Mandibular growth rates in human fetal development.

A morphometric analysis of changing proportions in the developing mandible was undertaken in 18 human embryos and fetuses of both sexes (developmental age from 8 to 14 weeks, crown-rump length, CRL, from 34 to 110 mm), previously cleared and stained with a specific method for bone (alizarin red S). Reference points were located on the mandible, i.e. condylar process (Pcl), coronoid process (Pco), gnathion (GN), gonion (GO), superior symphyseal point (SSP), for measuring linear dimensions, i.e. Pcl-GN, Pcl-Pco, Pco-GN, GO-GN, SSP-GN. The gonial (Pcl-GO-GN) and the (Pcl-GN-Pcl) angles were also measured. All linear dimensions were correlated with the CRL by bivariate allometry (1n y = 1n a+b 1n x): they all grew with positive allometry, except GO-GN with isometry. The mandibular ramus grew relatively faster than the body, both in length and height, and the greatest growth rate was found for ramus height. The relation between mandibular shape and the craniofacial structures was investigated using scale drawings obtained from photographs of fetal skulls in lateral view. In the youngest fetuses the mandible was prognathic, then became retrognathic. During the period investigated the zygomatic process and squama of the temporal bone were in a lower and more inclined position in relation to the transverse plane passing through the zygomatic arch than in the newborn and adult. This study identifies parameters fitting changing trends in height, length and shape of the human mandible during the prenatal period (8-14 weeks); moreover, it emphasizes that the mandibular growth patterns differ significantly from those of successive development periods.

The influence of dental metal alloys on cell proliferation and fibronectin arrangement in human fibroblast cultures.

The biocompatibility of six single-phase dental metal alloys was studied by determining cell proliferation rates correlated to the arrangement of fibronectin (FN) in fibroblast cultures. Immunocytochemical methods were used to detect cell proliferation by 5-bromodeoxyuridine (BrdU) incorporation, and FN organization [i.e. diffuse in the extracellular matrix and organized in fibrils or in focal adhesions (FA)] in human fibroblast cultures. Cell proliferation rates were related to FN arrangement and in particular a higher percentage of cells in the S-phase was related to a predominance of FA. The greatest difference in behaviour compared to that of the controls was detected after 120 and 168 hr: at these times, as well as at previous ones, the alloy with the highest Au content seemed the most biocompatible among those tested, as it behaved in a very similar way to the controls. In contrast, fibroblasts exposed to the other five alloys showed different behaviours from the controls. It is assumed that a correlation exists between FN organization and the percentage of BrdU-positive cells, and that these features vary in the presence of different alloys. The observation of FN arrangement together with cell proliferation rates could be another useful tool in determining the biocompatibility of dental metal alloys.

Cell proliferation rates and fibronectin arrangement as parameters for biocompatibility evaluation of dental metal alloys in vitro.

A short-term (72-96 hours) biocompatibility evaluation in vitro of four single phase dental metal alloys was conducted by determining cell proliferation rates correlated to the organization of the extracellular matrix protein fibronectin in human fibroblast cultures. Immunocytochemical methods were performed to detect both cell proliferation rates by 5-bromodeoxyuridine (BrdU) incorporation, and fibronectin arrangement, i.e., diffuse in the extracellular matrix, organized in fibrils or in focal adhesions. We showed that cell proliferation rates were related to fibronectin expression. In particular, a higher percentage of cells in the S-phase were related to a predominance of fibronectin organized both in fibrils and in focal adhesions. The alloy with the highest Au content seemed the most biocompatible among those tested, since it behaved in a very similar manner to the controls. On the contrary, fibroblasts exposed to the alloy with the highest percentage of Ag had the most different behavior as compared to the controls. We can assume that a correlation exists between fibronectin organization and the percentage of BrdU-positive cells and that these parameters are varying with the different metal composition of the alloys. The observation of fibronectin arrangement together with cell proliferation rates could be considered a useful tool to determine the biocompatibility of these biomaterials.

In vitro evaluation of the biocompatibility of dental alloys: fibronectin expression patterns and relationships to cellular proliferation rates.

OBJECTIVE: This short-term (72- to 96-hour) in vitro study on fibroblasts evaluated the biocompatibility of 3 single-phase dental alloys by determining cellular proliferation rates and the expression of a glycoprotein, fibronectin, which is involved in cellular adhesion processes. METHOD AND MATERIALS: Flow 2002 fibroblasts were cultured together with 3 single-phase dental alloys of different composition. Proliferation rates were determined by 5-bromodeoxyuridine incorporation. Fibronectin expression was determined by indirect immunofluorescence. RESULTS: At 72 hours, cells cultured with the alloy containing the lowest amount of noble elements (gold, platinum, and palladium) and the highest amount of silver exhibited significantly less proliferation than did controls. At 96 hours, only cultures with the alloy containing the greatest amount of noble elements behaved in a way similar to controls. Fibronectin organization in fibrils and in focal adhesions was correlated to higher cellular proliferation rates. CONCLUSION: Fibronectin organization could be a useful tool to determine the biocompatibility of dental alloys. Among the noble elements, palladium by itself exhibits very good biocompatibility. These indications could be useful for practitioners in the choice of the best alloy for specific clinical applications.

