Dentistry is a demanding profession requiring

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1 A Survey of Left-Handed Dental Students and Interns in Saudi Arabia Sulieman S. Al-Johany, B.D.S., M.S.D., D.A.B.P., F.A.C.P. Abstract: The purpose of this study was to survey left-handed (LH) dental students and interns concerning whether they face any problems in their dental education or in their practice of dentistry. The questionnaires were distributed in four dental colleges in different regions in Saudi Arabia. The questionnaire was comprised of sixteen questions to assess the following issues: demographic information, difficulties in dental school or dental practice due to left-handedness, preferred hand in performing different dental procedures, and musculoskeletal complications. The study found that the percentage of LH dental students was around 7 percent (110 out of 1,660). More than half of these participants (n=56) reported that being LH is not a problem in general, while when performing the required dental work, around 51 percent (n=56) agreed to having a problem. The majority (68 percent; n=75) reported that they had a problem with having RH instructors, and 84.5 percent (n=93) responded that their institution is not properly equipped to accommodate LH students. Only 34 percent (n=37) agreed that using facilities of an RH dentist may cause musculoskeletal complications to an LH dentist. The results of this study suggest that dental schools should provide LH students with appropriate equipment and a proper learning environment. Dr. Al-Johany is Associate Professor, Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University. Direct correspondence and requests for reprints to Dr. Sulieman Al-Johany, Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University, P.O. Box 60169, Riyadh 11545, Saudi Arabia; saljohany@hotmail.com. Keywords: dental education, dental students, left-handed students, musculoskeletal complications, Saudi Arabia Submitted for publication 6/15/11; accepted 3/12/12 Dentistry is a demanding profession requiring concentration, precision, and skills. 1 Successful dental treatment depends on such factors as the anatomy and location of teeth, selection of a well-adapted instrument, proper angulations of the instrument, and the proper position of the patient and the dentist as well as manual skills. 2 In dentistry, as in many other professions, equipment and instruments are manufactured to be used by right-handed (RH) users. 3-8 In the general population, the average percentage of left-handed (LH) people ranges from 8 to 15 percent. 9 About 11 percent of U.S. citizens are LH (20 percent of men and 8 percent of women). 10 The percentage has been found to be slightly less than 10 percent in dentists 11 and around 9.3 percent in surgeons. 12 Henderson et al. 11 reported the prevalence of self-reported sinistrality as 8.6 percent among dental students and 17.2 percent among orthodontists compared to 7.4 percent among the general population. 11,13 In an older survey of dental students, Brown 3 found that one in twelve (8 percent) were LH. Manual dexterity is defined as the ability to integrate precision and speed with finely coordinated movement of the arm, hand, and fingers. 14 Brayer et al. defined skill as proficiency that results from training and practice. 15 In dental schools, dental procedures, techniques, chairs, and stations are designed mainly for the RH students. 1,2,5,6,16 Some dental equipment manufacturers design dental chairs especially for LH dentists or in a way that they can be used by both RH and LH dentists with minor modifications. 3,4 Likewise, some of the dental instrument manufacturers have started designing dental instruments especially for LH dentists. The effect of being left-handed on professional practice is a concern not only in dentistry, but also in other fields of medicine requiring hand skills like surgery. 10,12,17-21 Dentists, and particularly general dentists, are at high risk for development of musculoskeletal disorders due to the high visual demands that result in the adoption of a fixed posture. 22 To work on a chair designed for RH students was found uncomfortable by 85.7 percent of the LH students in a study of fortytwo dental students (twenty-one RH and twenty-one LH). 2 In a study by Tezel et al. 1 about musculoskeletal disorders in LH and RH Turkish dental students (ninety-seven RH and twenty-four LH), they found that LH students experienced more musculoskeletal symptoms than RH students. LH students especially suffered from more neck and shoulder pain when compared with RH students. Most if not all of the dental techniques and procedures taught in dental schools are taught to fit RH students. 3-7 Carter and Triplett 23 described a technique for the successful administration of the inferior alveolar nerve injection by an LH dentist. There may be other techniques or procedures in dentistry that also need to be modified to allow LH January 2013 Journal of Dental Education 105

