The stress distribution of a primary molar tooth restored with stainless steel crown using different luting cements.

BACKGROUND: The aim of this study is to evaluate the stress distributions of a primary molar tooth restored with a stainless steel crown (SSC) using resin and glass ionomer luting cements by Finite Element Analysis (FEA). METHODS: Original DICOM data of a primary molar was used to create a 3D model. One model was prepared as a tooth model with SSC. A 30 µm cement layer was used in model. Two different luting cements were tested in the study: self-cure adhesive resin cement, and glass ionomer cement. Vertical and oblique loads of 330 N were applied to simulate maximum bite force and lateral forces in the occlusal contact areas of the models. Maximum von Mises stress values in the models were evaluated as MPa. RESULTS: The maximum von Mises stress value was observed in the force application and general occlusal contact areas for all models. The maximum von Mises stress values were higher in the tooth model with SSC using self-cure adhesive resin cement (478.09 MPa and 214.62 MPa) than in the tooth model with SSC using glass ionomer cement (220.06 MPa and 198.72 MPa) in both vertical and oblique loading, respectively. CONCLUSIONS: Depending on the magnitude of the bite force on the SSC, fracture of the luting cement materials could occur if the stress exceeds the endurance limit of the luting cement. Cementation with glass ionomer cement may help to reduce stress levels in SSC restorations of primary molars in children.

Evaluation of the effect of different post materials and adhesive systems on the bonding strength of short-post technique for primary teeth.

BACKGROUND: The most important process in treating grossly decayed teeth, including decay in the pulp, is the ability to hold a retainer in for a short time. AIM: The aim of this study was to investigate the bond strengths of different adhesive systems and post materials on primary teeth. DESIGN: One hundred and twenty extracted maxillar primary central incisor teeth were randomly divided into two main groups (total-etch and self-etch adhesive systems) and five subgroups (1: control-nanohybrid composite resin, 2: pre-impregnated glass fiber, 3: unsaturated glass fiber, 4: polyethylene fiber, 5: short-fiber reinforced composite resin). The push-out test was performed using a universal testing machine with a crosshead speed of 0.5 mm/min. RESULTS: No statistically significant difference was detected between the two different adhesive systems and five different materials in terms of the maximum values measured for fractures in the specimens when both the adhesive materials and the short-post materials were evaluated separately (P > 0.05). However, as a result of multiple comparisons made, it was found that statistical differences between the groups applying the total-etch adhesive system occurred in Groups 3 and 5. The highest push-out test values were measured in Group 5 and Group 1, and the lowest value in Group 3. Although the fracture type distribution in the total-etch adhesive system groups was not statistically different based on the material used (χ2  = 11,865; P = 0.309), the self-etch adhesive systems did show differences (χ2  = 28,463; P < 0.001). Both the total-etch and the self-etch adhesive system groups showed mostly adhesive failures. CONCLUSION: The fiber-reinforced and nanohybrid composite resin had higher values in the short-post technique, and there was no significant difference between the different fiber posts.

Assessment of oral hygiene and periodontal health around posterior primary molars after their restoration with various crown types.

OBJECTIVE: To compare the time-dependent changes in oral hygiene and periodontal health after restoring primary posterior molars with a traditional stainless steel crown (SSC) or an aesthetic crown using various measures of periodontal health and oral hygiene. DESIGN: This investigation was a randomized, non-blinded prospective controlled clinical trial in which 264 crowns of different types were fitted onto the first and/or second primary molars of 76 children. The oral hygiene and the gingival health of the restored teeth and the antagonistic teeth were evaluated clinically and radiographically at 3- and 6-month intervals for 18 months after fitting the crowns. RESULTS: The periodontal health of the control teeth was better than that of the remaining 215 restored teeth. The oral hygiene, as measured by the simplified oral hygiene index, and gingival health, as measured by the gingival index and the volume of gingival crevicular fluid, of the restored teeth, irrespective of crown type, progressively increased during the 18-month study period. CONCLUSIONS: Oral hygiene and gingival health around a restored primary tooth deteriorate with time. Our results suggest that SSC, an open-faced SSC, or a NuSmile(®) pediatric crown should be the preferred crown type for restoring posterior primary teeth.