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Biomedical subjects

S Lozanoff

Publications and source records attributed to S Lozanoff.

At least 37 records · Page 2Linked to original sources
PubMed1997

Finite element analysis of the cranial base in subjects with Class III malocclusion.

The association between cranial base morphology and Class III malocclusion is poorly understood. This study analyses local shape- and size differences in cranial base configurations of Class I and Class III subjects, employing finite element (FEM) analysis. Seventy-three prepubertal European-American children with Class III malocclusion were compared to their counterparts with a normal, Class I molar occlusion. Lateral cephalographs were traced, checked and subdivided into age- and sex-matched groups. Thirteen points on the cranial base were identified and digitized, providing a geometrical cranial base representation. Average cranial geometries were scaled to an equivalent size and a FEM analysis, capable of depicting and quantifying local shape- and size-change, employed to highlight regionalized, morphological differences. While the anterior cranial base was more homogeneous for shape-change, significant, localized anisotropy in the posterior regions of the cranial base and around sella turcica was evident. For size-change, areas of negative allometry were located posteriorly, but dilations in the mid- and anterior cranial base also were apparent. It is concluded that morphological alterations within the petro-occipital complex accompanied by changes in the sphenoidal and ethmoidal regions induce deviation from a normal cranial base configuration to one associated with deficient orthocephalization and an appearance of Class III malocclusion.

Age Factors↗
PubMed1997

Morphometry of the cranial base in subjects with Class III malocclusion.

The significance of the cranial base in the development of Class III malocclusion remains uncertain. The purpose of this study was to determine whether the form of the cranial base differs between prepubertal Class I and Class III subjects. Lateral cephalographs of 73 children of European-American descent aged between 5 and 11 years with Class III malocclusion were compared with those of their counterparts with a normal, Class I molar occlusion. The cephalographs were traced, checked, and subdivided into seven age- and sex-matched groups. Average geometries, scaled to an equivalent size, were generated based on 13 craniofacial landmarks by means of Procrustes analysis, and these configurations were statistically tested for equivalence. Bivariate and multivariate analyses utilizing 5 linear and angular measurements were undertaken to corroborate the Procrustes analysis. Graphical analysis, utilizing thin-plate spline and finite element methods, was performed for localization of differences in cranial base morphology. Results indicated that cranial base morphology differed statistically for all age-wise comparisons. Graphical analysis revealed that the greatest differences in morphology occurred in the posterior cranial base region, which generally consisted of horizontal compression, vertical expansion, and size contraction. The sphenoidal region displayed expansion, while the anterior regions showed shearing and local increases in size. It is concluded that the shape of the cranial base differs in subjects with Class III malocclusion compared with the normal Class I configuration, due in part to deficient orthocephalization, or failure of the cranial base to flatten during development.

Aging↗
PubMed1996

Morphological deficiency in the prenatal anterior cranial base of midfacially retrognathic mice.

The role of the anterior cranial base in the establishment of midfacial retrognathia remains unclear. The purpose of this study was to determine whether morphological deficiencies occur in the developing anterior cranial base of the retrognathic Brachyrrhine (3H1 Br/+) mouse mutant shortly after overt cartilaginous differentiation and to localise any malformations. Crania from 2 groups of 3H1 Br/+ and +/+ mice, each consisting of 15 animals, were collected at gestational days 15, 17, and 19 (Theiler stages 23, 25, 27). The anterior cranial base from each specimen was subjected to computerised reconstruction and 8 homologous anatomical landmarks were digitised on each model. The landmark configurations were subjected to Procrustes analysis and significant differences between models were determined at each age. In order to localise differences between forms, average landmark configurations derived from Procrustes analysis were subjected to finite-element analysis. Two cluster models were generated based on size-change values. One cluster was located anteriorly and superiorly while the second was located posteriorly and inferiorly within the anterior cranial base. Results indicate that the size-change values for the posterior and inferior cluster increased more rapidly compared with the anterior and superior region over the age range tested. These data indicate that the midfacial retrognathia in Br/+ mice is associated with abnormal growth activity in the presphenoid component of the presumptive anterior cranial base. In addition, the deficiency is present in the presphenoid at the time of overt cartilaginous differentiation.

