/home/opencode/cpanel/stomaeduj_hacked/uploads/art-5-1-21.pdf DENTAL ERGONOMICS www.stomaeduj.com A STANDARDIZED METHOD TO DETERMINE THE PROPER Original Articles WORKING DISTANCE FOR DENTAL MAGNIFICATION UTILIZING NEUTRAL ERGONOMICS POSITIONING Hind S. Hussein1a , Shelby Anderson1b , Melissa Matick1c , Avery Greene1d , Mark P. Zmiyiwsky1e , Nader F. Abdulhameed1f* 1Restorative Dentistry Department, School of Dental Medicine, Lake Erie College of Osteopathic Medicine, Bradenton, Florida, USA a BDS, Assistant Professor; email: Hhussein@lecom.edu; ORCIDiD: https://orcid.org/0000-0003-2850-3825 b DMD Student; email: SAnderson24575@dmd.lecom.edu; ORCIDiD: https://orcid.org/0000-0002-6461-6651 c DMD Student; email: MMatick37605@dmd.lecom.edu; ORCIDiD: https://orcid.org/0000-0001-7045-7055 d DMD Student; email: AGreene91477@dmd.lecom.edu; ORCIDiD: https://orcid.org/0000-0002-4636-7364 e DDS. MSBE, Assistant Professor; email: MZmiyiwsky@lecom.edu; ORCIDiD: https://orcid.org/0000-0002-1542-0302 f BDS. MS.PhD, Assistant Professor; email: Nabdulhameed@lecom.edu; ORCIDiD: https://orcid.org/0000-0001-8137-2495 ABSTRACT https://doi.org/10.25241/stomaeduj.2021.8(1).art. 5 Introduction Evaluate and compare the relationship between anatomic measurements of the dental clinician in a neutral ergonomics position with the proper working distance and test the hypothesis that working distance can be estimated using specific anatomical measurements of the operator. Materials and Methods Specific measurements were obtained from 134 participants utilizing a neutral ergonomics position. Values were applied using the Pythagorean theorem to calculate a hypothesized working distance (HWD) from lateral epicanthus (E) to antecubital fossa (F) and antecubital fossa to the tip of the thumb (T). The actual working distance (ET) was measured from lateral epicanthus to tip of the thumb in a neutral ergonomics position in a simulated setting. Results The results showed a significant positive correlation between (ET) and (HWD) and a positive correlation for all of the anatomic measurements taken in simulation: ET to height and HWD to height; (EF) and ET, EF and HWD; antecubital fossa to the thumb (FT) and ET, FT and HWD (p<0.00). There was a marginally significant difference when comparing vision types, corrective and non- corrective (p<0.058), with non- corrective vision having a higher actual working distance. There was a statistical difference when comparing gender and HWD with male participants ranking higher hypothesized and actual working distance. Conclusion When applying the Pythagorean formula using anatomic landmark measurements, the HWD is repeatable for most operators and may contribute to a more standardized method to measure the accurate working distance that fits the ergonomics. KEYWORDS Ergonomics; Dental Education; Musculoskeletal Disorders; Dentist; Dental Hygienists. 1. INTRODUCTION and clinicians may not be aware of what constitutes the correct ergonomics posture. The importance of Proper ergonomics in dentistry have been viewed an early introduction to proper ergonomics may be as contributory aspects in the prevention of beneficial to a clinician’s career, for both comfort and musculoskeletal injury and the working distance longevity. The cause of musculoskeletal disorders with magnification should allow the operator to (MSD) is multifactorial and can develop from as little maintain optimum posture [1]. Many dental students as a single event, or more likely through repetitive OPEN ACCESS This is an Open Access article under the CC BY-NC 4.0 license. Peer-Reviewed Article Citation: Hussein HS, Anderson S, Matick M, Greene A, Zmiyiwsky MP, Abdulhameed NF. A standardized method to determine the proper working distance for dental magnification utilizing neutral ergonomics positioning. Stoma Edu J. 2021;8(1):45-51. Received: January 19, 2021; Revised: February 18, 2021; Accepted: February 23, 2021; Published: February 25, 2021 *Corresponding author: Dr. Nader F. Abdulhameed, BDS, MS, PhD, Assistant Professor Restorative Dentistry Department, LECOM School of Dental Medicine, Lake Erie College of Osteopathic Medicine 4800 Lakewood Ranch Blvd, Bradenton, FL 34211 USA Tel: (941) 405-1508; Fax: (941) 405-1675; e-mail: nabdulhameed@lecom.edu Copyright: © 2021 the Editorial Council for the Stomatology Edu Journal. Stoma Edu J. 2021;8(1): 45-51 pISSN 2360-2406; eISSN 2502-0285 45 Hussein HS, et al. www.stomaeduj.com Original Articles Figure 1. Clinical position based on Module 1 Section 3 of Fundamentals of periodontal instrumentation and advanced root instrumentation. 