A simple mathematical study of anterior dental relations: Part III: incisor and canine overbite
The similarity between parents and offspring in facial soft tissue: a frontal-view study
An odontometric study of a Tibetan population
Lingual orthodontics: a review of its history
Case Report: Orthodontic treatment planning for inclusion of the third molar in the dental arches: Part II
Case Report: Two-phase treatment of an Angle Class II division 2 malocclusion
Two previous articles described horizontal interarch relations with a simple model developed. This paper required further development of the horizontal relations to allow vertical overlap to be studied. An analysis of orthodontic and dental-prosthetic models provided values to refine horizontal description then guide vertical calculations. Tooth thickness and angles of the maxillary teeth were related to horizontal overlap to produce an estimate of potential overbite. Principles were derived from the calculations and stated. Change can be predicted for overjet and overbite during and after orthodontic treatment. This series of articles expands the logical foundations by rationally considering a broad range of anterior occlusions. There are limitations in observing one or two features of anterior occlusion without comprehending the influence of other significant measurements. Measuring change in anterior overbite is inadequate without concurrently accounting for changes of other variables such as: spacing/enlarging/hypodontia; crowding; buccal relations and tooth thickness. A better understanding of anterior dental relations is possible from use of this model and the principles derived from it.
Key words: Occlusion, Overbite, Overjet, Tooth width, Tooth angles, Tooth thickness.
Accepted: September 1996
Similarities between parents and their offspring in facial soft tissue features were investigated. Fifty boys and fifty girls aged 9-10 years, excluding those with congenital anomalies, were selected. Frontal photographs of the family (father, mother and offspring) were taken and twenty-nine landmarks located on each enlarged tracing made from a photograph. Each landmark was digitised into (x, y) co-ordinate values from which the area and linear ratio dimensions were calculated and statistically evaluated. Results indicated that: (1) The nose was the feature that was most significantly correlated between parents and offspring. (2) The similarities between parents and offspring were closer for the relative positions of other features to the eyes than for individual features of the face. In general, the correlations between 'midparents' (the mean value of both parents) and offspring were higher than those between one parent and offspring. (3) The correlations between parents and offspring for size were higher than those for shape. (4) The similarities between mothers and offspring were closer than those between fathers and offspring. Furthermore: among four pairs of father/son, father/daughter, mother/son and mother/daughter, the mother/daughter pair had the highest correlation and the father/son had the lowest, which appears to be related to X-chromosome inheritance.
Key words: Similarity, Parents and offspring, Facial soft tissue.
Accepted: April 1997
Most of the indices of the norms of tooth dimensions established from model studies are those of a Western population. At present there are few norms for Oriental populations. This study was aimed at establishing more Oriental norms for various indices and the average tooth size of a particular Tibetan population, Tibetans being a distinct Mongolian type. The overall picture that emerges from all the established indices is that Tibetan teeth are broad and short. Mongoloids have a euryprosopic or wide face and a brachycephalic head. This study indicated that the teeth, dental arches and basal areas of the Tibetans in this group conform to this skeletal foundation.
Key words: Model analysis
Accepted: September 1996
When lingual orthodontics was first introduced about twenty years ago some called it the 'ultimate aesthetic appliance'. Patients and practitioners embraced this new treatment alternative with high expectations. Reports of disappointing results and high costs dampened much of the initial excitement and enthusiasm gradually waned. By the late 1980's, the number of practitioners using the technique had fallen sharply, leaving only a handful who still believed in its potential. Relatively little has been written on lingual orthodontics, almost nothing in recent years. This article takes an objective view of its present status.
Key words: Lingual appliances, Lingual orthodontics.
Accepted: April 1997
Marked lower anterior crowding (late crowding or post-adolescent crowding) often develops at about the time of third molar eruption.1,2,3 Many studies4-12 have implicated the presence of third molars as a cause of this crowding. Despite the fact that there is no clear evidence that this is the case,13-17 many orthodontists and their patients' referring dentists routinely remove third molars at the retention stage of treatment to prevent crowding later; Ricketts et al.18 even advocate enucleation of the third molar while the patient is very young to prevent future crowding. In the following report on two orthodontically-treated patients (the first three cases in this report were published in The Australian Orthodontic Journal, Volume 15, Number 1), the author emphasises the importance of careful consideration of the third molar in the treatment plan.
Received for publication: April 1996
This case was awarded the 1996 Begg Medallion by the Australian Begg Orthodontic Society.
This case report describes a two-phase approach to the treatment of an Angle Class II division 2 malocclusion in a growing boy. The first phase utilised a functional appliance (Clark Twin Blocks) during puberty and achieved a pleasing improvement in the facial profile. The second phase involved a fixed upper and lower Begg appliance without extractions, followed by retention. An unexpected complication was the failure of the lower left second molar to erupt; surgical removal of cystic elements surrounding this tooth, followed by traction and, later, mechanics to correct the buccal cross-bite, eventually corrected its position.
Received for publication: July 1997