[The causes of longitudinal fracture of the upper complete denture base]

Laying the strain gauge on the design areas of palatal base and frenum labiorum of complete dentures and simulating the different shapes of notch of frenums by the photoelastic mould. The test of the base condition under static and dynamic load by electrical measurement method was carried out. The longitudinal breaking line on the front part of the palatal base was first observed. The causes of breaking may be due to: the weak effect of notch of frenum labiorum; stress concentration on the front part of the base; material fatigue caused by the repeated alternate force and the strength of base material reduced by unsuitable processing.