8th edition revised by Gehrig JS, Sroda R, Saccuzzo D. Philadelphia, PA: Wolters Kluwer; 2019. A B Figure 2. The theorem application: a) The Pythagorean theorem is the formula for calculating the length of one side of a right-angled triangle (c) when the length of the other two sides is known: a2 + b2 = c2. In this formula, c represents the hypothesized working distance, a represents the distance from “Eye to Elbow” and b represents the distance from Elbow to Tooth; b) Investigational theorem application performed on the researcher. occupational movements over time. However, Council on Dental Practice’s (CDP) Dental Wellness risks for the development of MSD have been Advisory Committee (DWAC), in conjunction with the identified among dental students with reports of ADA Health Policy Institute, stress proper diligence pain in the back and neck regions during training when choosing loupes and the importance of the [2]. In an earlier study on the prevalence of body magnification level, working length, field of view, pain in a dental student population, 46-71% and the angle of declination in order to maintain of students reported pain with the percentage good head and neck posture [6]. Measurements are increasing with the increase of years in school [3]. individualized and unique to the clinician. The prevalence of musculoskeletal disorders in Magnification can allow the clinician to better visu- the dentist’s necks, backs, shoulders, and arms alize the oral cavity and to reinforce the maintenance were higher than other areas of the body; inter- of neutral ergonomics.The use of dental magnification vention with magnification helped to improve the in dentistry is widely utilized and continued efforts to working conditions reducing discomfort for the support its role in maintaining work posture remains clinicians [4]. Those who reported the regular use an area of study. Employing magnification loupes of some type of magnification were significantly has led to a reduction in the intensity of discomfort less likely to report MSDs compared to those who felt by dentists in areas of the “neck, shoulders and used magnification occasionally or never [5]. There arms, back, elbow, forearm and the whole body” is a general acceptance of the use of magnification [4]. Magnification increases a clinician’s visual acuity by dental students and practitioners and it is widely within the oral cavity and allows the clinician to see perceived as an adjunct, if not a standard, for dental detail without compensating with improper bending care in the profession. Recommendations by The or positioning. If magnification is to be considered 46 Stoma Edu J. 2021;8(1): 45-51 pISSN 2360-2406; eISSN 2502-0285 Dental magnification working distance and ergonomic www.stomaeduj.com Original Articles Table 1. Data Collection Criteria. Participant’s Age: Do not wish to Participant’s Gender: Male Female answer D1 D2 D3 Faculty Participant’s Educational Status: Handedness Right Left Standing Height (inch) Do you wear glasses/contacts? Lasik or related Yes No procedure? EF lateral epicanthus of the eye to mid-elbow fold (inch) FT The mid-elbow fold of the cubital fossa to the tip of thumb and or to occlusal surface #19 or #30 (inch) ET Working distance without loupes lateral epicanthus eye to typodont mandibular molar (inch) Table 2. Correlation significance test. since it reflects an individual length impacted by an operator’s characteristics and the ability to maintain Pearson Sig. r statistic proper ergonomics while working. Maintaining Correlation (2-tailed) proper ergonomics can be found in the curriculum ET vs HWD 0.878 0.000 Significant of dental education as provided in a guide to neutral ET vs Height 0 .741 0.000 Significant ergonomics [8]. Improper measurements may allow for awkward static positions and forward bending. HWD vs Height 0.847 0.000 Significant Studies have indicated that participants expressed EF vs ET 0.854 0.000 Significant that loupes resulted in better vision, more comfort, EF vs HWD 0.956 