Volume 22, No.2 - November 2006

Original Articles

Dental arch shape and size in Malay schoolchildren with Class II malocclusion
Saeed Banabilh, Zainul Rajion, Rani Samsudin and G.D. Singh

Myosin heavy chain isoform composition of human masseter muscle from subjects with different mandibular plane angles
Donna Lim, Felice Beitzel, Gordon Lynch and Michael G. Woods

An investigation of the forces used by clinicians to open spaces with coil springs
Gregor Steinbach, David Armstrong, Om P. Kharbanda, Peter Petocz and M. Ali Darendeliler

M/F ratios of four different closing loops: 3D analysis using the finite element method (FEM)
Mohammad Reza Safavi, Allahyar Geramy and Amir Kamyar Khezri

Assessment of growth activity in the mandibular condyles by single-photon emission computed tomography (SPECT)
Zahra Dalili Kajan, Safa Motevasseli, Navid Karimi Nasab, Hossein Ghanepour and Farzad Abbaspur

Use of miniscrews as temporary anchorage devices in orthodontic practice. I – Introduction
George Anka

The influence of ligation on frictional resistance to sliding during repeated displacement
Nathawut Sirisaowaluk, Olena Kravchuk and Christopher T.C. Ho

Static frictional resistances of polycrystalline ceramic brackets with metal slot inserts
Janahan Rajakulendran and Steven Jones

Root resorption after orthodontic treatment
David Armstrong, Om Kharbanda, Peter Petocz and M. Ali Darendeliler

Comparison of lip positions in ancient Buddhas with Japanese adults
Hideki Ioi, Shunsuke Nakata, Akihiko Nakasima and Amy L. Counts

Case report

Miniplates and screws in treatment of skeletal Class III malocclusion with missing posterior teeth. A case report
Charunee Rattanayatikul, Keith Godfrey, Jaruwarintr Chawengchettanon and Thepparit Vattraraphoudet

Abstracts

Dental arch shape and size in Malay schoolchildren with Class II malocclusion
Saeed M. Banabilh,* Zainul A. Rajion,* Rani Samsudin* and G. D. Singh†
School of Dental Sciences, Universiti Sains Malaysia, Kelantan, Malaysia* and BioModeling Solutions, USA†

Aim: To quantify and localise differences in Class I and Class II dental arches in Malay schoolchildren.
Methods: The subjects were 50 Malay schoolchildren (Mean age: 15 + 0.7 years) with either Class I (N = 25) or Class II (N = 25) malocclusions. Fourteen homologous landmarks on the upper and lower study models of the subjects were digitised using MorphoStudio software, and the Procrustes means were computed. The mean Class I and Class II configurations were subjected to t-tests and finite element analysis.
Results: Normalised upper arch Class I and Class II configurations were statistically different (p < 0.05), but the lower arches were not. However, normalised Class II linear parameters were statistically smaller in the upper arch and larger in the lower arch. The upper Class II dental arch was narrower by 15 per cent and asymmetric changes in size (11–20 per cent) were localised in the labial and buccal regions of the lower Class II arch.
Conclusions: Size and shape differences between Class I and Class II dental arches can be identified with finite element analysis.

(Aust Orthod J 2006; 22: 99–103)
Received for publication: January 2006
Accepted: July 2006

Myosin heavy chain isoform composition of human masseter muscle from subjects with different mandibular plane angles
Donna Lim,* Felice Beitzel,† Gordon Lynch† and Michael G. Woods*
School of Dental Science,* and Department of Physiology,† The University of Melbourne, Melbourne, Australia

Aim: To investigate the presence of myosin heavy chain isoforms in human masseter muscle and to describe any differences in orthognathic surgery patients with different mandibular plane angles.
Method: Biopsies were obtained from the anterior border of the superficial masseter muscle in 18 patients undergoing various orthognathic procedures. Myosin heavy chain isoforms were isolated and analysed by SDS-PAGE gel electrophoresis. Steiner’s mandibular plane angles were measured from pretreatment lateral cephalometric radiographs and used to classify the vertical dimension of each subject.
Results: Despite the fact that there was wide individual variation, there appeared to be no direct association between the presence of myosin heavy chain isoforms and specific vertical facial patterns. Type I myosin heavy chain isoform was the most common isoform found in all subjects. More Type IIA myosin heavy chain isoforms were observed in dolichofacial subjects. There were no differences between genders in myosin heavy chain expression.
Conclusion: A wide variation of myosin heavy chain isoforms exists in the masseter muscle of individuals with different mandibular plane angles. Further investigations involving larger sample sizes and the incorporation of bite-force measurements may help to clarify the relationship between mandibular muscle characteristics and the vertical facial dimension.

