[Restoration of non-carious cervical lesions in the first maxillary premolar:a three dimentional finite element study].

PURPOSE

To investigate the influences of factors such as cavity depth,shape,restorative materials and occlusal adjustment on the restoration of non-carious cervical lesions(NCCL) in the first maxillary premolars.

METHODS

3-D finite element models of adult first maxillary premolars which had cavities of different depths and shapes in buccal cervical region were built. The models were restored and divided into three groups: glass ion cement (GIC), amalgam and composite resin. The stress profiles and distribution in normal occlusion and malocclusion were evaluated from vertical to lateral loading.

RESULTS

In normal occlusion, there was mainly tensile stress and uniform distribution on the buccal cervical margin, compressive stress appeared when approaching to tooth root; in malocclusion, there was mainly greater concentrated tensile stress on the buccal cervical margin than normal occlusion. In all the two occlusions, lateral loading increased stress concentration and value comparing with vertical loading. The contrast between different cavity depths showed significant positive correlation between stress value of restoration and cavity depth. The wedge, rectangle and rounded shaped cavity in the cases of small cavities depths (0.5, 1.0mm) exhibited no difference. For larger cavity depth (1.5mm), the stress of rectangular cavity was greater than the wedge (about 4 times), but no difference between the wedge and the rounded. The interface stress value of GIC and composite resin model was smaller than that of amalgam the latter was 3-9 times greater than the former two. The GIC was slightly smaller than the resin (0.2-2.4 MPa).

CONCLUSIONS

For small cavity depth, cavity shape is not the primary factor affecting the treatment of NCCL. The rectangular cavity isn't suitable for large defect. There is positive correlation between stress value of restoration and cavity depth. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality(08DZ2271100).