The objective of this study was to investigate the effect of excessive occlusal loading on stress distribution on four type of cervical lesion, using a three dimensional finite element analysis (3D FEA).The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. Four different lesion configurations representative of the various types observed clinically for teeth were studied. A static point load of 500N was applied to the buccal and lingual cusp (Load A and B). The principal stresses in lesion apex, and vertical sectioned margin of cervical wall were analyzed.The results were as follows 1. The patterns of stress distribution were similar but the magnitude was different in four types of lesion. 2. The peak stress was observed at mesial corner and also stresses concentrated at lesion apex. 3. The compressive stress under load A and the tensile stress under load B were dominant stress. 4. Under the load, lesion can be increased and harmful to tooth structure unless restored. [J Kor Acad Cons Dent 31(5): [359][360][361][362][363][364][365][366][367][368][369][370] 2006]
The purpose of present study was to evaluate the influence of different base materials on the marginal integrity of posterior direct composite resin restorations. Conventional mesio-occluso-distal(MOD) cavity preparations, with margins in enamel and dentin, were prepared in 24 extracted human mandibular molars and randomly divided into four equal groups. One of three base materials (RMGI, compomer, flowable resin) was placed on the pulpal floors of the teeth of the groups. One group of teeth, which served as the control group, was not given any base material. Then, all teeth were restored with composite resin. The micromorphology of the tooth/restoration interfaces along the entire surfaces of the restorations was quantitatively analyzed using microscope at 150 magnifications immediately after finishing and after completion of thermo-mechanical stress. Marginal adaptation was assessed along the entire margin and % perfect margin (%PM) was calculated. The %PMs before and after thermo-mechanical stress in the groups were compared with Two- way ANOVA with Tukey test at the 95% confidence level. Before thermo-mechanical stress, there was no difference in marginal adaptation between groups. After the thermo-mechanical stress, the RMGI group showed the highest marginal adaptation rate among the tested groups. In compomer and flowable resin groups, the marginal adaptation was lower after thermomechanical stresses than before the stress (p<0.05).
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