Animals↗
PubMed1995

Superior laryngeal nerve block: an anatomical study.

Superior laryngeal nerve anaesthesia is frequently used to facilitate endotracheal intubation in the awake patient. We have modified the transcutaneous approach to this nerve block to employ a short bevel needle. This improves tactile perception in performing the procedure thus simplifying identification of the correct depth of injection. This study was designed to determine the anatomical basis of superior laryngeal nerve anaesthesia and to estimate the success rate using our modified technique. At autopsy, 20 cadavers had nerve block performed substituting 0.02% methylene blue for local anaesthetic. Dissection was then performed to identify the anatomical structures stained by the simulated local anaesthetic. Additional dissections were performed in formalin-fixed cadavers. We found that the dye was injected into the paraglottic space bounded laterally by the thyrohyoid membrane and thyroid cartilage, medially by the laryngeal submucosa, caudad by the conus elasticus, cephalad by the hyoid bone, and anteriorly and posteriorly by the anterior and posterior thyrohyoid ligaments, respectively. The internal laryngeal nerve, the sensory branch of the superior laryngeal nerve, passed through this compartment and was heavily stained with simulated local anaesthetic. Resistance to the passage of the short bevel needle was provided by the lateral glossoepiglottic fold, not the thyrohyoid membrane as we had expected. Of 40 injections, 39 were deemed successful for a success rate of 97.5%. We conclude that this is a simple and highly successful technique for performing superior laryngeal nerve anaesthesia.

Cadaver↗
PubMed1994

Anterior cranial base morphology in mice with midfacial retrusion.

The role of the anterior cranial base in the morphogenesis of class III malocclusions remains uncertain. This study was conducted to determine whether morphologic deficiencies occur in the anterior cranial base in the Brachyrrhine (Br) mouse mutant showing severe midfacial retrusion, which is characteristic of a class III malocclusion. Crania from three groups of C3H/Hej, 3H1 Br/+, and 3H1+/+ mice, each consisting of 15 animals, were collected at 1, 3, and 5 days of age (total = 135). The anterior cranial base from each specimen was subjected to computerized reconstruction and ten landmarks were digitized from each model. The landmark configurations were compared using Procrustes analysis. Significant differences between models were determined at each age. In order to localize differences between forms, average landmark configurations derived from Procrustes analysis were subjected to finite-element analysis. Size-change values for the 3H1 Br/+ animals showed magnitudes that increased in an anteroposterior direction when compared to the 3H1 +/+ and C3H/Hej animals at all ages. The largest values were located posteriorly along the ossifying front of the presphenoid. In five of six comparisons, the size-change values separated into two distinct clusters. The posterior region of the anterior cranial base was divisible into two subclusters, one located superiorly and the other inferiorly. These data suggest that midfacial retrusion in the Br mouse may be caused, in part, by growth deficiencies in the posterior region of the anterior cranial base, particularly the presphenoidal and sphenoethmoidal regions.

Aging↗
PubMed1993

External craniofacial features, body size, and renal morphology in prenatal brachyrrhine mice.

The Brachyrrhine (Br) semidominant mouse mutant provides a useful model for studying factors responsible for midfacial hypoplasia. In order to determine early morphogenetic events responsible for midfacial hypoplasia in these mice, prenatal mutants must be differentiated from nonaffected littermates. The purpose of this study was to determine whether prenatal offspring from Br matings could be separated morphologically into groups of normal or midfacially deficient embryos. Thirty embryos resulting from Br matings were collected between day 15 and birth (Theiler stages 23-27). Qualitative observations on craniofacial morphology as well as renal morphology and histology suggested that embryos segregated into two distinct groups. External craniofacial and body measurements, collected from the embryos, as well as renal volumes, determined from computerized reconstructions of the kidneys, were subjected to quantitative analyses. A discriminant function analysis segregated the sample into two groups based primarily on midfacial length and renal volume. Bivariate regression analysis showed that midfacial length and renal volume differed significantly, and cranial length marginally so, between the two groups. The results indicate that a proportion of prenatal offspring from Br matings exhibits midfacial and renal hypoplasia and that these animals segregate completely from nonaffected embryos.

