Chapter 25 Ergonomics Copyright 2003, Elsevier Science (USA). All rights reserved. No part of this product may be reproduced or transmitted in any form or by any means, electronic or mechanical, including input into or storage in any information system, without permission in writing from the publisher. PowerPoint® presentation slides may be displayed and may be reproduced in print form for instructional purposes only, provided a proper copyright notice appears on the last page of each print-out. Produced in the United States of America ISBN 0-7216-9770-4

Introduction Ergonomics deals with adaptation of the human body to the work environment. Ergonomic conditions are simply the safest, most efficient, and easiest way to work. The word “ergonomics” comes from the Greek words “ergon” (work) and “nomos” (laws of work). The goal of ergonomics is to help people stay healthy and at the same time perform their work more effectively by changing the design of the workplace, instruments, systems, products, training, or some combination of these elements.

Fig. 25-1 Ergonomic factors in dentistry.

Musculoskeletal Disorders Headaches, neck and shoulder pain, back pain, and carpal tunnel (wrist injuries) account for many disabling and potentially career-ending musculoskeletal disorders for dental professionals. Work habits, posture, and equipment and instrument design can contribute to these work-related disorders.

Ergonomics in the Dental Office Members of the dental team usually perform their work in a seated position, often use excessive motions, and have unbalanced postures. Work-related musculoskeletal disorders can range from back pain, joint pain, neck and shoulder pain, hand and wrist pain, and headaches. The early onset of pain should alert you that an imbalance exists, and if ignored, more serious damage can occur over time. It is important for the dental assistant to understand how to implement ergonomic changes and methods to prevent material safety data sheets (MSDS).

Risk Factors There are three interrelated factors that contribute to increased risk of job-related injury. These are: Posture Repetition Force

Posture Posture affects the ability of the dental assistant to reach, hold, and use the equipment. It also influences how long the dental assistant can perform a task without suffering adverse health effects. Over time, any position will eventually become fatiguing and may lead to lower back pain. Consider alternating assisting at chairside with other dental assistants in the office to give each other some variety in positions.

Posture- cont’d Establish a neutral position by sitting upright with your weight evenly distributed. Your legs should be separated with your feet flat on the chair footrest. Your back should be pressed against the back of the chair for lumbar support. Your hips should lean forward to rotate the pelvis backward. The properly aligned spine resembles a gentle “S.” When the spine is properly aligned, the ears, shoulders, and hips are in straight vertical alignment, providing balance, support, and equal distribution of weight.

Posture- cont’d While assisting the dentist, there is a tendency for the dental assistant to deviate from the neutral position. Examples of such deviations include leaning forward, twisting, overbending the back, and reaching. These poor postures can lead to aches, pains, numbness, and tingling. Ideally, alternate sitting and standing whenever possible.

Fig. 25-2 The dental assistant should sit on a chair with a lumbar support, not on a stool.

Reaching, Twisting, and Stretching Frequent reaching, twisting, and working with the arms in awkward positions can cause strains and sprains. Extreme stretching of muscles or ligaments causes strains, and sprains usually involve a sudden twist or wrenching of a joint with stretching or tearing of ligaments. Shoulder problems can be caused by repeatedly reaching behind the body for instruments or supplies.

Reaching, Twisting, and Stretching- cont’d Keep the air-water syringe, handpiece, saliva ejector, and high-volume oral evacuator so that they are within a “normal horizontal reach.” Keep the operatory light within a safe “maximum vertical reach.” Other supplies used less frequently should be placed within the “maximum horizontal reach.” Reaching behind your back and lifting can cause shoulder injury. When turning is necessary, rotate the chair rather than twisting your body.

Repetition and Force Repetitive motion, overflexing, and extension of the wrist can significantly increase the risk of cumulative trauma disorders (CDTs), particularly when the task requires force. To help prevent CDTs, it is recommended to take periodic breaks and alternate difficult procedures with less stressful procedures. A common CTD is carpal tunnel syndrome.

Fig. 25-3 Small pieces of equipment should be in a position that does not require twisting or bending. Fig. 25-3

Carpal Tunnel Sydrome The carpal tunnel refers to an anatomic area of the hand/wrist. With improper motions, the tendons swell and exert pressure on the median nerve. The first symptoms of carpal tunnel syndrome (CTS) is a painful tingling in one or both hands. A decreased ability and power to squeeze objects or make a tight fist may follow. In advanced cases, the thenar muscle (located at the base of the thumb) may weaken, causing a feeling of decreased strength in the hand grip.

Fig. 25-5 A, Cross section of wrist Fig. 25-5 A, Cross section of wrist. B, Schematic view of the carpal tunnel (samples attached). Fig. 25-5

Fig. 25-4 The bend in the wrist can lead to carpal tendon injury over long period.

Carpal Tunnel Sydrome- cont’d Other repetitive hand and wrist movements such as knitting, gardening, or keyboard use can also cause CTS. The use of ambidextrous gloves (gloves that are worn on either hand) can place excessive tension on the thenar eminence (the fleshy elevation of the palm side of the hand) by forcing the hand to work against the vertical alignment of the glove form. Right-left gloves that are properly sized support the hand in a natural position, which properly positions the thumb, index finger, and middle finger.

Fig. 25-6 Gloved hand showing hypothenar eminence.

Body Strengthening Exercises Stretching and strengthening the muscles that support the back and neck and those used in the forearm, wrist, and hand will help them remain strong and healthy. You can do periodic stretching throughout the workday. Before beginning any exercise program, you should check with your physician, particularly if you experience pain with any of the movements.

Hand Exercises Resting hands frequently is believed to be one of the most important factors in preventing CTS. Use the following exercises to stretch and relax the muscles in the hand.

Fig. 25-7 A and B, Slowly open and close your hands from a completely open position to a completely closed position, which ends with your fingers tucked into your palm. Fig. 25-7 A & B

Fig. 25-7 C, Press the palms of your hands together and then relax them.

Fig. 25-7 D, Gently pull and relax each finger on each hand separately.

Fig. 25-7 E, Cross the wrists and gently stretch and relax.

Eye Exercises To relieve eyestrain caused by focusing intensely at one depth of vision for long periods, look up from the task and focus your eyes at a distance for approximately 20 seconds. Practice this frequently throughout the day to use your full range of vision and lessen eyestrain.

Back Exercises To relieve stresses placed on the back, neck, and shoulders, try the full back release. Let the head move down slowly and allow the arms and head to fall between the knees; hold for a few seconds, then raise slowly by contracting the stomach muscles and rolling up. Bring the head up last.

Fig. 25-8 Full back release. Fig. 25-8

Neck Exercises Try head rotations for neck stiffness. Head rotations involve tilting the head from right to left, as well as forward and backwards, without forcing the motion beyond a range of comfort.

Shoulder Exercises Shoulder shrugging can be used to stretch the shoulder muscles that may be stressed from holding oral evacuators, instruments, and telephone handsets. Pull the shoulders up toward the ears, roll them backward and then forward in a circular motion.

Fig. 25-9 Shoulder shrugging.