Curriculum restructuring at a North American dental school: rationale for change.

The purpose of this article is to discuss how traditional dental school curricula are inconsistent with research in how learners learn. In the last ten years, there has been considerable discussion about the need for dental education reform, and innovative changes have occurred in the curricula of a number of U.S. dental schools. However, efforts in curriculum restructuring have been hindered by the lack of evidence that one specific curriculum design achieves outcomes superior to other designs. Moreover, there has been little discussion in the dental literature about how modern theories of learning can provide a sound rationale for change in dental education. Thus, it is important for those involved in curriculum reform to present the rationale for change based on the best available evidence. In this review, we summarize aspects of research on learning that seem applicable to dental education and outline ways in which curricula might be changed to become more consistent with the evidence.

Inhibition of orthodontically induced root resorption with echistatin, an RGD-containing peptide.

INTRODUCTION: Induced dental root resorption is a common side effect of orthodontic treatment. It is an unpredictable phenomenon, and its etiology is unknown. Odontoclasts responsible for the resorption of the dental tissues--ie, cementum and dentin--share many cytochemical and morphological characteristics with osteoclasts, which are responsible for bone resorption. The aim of this study was to explore cellular mechanisms that decrease induced root resorption in orthodontically treated teeth. METHODS: The effects of targeting the alphavbeta3 integrin receptor, expressed by odontoclasts, on induced root resorption surface areas and the number of root resorption lacunae were investigated by using an RGD-containing peptide, echistatin. The effect of echistatin on the number of clast cells in the periodontium was also examined. Tooth movement was achieved in 14 Sprague-Dawley rats by placing elastic bands between the right maxillary first and second molars for 24 hours. The animals were equally divided into 2 groups; the experimental animals received echistatin intravenously for 8 hours (0.8 microg/kg/min), and the controls received sterile water. The specimens obtained were processed for light microscopy. The surface area and the number of root resorption lacunae were measured histomorphometrically by using digital photomicrographs. Echistatin labeled with a fluorescent marker was used to confirm its presence in clast cells with fluorescent microscopy. Cytochemically, tartrate-resistant acid phosphatase was used to quantify mature and committed clast cells. Echistatin was localized in targeted cells in the periodontium. RESULTS: Echistatin significantly decreased root resorption surface areas (P < .01) and reduced the number of root resorption lacunae (P < .01). There was no statistically significant difference in clast cell numbers. CONCLUSIONS: Targeting alphavbeta3 integrin receptor expressed by odontoclasts can be effective in reducing root resorption during tooth movement. Further studies are needed to elucidate the mechanism of this inhibition.

Immunohistochemical localization of alphavbeta3 integrin receptor during experimental tooth movement.

During orthodontic treatment, multinucleated clast cells carry out the resorption of mineralized tissues. Adhesion of clast cells to the mineralized tissues is mediated by transmembrane cell-surface glycoproteins called integrins, specifically by the alphavbeta3 integrin, which plays an important role in the process of bone resorption. The role of the alphavbeta3 integrin in bone resorption leading to osteoporosis has been demonstrated, but its role in alveolar bone and root resorption during orthodontic tooth movement is unknown. This study examined the expression of the alphavbeta3 integrin during experimental tooth movement. Tooth movement was achieved in 16 male Sprague-Dawley rats (each weighing 120-200 g) with elastic bands between their maxillary first and second molars. The molar-bearing segments were dissected and processed for histologic and immunohistochemical examination. The expression of alphavbeta3 integrin was examined with 2 primary antibodies: a polyclonal anti-alphav integrin subunit antibody and a polyclonal anti-beta3 integrin subunit antibody. Negative controls were similarly processed but without incubation with primary antibodies. The alphavbeta3 integrin was expressed both by osteoclasts associated with alveolar bone resorption and by odontoclasts associated with root resorption during experimental tooth movement. Furthermore, the beta3 integrin subunit was expressed by the epithelial rests of Malassez in the periodontal ligament. Negative controls did not show immunolabeling. The alphavbeta3 integrin adhesion receptor is expressed during experimental tooth movement and might be involved in the process of mineralized tissue resorption and the functions of the epithelial rests of Malassez.

Use of bone morphogenetic protein-2 and dentin matrix protein-1 to enhance the osteointegration of the Onplant system.

Onplants are known to provide absolute anchorage for orthodontic tooth movement in humans if loaded after 3 to 4 months, and can be removed after use. The purpose of our study was to evaluate the speed and effectiveness of osteointegration of onplants treated with recombinant human bone morphogenetic protein-2 (rhBMP-2) and/or dentin matrix protein-1 (DMP-1) in rabbits. Fifty-four onplants were placed on the calvaria of 9 rabbits. Onplants were divided into four groups: rBMP-2, rDMP-1, BMP-2 +DMP-1 (B+D), and controls. The hydroxyapatite surface of each onplant was soaked in a solution of the assigned protein in each of the study groups or a phosphate buffer solution in the control group. Onplants were inserted into subperiosteal tunnels and allowed to heal for 6 weeks. After euthanizing the animals, bone blocks, each containing an onplant, were prepared for either histological examination or biomechanical characterization. Histological and histomorphometric results demonstrated significant bone formation at the bone-onplant interface in the BMP-2 and B+D groups when compared with DMP1 and the controls. Mechanically, onplants treated with BMP-2 withstood tensile forces between 3.4 and 5.0 kg. Onplants treated with BMP-2 and DMP1 (B+D) withstood an average of 3 kg of pulling forces. On the other hand, onplants in the DMP1 and control groups withstood forces ranging between 0 kg to 1.3 kg. These results indicate a potential of enhancing the osteointegration of onplants for early loading.