Current research projects in the Discipline of Orthodontics
The high quality of research produced by the Discipline of Orthodontics at Otago is internationally regarded. Areas of research strength include: craniofacial biomechanics, mechanobiology of the periodontal ligament, randomized controlled trials for growth modification treatments, biomechanics of closing loops, sleep studies, obstructive apnea, and clinical oral physiology, including the function of the masticatory muscles and the temporomandibular joint (TMJ). Important emerging lines of research include craniofacial genetics, carried out in conjunction with Genetics Otago (A/Prof. T. Merriman), and craniofacial imaging in conjunction with the Department of Computer Sciences (A/Prof. B. McCane).
Research projects are generally carried out in collaboration with internal and external research groups with multiple supervisors, who provide differing areas of expertise. Examples of local collaboration include the Sir John Walsh Research Institute (Prof. J.Kieser, Dr. W.Duncan), Department of Psychology (Prof. R. Knight), Department of Medicine (Prof. T. Doyle), Department of Economics (A/Prof. P.Hansen), and the School of Physiotherapy (A/Prof. S. Milosavljevic).
International collaborations involve the Department of Orthodontics and Clinical Gnathology, University of Naples Federico II (Prof. R. Martina, A/Prof. A. Michelotti), the Department of Odontology, University of Copenhagen (A/Prof. M. Bakke), Laboratory for Biomechanics, University of Zurich (Emeritus Prof. S.Palla, Prof. L.M. Gallo), and the Institute of Surgical Technology and Biomechanics, University of Bern (PhD candidate M.E. De Oliveira).
Current research projects
Orthodontic students are involved in research projects under the supervision of senior researchers. Examples of current research projects performed by undergraduate or postgraduate students are given below.
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Identifying the genes that cause the long face.
Postgraduate research project by Joseph Antoun et al.
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Predicting factors of orthodontic pain.
Postgraduate research project by Victoria Beck et al.
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Under pressure: generic and individual intra-oral pressure profiles in liquid swallows.
Postgraduate research project by Guy Farland et al.
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Salivary pH variation over a 24-hour period.
Postgraduate research project by Jennifer Lee et al.
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The effect of lip displacement on intra-oral pressures.
Postgraduate research project by Hannah Jack et al.
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Activity pattern of neck and trunk muscles during orthodontic clinical work.
Postgraduate research project by Cameron McNee et al.
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Aspects of growth and development in New Zealand Polynesian children and adolescents.
Postgraduate research project by Joe Petelo et al.
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Impact of care-seeking behaviour on personality traits in orthodontic patients.
Postgraduate research project by Ali Ukra et al.
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Effect of examiner expectation on cephalometric measurements in skeletal class II malocclusions.
Undergraduate research projects by Mickey Zhou, John Jo et al.
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Exploring tooth movements with four dimensions.
Undergraduate research project by James Au, Austin Kang, Kevin Oh.
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Finite Element Model to evaluate the effect of masticatory forces on the human nasal septum.
Undergraduate research project by Nadeem Hamadani et al.
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Three-dimensional analysis of craniofacial growth in a Rabbit Model.
Undergraduate research project by Inah Kim et al.
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Grey analysis of the lateral pterygoid muscle in patients with temporomandibular disc displacement.
Undergraduate research project by Phil McClea, Karan Taneja, et al.
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Neck and shoulder muscle activity during work-related postural tasks.
Undergraduate research project by Doreen Ng et al.
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Chewing activity and sleep bruxism: an insight into the rhythmic contraction of the masticatory muscles in the natural environment.
Undergraduate research projects by Jessica Po et al.
Identifying the genes that cause the long face.
