PubMed · 3865932
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A H Owen. 1985. Modified function regulator for vertical maxillary excess.. https://pubmed.ncbi.nlm.nih.gov/3865932/
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In laboratory experiments, progressive transversal jaw expansion with screw plates was simulated and the resulting increase in labial archwire force and deflection (autoactivation) was analysed. The results showed that progressive activation of a screw plate caused an initial increase in labial archwire force, which was subsequently followed by a minor reduction, and which stabilised after 90 seconds. Archwire force increases with the diameter of the wire, spring-hard wires developing higher forces than hard wires, and deflection decrease progressively with increasing size of the single activation step, as well as with increasing total activation. These results may have the following practical implications: on adjustment of the screw of the plate, the labial archwire is automatically activated to a reasonable degree for retroclination of the front teeth in screw plate treatment. This is particularly true when an 0.8 mm spring-hard wire is used. More constant archwire force is obtained by applying frequent small activations of the screw rather than a few large ones. To maintain the labial archwire force at a useful level, throughout treatment, fabrication of a new plate is recommended before the full range of screw adjustment is exhausted.
The theoretically favourable aspects of orthodontic space closure with segmented arch technique and the T-loop type A are clinically reproducible. In our study of eleven patients we found for the isolated canine retraction, as well as for the en masse retraction, controlled types of movement for the active units and maximum anchorage situations for the passive units produced by the torquing force. Because of these good anchorage conditions space closure could be done without headgear. The level of the anchorage segments was negligibly influenced but in the anterior segments a marked tilting was found in several cases. Besides other factors the intrusive force of the T-loops type A must be considered. As a rule the positioning of the T-loop between central and lateral incisor is to be recommended.
Occlusal contacts in maximum intercuspidation were recorded at the end of active orthodontic treatment and 3 months into the retention period. Hawley retainer, tooth positioner, and nontreated normal occlusion groups of 10 subjects were examined for change in the number and location of occlusal contacts. Soft silicone-base impression materials were used to make interocclusal registrations. The contacts were then transferred onto the study models, and standard photographs of each model were taken. To determine any locational changes, superimposition of the first registration photograph on the second one was done. Significant difference in the number of total contacts between the treated groups and the control sample was recorded at both time periods. Use of a tooth positioner as a retainer did not show any additional gain of contacts in the positioner group when compared with the Hawley retainer group. No significant change in the location of contacts occurred during the period of observation.