Figure 1  Seated Patient

The performance of any physical task is compromised when the setting and instruments used do not allow balanced operating positions for peak function (fig.1) (fig. 2). Past engineering has approached design innovation from the standpoint of modifying existing hardware and relocating different components in the setting to improve ergonomics and efficiency. This focus on existing hardware has made peak human potential, defined as doing the best performance of which one is capable, difficult to achieve. Dr. Daryl Beach, an American dentist residing in Japan, created a new way for dental equipment and instruments to be designed in 1962. This method he termed Performance Logic, an alternative approach to the delivery of dental services, which optimizes the performance of the dentist as s/he acts out dental procedures (fig. 3).

The most logical approach to design and performance first considers the conditions and use of the human body. The task or act being performed is considered second. Imbalance and strain in the dentist's body, limbs, and fingers during dental procedures are considered and comparisons are made with a style of performing which minimizes or eliminates this imbalance or strain. To construct a means for optimal performance the procedure is pantomimed blindfolded in open space by the dentist. Every aspect of the procedure is then analyzed in relation to the performers proprioception, a mechanism our bodies have for awareness (pressure and location) of component anatomy. This proprioceptive sense can simply be experienced by closing your eyes and touching the end of your nose with your index finger.

Figure 2  Tilting Patient

When you think you have achieved this relation of head to finger, open your eyes. You will find that you indeed are looking right at your finger.

After acting out the procedure in open space, the dentist now considers the same procedure while simultaneously considering the positioning of the dentist and patient. Finally, based on the less stressful and preferred positioning desired by pantomime, the dentist is encouraged to imagine new tools and technology that minimizes the number of positioning and repositioning acts during the technique. Ideally, being human centered presents nothing that gives you an image of an object. Having no physical instruments in hand allows the dentist to derive new technologies that make dental care easier and more human-centered.

Proprioceptive derivation (pd) tests not only delineates the performance of acts that are most ergonomically efficient but also are most suitable to the human anatomy and mind in relation to others. Therefore, when pd conditions have been established there will be no need for more ergonomic studies. If we do not have

Figure 3  Full Rest Patient

pd, we do not have a basis for ergonomics. When we have pd conditions we have much more than what ergonomic conditions were suppose to provide. We have optimum operating control, absence of mental stress during treatment of patients, and an individual awareness of the basis for judgments based on human centered conditions in the field of health care.

Pd based design innovations include a stabilized support for the patient; new standards for weight, dimension, angulation, and contact surfaces of instruments and handpieces; and skill programs that teach dental students and dentists to effectively use these new technologies.