Publications by authors named "A Daboul"

16 Publications

  • Page 1 of 1

A deep cascaded segmentation of obstructive sleep apnea-relevant organs from sagittal spine MRI.

Int J Comput Assist Radiol Surg 2021 Mar 26. Epub 2021 Mar 26.

Department of Computational Neuroscience, Georg-August-University, Friedrich-Hund Platz, 1, 37077, Göttingen, Germany.

Purpose: The main purpose of this work was to develop an efficient approach for segmentation of structures that are relevant for diagnosis and treatment of obstructive sleep apnea syndrome (OSAS), namely pharynx, tongue, and soft palate, from mid-sagittal magnetic resonance imaging (MR) data. This framework will be applied to big data acquired within an on-going epidemiological study from a general population.

Methods: A deep cascaded framework for subsequent segmentation of pharynx, tongue, and soft palate is presented. The pharyngeal structure was segmented first, since the airway was clearly visible in the T1-weighted sequence. Thereafter, it was used as an anatomical landmark for tongue location. Finally, the soft palate region was extracted using segmented tongue and pharynx structures and used as input for a deep network. In each segmentation step, a UNet-like architecture was applied.

Results: The result assessment was performed qualitatively by comparing the region boundaries obtained from the expert to the framework results and quantitatively using the standard Dice coefficient metric. Additionally, cross-validation was applied to ensure that the framework performance did not depend on the specific selection of the validation set. The average Dice coefficients on the test set were [Formula: see text], [Formula: see text], and [Formula: see text] for tongue, pharynx, and soft palate tissues, respectively. The results were similar to other approaches and consistent with expert readings.

Conclusion: Due to high speed and efficiency, the framework will be applied for big epidemiological data with thousands of participants acquired within the Study of Health in Pomerania as well as other epidemiological studies to provide information on the anatomical structures and aspects that constitute important risk factors to the OSAS development.
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http://dx.doi.org/10.1007/s11548-021-02333-0DOI Listing
March 2021

Is Continuous Eruption Related to Periodontal Changes? A 16-Year Follow-up.

J Dent Res 2021 Mar 3:22034521999363. Epub 2021 Mar 3.

Department of Restorative Dentistry, Periodontology, Endodontology, Preventive Dentistry and Pedodontics, University Medicine Greifswald, Greifswald, Germany.

The aims of this study were to 1) determine if continuous eruption occurs in the maxillary teeth, 2) assess the magnitude of the continuous eruption, and 3) evaluate the effects of continuous eruption on the different periodontal parameters by using data from the population-based cohort of the Study of Health in Pomerania (SHIP). The jaw casts of 140 participants from the baseline (SHIP-0) and 16-y follow-up (SHIP-3) were digitized as 3-dimensional models. Robust reference points were set to match the tooth eruption stage at SHIP-0 and SHIP-3. Reference points were set on the occlusal surface of the contralateral premolar and molar teeth, the palatal fossa of an incisor, and the rugae of the hard palate. Reference points were combined to represent 3 virtual occlusal planes. Continuous eruption was measured as the mean height difference between the 3 planes and rugae fix points at SHIP-0 and SHIP-3. Probing depth, clinical attachment levels, gingiva above the cementoenamel junction (gingival height), and number of missing teeth were clinically assessed in the maxilla. Changes in periodontal variables were regressed onto changes in continuous eruption after adjustment for age, sex, number of filled teeth, and education or tooth wear. Continuous tooth eruption >1 mm over the 16 y was found in 4 of 140 adults and averaged to 0.33 mm, equaling 0.021 mm/y. In the total sample, an increase in continuous eruption was significantly associated with decreases in mean gingival height ( = -0.34; 95% CI, -0.65 to -0.03). In a subsample of participants without tooth loss, continuous eruption was negatively associated with PD. This study confirmed that continuous eruption is clearly detectable and may contribute to lower gingival heights in the maxilla.
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http://dx.doi.org/10.1177/0022034521999363DOI Listing
March 2021

Association between coronal caries and malocclusion in an adult population.