The adhesion of Flow 2002 fibroblasts to titanium implant materials is influenced by different surface topographies and is related to the immunocytochemical expression of fibronectin.

Osteointegrated titanium dental implants are widely used biomaterials that have to integrate within the alveolar bone and interact with periodontal soft tissues. In this study, we investigated the immunocytochemical expression of the extra-cellular matrix (ECM) protein fibronectin (FN) and type I collagen (Coll I) in Flow 2002 fibroblast cultures spread on grade III-titanium samples with five different surface topographies and we correlated the immunocytochemical data to the adhesion capability of these cells to the above-mentioned substrates. Five different surfaces of grade III-titanium implants were at first characterized both by scanning electron microscopy (SEM) and by laser profilometry for surface roughness evaluation. After being spread on the biomaterial surfaces, the fibroblasts were left to proliferate for 72 hr and subsequently the cells underwent immunocytochemical procedures for detecting both FN and Coll I. The fibroblasts appeared more adherent to smoother titanium surfaces than to rougher ones; however, the highest cell density was detected on the roughest surface, even if it was unrelated to the highest FN expression. In the other biomaterial surfaces examined, as well as in controls, immunocytochemical FN expression correlated effectively to cell density on the examined substratum, whereas no determinant information was available regarding Coll I. It is reasonable to assume that surface roughness could be a relevant parameter influencing fibroblast adhesion to substrata; however, the evaluation of the cell density only is insufficient, and should be supported by the immunocytochemical FN expression, which could be confirmed as a useful tool in determining implant material biocompatibility. (Journal of Applied Biomaterials & Biomechanics 2004; 2: 169-76).

Biocompatibility in vitro of titanium dental implants. Immunocytochemical expression of fibronectin and extracellular matrix receptors.

BACKGROUND: Cell-substratum interactions play a peculiar role in cell proliferation, differentiation and migration. They are regulated by various glycoproteins, among which fibronectin, and by receptors connecting cells to the extracellular matrix, i.e. integrins. Therefore, the aim of this study was to correlate the proliferation rates of the human fibroblast line WI-38 cultured in presence of titanium dental implants to cell adhesion capability to substrata. METHODS: WI-38 fibroblasts were cultured in presence of four dental implants in titanium (one hydroxyapatite coated) for 48, 72 and 96 hours. Cell proliferation was evaluated by detecting 5-bromodeoxyuridine incorporation. Fibronectin organization and alpha5beta1 integrin expression were evidenced by indirect immunofluorescence. RESULTS: A correlation between fibronectin organization and cell proliferation rates was demonstrated: cultures showing fibronectin mainly organized in fibrils presented the highest cell proliferation degrees. After 96 hours, the observed decrease of the number of proliferating cells corresponded to a different fibronectin organization. In presence of the hydroxyapatite coated implant, colocalization of fibronectin and alpha5beta1 integrin was represented in focal contacts in cultures exhibiting the highest proliferation rate, while cells with the lowest proliferation one expressed alpha5beta1 integrin in point contacts. CONCLUSIONS: Evidences obtained in this work showed that both the organization of fibronectin and the expression of alpha5beta1 integrin are strictly correlated to cell proliferation rates. Therefore, these parameters could be useful for evaluating the biocompatibility of dental materials in vitro.

On the presence of a secondary cartilage in the mental symphyseal region of human embryos and fetuses.

The presence of a secondary cartilage in the mental symphyseal region was examined in this study. A double-staining method with alcian blue and alizarin red S was performed on both whole human embryos and fetuses (developmental age between 8 and 17 weeks, crown-rump length, CRL, between 37 and 124 mm) and their disjointed mandibles. Histological and histochemical techniques were applied to transverse serial sections of whole disjointed fetal heads. The ossification process observed in the mental symphysis is quite different from that of the mandibular body, whose membranous ossification is induced by the contiguous Meckel's cartilage. No evidence of any fusion of Meckel's cartilage with the symphyseal cartilage, that lies within the symphyseal space, was detected. On the basis of these findings, we suggested that the mental secondary cartilage is able to change into bone according to an endochondral ossification process. Moreover, the role of mechanical causes in the development of the mental symphysis was hypothesized.

Morphological features and measurements in a human fetus with karyotype 69, XXX: comparison with fetuses of the same CRL, without chromosomal anomalies.

