Volume 14, No.3 - October 1996


Original Articles

Guiding Occlusal development with functional appliances
Ib Leth Nielsen
Australian Orthodontic Journal
1996; 14(3):133-142

A mathematical study of anterior dental relations: Part II, incisor and canine overjet
Mark A. Cordato
Australian Orthodontic Journal
1996; 14(3):143-149

Application of a case-based expert system to Orthodontic diagnosis and treatment planning: A review of the literature
Roland M. S. Hammond, Terrence J. Freer
Australian Orthodontic Journal
1996; 14(3):150-153

Functional appliances: A mortgage on mandibular position
Lysle E. Johnston, Jr.
Australian Orthodontic Journal 1996; 14(3):154-157

Complications of orthognathic surgery
George Dimitroulis
Australian Orthodontic Journal
1996 14(3):158-161

Second permanent molar extraction and late lower arch crowding: A ten-year longitudinal study
Margaret E. Richardson
Australian Orthodontic Journal
1996; 14(3):163-167

A genetic aetiology for some common dental anomalies: A pilot twin study
Nick Kotsomitis, Michael P. Dunne, Terrence J. Freer
Australian Orthodontic Journal
1996; 14(3):172-177

Post-retention results of spring-loaded posterior bite-block therapy
Sevil Akkaya, Seda Haydar
Australian Orthodontic Journal
1996; 14(3):179-183

Case Report

A family case report: Disturbances in tooth form and eruption of the second premolar
Anne L. Symons, Aart A.R. Taverne
Australian Orthodontic Journal
1996; 14(3):168-171


Abstracts

Guiding occlusal development with functional appliances
Ib Leth Nielsen

Functional appliances have been used in Orthodontics since their introduction by Pierre Robin almost one hundred years ago, however, our understanding of how they bring about orthodontic correction is still limited. This article is a brief overview of their history, mode of action, advantages and disadvantages, and includes the results of a study of attempts to control and minimise their side-effects using a recent development in functional appliances: the ‘Teuscher Appliance’. This appliance combines a high-pull headgear with the activator, and is designed to reduce the often reported side-effects of functional appliances. The skeletal and dentoalveolar effects of treatment with the Teuscher Appliance on 40 consecutively-treated patients are reported and illustrated with four individual case reports.
The results showed that the skeletal effect on the maxilla was a retardation of the normal forward and downward growth in 80 per cent of the cases, and that mandibular growth in 80 per cent of cases was forward. In patients whose mandibular growth was primarily in a vertical direction, such growth could be ascribed mainly to posterior rotation of the maxilla and/or the fact that the acrylic covering the lower posterior teeth to correct a deep bite was removed, promoting the eruption of these teeth and increasing the anterior vertical development. The dentoalveolar changes were characterised by retroclination of the maxillary incisors in 90 per cent of the patients, and were due to insufficient torque control by the built-in torque springs which need further development. The mandibular incisors were well controlled by capping. The statistical analyses showed an inverse correlation between the initial incisor inclination and the change during treatment. This suggests that proclination of the lower incisors, as previously reported, is not a contra-indication to functional appliance treatment, provided the appliance is correctly designed. Overall, this study showed considerable individual response to treatment, and that the occlusal correction occurred through a combination of skeletal and dentoalveolar changes.

Accepted for publication : April 1995
Accepted : September 1995

Aust Orthod J 1995; 14(3)133-142

 

 

 

 

 

A mathematical study of anterior dental relations: Part II, Incisor and canine overjet
Mark A. Cordato

A mathematical model of anterior inter-arch relations was described in a previous article. This model is modified and manipulated and, using hypothetical dental measurements, results are generated and presented. The present work continues the two-dimensional examination of anterior dental relations in the first article, the emphasis remaining on incisor and canine overjet.
Other authors have started by observing ideal occlusions, then have worked backwards to gain ratios of preferred maxillary to mandibular teeth widths; this restricts their studies to Class I occlusions with complete anterior dentitions and similar anterior form of both arches. This paper has no premise of normal or initial ratios. Incorporation of multiple factors allows forming and testing of hypotheses of anterior dental relations. Many factors influence anterior dental relations in varying degrees. Some dental measurement changes examined here are: the sum of teeth widths in each arch; spacing; crowding; angle of the arc of each arch and the antero-posterior buccal relation.
Summary tables are presented to aid the prediction of the direction of inter-arch response to change in a dental measurement. Some inferences are discussed and are presented as a series of principles considered valid for this model. The principles may warrant testing with other arch form models.

Key words : Mathematics, arch form, overjet, tooth width, arc angle, occlusion, dental spacing, dental crowding, dental arch width, dental arch depth.

Received for publication : June 1995
Accepted : 1996

Aust Orthod J 1995; 14(3):143-149

 

 

 

 

 

Application of a case-based expert system to Orthodontic diagnosis and treatment planning: A review of the literature
Roland M.S. Hammond, Terrence J. Freer

Computer expert systems are being utilised increasingly in medical fields to assist diagnosis and treatment planning. Traditional rule-based expert systems have some limitations when applied to orthodontic diagnosis and treatment planning. These limitations may be avoided by using a case-based system which is a particular type of expert system that uses a stored data bank of previously-treated cases to provide the knowledge for solving new treatment problems. This article reviews the use of expert systems for orthodontic diagnosis and treatment planning, outlines the rationale, processes and advantages of case-based systems, and gives examples of the application of this technology in medical fields.