Abnormalities, Radiation-Induced↗
PubMed1993

Midfacial retrusion in adult brachyrrhine mice.

The purpose of this study was to determine quantitatively whether the Br mouse displays craniofacial size and shape patterns indicative of midfacial retrusion. Fifteen craniometric variables derived from a total of 40 male and female Br mice were compared with an equivalent number of C3H/HeJ adult mice displaying normal murine craniofacial morphology. Univariate statistical analysis showed that Br crania were significantly smaller for all measurements as compared with the C3H/HeJ specimens. Multivariate analysis revealed that the pattern of measurement covariation differed significantly between the two samples. Results indicated that the midface was significantly shorter in length relative to the calvaria in mutant mice was compared with C3H/HeJ mice. Therefore, the sagittal midfacial growth trajectory is deficient in Br mice.

Animals↗
PubMed1992

Accuracy and precision of computerized models of the anterior cranial base in young mice.

The quantitative analysis of craniofacial growth in experimental animals relies on computerized reconstructions in order to measure changes in form. The purpose of this study was to determine the validity of computerized three-dimensional models of the anterior cranial base in mice. Ten 1-day-old non-littermates were collected and the anterior cranial base was dissected free from surrounding connective tissues. Eleven measurements were recorded from these cartilages. Twenty developmentally equivalent mice were collected and fixed with either glutaraldehyde or formalin and the anterior cranial base from each specimen was subjected to computerized reconstruction. The corresponding 11 measurements were recorded from these models. Results showed that the measurements recorded from the computerized models were not significantly different from those recorded directly from the actual anterior cranial bases. Therefore, the reconstructions were considered accurate. An analysis of the coefficients of error revealed that measurements derived from the computerized models were significantly more precise than those recorded directly from the actual tissue. The computerized three-dimensional reconstruction method provides accurate and precise models of the anterior cranial base in young mice.

Animals↗
PubMed1992

Evaluation of a new periodontal curet. An in vitro study.

Removal of plaque and calculus from subgingival root surfaces is a fundamental aspect of periodontal therapy. A new type of periodontal curet (Gracey Curvette Sub-0) has been designed to better adapt to the root surfaces that may be encountered in periodontal pockets of incisor teeth. The new curet (test) was compared to a Gracey curet 1/2 (conventional) in their ability to remove deposits from the subgingival root surfaces of incisor teeth in an in vitro model. A dentiform model mounted on a dental chair was used with artificial gingiva, 6 mm pocket depths and subgingival root surfaces covered with black enamel paint. 2 groups of 12 hygienists used, on a timed basis, either the test or conventional curet on 4 of the incisor teeth and then switched to the alternate instrument for the remaining four incisors. The extent of surface material removal was determined using a computerized video routine. The test curet removed significantly (p less than 0.001) more of the surface material from all subgingival incisor root surfaces than the conventional curet (60.7% versus 46.3%). Both instruments were most effective at labial surfaces. The test curet was least effective at proximal surfaces and the conventional curet least effective at lingual surfaces. The greatest statistical difference between instruments was apparent at lingual surfaces of maxillary incisors and the least at mesial surfaces of mandibular incisors.

Alveolar Bone Loss↗
PubMed1992

An imaging routine for assessing the efficacy of instruments used for scaling and root planing.

Deposits of dental plaque or calculus are typically quantified using planimetric techniques. However, error is introduced into a quantitative analysis of plaque deposits using these methods, since they require a significant amount of human intervention. The purpose of this study is to describe and validate a computerized imaging routine which has the potential to objectively identify material on dental roots and measure the area covered by these deposits. Dentiform teeth with simulated plaque were videorecorded. A computer routine was developed based on a flood-fill algorithm which analyzed images of the dentiform teeth and determined the amount of simulated plaque on their root surfaces. Results showed that the dentiform teeth and their simulated plaque patterns are duplicated by the imaging routine in a rapid and reliable fashion. The system shows a high degree of accuracy with an average error factor of only 0.58%. As well, the system enables precise reproducibility with an average error factor of only 0.71%.