A triploid fetus (karyotype 69, XXX) with crown-rump length (CRL) 94 mm, presenting micro- and retrognathia, low-set ears and crooked feet, was cleared and double-stained with alizarin red S and alcian blue for detecting the ossification patterns in the vertebral column, ribs, ischium, limbs, and face. Longitudinal measurements of some long bones in the upper (humerus, ulna, radius) and lower (femur, tibia, fibula) limb were taken. The values of both the total length (TL) and the ossified part (OL) of each long bone, as well as the OL/TL per cent ratio were considered. Reference points were located on the mandible, i.e. condylar process (Pcl), coronoid process (Pco), gnathion (GN), gonion (GO), superior symphyseal point (SSP) for measuring linear dimensions. Since the aim of this work was to assess the influence of triploidy 69, XXX the skeletal development and growth patterns, all values obtained in the examined specimen were related with those relative to a group of fetuses, without any detectable malformation and chromosomal anomalies, with a CRL mean value of 93 mm. Results evidenced that the triploid fetus presented growth restriction and that the vertebral centra ossification and the mandibular development were much delayed with the normal ossification patterns.

Lamellar and "club-shaped" corpuscular nerve endings in human gingival mucosa. A light and electron microscopic study.

A study on the presence of corpuscular nerve endings in human gingival mucosa was performed using both light and transmission electron microscopic (TEM) techniques. Both round and oval lamellar corpuscles were detected by light microscopy. They were located either subepithelially, close to the basement membrane, or within the papillae, deeply invaginated into the overlying epithelium. TEM techniques showed convoluted structures with unmyelinated fibre arborizations leading to an afferent fibre supported by the so called lamellar cells. The presence of blood vessels, collagenous fibrils, desmosome-like junctions, cytoplasmic organelles, as well as the similarity with some previously described mechanoreceptors, suggested the role of such corpuscular nerve endings in transmitting a nervous impulse induced by mechanical stimulation. Other simpler structures were also observed and named "club-shaped" corpuscles: they could support the more complex ones in responding to the strengths and the movements directly influencing the gingival mucosa.

Biocompatibility evaluation of dental metal alloys in vitro: expression of extracellular matrix molecules and its relationship to cell proliferation rates.

The biocompatibility in vitro of dental biomaterials has been widely studied, with consideration of cell viability and cell proliferation rates. In the present study we evaluated the biocompatibility in vitro of three single-phase dental metal alloys, all provided by the same manufacturer. To this aim, we considered the percentage of proliferating cells revealed by 5-bromodeoxyuridine incorporation in human fibroblast cultures in the presence of these biomaterials, performing a short time test (72 h). These data were correlated with immunocytochemical expression of four molecules of the extracellular matrix, i.e., fibronectin, type I collagen, beta(1)-integrin subunit, and chondroitin sulfate, because the capability of cells to adhere to substrata is widely related to cell proliferation rates. Alloys presenting higher amounts of noble elements were more biocompatible even when they contained significant amount of both Ag and Cu. As regards the expression of the extracellular matrix molecules, the organization level of fibronectin in fibrils was correlated with higher cell proliferation rates, whereas no difference was detected for the expression of the other antigens. On these bases, we assume that expression of fibronectin could be a useful parameter in evaluation of biocompatibility in addition to cell proliferation capability.

The presence of implant materials influences fibronectin arrangement and cell growth in fibroblast cultures.

The nature of the bone-implant interface has been much focused in investigating dental implant materials, whereas the relationship between implant and fibroblasts has received much less attention. To evaluate the biocompatibility degree of an implant material, both cell adhesion and cell growth must be tested in the presence of the implant. Four dental implant (A,B,C,D) made in titanium alloy and one of them (C) hydroxyapatite (HA)-coated in fibroblast cultures (48 and 72 h) were tested, by performing immunocytochemical techniques and then by observing fibronectin (FN) arrangement for cell adhesion and counting 5-bromodeoxyuridine (5-BrdU) to evaluate cell proliferation. Different FN arrangements were observed-i.e. organized in fibrils, or in focal adhesion plaques, as well as dispersed in the intercellular space-which varied for the different implants employed at the various culture stages. Equally, the per cent ratio of 5-BrdU positive cells was different, with a more significant increase (p < 0.001) between 48 and 72 h for implant C and the controls. It was observed that the higher percentages of 5-BrdU positive cells were in cultures where FN was organized mainly in focal adhesions, as well as 5-BrdU positive cells increased after 72 h in cultures, which after 48 h presented much FN dispersed in the intercellular space. It may be assumed that a correlation exists between FN arrangement and the percentage of 5-BrdU positive cells and that these two parameters vary in the presence of the different implants. Moreover, the HA-coated implant seems to be the most biocompatible in fibroblast cultures.