0.000 Significant a positive change in work posture [7], and improved working conditions that facilitated their work [4]. FT vs ET 0.732 0.000 Significant Of the current research available, emphasis on FT vs HWD 0.862 0.000 Significant achieving the proper individualized working distan- *Correlation is significant at the 0.01 level (2-tailed). ce is scarce and further research is warranted to determine how an individual’s characteristics may an element in maintaining proper ergonomics, the influence the necessary working distance for ideal working distance with magnification cannot proper ergonomics positions in the selection of be ignored. The necessary working distance needed magnification loupes. with magnification was credited with contributing to The following null hypotheses were tested: the positive effect and improvement among dental 1) There is a direct relationship between the specific students by reinforcing the maintenance of proper anatomical measurements of a dental operator while ergonomics for the head, neck, and trunk [7]. in neutral ergonomics position and a mathematical As only one adjunct to achieving this goal, dental determination of proper working distance which magnification has its many intricacies within can be obtained itself. Proper alignment of declination angle and 2) No difference in working distance between the working distance can be viewed as essential in corrective and non-corrective vision groups, and affirming this contribution. Working distance 3) No difference in working distance between gen- measurements may be more variable, depending ders. on how the measurements are taken and obtained. Although the ideal working distance needed can 2. MATERIALS AND METHODS fall within a range dependent on the magnitude of magnification (ie: 2.5x, 3.0x, 3.5x.etc), the working Participants were recruited through LECOM School distance measurement/ focus point in this range of Dental Medicine by email invitation after getting may vary. A standard to obtain the most optimal the IRB approval for the study protocol. All D1, D2, measurement to help minimize the variation may and D3 students were asked to participate in the be applicable and helpful in determining an ideal study. In addition, the dental faculty were invited working distance specific for an individual. to participate. Invitation to participate was not The working distance is measured from the clinician’s extended to the D4 students since their curriculum eyes to the operating site. It is of critical importance places them in outreach clinics of distant locations. Stoma Edu J. 2021;8(1): 45-51 pISSN 2360-2406; eISSN 2502-0285 47 Hussein HS, et al. www.stomaeduj.com Participants were screened for exclusion factors - Step 7: Stabilize the lower back by pulling in the Original Articles such as current musculoskeletal distress or injury stomach muscles to the spine. preventing them from maintaining a comfortable - Step 8: Relax shoulders down and back. ergonomics position. The exclusion characteristics - Step 9: Position arms along the long axis of the tor- were not recorded. Experimental sessions took place so and hold elbows near the body. in the LECOM Simulation clinic during open sim lab Student investigators and the principal investigator hours. Upon completion of the informed consent, observed and verbally instructed changes in the following demographic information was ergonomics keeping in mind the following reco- recorded (Table 1): age, gender, height, handedness, mmendations: educational year, and whether the subject wears - Head tilt of 0 to 20 degrees - Trunk flexion of 0 to 20 degrees Figure 3. Strong linear correlation between HWD and ET. Distance in - Torso in line with the long axis of the body inches. - Shoulders in a horizontal line 25 - Elbows at waist level held slightly away from the 24 body, no greater than 20 degrees from the body 23 - Forearm position held parallel to the floor, the angle Distance in inches 22 between 100 degrees and 60 degrees - Wrist aligned with a forearm; little finger-side of 21 the palm is slightly lower than the thumb side of the 20 palm. 19 Once neutral ergonomics were achieved and confir- 18 WD mean Corrective Non-Corrective Female Male med by the investigators, the participant was asked to ET HWD 21.7 22.6 21.4 22.4 22 23.1 20.7 21.6 