66 research outputs found
REGRESSION OF WHITE SPOT ENAMEL LESIONS - A NEW OPTICAL METHOD FOR QUANTITATIVE LONGITUDINAL EVALUATION IN-VIVO
No full textMining Aircraft Telemetry Data With Evolutionary Algorithms
No full textThe Ganged Phased Array Radar - Risk Mitigation System (GPAR-RMS) was a
mobile ground-based sense-and-avoid system for Unmanned Aircraft System (UAS)
operations developed by the University of North Dakota. GPAR-RMS detected proximate
aircraft with various sensor systems, including a 2D radar and an Automatic Dependent
Surveillance - Broadcast (ADS-B) receiver. Information about those aircraft was then
displayed to UAS operators via visualization software developed by the University of
North Dakota. The Risk Mitigation (RM) subsystem for GPAR-RMS was designed to
estimate the current risk of midair collision, between the Unmanned Aircraft (UA) and a
General Aviation (GA) aircraft flying under Visual Flight Rules (VFR) in the surrounding
airspace, for UAS operations in Class E airspace (i.e. below 18,000 feet MSL). However,
accurate probabilistic models for the behavior of pilots of GA aircraft flying under VFR
in Class E airspace were needed before the RM subsystem could be implemented.
In this dissertation the author presents the results of data mining an aircraft
telemetry data set from a consecutive nine month period in 2011. This aircraft telemetry
data set consisted of Flight Data Monitoring (FDM) data obtained from Garmin G1000
devices onboard every Cessna 172 in the University of North Dakota\u27s training fleet.
Data from aircraft which were potentially within the controlled airspace surrounding
controlled airports were excluded. Also, GA aircraft in the FDM data flying in Class E
airspace were assumed to be flying under VFR, which is usually a valid assumption.
Complex subpaths were discovered from the aircraft telemetry data set using a novel
application of an ant colony algorithm. Then, probabilistic models were data mined from
those subpaths using extensions of the Genetic K-Means (GKA) and Expectation-
Maximization (EM) algorithms.
The results obtained from the subpath discovery and data mining suggest a pilot
flying a GA aircraft near to an uncontrolled airport will perform different maneuvers than
a pilot flying a GA aircraft far from an uncontrolled airport, irrespective of the altitude of
the GA aircraft. However, since only aircraft telemetry data from the University of North
Dakota\u27s training fleet were data mined, these results are not likely to be applicable to GA
aircraft operating in a non-training environment
Regression of white spot enamel lesions: A new optical method for quantitative longitudinal evaluation in vivo
No full textThis article describes a new nondestructive optical method for evaluation of lesion regression in vivo. White spot caries lesions were induced with orthodontic bands in two vital premolars of seven patients. The teeth were banded for 4 weeks with special orthodontic bands that allowed plaque accumulation on the buccal surface. The teeth were left in the dentition for 2 or 4 weeks after debanding. Regular oral hygiene with a nonfluoridated toothpaste was applied during the entire experimental period. The optical scattering coefficient of the banded area was measured before banding and in 1-week intervals thereafter. The scattering coefficient returned to the sound value in an exponential manner, the half-value-time for left teeth being 1.1 week, for right teeth 1.8 weeks, these values being significantly inequal (p = 0.035). At the start of the regression period, the scattering coefficient of left teeth lesions was 2.5 as high as of right teeth lesions, values being inequal with p = 0.09. It is concluded that regression of initial lesions in the presence of saliva is a relatively rapid process. The new optical method may be of clinical importance for quantitative evaluation of enamel lesion regression developed during fixed appliance therapy
An in vivo study on the merits of two glass ionomers for the cementation of orthodontic bands
No full textThe purpose of this study was to investigate the cariostatic effect of two glass ionomer cements on in vivo demineralization of partly uncovered enamel beneath orthodontic bands. A 4-week clinical trial was conducted on a group of five patients with nine pairs of premolars to be extracted for orthodontic purposes. Specially designed orthodontic bands were cemented with either Ketac-Cem (K-C) or Aqua-Cem (A-C). A local cariogenic milieu was created between the buccal surface of the premolars and the inner surface of the bands to secure plaque accumulation. The mineral content of the teeth was quantified by microradiography. The data were compared with data from a previous study of patients in the same age group with bands that had been cemented with a non-F cement. After comparison with the non-F group, the lesion depth (ld) was reduced by 63% for K-C and by 55% for A-C. This reduction was statistically significant at the 2.5% level (t test). The total mineral loss in teeth cemented with glass ionomer cements (DELTA-Z) was reduced, in comparison with the loss in teeth cemented with non-F cement, by 49% with K-C and by 27% with A-C. The differences were statistically significant only for the K-C group (t test, p 0.05). This investigation shows that fluoride released from glass ionomer cements contributes substantially to demineralization "reduction." However, these cements do not provide complete caries protection in sites where access is difficult
Retention of titanium tetrafluoride (TiF4), used as fissure sealant on human deciduous molars
No full textWhen dental hard tissues are exposed to aqueous solutions of TiF4, an acid-resistant glaze forms on tooth surfaces. The aim of the present study was to examine the long-term retention of the glaze on TiF4-treated deciduous molars. The occlusal surfaces of four deciduous molars in each of seven children were treated with 4% TiF4 for 1 min. The sealed teeth were extracted after 1, 3, 6, or 12 months and examined with scanning electron microscopy. An extensive surface layer was present on all deciduous molars after 1 month. After 3 months the glaze appeared to be worn out on the cusp tips and in some areas on the cusp inclines. At 6 months the glaze was observed as small areas distributed over the cusp inclines with total coverage of the pits and fissures. After 1 year the presence of the glaze was limited to pits and fissures. Clinically, all fissures were caries-free by visual inspection at the end of the experimental period. The results indicate that the glaze formed after topical TiF4 application may be an effective way of sealing pits and fissures under clinical conditions
Relative Cariostatic Effects of KOH-soluble and KOH-insoluble Fluoride in situ
No full textThe relative cariostatic effects of fluoride as fluorapatite, CaF2, loosely-bound fluoride, or KOH-soluble fluoride are debated. The present study was carried out to investigate this further in an intra-oral caries model. Pairs of premolars extracted for orthodontic reasons were used. Enamel from one tooth of each pair was used as control (untreated). Two slabs were cut from the enamel of the other contralateral premolar. These slabs were treated with 2% NaF for 24 h. One slab was then treated with 1 mol/L KOH twice for 24 h for removal of all loosely-bound fluoride. The slabs treated with 2% NaF and then with 1 mol/L KOH would contain the KOH-insoluble fluoride. Those treated with only 2% NaF would, in addition, contain KOH-soluble fluoride. Each slab, control, KOH-insoluble F, and KOH-soluble and insoluble F was mounted on different upper removable appliances. The slabs were covered with orthodontic banding material, thus allowing space for plaque accumulation. Five individuals wore the appliance in three separate four-week periods. The slabs were analyzed by quantitative microradiography. The average mineral loss (delta Z) was 1680 +/- 1000 vol% x microns in the control teeth, 620 +/- 76 vol% x microns in the KOH-soluble and -insoluble F teeth, and 2167 +/- 1278 vol% x microns in the KOH-insoluble F teeth. The average lesion depths were 90 +/- 41 microns in the control teeth, 35.3 +/- 5.5 microns in the KOH-soluble F teeth, and 88 +/- 35 microns in the KOH-insoluble F teeth. It was concluded that only KOH-soluble fluoride reduced mineral loss and lesion depths significantly, compared with the untreated teeth
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