Algorithms↗
PubMed1991

Implementing Boissonnat's method for generating surface models of craniofacial cartilages.

Surface modeling of embryonic craniofacial morphology typically is accomplished using data derived from planar contours. Methods currently available for reconstructing embryonic craniofacial anatomy from contour data rely on shortest-path algorithms in order to interpolate surfaces. However, these techniques either fail or require a considerable amount of user interaction when complex surfaces are modeled since foramina and structural divisions cannot be interpolated properly. Recently, a new approach has been described by Boissonnat that constructs a polyhedral volume between sets of planar contours. Surfaces are interpolated by identifying the planes formed when the contours intersect the polyhedron. The purpose of this study is to determine whether craniofacial cartilages from embryonic mice can be reconstructed in an accurate and reliable fashion using this method. Embryonic mice were collected and processed for routine histological sectioning. Serial sections of the anterior cranial base and nasal capsule were obtained, subjected to videomicroscopy, and modeled. Reconstructions of the anterior cranial base and nasal capsule from embryonic mice were compared to the same structures in age-matched specimens that were processed with whole-mount staining procedures. The models compared well with the whole-mount preparations. In addition, the reconstruction technique accurately rendered complex surface features of the embryonic anterior cranial base and nasal capsule including foramina and structural branches.

Algorithms↗
PubMed1991

A method to prevent wrinkles in autoradiographic emulsion when staining plastic embedded sections with hematoxylin and eosin-phloxine.

A procedure was developed which prevents wrinkles in autoradiographic emulsion when sections, embedded in glycol methacrylate, are stained with hematoxylin and eosin-phloxine. Craniofacial tissues labeled with tritiated thymidine were collected and mounted on slides. Slides were dipped in emulsion, stored for one month and developed. The slides were immersed in liquefied celloidin and subsequently stained with a modified hematoxylin and eosin-phloxine procedure. Results showed that the emulsion did not wrinkle and the procedure did not effect the occurrence of labeled cells.

Animals↗
PubMed1990

Comparison between two finite-element modelling methods for measuring change in craniofacial form.

Finite-element modelling of form change is a useful morphometric technique for measuring differences between anatomical patterns. Two different finite-element algorithms currently are used. One method requires normalized coordinates as input data, while the second method uses globalized coordinates as input data. This study determines whether the two finite-element methods provide equivalent measures of three-dimensional form change when applied to the nasal septa of embryonic mice. Computer models of the nasal septa from mice of 15 and 17 days gestation were generated. Homologous landmarks were identified so that each nasal septum was represented by a tetrahedral finite-element. These elements were subjected to both finite-element modelling methods. Results show that the two algorithms use different interpolation functions and yield dissimilar intermediate results, but generate identical strain matrices as well as equivalent principal extensions, directions of form change, variables of form change, and graphical displays. Therefore, results are directly comparable from studies using either finite-element modelling method.

Animals↗
PubMed1989

Developmental morphology of the solum nasi in the mouse lemur (Microcebus murinus).

The solum nasi of Microcebus murinus is characterized by the presence of a zona annularis, continuity between the anterior transverse lamina and the paraseptal cartilage, a continuous paraseptal cartilage, a palatine cartilage and a posterior transverse lamina. It lacks a fibula reuniens and possibly a cartilage of the nasopalatine duct as well as a palatine papillary cartilage. The morphology in M. murinus closely resembles that seen in Tupaia and Galago. This affinity results from the retention of primitive traits. However, Galago is reported to lack a zona annularis, thus displaying a specialization not shared with M. murinus. Therefore, the zona annularis provides a useful trait for distinguishing between the ontogenies of M. murinus and Galago.

Animals↗
PubMed1989

A computer graphics program for measuring two- and three-dimensional form change in developing craniofacial cartilages using finite element methods.

