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The Effect of Dentine Pre-Treatment Using Bioglass And/Or Polyacrylic

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The Effect of Dentine Pre-Treatment Using Bioglass And/Or Polyacrylic Journal of Dentistry 73 (2018) 32–39 Contents lists available at ScienceDirect Journal of Dentistry journal homepage: www.elsevier.com/locate/jdent The effect of dentine pre-treatment using bioglass and/or polyacrylic acid on T the interfacial characteristics of resin-modified glass ionomer cements ⁎ Salvatore Sauroa,b, , Timothy Watsonb, Agustin Pascual Moscardóc, Arlinda Luzia, Victor Pinheiro Feitosad, Avijit Banerjeeb,e a Dental Biomaterials, Preventive & Minimally Invasive Dentistry, Departamento de Odontologia, CEU Carndenal Herrera University, Valencia, Spain b Tissue Engineering and Biophotonics Research Division, King’s College London Dental Institute, King’s College London, United Kingdom c Departamento de Odontologia, Universitat de Valencia, Valencia, Spain d Paulo Picanço School of Dentistry, Fortaleza, Ceará, Brazil e Department of Conservative & MI Dentistry, King’s College London Dental Institute, King’s College London, United Kingdom ARTICLE INFO ABSTRACT Keywords: Objective: To evaluate the effect of load-cycle aging and/or 6 months artificial saliva (AS) storage on bond Air-abrasion durability and interfacial ultramorphology of resin-modified glass ionomer cement (RMGIC) applied onto den- Bioactive glass tine air-abraded using Bioglass 45S5 (BAG) with/without polyacrylic acid (PAA) conditioning. Bonding Methods: RMGIC (Ionolux, VOCO) was applied onto human dentine specimens prepared with silicon-carbide Dentine pre-treatment abrasive paper or air-abraded with BAG with or without the use of PAA conditioning. Half of bonded-teeth were Polyacrylic acid submitted to load cycling (150,000 cycles) and half immersed in deionised water for 24 h. They were cut into Resin-modified glass ionomer cements matchsticks and submitted immediately to microtensile bond strength (μTBS) testing or 6 months in AS im- mersion and subsequently μTBS tested. Results were analysed statistically by two-way ANOVA and Student–Newman–Keuls test (α = 0.05). Fractographic analysis was performed using FE-SEM, while further RMGIC-bonded specimens were surveyed for interfacial ultramorphology characterisation (dye-assisted nano- leakage) using confocal microscopy. Results: RMGIC applied onto dentine air-abraded with BAG regardless PAA showed no significant μTBS reduc- tion after 6 months of AS storage and/or load cycling (p > 0.05). RMGIC–dentine interface showed no sign of degradation/nanoleakage after both aging regimens. Conversely, interfaces created in PAA-conditioned SiC- abraded specimens showed significant reduction in μTBS (p < 0.05) after 6 months of storage and/or load cycling with evident porosities within bonding interface. Conclusions: Dentine pre-treatment using BAG air-abrasion might be a suitable strategy to enhance the bonding performance and durability of RMGIC applied to dentine. The use of PAA conditioner in smear layer-covered dentine may increase the risk of degradation at the bonding interface. Clinical significance: A combined dentine pre-treatment using bioglass followed by PAA may increase the bond strength and maintain it stable over time. Conversely, the use of PAA conditioning alone may offer no significant contribute to the immediate and prolonged bonding performance. 1. Introduction of powders used may affect the quality and durability of the tooth-re- storation interface [6,7]. Bioglass 45S5 (BAG), a calcium/sodium Conventional rotary instruments equipped with tungsten-carbide, phosphate-phyllosilicate glass, is used in air-abrasion with several ad- carbon-steel or diamond burs are used routinely in clinical practice for vantages including the absence of pain during the operative procedure dental cavity preparation. In minimally invasive dentistry (MID), the and the opportunity to leave cavities with rounded internal line angles, underlying tenet is to preserve sound dental hard tissues and minimise thus minimising the contraction stress of resin composites [8–10]. the unnecessary alteration of healthy tooth structure [1–5]. Air-abra- Moreover, BAG will embed into the dentine surface so creating a sion has been advocated to be a suitable approach to reduce the risk for bioactive smear layer [5,6,11] that can react with body fluids, en- unnecessary removal of sound dental tissues [2,4], although the choice couraging mineral deposition through formation of hydroxyapatite ⁎ Corresponding author at: Dental Biomaterials, Preventive and Minimally Invasive Dentistry, Departamento de Odontología, Facultad de Ciencias de la Salud, Universidad CEU- Cardenal Herrera, C/Del Pozo s/n, Alfara del Patriarca 46115, Valencia, Spain. E-mail address: [email protected] (S. Sauro). https://doi.org/10.1016/j.jdent.2018.03.014 Received 28 February 2018; Received in revised form 25 March 2018; Accepted 29 March 2018 0300-5712/ © 2018 Elsevier Ltd. All rights reserved. S. Sauro et al. Journal of Dentistry 73 (2018) 32–39 [Ca10(PO4)6(OH)2][2–16]. Table 1 The stabilisation of the interface between tooth and restorative