J Korean Acad Prosthodont.  2011 Jan;49(1):38-48. 10.4047/jkap.2011.49.1.38.

An influence of operator's posture on the shape of prepared tooth surfaces for fixed partial denture

• Won IJ
• Kwon KR
• Pae A
• Choi DG

• KMID: 2000282
• DOI: http://doi.org/10.4047/jkap.2011.49.1.38

Abstract

PURPOSE
Dentists suffer back, neck and shoulder pain during their careers due to bad operating posture. If dentists have a good operating posture ergonomically, there would be less pain and discomfort in the shoulder and back. Therefore, dentists should learn the Home position which enables dentists to approach a stable posture ergonomically. This study was to compare tooth preparation in the Home position and the Random position, and evaluate the clinical efficacy of the Home position.
MATERIALS AND METHODS
Tooth preparation for fixed partial denture was performed on the maxillary left 2nd premolar and maxillary left 2nd molar at the two different operating positions were compared. The amount of occlusal reduction, marginal width, subgingival margin depth, and convergence angle were measured. A T-test was performed separately to compare the results of the Random position and the Home position.
RESULTS
1. The amounts of average thickness of occlusal reduction on fossa were deficient to the ordered ones in the Random position and the Home position (P > .05). 2. The average subgingival margin depth of prepared margin on maxillary left 2nd premolar, maxillary left 2nd molar were excessive in the Random position than in the Home position. On the maxillary left 2nd premolar, there was no statistical difference in the Random position and the Home position except Distal midline, DL line angle, Lingual midline, ML line angle (P < .05). On the maxillary left 2nd molar, there was no statistical difference in the Random position and the Home position (P < .05). 3. Average convergence angle in the Random position and the Home position were excessive compared to the ordered angle. There was no statistical difference in the Random position and the Home position (P > .05). 4. Analysis of pearson correlation : In the Random position, the amounts of average thickness of occlusal reduction, the average subgingival margin depth of prepared margin, convergence angle were significantly associated with each other (P < .05). But in the Home position, they were not significantly associated with each other (P < .05). 5. The time needed for preparation in the Home position was faster or equal than that of the Random position as time went on.
CONCLUSION
In conclusion, there were no significant differences between Home postion and Random position in measures of occlusal reduction, marginal width, marginal depth, convergence angle. However, preparation time and incidence of damaging adjacent teeth were less in Home position than in Random position. Therefore, if trained properly, Home position which is more ergonomically stable can be adopted for clinical use.

Keyword

Home position; Random position; Tooth Preparation; Operator's Posture

MeSH Terms

Bicuspid
Dentists
Denture, Partial, Fixed
Humans
Incidence
Molar
Neck
Posture
Shoulder
Shoulder Pain
Tooth
Tooth Preparation

Figure

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  Fig. 1. Measuring method for occlusal reduction, width & depth of margine, convergence angle. A: Measuring point of margin width, B: Artificial gingiva position, C: Margin position, a: Thickness of occlusal surface reduction (Cusp tip), b: Thickness of Occlusal surface reduction (Fossa), c: Measuring point of convergence angle (Upper part of margin: 1.5 - 3 mm), d: Upper part of measuring point of margin width (0.5 mm), e: Upper part of artificial gingiva position (0.5 mm), f: Lower part of artificial gingiva position (0.5 mm).

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  Fig. 2. Preparation time of 8 operators in Home position/Random position.

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