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Evaluating the head posture of dentists with no neck pain
Journal of Bodywork & Movement Therapies (2013) 17, 430e433
Available online at www.sciencedirect.com
journal homepage: www.elsevier.com/jbmt
ERGONOMICS
Evaluating the head posture of dentists with no neck pain J. Mostamand, Ph.D*, H. Lotfi, BS, N. Safi, BS Musculoskeletal Research Centre, School of Rehabilitation Sciences, Isfahan University of Medical Sciences, PO Box 164, Isfahan 8174673461, Iran Received 2 July 2012; received in revised form 26 October 2012; accepted 7 November 2012
KEYWORDS Cervical lordosis; Forward head posture; Posture
Summary Introduction: Dentistry is one of the professions that requires a high degree of concentration during the treatment of patients. There are many predisposing factors, affecting dentists when working on the patient’s teeth, including neck flexion, arm abduction and inflexible postural positions, which may put them at the risk of developing musculoskeletal disorders related to the neck. Although dentists with long records of service show different levels of pain and discomfort in their necks, there is no evidence regarding whether younger dentists report neck pain before the onset of an abnormal condition in this region, including forward head posture (FHP). Discovering any alteration in the head posture of dentists might confirm one of the reasons for neck pain in this population. Materials: Forty one dentists with no neck pain and forty controls having jobs other than dentistry who had no risk factors related to head posture voluntarily participated in the present study. A standard method was used to measure the cervical curve in these two groups. Results: There was no significant difference between the mean values of cervical curve in dentists and the control group (p > 0.05). There was also no significant difference between cervical curve values in dentists working for either 5e8 years or 8e12 years (p > 0.05). The only significant difference was observed in mean cervical curve values of men and women in the dentist group (p < 0.05). Conclusion: No alteration of cervical curve in the dentist group compared to controls might be due to absence of pain sensation in the dentists in the current study. In other words, this group might have not yet experienced sufficient change in head posture to experience significant pain in their neck region. ª 2012 Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: þ98 311 7922024; fax: þ98 311 6687270. E-mail address: [email protected] (J. Mostamand). 1360-8592/$ - see front matter ª 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jbmt.2012.11.002
Evaluating the head posture of dentists
Introduction Some researchers believe that a correct posture is an ideal state of musculoskeletal balance that imposes the least amount of stress on the body (Finsen et al., 1998; Yip et al., 2008). Although a proper posture is an optimal condition advised by many specialists, poor posture is not uncommon (Yip et al., 2008). Many musculoskeletal disorders are attributed to the stresses resulting from sustained or repetitive activities. Most of these activities constitute people’s daily habits. Any damage to joints, muscles and connective tissues may lead to an abnormal posture. Conversely, an inappropriate posture may also bring about injuries to these anatomical components, causing symptoms such as pain (Akesson et al., 1997). The prevalence of musculoskeletal disorders in the neck and upper extremities is relatively high and it is more common in specific professions including dentistry (Akesson et al., 1997). Dentists should be highly focussed and precise during treatment of patients. In recent years, there has been a trend among dentist to treat their patients while assuming a sitting position. Since the treatment area is very small, the likelihood of inflexible posture increases among dentists (Finsen et al., 1998), which in turn, may predispose to neck and upper extremity disorders leading to painful symptoms (Akesson et al., 1997). In a recent study conducted by Dajpratham et al. (2010), the most prevalent musculoskeletal pain reported by dentists was shoulder pain followed by neck pain, and low back pain. The prevalence of neck pain in their study was reported as 70.3% (Dajpratham et al., 2010). In another study, 75% of dentists with 23 years of working experience showed pain and discomfort in their neck and shoulders during the previous 12 months (Finsen et al., 1998). One of the postural disorders in the head and neck area is forward head posture (FHP) in which, the head is placed in front of gravitational line. Several factors may lead to adoption of FHP such as, gravity, excessive curvature of body alignment, abnormal postures during occupational activities, including inappropriate postures during sitting position (Akesson et al., 1997). An inappropriate posture may result in injury to the joints and more probably to other connective tissues, which may finally lead to pain and disability in the affected subjects. Some studies have revealed a relationship between neck pain and FHP (Yip et al., 2008). It has been proposed that FHP is one of the reasons of neck pain in dentists, especially those whose job experience exceeds 15 years (McAviney et al., 2005). No previous studies were identified in which a subgroup analysis had been performed regarding the possible effects that years of practice, or gender of dentists may have had on symptoms. Considering the relation between FHP and neck pain (Yip et al., 2008; McAviney et al., 2005), and the absence of evidence on the relationship between pain and head posture in dentists, the current study considered the head posture in relatively young dentists with no neck pain. The results of this study might contribute to knowing whether these subjects reveal any alterations in their head posture before feeling pain in their necks. Understanding any alteration in the head posture in dentists before pain start
431 might confirm one of the reasons for neck pain in this profession. In fact, it would be clinically important to prevent any alteration in normal head posture and subsequently neck pain in professions such as dentistry.
