Biomedical subjects

Ingrid Rudzki-Janson

Publications and source records attributed to Ingrid Rudzki-Janson.

10 recordsLinked to original sources

PubMed2006

Inter-individual variability of the facial morphology during conscious smiling.

INTRODUCTION: Since many simulation and animation procedures for mimicry are based on averaged values and do not take into account an individual's situation, the goal of this study was to investigate the intra- and inter-individual variability of conscious smiling. MATERIALS AND METHODS: Twenty-three surface points were marked on the faces of 31 adult test individuals. Six photographs of each subject's face were then taken under standardized conditions, one with a neutral facial expression and five while the individual was asked to smile (conscious smile "on command"). After digital superposition of the individual images (neutral and smiling) the displacements were measured for every measurement point on each individual. All data underwent statistical evaluation after normalization in the vertical and horizontal directions. Evaluation of intra- and inter-individual variability was carried out by analyzing the corresponding coefficients of variation and the formation of confidence intervals (confidence level 95%). RESULTS: The repeated measurements upon conscious smiling showed a moderate intra-individual variability with coefficients of variation under 10%. In contrast, the inter-individual variability of the measured values was relatively high. Here variation coefficients were measured of between 28% and 60% depending on the localization of the measuring point. The displacements' absolute magnitude was greatest in the lower facial third. The two corners of the mouth, the upper lip in the philtrum area, the cheeks and the side wings of the nose revealed the highest displacements. CONCLUSION: Due to the high inter-individual variability, an analysis based on averaged values or a simulation of the conscious smile must be viewed with a certain amount of criticism.

Adult↗

PubMed2006

Investigation of shear-peel bond strength of orthodontic brackets on enamel after using Pro Seal.

AIM: The aim of this investigation was to ascertain whether the use of a fluoride-releasing, light-curing sealant (Pro Seal, Reliance Orthodontic Products, Itasca, IL, USA) results in differences in shear-peel bond strength when teeth are etched via the conventional acid-etching method and with self-etching primers (SEP), respectively. We also examined whether Pro Seal functions as a substitute for the bonding agents recommended by the manufacturers. MATERIAL AND METHODS: To carry out this study, we randomly allocated 300 extracted molars (ISO 11405) into twelve groups (n=25). The brackets used (Victory Series, Twin UBi 0T/0A .022, 3M Unitek, Seefeld, Germany) were bonded using the same layer thickness of adhesive. The teeth were then stored for 24 h in de-ionized water (37 degrees C) and subsequently thermocycled. The brackets were debonded using a universal testing machine with a crosshead speed of 0.5 mm/min. For statistical evaluation we used the one-way analysis of variance (ANOVA [alpha = 0.05]) and the post hoc Tukey test and Weibull analysis. RESULTS: We could establish that the use of Pro Seal does not have a negative influence on shear-peel bond strength. When the compomer Assure was used, Pro Seal even led to an increase in shear-peel bond strength, especially when it was applied using the bonding agent recommended by the manufacturer. The highest Weibull modulus (m) was found for the self-etching primer IDEAL 1 without using Pro Seal (m=6.5) and the lowest for First Step SEP when using Pro Seal (m=2.2). There were also clear differences in characteristic shear-peel bond strength (sigma(0)) within some of the groups investigated. CONCLUSIONS: Although the statistical evaluation showed no significant negative influence on the shear-peel bond strength either when Pro Seal was used in addition, or when that fluoride-releasing, light-curing sealant was substituted for the bonding agent recommended by the manufacturer, the Weibull analysis showed that the use of Pro Seal in combination with SEP resulted in bond strength values that were less reliably reproducible.

Orthodontic Brackets↗

PubMed2006

Stresses at the cranial base induced by rapid maxillary expansion.

OBJECTIVE: An analysis of the distribution of stresses at the juvenile and adult cranial base after implementation of a rapid palatal suture expansion was the goal of this study. Of particular interest were stresses occurring near the cranial foramina containing vulnerable structures. MATERIALS AND METHODS: The stresses were simulated and analyzed using a finite elements model of the human cranial base. The model consisted of several skull bones (sphenoid, frontal bone, occipital bone, and the two temporal bones) with a total of 41,556 finite elements. To illustrate the differences between reactions in the juvenile and the adult, the differing bone elasticity was depicted as variations in the modulus of elasticity. RESULTS: At the juvenile cranial base only moderate stresses occurred during rapid palatal suture expansion, apparently precluding the likelihood of any serious complications in the area of the foramina. The situation in the adult, however, was different. Because of the reduced elasticity of the bony structures, considerable stress already occurred on light bending of the pterygoid process, especially in the area of the round foramen, the oval foramen, and the superior orbital fissure, all of which might lead to microfractures with injury of nervous and vascular structures. CONCLUSIONS: The lower the bone elasticity on carrying out a rapid palatal suture expansion, the more important safety measures are for protecting the cranial base. For this reason the pterygomaxillary connection should be severed on both sides in adults when carrying out a surgically assisted palatal suture expansion.