22.5 23.6 maintain this position while focusing on the occlusal Groups surface of tooth 46 within the mannequin for right- ET HWD handed participants and the occlusal surface of 36 Figure 4. Group descriptive statistics. for left-handed participants. For every experimental session, a minimum of three investigators were contacts, glasses, or has had any corrected vision present to assist in measuring and recording the operation. The measurements were collected data. Three measurements were recorded: with a right-angle square and measuring tape in 1) EF: From the lateral epicanthus of the eye to the inches which can measure up to one eighth of the mid-elbow fold of the cubital fossa. inch. Following demographic data collection, the 2) FT: From the mid-elbow fold of the cubital fossa to participant was seated at a simulation station and the tip of the thumb and or to the occlusal surface instructed to assume the 9 o’clock position for right- of #46 for right-handed participants and #36 for left- handed participants and 3 o’clock for left-handed handed participants. participants. The participant was given safety 3) ET: From the lateral epicanthus of the eye to the goggles to wear for the duration of the experimental typodont lower molar. The right-angle square was session. The participant was asked by the student used to help maintain an angle consistent with our investigator and principal investigator to adjust proposed hypotheses in the equation and record the mannequin’s head to be at waist level. The measurements from EF and FT. A measuring tape participant was instructed into neutral ergonomics was used to measure the observed working distance based on Module 1 Section 3 of Fundamentals while the participant maintained an ergonomics of periodontal instrumentation and advanced position. The investigator notified the participant root instrumentation. 8th edition revised by when the working distance measurement was initia- Gehrig JS, Sroda R, Saccuzzo D. Philadelphia, PA: ted and completed. A student investigator recorded Wolters Kluwer; 2019. (Fig. 1). the participant’s demographics on a password- - Step 1: Place buttock back in the chair with even protected computer within a password protected distribution on the seat. flash drive. - Step 2: Adjust chair height so that feet rest flat on Using the Pythagorean theorem (Fig. 2) EF measu- the floor. Spread feet to shoulders width apart and rements were used to represent (a), FT measurements directly in front of the hips. were used to represent (b), and (c) was solved as our - Step 3: Tilt the seat until the back edge is one inch HWD in the formula and recorded. higher than the front edge or utilize a wedge-shaped ergonomics cushion. 2.1. The participant was informed of the following - Step 4: Adjust the lumbar rest so the lower back is risks: supported when the buttock is back in the chair. According to the Institutional Review Board (IRB) - Step 5: Adjust lumbar rest so that the height supp- protocol, the participant was asked to maintain a orts your natural curve. neutral ergonomics position for approximately up to - Step 6: Raise the tail bone to establish correct spinal five minutes. The participant was informed that they curvature. may experience minimal muscle soreness during 48 Stoma Edu J. 2021;8(1): 45-51 pISSN 2360-2406; eISSN 2502-0285 Dental magnification working distance and ergonomic www.stomaeduj.com or after the measurement session. To minimize this ergonomics and the use of magnification. Our Original Articles risk the participant was informed of their right to study does not attempt to explain the comparative stop the session at any time. We asked participants effectiveness of different styles of magnification [9], to verbally announce muscle soreness during the but to provide an emphasis on the proper working session to both student researchers and verify that distance in conjunction with magnification. Neutral the position we measured from was comfortable. If ergonomics is described as having the shoulders the participant could not continue the session the parallel with the floor, elbows close to the sides, and previously recorded information would be discarded. the patient’s mouth at elbow height of the clinician The ruler edges were protected with a plastic tube to [8]. This picture of