentin bond strength due to its wetting enhancement effect and promotes diffusion of co-monomers by expanding the demineralised collagen . The main drawbacks related to the use of the low weight monomer HEMA are its allergenic potential and hydrolytic deteriorating in the humid oral environment . High HEMA content promotes water uptake and subsequent gradual hydrolytic degradation of the polymers, swelling and staining . In 1-step SEA adhesives HEMA keep the resin monomers and water in one solution and prevent phase separation . Increased water uptake might accelerate the reduction of mechanical properties of the SEA . In deep cavities, HEMA may diffuse rapidly through dentin at cytotoxic concentrations, promoting an induction of pulp apoptotic cell death, resulting in hypersensitivity reactions in patients . Due to the disadvantages of HEMA, HEMA-free less hydrophilic adhesives have been introduced which may show reduced water sorption, higher stability of mechanical properties, stability of the interfacial bond, improvement in bonding durability and reduced allergenic potential . Omission of HEMA in adhesives may lead to phase separation between water and the adhesive monomers, and strongly air blowing to remove the water-containing droplets from the interface is therefore required . Giomers is a novel class of fluoride releasing anhydrous hybrid resin-based restorative materials which use pre-reacted glass-ionomer technology . The fillers are produced from siliceous hydrogels, which are formed after the reaction of ion-leachable glasses with polyalkenoic acid. The gels are freeze dried, milled and silanized. The unreacted fluoro-aluminosilicate glass, silica particles and fumed silica are added to a matrix of urethane dimethacrylate. After water uptake of the restorative, an acid–base reaction of the pre-reacted glass ionomer can take place promoting fluoride release . In this way, the material may inhibit demineralization and enhance remineralization. The long-term fluoride release is unknown. The clinical evidence for the material is scarce. The aim of this study was to investigate the clinical longevity of class II restorations performed with a HEMA-free 1-step SEA adhesive in combination with a micro-fine hybrid resin composite. The restorations were compared intraindividually with Class II HEMA-containing 2-step SEA – giomer restorations. The null hypothesis tested was that there is no difference in durability between the two resin composite restoration systems.

Material and methods

Experimental design

During november 2005-november 2007, adult patients attending the Dental School clinic in Umeå, who needed 2 or more similar sized Class II restorations, in order to make an intraindividual comparison possible, were asked to participate in the follow up. Female patients who were pregnant or nursing were excluded. No patient was excluded because of oral hygiene, caries activity, periodontal condition or parafunctional habits. All patients were informed on the background of the study, which was approved by the ethics committee of the University of Umeå. Reasons for placement of the resin composite restorations were primary or secondary carious lesions, fracture of old amalgam fillings or replacement because of esthetic or other reasons. Fifty-four patients participated, 30 men and 24 women, with a mean age of 57.1 yrs (range 24–77). One hundred-fifteen restorations were placed in 41 premolar and 74 molar teeth. All teeth had opposing and adjacent tooth contacts. The distribution and the size of the restorations are given in Table 1 . Before the operative procedure started, the cavities within each participant were randomized to the test systems. Cavities within each individual pair were restored with either the HEMA-free 1-step SEA adhesive G-Bond and the hybrid resin composite Gradia Direct posterior (GC, Tokyo, Japan; n = 60; GG) or the HEMA-containing 2-step SEA adhesive FL-Bond adhesive and the giomer resin composite Beautifil (Shofu, Kyoto, Japan; n = 55; FB) ( Table 2 ). In individuals with an uneven number of cavities, the cavity not belonging to a pair was restored with the one step SEA. Operative procedures were performed by one operator experienced with adhesive dentistry and familiar with the tested materials. Local anesthesia was used if necessary. Existing restorations and/or caries were removed under constant water cooling. No calcium hydroxide base material was placed and no bevels were prepared. The operative field was carefully isolated with cotton rolls and suction device. For all Class II cavities a thin metallic matrix was used and carefully wedging was performed with wooden wedges (Kerr/Hawe Neos, Switzerland). The cavities were cleaned by a thoroughfull rinsing with water. Application of the primers was done according to the manufacturer’s instructions ( Table 2 ). The resin composite was then applied in layers of maximally 2–3 mm with, if possible, an oblique layering technique using selected composite instruments (Hu Friedy). Every increment was light cured with a well controlled LED light-unit (Smart lite, Dentsply/DeTrey, Konstanz, Germany) for 30–40 s. After checking the occlusion/articulation and contouring with finishing diamond burs, the final polishing was performed with the Shofu polishing system (brownie) and finishing strips (GC).

