The Urban Heat Island at Toledo, Ohio

Author Institution: Geography Department, Kent State UniversityThirty-one years of daily maximum and minimum temperatures at a rural site and a roof-top urban site were examined to determine the magnitude and seasonal variability of the urban heat island. Mean annual temperature was 2.0°C warmer at the urban site with the greatest urban-rural temperature difference occurring during the summer and the smallest difference during the spring. The urban heat island was more evident in daily minimum temperatures than in daily maxima. The number of days over 32°C (90°F) was more than doubled by the urban heat island and the number of freezing days was reduced by 16%. The freeze-free season was lengthened approximately 24 days by the urban warming, heating degree days were reduced by 10%, and cooling degree days were increased by 70%

Climatic Summary of Snowfall and Snow Depth in the Ohio Snowbelt at Chardon

Author Institution: Geography Department and Water Resources Research Institute, Kent State UniversitySnowfall records were examined for the period 1945-85 at Chardon, OH, the only station with a long climatic record in the snowbelt. Average seasonal snowfall was 269 cm (106 in) with a seasonal maximum of 410 cm (161 in). Seasonal snowfall was positively correlated with other sites in the lower Great Lakes snowbelts and along the western slope of the Appalachians from Tennessee to Quebec, but was not correlated with snowfall in the snowbelts of the upper Lakes. The time series of seasonal snowfall was not random but showed weak year-to-year persistence. The average number of days with 2.5 cm (1 in) of snowfall was 35. The average dates of the first and last 2.5 cm snowfalls of the winter were 10 November and 4 April. The largest two-day snowfall of the winter averaged 33 cm. The average number of days with 2.5 cm of snow cover was 82. Daily probability of snow cover reached the seasonal maximum of 86% in mid-January and early February. These results may be reasonably extrapolated throughout the Ohio snowbelt for applications in vegetation studies, animal ecology, hydrology, soil science, recreation, and transportation studies

Winter Sub-Freezing Periods and Significant Thaws in the Boreal Forest Region of Central North America

Winter daily maximum temperatures were examined for 56 sites in northern portions on Ontario, Michigan, Wisconsin, and Minnesota over the period 1960-88. The longest sub-freezing period of winter averaged 20-30 days in the southern portion of the region, 30-40 days around Lake Superior, and 90-100 days in extreme northwestern Ontario. These are twice as long as sub-freezing periods at similar latitudes in eastern Canada. The sub-freezing period is shortened by about one week along the shores of the Great Lakes. There is annual spatial correlation of the longest sub-freezing period, indicating regional synoptic-scale control. The late 1970s had the longest sub-freezing periods but no significant linear trend was found in lengths of sub-freezing periods. The average date of the first significant thaw (>10 C) ranged from early March in the south to late April in the north and delayed 1- 2 weeks along the shores of the Great Lakes.Key words: winter, freezing temperature, boreal forest, Canada, Great LakesDe 1960 à 1988, on a mené une étude sur les températures quotidiennes maximales en hiver à 56 emplacements situés dans des régions septentrionales de l'Ontario, du Michigan, du Wisconsin et du Minnesota. La plus longue période de gel hivernal persistant durait en moyenne de 20 à 30 jours dans la partie méridionale de la région, de 30 à 40 jours autour du lac Supérieur, et de 90 à 100 jours dans la partie la plus au nord-ouest de l'Ontario. Ces durées sont deux fois plus longues que les périodes de gel persistant aux mêmes latitudes dans l'est du Canada. La période de gel persistant est réduite d'environ 1 semaine le long des rives des Grands Lacs. Il existe une corrélation spatiale annuelle de la période de gel persistant la plus longue, ce qui indique un contrôle régional à échelle synoptique. La fin des années 1970 comptait les périodes de gel persistant les plus longues, mais on n'a pas trouvé de tendance linéaire significative dans la durée des périodes de gel persistant. La date moyenne du premier dégel notable (>10 °C) allait de début mars dans le Sud à fin avril dans le Nord et était repoussée de 1 à 2 semaines le long des rives des Grands Lacs.Mots clés : hiver, température inférieure à O’C, forêt boréale, Canada. Grands Lac

In vitro tooth cleaning efficacy of manual toothbrushes around brackets

The purpose of this laboratory study was to assess the potential cleaning efficacy of nine different toothbrushes around brackets in vitro. Standard and Mini Diamond™ brackets were fixed on coloured teeth in a special model, coated with white titanium oxide, brushed in a machine with different manual toothbrushes (three different types: planar, staged, and v-shaped bristle field), and tested with a horizontal motion for 1 minute. After brushing, the teeth were scanned and the black surfaces were planimetrically assessed using a grey scale. Tooth areas which were black again after brushing indicated tooth surface contact of the filaments. The remaining white tooth areas around the brackets indicated ‘plaque-retentive' niches. Statistical analysis was carried out using the Kruskal-Wallis one-way test of variance for individual comparison. Bonferroni adjustment was used for multiple testing, and comparison of bracket size with Wilcoxon signed rank test. In the most critical area of 2 mm around the brackets, there was no statistically significant difference between the different toothbrushes evaluated. The untouched area ranged from 11 to 26 per cent of the initially whitened tooth surface. By pooling the toothbrushes according to their design, the median cleaning efficacy of the v-shaped (73.1 per cent) and staged (75.6 per cent) toothbrushes resulted in significantly superior cleaning efficacy than planar toothbrushes (60.7 per cent) for standard brackets. For mini bracket type, staged toothbrushes showed a significantly better mean cleaning efficacy (77.8 per cent) than planar (65 per cent) and v-shaped (72.4 per cent) toothbrushes. Staged and v-shaped brush designs resulted in superior cleaning efficacy of teeth with fixed orthodontic attachments than toothbrushes with a planar bristle field. None of the tested toothbrushes showed a consistent, significantly higher cleaning efficacy than the others in this in vitro experimen