Methods In this study, 41 dentists (21 women and 20 men) were recruited from their private dental clinics in Isfahan through a simple non-random convenient sampling method. All subjects had a history of working more than 5 years and had experienced no pain in their neck during last 6 months. To ensure participants had the specific years of work experience (more than 5 and less than 15 years), volunteers whose ages were more than 40 and less than 30 years were excluded from this study. Additionally, any history of rheumatic disease or trauma on the neck and history of surgery to this area were among the exclusion criteria. Forty subjects having jobs other than dentistry (22 women and 18 men) with similar criteria of work experience were selected as the control group. These jobs were amongst professions that did not predispose individuals to any postural stress or pain in their neck area. Subjects with professions such as hair dressing, tailoring, typing or any job performed in sustained and/or seated positions were therefore excluded from the control group (Ariens et al., 2001). With increasing neck flexor movements, the amount of cervical lordosis would be decreased in the long-term. FHP acts as a compensatory mechanism associated with increased cervical curve during standing (Hertling and Kessler, 2006). Measuring this curve may therefore help to estimate the extent of FHP. Cervical lordosis has been used as a reliable criterion for FHP in previous studies (Morningstar, 2002; Ahanjan et al., 2008). Background data were collected by means of a questionnaire. Using a measuring device for the cervical curve, the degree of lordosis was evaluated in both groups of subjects (Hertling and Kessler, 2006). This device included a 170 cm vertical rod and a 30 cm scaled horizontal ruler. The vertical rod was installed on a flat 35 35 cm insole. The scaled horizontal ruler on the vertical rod had the capability of both inferior-superior and anterior-posterior movements. All subjects were then trained to stand on the flat insole while the apex of their thoracic spine was in touch with the vertical rod. They were also instructed to stand with a width distance equal to the distance between their two shoulder blades and asked to look forward after several neck flexions and extensions. The scaled horizontal ruler was then located in the deepest point of the cervical curve and this point was finally recorded as the cervical curve of each subject. In the current study the main hypothesis was that the cervical curve in two independent groups of dentists and controls would be different. There were also two secondary hypotheses in the present study; the cervical curve should be equal in both male and female dentists, and there should be difference between the cervical curve of dentists with two different ranges of practice experience of 5e8 years and 8e12 years.
432
J. Mostamand et al.
Type I error of 0.05 was considered for all statistical tests. SPSS 13 was used to analyze data. As the data sets were found to be normally distributed, independentsample t-test was used to detect any significant difference between the two groups. Furthermore, the Pearson correlation test was used to examine the relationship between the cervical curve and quantitative variables of weight, height and age in each groups of the current study. The present study was approved by the Vice Chancellery for Research of Isfahan University of Medical Sciences. Written informed consent was provided by each participant.
