Aim: A three-dimensional finite element analysis (3D FEA) study for measuring optimum elasticity using thickness and load data collected from elderly edentulous patients when feeling pressure-related pain. Materials and methods:Tested elasticity as in a previous report ("measured elasticity") is measured using an able FEA ("optimum elasticity"). A two-way analysis of variance (ANOVA) was performed and Pearson's correlation coefficients were obtained. Pearson's correlation coefficients were also determined for thickness (mm), measured elasticity, and optimum elasticity (MPa) in different experimental areas. Finally, the von Mises stresses and subsidence (mm) results of the FEA were tested using measured elasticity; those using optimum elasticity were measured with a two-way ANOVA.Results: Seventeen patients were studied. Optimum elasticity was significantly lower than measured elasticity (p < 0.05). Correlations were found in all three palatal areas (p < 0.01). A correlation between thickness and measured elasticity was found at the midpoint (p < 0.05) but not at the median or lateral sections. No correlation between thickness and optimum elasticity was found in any of the three palate areas. Finite-element analysis results using measured elasticity indicated no differences in von Mises stress at any site when compared with FEA results using optimum elasticity. Subsidence was significantly smaller (p < 0.05). Conclusion:It is difficult to estimate elasticity using the thickness of denture-supporting tissue and necessary to optimize elasticity in all palatal areas when using an FEA. We established a method to measure elasticity.Clinical significance: If it were possible to optimize elasticity in a 3D FEA of maxillary denture-supporting tissue, it would become possible to design an optimal relief area through simulation. This would reduce the burden on the patient, such as the need for adjustment after wearing dentures, and improve quality of life.

Aim: A new maxillary palatal plate-form device that simultaneously measures clenching force and subsidence of the palatal mucosa at the onset of jaw clenching pain was developed to ascertain the effect of median palatal plate relief on denturebearing ability. Materials and methods: In 15 dentulous subjects, pseudopalatal plates were affixed to the palatal mucosa; anterior splints were affixed as maxillary references for measuring subsidence upon transmission of the clenching force through a pressurizing splint affixed to the mandible. The relief at the median palatal plate was categorized as: No-relief, 0.23 mm relief, and 0.46 mm relief. Subjects clenched their jaws until they experienced pain. The clenching force and subsidence of the palatal mucosa were simultaneously measured and compared across relief categories, and their relationship to the extent of relief at the onset of pain was evaluated. Results: At the onset of pain, both clenching force and subsidence of the palatal mucosa in the relief conditions were significantly greater than those in the no-relief condition (p < 0.05). In some patients, both clenching force and subsidence of the palatal mucosa decreased with increase in relief. Conclusion: Relief at the median palatal plate effectively increases the bearing ability of the palatal part. However, the range and extent of relief might vary, depending on oral conditions. Clinical significance: Using this approach, the relief area of maxillary full dentures suitable for individual patients was determined in an objective and convenient manner and the accuracy of denture treatments was improved. This could improve the quality of life of patients wearing dentures.