Abstracts

# THE DRUM SPRING (DS) RETRACTOR: A CONSTANT AND CONTINUOUS FORCE FOR CANINE RETRACTION

M. Ali Darendeliler, Haluk Darendeliler and Oktay Üner

Although much research has been undertaken on the rate of tooth movement, with different hypotheses having been put forward, the concepts of threshold, light, heavy and optimal forces are not still clear.

It has been stressed that an ideal orthodontic spring should have the ability to release a constant force throughout the entire range of its activation, but using traditional techniques applied initial force will decrease, depending on its deactivation due to the tooth movement and the physical properties of the force delivering system. The purpose of this study was to test the clinical use of a new and original spring, the drum spring (DS) retractor (developed in 1992), which applies a constant and continuous force without the need for reactivation, and to compare the effect of a constant and continuous force versus a continuous but diminishing force produced by a traditional pull coil (PC) retractor system on the rate of upper canine retraction.

The clinical sample consisted of 15 patients with upper first premolar extractions. For each patient,

the upper right canine was retracted by using a DS retractor applying a constant and continuous force of 50g; the upper left canine was fitted with a conventional PC applying an initial force of 50g, diminishing proportionally with the distal movement of the canine. In addition, each group was divided according to the age of each patient: eight patients (three males, five females) between 11.8 and 14.4 years of age (mean 13 ± 1.2 years) represented the adolescent group, and seven patients (three males, four females) between 18.8 and 21.6 years of age (mean 18.2 ± 1.9 years) representing the adult group. The experimental period started one week after the extraction of the first premolars. During this period no archwire was used, to avoid friction and force level changes, and the both springs were attached to a 6 mm hook fixed on the canine bracket to reduce tipping. The PC retractor was reactivated every three weeks whearas the DS retractor was left untouched over the entire experimental period. The study was continued until one of the two canines was completely retracted. The DS retractor was successful for space closure without any reactiviation, and the continuous and constant force provided a more rapid canine movement than the continuous but diminishing force. Canine retraction occurred faster in adolescents than in adults. An entire field of clinical and research applications may be influenced by this new type of spring.

European Journal of Orthodontics
19 (1997); 115-30
## FINANCIAL INDEPENDENCE WITH OR WITHOUT MANAGEMENT SERVICE

Todd S. Callender and R. Sam Callender

For the past several years, the most hotly debated issued in orthodontics has been the development of the management service organisations. Most MSO's involve the same basic concept, painted in different terms to appeal to different types of doctors. Each provides a sizeable affiliation price and other incentives, in exchange for a 20- or 40- year contract that hires the MSO to manage the business affairs of the practice. The MSO receives 15-20% of the practice's gross income (or 30-40% of the net) as an annual fee. Since its management services are accomplished mainly with the doctor's existing staff and income, the MSO recovers its affiliation fee over the period of the agreement.

*Journal of Clinical Orthodontics*

1997; July: 442

## LONG-TERM EFFECTS OF CLASS II CORRECTION IN HERBST AND BASS THERAPY

Jane Ömblus, Olle Malmgren, Hans Pancherz, Urban Hägg and Ken Hansen

This study compared the initial and long-term skeletal and dental effects of Herbst and Bass appliance therapy for correction of Class II malocclusion. The sample comprised 18 pairs of boys matched for growth period at the time of therapy, with similar pretreatment sagittal and vertical jaw base relationships. One boy in each pair was treated with the Herbst and the other with the Bass appliance. At follow-up, 15 boys of the Herbst group and 17 of the Bass group were available. Lateral cephalograms in centric occlusion taken before treatment, after 6 months of treatment and at the end of growth were analysed. After 6 months of treatment the Bass appliance seemed to have a greater effect on mandibular jaw base position. The correction of overjet and sagittal molar relationship was more complete in the Herbst patients due to dental changes. At follow-up varying effects both between and within pairs were observed. Overall, the skeletal and dental changes from start of treatment to end of growth were of the same magnitude. A restraining effect on the position of the maxilla was observed in both groups, somewhat more pronounced in the Bass sample. Both treatment methods are most useful in correction of severe Class II malocclusions. It was, however, difficult to find possible differences in treatment effects between the two methods due to great individual variations of growth.

*European Journal of Orthodontics*

19 (1997); 185-93

## EVALUATION OF THE SHEAR BOND STRENGTH OF DIFFERENT CERAMIC BRACKET BASE DESIGNS

Marc E. Olsen, Samir E. Bishara and Jane R. Jakobsen

The purpose of this study was to compare the Ceramaflex bracket with a traditional ceramic orthodontic bracket with regard to shear bond strength and bond failure location. Forty newly extracted human premolars were randomly divided into two groups. Twenty Ceramaflex brackets (TP Orthodontics Inc. LaPorte, Ind) and 20 Transcend 6000 brackets (Unitek Corp, Monrovia, Calif) were bonded to the teeth using the same bonding system (Right On, TP Orthodontics Inc, LaPorte, Ind). A Zwick Universal Test machine (Zwick Gm bH & Co, Ulm, Germany) was used to determine the shear bond strength for each bracket. After debonding, the teeth and brackets were examined under 10x magnification. After debonding, the amount of resin material adhering to the enamel surface was assessed according to the Adhesive Remnant Index (ARI). The results of this study suggest that Ceramaflex brackets have a significantly lower bond strength than traditional ceramic brackets. On the other hand, the bond failure location of the Ceramaflex bracket was consistently more favorable, i.e., occurring at the ceramic bracket-polycarbonate base.

*The Angle Orthodontist*

1997; 67 (3): 179-82.

## NICKEL-TITANIUM COIL SPRINGS AND REPELLING MAGNETS: A COMPARISON OF TWO DIFFERENT INTRA-ORAL MOLAR DISTALIZATION TECHNIQUES

N. Erverdi, D. Koyutürk and N. Küçükeles

The aim of this study was to compare two intra-oral molar distillation procedures, involving 15 cases with Class II molar relationships. Magnetic devices were applied to the upper right first molars in each case, while nickel-titanium coil springs were used against the upper left first molars, for a period of three months. Measurements were made from lateral cephalograms and from photocopies of models taken before and after the distalization procedure. Although upper molar distalization was achieved with ease in both techniques, nickel-titanium coil springs were found to be the more effective in terms of movement achieved.

*British Journal of Orthodontics*

1997; 24: 47-53