DC: Please explain the concept of proprioceptive derivation.

MD: Proprioceptive derivation (pd) in health care is the process of deriving the best positioning of the operator’s body, patients, instruments, equipment, and physical space for optimal ergonomic functioning. In dentistry, pd involves an innate introspective process to derive more natural body positioning for performing dental procedures while also considering patient positioning, instrument and equipment design, as well as the layout of the environment in which the dental procedures are performed.

The process of applying the principle of pd allows the participant (the self-appraiser) to decide for him or herself the best use of the body for clinical practice. The individual uses feedback from proprioceptive neurons to discern the least physical effort and most efficient way to perform procedures in the mouth. In using the pd process, the eyes are masked to avoid distractions from visual clues and to focus attention on all muscles of the body while specific dental procedures are mimed. Past operating positioning habits and positioning previous experience with dental instruments and equipment are disregarded.

The outcome of applying pd results in skillful use of the body and ensures that human performance is measurable and verifiable. It reflects the essential principle of ergonomic functioning—using the least human effort needed to resist the effects of gravity that contribute to body disorders, errors in procedures and outcomes due to fatigue, stress, and strain, and the waste of material resources.

DC: Describe the procedure for “proprioceptively deriving” optimal working position, instrument location, etc. for the dental practitioner.

MD: Pd tests are strictly feel-based and involve miming health care procedures with masked eyes in open space that is, in areas unrestricted by objects). Masked eyes reduce sensory input so that the individual’s self-appraisal of how s/he performs imagined dental procedures focuses on perceiving any strain associated with body position and paths of motion. This includes establishing the best position for the operating point in the patient’s mouth to ensure optimal precision of the dental operation being “performed.”

Once the operating point is determined, the paths of motion for locating instrument supports, holders, monitors, switches and other technologies are identified in relationship to the operating point, again through masked miming procedures. This involves assessing the strain in the body, particularly of the eye, neck, and foot muscles, in regard to the frequency, duration, and time that it takes to access whatever equipment, instruments, switch, monitor, or materials that are needed to perform the operation.

The appraisal process next considers procedures from both the patient’s and assistant’s perspectives by having the dental care provider assume these roles. Participant appraisers do this, still masked, to better understand the stresses and strains and motion paths experienced during procedures from both the patient’s and the assistant’s points of view.

• positions for the operator’s body, limbs, and fingers while in use and at rest
• the points on the body, including fingertips and feet, that come in contact with patients and objects for stable control and sightings of the operating points
• human supports and material objects that account for pd body space, paths of motion of body parts, and location of instrument supports

Importantly, the pd process is human-centered rather than object-centered because it focuses on discerning the safest and most efficient way to perform dental procedures from the operator’s, the patient’s, and the assistant’s perspectives.

DC: What are the most common ergonomics no-no’s you see in dental practice?

MD: The most common ergonomic mistake I see is in malpositioning of the body of the seated operator. These “no-no’s” are observed mostly with operators who work from the side of the patient at or less than 9:30 position and place the patient’s mouth below the apex of their heart (- 10 cm. from a line connecting their arm pits). As a result of poor positioning, I see body twisting, leaning, slumping, head ducking, elbows raised for long durations, and finger work not in the body mid-line. Although learning pd procedures does not make one completely immune from these no-no’s, pd practitioners report that the amount of time they spend in a compromised body condition goes from approximately 60% down to 10% with pd skill.

The other “no-no” that I see is dentists purchasing dentist chairs solely on the basis of how comfortable the chair is when they sit in it. Dental equipment should be purchased based on how compatible it is with the operating process which, ideally, would be pd. Dentists need a set of evaluation criteria upon which to base their purchase of products for their ergonomic effects. Thus, they should go through the self-assessment I’ve discussed above before purchasing equipment if, in fact, they want to practice in the most ergonomic manner.

DC: What are some of the notable ergonomic modifications in today’s operatory equipment?

MC: Notable ergonomic modifications in today’s operatory equipment include stable dual lighting, touch-less adjustable headrests, a non translating lift for the patient support, the single multipurpose foot controller, and the integration of handpieces, technologies and instrument holders at the shoulder of the patient’s support. Also notable are the improvements in lighted evacuation equipment.

The weight, length, and diameters of early electric handpieces sent pd ergonomics backwards. However, the specifications for many electric handpieces and air-driven handpieces are getting closer to a pd range.

Another example of notable modifications of instruments that are often claimed to be ergonomic but are not pd, are sensing instruments with large-diameter handles. For example, the explorer is a sensing instrument, and sensing ability is compromised by the greater amount of finger contact surface used with large diameter handles. Also, the large diameter makes it more difficult to position.

