Removable Partial Dentures throughout history have been, and still are, the most maligned and misunderstood area of prosthetic dentistry. Now, more then ever, the time has come for dentistry to recognize and correct this misconception.
Removable Partial Dentures in Dentistry are now at the advent of a new age. There are several factors that indicate the need for an increase in RPD'S.
1) People are living longer and saving more of their remaining teeth.
2) Baby Boomers, the largest segment of the population (Approximately 76 million) are now reaching the age of prosthetic needs.
3) Implants and crown and bridge, although preferred treatment plans, are not always indicated and are far more expensive for the patient.
4) Dentistry is more accessible for more people then ever before. Immigration has increased and many of these people have not had the benefit of proper dental care in other parts of the world.
5) Managed Care is on the rise. Most insurers are very particular about paying out for "fixed" restorations (i.e. Implants and Crown and Bridge), limiting treatment plans.
In order for a RPD to function properly, certain physics and engineering principles must be applied to their design, and ultimately to the abutment teeth. These laws of physics known as Class 11 lever and balance of force principles are necessary to direct forces vertically along the long axis of abutment teeth, while minimizing any horizontal torque forces. Balance of force principles must also be followed so that retention of RPDs is passive during mastication. Passive retention will virtually eliminate the "extraction forceps" design of conventional partial dentures.
As far back as the 3rd century BC, the great physicist and mathematician Archimedes formulated most of the principles covering leverage and forces in action. He was the one, according to the story, who said that if he had a lever long enough, a proper fulcrum, and a base to stand on, he could move the word. This of course described the use of the Class I lever, and when applied to the mouth will produce tremendous lateral torque on abutment teeth. A Class I lever force acts like forceps on abutment teeth creating a crowbar effect on to the abutment tooth. Class I lever has the fulcrum placed between an effort arm and a resistance arm. With the Class I lever, the fulcrum (the rest) will have excessive horizontal forces applied laterally on the abutment tooth. Today, most removable partial dentures are still designed with these types of conflicting forces even though we understand the nature of these deleterious forces on abutment teeth. This design principle will constantly create failures in the mouth. In order to eliminate these conflicting forces, it is necessary to utilize both balance of force principles and Class 11 lever design. The only partial denture system that utilizes all these engineering principles of physics is the Equipoise® Complete Removable Partial Denture System.
With the Equipoise Complete Removable Partial Denture System, true intra-arch Class 11 lever and balance of force principles are always utilized. When a Class 11 lever design is applied to a partial denture it will perform several functions. During mastication, when retention is not necessary, the retentive device, called an Equipoise® Clasp or E-clasp, is moving in the same direction as the denture base and goes from the area of greatest girth on the tooth to an area of lesser girth below the tooth's height of contour. The only metal now touching the tooth is the prepared occlusal spoon-shaped rest, which can only direct the masticating force along the long axis of the tooth. When a dislodging force is applied to the denture base, it and the free-end bar must move in the same direction, since the denture tends to rotate around the fulcrum rest. The free-end bar placed just below the undercut of the tooth now engages the undercut and positive retention is assured. These forces are kind and gentle and are designed to strengthen, protect and preserve abutment teeth.
For every action, there is an equal and opposite reaction. In the 17th century, Sir Isaac Newton's laws relating to forces stated "For two forces acting on a particle to be in equilibrium, the forces must be equal and opposite." This axiomatic law is necessary to adhere to when discussing proper clasp design. It is fundamental in the design of clasps in all Equipoise® RPDS. When clasps are not precisely equal and opposite on an individual tooth, equilibrium can not be obtained and movement of the tooth will occur.
With the Equipoise System the Class 11 lever design is carried one step further. All clasping is designed intra-arch. There are no clasps on the buccal or lingual aspects of teeth. All E-clasps are designed on the mesial or distal aspect of the teeth facing the edentulous area, to reduce lateral torque. Today, it is accepted Dental Practice to place rest preparations and guide plane preparations into enamel. The Equipoise® rest and guide plane are placed facing the adjacent tooth opposite the edentulous area. For proper function Equipoise Partials rely on this concept. If the preparation of enamel is felt to possibly lead to the deterioration or loss of the abutment tooth then a proper restoration, (amalgam, composite, or Equipoise® type crown) may be placed. It must be understood that ignoring the placement of proper rest seats, clasps, and guide planes will lead to the ultimate compromise or loss of a tooth due to improper lateral force applied to it. There should be no argument to justify a restoration placed preventively when the choice of ultimate loss is considered. By providing proper rest preparations, Equipoise® can not only save teeth, but also enhances the esthetics of the prosthesis.
The Equipoise® design principle is taken one step further with the use of the Equipoise(& C&L attachment. The C&L precision attachment combines an intra coronal attachment, the C-rest (counterpoise stabilizer) and the L-spring (retentive device). These components are used in place of the Equipoise® rest, guide plane and E-clasp. The applied forces of the Equipoise® principle enables Equipoise® to boast of the only single abutment crown designed to support a free-end saddle! This has been documented with 35 years of clinical proof and thousands of successful cases. By virtue of its unique size, mechanism of action, and shape, the C-rest and L-spring can be used in virtually any diagnostic situation involving replacement of missing teeth.
There is no need for catalogues of attachments. This is a "one size fits all" situation. As a matter of fact each and every ingenious L-Spring ever used can fit every Equipoise® attachment case designed regardless of who the patient maybe or where they are from, because they are universal in size and shape and interchangeable chairside.
With such sound principles of engineering behind it, the Equipoise® System easily eliminates the "Hodge Podge" design of RPD's we have seen. Why should the design of a removable partial denture be left to creativity spawning bizarre clasp configurations for retention while building in unaesthetic deleterious forces? Equipoise® designs have been fine tuned so that only four basic design types are used, whether replacing only one tooth or only one tooth remains. This system of design eliminates any guesswork and enables all Equipoise users to replace missing teeth the same way regardless of where they may practice. Not only is there uniformity, but only Equipoise® RPDs fulfill three design criteria:
1) Class 11 lever
2) Intra-arch design
3) Balance of force equilibrium clasp design
Based on these laws of physics, all other RPD designs are proven less successful in delivering long term optimal functioning and esthetic results.
The Equipoise complete partial denture system utilizes physics and engineering principles that are sound and have been proven clinically for over fifty years.
Testimonials from dentists throughout the world boast of "the best system" and verify its principles.
Equipoise® is with overwhelming clinical success, now more than ever, a viable and necessary component to the dental profession. The only way for Equipoise® to be further accepted into the dental community is for it to be inspected and taught in Dental Schools and utilized by all dentists. It is time for the entire dental community to unite in its approach to replacing missing teeth with removable partial prosthetics. The Equipoise® Dental Institute challenges the Dental Educational Institutions nationally and abroad as well as the Dental Community at large to evaluate, experience and criticize the Equipoise® Complete Partial Denture System. If a better system can be presented we would welcome the challenge.
The Equipoise® Complete Partial Denture System is supported with a hardcover textbook titled Equipoise the Proven Partial Denture System, two instructional videos (doctor and patient), tools and the parts necessary for the fabrication of the C&L precision partial denture. In addition, the Equipoise® Institute has an AGD accredited teaching facility located in Bergenfield, New Jersey and has supported lectures for over twenty five years to those dentists interested in better care for their patients. We encourage any and all of the Dental Community to contact the Equipoise® Dental Institute at 1-800-999-4950