J Orofac Orthop 2020 Dec 18. Epub 2020 Dec 18.

Department of Prosthetic Dentistry, Gerodontology and Biomaterials, University Medicine Greifswald, Walther-Rathenau-Str. 42a, 17475, Greifswald, Germany.

Purpose: Only a few but conflicting results have been reported on the association between malocclusions and caries. We investigated this association using data from the population-based cross-sectional Study of Health in Pomerania (SHIP).

Methods: Sagittal, vertical and transversal intermaxillary relationship, space conditions and sociodemographic parameters of 1210 dentate subjects (median age 30 years, interquartile range 25-35 years) were collected. Caries was assessed with the Decayed-Missing-Filled Surfaces index but analyzed as ordered outcome (four levels: sound, enamel caries, caries, tooth loss) in ordinal multilevel models, taking into account subject, jaw, and tooth level simultaneously.

Results: Anterior open bite ≤3 mm (odds ratio [OR] = 2.08, 95% confidence interval [CI]: 1.19-3.61), increased sagittal overjet of 4-6 mm (OR = 1.31, CI: 1.05-1.64), distal occlusion of ½ premolar width (OR = 1.27, CI: 1.05-1.53) and distal 1 premolar width (OR = 1.31, CI: 1.06-1.63) were associated with adjusted increased odds for a higher outcome level (caries). Anterior spacing (OR = 0.24, CI: 0.17-0.33), posterior spacing, (OR = 0.69, CI: 0.5-0.95), posterior crowding (OR = 0.57, CI: 0.49-0.66) and buccal nonocclusion (OR = 0.54, CI: 0.33-0.87) were associated with a lower outcome level (caries).

Conclusion: The results from this population-based study suggest that a connection between caries and malocclusion exists to a limited extent in young adults. The associations with caries are contradictory for several malocclusion variables. Distal occlusion (OR = 1.31, CI: 1.06-1.63) and related skeletal anomalies displayed positive associations with caries whereas crowding did not. Orthodontic treatment of anterior crowding would probably not interfere with caries experience. These aspects should be considered for patient information and in treatment decisions.
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http://dx.doi.org/10.1007/s00056-020-00271-1DOI Listing
December 2020

Are third molars associated with orofacial pain? Findings from the SHIP study.

Community Dent Oral Epidemiol 2020 10 18;48(5):364-370. Epub 2020 May 18.

Department of Oral and Maxillofacial Surgery/Plastic Surgery, University Medicine Greifswald, Greifswald, Germany.

Objectives: To examine the association between third molars and orofacial pain. We hypothesized that impacted third molars are a cause of orofacial pain.

Methods: Magnetic resonance images of 1808 participants from two population-based cohorts from Northeastern Germany were analysed to define the status of third molars according to the Pell and Gregory classification. A self-reported questionnaire and a clinical dental examination were used to detect chronic and acute complaints of orofacial pain, masticatory muscle pain, migraine and other types of headache. Logistic regression models were used to analyse the associations between third molar status and orofacial pain.

Results: Individuals with impacted third molars in the maxilla had a higher chance of chronic orofacial pain than those with erupted third molars (odds ratio 2.19; 95% CI 1.19-4.02). No such association was detected for third molars in the lower jaw. Third molars were not associated with masticatory muscle pain, migraine or other types of headache.

Conclusions: Impacted maxillary third molars might be a cause of chronic orofacial pain. Thus, physicians should consider the eruption/impaction status of third molars in their decision-making process when treating patients who complain of orofacial pain.
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http://dx.doi.org/10.1111/cdoe.12540DOI Listing
October 2020

Does craniofacial morphology affect third molars impaction? Results from a population-based study in northeastern Germany.

PLoS One 2019 22;14(11):e0225444. Epub 2019 Nov 22.

Department of Prosthodontics, Gerodontology and Biomaterials, University Medicine Greifswald, Greifswald, Germany.

Objectives: It is still not clear why impaction of third molars occurs. Craniofacial morphology and facial parameters have been discussed to be strong predictors for third molar impaction. Thus, this study aimed to investigate the effect of craniofacial morphology on erupted or impacted third molars in a German population sample.

