Peak Pinch Force Research Articles

Decoding the ergonomics in the new normal for dentistry: A narrative review

Focus and precision are the sine qua non of dentistry, wherein the routine tasks require a peak pinch force and results in finger fatigue and cumulative trauma disorders combined with impaired vision. Dentists’ posture is treated with great care and oft repeated in Ergonomics, studied in undergraduate courses and the continuing education courses, though many still do not know the subject well enough. The study selection was done upon selecting the dental surgeons, hygienists, assistant working on their patients and included the findings relating to practice environment. The electronically searched sources until 2021 were the MEDLINE Pub med, EMBASE, Wiley Online Library, Science direct, American Dental Association (ADA) website and Google Scholar. An additional manual search and queries with cross-reference yielded around fifty studies ultimately. The International Ergonomic Association (IEA) recognized certain domains long ago and its noteworthy application for dental office is set forth in the present review. Ergo-dentistry may come to be realized as a new essential in the new normal for our profession. Evidence echoes that dentists are at risk for developing health problems, particularly the musculoskeletal disorders and impaired vision. Beyond doubt, a healthy dentist is a pre-requisite for a successful dental practice. Ergodontics is the key to keep check on the same and following its core principles is essential.

Effects of the Surface Texture and Weight of a Pinch Apparatus on the Reliability and Validity of a Hand Sensorimotor Control Assessment

ObjectivesTo investigate the reliability and validity of a modified pinch apparatus devised with 3 surface textures and 2 different weights for clinical application. DesignCase-controlled study. SettingA university hospital. ParticipantsThe participants (N=32) included carpal tunnel syndrome (CTS) patients (n=16) with 20 sensory neuropathy hands, and an equal number of age-sex matched volunteers without CTS, as well as young volunteers without CTS (n=16 with 20 hands) used to analyze both the testing validity and reliability of the modified device. InterventionsNot applicable. Main Outcome MeasuresThe Semmes-Weinstein monofilament (SWM) and two-point discrimination (2PD) tests were conducted, and the force ratio between the FPpeak (peak pinch force during lifting phase) and FLmax (maximum load force at maximum upward acceleration onset) detected from a pinch-holding-up activity (PHUA) under various testing conditions was obtained. ResultsThe range of the intraclass correlation coefficient of this pinch device was 0.369-0.952. The CTS patients exhibited poorer force modulation ability according to the inertial change in a dynamic lifting task when compared to the controls under all testing conditions (P<.001). The area under the receiver operating characteristic force ratio curve was 0.841, revealing high accuracy of the test for diagnosing CTS neuropathic hands under the testing condition in which the 125-g coarse texture device was used. In addition, the weight factor was shown to have significant effects on the sensitivity and accuracy of the PHUA assessment. ConclusionsThis study showed that the PHUA test via the modified pinch apparatus is a sensitive tool that can be used in clinical practice for detecting neuropathic CTS hands. In addition, changing the weight of the pinch device has a significant effect on the sensitivity and accuracy of the PHUA assessment.

Feasibility of a Novel Functional Sensibility Test as an Assisted Examination for Determining Precision Pinch Performance in Patients with Carpal Tunnel Syndrome

To understand the feasibility of a novel functional sensibility test for determining precision pinch performance in patients with carpal tunnel syndrome, this study investigates the validity, sensitivity and specificity of functional sensibility derived from a pinch-holding-up activity (PHUA) test. Participants include 70 clinically defined carpal tunnel syndrome (CTS) patients with 119 involved hands and 70 age- and gender-matched controls. To examine the discriminating ability of the functional sensibility test, the differences in the ability of pinch force adjustments to the inertial load of handling object between CTS and control subjects are analyzed. The results of functional sensibility are correlated with the severity of CTS to establish concurrent validity. The receiver operating characteristic (ROC) curve is constructed to demonstrate the accuracy of the proposed test. The functional sensibility score significantly discriminates the patients and control groups (respectively, 12.94±1.72 vs. 11.51±1.15N in peak pinch force (FPPeak), p<0.001; 2.92±0.41 vs. 2.52±0.24 in force ratio, p<0.001) and is moderately correlated (r = 0.42–0.54, p<0.001) with the results of traditional sensibility tests (touch-pressure threshold and two-point discrimination test). In addition, there is a statistical difference in the results of functional sensibility (p<0.001) among the subgroups of CTS severity based on electrophysiological study. The sensitivity and specificity are 0.79 and 0.76, respectively, for the functional sensibility test. The areas under the ROC curve are 0.85 and 0.80 for the force ratio and FPPeak, respectively. In conclusion, the functional sensibility test could be feasibly used as a clinical tool for determining both the sensibility and precision pinch performance of hands for the patients with CTS.