Endodontic drug delivery for root surface disinfection: a laboratory feasibility evaluation

OBJECTIVES This study aims to assess the potential of a mixture of three antibiotics (TreVitaMix, TVM) as an intracanal dressing to disinfect the outer root surface by applying a new in vitro model. MATERIALS AND METHODS Fifty freshly extracted bovine roots were endodontically treated. Forty samples were then thoroughly scaled, mounted to petri dishes, gas sterilized, and randomly allocated to four groups (n = 10/group) according to their intracanal medication: sterile saline (NaCl; control, A); the TVM carrier material alone, i.e., propylene glycol (PG; B); TVM (C); and calcium hydroxide (D). In an additional group (E), the cementum was not removed and TVM was placed. Petri dishes were filled with Fastidious Anaerobe Agar, inoculated with Fusobacterium nucleatum suspension and then anaerobically incubated during 48-h intervals at 37 °C up to 192 h. Inhibition zones around the roots were then measured after each incubation period (mm(2)). RESULTS Only teeth inoculated with the TVM dressing showed inhibition at all time points, whereas the other treatments showed no peri-radicular growing inhibition. Presence of cementum had no negative effect on disinfection (p = 0.9320). CONCLUSION TVM was able to penetrate through the dentine and inhibit the bacterial growth of F. nucleatum up to 192 h. CLINICAL RELEVANCE TVM might have the potential to sustainably disinfect the outer root surface in perio-endo lesions and serve as an adjunctive antimicrobial agent

Potential of shock waves to remove calculus and biofilm

Effective calculus and biofilm removal is essential to treat periodontitis. Sonic and ultrasonic technologies are used in several scaler applications. This was the first feasibility study to assess the potential of a shock wave device to remove calculus and biofilms and to kill bacteria. Ten extracted teeth with visible subgingival calculus were treated with either shock waves for 1min at an energy output of 0.4mJ/mm2 at 3Hz or a magnetostrictive ultrasonic scaler at medium power setting for 1min, which served as a control. Calculus was determined before and after treatment planimetrically using a custom-made software using a grey scale threshold. In a second experiment, multispecies biofilms were formed on saliva-preconditioned bovine enamel discs during 64.5h. They were subsequently treated with shock waves or the ultrasonic scaler (N = 6/group) using identical settings. Biofilm detachment and bactericidal effects were then assessed. Limited efficiency of the shock wave therapy in terms of calculus removal was observed: only 5% of the calculus was removed as compared to 100% when ultrasound was used (P ≤ 0.0001). However, shock waves were able to significantly reduce adherent bacteria by three orders of magnitude (P ≤ 0.0001). The extent of biofilm removal by the ultrasonic device was statistically similar. Only limited bactericidal effects were observed using both methods. Within the limitations of this preliminary study, the shock wave device was not able to reliably remove calculus but had the potential to remove biofilms by three log steps. To increase the efficacy, technical improvements are still required. This novel noninvasive intervention, however, merits further investigatio

Influence of caries infiltrant contamination on shear bond strength of different adhesives to dentin

Objectives: To analyze whether the contamination with a caries infiltrant system impairs the adhesive performance of etch-and-rinse and self-etching adhesives on dentin. Materials and methods: Dentin contamination with the caries infiltrant system (Icon, DMG) was simulated by applying either hydrochloric acid (15% HCl, Icon Etch, 15s), the resin infiltrant (Icon infiltrant, 4min), or both prior to the application of the respective adhesives (each group n = 10). In the control groups, the etch-and-rinse adhesive (Optibond FL, Kerr) and the self-etching adhesive (iBOND Self Etch, Hereaus) were applied without former contamination with the infiltrant system. Additionally, the adhesive performance of the resin infiltrant alone was tested. Shear bond strength of a nano-hybrid composite was analyzed after thermocycling (5,000×, 5-55°C) of the specimens and analyzed by ANOVA/Scheffé post hoc tests (p < 0.05) and Weibull statistics. Failure mode was inspected under a stereomicroscope at × 25 magnification. Results: Contamination with the resin infiltrant alone did not impair shear bond strength, while contamination with hydrochloric acid or with hydrochloric acid and the resin infiltrant reduced shear bond strength (MPa) of the adhesives (Optibond FL: 20.5 ± 3.6, iBOND Self Etch: 17.9 ± 2.6) significantly. Hydrochloric acid contamination increased the number of adhesive failures. The adhesive performance of the caries infiltrant system alone was insufficient. Conclusion: The contamination with the caries infiltrant system impaired the shear bond strength of conventional dental adhesives. Clinical relevance: Contamination of the caries infiltrant system on dentin should be avoided due to the detrimental effect of hydrochloric acid etchin