Materials And Methods: Erupted and impacted third molars in 2,484 participants from the Study of Health in Pomerania were assessed by whole-body magnetic resonance imaging. Markers of facial morphology were determined in 619 individuals of those participants in whose 421 participants (16.7%) had at least one impacted third molar. Craniofacial morphology was estimated as linear measurements and was associated in a cross-sectional study design with impacted and erupted third molars by multinomial logistic regression models. Erupted third molars were used as reference outcome category and regression models were adjusted for age and sex.

Results: Maximum Cranial Width (Eurion-Eurion distance) was significantly associated with impacted third molars (RR: 1.079; 95% confidence interval 1.028-1.132). This association was even more pronounced in the mandible. Individuals with a lower total anterior facial height (Nasion-Menton distance) and a lower facial index also have an increased risk for impacted third molars in the mandible (RR 0.953; 95% confidence interval 0.913-0.996 and RR: 0.943; 95% confidence interval 0.894-0.995). No significant associations of third molar status with facial width (Zygion-Zygion distance), and sagittal cranial dimension (Nasion-Sella distance; Sella-Basion distance) were observed.

Conclusion: Individuals with an increased maximal cranial width have a higher risk for impaction of third molars in the mandible and in the maxilla. Individuals with a lower anterior total anterior facial height and lower facial index also have an increased risk for third molars impaction in the mandible. These findings could help orthodontic dentists, oral surgeons and oral and maxillofacial surgeons in decision-making for third molars removal in their treatment. These findings highlight the necessity of an additional analysis of the maximal cranial width by the Eurion- Eurion distance.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0225444PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6874347PMC
March 2020

A deep learning framework for efficient analysis of breast volume and fibroglandular tissue using MR data with strong artifacts.

Int J Comput Assist Radiol Surg 2019 Oct 6;14(10):1627-1633. Epub 2019 Mar 6.

Department of Computational Neuroscience, Georg-August-University, Friedrich-Hund Platz, 1, 37077, Göttingen, Germany.

Purpose: The main purpose of this work is to develop, apply, and evaluate an efficient approach for breast density estimation in magnetic resonance imaging data, which contain strong artifacts including intensity inhomogeneities.

Methods: We present a pipeline for breast density estimation, which consists of intensity inhomogeneity correction, breast volume segmentation, nipple extraction, and fibroglandular tissue segmentation. For the segmentation steps, a well-known deep learning architecture is employed.

Results: The average Dice coefficient for the breast parenchyma is [Formula: see text], which outperforms the classical state-of-the-art approach by a margin of [Formula: see text].

Conclusion: The proposed solution is accurate and highly efficient and has potential to be applied for big epidemiological data with thousands of participants.
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http://dx.doi.org/10.1007/s11548-019-01928-yDOI Listing
October 2019

New insights in the link between malocclusion and periodontal disease.

J Clin Periodontol 2019 02;46(2):144-159

Department of Prosthetic Dentistry, Gerodontology and Biomaterials, University Medicine Greifswald, Greifswald, Germany.

Aim: We aimed to investigate associations between malocclusions and periodontal disease by comparing it to that of smoking in subjects recruited from the population-based cross-sectional study "Study of Health in Pomerania."

Materials And Methods: Sagittal intermaxillary relationship, variables of malocclusion and socio-demographic parameters of 1,202 dentate subjects, 20-39 years of age, were selected. Probing depth (PD) and attachment loss (AL) were assessed at four sites by tooth in a half-mouth design. Analyses were performed with multilevel models on subject, jaw and tooth level.

Results: Distal occlusion determined in the canine region, ectopic position of canines, anterior spacing, deep anterior overbite and increased sagittal overjet were associated with AL (p-value <0.05). Associations between malocclusions and PD: deep anterior overbite with gingival contact (odds ratio [OR] = 1.40, 95% CI: 1.08-1.82; p-value = 0.0101) and anterior crossbite (OR = 1.75, 95% CI: 1.29-2.38; p-value = 0.0003). Regarding crowding, only severe anterior crowding was compatible with a moderate to large association with PD (OR = 1.93, 95% CI: 0.89-4.20). Compared to smoking, the overall effect of malocclusions was about one half for AL and one-third for PD.