2 dental students to improve the quality of their work. A literature review found no published data focusing on the problems facing LH dental students in their education in dental schools. The purpose of this study was thus to survey LH dental students and interns in Saudi Arabia concerning whether they face any problems in their dental education or in their practice of dentistry. Methods This study was registered as non-funded research and approved by the College of Dentistry Research Center in King Saud University (Registration No. NF2269). A paper-and-pencil questionnaire was designed based on interviews with LH dentists and review of the available literature on this topic. The LH dentists interviewed were two students, two interns, and two specialists with an age range of twenty-three to thirty-six years; all of them were still in practice. The interview was unstructured, and no focus groups were used. Suggestions were taken also from academic colleagues who have performed survey studies but are not expert methodologists. The questionnaire was developed based on all these comments and suggestions. The questionnaire was then pilot-tested with five LH dental students and interns to ensure clarity and face validity and was finalized. Face validity is a method used to estimate whether a test appears to measure a certain criterion. A test is considered to have face validity if it appears to measure what it is supposed to measure. It could be used to refer to the validity of observers who are not expert in testing methodologies as was done in this study. Face validity differs from content validity but is closely related. Content validity depends on a theoretical basis for assuming if a test is assessing all domains of a certain criterion, and it requires more extensive statistical tests than face validity, which only requires an intuitive judgment and relates to whether a test appears to be a good measure or not. 24 The final questionnaire consisted of sixteen questions that assessed the following: demographic information (age, gender, institution, educational level); any perceived difficulties due to being lefthanded in dental school and practice; preferred hand in performing various dental procedures and other activities; musculoskeletal complications; and parents manual habits and any efforts to change the use of the left hand. At the end, the participants were asked for any additional comments. The questionnaires were distributed to dental students and interns in one private and three public dental colleges in different regions in Saudi Arabia. These dental schools were the College of Dentistry in King Saud University (two campuses) and the Riyadh Colleges for Dentistry and Pharmacy, both in Riyadh (Central Region); the College of Dentistry at the King Abdulaziz University in Jeddah (Western Region); and the College of Dentistry at the University of Dammam in Dammam (Eastern Region). The students and interns were asked to indicate their preferred hand in performing dental procedures (selfreporting), and questionnaires were given to the LH students and interns only. Class and group leaders helped to distribute the questionnaires to their LH peers. The total number of students and interns was recorded to determine the percentage of LH students in each class and out of the total number. Only students in their third year and above who were involved in clinical dentistry courses were surveyed because most of the survey questions were clinically oriented. The collected data were analyzed with the Statistical Package for the Social Sciences (SPSS Inc., Chicago, IL; version 16.0). Descriptive statistics were used to summarize the responses, and chi-square and independent proportional t-test were used to compare differences. A p-value <0.05 was accepted as significant. Results Of the 1,660 undergraduate dental students and interns at the four dental schools in academic year , only 110 (6.6 percent) were found to be LH. There was no significant difference in the percentages of the LH respondents between the two genders: 6.8 percent for male and 6.4 percent for female (p=0.724). Of the 110 reported to be LH, there were sixty-three male (57 percent) and fortyseven female (43 percent). They ranged in age from twenty-one to twenty-seven years and were on average twenty-four years of age (mean=23.7, standard deviation=1.56). There was no significant difference among the percentages of LH students and interns at the four schools (p=0.236). There was at least one LH student in all the schools and in all the class levels. The highest percentage of LH students (14.3 percent) was found to be five in a class of thirty-five students, while the lowest percentage (5.56 percent) was found with only one student in a class of eighteen students (Table 1). 106 Journal of Dental Education Volume 77, Number 1

