Table 3.

Ergonomic interventions and their effects in the included studies reporting ergonomic interventions to prevent MSDs among dental professionals (n = 11).

Reference	Type of Prevention	Description of Intervention	Effect of Intervention	Analyzed Body Regions
Ergonomic Dental Chair
Dable 2014 [17]	Setting prevention	Intervention: Ergonomic dental chairs; magnification loupes; lecture in ergonomics. Facts: 3 different dental chairs were analyzed (30 dental students in each group)—(a) saddle stool, (b) conventional chair with back rest, (c) conventional chair without back rest. All investigations on working posture were carried out without and with magnification loupes. All students were lectured on ergonomic posture. After 3 months of training, the assessment procedure started; it lasted for 3 days. Survey instruments: Rapid Upper Limb Assessment (RULA) & videotapes Control: Study participants were their own controls (allocated dental chair without vs. with magnification loupes) Length: 3 months Follow up: In 3 days MSD status of participants: Is not stated, but there is a hint that some participants had mild MSDs before the intervention	-The use of the 3 different dental chairs (without and with magnification loupes) had various effects on working posture of dental students, e.g., The study showed significantly lower RULA scores for the saddle stool with magnification used (1.57 ± 0.50) as compared to the conventional chairs without magnification used (7.03 ± 0.49); for the saddle stool with magnification, the scores were very acceptable (p < 0.01) 🡪The use of the ergonomic saddle stool with magnification loupes was more suitable for dental students and produced a better working posture than the use of the conventional chairs without magnification loupes 🡪The use of the ergonomic saddle stool and loupes significantly improved the working posture of dental students (p < 0.01) 🡪Dental students reported to have fewer or no MSDs after using the saddle stool as they found it more comfortable to work in this chair than in the conventional chairs -The use of magnification loupes influenced the working posture of dental students for every dental chair, e.g., The study reported significantly lower RULA scores for the conventional chairs with magnification (CC1 5.63 ± 0.49 and CC2 5.07 ± 0.46) than in the groups without it (6.57 ± 0.50 and 6.96 ± 0.56) 🡪The use of magnification loupes significantly improved the working posture of dental students (p < 0.01) -When the conventional chairs were compared, it was seen that the back rest does not make any difference in improving the working posture of dental students (p > 0.05) -The study reported that the use of the ergonomic saddle stool could support the lumbar region and maintain the natural curvature of the lower back; at the same time, magnification could bring a clearer view near to the operator instead of the operator hunching over to get the view	-Arm -Leg -Neck -Trunk -Wrist
Hallaj 2016 [19]	Setting prevention	Intervention: Ergonomic dental chair with arm support Facts: A new designed arm support device was tested Survey instruments: Rapid Upper Limb Assessment (RULA) and photographs, feedback questionnaire with self-developed questions Control: Study participants were their own controls Length: 1 week Follow up: Time is not stated MSDs status of participants: Is not stated	-The use of an ergonomic dental chair with arm support correlated with the working posture of dentists, e.g., the overall RULA score (average value of all participants) was 3.14 after the use of an ergonomic dental chair with arm support 🡪The use of an ergonomic dental chair with arm support led to positive changes in the working posture of dentists -The use of an ergonomic dental chair with arm support had the following effects on the working posture of dentists, e.g., the combined bending and twisting of the back decreased by 13.8% after using the arm support device; the twisting, turning, grapping and wringing actions with fingers or arms bent decreased by 20.7%; excessive bending up or down of the wrist decreased by 41.38%; pinch grip decreased by 17.2%; the pressure on the neck and shoulder while performing dental tasks decreased by 79.3% 🡪The use of an ergonomic dental chair with arm support had a significant positive impact on the working posture of dentists 🡪Dentists reported more comfort by using the arm support device -The working posture can further be improved by adjusting both the patient’s and dentist’s chairs, to support the dentist’s neck during work -The RULA score indicated that by using the arm support device, the body posture of dentists is almost in the correct ergonomic position -Dentists stated that they prefer to have only one side arm supported	-Arm -Back -Elbow -Head -Neck -Shoulder -Wrist