Conclusion: Malocclusions or morphologic parameters were associated with periodontal disease.
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http://dx.doi.org/10.1111/jcpe.13062DOI Listing
February 2019

Influence of Age and Tooth Loss on Masticatory Muscles Characteristics: A Population Based MR Imaging Study.

J Nutr Health Aging 2018 ;22(7):829-836

Dr. Amro Daboul, Department of Prosthodontics, Gerodontolgy and Biomaterials, University Medicine Greifswald, Walther-Rathenau Str. 42, 17489 Greifswald, Germany,

Background: Aging is associated with a decline in masticatory muscles mass and performance. The present study aims to examine the differences in the cross-sectional areas of the masseter, medial and lateral pterygoid muscles in relation to age and the present dental status in a population-based magnetic resonance imaging study.

Methods: This cross sectional study involved 747 subjects aged between 30-89 years (344 male, 403 female) who underwent both a whole body MRI and a full oral examination. The cross-sectional areas of the masseter, medial and lateral pterygoid muscles were measured from MRI images using the software Osirix. Dental and prosthetic status data from the oral examination were classified according to Eichner index. The method of generalized least squares, also called growth curve model, was used to examine the associations between the cross-sectional areas, age and tooth status.

Results: The cross-sectional area of the lateral pterygoid muscle decreased substantially with age in women but did not depend on age in men. The medial pterygoid muscle depended on age but an effect modification by gender was uncertain. Masseter muscle was weakly associated with age but strongly associated with the number of teeth in both genders.

Conclusions: Our findings suggest that age has a heterogeneous effect on masticatory muscles. This indicates that age related changes to the masticatory muscles are muscle specific and are not consistent between the different muscles.
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http://dx.doi.org/10.1007/s12603-018-1029-1DOI Listing
October 2019

Procrustes-based geometric morphometrics on MRI images: An example of inter-operator bias in 3D landmarks and its impact on big datasets.

PLoS One 2018 22;13(5):e0197675. Epub 2018 May 22.

Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, Modena-Italy.

Using 3D anatomical landmarks from adult human head MRIs, we assessed the magnitude of inter-operator differences in Procrustes-based geometric morphometric analyses. An in depth analysis of both absolute and relative error was performed in a subsample of individuals with replicated digitization by three different operators. The effect of inter-operator differences was also explored in a large sample of more than 900 individuals. Although absolute error was not unusual for MRI measurements, including bone landmarks, shape was particularly affected by differences among operators, with up to more than 30% of sample variation accounted for by this type of error. The magnitude of the bias was such that it dominated the main pattern of bone and total (all landmarks included) shape variation, largely surpassing the effect of sex differences between hundreds of men and women. In contrast, however, we found higher reproducibility in soft-tissue nasal landmarks, despite relatively larger errors in estimates of nasal size. Our study exemplifies the assessment of measurement error using geometric morphometrics on landmarks from MRIs and stresses the importance of relating it to total sample variance within the specific methodological framework being used. In summary, precise landmarks may not necessarily imply negligible errors, especially in shape data; indeed, size and shape may be differentially impacted by measurement error and different types of landmarks may have relatively larger or smaller errors. Importantly, and consistently with other recent studies using geometric morphometrics on digital images (which, however, were not specific to MRI data), this study showed that inter-operator biases can be a major source of error in the analysis of large samples, as those that are becoming increasingly common in the 'era of big data'.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0197675PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5963746PMC
November 2018

Development and testing of satisfaction questionnaires for patients with removable dental prostheses.

Quintessence Int 2017 ;48(6):487-496

Objective: To develop and test self-administered satisfaction questionnaires for patients with removable dental prostheses (RDPs) in the German language.

Method And Materials: A three-phase methodology was used. A pilot questionnaire was developed in phase one. At the end of phase two, the final version of the questionnaires were reached. In phase three, 192 questionnaires were distributed to evaluate the psychometric properties of the final version of the questionnaires. Construct validity, content validity from the patients' perspective, and questionnaire reliability were estimated.

