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dissertation (9)


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2019 (9)

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Dissertation
Awareness of Forensic Odontologists Regarding Post-Traumatic Stress Disorder After Mass Fatality
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Year: 2019 Publisher: Leuven KU Leuven. Faculteit Geneeskunde

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Deze master thesis onderzocht of de forensisch odontoloog risico heeft voor het ontwikkelen van post-traumatische stress. Een enquête werd opgesteld en gestuurd naar forensisch odontologen die internationaal actief zijn. Deze enquête bevatte verschillende vragen gaande over symptomen van post-traumatische stress. Als hoofdresultaat vonden we dat de internationale forensisch odontoloog geen risico vertoonde voor het ontwikkelen van post-traumatische stress. Een ander belangrijk resultaat was dat 85% van de participanten geloofde dat training tegen post-traumatische stress geïncorporeerd moest worden in de training forensich odontologen

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Dissertation
Deep Learning based age estimation of third molars in panoramic images.
Authors: --- --- ---
Year: 2019 Publisher: Leuven KU Leuven. Faculteit Ingenieurswetenschappen

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The biological age of a person is critical in many legal settings related to sports and forensics. A typical scenario is to determine the age of athletes, unaccompanied fugitives claiming to be minors or a corpse. This demands for a method to determine the biological age of a person by doing relevant tests. In this regard, third molar-based age estimation looks a promising approach as the third molar shows distinct patterns of growth corresponding to the biological age of the person. The current methodology of age estimation from third molars involves radiology expertise to manually categorize the panoramic X-ray images to the development stage and later use statistical models to predict the biological age. This process is time-consuming and cumbersome. The goal of the project is to automate the age assessment process from dental radiograph images. The focus of the thesis is on exploring the advancements in deep learning for dental age estimation with an emphasis on regression and ordinal regression methods. The Dataset for the experiments consists of 2214 dental radiograph images distributed over age ranges of 8-24 years. Five-fold cross-validation was used to evaluate the models. A deep learning model with, Densenet201 as the convolutional neural network, achieved the best results with the ordinal regression method. The corresponding Mean Absolute Error (MAE) was 1.15 years.

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Dissertation
Genetic Influence on Human Tooth Development - Systematic Literature Review
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Year: 2019 Publisher: Leuven KU Leuven. Faculteit Geneeskunde

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Tooth development relies completely on the interaction between epithelium and the mesenchyme, thereby transitioning from the initiation stages to bud, cap, bell and advanced bell stages and finally eruption of tooth in the oral cavity. For each tooth class, the above stages take place under the influence of specific genes, which are regulated by the signalling pathways. Genes play important part in the initial phases of tooth development, from birth till the age of 14 years, contributing 80% to their development Dental age can be evaluated for different population groups as genes are main regulators for tooth development, with the environmental factors having a smaller influence, especially in the early stages of life. Thereafter tooth development relies on interaction of genetic, epigenetic and environmental factors. The aim of this study was to understand the influence of genes on tooth development. A systematic review was done according to Cochranes Manual of Systematic Reviews of Intervention with articles being searched online on PubMed/NCBI. Of the 2547 articles identified, 19 were included for data extraction. Data extracted pertained to the gene, the pathways, tooth class, tooth part and mutation effects. With this review an understanding of the extent to which the genes influenced dental development; and other factors, if involved, then how they influenced tooth development. Result: One article each provided information to link a Gene to: Tooth Class + Tooth Part & Tooth Class +Tooth Part + Mutation Effect. A possibility to trace a gene to a specific part of the tooth or to overall tooth development was attempted by depicting the outcomes of the data extraction with the help of a flow diagram.

