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DISCIPLINE OF ORTHODONTICS - Graduate Profiles
The following are brief profiles of the current final year graduate orthodontic students in
the Discipline of Orthodontics, University of Otago. Each profile is followed by a summary
or abstract of the research study the student is carrying out as part of their course.
Matt Barker gained a Batchelor of Science from Canterbury in 1991, and a Batchelor of
Dental Surgery from Otago in 1994. Since graduating, he has worked in the Hutt Hospital,
Wellington; Sevenoaks, England: and has owned a dental practice in Christchurch, New
Zealand. He is presently in his final year of the Masters of Dental Surgery (Orthodontics),
and enjoys fine wine and line dancing.
The aim of his study is to investigate whether there are personality traits that predispose
to poor ratings of orthodontic treatment. Data has been obtained from the Dunedin
Multidisciplinary Health and Development Study, a longitudinal birth cohort of 1037
children born in Dunedin between 1972 and 1973.
Approximately one third of the Study members received orthodontic treatment by age 26,
of which 8% of those rated their result as poor. At age 18, each Study member completed
the Multidimensional Personality Questionnaire, a 300 item self report psychological test
which yields a comprehensive profile of human psychological differences among multiple
personality dimensions. Recipients of orthodontic treatment were grouped according to
their rating of orthodontic result, and statistical analysis was used to identify predictors
(personality traits) of orthodontic dissatisfaction.
Mark Kum graduated with his BDS from the University of Otago 1993. He is intending to
complete his MDS in Orthodontics this year. His research component during his study
was titled “Moment to Force Ratio Characteristics of a Modified NiTi Closing T-Loop”. His
appreciation goes towards Dr Andrew Quick and Prof James Hood as co-supervisors. He
would also like to thank the ERDG for a research grant, and the supply companies GAC,
Ormco, & 3M Unitek for their material contributions. The abstract is as follows:
Abstract
Closing loop mechanics have been described previously in the literature, and have been
constructed with various materials such as stainless steel, chromium-cobalt alloy, betatitanium, and most recently, nickel-titanium. A low modulus archwire such as nickeltitanium generates a more constant force over a wider range of activation. This
experimental study measured the forces and moments generated during activation and
deactivation up to 10mm of three different closing loops constructed from two different
materials. A custom built testing jig was used to measure non-preactivated wires with a
vertical U-Loop, symmetrical T-Loop, and an asymmetrical T-Loop (X-Loop) made from
Titanium Molybdenum Alloy (TMA) and Japanese nickel titanium (Neo Sentalloy). All
testing was performed at 35.6°C ± 0.5°C. The results showed that the forces produced by
the nickel titanium closing loops were significantly less than those made with TMA. The
moments generated were also less for the nickel-titanium closing loops. Overall, the
nickel-titanium closing loops produced a lower moment to force (M:F) ratio than those
made from TMA in the same loop design. However, the statistical model indicated that
Neo Sentalloy produced a greater moment. The experimentation also confirmed that loop
design influences the M:F ratio. The non-preactivated closing loops tested did not
produce high enough M:F ratios for the suggested translational tooth movements. Further
study is required on pre-activation bends in nickel-titanium closing loops as well as their
design to assess the feasibility of producing the required translational tooth movements.
Catherine Porter gained her BDS from the University of Otago, in 1986. She is married
to Richard, and they have two daughters, Libby and Charlotte, ages 7 and 5. Currently
she is a final year MDS (Orthodontics) student. At the completion of her MDS, they will be
returning to Auckland.
Her research project assessed the “Orthodontic treatment need in 17-year-old Dunedin
adolescents.”
Preliminary Report Although many indices of treatment need have been developed, any
meaningful index must include a component which is designed to measure aesthetics
and, by implication, the likely level of psychological disadvantage. Recently, the Dental
Aesthetic Index (DAI) and the Index of Orthodontic Treatment Need (IOTN) have been
developed. The IOTN has both a dental health component (DHC) and an aesthetic
component (AC). Most studies investigating age variations with these indices have been
cross-sectional; few longitudinal studies have been reported. In 1995, the orthodontic
treatment need in 294 randomly chosen, 10-year-old Dunedin school children, was
assessed using the DAI and the IOTN. 152 of these children were subsequently reexamined in 1998, aged 13.
Objectives To determine the need for orthodontic treatment in 17-year-old adolescents in
Dunedin, New Zealand, using the IOTN and the DAI, and compare these findings with
those obtained in the same individuals at ages 10 and 13.
Method 52 individuals (including those who had been treated by age 17) out of the 152
examined in 1998, were assessed using the DAI and the IOTN.
Results More participants at age 17, were assessed as “Needing” treatment with the DHC
(11.5%) of the IOTN, when compared with the participant-assessed (0.0%) and examinerassessed (1.9%) AC grades, and the DAI (7.7%). While the DHC was more consistent
overall in the percentage of participants requiring treatment, only one third of the
participants who “Needed” treatment at age 10, remained by age 17. The DAI however,
estimated three times as many participants “Needed” treatment at ages 10 and 13, when
compared with age 17. Only one quarter of the participants at age 10 remained in the
“Mandatory” category by age 17. The standard DAI at age 10 was, on average, a better
predictor of the DAI for those not treated by age 17, when compared with the modified
DAI.
Conclusions Attrition in longitudinal studies has the potential to result in sample bias. In
this study, the IOTN AC was found to be more stable over time than the DHC, whereas
the DAI, was found to be unreliable over time; with the fall in the DAI scores being
attributed to the over-sensitivity of the index to mixed-dentition traits. For both the IOTN
and the DAI, the size of the treatment-need categories masked the movement of
participants to different scores within the groups. The overall stability of the IOTN could
be attributed to the grouping of different occlusal traits in the same treatment-need
category and to the small number of treatment-need categories in each component.