March 2009, Volume 5, Issue 3
Published by AEGIS Communications
Complete Denture Therapy: How to Accomplish Optimum Patient Satisfaction
David Avery, CDT
The rising demand for restoration of edentulous patients presents a significant challenge and opportunity to the dental profession. According to research conducted by Dr. Chester Douglas, the number of arches requiring treatment will be approximately 37.9 million by 2020.1
The diminishing number of qualified clinicians combined with a shrinking dental laboratory technician pool magnifies the opportunity level for both professional parties.
The preservation of the supporting alveolar structure is greatly enhanced by the improved stability realized through the addition of root form implants.2
This therapy is becoming more readily available to patients because of a number of factors. The inclusion of more general practitioners as well as endodontic specialists in the placement of fixtures is creating a more competitive environment. Combined with improvements in restorative technologies and materials, the predictability of the treatment result is greatly improved. These factors inevitably lead to reduction of cost to the patient. As the cost is reduced, a larger sector of the population in need of this treatment accepts the plan.
The improved stability resulting from the attachment of the denture to a retainer is the relative benefit. The use of the “stud” type of attachment has been a popular approach to overdenture retention for many years. Their placement in endodontically treated teeth reduced to the gingival level to improve a poor crown root ratio is well documented in the literature3 and served as a solid foundation for similar retainers to be incorporated into implant therapy.
For the sake of this discussion, we will divide overdenture attachments into two classifications. The first classification is "soft tissue supported"-implant/attachment retained.” The use of “direct” attachments offers the simplest and most cost-effective means of accomplishing this task. These abutments are typically screwed directly into the implant body with a retaining component cured into the denture base at chairside or in the dental laboratory. Two popular examples of this category are the Snap Attachment (DENTSPLY Tulsa Dental Specialties, Tulsa, OK; and ANKYLOS® DENTSPLY Friadent, Mannheim, Germany) and Locator attachment (Zest Anchors, Escondido, CA) (Figure 1 and Figure 2).
The second classification is "implant supported-implant/attachment retained." The ANKYLOS® SynCone® system (DENTSPLY Tulsa Dental Specialties; and DENTSPLY Friadent) is a unique example of this technology. It features a high degree of parallelism between the abutments resulting in extreme rigidity and stability of the denture during function. Another contributing factor to the improved retention is the swaging of the gold attachment to the abutment during function. This rigidity eliminates loading of the edentulous ridge, resulting in preservation of the supporting alveolar process. A minimum of four implants/ attachments are required for the mandible and six for the maxillary. The system delivers a level of stability typically associated with fixed retrievable/hybrid restorations at a significantly more affordable cost to the patient. This system also permits immediate loading of the implants in the ANKYLOS system (Figure 3).
The most accurate technique is accomplished with the chairside “pick-up” of the retainers using visible light-cured resin. The inaccuracy associated with laboratory processing is a result of two factors:
1. The +/- 7% shrinkage that occurs during the curing process for “press packed” laboratory-processed methyl methacrylate (MMA). This can be controlled through the use of injection processing methods such as the Success (DENTSPLY Prosthetics/ Trubyte, York, PA) and Ivocap (Ivoclar, Amherst, NY) systems. It may also be contolled through the use of the Elipse (DENTSPLY Prosthetics) resin system. This system uses a revolutionary VLC/MMA-free material (Figure 4).
2. Processing on a stone cast eliminates the ability to compensate for soft tissue resiliency. Ideally, a complete denture is adapted to the soft tissue, supporting it before attaching to the implants through post-delivery evaluation with Pressure Indicating Paste (PIP) and the appropriate adjustments. By ensuring the base adaptation before connecting to the implants, the functionality and life expectancy of the attachment is improved.
However, the role of conventional materials also cannot be overlooked. The use of highly cross-linked, interpenetrating polymer networks of MMA is essential in denture teeth (eg, Portrait IPN®, DENTSPLY Prosthetics/Trubyte) for enhanced wear resistance. Better retention of removable prostheses leads to higher bite forces, and durability of the denture tooth becomes a key criterion in enhancing esthetic, phonetic, and functional outcomes.
The use of bars to more favorably position the retainers is a common technique. The bar allows attachments to be ideally placed with less regard for implant position for improved stability. Dental technology has evolved to the point that CAD/CAM-fabricated titanium bars provide restorations at a lower cost with vastly improved accuracy, biocompatibility, and clinical performance compared to conventional cast bars (Figure 5).
Proper preoperative treatment planning has always been the key to accomplishing predictable and cost-effective prosthodontic results. Nowhere is this truer than implant therapy. The diagnostic capabilities presented by improved radiography such as cone beam, digital diagnostic software, and the resulting surgical guides provide opportunity for predictable outcomes (Figure 6a and Figure 6b ). As presented in this article, the simplest scenario is an overdenture supported by direct attachments. It is far less expensive than bar fabrication and easier to accomplish and maintain by the patient. State-of-the-art diagnostics adds preliminary expense to treatment, yet is returned many times over through a predictable treatment outcome that minimizes the need for more expensive, corrective hardware.
As this wonderful prosthetic service moves into the mainstream, it is imperative that we do not oversimplify the treatment at the expense of a predictable outcome.
The author has disclosed that he is a current consultant for, and has received honoraria from, DENTSPLY.
1. Douglass CW, Shih A, Ostry L. Will there be a need for complete dentures in the United States in 2020? J Prosthet Dent. 2002; 87(1):5-8.
2. Romanos GE. Present status of immediate loading of oral implants. J Oral Implantol. 2004;30(3):189-197.
3. Heartwell CM, Rahn AO. Syllabus of complete dentures. 4th Edition. Philadelphia, PA: Lea and Febiger; 1986:501.
About the Author
David Avery, CDT
Director of Training and Education
Drake Precision Dental Laboratory
Charlotte, North Carolina