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Dissertation
Potential of Temporomadibular Joint measures ob CBCTs fo human identification
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Year: 2019 Publisher: Leuven KU Leuven. Faculteit Geneeskunde

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Objectives: specific morphologic aspects of the temporomandibular joint (TMJ) on CBCT could be considered as an identifier for human identification. The aim of the current study was to quantify the potential of specific measures from TMJ on CBCT images, separate or combined, for subject identification. Methods: CBCTs of TMJ of 198 Slavic and Eastern origin patients were examined to find out which parameters of the joint were potential identifiers. Evaluation of parameters was performed using ICATVision and GIMP software. One representative slice where measurements were performed, for both planes, was chosen. Afterwards, nine landmarks on sagittal and 6 landmarks of frontal planes, for right and left sides simultaneously, were established. Width, height, length of TMJ were measured between the landmarks. Also, two angles were allocated. In total, 14 parameters were measured on the sagittal plane and 4 on the frontal plane. Whereupon, statistical analysis was done. At first step; sex and side were analyzed separately (univariate analysis) to find out if there is a significant difference between the left and right side and significant difference between males and females. In the next step; interaction between sex and sides were evaluated (multivariate analysis). Results: Periost density showed to be the most unique single measurement. The side of the joint does not make difference for the identifying purposes.There is no significant difference between right and left sides, however, there is a considerable (p<0,0001) impact of sex on some of the variables. When it comes for a combination of the variables, the most unique patterns of identifiers (12,12%) showed 26 parameters together. Conclusion: Considering discussed outcomes, the present study indicated the possibility for obtaining information from morphologic identifiers like TMJ. By combining 26 parameters of the joint it is possible to garner additional information which can be used for identification purposes in forensic practise.

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Dissertation
Dental age estimation in northwest Indians based on the development of permanent teeth and third molars.
Authors: --- ---
Year: 2019 Publisher: Leuven KU Leuven. Faculteit Geneeskunde

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In the last decade need for age, estimation has increased in INDIA because of medicolegal/criminal cases such as rape, child labor. Aim of this study was to estimate the dental age by validating performances of D (lower left quadrant), K(TM) and D+K(combined) in relation to sex-specific age prediction. 1300 panoramic radiographs northwest(NW) Indian subjects were used. Two staging techniques were used. Demirjian’s et al(D)[7] staging technique for all developing seven mandibular permanent teeth and modified Kohler(K) et al was used to evaluate all available third molars(TM). The comparison was quantified by MAE, RMSE and mean width and coverage of the prediction interval. The conclusion was D+K model was providing better age prediction information than D and K models separately.

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Dissertation
Dental Age estimation combining permanent teeth and third molars in a Western Indian population.
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Year: 2019 Publisher: Leuven KU Leuven. Faculteit Geneeskunde

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Aim: The aim of this study was to evaluate the age prediction performance when the third molar information is added to permanent teeth in children and subadults from western Indian population. Material & Methods: A sample of 1533 orthopantomograms of Indian males (M) and females (F), in the age range between 2 and 23.99 years were collected retrospectively. The Demirjian staging technique was used on the lower left permanent teeth, and the technique of Gleiser et al modified by Köhler et al. was applied to stage all present third molars. Continuation ratio models were obtained for permanent teeth (PT), third molars (TM), permanent teeth and third molars combined (PT + TM) as predictors and age as the response. Mean error (ME;), Mean absolute error (MAE), Root mean squared error (RMSE), Coverage and width prediction intervals were calculated from the models. Results: When third molar information was added to permanent teeth, the decrease in mean error (ME) was 0.10 years in M and 0.13 years in F. Whereas, the decrease in Mean absolute error (MAE) was 0.36 years (4.4 months) in M and 0.43 years (5.2 months) in F. An overall, decrease in root mean squared error (RMSE) of 0.52 years (6.3 months) in males and females both. The highest decrease in RMSE was noted for the age category of 14 to 14.99 years in males (1.41 years) and between 23 to 23.99 years in females (1.67 years) when PT+TM model was compared to PT model. Conclusion: Inclusion of the third molar developmental information to permanent teeth does improve the age prediction performance in Indian children and subadults. Especially in the age groups of 13 to 14.99; 20 to 22.99 and 11 to 16.99; 21 to 23.99 for males and females respectively.