DC: When designing and equipping the treatment room, what specifics should dentists be looking for?

MD: First, when designing and equipping the treatment room, the dental clinic owner/dental care provider should look for GEPEC pd-Acceptable components that have been determined to be human-centered by engineers and worldwide dentists. GEPEC is the first and only organization that evaluates products for their ergonomic compatibility with the user based upon a principle of body use. Pd surfaces (operator supports, patient supports, assistant supports) are level and non-tilting because humans physically related best to level, non-tilting surfaces.

In regard to an operator’s seat, it should create no pressure on the bottom of the thighs, have moderate posterior and lateral gluteal support, and the center of the axis of rotation of the seat should be between the ischeal tuberosities and above knee height. Bars at the base of the support that restrict foot movement are unacceptable. Operator back supports are optional and may be needed by some providers with disabilities. If the operator support has a back, it should not interfere with the fee range of motion of the elbows and the fully upright spine. Elbow supports are also not indicated when practicing under pd conditions since the use of elbow supports implies that the operator chooses to lean and/or extend his/her elbow far from their side. Further, delivery systems should provide either dual lighting or shadowless intraoral lighting, and all magnification should reflect pd conditions including working length and declination.

DC: For practitioners experiencing work-related pain, what’s the first step for determining the source and finding a remedy?

MD: If practitioners’ pain is suspected as being work-related (e.g., the person’s condition gets worse or is aggravated by performing work-related tasks), then management by using the process of pd care and pd-compatible clinics is indicated. The treatment setting where practitioners work must first be considered as equipment and physical space may not allow for natural upright positioning of the spine and natural paths of body and limb motion. The first step for practitioners with work-related pain who want to learn about using pd is to participate in an introductory course about pd which involves the self-assessments described above. Participants will derive the best treatment method for themselves through exercises, will experience how it feels to practice in a pd manner, and will be able to compare this with the way they have recently treated or currently treat patients to decide about changing to a pd practice.

DC: How would you characterize the progress toward establishing ergonomic standards in the dental industry?

The American Dental Association has included ergonomics as part of its wellness program. However, manufacturer interests tend to still govern what is debated and, therefore, the emphasis is on products that are not necessarily developed based on pd principles and best use of the human body for the practice of dentistry. Today those of us practicing pd dentistry are more convinced that a principle of pd is needed in health care as we are experiencing a global financial adjustment that has illuminated waste and self serving businesses. The public is witnessing the interface of an emerging survival-safety-health (SSH) economy with a group-personal choice economy that now seems to be leading to great waste recognized by world leaders.. Commitment to human centered standards in the dental industry and in dental clinics would be a demonstrable move toward the SSH economy.

DC: Are manufacturers interested?

MD: Definitely, yes. Most engineers agree with the principle of pd. However, I believe that the Dental Trade Association remains resistant to a single ergonomic pd standard for equipment and stands behind their dealers to market products that are equipment-centered as opposed to a human-process centered.

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Dentistry is a profession where consistent accuracy is required. A dentist’s judgment on skills, the setting where s/he practices, and the technology used affects the lives of many. Industry has taught us that to limit the adjustments and decisions a worker makes in manufacturing a product produces a product with fewer defects. Why should we think that dentistry is any different? Changing the tilting dental chair environment, which allows many adjustments and decisions, to an environment in which the dental patient support provides a stable reference for balanced operator positions limits adjustments and decisions during dental procedures and enhances the dentist’s performance. The non-tilting patient support requires advanced skills in order to function optimally.

Figure 1 Morita's Feel-Ease

New rules for the performance of motor tasks in dental procedures are self-derived using ones own proprioceptive feedback as well as self-modeling feedback via tracking cameras. The Skill Acquisition, Transfer, and Verification (SATV) model of developing psychomotor skills was developed by American dentist, Dr. Daryl R. Beach, through research and development at the Human Performance and Informatics Institute in Atami, Japan. The SATV system provides the most direct and reliable way in which students derive for themselves the way they want to practice throughout their career. SATV is divided into progressive stages of cognitive development starting with 0 for information and basic concepts through 6 which considers the inter-actions of the entire dental team and patients in clinical situations.

Figure 2 SATV Teeth

In the “Skill Acquisition” phase, students model and record the body positions and setting requirements that are compatible with the highest level of clinical performance that can be imagined. These conditions minimize the physical stress a dentist will experience during their career. These derivations are then used to adjust the SATV clinical setting to his or her unique body dimensions for optimal care delivery. Specific skills are acquired in simulating clinical acts using a simulated head, teeth, and pathologies. Immediate feedback is provided through CCD camera and digital/video recording for the frequency and the extent of variation from one’s self-selected optimal performance positions. Reference points on teeth and gingiva simulate areas most critical to an examination and treatment. These points enable an objective means to self-evaluate the body conditions and articulations that are most secure.

