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Biomedical subjects

G Siciliani

Publications and source records attributed to G Siciliani.

18 recordsLinked to original sources
PubMed1999

Histomorphometric study of bone reactions during orthodontic tooth movement in rats.

The biological response to orthodontic tooth movement has generally focused on reactions within the periodontal ligament (PDL), whereas less attention has been paid to the behavior of neighboring bone. The purpose of the study was to describe the influence of orthodontic force on bone surrounding the displaced tooth and the adjacent, untreated teeth. Bone changes in relation to treatment time and different sites were investigated. A mesial tipping of the left maxillary first molar was obtained from 54 adult male Wistar rats. Oxytetracycline was injected subcutaneously 48 h before killing, which took place after 4, 7, or 14 days. The maxilla was fixed in paraformaldehyde and embedded undecalcified in methylmethacrylate. A set of thick horizontal sections was taken from the cervical, intermediate, and apical levels of the roots. The sections were microradiographed and analyzed microscopically under bright-field and fluorescent illumination. Bone fraction and PDL width was measured using a Zeiss Videoplan device equipped with an overlay system. New bone formation was detected by oxytetracycline labels. The analysis showed a consistent, significant decrease of the alveolar bone fraction around both displaced and adjacent teeth at all treatment times. Apposition, indicated by the tetracycline uptake, was found on the periosteal side of the treated hemimaxilla and, after 14 days, also on the surface toward which the tooth was moving and around the adjacent teeth. These results suggest that a time rather than a space relationship exists between bone resorption and formation and that the whole hemimaxilla reacts to the mechanical challenge, resembling the regional acceleratory phenomenon (RAP) observed in other circumstances.

Adaptation, Physiological↗
PubMed1996

Effects of continuous and intermittent forces on human fibroblasts in vitro.

Orthodontics is based upon the cellular response to biomechanical forces. However, little is known about the way cells respond to such forces. An experimental model has been designed to study the morphological and metabolic behaviour of human cells, subjected to cyclical or static mechanical loads. The model involves attaching human fibroblasts to silicone collagen-coated membranes, which are subjected to either continuous of cyclical stretching by a motor coupled with a movable supporting frame. The effect of continuous or cyclical stretching on the secretion of collagenase, an enzyme thought to play an important role in the process of tooth movement, was measured. Cyclical stretching of fibroblasts over a 4-day period, approximately doubled collagenase production as compared with the control. Continuous stretching, on the other hand, was only 50 per cent as effective in enhancing enzyme release. In contrast, the secretion of the collagenase inhibitor was unaffected by either form of mechanical deformation. To understand the effect of cyclical forces further, a morphological study using humane fibroblasts was performed. It was found that stretching or compression delivered an immediate and proportional deformation of the cells. After 10-15 minutes the morphology of cells readapted to the new mechanical environment, causing a loss of the biological activation. This suggest that a new mechanical stimulus is necessary to induce a new biological reaction.

Biomechanical Phenomena↗
PubMed1996

The lingual distalizer system.

Class II molar relationships can be corrected by several methods. In previous systems, orthodontic forces have been applied to crowns and distal movement of the first molar has mainly been by tipping and a rotation of the crowns. A new Lingual Distalizer (LD) has recently been developed to distalize the maxillary molars without the drawbacks of previous appliances. The lingual distalizer is relatively easy to insert, is well-tolerated, does not require patient co-operation and is aesthetic. It distalizes molars without loss of anchorage and moves them with bodily translation.

Adolescent↗
PubMed1990

[Latero-lateral teleradiography of the head. Natural "controlled" position].

The Authors give forth a method to realize a profile radiograph in natural head position. This method considers the corner between the anterior border of the auricolar arm and the Camper plane. This angle always allows to reproduce natural head position like in the first profile radiograph. The Authors call this natural position: "natural controlled head position".

Cephalometry↗
PubMedDate not supplied

[Functional anterior limits of the dentition. 2].

The Authors search in the most used cephalometric techniques the values defining superior incisor position relationship with cephalometric planes. They assess cephalometric values on 50 functionally stable patients at the end of treatment with axiographic method.

Cephalometry↗
PubMedDate not supplied

[Electromyographic response to progressive activation of functional appliances].

The Authors, according to the literature, carried out an electromyographic study on young Class II patients. Muscolar activity was studied during rest and with Frankel's functional regulator in different conditions of activation. Analysis of obtained results supports the author's idea of an individual activation of the functional appliances.

Activator Appliances↗
PubMedDate not supplied

[Functional anterior limits of the dentition].

The Authors propose a further evaluation, during diagnosis which can allow us to label the subject not only from static point of view but also from the functional one. They think that it would be very helpful to conduct a study for evaluation the eminence angle or better, the condylar guide.

Cephalometry↗
PubMedDate not supplied

[Statistical cephalometric study of the anterior cranial base].

The Authors have carried out a cephalometric and statistic study, running at right angles, searching for a reference parameter regarding the S.N. length (skulled front base) so that it can be used in the differential diagnosis of the skeleton Classes.

Adolescent↗