Upper molar distalization with skeletally anchored TopJet appliance.

OBJECTIVE: To retrospectively investigate clinical outcomes with the TopJet appliance. MATERIALS AND METHODS: Measurements were taken on dental casts reflecting situations in 15 patients aged 10-48 years before and after orthodontic treatment with a TopJet appliance. Each measurement was taken with a digital caliper and repeated 2 weeks later. Recorded parameters included the amounts of distalization achieved, durations of active treatment to calculate rates of tooth movement, as well as rotational and transversal changes involved in the distalization of upper first molars. Student's t-test was used to compare mean values (α=0.05), explorative analysis to distinguish between unilateral and bilateral use of TopJet appliances, and Pearsons's correlation coefficient to determine intraobserver variability. RESULTS: Over a mean treatment duration of 5.9 months, the upper first molars were distalized by 4.0 ± 2.2 mm, including a mean tooth movement rate of 0.8 ± 0.6 mm per month. The rotational changes involved in the movements (-1.4 ± 6.7°) were not statistically significant. Transversal changes were 0.9 ± 1.2 mm at the level of the mesiobuccal cusps, 1.1 ± 1.1 mm at the central fossae, and 0.9 ± 0.9 mm at the distobuccal cusps. All measurements, other than those for rotation (r=0.7), were highly reproducible. Bilateral use of the appliance resulted in greater distalization than unilateral use, the mean difference being 1.4 mm. Bilateral use was more likely to involve inward rotation (+2.0°) on the mesial aspect of the first molars, whereas unilateral use resulted in mild outward rotation (-0.5°). CONCLUSION: Our results indicate that upper molars can be distalized effectively and efficiently with TopJet appliances. Any degrees of rotation and transversal changes that the first molars undergo during this process do not seem to play a major role.

Left/right asymmetries and open/closed differences of interdental forces in the mandible.

The aim of the present investigation was to study the variation in interdental forces between mandibular canines and lateral incisors of 19 volunteers (9 males and 10 females) aged 20-26 years for four configurations (mandible open/closed and left/right side). These forces were derived by pulling a stainless steel matrix strip between these teeth, six times per configuration, and registering the time variation with a high-resolution transducer. The repeated median smoothing algorithm was applied to find the maximum of each curve and a bootstrap method estimated the 95 per cent confidence intervals (CIs) for all 76 configurations. Seventy-six per cent of all paired force differences were found to be significant. Asymmetry phenomena were observed: the interdental forces differed significantly between the left and right sides and also between the open and closed position of the mandible. The interdental forces (4-21 N) showed a pattern modulated by volunteer-specific features: in 91 per cent of the configurations, the interdental forces were larger when the mouth was open. This observed pattern contributes to the instability observed in clinical practice, thus necessitating permanent fixed lower retainer wear.

Secular trends in the European male facial skull from the Migration Period to the present: a cephalometric study.

Secular trends in the facial skull over three Central European samples spanning more than 13 centuries were examined. Data were 43 conventional cephalometric landmark points for samples dating from 680 to 830 AD (29 male Avars), from the mid-19th century (49 adult Hapsburg Monarchy males), and from the 20th century (54 living Austrian young adult males). Analyses by standard methods of geometric morphometrics demonstrated shape differences by data and by size, with a strong interaction of these with sample, in that group mean differences were different for small and large individuals (allometry is different from period to period). The oldest sample, from the Migration Period, exhibited allometric features that may possibly be Turkic. There are implications for the orthodontist interested in growth trends or growth predictions in ethnically mixed patient samples.

Secular trends in the facial skull from the 19th century to the present, analyzed with geometric morphometrics.