neutral ergonomics as viewed in protect each participant and the student researchers. (Fig. 1) is observed to follow the geometry of a The ruler, measuring tape, and the participant’s right triangle with the working distance projecting eyewear was disinfected with CaviWipes (Metrex™ to be the hypotenuse. Our investigation aimed to Research, Orange, CA, USA) surface disinfectant pre- place a participant in a simulated position in neutral moistened wipe before and after each use. ergonomics prior to measuring working distance. This was based on the support of studies that 2.2. Analysis attribute MSD to improper ergonomics positioning Both demographic and recorded measurements and allowed us to view a working distance that were analyzed to determine statistical significance would be most conducive to a participant in neutral based on individual characteristics with the ergonomics [1]. While in this position, the working application of anatomic measurements in neutral distance was visualized and measured directly. The ergonomics and working distance. Levene’s Test for results of our study provided data to show that our Equality, Variances and t-test for equality of means hypothesized measurement derived indirectly from was used for this study with Pearson’s correlation sig. measurements of anatomical relationships had a (2-tailed). significant positive correlation with our observed actual working distance measurement in the same 3. RESULTS position. Within that anatomic measurement, (ET) and (HWD) were also both positively correlated to Levene’s Test for Equality showed a significant an individual’s height. When viewed separately difference when sig. (2-tailed) is ≤0.05. There was a each component of our equation EF, ET, and HWD marginally significant difference in vision type by also individually showed a significant positive “ET” to the vision; where the non-corrective vision correlation between itself and the observed actual had higher “ET” values compared to corrective vision working distance. Our results showed a significant values Sig.(2-tailed)= 0.058. difference in Eye to Tooth (ET) measurements by Significant differences were found (Sig. (2-tailed) gender with males having significantly higher ET =0.022) when comparing “HWD” between the measurements than females. This appears to be corrective and non-corrective vision, where the non- explained by the higher average ET measurement corrective vision had higher HWD. in males of 22.49 inches versus females with 20.73 There was a highly significant difference in “ET” inches. Similarly, there was a significant difference values by gender with males having significantly in the Hypothesized Working Distance (HWD) with higher “ET” values than females. Sig.(2-tailed)=0.000 males having a significantly higher HWD than fema- There was a highly significant difference in “HWD” les. Again, the average measurements for males by gender with males having a significantly higher was slightly higher at 23.61 inches compared to “Hypothesized Working Distance” than females. females at 21.62 inches. The results also showed Sig.(2-tailed)=0.000. There was a strong correlation a positive correlation of HWD and ET to height in between HWD “Hypothesized Working Distance” both the female and male participants giving more and ET “Actual Working Distance” (Linear regression= support that collectively an individual’s anatomic 0.775) see Fig. 3. proportions can help to determine a proper working distance. It is unclear if the differences in male to 4. DISCUSSION female anatomic measurements is contributory to the development of poor posture or MSDs; however, Our study involved obtaining measurements of previous studies have cited an increase in reported subjects in anatomic position with proper ergono- MSDs in females compared to males. In a study on mics and using those values in the Pythagorean ergonomics in preclinical dental students, Kamal et al theorem to hypothesize an individual’s working [10] reported differences in the postures of male and distance as the hypotenuse. The primary purpose female participants without magnification, where of this investigation was to analyze the relationship female students had worse ergonomic ratings than between measurements in an anatomic ergonomics males. They also observed a positive correlation