Current PhD Projects
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Retention of the lower arch with bonded lingual retainers Although the exact cause of relapse after orthodontic treatment is still unclear, the need for permanent retention of the mandibular arch is nowadays widely acknowledged by orthodontists. Compared to traditional removable appliances, the main advantage of bonded mandibular lingual retainers is their independence on patient cooperation. There are numerous forms of retainers; the most commonly used are the flexible spiral wire retainers, bonded to all lower anterior teeth, and the thick mandibular canine-and-canine retainer, bonded to both lower canines. Although the technical procedures and the advantages and disadvantages have been discussed in literature, only limited information is available concerning their long-term effectiveness and side-effects. Therefore research on the effectiveness and side-effects of the two most commonly used types of bonded mandibular retainers is beneficial for clinical orthodontics.
Collagen turnover in tooth movement and relapse
Sjoerd Henneman One of the main problems in orthodontics is relapse. During relapse the teeth tend to return to their pre-treatment position. Although the exact cause of relapse is still unclear, several possible causes have been proposed. Some authors suggest that periodontal fibers are stretched during tooth movement, and pull back the teeth after treatment. Other theories propose that relapse is caused by supra-alveolar elastic fibers or the transseptal fibers between the teeth. These theories all require that fibers are present within the periodontium that remain there for a long time and therefore have a long half-life. Literature data indicate a half-life of a few weeks for PDL fibers, and a few months for supra-alveolar fibers. The aim of this study is to determine the half-life of periodontal collagen fibers in different compartments of the periodontium. In addition, the effect of tooth movement on collagen turnover will be studied. These data will show whether the cause of relapse can be found in periodontal fibers with a long half-life.
Effects of analgesics on bone resorption during orthodontic therapy
Cendrawasih A Farmasyanti
Orthodontic tooth movement is based on tissue reactions in the dentofacial complex evoked by changes in mechanical conditions due to external forces. The present project focuses on the osteoclasts. These are the cells responsible for bone resorption and therefore a prerequisite for orthodontic tooth movement. In clinical practice these cells are recruited by activation and re-activation of the orthodontic appliances in the course of treatment. Such re-activations induce an acute inflammatory reaction within the periodontal ligament. One of the important features of this reaction is the so-called arachidonic-acid-cascade, a series of biochemical reactions leading, amongst others, to the production of prostaglandins. Prostaglandins play an important role in the induction of bone resorption and therefore stimulate tooth movement. On the other hand prostaglandins stimulate peripheral nerve endings which leads to pain. Orthodontic patients are therefore eager to use analgesics shortly after activation or re-activation of their appliance. However, most over-the-counter analgesics are of the NSAID-type. Their analgesic activity is based on the fact that they act as inhibitors of prostaglandin synthesis. However, as a side-effect, they counteract osteoclastic bone resorption and therefore slow down orthodontic tooth movement. Therefore research on alternative analgesics which do not interfere with osteoclast differentiation or their activity is beneficial for clinical orthodontics.
The effect of Emdogain® on periodontal wound healing and orthodontic tooth movement in rats Jeroen Roelofs
Periodontal diseases are bacterial infections with a high prevalence that cause the destruction of connective tissue, the loss of fibrous attachment of the teeth and the breakdown of alveolar bone and cementum. If untreated, these infections eventually lead to loss of teeth. Treatment of periodontitis focuses on the elimination of the bacterial infection and stabilization of the marginal lesion. This is done by periodontal surgery with possible application of Emdogain® on the exposed root surface. Emdogain® is an enamel matrix protein that has a possitive effect on healing of the periodontal structures after periodontal surgery. The exact working mechanism of Emdogain®, however, is still largely unknown. After periodontal surgery it is often necessary to bring the teeth in a favourable position by orthodontic therapy. The right time to start such an orthodontic therapy after periodontal surgery is still a big question mark. In our experiment we want to study whether effects of Emdogain® can be determined by histomorphometric analysis. In later experiments orthodontic tooth movement will be performed after treatment.
A biomechanical simulation model of the dento-alveolar complex A biomechanical simulation model of a tooth, its periodontal ligament, and the alveolar bone will be constructed. The model is validated with experimental observations from our Beagle dog experiments. This simulation model can be used to adequately predict the stress and strain distribution in the PDL. The work is performed in collaboration with the Eindhoven University of Technology, Biomedical Engineering & Materials Technology, Prof. Rik Huiskes. more info..
An unfavorable side effect of orthodontic tooth movement is hyalinization of the PDL. This phenomenon has been known for decades, but amazingly enough there are hardly any studies focusing specifically on hyalinization and all of them are studies on the initial stage of tooth movement. In this study in beagle dogs we look at the relationship between force level and hyalinization during the linear phase of orthodontic tooth movement.
Development of an evidence based clinical guideline for prevention of decalcifications during orthodontic treatment This project that is carried out in collaboration with the paedodontic department aims at the development of evidence based protocols for the prevention of decalcifications during fixed appliance therapy.more info.. |