The “Skill Transfer” phase emphasizes that the acquired basic skills may be applied to clinical procedures such as oral examination, extraction, anesthesia, tooth cavity restoration, full denture construction, root canal treatment, crown preparation, casted partial denture procedures, etc. An imaginary vertical axis through the incisive embrasure of the patient’s central incisors is established from awareness of comfort and optimal use of human body during simulation.

This awareness is reinforced by the design of an orbiting operator support in the preferred equipment model, the Feel-Ease (Figure 1). The consistency of positional relationships provided through simulated clinical procedures is best transferred to daily clinical practices by maintaining the clinical setting the same as the pre-clinical setting. Therefore, any student who has difficulty in clinical practice should come back to the SATV skill acquisition phase repeatedly until he/she has more confidence. This process is similar to the experience of an airline pilot in a flight simulator. A new cockpit requires experience in a new simulator.

Figure 3 DentSim (by DENX)

Skill verification by means of multimedia CCD camera, digital/video records or data forms, and standardized simulated pathologies, of skill acquisition and transfer is used throughout the system. Green reference surfaces within simulated teeth enable an objective means to self-evaluate the accuracy of intraoral outcomes. These surfaces are embedded around simulated caries in the transfer phase. Once a procedure is finished the remaining overcut lines or marked surfaces and remaining caries are measured. The measurement of the transferred to patient care.

What is critically important in pre-clinical dental school experiences is that: 1) the student be given the opportunity to derive for her/himself the conditions s/he prefers to practice with for the rest of their career and 2) the student be given those environments to develop his/her skills. Currently, most dental schools in the United States are establishing simulator settings with little or no regard to proprioceptive derivation or self-modeling. A very popular modeling environment,DentSim (Figure. 3), offers digitally monitored simulated oral performance but places the student in a chair-mounted over

Figure 4 SATV Simulator (by Morita Corp)

the patient delivery system with no feedback for their body conditions. The best placement of dynamic instruments and the skills to use them are being ignored. Most dental schools emphasize product and not process. The dental student’s performance is left to trial and error with emulative examples, which are not the best way to acquire skill.

Japan, on the other hand, has included SATV training in the curriculum of 23 out of their 29 dental schools. Much of this attention is due to the presence of Dr. Beach in Japan and the local manufacturing of the

The performance of any physical task is compromised when the setting and instruments used do not allow balanced operating positions for peak function. 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.

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.

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

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.

Kadowaki and Kaneco have completed studies comparing the traditional tilting dental chair environment and a new technology and process of performing dentistry that stabilizes the operator and the patient in the most optimum relationship. It is evident from their statistics that the latter is a significantly less stressful and more efficient way to practice dentistry because it resulted in significant differences in a variety of measures used to assess dental practice efficiency and efficacy.

The average number of contacts during treatment on tray handles, light handles, finger switches, charts, operating stools, cabinets, gowns, clothes, and dental chair were reduced from an average of 36.2 per operation to 4.8 per operation with the newer design of delivery. The average number of hand or finger contacts for the assistant were similarly reduced from 46.0 in a dental chair environment to 9.5 in this new stabilized setting. Treatment area time analysis (average) revealed that the percent of treatment time without physical distortion or strain was increased from 39.7% to 98.7%. The percent of dentists reporting subjective musculoskeletal (MSK) symptoms ranged from 78% for those who stood to operate with the dental chair to 76% for those who reclined the dental chair and sat to operate. Only 8% of dentists surveyed who worked with the stabilized future type of delivery reported MSK symptoms. Finally, the time analysis in handling instruments indicated that there was a significant reduction in the average number of pick-ups and in the average time spent picking up instruments with tubing and hand instruments with this new system designed for the proprioceptive sense of the operator.

This new human-centered technology is a break with the past history of performing dentistry with the patient sitting in a reclining chair. It is the result of the life-long pursuit of a better way to practice dentistry by American dentist, Dr. Daryl Beach, of Osaka, Japan. This new system uses an environment that encourages natural human movements and promotes optimal performance of dentistry. The concepts and equipment design advocate a non-articulating support for the reclined patient. This design incorporates dynamic instrumentation at positions just forearms drop away at the shoulder of the patient’s support. The design has come to be called “the shoulder delivery type” in Japan were it outsells “the chair mount delivery type” two to one. Prototypes of a stabilized form of shoulder delivery equipment and instruments have been manufactured by the Morita Corporation in Kyoto, Japan since 1962. This stabilized design has had limited availability in countries outside of Japan.