position and the individual working distance using between posture and reported pain for both female the geometric principles of the right triangle (Fig. and male students with 89.1% of female students 2). The core of the objectives centers on neutral and 65% of male students reporting MS pain after Stoma Edu J. 2021;8(1): 45-51 pISSN 2360-2406; eISSN 2502-0285 49 Hussein HS, et al. www.stomaeduj.com starting preclinical training. A marginally significant operator while in neutral ergonomics position and Original Articles difference in vision type by ET was found where non- a mathematical determination of proper working corrective vision had a higher ET than corrective distance can be obtained. When applying the prin- vision. This finding cannot be definitively explained ciples of the Pythagorean theorem with specified since our measurements were derived while the anatomic measurements the hypothesized working participant was sitting in neutral ergonomics and distance has a significant positive correlation to a hypothesized from anatomic measurements. participant’s actual measured working distance. Further studies may be necessary to investigate the This finding may contribute to a more standardized significance of corrective and non-corrective visi- method to measure the working distance that fits on differences. Our interpretation of the results provi- the proper neutral ergonomics for the operator. The des that our hypothesis was correct, and our first null hypothesis was accepted, while the second working distance value obtained through anatomic and third hypotheses were rejected. Through this measurements is similar to a measured working study, we are able to provide applicable information distance in neutral ergonomics. An individualized for students to reinforce proper ergonomics through working distance correlating to a person’s body the analysis of individual working distance values proportions can accurately provide their expected and the relationship to individual anatomic measure- working distance. This allows us to propose that ments in order to utilize adjuncts like magnification ideal working distance can be reproduced consis- in dentistry. tently through the Pythagorean formula with measured values of the eye to the cubital fossa and CONFLICT OF INTEREST the cubital fossa to the tooth. In addition, by using The authors declare no conflict of interest. identifiable landmarks (ie: the outer canthus and antecubital fossa), one may be able to obtain these ACKNOWLEDGMENTS measurements to calculate the desired working distance assuming ergonomics position without the None. aid of simulation in a dental chair or with a manne- quin. Furthermore, future applications of this study AUTHOR CONTRIBUTIONS may assist in the development of standardized measuring methods, thus promoting bio ergonomic HH: Take the existing design. Come up with some modifications head and neck posture. which improve the sensitivity, and reduce the error percentage of the previous design. Writing the manuscript; Data collection 5. CONCLUSIONS and data analysis. SA, MM, AG: Data collection and data analysis; Writing the manuscript. MZ: Methodology, calculation The results allow us to conclude that we can accept of modifications, writing and reviewing the manuscript. the hypothesis that there is a direct relationship to NA: Methodology, calculation of modifications, writing and the specific anatomical measurements of a dental reviewing the manuscript, data analysis and data interpretation. REFERENCES 1. Valachi B, Valachi K. Preventing musculoskeletal 6. Burger D. ADA wellness survey reveals dentists’ ergonomic disorders in clinical dentistry: strategies to address the issues. ADA News. January 12, 2018. Available from: https:// mechanisms leading to musculoskeletal disorders. J Am www.ada.org/en/publications/ada-news/2018-archive/ Dent Assoc. 2003;134(12):1604-1612. doi: 10.14219/jada. january/ada-wellness-survey-reveals-dentists-ergonomic- archive.2003.0106. PMID: 14719757. issues Full text links PubMed Google Scholar Scopus WoS Full text link 2. Ng A, Hayes MJ, Polster A. Musculoskeletal Disorders 7. Carpentier M, Aubeux D, Armengol V, et al. The effect of and Working Posture among Dental and Oral Health magnification loupes on spontaneous posture change of Students. Healthcare (Basel). 