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Objectives: To assess the association between different factors in saliva and dental caries experience in children with bronchial asthma. Materials and methods: A total of 60 asthmatic children and 60 healthy controls of both genders with age ranging from 4-to 12-year-old. The asthmatics were grouped according to disease severity into mild, moderate, or severe asthma. All the children were clinically examined to assess their dental caries experience (deft/DMFT), and stimulated saliva samples were collected to measure the saliva pH, flow rate, ά-amylase, and secretory immunoglobulin A (sIgA)-level changes. The data were statistically analyzed using the SPSS program (v. 23) to test for significance at p ≤ 0.05. Results: Asthmatic children presented significantly higher deft mean value (6.77 ± 1.69), as well as significantly reduced stimulated saliva flow (0.82 ± 0.2) and sIgA (29.42 ± 6.31) when compared to healthy control. The sIgA of asthmatics showed statistically significant negative correlation with deft and DMFT. Severe asthmatics presented significantly the lowest sIgA mean level (23.61 ± 5.33) and the most reduced saliva flow rate (0.64 ± 0.20). Conclusion:The reduction in saliva flow rate and secretory immunoglobulin A render asthmatic children more prone to increased dental caries progression mainly of primary dentition.

The present paper experimentally examines the influence of the progressive variations of the central air jet velocity in a concentric circular-elliptical inverse diffusion flame (IDF) on the visual and thermal structure and stability of the developed flames. All experiments are conducted at a fixed fuel flow rate (liquefied petroleum gas) throughput that emerges from the annular elliptic passage having an aspect ratio of 2:1. The visual images are aided via a digital camera and shadowgraphs, while the thermal structure (axial and radial temperature profiles) is acquired using a bare fine wire (125 µm) thermocouple; rendering radiation loss insignificant. The visual images and shadowgraphs clearly indicate the existence of four regimes: (i) an annular partially premixed region at the burner rim, (ii) an inner central premixed blue flame, (iii) an outer luminous yellowish post combustion zone and (iv) the flame tip buoyant zone. The progressive increases of the central average air velocity ( ̅ = 7.4 m/s up to 31.3 m/s) result in shortening the visible flame length and narrowing the flame width. These are coupled with changing the flame appearance from a yellowish diffusion flame with a sooty core regime to an intense central premixed flame surrounded by a soot ring to blue flames exhibiting intense central radiation regime associated with soot oxidation. At extremely high air velocity > 21 m/s, locals flame extinction and re-ignition occurs at the boundaries of the ellipse minor axis and further increase of ̅ causes complete extinction of the main flame. These findings are very much supported by the mean gas temperature measurements that indicate steep temperature rise associated with the formation of a central premixed combustion within the flame core which is followed by the diffusion mode of combustion. A plateau of the axial temperature profiles is observed in the transition zone between the two regions whereby the rise in temperature due to soot oxidation is balanced by the radiation loss.

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