The orthodontic treatment of long face patients with open bite malocclusions can often be very challenging, with poor aesthetic and functional outcomes. The purpose of this multicenter study is to investigate the relationship between genes and long face patterns (increased facial height). We are interested in finding out which genes play a role in the development of long faces and how external or environmental agents may affect this process. The ability to identify genetic markers that predispose individuals to excessively long faces can provide us with a clinically important window of opportunity to predict facial growth at a very early age, and possibly, to provide personalized orthodontic treatments. Data for this project is being collected internationally by web site.
Postgraduate research project by Joe Antoun
Joe Antoun
antjo634@student.otago.ac.nz et al.
Predicting factors of orthodontic pain.
Up to 95% of orthodontic patients report pain at some stage during their treatment. This is an important, yet unpredictable factor, with some patients reporting mild discomfort, whereas others experience such pain that they choose to discontinue orthodontic treatment. This research aims to identify "high pain responders" and "low pain responders", who will be further screened for anxiety levels, dental fear, sensitivity of their teeth, and several pain thresholds. A cheek swab will also be collected to test for genetic differences that can affect dental pain sensitivity. It is expected that some of these factors can be used in the future to predict factors contributing to orthodontic pain.
Postgraduate research project by Victoria Beck
Victoria Beck
becvi843@student.otago.ac.nz et al.
Under pressure: generic and individual
intra-oral pressure profiles in liquid swallows.
A fundamental tenet of tongue function is that, during the oral phase of swallowing, the tongue transports the bolus from the front of the mouth to the entrance of the oropharynx by an orderly sequential contact of its dorsal surface against the palate. But what, exactly, is the pattern and extent of lingual pressure applied to the palate? Despite considerable progress in understanding how food consistency, jaw posture and movements, sex and age can significantly affect how humans swallow their food, the answer to this fundamental question remains unknown. This project is looking at the effect of bolus viscosity on tongue pressures generated during swallowing.
Postgraduate research project by Guy Farland
Guy Farland et al.
Salivary pH variation over a 24-hour period.
Dental erosion is a major and common dental problem caused by exposure to a variety of acids. Further, the consumption of acidic beverages and the incidence of gastro-oesophageal reflux are on the increase. To date, little is known about salivary acidity variation as related to dietary habits in the natural environment. This research aims to collect normative values for intra-oral pH using miniaturized in-vivo equipment and will provide an insight to understanding the aetiology of tooth erosion due to pH variation.
Postgraduate research project by Jennifer Lee
Jennifer Lee
leeja518@student.otago.ac.nz et al.
The effect of lip displacement on intra-oral pressures.
Orthodontic relapse is a major issue in orthodontics. The causes are still unknown, however it is thought to be related to an imbalance of forces between lip and tongue. Using custom-made intra-oral pressure-recording devices we aim to compare the immediate and delayed responses of lip musculature to stretch between participants who have retrusive and protrusive profiles.
Postgraduate research project by Hannah Jack
Hannah Jack
jacha668@student.otago.ac.nz et al.
Activity pattern of neck and trunk muscles during orthodontic clinical work
Previous epidemiological research indicates that dental vocational activities, including orthodontics, represent risk factors for work-related musculoskeletal disorders, especially of the neck and trunk. The aim of this research is to describe the contraction pattern of the sternocleidomastoid and trapezius muscles by means of portable electromyographic recorders (KFS-ZZM) during day-today clinical orthodontic work. The contraction episodes will be compared with those collected during a day of unrestricted non-vocational activities and under partially restrained conditions with video-surveillance.
Postgraduate research project by Cameron McNee
Cameron McNee
mcnca672@student.otago.ac.nz et al.
Aspects of growth and development in New Zealand Polynesian children and adolescents.
Knowledge of growth and development of children and adolescents is an important aspect that is relevant to the entire dental profession. With particular reference to Orthodontics, assessment of chronological age alone has been shown not to be an accurate predictor of ones physiological development. Growth velocity, dental development and skeletal maturation, in particular cervical vertebral maturation, are methods used that influence treatment decisions. Current literature supports variability in timing of maturation between different ethnic groups. This project is looking at New Zealand Polynesian children and adolescents dental development and skeletal maturation.