2016;4(1):13. doi: 10.3390/ dental students during preclinical restorative training. J Dent healthcare4010013. PMID: 27417601; PMCID: PMC4934547. Educ. 2019;83(4):407-415. doi: 10.21815/JDE.019.044. PMID: Full text links PubMed Crossref Google Scholar Scopus WoS 30745350. 3. Rising DW, Bennett BC, Hursh K, Plesh O. Reports of Full text link PubMed Crossref Google Scholar Scopus WoS body pain in a dental student population. J Am Dent Assoc. 8. Gehrig JS, Sroda R, Saccuzzo D. Fundamentals 2005;136(1):81-86. doi: 10.14219/jada.archive.2005.0032. of periodontal instrumentation and advanced root PMID: 15693502. instrumentation. 8th edition revised. Philadelphia, PA: Wolters Full text link PubMed Crossref Google Scholar Scopus WoS Kluwer; 2019. ISBN: 9781975117504. 4. Aghilinejad M, Kabir-Mokamelkhah E, Talebi A, et al. The Google Scholar effect of magnification lenses on reducing musculoskeletal 9. Roll SC, Tung KD, Chang H, et al. Prevention and discomfort among dentists. Med J Islam Repub Iran. rehabilitation of musculoskeletal disorders in oral health 2016;30:473. PMID: 28491848; PMCID: PMC5419231. care professionals: A systematic review. J Am Dent Assoc. Full text link PubMed Google Scholar Scopus 2019;150(6):489-502. doi: 10.1016/j.adaj.2019.01.031. PMID: 5. Zarra T, Lambrianidis T. Musculoskeletal disorders amongst 31030935; PMCID: PMC6709589. Greek endodontists: a national questionnaire survey. Int Full text link PubMed Crossref Google Scholar Scopus WoS Endod J. 2014;47(8):791-801. doi: 10.1111/iej.12219. PMID: 10. Kamal AM, Ahmed DRM, Habib SFK, Al-Mohareb RA. 24283200. Ergonomics of preclinical dental students and potential Full text link PubMed Crossref Google Scholar Scopus WoS musculoskeletal disorders. J Dent Educ. 2020;84(12):1438-1446. doi: 10.1002/jdd.12369. PMID: 32810896. Full text link PubMed Crossref Google Scholar Scopus WoS 50 Stoma Edu J. 2021;8(1): 45-51 pISSN 2360-2406; eISSN 2502-0285 Dental magnification working distance and ergonomic www.stomaeduj.com Original Articles Hind S. HUSSEIN BDS, Assistant Professor of Restorative Dentistry LECOM School of Dental Medicine Bradenton, Florida 34211, USA CV Dr. Hind S. Hussein is a Clinical Assistant Professor at LECOM School of Dental Medicine. She is the director of Operative Dentistry courses. In 2014 she completed her Advanced Post Graduate Multispecialty Residency. In 2014, Dr. Hussein joined the University of Florida UF as Visiting Scientist (Restorative Dental Science and Orthodontics). In 2017, she was certified as UF Graduate Assistant Teacher with a technology program. From 2017 to 2018, she worked as Courtesy Clinical Assistant Professor at UF, with the Operative Dentistry and Prosthodontics, Department of Restorative Dental Sciences. Since 2014 she has been successfully involved in many research projects in dental materials. Dr. Hussein has successfully registered 4 US patents. Questions 1. In an earlier study on the prevalence of body pain in a dental student population, ______ of students reported pain with the percentage increasing with the increase of years in school. qa. 25-30 %; qb. 10-15%; qc. 46-71%; qd. 32-55 %. 2. All below are the null hypotheses tested in the study except one, which one is the exception? qa. There is a direct relationship to the specific anatomical measurements of a dental operator while in neutral ergonomics position, and a mathematical determination of proper working distance can be obtained; qb. No difference in working distance between the corrective and non-corrective vision groups; qc. No difference in working distance between genders; qd. No difference in the working distance when using different light. 3. In the study, the investigators observed and verbally instructed changes in ergonomics keeping in mind the following recommendation: qa. Head tilt of 0 to 20 degrees; qb. Head tilt 0-30 degrees; qc. Head tilt 0-10 degrees; qd. No head tilt. 4. In the conclusion, when applying the principles of the Pythagorean theorem with specified anatomic measurements, the hypothesized working distance has______ to the actual working distance. qa. Non- significant correlation; qb. Significant positive correlation; qc. Significant negative correlation; qd. Borderline significance. Stoma Edu J. 2021;8(1): 45-51 pISSN 2360-2406; eISSN 2502-0285 51