Adolescent↗

PubMed2006

Accuracy of facial plaster casts.

OBJECTIVE: The aim of this study was to evaluate the accuracy of facial plaster casts and their suitability for 3-D mapping. MATERIALS AND METHODS: All measurements were carried out on 15 adult probands (seven female and eight male; age range 19-31 years, mean 24.7 years). A plaster cast of the facial surface was prepared for all probands using alginate impressions. The plaster casts and the probands faces were digitized using a three-dimensional laser-scanner operating with structured light. The resulting point clouds were matched in a virtual environment to analyze the deviations between the cast and the facial surfaces, both qualitatively and quantitatively. RESULTS: The average deviations depended on the facial area and lay between 0.95 and 3.55 mm. Marked differences between the plaster cast and the facial surface were found, particularly in the area of the lips, at the roof of the nose, at the cheeks, and in the entire lower facial area. CONCLUSIONS: The regionally exacerbated soft tissue deformations that occur during impression of the facial surface lead to inaccuracies in the resulting plaster cast that forbids any use for morphometric analysis. Documentation of pathological findings in cleft lip and palate using facial plaster casts does appear to be justifiable.

Adult↗

PubMed2005

Three-dimensional soft tissue prediction using finite elements. Part I: Implementation of a new procedure.

BACKGROUND AND AIM: The prediction of soft tissue esthetics is important for achieving an optimal esthetic outcome in orthodontic treatment planning. Applicable procedures have so far been restricted to two-dimensional profile predictions that have not proven to be very reliable. The goal of this investigation was therefore to develop a novel finite element-based procedure that allows a three-dimensional, easily visualized, quantitative analysis and prediction of soft tissue behavior for the clinician. The procedure to be developed should be easy to handle and not entail any additional radiation exposure for the patient. MATERIAL AND METHODS: Using a three-dimensional scanner, the facial surfaces of 20 probands were digitalized and individual FEM models were generated. RESULTS: After reduction of data redundancy via several conversion steps, a patient-specific simulation model was prepared consisting of 20,000 to 40,000 individual elements to which specific physical properties could be assigned. The average time required for generating a virtual model was 50 minutes. Problems occurring during model generation were rare (mainly shadowing phenomena and movement artifacts). CONCLUSION: The procedure outlined herein makes the reliable generation of patient-specific simulation models possible for facial soft tissue prediction in orthodontics.

Adult↗

PubMed2005

Three-dimensional soft tissue prediction using finite elements. Part II: Clinical application.

BACKGROUND AND AIM: The goal of this study was to analyze the validity and prediction accuracy of a newly-developed procedure for three-dimensional soft tissue prediction based on Finite Element Method, and to compare the results with prediction produced using an existing two-dimensional prediction program (Dentofacial Planner Plus). PATIENTS AND METHODS: In twelve patients who underwent combined surgical-orthodontic treatment, profile prediction was generated using both procedures preoperatively and then compared at predefined measurement points with the patient's actual postoperative soft tissue status. RESULTS: The deviations observed depended on the facial region, whereby the prediction errors for both procedures were much greater in the lower facial third than in the midfacial third. Calculating in all the measurement points, the mean horizontal prediction error was 0.32 mm for the Finite Element Method and 0.75 mm for the Dentofacial Planner Plus. Overall, we were able to demonstrate the new procedure's superior validity and quality of visualization. In addition to profile prediction, the procedure allows a differentiated three-dimensional assessment of esthetically important regions such as the cheeks, nasolabial folds and the nasal wings. Additional X-radiation is not necessary in this risk-free and stress-free procedure. CONCLUSION: Three-dimensional soft tissue prediction employing finite element modeling is a useful aid for implementing esthetically-optimized treatment planning.

Adult↗

PubMed2005

Light microscopic and SEM findings after orthodontic treatment--analysis of a human specimen.

AIM: The hard and soft tissue damage caused by orthodontic forces has so far, for obvious ethical reasons, been investigated in animal models primarily. However, the validity of these results as applied to humans remains controversial. The particular value of this study is that the maxilla of a young adult could be analyzed histologically. Thus it was possible to retrospectively study the effects of a routine orthodontic therapy using light microscopy. MATERIAL AND METHODS: The upper jaw of a 24-year-old patient was investigated. He had been in orthodontic treatment with a straight-wire-appliance using superelastic materials for 18 months. Both posterior segments were analyzed in the horizontal plane using the microsection method according to Donath (toluidine blue staining). Both central incisors were analyzed using a scanning electron microscope (SEM). The examination was performed qualitatively and histomorphometrically. RESULTS: 170 lateral root resorptions were found in the nine posterior teeth, while pressure sites and interference areas with the buccal and sinus cortical bone were predominantly affected. However, the extent of root resorption was minimal: mean length 979 +/- 766 microm, mean depth 208 +/- 133 microm. The lateral root erosions presented high repair potential: 55.6% of resorption length, and 28% of the depth were repaired in 76% of all lesions. CONCLUSION: The incidence of detected root resorptions seems high at first. However, the prognosis of the affected teeth is not critically impaired, due to the lesions' minor extent (length, depth) and their high repair capacity.

