[Effects of loupes and microscope on the prosthodontist's posture from ergonomic aspects]

To assess the effects of loupes and microscope on the posture of prosthodontists when preparing the laminate veneer, and to assess the clinical value of loupes and microscope from the ergonomic aspects.

Twenty young prosthodontists from Department of Prosthodontics, Peking University School and Hospital of Stomatology were recruited into this study, which was a prospective, single blind, self-control trials. The research hypothesis was concealed and the participants were deceived about the precise purpose of the study to counterbalance the lack of direct blinding. The prosthodontists prepared laminate veneers of open window type in the artificial dental model, under routine visual field (control group), 2.5× headwear loupes (loupes group), and 8× operating microscope (microscopic group) by turning. The participants were photographed from profile view and front view. Thereafter, the subjective assessment was performed by themselves using the visual analogue score (VAS). The expert assessment was performed by two professors using modified-dental operator posture assessment instrument on the basis of photographs of the profile view and front view.

The subjective assessment scores for the control group, loupes group and microscopic group were 4.55±1.96, 7.90±1.12, and 9.00±0.92, respectively. There was significant difference between the three groups' subjective scores (P < 0.05). The expert assessment scores for the control group, loupes group and microscopic group were 16.38±1.52, 15.15±1.30, and 13.60±0.88, respectively. There was significant difference between the three groups' expert assessment scores (P < 0.05). Specifically, the three groups' expert assessment scores were significantly different (P < 0.05) in trunk position (front to back) (1.33±0.41, 1.03±0.11, 1.00±0.00), head and neck position (front to back) (2.75±0.38, 2.13±0.36, 1.23±0.38), elbows level (1.38±0.43, 1.40±0.45, 1.13±0.22), and shoulders level (1.43±0.41, 1.23±0.34, 1.13±0.28). Thereinto, the microscopic group was better than loupes group in head and neck position (front to back) and elbows level (P < 0.05).

Loupes and microscope improve the posture of the prosthodontist when preparing the laminate veneer, in which the microscope is better than loupes. Therefore, the magnification devices have clinical value from the ergonomic aspects.