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Dissertation
Literatuuronderzoek naar de transfereerbaarheid van de tandmorfologie in beetsporen
Authors: --- ---
Year: 2019 Publisher: Leuven KU Leuven. Faculteit Geneeskunde

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Een beetspoor kan een belangrijk element zijn in forensisch onderzoek maar de analyse ervan bleek in het verleden niet altijd even betrouwbaar, wat tot foutieve veroordelingen kan leiden. Daarom is het belangrijk om na te gaan welke factoren hierbij een rol spelen. Doel: onderzoek van de factoren die de transfer van gebitskenmerken naar een beetspoor en de analyse ervan beïnvloeden. Methode: er werd d.m.v. de PICO-methode een literatuurstudie uitgevoerd door het doorzoeken van de online databank MEDLINE®/Pubmed® om studies rond de vervorming van beetsporen of beetspooranalyse te selecteren. Resultaten: van de 217 bekomen resultaten, werden 13 artikels geselecteerd. Volgende data werd geëxtraheerd: onderzochte parameters, aantal beetsporen, richting van de beetsporen op de huid, aantal kadavers of levende personen gebruikt als substraat, locatie van de beetsporen op het substraat, de geanalyseerde tanden, beetspoor applicatie techniek, registratietechniek gebruikt voor datacollectie, methode voor data analyse en studieresultaten. Er werden 5 combinaties van onderzochte parameters gevonden: vorm en grootte (n=1); vorm, grootte en hoek (n=6); mesiodistale breedte en afstand tussen de hoektanden (n=1); mesiodistale breedte, afstand tussen de hoektanden en tandrotatie ten op zichte van de mesiodistale as (n=4); en oppervlakte van de dentale bijtranden en mesiodistale breedte (n=1). Tussen 1 en 89 beetsporen werden meestal loodrecht op de Langerlijnen aangebracht op 1 tot 40 substraten ter hoogte van verschillende locaties. Boven- en onderkaak werden vaak samen bestudeerd met focus op de anterieure regio (n=8) of volledige tandenboog (n=1). In drie artikels werden enkel de fronttanden van onderkaak bekeken en in één artikel slechts enkele fronttanden van de bovenkaak. Elf artikels gebruikten uitsluitend tweedimensionale (2D) registratie en onderzochten primaire vervorming, één artikel uitsluitend driedimensionale (3D) registratie en één artikel maakte een vergelijking van beide. Deze laatste twee onderzochten secundaire vervorming. Veertien digitale ‘landmarks’ werden in vier artikels aan de hand van tpsDIG® software geplaatst op de digitale afbeeldingen van beetsporen en ingescande gebitsmodellen. Bij één artikel werden aspecifieke referentiepunten rond het beetspoor getekend, dat met RolleiMetric® software omgezet werd tot een 3-dimensionaal datamodel. Bij drie artikels werden pseudo-beetsporen onderzocht en bij twee hiervan werden pseudobeetsporen onderling vergeleken, in plaats van zoals in de andere gevallen het gebitsmodel met de beetsporen te vergelijken. Deze vergelijking gebeurde meestal met behulp van superimpositie (n=9), maar bij twee artikels hiervan werd geen software maar affiene transformatie gebruikt. Conclusie: binnen de primaire vervorming speelt weefselvervorming een grotere rol dan dynamische vervorming. Anatomische locatie van het beetspoor, anisotropie van de huid en individuele tandhoogte van de dader hebben een belangrijke invloed. Men moet zeer voorzichtig zijn met pogingen om primaire beeldvervorming te corrigeren en steeds de meest eenvoudige methode hanteren. 3D dataregistratie heeft veel voordelen en toekomstperspectief, maar is niet altijd toepasbaar. Forensische beetspooranalyse moet dus met alle voorzichtigheid behandeld worden en vergt nog veel wetenschappelijk onderzoek.