Results Table 1 reveals the demographic characteristics of weight, height, age, with regard to the gender of the subjects for both groups of dentists and controls, respectively. According to the compared results, there was no statistically significant difference between the two study groups (p > 0.18). According to Table 2, there was no significant difference between the mean values of cervical curve of dentists and controls (p > 0.05). In other words, no difference was found between the cervical curve in both dentist and control groups. There was a statistically significant difference between the mean values of the cervical curve in male and female dentists (p < 0.05), meaning that the curve is greater in male compared to female dentists (Table 3). However, there was no significant difference between the mean values of cervical curve in male and female controls (p > 0.05). There was no significant difference between the cervical curve of dentists with two different practice experience of 5e8 years and 8e12 years (p > 0.05), revealing that an increased level of working duration of up to 12 years did not alter the curvature of cervical spine in the dentists (Table 4). It was also found that there is a significant and positive correlation between the cervical curve and the height of subjects in the dentist group, revealing a direct relationship between height and the cervical curve (r Z 0.58, p < 0.05). In other words, the cervical curve increases as the height of subjects increases. This correlation was however, nonsignificant among controls (r Z 0.18, p > 0.05). The results obtained from Pearson correlation test showed a relationship between the height and the cervical curve in the dentist group. Considering the greater values of the cervical curve in male dentists compared to female dentists (Table 3), regression analysis was used to Table 1 Demographic characteristics of both dentist and control groups. Data represents mean SD. Weight (kg) Height (cm) Age (year) p value
Table 2 Comparison of the cervical curve mean values (standard deviation Z SD) between study groups. Cervical curve (cm)
Dentists (41)
Controls (40)
p value
6.80 (1.34)
6.69 (1.34)
0.72
determine any relation between the curvature of the cervical spine and height in the dentist group. In a linear regression model and using least squares method, the height variable only remained in the test process (Table 5) when other variables including gender and the weight of subjects were omitted from the model (p < 0.05, F Z 8.67). In other words, it can be stated that the observed difference of the cervical curve value in the dentist group, might be due to the difference of height between men and women working in this profession (p < 0.05). A similar argument is not appropriate for the control group, as there was no significant difference between the height of two genders in this group (p > 0.05).
Discussion Considering the results of the current study, there was no statistically significant difference between the cervical curve of dentists and the control group. In addition, the position of head and neck in the dentist group with two different working histories of 5e8 and 8e12 years was not statistically different. The only difference was found in the head posture of male and female dentists. According to the regression analysis, the difference between cervical curves in the two genders might be related to the difference between the height of men and women in the dentist group. The greater amount of cervical curve in the male dentists compared to females working in this profession might not therefore be due to the abnormal posture of head in men, but to their greater height. Previous studies showed a relationship between neck pain and posture of the head. In a study conducted by Yip et al. (2008), it was shown that there was a direct relationship between neck pain and FHP and the disability resulting from FHP. The results of that study revealed that the craniovertebral angles in subjects with neck pain were smaller compared to the normal subjects (with no pain), so that the greater the angle, the more severe the FHP. A reverse relationship was also observed between this angle and the age of subjects recruited in the Yip et al. study. Additionally, in their study, there was a reverse relationship
Table 3 Comparison of the cervical curve mean values (standard deviation Z SD) between the two genders of dentist and control groups.
Dentists (21 W, 20 M)
Controls (22 W, 18 M)
Dentists
Controls
70.12 (13.95) 169.83 (10.99) 33.05 (3.74) p > 0.18
67.00 (12.62) 166.35 (10.04) 34.98 (3.54)
Female (21) Male (20)
Female (22) Male (18)
W Z Women, M Z Men.
