The use of removable partial dentures (RPD), continues to be of significant value, particularly in the elderly population. This article review four RPD treatment modalities, some of the new technologies being used in RPDs, and their use and application in the elderly population.

By Prof John D. Jones and M. Norma Partida

For well over a century, removable partial dentures (RPD) have provided a viable treatment for partially edentulous patients. With the advent of osseointegrated dental implants and even more recent technologies, treatment possibilities have considerably evolved and improved.

For years new technologies have been dramatically improving the quality of removable partial denture and the lives of patients who use them [1]. As well as improved impression materials, there have been developments in other necessary materials, techniques and designs.
Four treatment modalities will be described in this article. Some of these modalities have served patients well for many years whereas others have been more recently introduced. These modalities include conventional RPD, attachments and the RPD, the interim RPD and the implant-supported RPD.

Conventional RPD
Although the original removable partial dentures may be described as conventional, the RPD has nevertheless continued to evolve so that when dentists refer to a “conventional” RPD, there may be some differences in what they mean by the term. However most would agree that the conventional RPD consists of a metal major connector that connects to the other components [2, 3, 4] [Figure 1].

Such prostheses provide vertical support on mouth preparations termed rests seats, into which the rests on the framework fit. Incorporated into the conventional RPD are clasps and clasp assemblies that serve as retentive and reciprocal elements. The RPDs also provide form and function for patients with varying teeth replacements. These may include denture teeth on a denture base as well as denture teeth on a metal base in posterior teeth (commonly called tube teeth) and reinforced acrylic pontics in anterior teeth.

Attachments
The use of attachments is becoming increasingly popular, with clinicians using dental implants with RPDs. Attachments are frequently used for aesthetic purposes, e.g., crowns on natural teeth, but they are also used to allow good retention of RPDs [5].

Attachments are available in a variety of shapes and sizes for a number of different applications. Extracoronal attachments do not require additional reduction in the preparation, but they do require additional space within the RPD [Figure 2]. Intracoronal attachments do not require additional space in the RPD, but need space within the casting [6,7,8].

Widely used attachments for both implants and natural teeth include nylon clips, nylon rings or rubber rings. Many of these systems have a metal housing that makes replacement of the attachments much easier.

Acrylic resin RPD
Acrylic resin removable partial dentures are commonly referred to as interim or transitional RPDs. They provide a valuable service as a transition from natural teeth to artificial teeth or from no teeth to a resin RPD [9] [Figure 3].

A resin RPD may help serve as a prosthesis to provide treatment in orthodontics or therapy for Temporomandibular disorders [TMD] as well as for tissue conditioning prior to replacement of missing teeth. An immediate transitional RPD is an aesthetic restoration that allows patients to keep their teeth while the prosthesis is being made, and have the teeth extracted and the RPD fitted at the same appointment.

In certain situations resin RPDs may also serve as a definitive removable partial denture. This may be the case for economic reasons, because of poor oral hygiene, or because supporting structures are limited. In these cases the provision of additional rests is important to prevent stripping of the gingival tissues.

Implant supported RPD
With the advent of root form dental implants, partially edentulous patients who have a poor prognosis, with too few teeth for a conventional RPD, can now have an excellent prognosis with the addition of just one dental implant [10].
Implant supported removable partial dentures can change a distal extension and tooth/tissue supported RPD into a tooth/implant support with excellent retention and vertical support [11,12] [Figure 4]. Dental implants may also be used as a retentive abutment to eliminate a clasp on the adjacent tooth in the aesthetic zone.

New technologies
The use and advantages of Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) systems in research and in clinical practice of dentistry have been well described [13, 14]. These technologies can allow treatment without the need for impressions by scanning in the patient’s mouth or by making a final impression and scanning the master cast.

There are currently several manufacturers that market CAD/CAM technology and different companies that provide this service. It has been suggested that the number of practicing dentists using CAD/CAM technology will exponentially increase within the next ten years.
New resins and nylons have been developed recently, which can be used instead of traditional metals. A new semi-rigid transparent nylon frame utilises occlusal rests, clasps and proximal plates. It has been designed to replace metal frameworks and is aesthetically advantageous compared with some of the components of the metal counterparts.

A growing geriatric population
Trends in ageing worldwide
There is a steady trend towards an increase in the global population that is over 65 years old. This trend is due to both a decline in fertility rates and increases in life expectancy rates [15]. Worldwide, the ageing population > 65 years is expected to increase from approximately 550 million to 973 million during the three decades from 2000-2030.

Europe is expected to see an increase in the > 65 years population from 15.5% to 24.3%. With this increase in longevity there will inevitably be a corresponding increase in chronic diseases, of which the most common in this age-group are heart disease, stroke, cancer and diabetes. Such chronic conditions can impact on the patient’s ability to wear, clean and maintain an RPD.