This new concept of dental care is free of unnecessary distractions and gives the dentist, the assistant, and the patient the most optimum position and context for the activities that occur during dental treatment. The patient is offered a lying or full rest position for treatment. This positioning and a special headrest helps keep the patient’s mouth in a predictable position regardless of the patient’s height. The range of the operator’s support to the patient’s oral cavity constitutes an arc of approximately 120 degrees from behind the patient’s head. The center of this arc is the incisal embrasure of the patient’s maxillary central incisors. This imaginary vertical line is referred to as a skill

axis. The relationship of operator to patient is stabilized and consistently keeps the dentist in a full upright alert seated posture. The dentist’s upright posture allows the best control of the fine stabilized finger movements required when operating in the mouth and on the teeth. By stabilizing the position of the mouth and being able to easily reach necessary equipment and materials, the dentist and his assistants are able to work more accurately, more efficiently, and with less physical and mental wear and tear on both the patient and themselves. According to Dr. Beach, “Performance starts with the spine.” Maintaining the physiologic curves of the erect vertebral column transecting the center of gravity allows for maximum performance.

This stable relationship offers many other advantages over previous chair- based equipment systems. Currently, the treatment room has become a site for detached areas of technology. The addition of clinical microscopes, lasers, curing lights, air abrasion techniques, intraoral video, CAD CAM, root canal apex finders, sonic scalers, radiovisiography, pressure assisted anesthetic devices, separate dental unit water lines, and clinical computer systems has the future treatment room looking like a garage sale. The moving orientation of the head of the dental patient by traditional tilting dental chairs requires buttons, switches, wheels on cabinets and stools, folds, seams, tracks, computer processing of positions, robotics, long tubes, wires, hinged arms, movable lights, trays, and carts. There is a best posture and position to see and articulate the oral tissues. It is also a position from which all present and future technologies can relate and be delivered. The skill axis/oral surface interface is the most important point in the future dental office. Technology may be integrated into this type of treatment room with specifications that it must not intrude into space necessary for a stable and natural human to human interface.

When a dentist establishes routes in an oral procedure there have been limits to his/her maintaining balance due to previous equipment and instrument designs. Some of these specifications are the size and positioning of the headrest, dental mirror- handle angle and dimensions, and the errors induced by a fully adjustable and tilting system without a stable skill axis. The scooting of the operator stool in the attempt to position the operator appears to be an imperfect system for repetitive positioning. A new level of organization is now available with feel based equipment and instruments that relate the process of dental treatments to the dentist. Benefits of this new technology include:

1. Dramatic improvement in personal health and stamina
2. Increased confidence and security
3. Minimized physical stress while treating patients
4. Heightened awareness of precise operating control
5. Significantly improved ability to enhance productivity
6. Increased gentleness and patient comfort

Dentists have been performing dentistry essentially the same since the time and motion studies of the late 1960′s. The current dental student is still unable to consistently develop ways of limiting reach, articulations, and predictable presentations in the course of moving from one surface of a tooth to another because of the equipment and instruments their predecessors have modeled. The physical and mental health of dentists and hygienists have been strained and compromised based on available research. They often have limited themselves to “a peek in the mouth” instead of “a peak performance”. Their success at maintaining an unstrained posture has been mostly left up to personal trial and error in a tilting environment that always requires organization and postural accommodation. The dental chair has been a great contributor towards the performance of dental operations and much of our thinking for over a century. Manufactures have automated, configured, and flexed the “chair” until its concept has been exhausted based on the dental profession’s future needs. It is time to stop thinking in terms of “dental chairs”, “chair time”, and “chairside assistants” and to start thinking in terms of human needs.

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“Pd –The Key To Linkage of Skills, Settings and Technology–An Example of pd Linkage In Health Care”
Daryl Beach DMD, LAN Center, Osaka, Japan

Introduction

The industrial age produced a health care field that is heavily dependent on technology. It also produced a great demand for standards. This has resulted in accredited curriculums that produce licensed personnel from medical, dental, nursing, pharmaceutical and other schools. Also, with a concern for safety, national and international standards organizations have regulated or set standards for drugs, equipment, devices, health care settings and information.

On the other hand, standards for skills do not exist beyond the range of individual schools, hospitals or service organizations. While there is much interest in restoring the abilities or health of the human body, there has been little interest in determining optimum use of the human body for providing health care. Skill is simply identified as an ability to achieve desired outcomes with applications focused on various parts, functions, and disorders of the human body. This has led to a large variety of specialties which are recognized at the administrative levels of governments and schools. In these specialties the ability to achieve given outcomes with poorly designed instruments or in compromised settings is often seen as a useful test of skill. This credit was certainly indicated in the early industrial period, but today, overall, it has negative value for patients and all who support the health care field, since it delays progress in health care.