Table 1
Distribution of the experimental restorations.
Surfaces Mandibula Maxilla
Premolars Molars Premolars Molars
2 Surfaces 9 19 17 31
3 Surfaces 6 8 1 9
>3 Surfaces 3 8 4
Total 15 30 26 44

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. Light cure for 10 s
FL Bond 2-step SEA FL Primer A : distilled water, acetone, initiators FL Primer B : 2-HEMA, 4-AET, 4-AETA, UDMA, TEGDMA, acetone, initiators, stabilizers, pigment. FL Bond :Distilled water, 2-HEMA, 4-AET, 4-AETA, urethane-triacrylate, TEGDMA, urethane dimethacrylate, pre-reacted glass-ionomer filler, DL-camphorquinone, initiators Shofu, Kyoto, Japan primer lot A 04383 lot B 040301 bonding lot 040301 Primer: apply for 20 s, 10 s gently air drying Light cure for 10 s. Bonding: apply and light cure
Gradia direct micro-fine hybrid resin composite UDMA and dimethacrylate monomers, silica (13 vol%), prepolymerized filler (28 vol%), silanated fluor-alumino silicate glass (24 vol%), camphorquinone. Modulus of elasticity 7 GPa Fracture toughness 1.6 MPa a GC Corp, Tokyo, Japan lot 121222 2–3 mm layers light cured 40 s
Beautifil giomer resin composite Bis-GMA, TEGDMA Filler loading 66.3 vol%: 50% silanized fluoboro-alumino silicate glass and 50% multifunctional glass pre-reacted on the surface presenting a stable glass ionomer phase (S-PRG), catalysts, inhibitors, pigment. Modulus of elasticity: 8.5 GPa a Shofu, Kyoto, Japan
lot 11032654
2–3 mm layers light cured 40 s
Abbreviations : HEMA, 2-hydroxyethyl methacrylate; 4-MET, 4-methacryloxyethyl trimetellitic acid; TEGDMA, triethyleneglycol dimethacrylate; 4-AET, 4-acryloxyethyltrimellitec acid; 4-AETA, 4-acryloxyethyltrimellitate anhydride; UDMA, urethane-dimethacrylate; CQ, camphorguinone; Bis GMA, bisphenol A glycidyl dimethacrylate.

a Information of the respective manufacturers technical files.

Evaluation

Each restoration was evaluated according to slightly modified USPHS criteria for the following characteristics: anatomical form, marginal adaptation, color match, marginal discoloration, surface roughness, caries ( Table 3 ) . The restorations were evaluated at baseline, and then blindly every year during 6 years by the operator and at regular intervals (30–40% of the evaluation days) by other calibrated evaluators. Bite-wing radiographs were taken of all restorations according to guidelines used at our clinic based on the individuals’ caries risk, in most cases once a year or every second year. The caries risk for each patient at baseline was estimated by the treating clinician by means of clinical and socio-demographic information routinely available at the annual clinical examinations, e.g. incipient caries lesions and former caries history . Bruxing activity was estimated as low or high by the treating clinician by means of clinical signs and history at the annual examinations. Any failures during the clinical study were counted as failures during all subsequent recalls. The failure percentage at each recall was the total number of failures to date in the following equation: Failure percentage = (previous failures + new failures)/(previous failures + currently recalled restorations) × 100.

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 evaluation

The evaluated characteristics of the restorations, including the number of not-acceptable restorations (failures) are described by descriptive statistics by using frequency distributions of the scores. The overall performance of the experimental restorations was tested after intra-individual comparison and ranking using the Friedman’s two-way analysis of variance test . Patients with restorations, not belonging to a pair were included in the descriptive statistics of the scores for the resin composite, but not in the analysis of the intraindividual comparison of the two adhesives. The hypothesis was rejected at the 5% level.