Cervical 6.26 (1.00) curve (cm) p value 0.008
7.35 (1.45) 6.33 (1.15)
0.05
7.12 (1.45)
Evaluating the head posture of dentists
433
Table 4 Comparison of the cervical curve mean values (standard deviation Z SD) in dentists with two different working histories. Working history of dentists
Number
Cervical curve (cm)
p value
5e8 years 8e12 years
20 21
6.84 (1.74) 6.75 (0.86)
<0.84
between the craniovertebral angle and the disability caused by neck pain and its severity in these subjects (Yip et al., 2008). This relationship revealed that the FHP could be a potential reason for neck pain. In the present study, the head posture was measured while none of subjects in the two study groups experienced pain in their neck region, during the 6 months prior to the beginning of the study. The lack of reported pain might be one of the reasons for no significant difference being observed in the head posture in these two groups. In other words, altered head posture in the tested subjects did not cause pain in their necks, something likely to be more easily measurable when pain is experienced and reported by dentists. In fact, it appears evident that prevention of neck pain, requires that therapists prioritize attention to assisting in the avoidance of pain-provoking postural imbalances in dentists (and others), particularly those affecting the neck. Although in the current study it was found that dentists seem to have similar characteristics to people in other professions, it is reported that some professions such as dentistry are subject to earlier alterations in head posture (Ariens et al., 2001; Finsen et al., 1998; McAviney et al., 2005). Accordingly, earlier prevention of abnormal head posture before onset of painful signs and symptoms might be of benefit for dentists to allow them to perform their work, efficiently, for a longer period of time. According to the current results, it is reasonable to attempt to prevent any abnormal head posture before signs and symptoms in appear in younger dentists. This might be achieved using different strengthening exercises for cervical muscles, prescribed by clinicians or therapists. In the current study, it was also revealed that none of two working history of 5e8 and 8e12 years in dentistry led to postural alteration in heads and necks. Considering the age range of dentist group (30e40 years), the working history of minimum 5 and maximum 15 years appears not to be sufficient to result in any postural alterations of the heads in the relatively young subjects. In a study conducted by Finsen et al. (1998), 115 dentists with average age of 45 years and working history of 23 years were studied for the
Table 5 Model
Final model of regression analysis. Substandard Standard coefficients coefficients B
Height 5.38 0.07
t
Sig
Standard error Beta 2.70 0.01
0.58
1.99 0.054 4.51 0.00
risk factors of developing musculoskeletal disorders. Of these dentists, 75% reported pain and discomfort in their neck and shoulders during previous 12 months. In their study, the average age of dentists was 12 years greater than of those in the present study.
Conclusion There was no significant difference between the cervical curve in the dentist and control groups. There was also no difference between the cervical curve values in dentists with two different working history of 5e8 and 8e12 years. Absence of cervical curve alteration in the dentist group compared to the controls might be due to no pain sensation reported among dentists assessed in the current study. In the present study, the alteration of head posture was not sufficient to generate pain sensation in the dentist group. Therefore significantly altered neck lordosis should not be anticipated in dentists aged between 30 and 40 years.
Conflict of interest statement We confirm that the authors have no conflict of interests regarding this paper.