Experimental design and number of teeth/specimen used in each experimental material, as well as the creation of in loco conditions that might protect group. and/or repair the retained demineralised dental hard tissues are of Subgroups: [number of specimens for MTBS/ particular importance in MID [16–18]. The use of fluoride-releasing Confocal/FE-SEM] restorative materials such as glass ionomer cements (GIC) or resin- modified glass ionomer cements (RMGIC) may contribute to interfacial Main groups Dentine CTR: LC: Load AS: 6- AS + LC: Load ff fl [8 teeth each] etching 24 h cycling in month in cycling + 6- protection because of their bu ering ability and their uoride ion re- (10% PAA AS AS AS month in AS lease/re-charge [19–21]. Moreover, since GIC-based materials have the gel)* aptitude to induce crystal growth [22] within the interface of the re- storation after long-term storage in water, with a chemical composition SiC paper NO [8/8/ [8/8/5] [8/8/5] [8/8/5] 5] similar to that of dental hard tissues [23,24], it is hypothesised that the SiC paper YES [8/8/ [8/8/5] [8/8/5] [8/8/5] combination of dentine pre-treatment with BAG air-abrasion and sub- 5] sequent restoration using GIC-based materials could be a suitable Air-abrasion NO [8/8/ [8/8/5] [8/8/5] [8/8/5] strategy to achieve longer-lasting bonding interfaces that can resist BAG 5] degradation over time. Air-abrasion YES [8/8/ [8/8/5] [8/8/5] [8/8/5] BAG 5] RMGICs combine the therapeutic properties of GICs with the me- chanical properties of resin polymers [25]. The setting process of RMGIC is based on free-radical polymerisation as well as the acid–base The roots were removed 1 mm beneath the cemento–enamel junction reaction between polyalkenoic acids and fluoroaluminosilicate glass (CEJ) using a diamond-embedded blade (high concentration XL 12205; [26–28]. The self-adhesive mechanism of GIC-based materials to den- Benetec, London, UK) mounted on a hard-tissue microtome (Remet tine is the micromechanical interlocking achieved by shallow hy- evolution, REMET, Casalecchio di Reno, Italy). A subsequent parallel bridisation of the micro-porous collagen network. There is a chemical cut was performed to remove the occlusal enamel and expose mid- reaction that occurs through the formation of ionic bonds between the coronal dentine. This flat dentine surface was polished with silicon- carboxyl groups of the polyalkenoic acids and calcium of hydro- carbide paper (SiC #320-grit) for 1 min under continuous water irri- xyapatite-coated collagen fibrils [29,30]. Polyacrylic acid (PAA) is the gation to simulate the creation of a smear layer that would be created most common conditioner used in enamel/dentine pre-treatment to clinically after rotary dentine preparation. The specimens were divided remove the smear layer prior to the application of GIC-based restorative into experimental groups and subgroups as shown in Table 1. materials onto dentine and enamel. However, concerns exist regarding its use, application times and concentrations as these factors may in- terfere with the overall bonding performance. Indeed, a high number of 2.2. Experimental design: dentine pre-treatments and aging protocols adhesive failures between a RMGIC and resin composite have been reported when a polyalkenoic conditioner was used on smear-layer The experimental design required that half of the dentine specimens covered dentine [30]. were air-abraded with BAG (Sylc, VELOPEX International, London, UK) Milly et al., [31] used a combination of PAA-BAG powder in air- under water irrigation. An Aquacare air-abrasion unit (VELOPEX abrasion as a pre-treatment of white spot lesions in enamel (WSL). It International) was used with an air pressure of 4 bar (400 MPa) for was showed that surface pre-conditioning was able to enhance the re- 1 min at a distance of 1 cm from the dentine surface and with con- mineralisation of WSL. Indeed, there were reported increased mineral tinuous mesio-distal and bucco-lingual movements. Subsequently, the content, improved mechanical properties and alterations in the enamel air-abraded dentine surface were conditioned with 10% PAA gel (GC ultrastructure. To the present authors’ knowledge, there are no previous Fuji conditioner, Newport Pagnell, UK) for 20 s and rinsed with water published studies assessing the effect of dentine pre-treatments using for 20 s, or left unconditioned. BAG air-abrasion and/or by PAA conditioning on the interfacial char- Overall, four primary groups (n = 32 specimens/group) were cre- acteristics of resin-modified glass ionomer cements submitted to dif- ated for this experimental design based on the preparation of the den- ferent aging regimes. tine substrate: The aim of this study was to test the microtensile bond strength Group 1. Specimens abraded using 320-grit SiC abrasive paper (MTBS), after load-cycle aging and/or 6 months storage in artificial (1 min) under continuous irrigation, followed by a water rinse (20 s), saliva (AS), of RMGIC applied to dentine air-abraded using Bioglass air-drying (2 s) and restored with a light-cured RMGIC (no PAA con- 45S5 (BAG) with or without subsequent surface pre-conditioning using ditioning).
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