The following was published in Volume 30, Issue 5 of The International Journal of Prosthodontics.
Editorial: A Provocative New Text
George A. Zarb, Editor-in-Chief
My dental education exposed me to several assertively proposed clinical rituals, professional rites of passage that would guarantee excellence of my technical performance and optimal treatment outcomes, even if the scientific backing could be far from compelling. It took a few years of independent clinical practice and coping with my career’s teaching responsibilities to recognize that a great deal of what I had learned—and indeed, subsequently taught—lacked an ecological intraoral context; and that treating an absent or missing single anterior tooth with a fixed three-unit prosthesis ignored the plain fact that enamel is not a renewable resource. The operational rationale was that while time-dependent concerns regarding pulpal and gingival responses to the recruited abutment teeth were not readily predictable, one could always revise the original treatment as needed.
The arrival of the adhesive dentistry era provided an exciting scope for alternative and more ecologically prudent ways to restore teeth and facilitate provision of replacements. However, osseointegration and its apparent ease at providing a tooth root analog quickly eclipsed serious reliance on the adhesive approach. This preprosthetic surgical intervention rapidly embraced by sister specialty groups was enthusiastically advanced as a quasi-panacea, irrespective of the fact that proposed host bone sites were not always ideal candidates for implant location. Numerous ingenious techniques were developed to go on justifying routine implant management, even in young patients whose age-determined morphologic features needed thorough consideration. It became clear that a populist assignment of implant management to the top of a hierarchical treatment list for the missing single tooth was misleading, and that a far more measured and ultimately prudent way of offering patients a best treatment choice, especially in an age-dependent context, was required.
Matthias Kern has undertaken this challenge very convincingly in his new text, and the Journal is pleased to offer this Invited Commentary to describe why he wrote his book.
Invited Commentary: Minimally Invasive Single-Tooth Replacement Without Implants—A True Alternative?
Resin-bonded fixed dental prostheses (RBFDPs) were introduced in the early 1970s. Researchers at the University of Maryland redefined aspects of restoration design, and their described “Maryland bridge” quickly gained popularity. Regardless, RBFDPs never became a standard treatment procedure in general dental care, and their ongoing development was curtailed by the potential and versatility of the osseointegration technique.
RBFDPs are considered by most dentists as long-term provisional restorations placed until a single-implant restoration can be provided. However, there is now a growing body of evidence that single implants inserted for single-tooth replacement in the esthetic zone often result in esthetic problems in later years. Although orthodontic literature has long underscored the fact that craniofacial growth continues during adulthood, it appears that morphologic consequences have often been ignored when placing single implants in the esthetic zone. This oversight might be due partially to the perception of many dentists that true long-term and lasting alternative treatment options were missing when adjacent teeth were caries free and should not be cut down for crowns to retain a conventional fixed dental prosthesis. Osseointegrated implants behave like ankylosed teeth roots, and after some years with craniofacial growth and eruption of the anterior teeth, the implants end up as infra-positioned. While the incisal edge might be adapted by providing a new crown, the gingival position of the implant-retained crown will show adverse change, especially in patients with a high lip line. Regrettably, repositioning the now vertically malpositioned implant is possible only to a very limited extent.
Therefore, in the light of recently published clinical studies revealing excellent long-term outcomes of single-retainer RBFDPs, which compare well with the success and survival rates of single-tooth implants in the esthetic zone, the standard of care for the replacement of missing incisors in the esthetic zone should be reconsidered. In RBFDPs, the pontic “erupts” together with its abutment tooth, and no incisal infrapositioning will occur, even over the course of decades. In addition, the popular view that replacing single teeth with implants will result in better preservation of bone and soft tissue than the use of (RB)FDPs is questioned by clinical observations showing no clinically relevant tissue resorption beneath pontics, even after many years. Recently published clinical studies using digital measuring techniques over 5 and 10 years confirm these results.
RBFDP cases treated and clinically observed by the author for more than two decades are presented in the book RBFDPs: Resin-Bonded Fixed Dental Prostheses—Minimally Invasive—Esthetic—Reliable. These numerous case histories reveal that when using an adequately designed ovate pontic with a concave soft tissue contact area, no clinically relevant tissue resorption occurs in the area beneath the pontic for up to 20 years. It might be speculated that an adequately designed pontic is able to transfer some physiologic stimulation to the edentulous ridge through its basal contact area, which results in its long-term preservation.