Material and methods

Experimental design

During november 2005-november 2007, adult patients attending the Dental School clinic in Umeå, who needed 2 or more similar sized Class II restorations, in order to make an intraindividual comparison possible, were asked to participate in the follow up. Female patients who were pregnant or nursing were excluded. No patient was excluded because of oral hygiene, caries activity, periodontal condition or parafunctional habits. All patients were informed on the background of the study, which was approved by the ethics committee of the University of Umeå. Reasons for placement of the resin composite restorations were primary or secondary carious lesions, fracture of old amalgam fillings or replacement because of esthetic or other reasons. Fifty-four patients participated, 30 men and 24 women, with a mean age of 57.1 yrs (range 24–77). One hundred-fifteen restorations were placed in 41 premolar and 74 molar teeth. All teeth had opposing and adjacent tooth contacts. The distribution and the size of the restorations are given in Table 1 . Before the operative procedure started, the cavities within each participant were randomized to the test systems. Cavities within each individual pair were restored with either the HEMA-free 1-step SEA adhesive G-Bond and the hybrid resin composite Gradia Direct posterior (GC, Tokyo, Japan; n = 60; GG) or the HEMA-containing 2-step SEA adhesive FL-Bond adhesive and the giomer resin composite Beautifil (Shofu, Kyoto, Japan; n = 55; FB) ( Table 2 ). In individuals with an uneven number of cavities, the cavity not belonging to a pair was restored with the one step SEA. Operative procedures were performed by one operator experienced with adhesive dentistry and familiar with the tested materials. Local anesthesia was used if necessary. Existing restorations and/or caries were removed under constant water cooling. No calcium hydroxide base material was placed and no bevels were prepared. The operative field was carefully isolated with cotton rolls and suction device. For all Class II cavities a thin metallic matrix was used and carefully wedging was performed with wooden wedges (Kerr/Hawe Neos, Switzerland). The cavities were cleaned by a thoroughfull rinsing with water. Application of the primers was done according to the manufacturer’s instructions ( Table 2 ). The resin composite was then applied in layers of maximally 2–3 mm with, if possible, an oblique layering technique using selected composite instruments (Hu Friedy). Every increment was light cured with a well controlled LED light-unit (Smart lite, Dentsply/DeTrey, Konstanz, Germany) for 30–40 s. After checking the occlusion/articulation and contouring with finishing diamond burs, the final polishing was performed with the Shofu polishing system (brownie) and finishing strips (GC).

Table 1
Distribution of the experimental restorations.
Surfaces Mandibula Maxilla
Premolars Molars Premolars Molars
2 Surfaces 9 19 17 31
3 Surfaces 6 8 1 9
>3 Surfaces 3 8 4
Total 15 30 26 44

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. Light cure for 10 s
FL Bond 2-step SEA FL Primer A : distilled water, acetone, initiators FL Primer B : 2-HEMA, 4-AET, 4-AETA, UDMA, TEGDMA, acetone, initiators, stabilizers, pigment. FL Bond :Distilled water, 2-HEMA, 4-AET, 4-AETA, urethane-triacrylate, TEGDMA, urethane dimethacrylate, pre-reacted glass-ionomer filler, DL-camphorquinone, initiators Shofu, Kyoto, Japan primer lot A 04383 lot B 040301 bonding lot 040301 Primer: apply for 20 s, 10 s gently air drying Light cure for 10 s. Bonding: apply and light cure
Gradia direct micro-fine hybrid resin composite UDMA and dimethacrylate monomers, silica (13 vol%), prepolymerized filler (28 vol%), silanated fluor-alumino silicate glass (24 vol%), camphorquinone. Modulus of elasticity 7 GPa Fracture toughness 1.6 MPa a GC Corp, Tokyo, Japan lot 121222 2–3 mm layers light cured 40 s
Beautifil giomer resin composite Bis-GMA, TEGDMA Filler loading 66.3 vol%: 50% silanized fluoboro-alumino silicate glass and 50% multifunctional glass pre-reacted on the surface presenting a stable glass ionomer phase (S-PRG), catalysts, inhibitors, pigment. Modulus of elasticity: 8.5 GPa a Shofu, Kyoto, Japan
lot 11032654
2–3 mm layers light cured 40 s
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Nov 25, 2017 | Posted by in Dental Materials | Comments Off on A 6-year prospective evaluation of a one-step HEMA-free self-etching adhesive in Class II restorations
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