Quantitative Analysis of Proximal Wear of Human Enamel in vivo

Objectives: To investigate the proximal enamel wear loss in caries-free young dentition.

Methods: Epoxy models of upper and lower dentitions of nineteen volunteer subjects without TMJ disorder (aged 18-22 years old) were taken at an annual recall over a 3-year period. Four of the nineteen subjects were followed up over a 7~11-year period. The occlusal force was measured at 2-year-recall by Dental Prescale and Occluzer System (Fuji Film Co., Japan). Proximal wear loss between second premolar and first molar was measured on the models as follows. Bearing balls (1mm in diameter) were placed on the occlusal pits of the objective teeth. The distances between shining points on the top surface of each ball were measured on the profile projector (Nikon, Japan) at x10. Proximal wear loss was calculated from the changes of the distance at each recall period.

Results: The mean 3-year proximal wear loss of the subjects was 46.5µm(max 102.2µm, min 9.8µm). There was no difference among subjects(p=0.27) or region(p=0.23)(two-way ANOVA). The mean occlusal force was 438.6N(max 850N, min 197N). There was no correlation between 3-year proximal wear loss and occlusal force(r=-0.12). Long-term proximal wear loss of four subjects were 50.5~72.9µm at 7-year, 140.9~168.7µm at 9-year, 81.4~139.4µm at 10-year and 111.5~257.1µm at 11-year. The enamel wear rate on proximal surface was not constant due to various facters.

Conclusion: The average of 3-year proximal wear between second premolar and first molar was 46.5µm(15.5µm/year) in caries-free dentition of young subjects. The proximal enamel wear was not correlated with occlusal force.

Supported by Grant-in-Aid for Young Scientists(B)17791353 from Japan Ministry of Education, Culture, Sports, Science and Technology and Grant-in-Aid for Scientific Research(C)19592196 from JSPS.