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Towards an improved dental pulp-capping therapy

Book - Dissertation

SUMMARY.A recent Delphi survey on the future of restorative dentistry for the next 20 years identified maintenance of the pulp vitality as of the highest importance [1]. The authors rated bioactivity toward the pulp-dentin complex as key property for future tooth-restorative materials. This need to develop bioactive restorative materials was also the conclusion drawn on a workshop ('Future innovation and research in dental restorative materials') of the International Association for Dental Research (2012) in response to the decision taken by WHO to globally phase-down the use of (dental) mercury (amalgam restorations). Both 'maintenance of pulp vitality' and 'bioactivity toward the pulp-dentin complex' imply a need for the restorative material to be also therapeutically active in the form of biologic interaction with tooth-pulp cells. The two processes targeted are reactionary and reparative dentinogenesis [2]. Reactionary dentinogenesis refers to the stimulation of healthy odontoblasts to produce tertiary dentin to serve as barrier against external irritants that may endanger the pulp's vitality('indirect' pulp capping). Reparative dentinogenesis requires recruitment of new cells thatdifferentiate into new odontoblasts-like (dentin-forming) cells in the event the pulp is severely injured with loss/destruction of the original odontoblasts. This 'direct' pulp capping is typically employed to treat pulpal exposures, accidentally caused by trauma or by the dentist when bur excavating aries very close to the pulp. The ultimate goal is to avoid an often technically demanding and costly root-canal treatment that would definitely undermine the tooth's lifetime; a pulpless tooth is weaker, may discolor, and often requires more invasive restorative procedures like the preparation of a root-canal post.Vital pulp therapy involves the placement of a bioactive medicament directly over the exposed pulp with the objective of maintaining the pulp's vitality [3]. Primary requirements for a successful therapy are an uninflamed pulp, adequate arrest of pulpal bleeding (hemorraghe control), a bacteria-tight seal, and the use of a capping material that is not only tolerated by the pulp, but also bio-activates the pulp [4]. A more invasive form, commonly applied to deciduous teeth of children, is a pulpotomy; this involves removal of the inflamed pulp tissue to the level of healthy coronal or even root pulp, followed by application of the pulp-capping agent.Historically, Calcium hydroxide (CaOH) has been the standard pulp-capping agent [5]. The mechanism of action has been attributed to its disinfection potential and simultaneous induction of dentinal bridge formation (12). The mild irritation provoked to the pulp initiates an inflammatory response that, in absence of bacteria, will heal by forming a dentin bridge'. While the actual repair mechanism is still not fully understood, the induced release of bioactive molecules, including bone morphogenetic proteins (BMP) and transforming growth factor beta (TBF-ß) has been demonstrated to be involved [6,7]. Major shortcomings of CaOH are inferior physico-mechanical properties (disintegrates over time) and limited sealing potential against external bacterial ingress. CaOH does not self-adhere to dentin and a dentin bridge formed beneath CaOH often contains 'tunnel defects', still enabling bacterial penetration. Throughout the years, alternative materials, like zinc oxide eugenol, glass-ionomers, resin-based adhesives, and more recently a bioactive cement, known as 'mineral trioxide aggregate' (MTA), have been advocated for vital pulp therapy [3,8]. Much dispute arose within the research community regarding the use of resin-based adhesives; while they possess a better sealing ability, they lack antibacterial properties(with some exceptions) and they are most of all disliked for their (alleged) toxicity, in particular when applied directly to exposed pulpal tissue [9,10]. MTA (alkaline material based on calcium silicate technology) stimulates dentinal bridging; it is today frequently employed in clinical practice as pulp-capping material, yet long-term clinical success needs to be demonstrated [8]. The primary reaction product of MTA with water is calcium hydroxide, so its principal mechanism of action largely follows that of CaOH. Besides for (in)direct pulp capping (and pulpotomy), MTA serves a more versatile application area, in particular as root canal repair material (root perforation, ex-/internal resorption, apexification, apexogenesis, revascularisation); it is often used as ultimate remedy to preserve the tooth that otherwise would be extracted. While setting within a moist environment and providing some dentinal sealing, reported disadvantages of MTA are its prolonged setting time, long-term solubility, potential discoloration of the tooth due to iron (grey formulation), its less user-friendly handling and relatively high cost.OBJECTIVES.Maintaining the pulp vital has been identified as a major future role of tooth-restorative treatment, thereby emphasizing the importance/impact of this research project, in particular as the restoration of teeth accounts for the major part of everyday dental practice and nearly the whole population may be in need of a tooth restoration sooner or later. The OVERALL PROJECT AIM is to contribute to a better understanding of biomaterial-pulp interactions and yet to explore the mechanisms of pulpal repair following 'direct' pulp capping, which today remain insufficiently understood [2,11]. Since the current pulp-capping agents fall somewhat short of several properties, such as overall pulp survival, sealing ability, physicomechanical properties, and clinical handling, the more SPECIFIC PROJECT OBJECTIVE is to develop a clinically more effective and predictable pulp-capping material/technique.1. Seemann et al. Restorative dentistry and restorative materials over the next 20 years: A Delphi survey. Dent Mater 2014 doi:10.1016/j.dental.2014.01.013.2. Ferracane et al. Can interaction of materials with the dentin-pulp complex contribute to dentin regeneration? Odontology 2010;98:2-14.3. Hilton TJ. Keys to clinical success with pulp capping: a review of the literature. Oper Dent 2009;34:615-25.4. Swift et al. Vital pulp therapy for the mature tooth - can it work? Endodontic Topics 2003;5:49- 56.5. Stanley and Pameijer. Dentistry's friend: calcium hydroxide. Oper Dent 1997;22:1-3.6. Graham et al. The effect of calcium hydroxide on solubilisation of bio-active dentine matrix components. Biomaterials 2006;27:2865-73.7. Cooper et al. Inflammation-regeneration interplay in the dentine-pulp complex. J Dent 2010;38:687-97.(NWP).8. Comparison of Ca(OH)2 with MTA for direct pulp capping: a PBRN randomized clinical trial. J Dent Res 2013;92:16S-22S.9. Goldberg M. Biocompatibility or cytotoxic effects of dental composites. 2009: Coxmoor publishing; ISBN: 978-1-901892-34-5.10. Van Landuyt, ..., Van Meerbeek. How much do resin-based dental materials release? A metaanalytical approach. Dent Mater 2011;27:723-47.11. Niu et al. A review of the bioactivity of hydraulic calcium silicate cements. J Dent 2014; doi: 10.1016/j.jdent.2013.12.015.12. Yoshida, Van Meerbeek et al. Evidence of chemical bonding at biomaterial-hard tissue interfaces. J Dent Res 2000;79:709-14.
Publication year:2020
Accessibility:Open