This study analyses the expansive capacities of the new low friction binding system,compared with the conventional elastomeric binding system. Methods. 12 young people aged between 11 and 14 have been counted among the patients, who have skeletal malocclusion of Class II or III and with slight to moderate crowding of teeth,with no need of tooth extraction.The participants have been divided into two groups of 6: the first group has been treated with conventional elastomeric bindings,the second with low friction bindings,always using 0.14 NiTi arches and conventional stainless steel brackets.All the patients have been submitted to periodical check-ups Results. After 90 days the changes of the following parameters have been evaluated: intercanine distance, interpremolar and intermolar distance, dental arch length and perimeter. It has been found that the patients with low friction bindings show a greater increase of the interpremolar distance,while the patients with elastomeric bindings show a greater increase of the intermolar distance and of the dental arch length and perimeter;the latters have also showed a slightly greater increase of the intercanine distance. Discussion. As low friction dental braces do not alter the biological bone-periodontium-teeth system,they would allow a physiological movement of the teeth with the bone and a remodelling of the arch dimension.

Aim. The scope of this experimental study was to verify the validity of the ADPI proposed by Kim,confronting it with the ANB angle and Wits' index.Furthermore,it was intended to consider the correlation between these three parameters and the variations of the vertical scheletral rapports using as indicator Schudy's intermaxillary angle. Methods. We have analised the lateral-side x-rays from 50 subjects between the ages of 7 to 14.After having carried out the cephalometric tracing and,to evaluate the error,we have applied Dalberg's equation.The values from the various APDI measures were studied and elaborated to obtain the average and the standard deviation. Confronting the APDI values with the ANB angle we were able to evaluate the correlation matrix between ANB,Wits and APDI.The following phase was the analysis of the regression between the intermaxillary angle and the respective values of ANB,Wits and APDI. Results. These studies have bought us to recognise a high level of correlation between APDI and the other two parameters. Conclusions. The use of APDI should not substitute the traditional measures because it is reductive and risky,because of this one should resort to the practice of "2 out of 3" using the three forms of cephalometric tracing. Where two parameters are discordant it is always better to consider a third in order to arrive at a more correct diagnosis.