Results: At the end of phase two, the final versions of the questionnaires were defined as instruments with good face validity. At the end of phase three, content validity from the patients' perspective was assessed and found to be good. Exploratory factor analysis identified a one-factor model for each questionnaire. Consequently, each questionnaire was summed to create a single index. Internal consistency of the indexes was assessed using Cronbach's α and found to be excellent (α > 0.9). A high repeatability of all the items was identified through a test-retest. Intra-class correlation coefficient (ICC) values ranged from 0.80 to 0.99.

Conclusion: The questionnaires and indexes are valid and highly reliable instruments, and can be used to measure patient satisfaction with RDPs.
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http://dx.doi.org/10.3290/j.qi.a38201DOI Listing
October 2018

Estimating effects of craniofacial morphology on gingival recession and clinical attachment loss.

J Clin Periodontol 2017 Apr 18;44(4):363-371. Epub 2017 Feb 18.

Department of Prosthodontics, Gerodontology and Biomaterials, University Medicine Greifswald, Greifswald, Germany.

Objectives: Evidence on possible associations between facial morphology, attachment loss and gingival recession is lacking. We analysed whether the facial type, which can be described by the ratio of facial width and length (facial index), is related to periodontal loss of attachment, hypothesizing that a broad face might be associated with less gingival recession (GR) and less clinical attachment loss (CAL) than a long face.

Materials And Methods: Data from the 11-year follow-up of the population-based Study of Health in Pomerania were used. Periodontal loss of attachment was assessed by GR and CAL. Linear regression models, adjusted for age and gender, were used to assess associations between specific landmark based distances extracted from magnetic resonance imaging head scans and clinically assessed GR or CAL (N = 556).

Results: Analysing all teeth, a higher maximum cranial width was associated with a lower mean GR (B = -0.016, 95% CI: -0.030; -0.003, p = 0.02) and a lower mean CAL (B = -0.023, 95% CI: -0.040; -0.005, p = 0.01). Moreover, a long narrow face was significantly associated with increased mean GR and CAL (facial index, P for trend = 0.02 and p = 0.01, respectively). Observed associations were more pronounced for incisors and canines than for premolars and molars.

Conclusion: This study revealed craniofacial morphology, specifically the cranial width and the facial index, as a putative risk factor for periodontal loss of attachment.
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http://dx.doi.org/10.1111/jcpe.12661DOI Listing
April 2017

Clinical performance during 48 months of two current glass ionomer restorative systems with coatings: a randomized clinical trial in the field.

Trials 2016 May 8;17(1):239. Epub 2016 May 8.

Polyclinic of Prosthodontics and Biomaterials, Greifswald University, Rotgerberstr. 8, Greifswald, 17475, Germany.

Background: This study was carried out as a prospective clinical field study with the aim of evaluating the clinical performance of Equia Fil® with a nanofilled resin coating and the conventional Fuji IX GP® fast with an LC coating according to the World Dental Federation (FDI) restoration material evaluation criteria.

Methods: The clinical performance of Equia Fil® and Fuji IX GP® fast was evaluated on permanent posterior teeth of 643 adult patients aged between 20 to 80 years old in randomly selected clinics across Germany. Occlusal cavities in posterior permanent teeth were restored with Equia Fil® with a nanofilled, light-cured resin coating (n = 515) and Fuji IX GP® fast with an LC coating (n = 486). Direct clinical assessment as well as photographic assessment and assessment of stone casts of the restorations were made at 1 year, 2 years, 3 years, and 4 years.

Results: In 4 years, a total of 1001 fillings from both materials were placed by 111 dentists in 643 patients. Random slope models showed that the Equia filling system had overall lower odds of obtaining a delta event (material needs replacement) in comparison to Fuji IX GP® fast with an LC coating within all models. In both materials, filling size/surface was the most important component affecting the clinical performance of the materials. When measuring the odds of obtaining a delta event (material needs replacement), the odds ratios jumped to approximately 43 and 296 times for class II (two surfaces) and class II mesial-occlusal-distal (three surfaces) respectively in comparison to class I fillings.