Oral health factors
The FDI World Dental Federation, the World Health Organisation and the International Association of Dental Research have developed a series of global goals and targets to be reached in oral health by 2020 with one of the goals concerning the issue of tooth loss. The aim is to reduce tooth loss and increase the number of natural teeth remaining in the 65-74 year old population.

Overall, edentulism rates are declining worldwide. However, the average number of lost teeth increases with age [16]. The retention of natural teeth and the loss of some teeth with age necessitates a greater need and knowledge of effective RPD designs.

Patient factors influencing RPD preference
For the elderly in Europe, removable partial dentures are one of the main types of restoration for missing teeth [17]. The replacement of missing teeth with an RPD is linked to socio-economic status, demographics, education attainment levels and income. Patients with lower educational and socio-economic levels, or those living in rural areas, are more likely to choose an RPD over a fixed modality.

While there is a general increase in the use of dental implants in the elderly in Europe, nevertheless still only 2-4% of current elderly patients actually have dental implants [17]. This can again be attributed to the socio-economic factors mentioned previously. Another consideration is the training, experience and availability of dentists who can restore missing teeth with implants.

Conclusion
Although there have been fewer dramatic developments in removable partial dentures in recent years, the value of the treatment remains as important as ever. There are new designs, materials, implant supported removable partial dentures, new attachments and CAD/CAM technology that will continually allow this discipline of dentistry to evolve.

Some practitioners suggest that with dental implants and new technologies the need for RPDs will be less, but with the growing geriatric population, removable partial dentures will continue to be a valuable and important area of clinical dentistry.
 
References
1. Jones, JD, Turkyilmaz, I, Garcia, LT, Removable Partial Dentures – Treatment now and for the future, Tex Dent J 2010 Apr; 127(4)365-72
2. Jones JD, Garcia LT. Removable Partial Dentures – A Clinicians Guide, Components, 2009 Wiley-Blackwell
3. Phoenix R, Cagna D, Defreest C. Stewart’s Clinical Procedures for Removable Partial Dentures, 3rd edition, 2002, Quintessence Publishing Co.
4. Carr AB, McGivney GP, Brown DT. McCracken’s Removable Partial Dentures, 11th edition 2004, Elsevier Mosby
5. Jones JD, Garcia LT. Removable Partial Dentures – A Clinician’s Guide, Attachments, 2009 Wiley-Blackwell
6. Baker J and Goodkind R. Theory and practice of precision attachment removable partial dentures, St. Louis. 1978; the CV Mosby Co.
7. Mensor MC. Classification and selection of attachments J Prosthetic Dent 1973; 29(5):494-497
8. Prieskel HW Precision attachments in dentistry 3rd edition St. Louis, 1979, Henry Kimpton Publishers
9. Jones JD, Garcia LT. Removable Partial Dentures – A Clinician’s Guide, Acrylic Resin Removable Partial Dentures, 2009 Wiley-Blackman
10. Starr NL. The distal extension case: an alternative restorative design for implant prosthetics, Int J Periodontics Restorative Dent 2001;21(1):61-67
11. Battistuzzi PG, van Slooten H, Kayser AF. Management of an anterior defect with a removable partial denture supported by implants and residual teeth: case report. Int J oral Maxillofac implants 1992; 7(1):1-5
12. Giffin KM. Solving the distal extension removable partial denture base movement dilemma: a clinical report. J Prosthetic Dent 1996;76(4):347-349
13. Strub JR, Rekow ED, Witkowski S. Computer-aided design and fabrication of dental restorations: current systems and future possibilities. J Am Dent Assoc 2006;137(9):1289-96
14. Williams RJ, Bibb R, Eggbeer D, Collis J. Use of CAD/CAM technology to fabricate a removable partial denture framework. J Prosthet Dent 2006;96(2):96-9
15. Kinsella KG. Future longevity – demographic concerns and consequences. J Am Geriatr Soc 2005; 53(9 Suppl):S299-303
16. Muller F, Naharro M, Carlsson GE. What are the prevalence and incidence of tooth loss in the adult and elderly population in Europe, Clin Oral Implants Res 2007;18 Suppl 3:2-14
17. Zitzmann NU, Hagmann E, Weiger R. What is the prevalence of various restorations in Europe, Clin Oral Implants Res 2007 Jun;18 Suppl 3:20-33

The authors
Prof John D. Jones DDS
Professor, Prosthodontist
Dept of Comprehensive Dentistry
University of Texas Health Science Center
San Antonio, Texas, USA
and
M. Norma Partida DDS, MPH
Associate Professor, Geriatric Dentist
Dept of Comprehensive Dentistry
University of Texas Health Science Center
San Antonio, Texas, USA