Adult↗

PubMed2005

Investigation of maxillary tooth sizes in patients with palatal canine displacement.

AIM: The aim of this retrospective trial was to investigate differences in mesiodistal and vestibulo-oral crown sizes of naturally, fully-erupted permanent maxillary teeth between patients with and without palatal canine displacement. PATIENTS AND METHOD: 115 patients (mean age: 14 years 10 months; females: 77 males: 38) treated in the Department of Orthodontics, University of Munich were included in the study. 65 of the patients showed at least one palatally-displaced canine. Diagnosis and the location of the displacement were determined on the basis of standardized radiographs and confirmed by surgical documentation. Each maxillary tooth's mesiodistal and vestibulo-oral width was measured using a dial caliper on each dental cast. Excluded were partially-erupted teeth and surfaces with caries or restorations that had to be measured. An analysis of available space was made by evaluating the pre-treatment dental casts of all patients included in the study. RESULTS: Comparing the tooth widths of patients with unilateral canine displacement with the corresponding contralateral quadrants, we noted a statistically significant difference, namely that the central and lateral incisors and the canines of the affected side were narrower than those of the non-affected side in the same patient. Moreover, the displaced upper canines showed an increase in vestibulo-oral dimension. Overall tooth width (including all tooth groups) in patients with palatally-displaced canines was significantly less than that in the control group. However, when comparing the crown diameters of unilaterally- and bilaterally-affected patients, no differences in tooth-size were observed. The space-analysis showed excessive dental-arch space in patients with a palatally-displaced canine. CONCLUSION: Patients affected by palatal canine displacement showed significantly smaller maxillary tooth size.

Adolescent↗

PubMed2005

Cone-beam computed tomography in orthodontics: benefits and limitations.

INTRODUCTION: In order to obtain an overlay-free assessment of dental structures for resorption and ankylosis diagnostics, conebeam computed tomography (CBCT) is being employed more and more often in orthodontics alongside dental CT. OBJECTIVE: The aim of this study was to investigate the quality and accuracy of CBCT in the imaging of dental structures and to compare it with the imaging quality produced by dental CT. Moreover, we intended to assess the specific advantages and disadvantages of CBCT in clinical use. MATERIALS AND METHODS: The image quality of CBCT and dental CT was examined for a total of 417 teeth and their surrounding structures. 208 teeth were diagnostically recorded using volume tomography and 209 with dental CT. The axial images were assessed for metal and movement artifacts and whether there was an imprecise depiction of the enamel-dentin and pulp interface. The definition and reproductive quality of all teeth were evaluated when imaging the periodontal ligament space in the cervical, middle and apical root thirds. RESULTS: In contrast to dental CT, metal artifacts were barely apparent in the CBCT and when so, only very feebly, whereas we only observed disruptions in image quality from movement artifacts with CBCT. Image quality of the dental and surrounding bony structures was far better with dental CT on the whole than it was with CBCT. During imaging by CBCT, the periodontal ligament space either could not be, or if so, then only poorly assessed for 86% of the teeth, while this figure was only 20% for dental CT. Furthermore, the enamel-dentin interface and pulp cavity's edges were on the whole much more sharply defined in the dental CT. CONCLUSION: Dental CT still represents the gold-standard for inspecting the dental roots and their surrounding bone.

Artifacts↗

PubMed2005

Cephalometric features of Filipinos with Angle Class I occlusion according to the Munich analysis.

The purpose of this study was (1) to establish cephalometric norms for soft tissue, skeletal and dental relationships among Filipino adults; and (2) to compare these norms with the accepted German standards. Eighty-one Filipino subjects, 44 men and 37 women, were selected from the student population of the Manila Central University on the basis of the following criteria: (1) natural-born ethnic Filipino, traced up to their great-grandparent's generation; (2) good facial aesthetics; (3) Angle Class I occlusion with no crowding; (4) all teeth present (third molars may or may not be present); and (5) no previous history of orthodontic treatment. Clinical examinations and interviews were conducted to ensure that the established criteria were observed properly. The German subjects, 78 men and 123 women, were selected from Hamburg and Munich on the basis of the same criteria. Each lateral headfilm was traced and digitized, and differences between the cephalometric measurements of the two groups were compared using the Student's t-test and cephalometric superimpositions. Significant differences between the two groups were seen predominantly in the lower third of the face. The Filipinos showed more posteriorly inclined apical bases and a less prominent chin. Dentally, they exhibited a bimaxillary dental protrusion resulting in an acute dental pattern and a convexity of the soft tissue profile. These findings suggest that ethnic differences in facial traits exist and awareness of the dentofacial pattern of each ethnic group will ensure better success of treatment in establishing optimal facial harmony.

Adult↗