3 Table 2 shows the results of the participants responses to part of the questionnaire and the corresponding p-values. Of those respondents who reported having musculoskeletal complications due to the use of facilities of RH dentists, the most common area with pain was the shoulder and neck. Figure 1 shows the percentage of the answers concerning the area afflicted with pain among the participants. No significant gender differences in the responses to this question were found. Only 34.5 percent (n=38) were purely LH, while 65.5 percent (n=72) were mixed (using both right and/or left hand in performing some dental procedures). Figure 2 shows the percentage of the hand used in performing these dental procedures. The majority of the subjects (74.5 percent; n=82) used only their left hand in writing, 50.9 percent (n=56) in sports, and 9.1 percent (n=10) only in eating. The rest used either the right hand or both. Table 3 shows the manual habits of the participants parents. There were more LH mothers compared to LH fathers, which was significant (p=0.004). Around 61.8 percent (n=68) reported that their parents tried to modify their habit to be RH when they were young. It partially succeeded in 72 percent (n=49) and failed with the rest, 28 percent (n=19). Comments from respondents to the open-ended questions showed that many of them had asked for LH equipment not only in the clinic and laboratory, but also in classrooms. Some participants stated the need of LH teachers to teach them special techniques for being left-handed. Other comments noted the participants appreciation that this study was being conducted. Discussion Surveys are procedures used to investigate opinions, and a paper-and-pencil questionnaire can be used to improve the response rate and the accuracy of responses. 25 Only a few data regarding LH dental students were found in the literature. 1,2,11,13,15,16,23 In this study, the LH dental students and interns were asked to express their opinions about various aspects of learning and practicing dentistry. The results of the survey showed that the percentage of the LH students is 6.6 percent of the total number of the students approached. This is slightly less than the percentage reported by Brown 3 and Henderson et al. 11 among dental students; those researchers reported 8 percent and 8.6 percent, respectively, and 17.2 percent among orthodontists. In the general population, the percentages ranged from 8 to 15 percent. 9 However, no information is Table 1. Demographic data of participants in study Left-Handed Participants N % p-value Age % (left-handed n=110) % % % % % % Did not indicate % Gender Male (n=924) % (total n=1660) Female (n=736) % Institution King Saud University (n=452) % (total n=1660) Riyadh Colleges of Dentistry and Pharmacy (n=613) % King Abdulaziz University (n=469) % University of Dammam (n=126) 8 6.3% Educational level Undergraduate % (left-handed n=110) Third year % Fourth year % Fifth year % Intern % January 2013 Journal of Dental Education 107

4 Table 2. Selected survey questions and participants responses with p-values p-value Question Agree Don t Know Disagree Agree/Disagree It is difficult for you to be left-handed. 41 (37.3%) 13 (11.8%) 56 (50.9%) You have a problem in being left-handed to do the required dental work. 56 (50.9%) 3 (2.7%) 51 (46.4%) You have a problem with your instructors or supervisors in 75 (68.2%) 10 (9.1%) 25 (22.7%) being left-handed and they are right-handed. Your institution is properly equipped to accommodate you 9 (8.2%) 8 (7.3%) 93 (84.5%) as left-handed. You prefer to use a dental chair, unit, or station designed 93 (84.5%) 8 (7.3%) 9 (8.2%) especially for a left-handed dentist. You can use the devices manufactured to be used by 88 (80.0%) 11 (10.0%) 11 (10.0%) right-hand dentists. Being a left-handed dentist will affect your dental assistant s 63 (57.0%) 19 (17.3%) 28 (25.5%) ability or convenience to work. Patient feels discomfort being treated by a left-handed dentist. 