Magnification Loupes
Hayes 2014 [20]	Setting prevention	Intervention: Magnification loupes Facts: Galilean flip-up style loupes with 2.5 x magnification were used. The convergence and working angles of the magnification loupes were adjustable. Survey instruments: Disabilities of the Arm, Shoulder and Hand (DASH) Questionnaire, physical assessments based on validated protocols Control: Dental hygiene students not wearing magnification loupes Length: 6 months Follow up: After 6 monthsMSDs status of participants: All study subjects experienced MSDs before the intervention, subjects with chronic MSD conditions were not included in the study	-The use of magnification loupes in dental care was associated with symptoms of MSDs among dental hygienists, e.g., DASH scores for dental hygienists (intervention group) were higher than for dental hygiene students (control group) (8.56 ± 9.64 vs. 4.99 ± 6.25) at baseline; this trend reversed after the intervention (5.17 ± 5.29 vs. 7.84 ± 8.73) 🡪Following the intervention, the DASH scores for dental hygienists decreased, and those for dental hygiene students increased 🡪The use of magnification loupes significantly reduced symptoms of MSDs among dental hygienists (p < 0.05) -Levels of self-reported upper extremity pain and disability improved in the intervention group when comparing baseline to post-intervention, while symptoms of MSDs in upper extremities worsened in the control group -Changes in musculoskeletal function were minimal among dental hygienists -Dental hygienists reported less pain in the shoulder, arm and hand regions after the intervention	-Arm -Hand -Shoulder
Hayes 2016a [21]	Setting prevention	Intervention: Magnification loupes Facts: Galilean flip-up style loupes with 2.5 × magnification were used. The convergence and working angles of the magnification loupes were adjustable. Survey instruments: Neck Pain and Disability Scale (NPDS), physical assessments based on validated protocols Control: Dental hygiene students not wearing magnification loupes Length: 6 months Follow up: After 6 months MSDs status of participants: All study subjects experienced MSDs before the intervention, subjects with chronic MSDs conditions (persistent pain for at least 3 months) or with pre-existing MSDs unrelated to occupational factors were not included in the study	-The use of magnification loupes correlated with neck pain and disability in dental hygienists, e.g., The study revealed no significant interactions between time and treatment (p > 0.05); there was no change in mean NPDS scores between baseline and follow up for the intervention group (14.00 ± 12.49 vs. 14.00 ± 11.05), while the control group reported an increase in perceived neck pain at follow up (14.97 ± 16.91 vs. 15.90 ± 13.54) (p > 0.05) 🡪The use of magnification loupes created no significant changes in neck pain and disability in dental hygienists over time 🡪The use of magnification loupes had no significant effect on improving symptoms of neck pain and disability in dental hygienists, but a slightly positive impact can be assumed	-Neck
Maillet 2008 [24]	Setting prevention	Intervention: Magnification loupes Facts: The magnification loupes were Hires flip-ups, complete with head straps and side shields. The frames were all standard titanium frames, slate in color. Orascoptic also provided three rigid headbands to allow for prescription eyeglass wearers. The headbands and standard frames had interchangeable working lengths to allow for portability within the group. The magnification for all was 2.5 ×. The study consisted of two parts: preliminary study and formal study that were implemented in 2005. Group 1 wore the loupes for the first session and worked without them for the second session, while Group 2 worked without loupes for the first session and with loupes for the second. Survey instruments: Posture Assessment Instrument (PAI), Posture Assessment Criteria (PAC), post-study-survey with self-developed questions and videotapes Control: Study participants were their own controls (2 sessions each with and without magnification loupes) Length: 7 months Follow up: After 7 monthsMSDs status of participants: Is not stated	-The use of magnification loupes showed effects on the working posture of dental hygiene students, e.g., The results of the first session indicated that Group 1 (wore the magnification loupes) had significantly better ergonomic scores than Group 2 (did not wear the magnification loupes). Group 1 had a mean score of 5.69 ± 2.17 points from the ideal posture, compared with a mean score of 10.76 ± 4.30 points for Group 2 (t = 4.37, df = 23, p < 