Specialty-based skills

Specialty-centered skills are identified with careers, settings or techniques. “What do you do?” “I am a surgeon.” “What kind of surgeon?” “Abdominal.” “Are you using laparoscopic technique?” “As much as possible.” With these questions we have captured the image of a person’s career, the setting of activity and an interest in a technique. How does a surgeon with skills based on use of scalpels, probing fingers and tying sutures transfer his/her skills to use of laparoscopes? How many patients are at risk of complications–not because of the laparoscopy technology, but because of the problems of acquiring or transferring skills that are based on manuals and emulation with trial and error?

This is only one example of change that is taking place throughout the field of health care due to rapid and costly testing and adoption of new technologies. Specialty-based skills are centered on what we can do with what we have now, what we are teaching now, or how our present “new” techniques compare with the past conditions of our specialty. From this point of view, we often see progressive changes mixed with retrogressive changes.

The following are problems of specialty centered skills;

• 1 Inability to differentiate skill problems from problems of settings or technology,
• 2 High cost and unnecessary risk to patients due to accommodation of specialty centered skills in the health care field,
• 3 Difficulty in acquiring and transferring skills due to lack of principle for procedure,
• 4 Inability to correlate use of one’s body with consistent accuracy in outcomes and productivity,
• 5 Confusion and needless stress for patients, providers, engineers, students and administrators due to the above mentioned problems.

Pd skill – Optimum use of the human body

Pd skill is acquired from derivations in open space with no preconceptions and then pd muscle memory sets are established and maintained in pd settings. Pd-based skill can cover all specialties now and in the future, while specialty-based skills reflect past habits and the use of dated technology associated with specialty techniques.

What is the key to linkage of skills, settings and technology? Wilfred Barlow, MD pointed out in his book, “The Alexander Principle,” that misuse of the neck results in misuse of the rest of the body, including the fingers, lower back, feet, jaws and eyes. The optimum use of the body begins with the use of the neck, from which we can proprioceptively derive the optimal use of remaining muscles of the body. The use of the neck can be specified for both resting conditions and purpose-oriented activities. It is not only the key for determination of skills, settings and human interface with technology, but it also affects musculo-skeletal health which, in turn, may affect the health of other organs.

Use of the neck can be analyzed from tracings of one or more points on the head in relation to other points on the body. Also EMGs and X-rays have been widely used, particularly in studies of neck-associated pain. After the parameters of the head-trunk relationship have been established for achieving a desired outcome, then the 0 locations and paths of motions of the remaining segments of the body can be traced with a high focus on finger points and instrument points. Accuracy of outcomes is highly measureable.

When should we be concerned with the use or misuse of the human body? We are concerned with it when consistent accuracy is required, when our judgments on skills, settings and technology affect the lives of many, and when we want to prevent or correct personal health problems caused by misuse of our bodies.

Conclusions

The study of human factors deals with the interface between human beings and settings. Today, especially in health care settings, human beings interface extensively with specialized treatment and information technology, often in the form of big machines. Human interface engineers must know the appropriate basis for human acts before specifying the human-setting/technology interfaces.

In summary:

• 1. Pd is the core of ergonomics.
• 2. Pd skill is needed for the field of health care.
• 3. Pd skill needs pd space, pd settings and pd technology.

Editors Note: Dr. Beach wrote the article above17 years ago. Today those practicing pd dentistry are more convinced that a principle of pd is needed in health care as we are experiencing a global financial adjustment that has illuminated waste and self-serving businesses. The public is witnessing the interface of an emerging survival-safety-health (SSH) economy with a group-personal choice economy that now seems to be leading to great waste of material resources and human energy recognized by world leaders. Commitment to human-centered standards in the dental industry and in dental clinics would be a demonstrable move toward the SSH economy. Patients want control of their bodies, safety for themselves, and to be reassured they are receiving the best care and the best care options for their health care dollars, insurance premiums, and taxes allocated for health care. Pd conditions can address these concerns in addition to being the core of ergonomics for safe musculoskeletal practice by the health care provider. The outcomes of applying pd result in skillful use of the body and ensure that human performance is measurable and verifiable. It reflects the essential principle of ergonomic functioning—using the least human effort and material resources needed for a procedure that does not contribute to body disorders, to errors in procedures, and to unacceptable outcomes due to fatigue, stress, and strain.