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Editor's Note: The International City/County Management Association (ICMA) celebrates the 100th anniversary of its founding in 2014. This article is the first of several that will appear during the next year about the council‐manager plan to commemorate ICMA's 100th anniversary. Three contemporary leadership challenges face local governments today. The first encourages department heads to more actively work the intersection between political and administrative arenas. The second promotes collaborative work, synchronizing city and county boundaries with problems that have no jurisdictional homes. The third argues that citizen engagement is no longer optional—it is imperative—and that connecting engagement initiatives to traditional political values and governing processes is an important mark of successful community building. These three leadership challenges stem from a widening gap between the arenas of politics and administration—that is, between what is politically acceptable in public policy making and what is administratively sustainable. The gap is fueled by conflicting trends experienced locally and common internationally. Failure to bridge this gap between political acceptability and administrative sustainability results in decreasing legitimacy for governing institutions and increasing challenges.

A preliminary survey of age changes in human teeth by Nalbandian,1 2 utilizing the multifactorial point system proposed by Gustafson,3 suggested that the relative transparency of root dentin-generally known as "sclerosis"-might be among the more reliable dental aging characteristics, presumably least affected by the superimposed pathology to which the crown portion of teeth is prone. It seemed worthwhile, therefore, to examine the nature of the age changes in the root dentin more closely.In the present study structural alterations associated with sclerotic root dentin have been observed by means of optical and electron microscopy as well as by high-resolution microradiography. While similar techniques have been employed individually as applied to studies on crown dentin, there does not appear to be any previous study comparing the combined results of these several approaches in the study of typical sclerotic age changes in the root dentin of human teeth.The classical studies of W. D. Miller,4 Beust,5-7 and Bodecker and Lefkowitz,8 9 demonstrated alterations in the optical appearance of ground sections of dentin as well as a decrease in permeability to dyes coincident with aging. These changes could be the result of intratubular calcification, which would inhibit the diffusion of dyes and cause the refractive index of the tubules to approach that of the intertubular dentin, thus modifying the relative transparency.Recently a number of microradiographic investigations of crown dentin'0-'6 have revealed areas of considerably greater X-ray absorption in relation to the dentinal tubules than in the general dentin matrix, suggesting deposition of highly concentrated minerals. For example, J. Miller'0 demonstrated a highly mineralized zone around the odontoblastic processes in microradiographs of dentin from unerupted teeth. Similar observations were made by Blake" in sound teeth from eleven-to thirteen-year-olds. Bergmann and Engfeldt12 studied by microradiography the transparent dentin under superficial caries. Their material showed, in addition to hypercalcified zones around many tubules, other tubules which appeared to be completely obliterated by highdensity material. The following year Rbckert13 reported complete tubular obliteration in the crown dentin of young and old non-carious teeth, stating that there was a greater tendency toward tubular obliteration with increasing age. Downloaded from SCLEROTIC AGE CHANGES IN ROOT DENTIN 5Bradford'4 15 has studied the structure and "maturation" of dentin by optical microscopy of ground sections and sections of decalcified material, noting various stages in a progression of tubular "maturation," culminating in complete tubular obliteration.The most conclusive demonstration of a hypercalcified peritubular zone was recently made by Frank'6 in electron-microscopic studies of undecalcified sections of crown dentin from unerupted third molars.It appears that the hypercalcified peritubular zone is a normal structure in dentin, with the possible exception of areas near the preden...

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Polytetrafluoroethylene membranes (ePTFE) used in guided tissue regeneration (GTR) are accessible to colonization by oral bacteria. The bacterial composition of the adherent biomass is unknown. We examined a total of 6 membranes that were retrieved after 4 to 6 weeks from human periodontitis sites, using optical and transmission electron microscopy (TEM) as well anaerobic cultivation. Five of the 6 membranes provided the microbiological data and microscopic data. TEM revealed an organized microbial mass covering the surfaces and also within the interstices of the open microstructure and occlusive portions of the membranes. Numerous bacterial forms including cocci, rods, and filaments with an interbacterial matrix, frequently in microcolonies, were identified. Anaerobic cultivation yielded Streptococcus and Actinomyces species with a minor component of Gram‐negative facultative rods comprised mainly of Haemophilus species. Candida species was recovered from one membrane. These data show that ePTFE is heavily colonized by oral bacteria during retention. The impact of bacterial colonization of ePTFE is not known but it seems reasonable to assume that colonization of membranes may affect connective tissue regeneration. Further studies will be needed to examine the effect of systemic antimicrobials on ePTFE colonization and in turn to examine the effect on GTR. J Periodontol 1993;64:162–168.