0.001); in the second session, Group 2 (wore the magnification loupes) had significantly better ergonomic scores than Group 1 (did not wear the magnification loupes). Group 2 had a mean score of 7.83 ± n/a points from ideal posture, compared with a mean score of 10.13 ± n/a points for Group 1; in the end, all students wearing magnification loupes showed significantly better ergonomic scores than all students not wearing magnification loupes (6.4 ± 2.61 vs. 10.8 ± 4.24, t = 6.66, df = 34, p < 0.000001) 🡪The use of magnification loupes significantly improved the working posture of dental hygiene students in both groups (p < 0.001) 🡪An early introduction in magnification loupes was more effective in improving the working posture -The majority of students were aware of the improved posture, perceived that the quality of their work increased when wearing magnification loupes and would wear loupes regularly if they were provided	-Arm -Head -Hip -Leg -Neck -Shoulder -Trunk
Prismatic Spectacles
Lindegård 2012 [22]	Setting prevention	Intervention: Prismatic spectacles; lecture in ergonomics Facts: The prismatic glasses include optometric correction. The ergonomic education (lecture in ergonomics) includes a comprehensive 1.5 h information session about dental ergonomics including working postures, working technique and visual ergonomics. All study participants underwent the education. The assessments lasted 4 months. Survey instruments: Borg’s RPE Scale (modified), inclinometers and questionnaires Control: Dentists and dental hygienists not wearing prismatic spectacles Length: 12 months Follow up: CG: 7 and 8 weeks after the education, IG: 9 to 11 weeks and 12 months after the intervention MSD status of participants: Is not stated	-The use of prismatic glasses in dental care had an impact on the working posture of dentists and dental hygienists, e.g., at follow up, the head flexion was reduced in both groups but more pronounced in the intervention group (received prismatic glasses) than in the control group (did not receive prismatic glasses) (8.7° vs. 3.6°, p < 0.01); regarding the neck flexion, a significant reduction was seen for the intervention group, while a smaller and insignificant reduction was present in the control group (8.2° vs. 3.3°, p < 0.05); in the intervention group, there was a significant decrease (4 units) in the perceived exertion of the head and the neck at follow up, and the corresponding decrease for the control group was 2 units (n. s.) 🡪The use of prismatic glasses made significant positive changes in the working posture of dentists and dental hygienists for the head and the neck regions 🡪The use of prismatic glasses reduced complaints in the head and the neck caused by dental work 🡪The use of prismatic glasses facilitated the performance of dental work (🡪 80% of the participants reported that the prismatic glasses were feasible to wear during work and considerably facilitated dental work) 🡪The use of prismatic glasses decreased the risk of exposure to high risk working postures in the neck during dental work	-Head -Neck
Lindegård 2016 [23]	Setting prevention	Intervention: Prismatic spectacles Facts: All participants in the intervention group were given an eye test for adjusting the prismatic glasses individually. Survey instruments: Nordic Musculoskeletal Questionnaire (NMQ), Work Ability Index (WAI), questionnaire with self-developed questions for the follow up assessment, physical assessments based on Health Surveillance in Adverse Ergonomics Conditions (HECO) protocols Control: Remaining dental personnel not receiving prismatic spectacles Length: 12 months Follow up: After 12 months MSE status of participants: All study subjects experienced MSDs before the intervention (at baseline); the intervention group reported a higher prevalence of MSDs and clinical diagnoses at baseline than the control group	-The use of prismatic glasses during clinical dental work correlated with symptoms of MSDs in dental personnel, e.g., the study revealed in the intervention group (received prismatic glasses) significant improvements regarding clinical diagnoses (p < 0.05), perceived exertion (p < 0.01), self-reported pain (p < 0.05) and self-rated work ability (p < 0.05) compared to the control group (did not receive prismatic glasses) 🡪The use of prismatic glasses significantly improved symptoms of neck and/or shoulder pain in dental personnel 🡪The use of prismatic glasses significantly reduced the risk of developing MSDs (including neck and shoulder pain) and decreased perceived muscular exertion during the performance of dental work -The prismatic glasses enable the dental personnel to work in a more upright position with a less bent neck that promotes an ergonomic working posture with a lower risk of developing muscular complaints and symptoms of MSDs -Study participants reported that wearing the prismatic glasses simplified their daily work and strengthened their work ability in dental care 🡪The greatest advantage of the prismatic glasses was found during root-fillings and other vision-demanding tasks in constrained working positions	-Neck -Shoulder
