Current practice in endodontics: 3. Access is success, and rubber dam is easy

The prime aim of this series of articles is to improve the quality of endodontic treatment in general dental practice by considering what is currently being taught in dental schools. This, the third article, offers guidance and hints to ease the use of rubber dam, which should be mandatory for root canal therapy. It also considers the shape, position and extent of access cavities. The access cavity can make all the difference in success or failure of endodontic treatment.     

Expression of human beta-defensin -1, -2, and -3 in non-inflamed pseudocyst, mucoceles

Objectives and design: The expressions of human beta defensin‐1 (HBD‐1), ‐2 (HBD‐2) and ‐3 (HBD‐3) in non‐inflamed pseudocysts such as mucoceles were investigated immunohistochemically in this study. Materials and methods: Mucocele specimens were obtained from 21 patients. The expression of HBDs was studied immunohistochemically by using antibodies directed against HBD‐1, ‐2, and ‐3. Statistical analyses were carried out on serial sections stained with antibodies. Results: Cells expressing HBDs were found in mucoceles. The expression of HBD‐2 was observed in floating cells in all the specimens, whereas HBD‐1 and HBD‐3‐expressing cells were detected in 93% and 73% of the mucoceles, respectively. The HBD‐2 signal was the most intense and the HBD‐3 signal intensity was weaker than that of HBD‐1. HBDs were expressed in neutrophils and in other floating cells. Interestingly, the signal intensity and the population of positive cells located close to the centers of cysts were higher than those located in the peripheral areas of cysts. Conclusion: The expression of HBDs was found even in non‐inflamed pseudocysts such as mucoceles. These results suggest that an unknown mechanism not involved in biophylaxis for the expression of HBDs may exist.     

TGF-β1 is essential for the homeostasis of the dentin-pulp complex

Among the complex network of cytokines that influence odontoblast function during development and repair, TGF-β1 is unique in its dual abilities to function as a potent immunosuppressant and as an inducer of extracellular matrix production. These properties underscore the importance of this molecule in maintaining the homeostasis of the dentin-pulp complex after injury. The purpose of this paper is to describe new findings of our phenotypic analysis of dentition in mice in which the TGF-β1 gene has been disrupted. The major phenotype of TGF-β1 (?/?) offspring is one of diffuse immune system activation with progressive inflammation, wasting and death. Our studies of adult TGF-β1 (?/?) dentition show widespread pulpal and periapical inflammation and necroses. In addition, the coronal surfaces of occluding molars show marked attrition. To determine whether the phenotypic changes in TGF-β1 (?/?) dentition are directly linked to the loss of TGF-β1 rather than the inflammatory process itself, we studied adult dentition in TGF-β1 (?/?) mice backcrossed into immunodeficient backgrounds. Results of our histopathologic and radiographic analyses show that teeth of TGF-β1 (?/?) immunodeficient mice retain vitality in pulpal and periapical regions but show excessive wear of occlusal surfaces.     

Dental education in Queensland I: the 1-3-1 model.

Dental education worldwide is under great pressure. This pressure is being driven not only by changing patterns of oral disease but also by economic factors both inside and outside universities. Technological advances and changing educational philosophies across the board also impact significantly on what we do and how we do it. This article outlines how the School of Dentistry at The University of Queensland is responding to these pressures within the context of local political, educational and economic realities. The so-called 1-3-1 model that has been adopted involves one year of basic science, three years of applied dental science and one year of extramural clinical practice. This model represents a partnership with the Queensland Department of Health and will: Involve dental education and the Dental School in the provision of health care to the community. Place the Dental School in a position to influence the delivery and quality of oral health care in the population and to assume some of the responsibility for it. Provide a wide range of clinical and community experiences for students prior to graduation. Allow the adoption of modern teaching methods such as Problem Based Learning (PBL) in Years II-IV with all the additional benefits e.g. communication skills. Provide an extended clinical period for the acquisition and development of clinical and technical skills prior to graduation. Be cost-effective both to the university and the health service. Allow for outside input without compromising the knowledge and research base. It is recognised that while the 1-3-1 model may meet the demands of a large, decentralised state such as Queensland, it may not be suitable for all institutions. In this context diversity in approach is one of the strengths of dental education, nationally and internationally.     