Postgraduate research project by Joe Petelo
Joe Petelo et al.
Effect of examiner expectation on cephalometric measurements in skeletal class II malocclusions.
After more than a century of craniofacial research, the overall findings on the effects of growth modification appliances in skeletal class II patients remain debatable. The uncertainty on the ability of functional treatment to modify mandibular growth is largely due to inconsistencies in results, which may be attributable to poor methodology of the studies rather than to treatment effectiveness. Major flaws of most studies include: the lack of randomization, the use of small sample size, and the lack of blinded measurements. We hypothesized that the outcome of cephalometric analysis is influenced by subconscious expectations of the treatment results. A repeated measures study design was used to determine the measurement biases occurring in orthodontists evaluating the cephalometric features of skeletal Class II patients.
Undergraduate research project by Mickey Zhou
Mickey Zhou, John JoJohn Jo et al.
Impact of care-seeking behaviour on personality traits in orthodontic patients.
The request of patients for orthodontic treatment is not always commensurate with the severity of malocclusion. In some cases the patient may over-emphasize minor orthodontic problems, thus indicating possible alterations in the self-perception of body image and smile. The aim of this research is to compare the personality traits and the occlusal features of care-seeking adolescents, who are the core of the orthodontic patient base, with those adolescents in the community with similar malocclusions who do not seek any treatment. Hence this research will shed light on the controversial association between malocclusion and temporomandibular disorders by identifying the possible confounding effects of somatization and propensity towards body dysmorphic disorders in clinic cases versus community cases.
Postgraduate research project by Ali Ukra
Ali Ukra
ukral644@student.otago.ac.nz et al.
Exploring tooth movements with four dimensions.
Orthodontic movements are generally described in two dimensions using a single center of rotation. However, in reality this is an over-simplification as during the application of forces, movements occur in 3D along an axis of rotation constantly changing over time. The finite helical axis (FHE) can be used to describe complex tooth movements allowing a deeper understanding of the biomechanics of orthodontic appliances. The aim of this project is to explore the relevance of the fourth dimension (time) in orthodontic biomechanics using advanced CAD software (Autodesk 3ds Max) under controlled clinical simulations.
Undergraduate research project by James AuJames Au, Austine Kang
Austine Kang, Kevin Oh
Kevin Oh et al.
Finite Element Model to evaluate the effect of masticatory forces on the human nasal septum.
Previous theories have emphasized the role of the nasal septum as a primary centre for craniofacial growth. Recent evidence suggests that the septum does not act as a vertical strut, and instead may rather act by absorbing loads generated during oral function. The resulting stress and strain pattern may also be implicated in the regulation of craniofacial growth. The Finite Element Modelling (FEM) technique makes use of computers to solve large numbers of equations, which simulate the physical properties of the structure being analysed. The non-invasive nature of FEM allows the modelling of forces, stress, and strains in a manner that is suitable for evaluating the effect of masticatory forces on an appropriate human model. To date little is known about how the nasal septal cartilage responds to everyday forces, such as those experienced during mastication, clenching, swallowing and rest. It is the aim of this study to describe these stress and strain patterns through the use of a Finite Element Model. It is hypothesised that a significant extent of these functional forces will be transmitted to the nasal septum.
Undergraduate research project by Nadeem Hamadani
Nadeem Hamadani et al.
Three-dimensional analysis of craniofacial growth in a Rabbit Model.
Predicting and modifying mandibular growth is an important aspect of orthodontics. Our current knowledge of the extent to which the mandible changes and rotates during growth is derived from classical longitudinal radiographic studies with metallic markers. While the information obtained from these landmark studies is substantial, there are limitations associated with a two-dimensional image. Cone-beam computed tomography (CBCT) is becoming widely available and is a diagnostic tool in dentistry. It is hypothesized that the implant method of analysis combined with CBCT three-dimensional (3D) imaging will provide more information with respect to mandibular growth over time, than previous studies that used conventional radiographs. The purpose of our study is to describe mandibular remodelling in a growing rabbit model using metallic bone markers and three-dimensional colour growth maps. This study was undertaken to determine the feasibility of the proposed method, in order to plan future treatment intervention studies.