Conclusion: Both materials showed similar good overall performance in class I cavities; however, when including numbers from both class I and II fillings, the Equia system with a nanofilled resin coating showed better overall performance with fewer failures in all the follow-up intervals. Nonetheless, the percentage of unsatisfactory to poor fillings according to the FDI criteria was relatively high in two-surface class II fillings and higher in three-surface class II fillings for both materials.

Trial Registration: Deutsches Register Klinischer Studien (German Clinical Trials Register): DRKS00004220. ( www.germanctr.de ). Registration date: 6 Sept 2012.
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http://dx.doi.org/10.1186/s13063-016-1339-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4860258PMC
May 2016

Dental practitioner recruitment for a randomized clinical trial in the field to evaluate the performance of a new glass ionomer restoration material.

Trials 2016 Feb 10;17:73. Epub 2016 Feb 10.

Policlinic of Prosthodontics and Biomaterials, Greifswald University, Greifswald, Germany.

Background: In 2009, we began recruiting dental practitioners across Germany to participate in a clinical trial to evaluate the clinical performance of EQUIA, a new glass ionomer restoration material. The aim of this paper is to discuss the outcomes of the dental practitioner recruitment and outline the process of establishing a practice-based research network.

Methods: Study proposals were sent to randomly selected dental offices in 29 cities in Germany. The proposals were sent until a minimum of 10 clinics in each city declared participation. Later on, briefing lectures informed the participating practitioners about the design, methods, and material application procedure. Participants were familiarized with the guidelines of Good Manufacturing Practice (GMP) and Good Epidemiological Practice (GEP). A questionnaire describing the characteristics of each dental office was filled out by the participating practitioner. Additionally, participation levels were characterized according to the socioeconomic status and geographic districts of residence in Germany (Regions 0 to 9). The associations between the characteristics were tested by the Kruskal-Wallis Test and Chi-squared test (P < 0.05).

Results: A total of 3194 private dental clinics were invited, 1712 clinics refused to participate, 1195 did not respond to the invitation, and 323 agreed to participate. Only 144 clinics participated in the lectures held in their cities and signed the participation agreement. Based on their geographic location, the highest participation was in Region 2 with a participation rate of 14.3%, and the lowest participation was in Region 6 with a participation rate of 1.7%. Regions with the lowest rate of unemployment and relatively higher rates of income (Regions 7 and 8) had the highest rate of refusals (86%).

Conclusion: The initial results of the dental practitioner recruitment in this study suggest that the recruitment and pre-randomization design were successful, and by reaching out to a considerable number of private dental clinics to participate, we were able to recruit a smaller number of highly motivated dentists in this clinical study. Regional differences in socioeconomic status, practitioner specialization, and differences in patient health care insurance have to be considered when recruiting dental practitioners for clinical trials.

Trial Registration: The trial has been registered at Deutsches Register Klinischer Studien (German register of clinical trials) on 6 September 2012 under DRKS-ID: DRKS00004220.
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http://dx.doi.org/10.1186/s13063-016-1198-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4748549PMC
February 2016

Reproducibility of Frankfort horizontal plane on 3D multi-planar reconstructed MR images.

PLoS One 2012 31;7(10):e48281. Epub 2012 Oct 31.

Polyclinic of Prosthodontics and Biomaterials, Greifswald University, Greifswald, Germany.

Objective: The purpose of this study was to determine the accuracy and reliability of Frankfort horizontal plane identification using displays of multi-planar reconstructed MRI images, and propose it as a sufficiently stable and standardized reference plane for craniofacial structures.

Materials And Methods: MRI images of 43 subjects were obtained from the longitudinal population based cohort study SHIP-2 using a T1-weighted 3D sequence. Five examiners independently identified the three landmarks that form FH plane. Intra-examiner reproducibility and inter-examiner reliability, correlation coefficients (ICC), coefficient of variability and Bland-Altman plots were obtained for all landmarks coordinates to assess reproducibility. Intra-examiner reproducibility and inter-examiner reliability in terms of location and plane angulation were also assessed.