32 (29.1%) 42 (38.2%) 36 (32.7%) You should write being a left-handed dentist in your CV. 37 (33.6%) 43 (39.1%) 30 (27.3%) You will correct the habit of your children in the future if 34 (30.9%) 13 (11.8%) 63 (57.3%) they show the habit of using their left hand. A left-handed dentist using the facilities of a right-handed 37 (33.6%) 28 (25.5%) 45 (40.9%) dentist can cause some musculoskeletal medical complications. Note: p-value <0.05 was considered significant. available about the prevalence of left-handedness in the general population of Saudi Arabia that could be used as a reference figure. Slightly more than one-third of the LH respondents indicated that it is difficult to be LH in general. In response to the question about how difficult it is for LH students to perform the required dental procedures, the percentage increased to slightly more than half of the group. This finding is consistent with the results of Henderson et al., 11 who found that LH dentists thought that left-handedness was a general inconvenience. The finding points to the difficulties LH individuals face, and these difficulties increase when practicing dentistry. When working with RH instructors, around two-thirds of the respondents indicated that they had a problem. This could be due to the difficulty of the RH instructors to teach an LH student some techniques that may require certain modifications or to adjust to their LH station for the evaluation of their work. The thoughts of RH instructors or mentors concerning teaching LH dental students could be for the focus of a future survey. In their comments, most of the LH students complained that there were no clear instructions or materials to read either in the literature or in dental textbooks that would help them to master the required dental techniques. Some of them asked if there is an LH instructor to teach the LH students. Maybe it would be useful for dental schools to encourage qualified LH or mixed-handed specialist dentists to provide special attention to LH students. It is not surprising to find that most of the LH respondents (84.5 percent) said their institution is not equipped properly to accommodate them as LH dental students. It is probably not easy for dental schools to provide these needed modifications of the dental chairs and laboratory stations. However, it could be done. 3,4 The same majority in my study asked for dental chairs and stations designed especially for LH dentists. This is in agreement with the results of Kaya and Orbak that 85.7 percent of LH students felt uncomfortable using dental chairs designed for RH providers. 2 In addition, a majority of the respondents (80 percent) in my study agreed that they use devices designed especially for RH. It is very important for LH students to be familiar with the equipment designed for RH. Someone may argue that teaching a student to work in a comfortable LH environment does not prepare them for the RH units present in most dental practices. 11 Still this finding should not be used as a reason not to provide LH students with convenient LH chairs and stations. 108 Journal of Dental Education Volume 77, Number 1

5 Figure 1. Percentage of left-handed participants responses regarding the area in which they felt pain Figure 2. Percentage of left-handed participants responses regarding the hand they used in performing dental procedures If an LH dentist works on an RH dental chair, some modifications were found to be convenient such as over-the-patient delivery (which may be unpopular with patients) and also the spittoon was found convenient at the left of the chair. 3 Kaya and Orbak 2 reported that the care their patients received could be improved by providing the opportunity for LH dentists to work from the left side of the patient. January 2013 Journal of Dental Education 109

6 Table 3. The manual habits of participants parents Father Mother Number Percentage Number Percentage Right-handed % % Left-handed 8 7.5% % Both hands 3 2.8% 8 7.5% Don t know 1 0.9% 1 0.9% Did not indicate 4 3.6% 4 3.6% p=0.004 Adusumilli et al. 17 made many suggestions based on their findings with LH surgeons that could also be applied to LH dentists. These include having basic sets of LH instruments available in the teaching hospitals for medical students to minimize the inconvenience associated with learning, the provision of LH mentors, and other environmental modifications, a simple website, a chapter in surgical textbooks, or a pocket manual outlining the guidelines in performing invasive and surgical procedures specifically for LH medical students and surgery residents. The convenience of dental assistants to assist an LH dentist is an area of interest. The participants in this survey were dental students who usually work without the help of a dental assistant to do four-handed dentistry in dental school. However, the majority of them (57 percent) said being LH may affect the ability or convenience of the dental assistant to work. Dental assistant training programs should include training to assist LH dentists. 