Dental Instruments
Rempel 2012 [25]	Setting prevention	Intervention: Dental instruments Facts: Instrument 1 weighed 14g and had an 11mm diameter handle, Instrument 2 weighed 34g and had an 8mm diameter handle. Instrument 1 was made from black plastic, and Instrument 2, from steel plated with black coating. Randomization took place at the level of the dental office. Survey instruments: Online questionnaires at baseline, weekly during the intervention and at follow up Control: 2 intervention groups with own controls (use of light/wide vs. heavy/narrow instrument) Length: 5 months Follow up: After 5 months MSDs status of participants: Study subjects experienced MSDs before the intervention; subjects who received any treatment of MSDs before the intervention were not included in the study	-The use of a lightweight dental instrument with a wide diameter had impacts on symptoms of MSDs in dentists and dental hygienists, e.g., the unadjusted pain scores improved more for study participants who used Instrument 1 (light and wide) than for those who used Instrument 2 (heavy and narrow) for the wrist/hand (0.40 ± 0.11 vs. 0.14 ± 0.11, n. s.), arm (0.20 ± 0.09 vs. 0.06 ± 0.09, n. s.) and shoulder (0.51 ± 0.16 vs. 0.19 ± 0.15, p < 0.05) regions; after adjusting for confounders (e.g., age and occupation), the authors found a significant difference between the two groups only for the shoulder region (0.52 ± 0.17 vs. 0.19 ± 0.16, p < 0.05) 🡪The use of the lightweight dental instrument with a wide diameter significantly reduced symptoms of shoulder pain in dentists and dental hygienists 🡪The improvements in symptoms of MSDs were greater among those who used the lightweight instrument with a wide diameter 🡪The use of the lightweight instrument with a wide diameter was more suitable for dental work than the use of a heavyweight instrument with a narrow diameter, even if symptoms of MSDs improved in both groups -The number of nights awakened with finger numbness improved more for participants assigned to the lightweight instrument with a wide diameter than they did for those assigned to the heavyweight instrument with a narrow diameter -The follow up survey ratings regarding the usability of the instruments were more positive for participants who used the lightweight instrument with a wide diameter than they were for those who used the heavyweight instrument with a narrow diameter	-Arm -Hand -Shoulder -Wrist
Training Course in Ergonomics
Dehghan 2016 [16]	Behavioral prevention	Intervention: Training course in ergonomics Facts: The intervention includes 4 sections: 1. knowledge and training about ergonomics (training sessions), 2. workstation modification (instructions how to modify working postures), 3. training and surveying ergonomics at the workstation (working conditions were evaluated, discussed and modified), 4. regular exercise program (stretching movements were explained by a physiotherapist). Survey instrument: Nordic Musculoskeletal Questionnaire (NMQ) Control: Dentists not receiving the ergonomic intervention program Length: 2 months Follow ups: After 3 and 6 months MSD status of participants: Is not stated	-Participation in the ergonomic intervention program influenced the prevalence of MSDs in dentists, e.g., dentists who were in the intervention group had lower prevalence rates of MSDs for all surveyed body regions at 3 and 6 months after the program than dentists who were in the control group; e.g., the prevalence of knee pain was 24% in the intervention group and 36% in the control group 6 months after the program (p < 0.01); the prevalence of shoulder pain was 44% and 80% (p < 0.05), and of neck pain, 62% and 84% (p < 0.01); prevalence rates of MSDs decreased over time in the intervention group for all body regions and in the control group only for the back region; e.g., in the intervention group, the prevalence of knee pain was 30% before and 24% 6 months after the program (p < 0.01); the prevalence of shoulder pain was 60% and 44% (p < 0.01), and of neck pain, 78% and 62% (p < 0.01); therefore, prevalence rates of MSDs increased over time in the control group for almost all body regions 🡪The ergonomic intervention program had a positive effect by significantly reducing the prevalence of MSDs in dentists 🡪Theoretical and practical knowledge about ergonomics and workplace modification in dental care can significantly improve the experience of MSDs in dentists -Almost all surveyed dentists (98%) who were in the intervention group agreed with the multifaceted ergonomic intervention program and experienced a positive benefit, finally had significantly fewer MSDs after the intervention and were able to improve their workplace ergonomics through gained knowledge	-Arm -Back -Foot -Knee -Neck -Shoulder -Thigh -Wrist
