[Photoelastic stress analysis at the metal-enamel junction of the anterior adhesive bridge on non-prepared teeth in eccentric jaw position].
To study the stress involved at the metal-enamel junction of an adhesive bridge during the eccentric movement of the mandible, the author calculated the values of principal stress and maximum shearing stress, and determined the stress distribution at the adhesive surface which exists between retainer and enamel, for which an unprepared canine and a centaral incisor, using a three-dimensional photoelastic experiment. Based on the assumed eccentric movement of the mandible, three models with loading at different parts of the adhesive bridge were used for the experiment: Model 1 with loading only on the central incisor, Model 2 with loading on the pontic of the lateral incisor and Model 3 with loading only on the canine. The results were as follows. (1) Models 1 and 3 showed stress concentration directly under the loading point, where the compressive stress was 610 kgf/cm2 in Model 1 and 610 kgf/cm2 in Model 3. (2) Model 1 showed distribution of stress of 30-80 kgf/cm2 at the metal-enamel junction of the canine, while in Model 3 the stress of 80-150 kgf/cm2 was distributed at the metal-enamel junction of the central incisor. Loading only on the canine produced higher levels and broader distribution of stress than loading only on the central incisor. (3) Model 2 showed distribution of stress of about 60 kgf/cm2 at the metal-enamel junction of the central incisor and canine. Extremely intense stress, 250 kgf/cm2, was noted in the canine slice contiguous to the pontic. Stress as high as 70 kgf/cm2 was also observed in the central incisor slice contiguous to the pontic. (4) The maximum shearing stress values were 305 kgf/cm2 in Model 1 and 325 kgf/cm2 in Model 3 at the sites directly under the loading point, showing similarly high levels. (5) A comparative investigation of the maximum shearing stress appearing at the metal-enamel junction among the models showed that the distributed maximum shearing stress in Model 3 was about twice that in Model 1. (6) Model 2 had the maximum shearing stress, which was located toward the pontic in the canine, with an intensity closed to the shearing strength of currently available adhesive resin cement, suggesting a high risk of desquamation at this site.
Ohtsuka
Y
Y
Kamezawa
H
H
Yokozuka
S
S
D003722:Dental Alloys; D001840:Dental Bonding; D003737:Dental Cavity Preparation; D003766:Dental Occlusion; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003830:Denture, Partial, Fixed; D006801:Humans; D007180:Incisor; D008409:Mastication; D013499:Surface Properties
D003722:Dental Alloys; D003776:Dental Porcelain