References Ahanjan, S., Behpour, N., Keyvanlou, F., 2008. The study of cervical curvature in forward head posture. In: Proceedings of the 15th Sports Medicine Balkan Congress, Oct 1e4; Bucharest, Romania, p. 14. Akesson, I., Hansson, G.A., Balogh, I., Mortiz, U., Skerfving, S., 1997. Quantifying work load in neck, shoulders and wrists in female dentists. International Archives of Occupational and Environmental Health 69 (6), 461e474. Ariens, G.A., Bongers, P.M., Douwes, M., Miedema, M.C., Hoogendoorn, W.E., van der, W.G., et al., 2001. Are neck flexion, neck rotation, and sitting at work risk factors for neck pain? Results of a prospective cohort study. Occupational and Environmental Medicine 58 (3), 200e207. Dajpratham, P., Ploypetch, T., Kiattavorncharoen, S., Boonsiriseth, K., 2010. Prevalence and associated factors of musculoskeletal pain among the dental personnel in dental school. Journal of the Medical Association of Thailand 93 (6), 714e721. Finsen, L., Christensen, H., Bakke, M., 1998. Musculoskeletal disorders among dentists and variation in dental work. Applied Ergonomics 29 (2), 119e125. Hertling, D., Kessler, R.M., 2006. Management of Musculoskeletal Disorders; Physical Therapy Principles and Methods, fourth ed. Lippincotts, Williams and Wilkins, Philadelphia. 393e394. McAviney, J., Schulz, D., Bock, R., Harrison, D.E., Holland, B., 2005. Determining the relationship between cervical lordosis and neck complaints. Journal of Manipulative Physical Therapy 28 (3), 187e193. Morningstar, M., 2002. Cervical curve restoration and forward head posture reduction for the treatment of mechanical thoracic pain using the pettibon corrective and rehabilitative procedures. Journal of Chiropractic Medicine 1 (3), 113e115. Yip, C.H., Chiu, T.T., Poon, A.T., 2008. The relationship between head posture and severity and disability of patients with neck pain. Manual Therapy 13 (2), 148e154.
Available online at www.sciencedirect.com
journal homepage: www.elsevier.com/jbmt
ERGONOMICS
Evaluating the head posture of dentists with no neck pain J. Mostamand, Ph.D*, H. Lotfi, BS, N. Safi, BS Musculoskeletal Research Centre, School of Rehabilitation Sciences, Isfahan University of Medical Sciences, PO Box 164, Isfahan 8174673461, Iran Received 2 July 2012; received in revised form 26 October 2012; accepted 7 November 2012
KEYWORDS Cervical lordosis; Forward head posture; Posture
Summary Introduction: Dentistry is one of the professions that requires a high degree of concentration during the treatment of patients. There are many predisposing factors, affecting dentists when working on the patient’s teeth, including neck flexion, arm abduction and inflexible postural positions, which may put them at the risk of developing musculoskeletal disorders related to the neck. Although dentists with long records of service show different levels of pain and discomfort in their necks, there is no evidence regarding whether younger dentists report neck pain before the onset of an abnormal condition in this region, including forward head posture (FHP). Discovering any alteration in the head posture of dentists might confirm one of the reasons for neck pain in this population. Materials: Forty one dentists with no neck pain and forty controls having jobs other than dentistry who had no risk factors related to head posture voluntarily participated in the present study. A standard method was used to measure the cervical curve in these two groups. Results: There was no significant difference between the mean values of cervical curve in dentists and the control group (p > 0.05). There was also no significant difference between cervical curve values in dentists working for either 5e8 years or 8e12 years (p > 0.05). The only significant difference was observed in mean cervical curve values of men and women in the dentist group (p < 0.05). Conclusion: No alteration of cervical curve in the dentist group compared to controls might be due to absence of pain sensation in the dentists in the current study. In other words, this group might have not yet experienced sufficient change in head posture to experience significant pain in their neck region. ª 2012 Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: þ98 311 7922024; fax: þ98 311 6687270. E-mail address: [email protected] (J. Mostamand). 1360-8592/$ - see front matter ª 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jbmt.2012.11.002
Evaluating the head posture of dentists
Introduction Some researchers believe that a correct posture is an ideal state of musculoskeletal balance that imposes the least amount of stress on the body (Finsen et al., 1998; Yip et al., 2008). Although a proper posture is an optimal condition advised by many specialists, poor posture is not uncommon (Yip et al., 2008). Many musculoskeletal disorders are attributed to the stresses resulting from sustained or repetitive activities. Most of these activities constitute people’s daily habits. Any damage to joints, muscles and connective tissues may lead to an abnormal posture. Conversely, an inappropriate posture may also bring about injuries to these anatomical components, causing symptoms such as pain (Akesson et al., 1997). The prevalence of musculoskeletal disorders in the neck and upper extremities is relatively high and it is more common in specific professions including dentistry (Akesson et al., 1997). Dentists should be highly focussed and precise during