Contents lists available at ScienceDirect Journal of Dentistry journal homepage: www.elsevier.com/locate/jdent Full Length Article Novel self-healing dental luting cements with microcapsules for indirect restorations Junling Wu a, ⁎ , Qiang Zhang b , Michael D. Weir c , Thomas W. Oates c , Chuanjian Zhou d, ⁎ , Xiaofeng Chang e, ⁎ , Hockin H.K. Xu c,f,g,h a Department of Prosthodontics, School of Stomatology, Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Jinan, 250012, China b Oral Implantology Center, Jinan Stomatological Hospital, Jinan, 250001, China c Department of Endodontics, Periodontics and Prosthodontics, University of Maryland Dental School, Baltimore, MD 21201, USA d Research Institute of Polymer Materials, School of Materials Science and Engineering, Shandong University, Jinan, 250061, China e School of Stomatology, Xi’an Jiaotong University, Xi’an, Shaanxi, China f Center for Stem Cell Biology & Regenerative Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA g Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, USA h Department of Mechanical Engineering, University of Maryland, Baltimore County, MD 21250, USA ARTICLE INFO Keywords: Self-healing dental luting cements Microcapsules Polymerizable healing liquid Water-aging Mechanical property recovery ABSTRACT Objectives: Dental luting cements are widely used to bond indirect restorations to teeth. Microcracks often lead to cement failures. The objectives of this study were to develop the first self-healing luting cement, and in- vestigate dentin bond strength, mechanical properties, crack-healing, and self-healing durability in water-aging for 6 months. Methods: Microcapsules of poly(urea-formaldehyde) (PUF) shells with triethylene glycol dimethacrylate (TEGDMA) as healing liquid were synthesized. Cement contained bisphenol A glycidyl dimethacrylate, TEGDMA, 4-methacryloyloxyethyl trimellitic and glass fillers. Microcapsules were added at 0%, 2.5%, 5%, 7.5%, 8.5%, 9.5% and 10%. Dentin shear bond strength was measured using extracted human teeth. Flexural strength and elastic modulus were measured. Single edge V-notched beams were used to measure fracture toughness (K IC ) and self-healing. Specimens were water-aged at 37 °C for 6 months and then tested for self-healing durability. Results: Adding 7.5% microcapsules into cement achieved effective self-healing, without adverse effects on dentin bond strength and virgin mechanical properties (p > 0.1). Excellent self-healing of 68%-77% recovery was obtained. Six months of water-aging did not decrease the self-healing efficiency, compared to 1 d (p > 0.1), indicating that the self-healing property did not degrade in water-aging. Conclusions: A self-healing dental luting cement was developed for the first time. It contained fine microcapsules and exhibited an excellent self-healing efficiency, even after being immersed in water for 6 months. Clinical significance: The self-healing cement is promising for cementing crowns and bridges and other adhesive cement applications, to heal cracks and increase restoration longevity. 1. Introduction Dental luting cements play an important role in dentistry to attach indirect restorations including inlays, crowns and bridges to the pre- pared teeth [1]. Success of indirect restorative procedures depends partly on the cementation technique used to create a critical link be- tween the fixed prostheses and their supporting tooth structures [2,3]. Although the clinical performance has been improved rapidly, dental cements still have relatively poor physical properties compared to bulk restorative filling materials and are prone to fractures [4–6]. At the restoration-tooth cemented interfaces or margins, the bond longevity is mainly affected by microcracks induced by polymerization shrinkage, repetitive dynamic mechanical loading, water sorption and thermal fatigue [7–9]. These microcracks could coalesce under cyclic stresses and eventually cause cement fracture, which is a main reason for the failure of cemented restorations [10,11]. Therefore, extensive efforts have been undertaken to improve the properties of dental luting agents to increase the clinical service lives. They include modifying the com- positions [12–14] and optimizing the handling properties [15,16]. However, there have been few reports on inhibiting microcrack pro- pagation to protect the cement’s integrity. An innovative strategy is to develop self-healing materials by incorporating microcapsules [17]. http://dx.doi.org/10.1016/j.jdent.2017.08.006 Received 28 April 2017; Received in revised form 10 August 2017; Accepted 12 August 2017 ⁎ Corresponding authors. E-mail addresses: doctorwujunling@163.com (J. Wu), zhouchuanjian@sdu.edu.cn (C. Zhou), changxf@xjtu.edu.cn (X. Chang). Journal of Dentistry xxx (xxxx) xxx–xxx 0300-5712/ © 2017 Published by Elsevier Ltd. Please cite this article as: Wu, J., Journal of Dentistry (2017), http://dx.doi.org/10.1016/j.jdent.2017.08.006