Setup of a Novel Biofeedback Prototype for Sensorimotor Control of the Hand and Preliminary Application in Patients With Peripheral Nerve Injuries

Biofeedback training is widely used for rehabilitative intervention in patients with central or peripheral nervous impairment to train correct movement patterns; however, no biofeedback apparatus is currently available to correct pinch force ratios for patients with sensory deficiencies. A cross-sectional and longitudinal design was used in an observational measurement study for establishing a prototype and to determine the effects of biofeedback intervention, respectively. This study aimed to develop a computerized evaluation and re-education biofeedback (CERB) prototype for application in clinical settings. A CERB prototype was developed integrating pinch apparatus hardware, a biofeedback user-controlled interface, and a data processing/analysis interface to detect momentary pinch performances in 79 people with normal hand sensation. Nine patients with hand sensory impairments were recruited to investigate the effects of training hand function with the CERB prototype. Hand dominance, pinch pattern, and age significantly affected the peak pinch force and force ratio for lifting a 480-g object with a steel surface. In the case of the 79 volunteers with normal hand sensation, hand dominance affected the time lag between peak pinch force and maximum load; however, it was unaffected by pinch pattern or age. Training with the CERB prototype produced significant improvements in force ratio and better performance in the pin insertion subtests, although the results for both 2-point discriminative and Semmes-Weinstein monofilament tests did not change significantly. The intervention findings are preliminary. This study developed a conjunct system suited for evaluating and restoring sensorimotor function for patients with impaired hand sensibility. The results from the participants with normal hand sensation could serve as a reference database for comparison with patients with nerve injuries.

Clinical application of computerized evaluation and re-education biofeedback prototype for sensorimotor control of the hand in stroke patients

BackgroundHemianaesthesia patients usually exhibit awkward and inefficient finger movements of the affected hands. Conventionally, most interventions emphasize the improvement of motor deficits, but rarely address sensory capability and sensorimotor control following stroke. Thus it is critical for stroke patients with sensory problems to incorporate appropriate strategies for dealing with sensory impairment, into traditional hand function rehabilitation programs. In this study, we used a custom-designed computerized evaluation and re-education biofeedback (CERB) prototype to analyze hand grasp performances, and monitor the training effects on hand coordination for stroke patients with sensory disturbance and without motor deficiency.MethodsThe CERB prototype was constructed to detect momentary pinch force modulation for 14 sub-acute and chronic stroke patients with sensory deficiency and 14 healthy controls. The other ten chronic stroke patients (ranges of stroke period: 6–60 months) were recruited to investigate the effects of 4-weeks computerized biofeedback treatments on the hand control ability. The biofeedback procedures provide visual and auditory cues to the participants when the interactive force of hand-to-object exceeded the target latitude in a pinch-up-holding task to trigger optimal motor strategy. Follow-up measurements were conducted one month after training. The hand sensibility, grip forces and results of hand functional tests were recorded and analyzed.ResultsThe affected hands of the 14 predominant sensory stroke patients exhibited statistically significant elevation in the magnitude of peak pinch force (p = 0.033) in pinching and lifting-up tasks, and poor results for hand function tests (p = 0.005) than sound hands did. In addition, the sound hands of patients were less efficient in force modulation (p = 0.009) than the hands of healthy subjects were. Training with the biofeedback system produced significant improvements in grip force modulation (p = 0.020) and better performances in the subtests of pin insertion (p = 0.019), and lifting of lightweight objects (p = 0.005).ConclusionsThe CERB prototype can provide momentary and interactive information for quantitative assessing and re-educating force modulation appropriately for stroke patients with sensory deficits. Furthermore, the patients could transfer the learned strategy to improve hand function.

Correlation of digital sensibility and precision of pinch force modulation in patients with nerve repair

The outcome measures for patients following peripheral nerve repairs commonly include muscle strength and sensory assessments. However, no significant discussion exists on the impact of nerve injury on sensorimotor control. The objective of this longitudinal study was to explore the effects of nerve regeneration on the control of pinch force in executing functional tasks. Seven patients with digital or median nerve repairs were assessed by a custom-designed pinch device and conventional sensory tools at monthly intervals following nerve repair. These tools measured sensibility, maximum pinch strength, and anticipated pinch force adjustments to movement-induced load fluctuations in a pinch-holding-up activity (PHUA). Six force-related and temporal parameters for sensory measurement were used to determine improvements in pinch performance over time following sensory recovery. The results revealed significant differences in the parameters of peak pinch force, baseline pinch force, force ratio, and the percentage of maximal pinch force output at different points in the course of nerve regeneration. A strong relationship was also found between kinetic data from the PHUA test and the traditional sensibility tests for the nerve repair patients in the present study.

