Comparison of Hyrax and bonded expansion appliances.

The majority of rapid maxillary expansion studies have reported the use of appliances with metal bands attached to the posterior teeth. Tooth extrusion, dental tipping, and an increase in the vertical dimension are often encountered, which may not coincide with treatment objectives. Bonded appliances using interocclusal acrylic may control the vertical dimension and expand the maxillary halves in a more bodily and symmetrical fashion. The purpose of this clinical trial was to determine, by radiographic analysis, the differences between a conventional banded expander (Hyrax) and a bonded acrylic expander. Fourteen patients who exhibited a need for expansion were enrolled in the study. The results suggest that the increase in the vertical dimension often seen with the more conventional Hyrax appliance may be minimized or negated with the bonded appliance. However, there appeared to be no significant difference between the amount of dental tipping or symmetrical expansion between the two appliances, as previously theorized.

Vertical extrusion using a removable orthodontic appliance.

Vertical extrusion is a useful adjunct to periodontal-restorative procedures, particularly in the anterior segment of the dentition in which esthetic appearance is a primary concern. In the case presented, a multidisciplinary approach was used to treat a tooth successfully with extensive subgingival destruction. Orthodontic and periodontic treatment, as part of an integrated treatment plan, resulted in preservation of esthetic appearance and establishment of sound tooth structure to allow for biologic width and restorative margins.

The response of human pulpal tissue after orthodontic force application.

Previous investigations have dealt with significant alterations in pulpal respiration associated with dental materials and methods. The purpose of this investigation was to note if significant alterations in pulpal respiration remained after the insult had been removed. A rest period of 1 week was chosen to evaluate the pulpal respiration response after application of an initial 72-hour orthodontic force. A radiorespirometric method was used to determine differences in experimental and control pulpal tissue respiration rates within individuals. These data showed that the mean respiration rates of experimental pulpal tissue compared with control pulpal tissue remained depressed approximately 33.2% after the 7-day rest period. However, it was found upon further investigation that there were really two groups present--one that had returned to normal respiration rates and one that did not within a 1-week rest period. Age and apical opening size correlated with the return of the respiration rates to normal during the 1-week rest period. Age was negatively correlated with respiration rate and apical opening size correlated with the return of the respiration rates to normal during the 1-week rest period. Age was negatively correlated with respiration rate and apical opening size was positively correlated with respiration rate.

Frictional changes in force values caused by saliva substitution.

The objective of this study was to determine the magnitude of frictional force changes between several sizes of stainless steel orthodontic wires (0.018 inch round, 0.020 inch round, and 0.018 X 0.025 inch rectangular) and an edgewise bracket (0.022 X 0.028 inch slot) when an artificial saliva medium was introduced. The wires were secured in the bracket slots with a 0.010 inch polyurethane ligatures. The force values in the saliva substitute medium were compared with those produced in a dry control and in glycerin. Clinically significant differences among the environmental conditions and among the wire sizes were found. The introduction of saliva substitute provides a significant reduction in force values.