treatment of patients. In recent years, there has been a trend among dentist to treat their patients while assuming a sitting position. Since the treatment area is very small, the likelihood of inflexible posture increases among dentists (Finsen et al., 1998), which in turn, may predispose to neck and upper extremity disorders leading to painful symptoms (Akesson et al., 1997). In a recent study conducted by Dajpratham et al. (2010), the most prevalent musculoskeletal pain reported by dentists was shoulder pain followed by neck pain, and low back pain. The prevalence of neck pain in their study was reported as 70.3% (Dajpratham et al., 2010). In another study, 75% of dentists with 23 years of working experience showed pain and discomfort in their neck and shoulders during the previous 12 months (Finsen et al., 1998). One of the postural disorders in the head and neck area is forward head posture (FHP) in which, the head is placed in front of gravitational line. Several factors may lead to adoption of FHP such as, gravity, excessive curvature of body alignment, abnormal postures during occupational activities, including inappropriate postures during sitting position (Akesson et al., 1997). An inappropriate posture may result in injury to the joints and more probably to other connective tissues, which may finally lead to pain and disability in the affected subjects. Some studies have revealed a relationship between neck pain and FHP (Yip et al., 2008). It has been proposed that FHP is one of the reasons of neck pain in dentists, especially those whose job experience exceeds 15 years (McAviney et al., 2005). No previous studies were identified in which a subgroup analysis had been performed regarding the possible effects that years of practice, or gender of dentists may have had on symptoms. Considering the relation between FHP and neck pain (Yip et al., 2008; McAviney et al., 2005), and the absence of evidence on the relationship between pain and head posture in dentists, the current study considered the head posture in relatively young dentists with no neck pain. The results of this study might contribute to knowing whether these subjects reveal any alterations in their head posture before feeling pain in their necks. Understanding any alteration in the head posture in dentists before pain start
431 might confirm one of the reasons for neck pain in this profession. In fact, it would be clinically important to prevent any alteration in normal head posture and subsequently neck pain in professions such as dentistry.
Methods In this study, 41 dentists (21 women and 20 men) were recruited from their private dental clinics in Isfahan through a simple non-random convenient sampling method. All subjects had a history of working more than 5 years and had experienced no pain in their neck during last 6 months. To ensure participants had the specific years of work experience (more than 5 and less than 15 years), volunteers whose ages were more than 40 and less than 30 years were excluded from this study. Additionally, any history of rheumatic disease or trauma on the neck and history of surgery to this area were among the exclusion criteria. Forty subjects having jobs other than dentistry (22 women and 18 men) with similar criteria of work experience were selected as the control group. These jobs were amongst professions that did not predispose individuals to any postural stress or pain in their neck area. Subjects with professions such as hair dressing, tailoring, typing or any job performed in sustained and/or seated positions were therefore excluded from the control group (Ariens et al., 2001). With increasing neck flexor movements, the amount of cervical lordosis would be decreased in the long-term. FHP acts as a compensatory mechanism associated with increased cervical curve during standing (Hertling and Kessler, 2006). Measuring this curve may therefore help to estimate the extent of FHP. Cervical lordosis has been used as a reliable criterion for FHP in previous studies (Morningstar, 2002; Ahanjan et al., 2008). Background data were collected by means of a questionnaire. Using a measuring device for the cervical curve, the degree of lordosis was evaluated in both groups of subjects (Hertling and Kessler, 2006). This device included a 170 cm vertical rod and a 30 cm scaled horizontal ruler. The vertical rod was installed on a flat 35 35 cm insole. The scaled horizontal ruler on the vertical rod had the capability of both inferior-superior and anterior-posterior movements. All subjects were then trained to stand on the flat insole while the apex of their thoracic spine was in touch with the vertical rod. They were also instructed to stand with a width distance equal to the distance between their two shoulder blades and asked to look forward after several neck flexions and extensions. The scaled horizontal ruler was then located in the deepest point of the cervical curve and this point was finally recorded as the cervical curve of each subject. In the current study the main hypothesis was that the cervical curve in two independent groups of dentists and controls would be different. There were also two secondary hypotheses in the present study; the cervical curve should be equal in both male and female dentists, and there should be difference between the cervical curve of dentists with two different ranges of practice experience of 5e8 years and 8e12 years.