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Dissertation
Uniekheid van tandmorfologie gebaseerd op lineaire en oppervlaktemetingen in panoramische opnames
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Year: 2019 Publisher: Leuven KU Leuven. Faculteit Geneeskunde

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Forensische odontologie kent de laatste jaren een enorme opmars, zowel in de beetspooranalyse als in dentale identificatie. Beide vergelijkende processen steunen op een belangrijk concept, namelijk dat de menselijke dentitie uniek is. Nu zijn er de dag van vandaag nog heel wat onzekerheden over de morfologische uniekheid van de menselijke dentitie. Door sommige onderzoekers wordt die uniekheid wetenschappelijk geclaimd. Door anderen wordt dit resultaat in twijfel getrokken of wordt het tegengestelde beweerd, namelijk dat die uniekheid niet wetenschappelijk te bewijzen is. Het doel van huidig onderzoek is om aan de hand van lineaire en oppervlaktemetingen op panoramische opnames de morfologische uniekheid van de menselijke dentitie aan te tonen. De methode bestaat uit het uitvoeren van metingen, betreffende verschillende tanddimensies en -oppervlaktes op 101 panoramische opnames (51 mannen, 50 vrouwen; 15-25 jaar). De metingen werden vergeleken tussen homologe, paarsgewijze onderhoektanden, eerste onderpremolaren en -molaren. Ook werd het percentage overlap berekend per tandsoort. Uit de resultaten van de beschrijvende en vergelijkende statistiek kon geen morfologische uniekheid worden afgeleid uit de homologe, paarsgewijze onderzochte tanden. Wel konden geslachtverschillen in de humane dentitie worden aangetoond, met name dat mannen grotere tanden hebben dan vrouwen.

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Dissertation
Measurement of morphological features of maxillary first molar crowns for human identification

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Improvements in oral health and the trend for minimal invasive, computer-aided dentistry turns classical protocols for human identification redundant. Three-dimensional, morphological comparison is becoming an important identification tool. This research aims to measure specific morphologic features of maxillary first molars and to quantify their identifying power, separately and in combination. One hundred and sixty four upper first molars were isolated from 3D digitally scanned, dental cast models and standardized dimension measurements were registered using the 3D modelling software 3-Matic Medical (Materialise N.V., Leuven, Belgium). Fifteen measurements were classified in 4 groups: tooth depth (in mm, n=1), measurement between the cusps (in mm, n=6), measurement between the cusps and the core of the tooth (in mm, n=4), and angles between cusps (in degrees, n=4). All measurements were registered by the first examiner (n=2460). After a month, a subset (n=600) was re-analyzed by the first examiner and by a second examiner. The distance between each subject in the subset and the subjects in the complete sample was quantified for each measurement to establish a mean potential set (MPS) of candidate matches. The MPS, expressed as the amount of possible matches that would not exclude the correct subject in the complete sample, was determinant in the quantification of uniqueness of each specific measurement (univariate). Intra class correlation coefficient (ICC) was calculated to quantify inter- and intra-observer reliability. Differences and agreement between right and left measurements were evaluated. The 4 groups of measurements were combined between each other for a multivariate analysis of uniqueness. The most unique measurement was tooth depth (ICC=0,879, MPS=17,1%), followed by the measurement between distal cusps and the measurement between the core of the tooth and the disto-palatinal cusp (ICC=0,855, MPS=19,9% and ICC=0,840, MPS=20,9%, respectively). The measurement between the mesio-buccal and disto-palatinal cusps (ICC=0,524, MPS=32,3%) was the least unique. In the multivariate combination of measurements, the angles between cusps (n=4) were the most powerful identifiers (MPS= 3,911%). The measurement between the mesio-palatinal and disto-buccal cusps was the only measurement revealing statistically significant differences between right and left side (mean difference -0,25, p=0.0008). Agreement between measurements of right and left molars varied. The mean ICC for the intra- and inter-observer reliability were 0,75 and 0,78, respectively. Digital measurements of morphological features of maxillary first molars can present a useful tool in protocols for human dental identification. Validation of these measurements in a forensic set up is required.

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