In vitro investigation on extensively destroyed vital teeth: is fracture force a limiting factor for direct restoration?

To evaluate the in vitro fracture load of extensively damaged vital teeth after either direct or indirect restauration, severe tooth substance loss was simulated for 96 molars. Subsequently, two cavities were prepared with little (design 1) or more substantial (design 2) residual tooth support. All molars were provided with a 2-mm ferrule design and then divided into 12 test groups based on their occlusal surface size. They were restored with composite or with either of two types of single crown (cast metal or milled zirconia). After thermal ageing (10,000 cycles at 6.5 and 60 °C), 1.2 million cycles of chewing simulation were applied (64 N). Maximum fracture load was determined with a loading angle of 45°. Statistical analysis was performed by use of Kaplan-Meier modelling, Student's t-tests, one-way anova, post hoc Tukey's HSD tests and linear regression analysis. Regarding mean fracture load without ageing, the indirect restorations outperformed composite (design 1: direct: 508 ± 123 N, indirect: 741 ± 248 N; design 2: direct: 554 ± 167 N, indirect: 903 ± 221 N). After artificial ageing, however, these differences were no longer significant (design 1: direct: 328 ± 189 N, indirect: 506 ± 352 N; design 2: direct 399 ± 208 N, indirect 577 ± 292 N). Instead, the fracture load of the aged composite restorations was comparable with that for zirconia (design 1) and cast metal (design 2) crowns. Fracture loads of direct composite restorations after artificial ageing might fulfil clinical requirements.

Caries prevalence in 12-year-old Cypriot children.

OBJECTIVE: To determine caries prevalence and caries experience in 12-year-old children living in the Republic of Cyprus and to evaluate whether different variables were associated with caries experience. METHODS: According to the WHO recommendation, schools were randomly selected by taking into account the distribution between rural and urban regions, so that 10% of Cypriot children attending the sixth grade could be examined. In the school year 2003/2004 the children were examined in schools by one person with the aid of artificial light but without taking radiographs or fibre-optic transillumination. DMFT, presence of fissure sealants and black stain were recorded. RESULTS: In total 951 children were examined. Caries prevalence was 32.6% (95% CI 29.62-35.6). The mean DMFT was 0.65 (sd 1.17) and the SiC was 1.95. Fissure sealants were found in 14.3% of the children. No association between frequency of tooth brushing, presence of fissure sealants or presence of black stain and caries experience was observed. Children living in rural areas had significantly higher mean DMFT values than children living in urban areas. CONCLUSION: A further caries decline may be attained by promoting a more extensive use of preventive measures like application of fluoride varnish or fissure sealants.