(Aust Orthod J 2006; 22: 105–114)
Received for publication: February 2006
Accepted: April 2006

An investigation of the forces used by clinicians to open spaces with coil springs
Gregor Steinbach,* David Armstrong,† Om P. Kharbanda,‡ Peter Petocz+ and M. Ali Darendeliler†
Hanover, Germany,* The University of Sydney, United Dental Hospital, Sydney, Australia,† All India Institute of Medical Sciences, New Delhi, India‡ and Macquarie University, Sydney, Australia+

Aims: To determine the forces applied by coil springs used to open spaces for blocked out lateral incisors, and to compare the actual forces used with clinicans’ concepts of an ‘ideal’ force.
Methods: Twelve postgraduate orthodontic students (7M, 5F) and 12 orthodontic tutors (9M, 3F) participated in this study. They were asked to state what they considered was an ideal orthodontic force, and then to cut appropriate lengths of stainless steel and nickel titanium open coil springs to open spaces for blocked out maxillary and mandibular permanent lateral incisors on a typodont set-up. The forces generated by the open coil springs were measured and compared to the stated ideal forces.
Results: The mean ideal force was 76.75 g (Range: 25–200 g). The mean applied force was 314 g (Range: 21–519 g). There were no significant differences in the forces used by the male and female postgraduates, but the male tutors used a significantly higher force than the male postgraduate students (p = 0.007) and the female tutors (p < 0.001). The female tutors used a significantly lower force than the female postgraduates (p = 0.024) and the male postgraduates (p = 0.003). Higher forces were produced by the stainless steel coil springs in both arches (Maxillary arch: p = 0.007; Mandibular arch: p < 0.005).
Conclusions: The clinicians could not agree on an ideal force to open spaces for blocked out lateral incisors. There were substantial differences between the forces applied by the coil springs and the forces considered by the clinicians to be ideal. There were large differences in the forces used by the different groups of orthodontists.

(Aust Orthod J 2006; 22: 115–120)
Received for publication: January 2006
Accepted: August 2006

M/F ratios of four different closing loops: 3D analysis using the finite element method (FEM)
Mohammad Reza Safavi,* Allahyar Geramy† and Amir Kamyar Khezri‡
Shahid Beheshti University of Medical Sciences,* Teheran University of Medical Sciences and Dental Research Centre, Teheran University of Medical Sciences† and Teheran,‡ Iran

Background: It has been claimed that the opus loop is capable of delivering a constant and optimum M/F ratio without the need for gable bends.
Objective: To compare the forces, moments and moment/force (M/F) ratios of the opus loop, L–loop, T–loop and vertical helical closing loop (VHC loop) in a segmented arch with the finite element method (FEM).
Methods: The FEM was used to compare 3D models of closing loops in rectangular (0.016 x 0.022 inch) stainless steel wire. The L–, T– and VHC loops were designed with and without preactivation bends. The opus loop had no preactivation bends. The T–Loops were 10 mm in height and 10 mm in length. The horizontal and vertical forces, the moments and the M/F ratios at the alpha and beta ends were recorded at 0, 0.1, 0.4, 0.7 and 1 mm intervals.
Results: The highest horizontal and vertical forces were produced by the L–loop (with and without preactivation bends) and in most cases the lowest forces were produced by the VHC loop. Loops with preactivation bends produced marked changes in the M/F ratio and loops without preactivation bends low, but relatively constant, M/F ratios over the full range of activation. Of the loops modelled without preactivation bends the opus and T-loop had the highest M/F ratios (7.20 – 7.67 mm at the anterior ends).
Conclusion: Stainless steel opus and T–loops without preactivation bends had constant M/F ratios, but both loops failed to deliver the optimum M/F ratio of 10:1.