Functional sensibility assessment. part II: Effects of sensory improvement on precise pinch force modulation after transverse carpal tunnel release

Patients with median nerve compression at the carpal tunnel often have poor sensory afferents. Without adequate sensory modulation control, these patients frequently exhibit clumsy performance and excessive force output in the affected hand. We analyzed precision grip function after the sensory recovery of patients with carpal tunnel syndrome (CTS) who underwent carpal tunnel release (CTR). Thirteen CTS patients were evaluated using a custom-designed pinch device and conventional sensory tools before and after CTR to measure sensibility, maximum pinch strength, and anticipated pinch force adjustments to movement-induced load fluctuations in a pinch-holding-up activity. Based on these tests, five force-related parameters and sensory measurements were used to determine improvements in pinch performance after sensory recovery. The force ratio between the exerted pinch force and maximum load force of the lifting object was used to determine pinch force coordination and to prove that CTR enabled precision motor output. The magnitude of peak pinch force indicated an economic force output during manipulations following CTR. The peak pinch force, force ratio, and percentage of maximum pinch force also demonstrated a moderate correlation with the Semmes-Weinstein test. Analysis of these tests revealed that improved sensory function helped restore patients' performance in precise pinch force control evaluations. These results suggest that sensory information plays an important role in adjusting balanced force output in dexterous manipulation.

Functional sensibility assessment. Part I: develop a reliable apparatus to assess momentary pinch force control

A precise magnitude and timing control of pinch performance is based on accurate feed-forward and feedback control mechanisms. Ratio of peak pinch force and maximum load force during a functional performance is a sensitive parameter to reflect the ability to scale pinch force output according to actual loads. A pinch apparatus was constructed to detect momentary pinch force modulation of 20 subjects with normal hand sensation. The results indicated high intra-class correlation coefficient and small coefficient of variation of the detected force ratio among three repeated tests, which represented that the stability test of the measured response confirmed the feasibility of this apparatus. The force ratio for a 480 g object with a steel surface ranged between 1.77 and 1.98. Normal subjects were able to scale and contribute pinch force precisely to a pinch-holding-up test. This study may provide clinicians a reliable apparatus and method to analyze the recovery of functional sensibility in patients with nerve injuries.

Evaluation of Distal Upper Extremity Musculoskeletal Load During Routine Colonoscopy

Background: Physicians who perform endoscopies are at increased risk for developing recurrent thumb, hand, elbow and low back pain. Musculoskeletal disorders of the upper extremities are related to repeated, forceful movements of the hands and arms. As the demand for colonoscopy increases, so will the physical loads on the hands and arms of endoscopists. The risk factors of upper extremity overuse injuries during routine endoscopy, such as applied pinch force and muscle loads, have not been evaluated during routine endoscopy. We performed a pilot study to determine right thumb pinch force and hand and wrist muscle activities during colonoscopy. Methods: Three gastroenterologists were studied while each performed three colonoscopies. Electromyographic (EMG) activity of the right and left forearm extensor carpi radialis (ECR), right and left flexor digitorum superficialis (FDR), and left abductor pollicis longus (APL) was measured with surface electrodes. Summary measures of EMG data were calculated using the amplitude probability distribution function (APDF), which is a method to quantify muscular activity by normalizing it to maximum voluntary contraction (MVC). Prior studies have shown median levels of muscle activity (APDF 50%tile) of >7-20% MVC and low levels of muscle activity (APDF 10%ile) of >2-5% MVC are associated with increased risk of injury. Right thumb pinch force was measured using a thin profile, custom designed pressure sensor. Prior studies have shown peak pinch force levels (APDF 90%tile) of >10N are associated with an increased risk of injury. Results: The mean peak pinch force across the 9 patients (APDF 90) was 8.6N (SD ± 2.1). The highest pinch forces occurred during insertion: APDF 90 = 10.4N in the left colon and APDF 90 = 10.1N in the right colon. The highest muscle activities were observed in the left ECR (APDF 10 = 10% MVC and APDF 50 = 20% MVC). Left ECR activity was greatest during insertion into the left colon (APDF 10 = 9.0%, APDF 50 = 25.1%) and right colon (APDF 10 = 11.4%, APDF 50 = 23.9%). APDF 10 values of the other muscle groups studied did not exceed 5% of MVC, and APDF 50 values did not exceed 20% of MVC. Conclusions: Based on this pilot data, colonoscopy is associated with a borderline risk of musculoskeletal disorders of the upper extremities, specifically right thumb and left wrist extensor injury. Repeated, high thumb pinch forces can lead to DeQuervain's tendinitis and carpal tunnel syndrome. Repeated, high left ECR muscle loads can lead to second and third extensor compartment tenosynovitis at the wrist and epicondylitis. Further study is needed to identify modifiable risk factors and evaluate methods to reduce this risk.