432
J. Mostamand et al.
Type I error of 0.05 was considered for all statistical tests. SPSS 13 was used to analyze data. As the data sets were found to be normally distributed, independentsample t-test was used to detect any significant difference between the two groups. Furthermore, the Pearson correlation test was used to examine the relationship between the cervical curve and quantitative variables of weight, height and age in each groups of the current study. The present study was approved by the Vice Chancellery for Research of Isfahan University of Medical Sciences. Written informed consent was provided by each participant.
Results Table 1 reveals the demographic characteristics of weight, height, age, with regard to the gender of the subjects for both groups of dentists and controls, respectively. According to the compared results, there was no statistically significant difference between the two study groups (p > 0.18). According to Table 2, there was no significant difference between the mean values of cervical curve of dentists and controls (p > 0.05). In other words, no difference was found between the cervical curve in both dentist and control groups. There was a statistically significant difference between the mean values of the cervical curve in male and female dentists (p < 0.05), meaning that the curve is greater in male compared to female dentists (Table 3). However, there was no significant difference between the mean values of cervical curve in male and female controls (p > 0.05). There was no significant difference between the cervical curve of dentists with two different practice experience of 5e8 years and 8e12 years (p > 0.05), revealing that an increased level of working duration of up to 12 years did not alter the curvature of cervical spine in the dentists (Table 4). It was also found that there is a significant and positive correlation between the cervical curve and the height of subjects in the dentist group, revealing a direct relationship between height and the cervical curve (r Z 0.58, p < 0.05). In other words, the cervical curve increases as the height of subjects increases. This correlation was however, nonsignificant among controls (r Z 0.18, p > 0.05). The results obtained from Pearson correlation test showed a relationship between the height and the cervical curve in the dentist group. Considering the greater values of the cervical curve in male dentists compared to female dentists (Table 3), regression analysis was used to Table 1 Demographic characteristics of both dentist and control groups. Data represents mean SD. Weight (kg) Height (cm) Age (year) p value
Table 2 Comparison of the cervical curve mean values (standard deviation Z SD) between study groups. Cervical curve (cm)
Dentists (41)
Controls (40)
p value
6.80 (1.34)
6.69 (1.34)
0.72
determine any relation between the curvature of the cervical spine and height in the dentist group. In a linear regression model and using least squares method, the height variable only remained in the test process (Table 5) when other variables including gender and the weight of subjects were omitted from the model (p < 0.05, F Z 8.67). In other words, it can be stated that the observed difference of the cervical curve value in the dentist group, might be due to the difference of height between men and women working in this profession (p < 0.05). A similar argument is not appropriate for the control group, as there was no significant difference between the height of two genders in this group (p > 0.05).
Discussion Considering the results of the current study, there was no statistically significant difference between the cervical curve of dentists and the control group. In addition, the position of head and neck in the dentist group with two different working histories of 5e8 and 8e12 years was not statistically different. The only difference was found in the head posture of male and female dentists. According to the regression analysis, the difference between cervical curves in the two genders might be related to the difference between the height of men and women in the dentist group. The greater amount of cervical curve in the male dentists compared to females working in this profession might not therefore be due to the abnormal posture of head in men, but to their greater height. Previous studies showed a relationship between neck pain and posture of the head. In a study conducted by Yip et al. (2008), it was shown that there was a direct relationship between neck pain and FHP and the disability resulting from FHP. The results of that study revealed that the craniovertebral angles in subjects with neck pain were smaller compared to the normal subjects (with no pain), so that the greater the angle, the more severe the FHP. A reverse relationship was also observed between this angle and the age of subjects recruited in the Yip et al. study. Additionally, in their study, there was a reverse relationship
Table 3 Comparison of the cervical curve mean values (standard deviation Z SD) between the two genders of dentist and control groups.