Undergraduate research project by Inah Kim
Inah Kim et al.
Grey analysis of the lateral pterygoid muscle in patients with temporomandibular disc displacement.
Magnetic Resonance Imaging (MRI) is an ideal tool for soft tissue imaging including the temporomandibular joint (TMJ) disc and masticatory muscles. The purpose of our research was to compare the grey scales of the upper and lower heads of the lateral pterygoid muscles between TMJs with internal disc derangement and healthy joints. Three dimensional (3D) reconstructions of the lateral pterygoid muscles (LPM) were obtained by manual and semi-automatic segmentation techniques, and rendered in 3D. Regions of interest for the upper and lower lateral pterygoid muscles were defined and the grey histograms were calculated. The mean and median values of the resulting scales were used as outcome measures. Significant changes of the histograms were found between the affected and unaffected joints, thus indicating the possible occurrence of disuse atrophy of LPM as well as fatty infiltration. The grey analysis may have interesting applications in craniofacial imaging that need to be fully explored in future studies.
Undergraduate research project by Phil McCleaPhil McClea, Karan Taneja
Karan Taneja et al.
Neck and shoulder muscle activity during work-related postural tasks.
The aim of this study is to describe the pattern of neck and shoulder muscle contractions during a series of work-related postural tasks and secondly, to explore whether the contraction levels differed between sexes. Electromyographic (EMG) activity was recorded using specifically designed software unilaterally from the sternocleidomastoid and upper trapezius muscle in 17 participants, who were instructed to perform 44 different postural tasks. EMG amplitude was measured by the root mean square values of the raw signals and normalized to peak maximum contractile values for each muscle (EMG%MVC). Muscle co-activation was assessed by a co-activity index of both investigated muscles. During most tasks the two muscles contracted lightly to moderately and were mildly co-active. Tasks such as head leaning and shoulder shrugging, which are commonly performed during dental work, activated both muscles considerably. The sternocleidomastoid muscle produced substantial activity during tasks involving head movements whilst the trapezius muscle yielded greater muscle activity during arm tasks. Muscle activity did not differ significantly between male and female participants.
Undergraduate research project by Doreen Ng
Doreen Ng et al.
Chewing activity and sleep bruxism: an insight into the rhythmic contraction of the masticatory muscles in the natural environment.
Chewing is the result of a complex interaction between neural pathways, a central pattern generator, which generates an intrinsic rhythm, and modulation from peripheral feedback. Sleep bruxism is highly prevalent in the general population and its consequences include tooth wear, orofacial pain, and destruction of dental work. The aetiology of sleep bruxism is still unknown but it is nowadays accepted to have a central origin unrelated to dental occlusion. Given the available information in the existing literature, the question arises as to whether there could be a relationship between chewing and sleep bruxism activities. However, little information currently exists regarding the features and variability of human chewing activity and the features and mechanism of sleep bruxism as they occur in the natural environment, resulting in an inability to compare the two. In recent years, portable EMG recorders have been developed and used to gather data on rhythmic masticatory muscle activity, and an algorithm for the automated detection of this activity from EMG signals was developed and validated. These recent developments allow for accurate time-frequency analysis of rhythmic episodes as they occur in the natural environment thus enabling us to investigate the question posed above. The objectives of two research projects were firstly to investigate the variability of the human chewing pace, both between and within individuals as assessed in their natural environment, and secondly to then compare human rhythmic masticatory muscle activity in the natural environment, including sleep bruxism and chewing, in a separate cohort.
Undergraduate research project by Jessica Po
Jessica Po et al.
