Streptococci dominate the diverse flora within buccal cells

Previously, we reported that intracellular Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythensis were present within buccal epithelial cells from human subjects, as lesser components of a polymicrobial flora. In this study, we further characterized that intracellular flora by using the same double-labeling techniques to identify Fusobacterium nucleatum, Prevotella intermedia, oral Campylobacter species, Eikenella corrodens, Treponema denticola, Gemella haemolysans, Granulicatella adiacens, and total streptococci within buccal epithelial cells. All those species were found within buccal cells. In every case, species recognized by green-labeled species-specific probes were accompanied by other bacteria recognized only by a red-labeled universal probe. Streptococci appeared to be a major component of the polymicrobial intracellular flora, being present at a level from one to two logs greater than the next most common species (G. adiacens). This is similar to what is observed in oral biofilms, where diverse species interact in complex communities that often are dominated by streptococci.     

Shaping ability of progressive versus constant taper instruments in curved root canals of extracted teeth

AIM: To compare the shaping ability of progressive versus constant taper shaft instruments in curved root canals of extracted human teeth. METHODOLOGY: A total of 40 root canals of mandibular molars with curvatures ranging between 20 degrees and 40 degrees were divided into two groups of 20 canals each and embedded in a muffle system. The root canals sectioned horizontally at three levels before preparation and then remounted into the mould. All root canals were prepared with ProTaper (progressive taper) or Hero Shaper (constant taper) instruments. Pre- and post-instrumentation radiographs and cross-sectional images were obtained. The parameters evaluated were: working safety (instrument failure, apical blockage and loss of working length) and shaping ability (straightening, cross-sectional area, transportation and centring ability). The data were analysed statistically using Student's t-test. RESULTS: No instrument fractured during preparation. One Hero Shaper instrument permanently deformed. Both instrument systems maintained working length well. The canals prepared with Hero Shaper instruments were straightened to a lesser degree (P < 0.05). ProTaper instruments removed more dentine in the coronal and the middle sections of the canals. Canals prepared with Hero Shaper instruments had less transportation (P < 0.01) and better centring ability (P < 0.05) in the apical section. CONCLUSIONS: Both instrument systems were safe to use and maintained working length well. The canals prepared with Hero Shaper had less transportation and were better centred in the apical region, possibly because their smaller taper reduced instrument stiffness.     

前牙美学修复牙冠延长和前导转移

前牙美学修复应以保证口颌系统的健康和功能为前提，不能仅关注牙齿颜色、形态以及部分排列的调整。若不重视前牙引导下颌前伸和侧方运动的功能（即前导），修复治疗则可能引起患者口颌系统的相应改变，严重时会导致相关器官的功能障碍和病变。     

Immunocytochemical localization of growth hormone receptor in rat maxillary teeth.

To address the question of what role growth hormone may have in stimulating tooth formation, the distribution of its receptor/binding protein in developing rat incisors and molars was studied immunocytochemically using well-characterized monoclonal antibodies. Ten female 45-day-old Wistar rats were perfused with 4% paraformaldehyde. Five-microns paraffin sections of the growing end of maxillary incisors and molars were cut, deparaffinized and incubated with mouse anti-growth hormone receptor antibodies or control antibodies. A three-layer streptavidin peroxidase technique was used to detect bound antibody. Immunoreaction product was associated primarily with the cytoplasm of cells at certain stages of differentiation. Dividing cells, differentiating preameloblasts and preodontoblasts, secretory ameloblasts and odontoblasts showed immunoreactivity. Undifferentiated dental epithelium cells, stellate reticulum, external dental epithelial cells, mature odontoblasts, and most of cells in the dental papilla were non-reactive. However, at certain stages of tooth development, the stratum intermedium and the external dental epithelium also stained positively. The presence of growth hormone receptor/binding protein in tooth cells at different stages of their development indicates that growth hormone may influence cell proliferation, differentiation and differentiated functions of ameloblasts, odontoblasts and cementoblasts independent of a systemic mediator, and thus may be involved in stimulating odontogenesis directly.