Timp-1, -2 and -3 show coexpression with gelatinases A and B during mouse tooth morphogenesis

Matrix metalloproteinases (MMPs) have been implicated in tissue remodelling and in regulation of cell-matrix interactions during organ development. The activity of MMPs is regulated by members of the TIMP (tissue inhibitors of metalloproteinase) family. We analyzed by in situ hybridization the expression of gelatinase A (MMP-2) and gelatinase B (MMP-9) as well as Timp-1, -2 and -3 during different stages of mouse tooth development. Gene expression was generally found in mesenchymal tissues except for Timp-3, which also was found in dental epithelial cells. During early tooth development, gelatinase A and Timp-2 were widely expressed in the branchial arch, while gelatinase B and Timp-1 and Timp-3 expression showed clear association with epithelial morphogenesis and was restricted to the mesenchyme at the tip of the growing tooth bud. Gelatinase A and Timp-1 showed transient expression in secretory odontoblasts at the time of basement membrane degradation, while Timp-2 expression continued throughout the dental papilla. At the time of tooth eruption, Timp-3 was expressed in most dental epithelial cells except secretory ameloblasts, and gelatinase B was intensely expressed in osteoclasts in the jaw bone. The exact co-localization of gelatinase A and Timp-1 in secretory odontoblasts, and the correlation between gelatinase B and Timp-3 during bone resorption may indicate interaction of the proteins during degradation of the basement membrane and in the control of ECM turnover in connection with tooth eruption.     

Irreversible inflammation is associated with decreased levels of the alpha1-, beta1-, and alpha2-subunits of sGC in human odontoblasts

The nitric oxide (NO) receptor enzyme soluble guanylate cyclase (sGC) contains one prosthetic heme group as an αβ heterodimer, and two heterodimer isoforms (α(1)β(1), α(2)β(1)) were characterized to have enzyme activity. To test the irreversible inflammation-dependent regulation of sGC in odontoblasts, we incubated decalcified frozen sections of healthy and inflamed human third molars with antibodies against β-actin, nitrotyrosine, inducible nitric oxide synthase (iNOS), α(1)-, β(1)-, and α(2)-subunits of sGC and analyzed them at protein levels by quantitative immunohistochemistry. The irreversible inflammation induced an increase in the signal intensities for nitrotyrosine and iNOS and a decrease for the α(1)-, β(1)-, and α(2)-subunits of sGC in odontoblasts. Inflammatory mediators, reactive oxygen, and nitrogen species may impair the expression of the α(1)-, β(1)-, and α(2)-subunits in odontoblasts. The decrease of sGC at the protein level in inflamed odontoblasts is compatible with a critical role for sGC to mediate biological effects of NO in health.     

Correlated expression of human beta defensin-1, -2 and -3 mRNAs in gingival tissues of young children

OBJECTIVE: Human beta-defensins (hBDs) are a group of antimicrobial peptides, expressed by the epithelial cells of many organs including gingival epithelium. The present study examined correlation between the gene expressions of hBD-1, -2, -3 mRNAs and the inflammatory cytokines in human gingival tissues. STUDY DESIGN: The gingival tissues were obtained from surgical discards from 20 different patients (age range, 5-13 years). The expression levels of mRNAs were evaluated by quantitative RT-PCR with LightCycler. The mRNA expression levels were normalized with those of keratin 10 mRNA. The data were statistically analysed using Person's correlation coefficient. RESULTS: The expression levels of hBD-1,-2 and -3 were significantly correlated with each other and also correlated with that of TNF-alpha. CONCLUSIONS: The results indicate that the expression levels of hBDs vary from one individual to another.     

Transforming Growth Factor-β1 (TGF-β1) in dentine matrix

Transforming Growth Factor-β (TGF-β) and other members of this family of growth factors have been implicated in tooth development and dental tissue repair. This study aimed to investigate regulatory factors for TGF-β1 in rabbit incisor dentine matrix and the expression of receptors for TGF-β in dental tissues better to understand the control of its biological activity. Approximately half of the TGF-β1 in dentine matrix was present in active form. TGF-β1 was found in association with latency associated peptide (LAP), betaglycan and decorin in an isolated dentine matrix preparation. Immunohistochemistry showed strong staining for TGF-β type I and II receptors in odontoblasts with more variable and weaker staining of other pulpal cells. Association of TGF-β1 with betaglycan, decorin and LAP may regulate the availability and biological activity of this growth factor and influence its presentation to the TGF-β type I and II receptors on odontoblasts. During dental tissue repair, such control processes will be important in regulating the biological effects of TGF-β1 on cells of the dentine-pulp complex.