Farrokhnia 2018 [18]	Behavioral prevention	Intervention: Training course Facts: The educational intervention included a brief face-to-face teaching and distributing pamphlets Survey instruments: Cornell Musculoskeletal Discomfort Questionnaire (CMDQ) and questionnaire with self-developed questions Control: Study participants were their own controls Length: More than two days (probably a few weeks) Follow up: After 2 months MSDs status of participants: Most of the study subjects (87%) experienced MSDs before the intervention; some study subjects (13%) were free of MSDs at this time	-Participation in the educational intervention correlated with the symptoms of MSDs in dentists, e.g., at follow up the study results revealed a significant reduction in means for MSDs for the neck (10.97 ± 20.44 vs. 7.91 ± 17.01, p < 0.01), right shoulder (8.85 ± 19.76 vs. 5.24 ± 13.51, p < 0.01), left shoulder (5.80 ± 17.21 vs. 2.95 ± 9.33, p < 0.01), upper back (6.92 ± 17.59 vs. 4.53 ± 14.35, p < 0.01) and right wrist (5.12 ± 13.35 vs. 3.81 ± 12.96, p < 0.05) regions; before the intervention, 87% of dentists had problems with MSDs; after the intervention, it was 81% 🡪Through participation in the educational intervention, symptoms of MSDs significantly improved in dentists 🡪The educational intervention had the greatest impact on body regions like the neck, shoulder, back and wrist 🡪The educational intervention had positive effects on present symptoms of MSDs and contributed to reducing MSDs in dentists by teaching good working postures, regular rest breaks and stretching exercises -Further analyses showed that more short breaks between patients resulted in lower MSDs (p < 0.05) and increased age led to more neck pain (p < 0.05)	-Arm -Back -Hip -Knee -Leg -Neck -Shoulder -Thigh -Wrist
Koni 2018 [14]	Behavioral prevention	Intervention: Training course in ergonomics Facts: The intervention comprised several training sessions, each of 60 minutes in length. The program was organized by the University of Trieste, School of Dentistry and Physiotherapy degree course. The course taught the participants in basic knowledge on working postures and MSDs and in prevention strategies against symptoms of MSDs. Survey instruments: Verbal Numerical Scale (VNS), photographs and questionnaires Control: Study participants were their own controls Length: More than two days (probably a few weeks) Follow up: After 3 months MSDs status of participants: Is not stated, but there is a hint that all study participants had some form of MSDs before the intervention	-Participation in the training course in ergonomics was associated with symptoms of MSDs in dental students, e.g., 49% of dental students reported an improvement of symptoms of MSDs 3 months after the training course (p < 0.05), but 17% reported a worsening of symptoms; women, younger students and those who reported less pain at the beginning of the study experienced fewer improvements of symptoms of MSDs after the intervention (OR = 0.48, 95% CI = 0.22-1,04; OR = 0.93, 95% CI = 0.83–1.03; OR = 0.94, 95% CI = 0.89–0.99) 🡪The training course showed mutual results, but a clear benefit for half of the surveyed dental students can be derived 🡪The training course is an effective option to reduce symptoms of MSDs in dental students through improving knowledge of prevention strategies -Of the dental students, 25.6% reported more dynamic working postures at follow up 🡪The training course effectively improved working postures in dental students -Of the dental students, 87.7% changed their habits in dental work after the training course following its suggestions for a better working posture and prevention strategies against MSDs 🡪The training course was well accepted and provided practical skills for dental students	-Back -Elbow -Foot -Hand -Head -Hip -Knee -Shoulder

Abbreviations: CC1: conventional chair 1; CC2: conventional chair 2; CG: control group; CI: confidence interval; DASH: Disabilities of the Arm, Shoulder and Hand; df: degrees of freedom; IG: intervention group; MSDs: musculoskeletal diseases and pain; NPDS: Neck Pain and Disability Scale; n/a: not applicable; n. s.: not significant; OR: odds ratio; RPE: Received Perception of Exertion; RULA: Rapid Upper Limb Assessment.