3 The opinions of dental assistants about assisting LH dentists could be obtained in future survey. Surprisingly, one-third (31 percent) of the participants said that they will change the habit of their children in the future if they show LH preference. This could be because of the difficulties facing being left-handed, which they do not want their children to face. This attitude can be expected in a dominant RH world. It adds some responsibility for dental educators to accommodate LH students without any kind of differentiation than RH. Simply, it is not a disability that needs correction. The results of this survey showed that one-third (33.5 percent) of the participants have musculoskeletal symptoms mainly in the neck and shoulder. This finding is consistent with the results of Tezel et al. 1 when they compared the musculoskeletal symptoms of RH and LH dental students. The purpose of that study was to find out the musculoskeletal disorders between LH and RH dental students and concentrated only on the position, location, and severity of the pain without any other aspects of being LH in dentistry. In my study, the questionnaire focused on being LH in dentistry and the problems associated with being LH in dental education and dental practice in general. My findings were also in agreement with the results by Henderson et al., 11 who found that fixed RH units seemed to generate minor irritation to LH dentists. This could be explained by the inconvenience in using RH dental chairs and stations. Canakci et al. 16 reported that the average negative scaling and root planing forces were significantly greater in LH dentists than in RH dentists. It could be that LH dentists exert more efforts than RH dentists due to working on an RH dental chair. This poor working condition may cause musculoskeletal symptoms. The present study results are consistent with this consideration. 1 As stated by Tezel et al., 1 The best ergonomic working principles should be taught to the students, and dental schools should provide a comfortable working environment. LH students should work on an LH designed chair, and further study is required to identify factors that will reduce the prevalence of symptoms amongst those practicing general dentistry. Most of the participants reported being able to use both hands in performing dental procedures. This could be an advantage for them. This result was in agreement with the findings by Henderson et al. 11 that there are many more mixed-handers than LH only among dental students. Schmauder et al. 26 found that the strength of the sub-dominant hand-arm system is inferior in RH subjects. Contrary to this, the difference in strength between the arms of an LH person was hardly noticeable. In treatment of dental calculus, Orbak et al. 13 reported that the LH students were better than the RH students when using reverse chairs. The finding that 51 percent of the respondents used their left hand in sports was consistent with 110 Journal of Dental Education Volume 77, Number 1

7 the results of studies in other professions, which showed that around 45 percent of LH persons are leftfooted. 27 Very few subjects (9 percent) used their left hand when eating. This could be due to religious and cultural reasons. In Saudi Arabia where the survey was conducted, it is generally not acceptable to eat with the left hand especially in public events. The results of this study did not find significant correlations between the parents preferred hand and the students LH habit. There were more LH mothers compared to LH fathers, which was significant, but most of the parents were RH. LH mothers may have more effect on their children to be LH than LH fathers, but the explanation for this is beyond this study s purpose and author s experience. However, this could explain why many students (62 percent) reported that their parents tried when they were young to modify their habit to be RH. Conclusions This article has attempted to bring the attention of the profession to this important issue as many LH dental students face challenges. This problem seems to be an issue in dental education worldwide. It raises serious questions such as