Key words : Diagnosis, treatment planning, computers, expert systems

Received for publication : November 1995
Accepted : July 1996

Aust Orthod J 1995; 14(3):150-153

 

 

 

 

 

Functional appliances: A mortgage on mandibular position
Lysle E. Johnston Jr.

It is a popular article of faith that clinicians and academics are polar opposites. In recent years, the supposed chasm separating town and gown has been the subject of aggrieved letters to the editor and embarrassing, intemperate comments at meetings. The seemingly eternal bone of contention is the standard of proof necessary to the conduct of a rational clinical practice.
In response to each successive ‘latest and best in orthodontic mechanism’, academicians routinely caution restraint and then, to compound the felony, badger the enthusiastic proponents for data. Unfortunately, those who object publicly to this ongoing criticism, ostensibly on behalf of busy clinicians and needy patients, all too often bring little to the dialogue other than varying degrees of proprietary interest and the strange notion that scientific truth is determined by a simple majority vote. As a teacher charged with preparing future generations of orthodontists, the writer sees this ongoing conflict as mocking all that education and the scientific method stand for; it speaks eloquently to the failure of our educational process.

Received for publication: July 1996
Accepted : July 1996

Aust Orthod J 1996; 14(3):154-157

 

 

 

 

 

Complications of orthognathic surgery
George Dimitroulis

Although orthognathic surgery has now become a routine part of oral and maxillofacial surgery practice, concern and apprehension about major jaw surgery continues to plague the minds of many orthodontists faced with the prospect of referring their patients for surgery. Like all surgery, complications also occur with orthognathic procedures, most of which can be prevented by thorough planning and careful surgery. In this article a brief overview of the potential complications associated with orthognathic surgery is presented for the benefit of orthodontists involved in the management of patients undergoing combined orthodontic-surgical treatment.

Key words : Orthognathic surgery, complications, risks, review of.

Received for publication : July 1995
Accepted : June 1996

Aust Orthod J 1996; 14(3):158-161

 

 

 

 

 

Second permanent molar extraction and late lower arch crowding: A ten-year longitudinal study
Margaret E. Richardson

The purpose of this investigation was to examine lower arch alignment in the long term following treatment by second molar extraction. Thirty subjects, treated by extraction of four second permanent molars at an average of 13.9 years, were examined five and ten years after extractions. None had any mechanical treatment in the lower arch. Twenty had some simple upper arch treatment, including, in five cases, extraction of first premolars. The changes in lower arch alignment were measured on study models. There was a small average decrease in lower arch crowding in the first five years following extraction, and little or no change in alignment in the next five years.

Key words: Second molar extraction, crowding, stability

Received for publication : February 1996
Accepted : June 1996

Aust Orthod J 1996; 14(3):163-167

 

 

 

 

 

A genetic aetiology for some common dental anomalies: A pilot twin study
Nick Kotsomitis, Michael P. Dunne, Terrence J. Freer

This pilot study investigated the aetiology of various dental anomalies. Twin-pair correlations were obtained for the total number of missing, ectopic, malformed and rotated permanent teeth which were scored from panoramic radiographs of 59 monozygotic (identical) and 42 dizygotic (non-identical) twin-pairs. All monozygotic (MZ) twin correlations were greater than the dizygotic (DZ) twin correlations, suggesting a significant hereditary aetiology. A familial history of such common dental anomalies could become a valuable asset in treatment planning.

Key words : Twins, genetic factors, dental anomalies

Received for publication : October 1995
Accepted : June 1996

Aust Orthod J 1996 14(3):172-178

 

 

 

 

 

Post-retention results of spring-loaded posterior bite-block therapy
Sevil Akkaya, Seda Haydar

In this study, ten patients who were treated with spring-loaded posterior bite blocks (SLPBB), were evaluated over a period of two years in order to test the effects of the appliance and the incidence of relapse. Successful treatment wit SLPBB was achieved in skeletal and dental open bite cases. However, the use of acrylic bite blocks for retention during the post-treatment growth period, did not prevent relapse.

Key words : Open bite; Bite Block Therapy; Relapse

Received for publication : November 1994
Accepted : June 1996

Aust Orthod J 1996; 14(3):179-183

 

 

 

 

 

A family case report: Disturbances in tooth form and eruption of the second premolar
Anne L. Symons, Aart A.R. Taverne

This report describes a family who demonstrated anomalies of tooth form and eruption of the lower second premolar. Observation of the second premolars remaining in the mother’s and father’s dentitions included ectopic eruption with impaction and substantial spacing between the first and second premolars. Four siblings were also examined - three boys aged 15, 14 and 12 years, and one girl aged 11 years. Anomalies of the second premolar recorded in the males and female include: congenital absence, ectopic eruption with impaction, delayed eruption and spacing. Associated anomalies included congenital absence of other permanent teeth and spacing. It appears that the defect in tooth form and eruption is of a genetic origin, affecting both males and females. The condition(s) did not appear to be associated with a syndrome, and the human papilloma virus lesions noted in all family members were not considered to be related to the dental defects. This family demonstrated two anomalies of the lower second premolar: congenital absence, and disturbance in tooth eruption. The question raised by this case report is whether these two anomalies are inherited as separate traits, or whether failure of tooth eruption is a variation in expression of the same genetic factor that results in oligodontia.

Received for publication : September 1995
Accepted : February 1996

Aust Orthod J 1996; 14(3):168-171