(Aust Orthod J 2006; 22: 121–126)
Received for publication: August 2005
Accepted: August 2006

Assessment of growth activity in the mandibular condyles by single-photon emission computed
tomography (SPECT)
Zahra Dalili Kajan,* Safa Motevasseli,* Navid Karimi Nasab,* Hossein Ghanepour†
and Farzad Abbaspur†
Dental School, Guilan University of Medical Sciences,* Rasht,† Iran

Background: Unilateral condylar hyperplasia can lead to marked and disfiguring changes in the face and occlusion. A method of determining side-to-side differences in condylar activity is an important step in managing this condition.
Aims: To determine the growth activity in normal mandibular condyles and to devise an index of side-to-side differences in condylar activity in different individuals.
Methods: Thirty eight patients, ranging from 13 to 34 years, who were undergoing skeletal scintigraphy for a variety of conditions agreed to participate in this study. No subjects had clinical or radiographic signs of mandibular hyperplasia. After injection of 25 mci Tc99 the uptake by the right and left mandibular condyles was measured and the side-to-side differences used to calculate an index.
Results: The maximum side-to-side differences were 6.2 per cent (Right side versus Left side: 53.1 per cent and 46.9 per cent respectively) in the male patients and 5.7 per cent in the female patients (Right side versus Left side: 52.85 per cent and 47.15 per cent respectively).
Conclusions: The variation in growth activity in normal right and left mandibular condyles was less than 6.2 per cent.

(Aust Orthod J 2006; 22: 127–130)
Received for publication: December 2005
Accepted: June 2006

Use of miniscrews as temporary anchorage devices in orthodontic practice. I - Introduction
George Anka
Tama-shi, Tokyo, Japan

Aim: To describe the use of miniscrews as temporary anchorage devices to facilitate mesial, distal and vertical orthodontic tooth movement.
Method: The development of miniscrews and the direct and indirect application of forces from these devices are described. Case reports will be given in a second paper.

(Aust Orthod J 2006;22: 131–139)
Received for publication: June 2005
Accepted: August 2006

The influence of ligation on frictional resistance to sliding during repeated displacement
Nathawut Sirisaowaluk,* Olena Kravchuk† and Christopher T. C. Ho*
School of Dentistry,* and School of Land and Food Sciences,† The University of Queensland, Brisbane, Australia

Objective: To determine if the type of ligation influences the frictional resistance between stainless steel wire and brackets when the wire is subjected to repeated vertical displacements.
Methods: Eight different types of ligation were used to secure a length of stainless steel wire in three stainless steel twin brackets. The wire was subjected to repeated vertical displacements in a simulated extraction space. Eighty per cent of the minimum force required to overcome static friction (F-m) between the wire and brackets was applied to the wire for eight minutes and any sliding measured.
Results: Frictional resistance to sliding was least when stainless steel ligatures twisted in a figure 8 pattern until taut then untwisted one quarter turn were used, and greatest when elastomeric modules in a figure 8 pattern (EM8) were used. The F-m difference between fully engaged standard and Super Slick elastomeric modules was significantly different (p = 0.007). The frictional resistance to sliding fell when the wire was secured with either of these two methods and subjected to vertical displacement loads. There was no significant difference in the rate of wire movement between these modules.
Conclusion: Repeated vertical displacement reduced the frictional resistance to sliding for all methods of ligation except EM8. The stainless steel twist ligatures demonstrated the lowest frictional resistance to sliding.

(Aust Orthod J 2006; 22: 141–146)
Received for publication: July 2006
Accepted: August 2006

Static frictional resistances of polycrystalline ceramic brackets with metal slot inserts
Janahan Rajakulendran* and Steven Jones†
Doncaster, Victoria, Australia,* and Eastman Dental Institute for Oral Health Care Sciences, University College London, England†

Aims: To compare the static frictional resistances of polycrystalline ceramic brackets with a gold slot insert (Desire), a stainless steel slot insert (Clarity), a conventional polycrystalline ceramic bracket (Transcend 6000) and a stainless steel bracket (Ultratrimm).
Methods: Twenty five brackets of each type were tested by sliding against straight lengths of 0.019 x 0.025 inch rectangular stainless steel wire. During the tests the brackets and wire were lubricated with artificial saliva. Static frictional forces at three different binding angulations (0, 5 and 10 degrees) were measured for all brackets.
Results: Statistically significant increases in static frictional resistance were found as the bracket/wire angulation increased from 0 through 5 to 10 degrees for all bracket types. At angulations below the critical binding angle the Ultratrimm brackets produced the greatest friction and the Transcend 6000 brackets produced the least friction. As the angulation increased the Transcend 6000 brackets produced greater friction than the other brackets. At the highest angulation (10 degrees), the Ultratrimm brackets produced significantly less friction and the Transcend 6000 brackets produced significantly more friction than the other brackets. The Desire and Clarity brackets produced comparable results: there were no statistically significant differences between these two brackets for static friction at any of the angulations.
Conclusions: Polycrystalline ceramic brackets with either stainless steel or gold slot inserts produced similar static frictional resistances to sliding. At binding angulations, the brackets with inserts demonstrated consistently lower static frictional resistances than a conventional ceramic bracket.