whether applicants for admission to dental schools should be asked about their preferred hand to allow the school to prepare ahead of time the equipment needed for LH students. Should it be mandatory for dental schools to provide LH dental educators or mentors to teach LH dental students? Shall this be included as part of the academic accreditation requirements? More research is needed to answer these and related questions. This study found that the prevalence of LH students in this dental school population was around 7 percent. Dental schools should provide LH students with needed equipment and a proper learning environment. Expert senior LH dentists should help junior LH dental students to learn techniques and procedures used by left-handers. This could be done by involving LH educators in dental education or by publishing articles and reading materials for LH dental students. Acknowledgments The author would like to thank Drs. Wasseem Alzemei and Ahmad Farghal, King Abdulaziz University, for distributing the questionnaire in Jeddah; Dr. Aws AlRejay, Dammam University, for distributing the questionnaire in Dammam; Drs. Faleh AlShahrany and Abdulaziz AlHilal, King Saud University, and Dr. Hadi Alamri, Riyadh Colleges of Dentistry and Pharmacy, for distributing the questionnaire in Riyadh. Appreciation is also extended to Mr. Nassr AlMaflehi for his help with the statistical analysis as well as all the students and interns for responding to the survey. REFERENCES 1. Tezel A, Kavrut F, Tezel A, Kara C, Demir T, Kavrut R. Musculoskeletal disorders in left- and right-handed Turkish dental students. Int J Neurosci 2005;115(2): Kaya M, Orbak R. Performance of left-handed dental students is improved when working from the left side of the patient. Int J Ind Ergon 2004;33: Brown JM. Left-handed GDPs and students. Br Dent J 1995;178(12): Carsberg C. Left-handed GDPs and dental nurses. Br Dent J 1995;179(7): Graham R. Left-handed GDPs and students. Br Dent J 1995;178(9): Henderson NJ, Stephens CD. Left-handed GDPs. Br Dent J 1995;179(1):8. 7. Whitby B. Left-handed GDPs. Br Dent J 1995;179(1):9. 8. Whitmore J. Left-handed GDPs. Br Dent J 1995;179(1):8. 9. Hardyck C, Petrinovich LF. Left-handedness. Psychol Bull 1977;84(3): Rohrich RJ. Left-handedness in plastic surgery: asset or liability? Plast Reconstr Surg 2001;107(3): Henderson NJ, Stephens CD, Gale D. Left-handedness in dental undergraduates and orthodontic specialists. Br Dent J 1996;181(8): Makay O, Icoz G, Ersin S. Surgeons view on the limitations of left-handedness during endoscopic surgery. J Laparoendosc Adv Surg Tech A 2008;18(2): Orbak R, Tezel A, Canakci V, Tan U. Right- and lefthanded dentists using right- and left-sided dental chairs in treatment of calculus. Int J Neurosci 2002;112(1): Ozcan A, Tulum Z, Pinar L, Baskurt F. Comparison of pressure pain threshold, grip strength, dexterity, and touch pressure of dominant and non-dominant hands within and between right- and left-handed subjects. J Korean Med Sci 2004;19(6): Brayer WK, Mellonig JT, Dunlap RM, Marinak KW, Carson RE. Scaling and root planing effectiveness: the effect of root surface access and operator experience. J Periodontol 1989;60(1): Canakci V, Tan U, Orbak R, Tezel A. Right- and lefthanded dentists in periodontal therapy. Int J Neurosci 2002;112(1): Adusumilli PS, Kell C, Chang JH, Tuorto S, Leitman IM. Left-handed surgeons: are they left out? Curr Surg 2004;61(6): Pegum M. The left-handed use of scissors. Ann R Coll Surg Engl 2003;85(3): Wooton MA. A first left-handed intravenous cannula. Anaesthesia 2001;56(4): Kavka SJ. Left-handedness in plastic surgery: asset or liability? Plast Reconstr Surg 2002;109(2):823. January 2013 Journal of Dental Education 111

8 21. Tchantchaleishvili V, Myers PO. Left-handedness: a handicap for training in surgery? J Surg Educ 2010;67(4): Morse TF, Michalak-Turcotte C, Atwood-Sanders M, Warren N, Peterson DR, Bruneau H, Cherniack M. A pilot study of hand and arm musculoskeletal disorders in dental hygiene students. J Dent Hyg 2003;77(3): Carter DB, Triplett WW. The inferior alveolar injection for the left-handed dentist. Gen Dent 1982;30(4): Anastasi A. Psychological testing. New York: Macmillan, 1988: Fanning E. Formating a paper-based survey questionnaire: best practices. Practical Assessment Res Eval 2005;10: Schmauder M, Eckert R, Schindhelm R. Forces in the hand-arm system: investigations of the problem of lefthandedness. Int J Ind Ergon 1992;12: Augustyn C, Peters M. On the relation between footedness and handedness. Percept Mot Skills 1986;63: Journal of Dental Education Volume 77, Number 1