Treatment results in dental school orthodontic patients in 1983 and 1993

The effect of incremental changes in materials and techniques on orthodonti c treatment outcomes is difficult to evaluate objectively. Treatment result s for two groups of patients whose treatments were completed approximately 10 years apart were evaluated using the peer assessment raring (PAR) index and the index of orthodontic treatment need (IOTN) using the Wilcoxon match ed-pairs signed-rank test. Patients in the later group who had been treated by postgraduate students primarily (using fixed appliances) had significan tly lower IOTN and PAR scores at the end of treatment and showed a signific antly greater reduction in the PAR score than a similar group of patients i n the earlier group. There were no significant differences in treatment res ults between patients in the early and late groups who were treated with re movable appliances. Differences in treatment results were most likely the r esult of changes in materials a nd techniques that had occurred in the 10 i ntervening years.