Results: Intra- and inter-examiner reliabilities for X, Y and Z coordinates of all three landmarks were excellent with ICC values ranging from 0.914 to 0.998. Differences among examiners were more in X and Z than in Y dimensions. The Bland-Altman analysis demonstrated excellent intra- as well as inter-examiner agreement between examiners in all coordinates for all landmarks. Intra-examiner reproducibility and inter-examiner reliability of the three landmarks in terms of distance showed mean differences between 1.3 to 2.9 mm, Mean differences in plane angulation were between 1.0° to 1.5° among examiners.

Conclusion: This study revealed excellent intra-examiner reproducibility and inter-examiner reliability of Frankfort Horizontal plane through 3D landmark identification in MRI. Sufficiently stable landmark-based reference plane could be used for different treatments and studies.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0048281PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3485237PMC
April 2013

A genome-wide association study identifies five loci influencing facial morphology in Europeans.

PLoS Genet 2012 Sep 13;8(9):e1002932. Epub 2012 Sep 13.

Department of Forensic Molecular Biology, Erasmus MC University Medical Center Rotterdam, Rotterdam, The Netherlands.

Inter-individual variation in facial shape is one of the most noticeable phenotypes in humans, and it is clearly under genetic regulation; however, almost nothing is known about the genetic basis of normal human facial morphology. We therefore conducted a genome-wide association study for facial shape phenotypes in multiple discovery and replication cohorts, considering almost ten thousand individuals of European descent from several countries. Phenotyping of facial shape features was based on landmark data obtained from three-dimensional head magnetic resonance images (MRIs) and two-dimensional portrait images. We identified five independent genetic loci associated with different facial phenotypes, suggesting the involvement of five candidate genes--PRDM16, PAX3, TP63, C5orf50, and COL17A1--in the determination of the human face. Three of them have been implicated previously in vertebrate craniofacial development and disease, and the remaining two genes potentially represent novel players in the molecular networks governing facial development. Our finding at PAX3 influencing the position of the nasion replicates a recent GWAS of facial features. In addition to the reported GWA findings, we established links between common DNA variants previously associated with NSCL/P at 2p21, 8q24, 13q31, and 17q22 and normal facial-shape variations based on a candidate gene approach. Overall our study implies that DNA variants in genes essential for craniofacial development contribute with relatively small effect size to the spectrum of normal variation in human facial morphology. This observation has important consequences for future studies aiming to identify more genes involved in the human facial morphology, as well as for potential applications of DNA prediction of facial shape such as in future forensic applications.
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http://dx.doi.org/10.1371/journal.pgen.1002932DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3441666PMC
September 2012

Artifacts in magnetic resonance imaging and computed tomography caused by dental materials.

PLoS One 2012 22;7(2):e31766. Epub 2012 Feb 22.

Polyclinic of Prosthodontics and Biomaterials, Greifswald University, Greifswald, Germany.

Background: Artifacts caused by dental restorations, such as dental crowns, dental fillings and orthodontic appliances, are a common problem in MRI and CT scans of the head and neck. The aim of this in-vitro study was to identify and evaluate the artifacts produced by different dental restoration materials in CT and MRI images.

Methods: Test samples of 44 materials (Metal and Non-Metal) commonly used in dental restorations were fabricated and embedded with reference specimens in gelatin moulds. MRI imaging of 1.5T and CT scan were performed on the samples and evaluated in two dimensions. Artifact size and distortions were measured using a digital image analysis software.

Results: In MRI, 13 out of 44 materials produced artifacts, while in CT 41 out of 44 materials showed artifacts. Artifacts produced in both MRI and CT images were categorized according to the size of the artifact.

Significance: Metal based restoration materials had strong influence on CT and less artifacts in MRI images. Rare earth elements such as Ytterbium trifluoride found in composites caused artifacts in both MRI and CT. Recognizing these findings would help dental materials manufacturers and developers to produce materials which can cause less artifacts in MRI and CT images.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0031766PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3285178PMC
August 2012