Pinch Forces and Instrument Tip Forces During Periodontal Scaling

The prevalence of upper-extremity musculoskeletal disorders, such as tendinitis, is elevated among dental practitioners. An important risk factor for these disorders is forceful pinching; however, the pinch forces and instrument forces during scaling are unknown. Six dentists and six senior-year dental students were recruited to use an instrumented periodontal scaler to perform their usual dental scaling work on patients. Thumb pinch force was measured by a pressure sensor, whereas the forces developed at the instrument tip were measured by a six-axis load cell. Dental students applied greater mean peak pinch force (35.7 +/- 3.8 N) compared to dentists (24.5 +/- 4.1 N) (P = 0.001). On the other hand, the peak forces generated at the instrument tip, which were directly related to the productivity of the dental scaling task, were higher among the dentists. The application of pinch force by dentists was related to the required scaling forces, whereas students applied excessive pinch force to the tools. Increased experience in periodontal scaling leads to the application of less pinch force to accomplish scaling. Nonetheless, the applied peak pinch forces in both groups are high and may pose a risk for the development of musculoskeletal disorders of the distal upper extremity.

A biomechanical analysis of applied pinch force during periodontal scaling

One of the factors associated with the high prevalence of upper extremity musculoskeletal disorders, such as carpal tunnel syndrome, among dental practitioners is the repeated high pinch force applied during periodontal scaling. The goal of this study was to determine the relationship between the pinch force applied during periodontal scaling and the forces generated at the tip of the tool. A linear biomechanical model that incorporated tool reaction forces and a calculated safety margin was created to predict the pinch force applied by experienced and inexperienced dentists during periodontal scaling. Six dentists and six dental students used an instrumented scaling tool while performing periodontal scaling on patients. Thumb pinch force was measured by a pressure sensor, while the forces developed at the instrument tip were measured by a six-axis load cell. A biomechanical model was used to calculate a safety factor and to predict the applied pinch force. For experienced dentists, the model was moderately successful in predicting pinch force ( R 2 = 0.59 ). For inexperienced dentists, the model failed to predict peak pinch force ( R 2 = 0.01 ). The mean safety margin was higher for inexperienced (4.88±1.58) than experienced (3.35±0.55) dentists, suggesting that students apply excessive force during scaling.

Pinch Forces and Instrument Tip Forces during Periodontal Scaling

The prevalence of upper extremity musculoskeletal disorders, including carpal tunnel syndrome (CTS), are elevated among dental practitioners, especially dental hygienists. An important risk factor for these disorders is forceful pinching; however, the pinch forces and instrument forces during scaling are unknown. Six dentists and 6 senior-year dental students were recruited to use a specially designed instrument while performing their usual dental scaling on patients. Thumb pinch force was measured by a pressure sensor, while the forces developed at the instrument tip were measured by a 6-axis load cell. Dental students applied greater mean peak pinch force (35.7 ± 3.8 N) compared to dentists (24.5 ± 4.1 N) (p = 0.001). The peak forces generated at the instrument tip were higher among the dentists. Increased experience in periodontal scaling leads to the application of less pinch force to accomplish scaling. Nonetheless, the applied peak pinch forces in both groups are high and pose a risk for the development of musculoskeletal disorder of the distal upper extremity.

The Effects of Forearm Posture, Wrist Posture, Gender, and Hand on Three Peak Pinch Force Types

In many industries the hand is utilized as a fixture, pinching in various wrist postures and forearm postures. In an effort to quantify the effects of wrist posture, forearm posture, gender, and dominant/non-dominant hand upon three peak pinch forces, a study was performed. Three pinch types were tested in this study: index pad pinch, middle pad pinch, and three-jaw chuck pinch force. For each pinch exertion condition, one of five wrist postures were employed: neutral, 45° extension, 65° extension, 45° flexion, and 65° flexion. Each pinch was also performed in one of three forearm postures: neutral, full pronation, and full supination. Ten subjects between 20–25 years of age within each gender category were tested giving a total of 20 subjects. Each subject was asked to build up to his or her maximal voluntary contraction using a modified Caldwell regimen, and hold that pinch level for three seconds. Results were analyzed using analysis of variance (ANOVA) with significant effects (gender, hand, pinch type, wrist posture, and forearm posture) tested using post hoc analysis. The results and their implications are discussed.