Volume 18, No.2 - November 2002

Original Articles

Orthodontic treatment of palatally impacted maxillary canines
Richard J. Olive
Australian Orthodontic Journal 2002; 18: 64-70

Frictional resistance to sliding archwires with repeated displacement
C.F. Liew, P. Brockhurst, T.J. Freer
Australian Orthodontic Journal 2002; 18: 71-75

A comparison of splinted and banded Herbst appliances: treatment changes and complications
Urban Hägg, Edmond L.K. Tse, A. Bakr M. Rabie, W. Robinson
Australian Orthodontic Journal 2002; 18: 76-81

Maxillonasal dysplasia (Binder syndrome): a lateral cephalometric assessment
Barbara Carach, Michael Woods, Peter Scott
Australian Orthodontic Journal 2002; 18: 82-91

Distortions in panoramic radiographs
D.K.L. Yeo, T.J. Freer, P.J. Brockhurst
Australian Orthodontic Journal 2002; 18: 92-98

Abstracts

Orthodontic treatment of palatally impacted maxillary canines
Richard J. Olive

The aim of this study was to determine the feasibility of treating children with impacted maxillary canines by orthodontic treatment alone.
The subjects were 28 children (mean age: 13.5 years, range 11.4-16.1 years) with between them 32 palatally impacted canines. The overlying primary canines were extracted between 0 and 42 months before the start of appliance treatment to open space in the arches for the impacted teeth. No other surgical procedures were carried out prior to the start of appliance treatment. Appliance treatment was deferred for at leat six months if an impacted canine was the main reason for treatment, otherwise treatment was commenced according to the needs of the patient.
In 94% of the cases, the severity of impaction lessened following extraction of the overlying primary canines and orthodontic treatment. The deepest impactions tended to occur in the oldest children. The majority (75%) of the canines emerged following orthodontic treatment to create space for them in the arch; the remainder were surgically exposed. Appliance treatment tended to take longer in children with the deepest impactions.
It is concluded that fixed appliance treatment to create space for a palatally impacted canine is an effective management option for children with impacted maxillary canines.

Received for publication: October 2001
Accepted: April 2002
Aust Orthod J 2002; 18: 64-70

Frictional resistance to sliding archwires with repeated displacement
C.L. Liew, P. Brockhurst, T.J. Freer

Frictional resistance between a length of stainless steel archwire and a single bracket was calculated, and the effects of cyclical displacement forces on frictional resistance were tested. With the application of repeated displacement forces to be archwire, the force required to slide the wire through the bracket was substantially reduced. The percentage reduction in the force required to slide the wire was dependent on the size of the displacement force applied to the archwire. Frictional resistance in the mouth may not be satisfactorily reflected by steady mode laboratory models. The clinical implications for different types of orthodontic brackets remain unresolved.

Received for publication: April 2002
Accepted: July 2002
Aust Orthod J 2002; 18: 71-5

A comparison of splinted and banded Herbst appliances: treatment changes and complications
Urban Hägg, Edmond L.K. Tse, A. Bakr M. Rabie, W. Robinson

The aims of this study were to compare the frequency of clinical problems, such as fracture and dislodgement, and the dentofacial changes in 28 13-year-old Chinese children with Class II, division 1 malocclusions treated with either cast-metal splinted Herbst appliances or banded Herbst appliances.
The first fourteen children were treated with a maximum anchorage type of banded Herbst appliance for six months, and the remainder were treated with cast-silver splinted Herbst appliances for seven months. The dentofacial form and the treatment changes were assessed with the aid of pre- and post-treatment lateral cephalometric radiographs. The number of visits and the number of fractured and dislodged appliances were recorded.
Both appliances had similar effects on the dentofacial structures. There were no statistically significant dentofacial differences between the groups at the conclusion of treatment. During treatment relatively few banded appliances were dislodged and few splinted appliances fractured. However, a large number of banded appliances fractured, and a similar number of splinted Herbst appliances were dislodged. The latter required less clinical and laboratory time to service and/or replace.
It was concluded that splinted Herbst appliances are preferable to banded Herbst appliances because of the savings in clinical and laboratory time.

Received for publication: November 2001
Accepted: March 2002
Aust Orthod J 2002; 18: 76-81

Maxillonasal dysplasia (Binder syndrome): a lateral cephalometric assessment
Barbara Carach, Michael Woods, Peter Scott

Binder syndrome or maxillonasal dysplasia was first described by Binder in 1962, and is a disorder characterised by nasomaxillary hypoplasia. The records of 33 patients who had been diagnosed clinically with Binder syndrome at the Royal Children's Hospital of Melbourne were examined. Of these 33 patients, 14 were selected because they met the inclusion criteria: that they had not had prior surgical and/or orthodontic treatment, and that high-quality lateral cephalometric radiographs were available. The craniofacial morphology of these patients was determined on lateral cephalometric radiographs and compared with published age- and sex-matched norms. In agreement with published studies, the anteroposterior lengths of the anterior cranial base and maxillo were reduced, and the majority of patients had a Class III skeletal relationship. Although the lower incisors tended to be prominent, both overjet and overbite fell within the ranges for the normal population. Despite the fact that the orthodontic and surgical treatment for patients with Binder syndrome is normally carried out within specialised units, clinicians should be aware of the variety of ways in which this condition may present.

Received for publication: August 2001
Accepted: January 2002
Aust Orthod J 2002; 18: 82-91

Distortions in panoramic radiographs
D.K.L. Yeo, T.J. Freer, P.J. Brockhurst

This study was designed to investigate the factors affecting linear distortion in orthopantomography. A test model was constructed with metallic rods positioned to simulate maxillary teeth from the first permanent molar to the lateral incisor. In addition to examining the effects of varying the tilts of the test rods in a mesiodistal or bucco-palatal direction, spatial position changes (sagittal displacement, transverse displacement and horizontal rotation) of the test model were evaluated by determining the magnification changes in the width and length of the test rods. Results showed that significant errors occurred with all variations in magnification when test rods were included bucco-palatally (p < 0.001) at or exceeding 5 degrees relative to the true perpendicular, and for spatial positioning errors (p < 0.05) at or exceeding ± 5 degrees and ± 5 mm. Bucco-palatally inclined objects in the lateral incisor-canine region were particularly susceptible to large changes in horizontal magnification. Linear measurements and clinical assessments from panoramic radiographs should therefore be undertaken cautiously. To minimise errors in orthopantomography, it is important to position the patient in the focal trough precisely according to the manufacturer's specification.

Received for publication: June 2002
Accepted: September 2002
Aust Orthod J 2002; 18: 92-8