Original Articles
Facio-lingual width of the alveolar base
Parpart Wonglamsam, Montien Manosudprasit, Keith Godfrey
Australian Orthodontic Journal 2003; 19: 1-11
In vitro surface corrosion of stainless steel and NiTi orthodontic appliances
Ji-Soo Shin, Keun-Taek Oh, Chung-Ju Hwang
Australian Orthodontic Journal 2003; 19:13-18
Some factors associated with open gingival embrasures following orthodontic treatment
Natsue Ko-Kimura, Masami Kimura-Hayashi, Masaru Yamaguchi, Tadataka Ikeda, Daijiro Meguro, Mika Kanekawa, Kazutaka Kasai
Australian Orthodontic Journal 2003; 19: 19-24
Cervical vertebral maturation as a predictor of the adolescent growth spurt
Keith Grave, Grant Townsend
Australian Orthodontic Journal 2003; 19: 25-32
Abstracts
Facio-lingual width of the alveolar base
Prapart Wonglamsam, Montien Manosudprasit, Keith Godfrey
Importance is attached to assessment of anterior facio-lingual maxillary and mandibular apical base widths in determining limits to incisor root movements. There is absence of similar assessment of facio-lingual base widths for premolars and molars.
The aims of this paper are two-fold: to determine the strength of associations between the facio-lingual widths of the anterior and buccal alveolar apical bases, and to determine if an association might exist between the posterior alveolar base width and specific lateral cephalometric measurements. Comparative measurements were made on 40 adult Thai skulls and their companion mandibles using lateral cephalometric radiographs, linear tomography, and direct measurements of the dento-alveolar and basal structures.
Wide variation was found in facio-lingual widths of the anterior and posterior alveolar bases in the maxillae and mandible. Significant inverse correlations were found between the alveolar base widths at the mandibular incisors and the FP-MP and PP-MP angles, and between maxillary incisor base widths and the gonial angle. Importantly, no cephalometric indicators were found to predict posterior alveolar base widths.
There is a need to continue to search for assessment indicators.
Received for publication: August 2002
Accepted: February 2003
Aust Orthod J 2003; 19: 1-11
In vitro surface corrosion of stainless steel and NiTi orthodontic appliances
Ji-Soo Shin, Keun-Taek Oh, Chung-Ju Hwang
Simulated fixed orthodontic appliances were constructed, immersed and incubated in artificial saliva for periods up to three months. Two types of stainless steel archwires and two types of NiTi wires were used. The surface corrosion of the archwires was determined macroscopically, with scanning electron microscopy, and with spectrophotometry. The deposits on the wires were identified with X-ray diffraction. Uniform corrosion was observed on stainless steel wires, and a slight colour change was detected on the NiTi wires beneath stainless steel ligatures. The corrosion product on the stainless steel wires increased with immersion time, and the surface oxide films were easily detached from the underlying matrix. Crevice corrosion was observed under deposits of oxide, and at the interface between bracket and band. Such corrosion may weaken a wire of weld leading to fracture. In contrast, the NiTi archwires did not corrode, and there was no significant difference in surface morphology. The stainless steel archwires showed a significant loss of reflectance after heat treatment and immersion in artificial saliva. The NiTI archwires had the same reflectance before and after the immersion test. NiTi archwires are significantly more stable and resistant to corrosion than stainless steel archwires.
Received for publication: July 2003
Accepted: February 2003
Aust Orthod J 2003; 19: 13-18
Some factors associated with open gingival embrasures following orthodontic treatment
Natsue Ko-Kimura, Masami Kimura-Hayash, Masaru Yamaguchi, Tadataka Ikeda, Daijiro Meguro, Mika Kanekawa, Kazutaka Kasai
Open gingival embrasures or "black triangles" can be an undesirable outcome of adult orthodontic treatment. The aims of the present study were to determine the prevalence of open gingival embrasures in a group of orthodontic patients, and to determine if open gingival embrasures were related to: age at the start of treatment, the severity of pretreatment crowding of the mandibular incisors, the duration of treatment or changes in alveolar bone height. The subjects were 80 orthodontic patients (33 males, 47 females) between 15 and 31 years of age. Open gingival embrasures were found in 43.7 per cent of all subjects, while in subjects over 20 years of age the prevalence was 66.7 per cent. In relation to the amount of crowding 42.8 per cent of the subjects with less than 4 mm crowding had open gingival embrasures, 41.2 per cent of those with between 4 and 8 mm crowding had open gingival embrasures, and 50 per cent of those with more than 8 mm crowding had open gingival embrasures. The groups were not significantly different. Approximately 42 per cent of the subjects in the shorter treatment group had open gingival embrasures, and 44.4 per cent of those whose treatment took longer than 3 years had open gingival embrasures. This difference was not statistically significant. Cephalometric measurements of mandibular alveolar bone height indicate that open gingival embrasures were more likely to be due to resorption of the alveolar crest rather than extrusion of the mandibular incisors. In conclusion, open gingival embrasures were more frequently found in patients over 20 years of age than in younger patients, and were associated with resorption of the alveolar crest.
Received for publication: April 2002
Accepted: January 2003
Aust Orthod J 2003; 18: 19-24
Cervical vertebral maturation as a predictor of the adolescent growth spurt
Keith Grave, Grant Townsend
The aim of this study was to investigate the application of an improved version of the Cervical Vertebral Maturation (CVM) method in a group of indigenous Australians and to relate the ossification events to the timing of peak growth in both stature and the mandible. Data were obtained from longitudinal records of 74 Australian Aboriginal children living at Yuemdumu Settlement in the Northern Territory of Australia. CVM stages were limited to particular growth periods: in a large percentage of subjects stage 1 occurred in the pre-peak period of growth, stages 2 and 3 in the peak period, and stages 4 and 5 in the post-peak period. Our findings were similar to those reported in other ethnic groups, suggesting that they can be applied more generally in orthodontic practice to assess a child's growth activity. In the majority of boys, CVM stage 2 would appear to be a good time to commence an orthopaedic phase of treatment, whereas in girls, results would support an earlier more cautious approach, sometime before stage 2 is reached. Peak growth occurs between stages 2 and 3 and timing is extremely important to maximize the effects of growth in the treatment process.
Received for publication: January 2003
Accepted: March 2003
Aust Orthod J 2003; 19: 25-32