Lyndon F. Cooper, DDS, PhD
The provision of implant-supported or -retained prostheses is now broadly recognized as an accepted modality for the management of edentulism. Over three decades, technological advances have provided new concepts and tools for treating edentulism using dental implants. While challenges to successful osseointegration still remain, the impact of surface topographic enhancement on implant success and survival has been demonstrated for the edentulous maxilla and for low-density bone. Many of the challenges in creating complex and large prostheses retained by multiple implants have been circumvented by computer numeric control manufacture that eliminates the dimensional inaccuracies that accumulated in traditional lost-wax casting of metallic frameworks.
However, clinicians face yet another challenge when treating edentulism using implants. The biologic implications of placing a foreign body (ie, the implant and abutment) through oral mucosa and attaching a prosthesis—a biofilm-accumulating and non-shedding surface—into the oral cavity remain largely unexplored. Successful treatment of edentulism requires the effective and lifelong management of osseointegration, mucosal integration, and prosthetic integrity. An important added consideration is the individual patient, including his or her functional, social, and financial expectations and the systemic health factors he or she presents in individual management. The challenge of treating the edentulous patient is far from unidimensional.
Past investigators and scholars have broadly divided the treatment of the edentulous patient into two technical therapeutic categories. One is treatment using a fixed prosthesis, retained on implants (or abutments) using screws or retained on abutments using cement. The other is treatment using a removable prosthesis or overdenture retained by unsplinted implants with attachments or by splinted implants with a superstructure bearing attachments.
Previously reported factors that guided the selection of fixed versus removable prosthetic solutions for implant-related treatment of edentulism included anatomic restrictions that encompassed bone and soft-tissue deficiencies, relative or absolute prognathism, and phonetic complications. Recent evidence indicates that neither the implant location, the number of implants, nor the type of restoration influences implant loss rates.1 Further, while there is some data demonstrating that implant-retained or -supported prostheses provide a high level of measured satisfaction,2 fixed prostheses are often discussed as “superior” or “advantageous” in terms of function and satisfaction. The patient's expectations are, thus, central to the decision-making process when selecting treatment using fixed versus removable prostheses.
More recently, the lifelong management of implant prostheses has come into focus among clinicians. Regarding implant prostheses, the wear, chipping, and fracture of acrylic-wrapped metal framework prostheses (“hybrid”) is commonly reported and progressive over time. PFM and layered zirconia prostheses demonstrate chipping and fracture that is costly to repair. Monolithic zirconia prostheses are relatively new and the published limited experience is favorable, but not without complications and rare catastrophic failures. The long-term biological impact of implant prostheses in the edentulous patient is also of growing concern, and it is peri-implantitis that challenges successful management of a significant percentage of treated patients.3 The prevention and management of peri-implant mucositis and peri-implantitis requires long-term supportive care that involves careful oral hygiene, detailed clinical examination, and mechanical biofilm disruption. Together, these growing data sets regarding the long-term management of edentulous individuals with dental implants (irrespective of prosthesis type) can be facilitated by, or may require more frequent removal of the prosthesis for, prosthetic repair, implant hygiene, or intervention.
The advantages of removable prostheses for hygiene access, implant assessment, and intervention and repair or replacement are clearly aligned with the goals of long-term management of the edentulous implant patient. However, patient perceptions and clinical prejudices regarding removable prostheses may present substantial barriers to more widespread adoption. The visual similarity of removable implant prostheses with dentures relates to the presence of flanges and palatal coverage and these visual cues are reinforced by oral sensations of mucosal contact and motion. While bar overdenture constructions can sometimes remove the mucosal contact, they are associated with important dimensional limitations to their usage and also are reported to retain biofilm that contributes to mucositis and peri-implantitis. Alternatives to fixed and implant-supported or -retained removable prostheses may be valuable in dentistry's efforts to improve the long-term management of the edentulous implant patient.
One early approach investigated is the use of double crown prosthesis construction.4 A prefabricated unsplinted rigid Syncone attachment system (ANKYLOS® Syncone®, Dentsply Implants, dentsplyimplants.com) also provided a removable solution for implant-retained prostheses with the key advantage of providing improved oral hygiene capability compared to bar-retained prostheses.5 A customized Conus abutment solution (ATLANTIS™ Conus abutments, Dents-ply Implants) to support removable prostheses on unsplinted implants was recently introduced and offers individualized CAD/CAM control of the mutual parallelism needed for therapeutic success. These solutions involving four or more implants provide both support and retention of the prosthesis without the requirement of mucosal support. They are all removable by the patient to enable hygiene, and because they are freely removable, they are readily repaired. Most recently, another innovative abutment solution has emerged that also enables the removal of a full-arch prosthesis from the abutment, with removal and replacement facilitated by the clinician. The LOCATOR F-Tx® Fixed Attachment System (Zest Dental Solutions, zestdent.com) introduces another means of connecting a prosthesis to an abutment that is free of cement and requires no screws.
These innovations each differ in their relative advantages and disadvantages, but all of them may be used to support a restoration that is divested of flanges (not denture-like), may be removed for hygiene access, and enable direct repair or revision.
In this supplement to Compendium, clinical contributors share early experiences in the initial management of edentulous patients using this new class of implant prosthesis that is perceived as fixed by the patient, but is removable as needed by the practitioner. This special issue begins to explore our ability to provide individual patients with the perceived or recognized benefits of a fixed prosthesis and the desired advantages of a removable prosthesis that may enhance long-term management of the edentulous implant patient.
ABOUT THE AUTHOR
Lyndon F. Cooper, DDS, PhD
Associate Dean for Research and Head of the Department of Oral Biology, University of Illinois at Chicago College of Dentistry, Chicago, Illinois
REFERENCES
1. Kern JS, Kern T, Wolfart S, Heussen N. A systematic review and meta-analysis of removable and fixed implant-supported prostheses in edentulous jaws: post-loading implant loss. Clin Oral Implants Res. 2016;27(2):174-195.
2. De Bruyn H, Raes S, Matthys C, Cosyn J. The current use of patient-centered/reported outcomes in implant dentistry: a systematic review. Clin Oral Implants Res. 2015;26(suppl 11):45-56.
3. Meijer HJ, Raghoebar GM, de Waal YC, Vissink A. Incidence of peri-implant mucositis and peri-implantitis in edentulous patients with an implant-retained mandibular overdenture during a 10-year follow-up period. J Clin Periodontol. 2014;41(12):1178-1783.
4. Frisch E, Ziebolz D, Rinke S. Long-term results of implant-supported over-dentures retained by double crowns: a practice-based retrospective study after minimally 10 years follow-up. Clin Oral Implants Res. 2013;24(12):1281-1287.
5. Cepa S, Koller B, Spies BC, et al. Implant-retained prostheses: ball vs. conus attachments - A randomized controlled clinical trial. Clin Oral Implants Res. 2017;28(2):177-185.