Allometric analysis of chondrocranial growth seeks to provide objective measures of morphogenetic form change during ontogeny of the primordial skull. Linear measures, typically employed to study differential growth, become problematic at the histological level since an external referencing system is impossible to achieve for microscopic anatomies in embryos. The purpose of this paper is to describe a computer graphics program which generates spatially invariant measures of two- and three-dimensional form change using finite element methods. Anatomical form change is viewed as a continuous deformation of an initial finite element representing an anatomical unit into a second configuration. The algorithm consists of isoparametric scaling of finite elements, strain matrix formulation, and size/shape variable derivation. The routine includes four segments serving to extract nodal data, generate the strain matrix relating the two morphologies as well as deriving corresponding size/shape variables, reference the major and minor axes of form change, and provide graphic display of the anatomical geometries. Applications are provided measuring two- and three-dimensional form change in the developing craniofacial cartilages of rats subjected to treatment with the known teratogen diazo-oxo-norleucine (DON). The finite element routine provides craniofacial form change variables which are expected in light of cellular alterations induced by DON administration. Finally, computational differences between this routine and similar approaches using finite element methods for analyzing biological form change are examined.

Animals↗
PubMed1988

Surface modeling of craniofacial form in human embryos with a limited graphics terminal.

Three-dimensional morphology of the human embryo typically is visualized through computerized modeling techniques utilizing planar contours as the data base. Through this approach, tissue outlines are digitized, and contour lines are superimposed, providing a depth perspective. However, these techniques represent embryonic tissues as discontinuous surfaces and therefore ignore morphological information between sections. The purpose of this study was to develop a computerized routine for the three-dimensional surface modeling of craniofacial morphology in human embryos. Tissue outlines are digitized, thus converting contour information into x,y,z coordinate data. The three-dimensional reconstruction program BCSURF opens the data file and plots each tissue polygon. A center is determined for each contour, and this value is used to divide each polygon into four segments. Surface patches are generated by mapping each segment onto the corresponding segment of subsequent sections. A face table is constructed representing the surface patches and plane normals are generated for each patch. The normal and depth values are appended to the face table, and these measures determine the color intensity for each patch. Finally, patches are plotted providing a polygon mesh model, and each patch is filled with a dither pattern according to shading values. Three-dimensional reconstructions of the craniofacial region in Carnegie embryos (stages 15-17) are generated, and major morphological features are observed. Although bilevel shading capabilities cause discontinuous shading textures, this simple and inexpensive system can be easily upgraded for high-resolution graphics.

Computer Simulation↗
PubMed1986

Measuring histological form change with finite element methods: an application using diazo-oxo-norleucine (DON)-treated rats.

Analyses of drug-induced anatomical malformations routinely rely on linear measurements as a data base. Morphometric approaches utilizing these measures become inappropriate at the histological level at which a constant external referencing system is impossible to achieve. The purpose of this study was to quantify anatomical form change in the craniofacial region of late embryonic rats induced by a known teratogen, diazo-oxo-norleucine (DON), independent of any global referencing system. A sample of 17 untreated specimens of 17-day gestation served as the control. A second group, equivalent in number and age, received 2.0 mg DON on day 15. Homologous landmarks were identified in each specimen and craniofacial regions were partitioned with respect to these bounding nodes into nasal, oral, and mandibular elements. Form change was viewed as the continuous deformation of a reference craniofacial region from a 15-day untreated specimen into each final 17-day geometry. An interactive graphics program generated spatially invariant measures of form change through finite element methods. A local coordinate system was established for each element. A point within each region of the 15-day reference specimen was selected and the spatial relationship between this point and bounding nodes was quantified through interpolation functions. Size and shape variables were derived from a Lagrangian strain tensor, and values were compared between groups. Results showed that all three craniofacial regions were smaller in size among DON-treated specimens, but only oral and mandibular region shapes were different from controls. The finite element approach was considered superior to other histological morphometric techniques since an entire geometry was described and a visual description of form change as well as spatially invariant measures of size and shape change were derived.

Abnormalities, Drug-Induced↗