Bond Strength of 5(th), 6(th) and 7(th) Generation Bonding Agents to Intracanal Dentin of Primary Teeth.

Original Article Bond Strength of 5th, 6th and 7th Generation Bonding Agents to Intracanal Dentin of Primary Teeth Hossein Afshar1, Yahya Baradaran Nakhjavani1, Sedighe Rahro Taban2, Zahra Baniameri3, Azam Nahvi4 1. 2. 3. 4. 1 Associate Professor, Dental Research Center Dentistry Research Institute, Department of Pediatric, Faculty of Dentistry, Tehran University of Medical Sciences, Tehran, Iran 2 Associate Professor, Department of Oral and Maxillofacial Pathology, Faculty of Dentistry, Tehran University of Medical Sciences, Tehran, Iran 3 Assistant Professor, Department of Pediatric, Faculty of Dentistry, Golestan University of Medical Sciences, Golestan, Iran 4 Associate Professor, Department of Pediatric, Faculty of Dentistry, Mazandaran University of Medical Sciences, Sari, Iran  Corresponding author: A. Nahvi, Department. of Pediatric, Faculty of Dentistry, Mazandaran University of Medical Sciences, Sari, Iran Received: 22 August 2014 Accepted: 16 December 2014 Abstract Objectives: This in-vitro study sought to assess the push-out bond strength of a total etch and 2 self-etch bonding systems to intracanal dentin of primary anterior teeth (PAT). Materials and Methods: Thirty-six primary anterior teeth were randomly divided into 3 groups of 5th generation (Single Bond 2), 6th generation (Clearfil SE) and 7th generation (Single Bond Universal) bonding agents. The canal orifice was restored with composite resin and the push-out test was carried out to assess the bond strength. After applying the push-out load, specimens were evaluated under a light microscope at 40X magnification. One-way ANOVA and log-rank test on Kaplan-Meier curves were applied for the comparison of bond strength among the 3 groups. Results: The mean± standard deviation (SD) bond strength was 13.6±5.33 MPa for Single Bond 2, 13.85±5.86 MPa for Clearfil SE and 12.28±5.24 MPa for Single Bond Universal. The differences in bond strength among the 3 groups were not statistically significant (P>0.05). Conclusion: All three bonding agents are recommended for use with composite posts in PAT. However, due to high technical sensitivity of the Total Etch system, single or two-step self etch systems may be preferred for uncooperative children. Key words: Bonding agents; Bond strength; Primary teeth Journal of Dentistry, Tehran University of Medical Sciences, Tehran, Iran (2015; Vol. 12, No. 2) INTRODUCTION Early childhood caries are common in children and quickly lead to the loss of tooth structure in primary maxillary anterior teeth. Removal of carious tissue in these teeth renders pulp treatments inevitable and due to the lack of sufficient enamel, retention must be gained from the coronal 3 mm of the canal to restore the tooth crown [1]. The same protocol is applied and followed for dentin bonding in perwww.jdt.tums.ac.ir February 2015; Vol. 12, No. 2 manent and primary teeth [2]. However, invitro studies have reported controversial results regarding the bond strength of adhesive systems to primary compared to permanent dentin. Different characteristics of primary dentin may be responsible for the conflicting results reported in the literature [2, 3]. Greater thickness of peritubular dentin with higher percentage of mineralization and larger diameter of dentinal tubules in primary teeth [2] sig901 Journal of Dentistry, Tehran University of Medical Sciences nificantly decrease the amount of solid dentin available for bonding compared to that in permanent teeth [2- 4]. On the other hand, different techniques have been used for the reconstruction of severely damaged primary anterior teeth; composite resin posts are most commonly used for this purpose [5]. Increased demand for esthetic restorations in dentistry has led to the development of different systems to enable adequate bonding to enamel and dentin with fewer steps [6]. Available dentin adhesives include 3-step, 2-step and one-step adhesives depending on the method of incorporation of the three main constituents of etching, priming and bonding [7]. Many researchers have attempted to improve the efficacy of dentin bonding agents. Now that adhesives have reached an acceptable level of bond strength, attempts have focused on reducing the application steps since the use of multi-step agents in children is difficult and time-consuming. Simultaneous enamel and dentin etching systems by using 2-step 5th generation bonding agents have shown favorable clinical efficacy. A recent revolutionary advancement in dentin bonding agents is the use of acidic adhesives enabling simultaneous application of acid, primer and bonding agent all together in 6th and 7th generation bonding systems [8]. Aside from the easy steps, the mechanism of action of 6th and 7th generation bonding agents is surface demineralization of dentin and simultaneous penetration of monomers into the resultant porosities [9]. Onestep systems simplify and shorten the process of bonding and are beneficial for use in uncooperative children [3]. Considering the fact that intracanal dentin has significant structural differences with coronal dentin in terms of the number and diameter of dentinal tubules and the amount of peritubular dentin (dentinal tubules in the root are straighter, less divergent and not as numerous as in the crown)[10], materials and methods that compensate for the afore-mentioned limitations and provide maximum retention can 291 Afshar et. al ensure greater durability of composite restorations in primary teeth. Thus, this study sought to assess and compare the push-out bond strength of three 5th, 6th and 7th generation bonding agents to intracanal dentin in PAT. MATERIALS AND METHODS This experimental study evaluated 36 primary anterior teeth extracted due to severe caries in the past 6 months and stored in 0.5% Chloramine T solution for one week. The teeth were then stored in distilled water. Teeth crowns were cut 1mm above the cementoenamel junction using diamond discs perpendicular to the long axis of the teeth. According to Torres et al, [13] and using the multiple means comparison feature, the minimum sample size for each of the 3 groups was calculated to be 12 teeth via Minitab software taking into account α=0.05, β=0.2, mean difference=3.3 and SD=3.16. A total of 36 teeth were randomly divided into 3 groups (n=12). The teeth in each group were coded in such a way to ensure blindness of results. A 5th generation bonding agent (Single Bond 2)(3M, St. Paul, MN, USA), a 6th generation bonding agent (Clearfil SE) (Kuraray Co., Osaka, Japan) and a 7th generation bonding agent (Single Bond Universal)(3M, St. Paul, MN, USA) were used in groups 1, 2 and 3, respectively according to the manufacturer’s instructions (Table 1). Root canals were prepared using K files (Mani Inc.,) up to #3, irrigated with saline solution and dried with paper points (PT Dent, USA) by the researcher (post graduate student of pediatric dentistry). The coronal 3mm of the canals was restored with (...truncated)