The New Zealand School Dental Service provides dental care for children 2 1/2-13 yr of age, without using routine diagnostic radiographs. This study investigated the pattern of dental X-ray exposure in groups of New Zealand children. One group consisted of 100 children who had all treatment before the age of 13 years with the School Dental Service. The other group consisted of 82 children who were treated in the University of Otago School of Dentistry paedodontic programme. Children in both groups turned 13 years of age between 1977 and 1982. From age 13 years these children were cared for by contracting dentists. Radiographic histories were recorded from School of Dentistry charts, and from the area Principal Dental Officer. Cumulative radiation doses were calculated. Surfaces restored at age 13 were noted from Department of Health records. Results show that by age 13 children enrolled in the School of Dentistry paedodontic programme received a mean cumulative skin dose of 23.03 mSv. Thyroid dose was 0.242 mSv. Children treated in the School Dental Service received a mean cumulative skin dose of 1.01 mSv and a thyroid dose of 0.006 mSv. Cumulative radiation dose for both groups was low. There was no significant difference in the mean number of restorations placed at age 13 years despite an extremely low level of diagnostic radiography in the School Dental Service group.

Adolescent↗

PubMed1983

Model for bacterial culture growth rate throughout the entire biokinetic temperature range.

The "square-root" relationship proposed by Ratkowsky et al. (J. Bacteriol. 149:1-5, 1982) for modeling the growth rate of bacteria below the optimum growth temperature was extended to cover the full biokinetic temperature range. Two of the four parameters of this new nonlinear regression model represent minimum and maximum temperature bounds, respectively, for the predicted growth of the culture. The new model is easy to fit and has other desirable statistical properties. For example, the least-squares estimators of the parameters of the model were almost unbiased and normally distributed. The model applied without exception to all bacterial cultures for which we were able to obtain data. Results for 30 strains are reported.

Acinetobacter↗

PubMed1983