INTRODUCTION: Over the last 100 years, Austrian facial form has changed for various reasons, including changes in growth pattern, changes in shape pattern, or a combination of these. In this study, we explored and contrasted these 2 explanations. METHODS: We compared cephalograms from 54 recruits in the present-day Austrian Federal Army to those from 49 dry skulls of soldiers from the Imperial Hapsburg army. Body height was measured or acquired from military records. Forty-three landmarks were located on each lateral cephalogram. Secular change and growth allometry were analyzed with standard Procrustes methods. RESULTS: Body height correlated only weakly with size of the facial skull in these samples, and secular change in facial size (4.5% over a century) was proportionately less than that in height. Growth allometry was nearly unchanged over the century, emphasizing the typical changes of vertical to horizontal proportions and bimaxillary prognathism. Secular changes over the century took the form of far more localized remodeling around the coronoid process and the anterior maxilla. The large-scale differences, in contrast, were opposite to those one would expect from the size change. CONCLUSIONS: The observed trends shed considerable light on secular changes in the range of dysmorphologies for clinical orthodontic correction. At the same time, the dissociation between within-century and between-century allometry is an important possibility that was hitherto typically observed only at far greater time scales than the 150 years spanned by these data.

Heat generated by residual adhesive removal after debonding of brackets.

AIM: To measure the rise in temperature during mechanical removal of residual adhesive after debonding of brackets in vitro. METHODS: Different carbide burs on a high-speed handpiece were tested. Acrylic on the buccal surfaces of recently extracted human maxillary incisors was removed using 3 types of carbide burs (6-, 12-, 40-fluted) with a varying number of windings relative to the long axis of the shaft. The temperature was measured using a thermocouple probe in the pulp chamber of the extracted teeth. RESULTS: The highest mean rise in temperature was measured using a 6-fluted bur (+9.4 degrees C, P < .001), followed by the 12-fluted bur (+6.5 degrees C, P <.001). The lowest rise in temperature (+1.2 degrees C, not significant) was seen with a 40-fluted bur. After 3 to 8 seconds of continuous grinding, the rise in temperature seems to slow down. CONCLUSION: The removal of residual adhesive after debonding is best performed with fine burs. If 6-fluted burs are used, a pause after 5 to 10 seconds of continuous grinding is recommended, especially in the mandibular anterior area.

A cephalometric comparison of skulls from different time periods--the Bronze Age, the 19th century and the present.

The aim of this study was to evaluate secular trends by means of orthodontic measurements on lateral cephalograms. We use roentgenograms from three populations: 22 Bronze Age skulls from a cemetery near Hainburg/Austria, 140 soldiers who served in the Hapsburg Imperial Army in the late 19th century, and 154 contemporary recruits of the Austrian Federal Army. Using conventional morphometric analysis, no statistically significant differences could be established. But applying geometric morphometrics to the 2D-coordinates of the pentagon composed of the landmarks Sella, Nasion, Articulare, Gonion and Menton, some biologically interpretable differences were detected, the size allometry between the 19th- and 20th-century populations being the only notable one. We conclude that landmarks should be digitized directly (and many more of them) and that conventional methods used in clinical orthodontics are inappropriate for addressing the scientific questions approached here.

Rectangular loops in inconsistent force systems: a laboratory investigation.

MATERIAL AND METHOD: [corrected] The force system delivered by the rectangular loop (R-loop) was the subject of this in-vitro investigation. The correction of a first-order irregularity was simulated in an inconsistent force system. Three types of R-loop made of 0.017" x 0.025" TMA wire but differing in length and insertion system were tested in a 3D strain gauge (Hottinger, Darmstadt, Germany). The buccal segment consisted of one molar and two bicuspids, with the first bicuspid as an active unit scheduled to be moved buccally into the dental arch. RESULTS: The first R-loop tested revealed too high a force magnitude to be recommended for clinical use. A loop connecting only two teeth and bypassing the second premolar delivered a favorable initial force of 85 cN with a drop of 20 cN per 1 mm deactivation. In order to achieve a translatory tooth movement, a buccal root torque must be bent in addition into the short horizontal leg of the R-loop. The use of a transpalatal arch is indispensable if adverse side effects are to be avoided.