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Copyright of Canadian Journal of Dental Hygiene is the property of Canadian Dental Hygienists Association and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tooth enamel has the highest degree of biomineralization of all vertebrate hard tissues. During the secretory stage of enamel formation, ameloblasts deposit an extracellular matrix that is in direct contact with the ameloblast plasma membrane. Although it is known that integrins mediate cell-matrix adhesion and regulate cell signaling in most cell types, the receptors that regulate ameloblast adhesion and matrix production are not well characterized. We hypothesized that αvβ6 integrin is expressed in ameloblasts where it regulates biomineralization of enamel. Human and mouse ameloblasts were found to express both b6 integrin mRNA and protein. The maxillary incisors of Itgb6-/- mice lacked yellow pigment and their mandibular incisors appeared chalky and rounded. Molars of Itgb6-/- mice showed signs of reduced mineralization and severe attrition. The mineral-to-protein ratio in the incisors was significantly reduced in Itgb6-/- enamel, mimicking hypomineralized amelogenesis imperfecta. Interestingly, amelogenin-rich extracellular matrix abnormally accumulated between the ameloblast layer of Itgb6-/- mouse incisors and the forming enamel surface, and also between ameloblasts. This accumulation was related to increased synthesis of amelogenin, rather than to reduced removal of the matrix proteins. This was confirmed in cultured ameloblast-like cells, in which αvβ6 integrin was not an endocytosis receptor for amelogenins, although it participated in cell adhesion on this matrix indirectly via endogenously produced matrix proteins. In summary, integrin αvβ6 is expressed by ameloblasts and it plays a crucial role in regulating amelogenin deposition and/or turnover and subsequent enamel biomineralization. [ABSTRACT FROM AUTHOR]

Scar formation is a common, unwanted result of wound healing in skin, but the mechanisms that regulate it are still largely unknown. Interestingly, wound healing in the oral mucosa proceeds faster than in skin and clinical observations have suggested that mucosal wounds rarely scar. To test this concept, we created identical experimental wounds in the oral mucosa and skin in red Duroc pigs and compared wound healing and scar development over time. We also compared the pig oral mucosal wound healing to similar experimental wounds created in human subjects. The findings showed significantly reduced scar formation at both clinical and histological level in the pig oral mucosa as compared with skin 49 days after wounding. Additionally, the skin scars contained a significantly increased number of type I procollagen immunopositive cells and an increased fibronectin content, while the oral mucosal wounds demonstrated a prolonged accumulation of tenascin-C. Furthermore, the pig oral mucosal wounds showed similar molecular composition and clinical and histological scar scores to human oral mucosal wounds. Thus, the reduced scar formation in the pig oral mucosa provides a model to study the biological processes that regulate scarless wound healing to find novel approaches to prevent scar formation in skin. [ABSTRACT FROM AUTHOR]

Theoretical, numerical and experimental methods are used to develop a comprehensive understanding of how cell shape affects the mechanical characteristics of two-dimensional aggregates such as epithelia. This is an important step in relating the mechanical properties of tissues to those of the cells of which they are composed. Statistical mechanics is used to derive formulas for the in-plane stresses generated by tensions γ along cell-cell interfaces in sheets with anisotropic cellular fabric characterized by average cell aspect ratio κ . These formulas are then used to investigate self-deformation (strain relaxation) of an anisotropic sheet composed of cells of thickness h and having effective viscosity μ . Finite element simulations of epithelia and of isolated cells and novel relaxation studies of specimens of embryonic epithelia reported herein are consistent with the predictions of the theory. In all cases, geometric factors cause the relaxation responses to be more complex than a single decaying exponential. [ABSTRACT FROM AUTHOR]

The case report describes placement of an implant in the posterior maxilla so as to avoid a pneumatized sinus and also to avoid the need for a sinus lift procedure. An 81-year-old woman presented with an edentulous span in the upper right posterior maxilla. She had been missing teeth in this area for many years, and there was a combination of resorption of the alveolar ridge and pneumatization of the maxillary sinus. Eleven years previously, implants had been placed anterior to this region, but the patient was told that implants could not be placed posteriorly unless a sinus lift was done. At the time of the current presentation she was still unwilling to undergo a sinus lift procedure but wanted to know if implants could be placed in the posterior right maxilla. A tomogram obtained with a radiographic stent in place indicated that there was insufficient bone height to allow placement of implants at the usual angulation without a sinus lift. Therefore, to avoid the need for a sinus lift, 2 implants were placed with palatal angulation as guided by tomographically determined surgical stent. The treatment planning and surgical and restorative techniques are reviewed here. A favourable for the patient and the clinicians. In the situations where there is sufficient palatal bone medial to the maxillary sinus, placing implants at an angle may prevent the need for a sinus lift procedure, assuming that proper development of an occlusal restorative scheme is possible. [ABSTRACT FROM AUTHOR]

Until recently, the accepted standard for the classification of periodontal diseases was the one agreed upon at the 1989 World Workshop in Clinical Periodontics. This classification system, however, had its weaknesses. In particular, some criteria for diagnosis were unclear, disease categories overlapped, and patients did not always fit into any one category. Also, too much emphasis was placed on the age of disease limited to the gingiva existed. In 1999, an International Workshop for a Classification of Periodontal Diseases and Conditions was organized by the American Academy of Periodontology to address these concerns and to revise the classification system. The workshop proceedings have been published in the Annals of Periodontology. The major changes to the 1989 proceedings and the rationale for these changes are summarized here. In addition, the potential impact of these changes is discussed. [ABSTRACT FROM AUTHOR]