Dentists (21 W, 20 M)
Controls (22 W, 18 M)
Dentists
Controls
70.12 (13.95) 169.83 (10.99) 33.05 (3.74) p > 0.18
67.00 (12.62) 166.35 (10.04) 34.98 (3.54)
Female (21) Male (20)
Female (22) Male (18)
W Z Women, M Z Men.
Cervical 6.26 (1.00) curve (cm) p value 0.008
7.35 (1.45) 6.33 (1.15)
0.05
7.12 (1.45)
Evaluating the head posture of dentists
433
Table 4 Comparison of the cervical curve mean values (standard deviation Z SD) in dentists with two different working histories. Working history of dentists
Number
Cervical curve (cm)
p value
5e8 years 8e12 years
20 21
6.84 (1.74) 6.75 (0.86)
<0.84
between the craniovertebral angle and the disability caused by neck pain and its severity in these subjects (Yip et al., 2008). This relationship revealed that the FHP could be a potential reason for neck pain. In the present study, the head posture was measured while none of subjects in the two study groups experienced pain in their neck region, during the 6 months prior to the beginning of the study. The lack of reported pain might be one of the reasons for no significant difference being observed in the head posture in these two groups. In other words, altered head posture in the tested subjects did not cause pain in their necks, something likely to be more easily measurable when pain is experienced and reported by dentists. In fact, it appears evident that prevention of neck pain, requires that therapists prioritize attention to assisting in the avoidance of pain-provoking postural imbalances in dentists (and others), particularly those affecting the neck. Although in the current study it was found that dentists seem to have similar characteristics to people in other professions, it is reported that some professions such as dentistry are subject to earlier alterations in head posture (Ariens et al., 2001; Finsen et al., 1998; McAviney et al., 2005). Accordingly, earlier prevention of abnormal head posture before onset of painful signs and symptoms might be of benefit for dentists to allow them to perform their work, efficiently, for a longer period of time. According to the current results, it is reasonable to attempt to prevent any abnormal head posture before signs and symptoms in appear in younger dentists. This might be achieved using different strengthening exercises for cervical muscles, prescribed by clinicians or therapists. In the current study, it was also revealed that none of two working history of 5e8 and 8e12 years in dentistry led to postural alteration in heads and necks. Considering the age range of dentist group (30e40 years), the working history of minimum 5 and maximum 15 years appears not to be sufficient to result in any postural alterations of the heads in the relatively young subjects. In a study conducted by Finsen et al. (1998), 115 dentists with average age of 45 years and working history of 23 years were studied for the
Table 5 Model
Final model of regression analysis. Substandard Standard coefficients coefficients B
Height 5.38 0.07
t
Sig
Standard error Beta 2.70 0.01
0.58
1.99 0.054 4.51 0.00
risk factors of developing musculoskeletal disorders. Of these dentists, 75% reported pain and discomfort in their neck and shoulders during previous 12 months. In their study, the average age of dentists was 12 years greater than of those in the present study.
Conclusion There was no significant difference between the cervical curve in the dentist and control groups. There was also no difference between the cervical curve values in dentists with two different working history of 5e8 and 8e12 years. Absence of cervical curve alteration in the dentist group compared to the controls might be due to no pain sensation reported among dentists assessed in the current study. In the present study, the alteration of head posture was not sufficient to generate pain sensation in the dentist group. Therefore significantly altered neck lordosis should not be anticipated in dentists aged between 30 and 40 years.
Conflict of interest statement We confirm that the authors have no conflict of interests regarding this paper.
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