Stability of the Adhesive Interface after Different Artificial Aging Techniques

Case Report

J Dent App. 2015;2(2): 153-157.

Stability of the Adhesive Interface after Different Artificial Aging Techniques

Souza LC1, Apolonio FM1, Souza LP2, Carrilho MRO3 and Saboia VPA4*

1Post Graduate Program of Dentistry - Faculty of Pharmacy, Dentistry and Nursing, Federal University of Ceará, Fortaleza, Ceará, Brazil

2Department of Biology, São Paulo State University “Julio Mesquita” (UNESP), Rio Claro, São Paulo, Brazil

3Department of Oral Biology, School of Dentistry, Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada

4Department of Operative Dentistry, Federal University of Ceará, Fortaleza, Ceará, Brazil

*Corresponding author: Saboia Vpa, Department of Operative Dentistry, Federal University of Ceará, Fortaleza, Ceará, Brazil, Rua Gilberto Studart, 770 AP. 901, Bairro: CocÓ - CEP: 60.190-750

Received: September 20, 2014; Accepted: January 18, 2015; Published: January 20, 2015


This study evaluated the stability of resin-bonded dentin interfaces using a two-step etch-and-rinse adhesive submitted to different artificial aging methods. Thirty human molars had the occlusal middle-dentin exposed and treated with Adper Single Bond 2 system, as recommended by manufacturer. Resin composite buildups were incrementally placed on bonded dentin. Specimens for micro tensile test were obtained according to the “non-trimming” technique and tested in tension, at 0.5 mm/minute, after one of the storage conditions: G1) water for 24 h (control group), G2) 10% NaOCl for 1 h, G3) continuous thermocycling (60,000 cycles at 5°-55°C for 3 months), G4) water for three months, G5) intermittent thermocycling (10,000 cycles/month at 5°- 55°C for 6 months) and G6) water for six months. Results showed that all tested methods induced a significant decrease in bond strength to dentin when compared with that observed for the control group (p<0.05). The highest decrease in bond strength values were observed for groups G2 and G3. Storage in 10% NaOCl and continuous thermocycling were the most aggressive methods to reduce the micro tensile bond strength to bonded dentin.

Keywords: Adhesives; Dentin; Sodium hypochlorite


Perfect dentinal sealing is an elementary goal to be achieved in adhesive restorations [1]. In daily situations, restorative materials and dental restorations are commonly challenged by chemical (i.e. water, acids and enzymes) and physical/mechanic agents (i.e. changes in temperature and pH, chewing loads), which in conjunction end up accelerating the degradation of restorative materials and contributing with the disruption of dental restorations at short-term [2,3].

While not definitive, laboratorial research is fundamental to predict the complex clinical conditions that take part in the oral environment and compromise the durability of adhesive dental restorations. In this sense, in vitro aging of adhesive restorations may help one to understand the mechanisms involved in their degradation and also to find clinical and technical solutions to postpone this occurrence [4].

Storage in water has been the in vitro technique most commonly used to age adhesive restorations since the presence of water makes part, directly or indirectly, of all degrading reactions in the oral cavity [5,6]. In most of studies, the period of sample immersion may vary from few months [7-9] to some years [2,10] at the temperature of 37°C.

The aging by samples thermo cycling is commonly used to simulate the thermal changes that occur in the oral environment caused by consumption of food and drinks and even by breathing [11]. The specimens are submitted to a thermal variation that is normally driven by immersion into water baths at different temperatures [3].

Another method has been suggested to assess durability of resinbonded specimens and it consists in exposing the adhesive interface to an aqueous sodium hypochlorite solution [4]. According to Saboia et al. [12] this is a rapid and effective method of aging, which apart from challenging resinous components of resin-dentin bonds, it can also promote the degradation of dentin matrix components that have not been eventually well-impregnated by the adhesive system after dentin demineralization, a condition that seems to be more clinically realistic.

Despite promising, this chemical aging of bonds has not been sufficiently evaluated and compared with other in vitro aging methods. Thus, the present study was performed to evaluate the stability of resin-dentin bonds created by a two-step etch-and-rinse adhesive system to human dentin after different artificial aging techniques. It was hypothesized that different methods to promote in vitro aging do not differ in their ability to the bond strength of resin-bonded dentin specimens.


Thirty freshly extracted human non-carious third molars were used in this study after obtaining the patients informed consent for their use, under a protocol approved by Federal University of Ceará (Brazil), n° 142/09. The teeth were stored in 0.01% thymol solution at 4°C for no more than 1 month. The occlusal surfaces were ground flat using 80- and 400-grit silicon carbide (SiC) to expose the deep dentin and 600-grift SiC to standardize the smear layer. Specimens were etched with 37% phosphoric acid gel for 15 s (Condac/FGM, Joinvile, Brazil), rinsed with water and dried with absorbent paper.

Single Bond 2 (3M-ESPE, St. Paul, USA) was applied in accordance with the manufacturer’s instructions (Table 1), and each bonded specimen was light-cured for 10 s using a light-curing unit (Gnatus Optilight LD Max, Ribeirão Preto, Brazil) delivering at 460mW/cm [2]. Increments of 6 mm-thick resin composite build ups (Z100, 3M-ESPE, St. Paul, USA) were placed on dentin-hybridized surfaces in increments of 2 mm that were individually light cured for 40s.