(Aust Orthod J 2006; 22: 147–152)
Received for publication: June 2006
Accepted: September 2006

Root resorption after orthodontic treatment
David Armstrong,* Om P. Kharbanda,† Peter Petocz‡ and M. Ali Darendeliler*
The University of Sydney, United Dental Hospital, Sydney, Australia,* All India Institute of Medical Sciences, New Delhi, India† and
Macquarie University, Sydney, Australia‡

Background: Orthodontic treatment can result in root resorption.
Objective: To determine if apical root resorption is related to the type of appliance used and/or the direction and amount of tooth movement.
Methods: The pre- and post-treatment tooth lengths of the maxillary and mandibular first molars and incisors were measured on panoramic radiographs of 114 subjects. Associations between changes in the lengths of the incisors and positional changes in the upper and lower central incisors were determined for 45 subjects with pre- and post-treatment cephalometric radiographs.
Results: Taking into account the gender and OPT machine seven statistically significant differences were found between the appliance groups for the lengths of teeth 31 and 41. Within the groups four teeth decreased significantly in length when the pre-adjusted appliance was used (teeth 12, 11, 21, 26) and four teeth when the Speed appliance was used (teeth 26, 31, 41, 42). Only tooth 31 was shorter when the Tip-Edge appliance was used. Lower incisors were significantly shorter post-treatment if the apices were moved close to the lingual cortex.
Conclusions: When panoramic radiographs are used to assess treatment-induced changes in the lengths of the incisors, apical resorption is only one factor that should be considered. The images of lower incisors proclined during treatment may be foreshortened and/or the apices may lie outside the focal plane: both may result in ‘shorter’ teeth post-treatment. Because of the confounding factors panoramic radiographs may not be a reliable method of determining apical root resorption.

(Aust Orthod J 2006; 22: 153–160)
Received for publication: November 2005
Accepted: September 2006

Comparison of lip positions in ancient Buddhas with Japanese adults
Hideki Ioi,* Shunsuke Nakata,* Akihiko Nakasima* and Amy L. Counts†
Faculty of Dentistry, Kyushu University, Fukuoka, Japan,* Dental School of Orthodontics, Jacksonville University, Jacksonville, Florida, United States of America†

Objectives: To compare the lip positions found in two ancient Buddha statues with the lip positions in contemporary Japanese adults.
Methods: The facial profiles of Yakushi-ji temple Sho Kannon (male) and Chugu-ji temple Bodhisattva (female), generally considered to be two of the most beautiful Buddha statues in existence, were compared with the facial profiles of 30 Japanese dental students. Profiles of the statues were measured on photographs and profiles of the adults on cephalometric radiographs. The adults comprised 15 men between 22 and 26 years of age (Mean age: 23.8 ± 1.3 years) and 15 women between 22 to 25 years of age (Mean age: 22.9 ± 1.0 years).
Results: The Buddha statues had retrusive lips compared with the lip positions in contemporary Japanese adults.
Conclusion: Flat profiles may be favoured by Japanese adults who, typically, have protrusive lips.

(Aust Orthod J 161–165)
Received for publication: March 2006
Accepted: November 2006

Miniplates and screws in treatment of skeletal Class III malocclusion with missing posterior
teeth. A case report
Charunee Rattanayatikul,* Keith Godfrey,* Jaruwarintr Chawengchettanon,*
and Thepparit Vattraraphoudet†
Departments of Orthodontics,* and Oral Surgery,† Faculty of Dentistry, University of Khon Kaen, Thailand

Aim: To describe the use of miniplates for temporary skeletal anchorage to distalise the entire lower dentition.
Methods: A 40 year-old woman presented with a skeletal Class III malocclusion and multiple missing maxillary and mandibular teeth. The treatment plan was to distalise the mandibular dentition. Two miniplates and screws in the mandibular retromolar region were used as temporary skeletal anchorage for Class I elastics. The entire lower dentition was distalised into a Class I incisor relationship with the miniplate and screw anchorage.

(Aust Orthod J 2006; 22: 167–172)
Received for publication: January 2006
Accepted: March 2006