Longitudinal study on the influence of Nd:YAG laser irradiation on microleakage associated of two filling techniques.

Objective: This study investigates the effects of Nd:YAG laser irradiation on apical and coronal seals, when used prior to two root canal filling techniques. Background Data: Limited information exists regarding the effects of morphologic changes to dentin walls following Nd: YAG laser irradiation on the sealing ability of root fillings. Methods: Two hundred forty teeth were analyzed by observing coronal and apical leakage of Indian ink (DL), and 60 were analyzed for through-and-through leakage using the fluid transport model (FTM). The Nd: YAG laser parameters were 1.5W, 100mJ, and 15Hz (four times for 5s at 20s intervals). Each group consisted of a lased and a nonlased subgroup: each subgroup had root fills done by either cold lateral condensation (CLC) or hybrid condensation (HC). Leakage was assessed after 48 h, and then at 1, 6, and 12 months. The DL group was divided into four groups of 15 teeth for each evaluation point. Through-and-through leakage (L in microliters/day) was measured for 48h under a pressure of 1.2 atm using FTM, and recorded as L = 0 (L1), 0 10 (L3). Results: Apical and coronal dye leakage was observed in all groups. Significant differences (p < 0.05) in apical leakage were found between HC and HC + Nd after 1, 6, and 12 months, and between CLC and CLC + Nd at 6 and 12 months. No significant differences were found between laser-irradiated and non-laser-irradiated groups with FTM. Conclusion: Pulsed Nd: YAG laser irradiation following root canal preparation may reduce apical leakage in association with hybrid gutta-percha condensation

Investigation of coronal leakage of root fillings after smear layer removal with EDTA or Nd:YAG lasing through capillary flow porometry

Objective: This study investigates the effects of Nd:YAG laser irradiation combined with different irrigation protocols on the marginal seal of root fillings. Background data: Limited information exists regarding the effects of morphologic changes to root canal (RC) walls after Nd:YAG laser irradiation after smear-layer removal with EDTA on the sealing ability of root fillings. Methods: The 75 root-filled teeth (5 × 15 teeth) were analyzed for through-and-through leakage by using capillary flow porometry (CFP). The RC cleaning procedure determined the assignment to a group: (1) irrigation with NaOCl 2.5% and EDTA 17% or standard protocol (SP), (2) SP + Nd:YAG lasing (dried RC), (3) NaOCl 2.5% + Nd:YAG lasing (dried RC), (4) SP + Nd:YAG lasing (wet RC), or (5) NaOCl 2.5% + Nd:YAG lasing (wet RC). Groups 1r to 5r consisted of the same filled teeth with resected apices up to the most apical point of the preparation length. Resection was performed after the first CFP measurement. Roots were filled with cold lateral condensation. CFP was used to assess minimum, mean flow and maximum pore diameters after 48 h, and immediately after these measurements, including root resection. Statistics were performed by using nonparametric tests (p > 0.05). An additional three roots per group were submitted to SEM of the RC wall. Results: Through-and-through leakage was observed in all groups. Statistically significant differences were observed in maximum pore diameter: 1r > 3r, and 1r > 5r; in mean flow pore diameter: 1r > 2r, 2r < 4r (p < 0.05). Typical Nd:YAG glazing effects were observed when the smear layer was present and exposed to the laser fiber (i.e., in the groups without use of EDTA) or when the fiber tip made direct contact with a smear-layer free RC wall. Conclusions: The reduction in through-and-through leakage is significantly higher with the Nd:YAG laser as smear-layer modifier than when smear layer is removed with an EDTA rinsing solution

Different mechanisms of goose influence both accelerate and retard the decomposition process in an Arctic wetland

Background and aims Due to human induced changes in their wintering grounds, goose numbers increased dramatically over the past 50 years. To understand the consequences of these changes, studies on key ecosystem processes, like decomposition, on the breeding grounds in the generally severely nutrient limited Arctic are indispensable. This article reports on the influence of Barnacle Geese Branta leucopsis on the decomposition process and the release of nitrogen from litter on high-Arctic Svalbard (78° 55' N, 11° 56' E). Methods The study made use of paired long-term exclosures and control plots. Litter and goose droppings were collected and subsequently analysed on chemical parameters to understand the influence of grazing via a change in dead organic matter quality within and between plant growth forms and faeces. Reciprocal transplantation of dead organic matter (graminoids, mosses, roots and faeces) between ungrazed (exclosures) and heavily grazed areas, using the litterbag technique, was used to study the goose grazing influence on litter decomposition and nitrogen release through a shift in environmental conditions. The possibly facilitating role of goose faeces was investigated by studying decomposition in separate subplots with faeces addition in some of the exclosures. Results In the exclosures almost twice the necromass of grazed plots was present and the contribution of litter originating from graminoids and roots was respectively twice and four times as much in the exclosures compared to the grazed plots. This is important seen the fact that these growth forms were found to differ in litter quality. Together with the place of production and thus incubation, this resulted in a decrease in decomposition and nitrogen release rates in the following order: roots, graminoids and moss. Goose-induced changes in litter composition thus impeded decomposition. Environmental impact of geese, in contrast, was found to enhance decomposition, but not nitrogen release rates of the same litter type. Goose faeces, characterised by a distinct chemical quality, were found to decompose as slow as moss litter and release nitrogen as fast as graminoid litter

Influence of goose grazing on plant availability of nutrients

Nutrient availability is a primary limiting factor of biotic functioning in Arctic environments. We hypothesized that geese, whose numbers have increased dramatically, impact on the plant availability of nutrients. The moss layer was thought to play a key role herein. To test for these hypotheses we measured plant availability of macro- and micronutrients over the winter and growing season and moss depth in a goose exclosure experiment. Our results show that important nutrients were significantly influenced by goose grazing. For some elements this could be partially explained by the grazing impact on the moss layer. During the winter season nutrient availability was remarkably high and was influenced by geese, urging the need for more ecological research during this period