Traditionally, periodontal hand instruments are honed or sharpened during patient care as they dull easily during contact with enamel, calculus and cementum. This approach is taught in dental and hygiene schools around the world and remains the standard of care. Recently, some professional organizations have questioned whether this practice should be abandoned because of safety issues. Questions have been raised whether sharpening stones can be properly sterilized and whether the sharpening of contaminated instruments poses a health hazard for the provider. Using bacteria culture techniques and scanning electron microscopy, we tested whether contaminated ceramic sharpening stones can be sterilized. Our results demonstrate that the stones were sterile after being subjected to the manufacturer's sterilization protocol. In addition, over the last year, no incidents related to periodontal instrument sharpening have been reported among nearly 400 students at the faculty of dentistry, University of British Columbia, where chair-side sharpening is taught. Therefore, we conclude that ceramic sharpening stones can be sterilized using normal office protocols and that chair-side sharpening adds little risk beyond routine handling of operatory or periodontal instruments during patient care when proper protocols are followed. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to an article on cracked tooth syndrome by Christopher D. Lynch and Robert J. McConnell in the September 2002 issue.

Traditionally, periodontal hand instruments are honed or sharpened during patient care as they dull easily during contact with enamel, calculus and cementum. This approach is taught in dental and hygiene schools around the world and remains the standard of care. Recently, some professional organizations have questioned whether this practice should be abandoned because of safety issues. Questions have been raised whether sharpening stones can be properly sterilized and whether the sharpening of contaminated instruments poses a health hazard for the provider. Using bacteria culture techniques and scanning electron microscopy, we tested whether contaminated ceramic sharpening stones can be sterilized. Our results demonstrate that the stones were sterile after being subjected to the manufacturer's sterilization protocol. In addition, over the last year, no incidents related to periodontal instrument sharpening have been reported among nearly 400 students at the faculty of dentistry, University of British Columbia, where chair-side sharpening is taught. Therefore, we conclude that ceramic sharpening stones can be sterilized using normal office protocols and that chair-side sharpening adds little risk beyond routine handling of operatory or periodontal instruments during patient care when proper protocols are followed.

Our research group is comparing clinical, histological and molecular healing profiles of oral and skin wounds using human and pig models. The goal is to determine the molecular cues that lead to scarless healing in the oral mucosa and use that information to develop scar prevention therapies for skin and prevent aberrant wound healing in the oral cavity. Wound healing in human and pig palatal mucosa is almost identical, and scar formation is reduced in oral wounds compared with skin. The striking difference between these tissues is transient and rapidly resolving inflammation in oral wounds compared with long-lasting inflammation in the skin wounds. Currently, we are looking at wound transcriptomes (genes differentially regulated) and proteomes (a set of proteins) to investigate how these wound healing responses in skin and oral mucosa are regulated at the molecular level.

Oral mucosal wounds heal with reduced scar formation compared with skin. The epithelial integrin alphavbeta6 is induced during wound healing, and it can activate fibrogenic transforming growth factor beta1 (TGF-beta1) and anti-fibrogenic TGF-beta3 that play key roles in scar formation. In this study, expression of beta6 integrin and members of the TGF-beta pathway were studied in experimental wounds of human gingiva and both gingiva and skin of red Duroc pigs using real-time PCR, gene microarrays, and immunostaining. Similar to human wounds, the expression of beta6 integrin was induced in the pig wounds 7 days after wounding and remained upregulated >49 days. The alphavbeta6 integrin was colocalized with both TGF-beta isoforms in the wound epithelium. Significantly higher expression levels of beta6 integrin and TGF-beta1 were observed in the pig gingival wounds compared with skin. Early gingival wounds also expressed higher levels of TGF-beta3 compared with skin. The spatio-temporal colocalization of alphavbeta6 integrin with TGF-beta1 and TGF-beta3 in the wound epithelium suggests that alphavbeta6 integrin may activate both isoforms during wound healing. Prolonged expression of alphavbeta6 integrin along with TGF-beta3 in the gingival wound epithelium may be important in protection of gingiva from scar formation.

This case report describes placement of an implant in the posterior maxilla so as to avoid a pneumatized sinus and also to avoid the need for a sinus lift procedure. An 81-year-old woman presented with an edentulous span in the upper right posterior maxilla. She had been missing teeth in this area for many years, and there was a combination of resorption of the alveolar ridge and pneumatization of the maxillary sinus. Eleven years previously, implants had been placed anterior to this region, but the patient was told that implants could not be placed posteriorly unless a sinus lift was done. At the time of the current presentation she was still unwilling to undergo a sinus lift procedure but wanted to know if implants could be placed in the posterior right maxilla. A tomogram obtained with a radiographic stent in place indicated that there was insufficient bone height to allow placement of implants at the usual angulation without a sinus lift. Therefore, to avoid the need for a sinus lift, 2 implants were placed with palatal angulation as guided by a tomographically determined surgical stent. The treatment planning and surgical and restorative techniques are reviewed here. A postoperative tomogram was obtained to determine the final position of the implants. The outcome has been favourable for the patient and the clinicians. In situations where there is sufficient palatal bone medial to the maxillary sinus, placing implants at an angle may prevent the need for a sinus lift procedure, assuming that proper development of an occlusal restorative scheme is possible.