The author’s clinical experience over the past two decades indicates that a rarely encountered adverse event for a single-retainer, all-ceramic RBFDP is fracture or debonding. In case of the first complication, the RBFDP must be renewed; in the second, the RBFDP can be rebonded. Long-term complications of single-tooth implants are much more severe and include vertical malpositioning, recession of the soft tissue, gingivitis with or without marginal bone resorption, and implant fracture. Consequently, the preference for the use of implants over RBFDPs by most dentists is difficult to understand, given the clear ecological advantages of the latter’s protocol and treatment outcomes.
The question must be posed—why are single-retainer RBFDPs still not used as standard of care when indication(s) are explicit? One reason seems to be the technique sensitivity of bonding methods and associated bad experiences of many dentists. Moreover, there are still clinical rumors that bonding zirconia ceramic would not be reliable. As a series of surveys in Northern Germany showed, there is still a considerable lack of knowledge when it comes to understanding the principles of reliable ceramic bonding among dental practitioners. However, these principles are already well known and have been con rmed in various clinical studies with nonretentive RBFDPs. The most recent clinical study on zirconia ceramic single-retainer RBFDPs showed a survival rate of 98.2% after 10 years. Overall, 8.0% of the RBFDPs debonded, but it must be kept in mind that they could always be rebonded.
It might be time to reconsider the standard of care for single-tooth replacement of incisors in the esthetic zone. Zirconia ceramic single-retainer RBFDPs are not only minimally invasive and esthetic, but also very reliable—and they do not bear the long-term risks of anterior implant protocols. A compelling concern now is whether the profession is prepared to reconsider the best way to replace the missing single tooth.
Bienz SP, Sailer I, Sanz-Martín I, Jung RE, Hämmerle CH, Thoma DS. Volumetric changes at pontic sites with or without soft tissue grafting. A controlled clinical study with a 10-year follow-up. J Clin Periodontol 2017;44:178–184.
Botelho MG, Chan AW, Leung NC, Lam WY. Long-term evaluation of cantilevered versus fixed-fixed resin-bonded fixed partial dentures for missing maxillary incisors. J Dent 2016;45:59–66.
Kern M. Fifteen-year survival of anterior all-ceramic cantilever resin-bonded fixed dental prostheses. J Dent 2017;56:133–135.
Kern M. Resin bonding to oxide ceramics for dental restorations. J Adhes Sci Technol 2009;23:1097–1111.
Kern M, Passia N, Sasse M, Yazigi C. Ten-year outcome of zirconia ceramic cantilever resin-bonded fixed dental prostheses and the influence of the reasons for missing incisors [epub ahead of print 5 July 2017]. J Dent doi: 10.1016/j.jdent.2017.07.003.
Klosa K, Meyer G, Kern M. Clinically used adhesive ceramic bonding methods: A survey in 2007, 2011, and in 2015. Clin Oral Investig 2016;20:1691–1698.
Nowadays single-retainer metal-ceramic and all-ceramic resin-bonded fixed dental prostheses (RBFDPs) often present a minimally invasive alternative to single-tooth implants or other conventional prosthetic methods. With a growing body of evidence showing that implants placed in the esthetic zone of younger patients present a high risk of esthetic problems in later years, RBFDPs made from zirconia ceramics are experiencing a great renaissance. This book details the protocols necessary to achieve success when replacing incisors with single-retainer RBFDPs. Although the method is technically sensitive, it is simple and extremely reliable when the correct procedures are implemented. The principles outlined in the text can also be used to replace canines and premolars. Numerous high-quality figures detail the procedures for metal-ceramic and all-ceramic RBFDPs, and case presentations—some with 20 years and more of follow-up—document the development of the success model for RBFDPs. This comprehensive text will benefit practitioners who want to expand their minimally invasive treatment options for esthetic single-tooth replacement.
264 pp; 888 illus; ISBN 978-1-78698-020-5 (B9102); Available now! US $148