Biomedical subjects

P Bracco

Publications and source records attributed to P Bracco.

At least 19 recordsLinked to original sources

PubMed2005

Reproducibility of surface EMG variables in isometric sub-maximal contractions of jaw elevator muscles.

The aims of this study were: (1) to develop and assess reproducibility of a new method for measuring masticatory force in the intercuspal position; (2) to test the reproducibility of surface EMG signal amplitude and spectral variables in constant force contractions of jaw elevator muscles and its dependency on inter-electrode distance. The study was performed on the masseter and temporalis anterior muscles of both sides of nine healthy volunteers. An intraoral compressive-force sensor was used to measure maximal voluntary contraction forces in the intercuspal position and to provide a visual feedback on sub-maximal forces to the subject. Three experimental sessions were performed in three days. In each session, three isometric contractions at 80% of the maximal force were sustained by the subjects for 30s. The intra-class correlation coefficient (ICC) of the maximal force measure was 71.9%. ICC of average rectified value and mean power spectral frequency of the EMG signal increased with inter-electrode distance, with values larger than 70% with 30 mm inter-electrode distance. It was concluded that surface EMG variables measured in isometric contractions of the jaw elevator muscles with the proposed force recording system show good reproducibility for clinical applications when a 30 mm inter-electrode distance is considered.

Adult↗

PubMed2005

Primary and secondary closure of the surgical wound after removal of impacted mandibular third molars: a comparative study.

Primary and secondary closure techniques after removal of impacted third molars were compared in terms of post-operative pain and swelling. Two hundred patients with impacted third molars were randomly divided into two groups of 100. Panoramic radiographs were taken to assess degree of eruption and angulation of third molars. Teeth were extracted, and in Group 1 the socket was closed by hermetically suturing the flap. In Group 2 a 5-6 mm wedge of mucosa adjacent to the second molar was removed to obtain secondary healing. Swelling and pain were evaluated for 7 days after surgery with the VAS scale. The statistical analysis (*analysis of variance for repeated measures, P < 0.05) showed that pain was greater in Group 1, although it decreased over time similarly in the two groups (P = 0.081, F(6,198) = 3.073*). Swelling was significantly worse in Group 1 (P < 0.001, F(6,198) = 44.30*). In Group 1, dehiscence of the mucosa was present in 33% of patients at day 7, and 2% showed signs of re-infection with suppurative alveolitis at 30 days. Pain and swelling were less severe with secondary healing than with primary healing.

Adult↗

PubMed2005

Surface EMG of jaw elevator muscles: effect of electrode location and inter-electrode distance.

This study addresses methodological issues on surface electromyographic (EMG) signal recording from jaw elevator muscles. The aims were (i) to investigate the sensitivity to electrode displacements of amplitude and spectral surface EMG variables, (ii) to analyse if this sensitivity is affected by the inter-electrode distance of the bipolar recording, and (iii) to investigate the effect of inter-electrode distance on the estimated amplitude and spectral EMG variables. The superficial masseter and anterior temporalis muscles of 13 subjects were investigated by means of a linear electrode array. The percentage difference in EMG variable estimates from signals detected at different locations over the muscle was larger than 100% of the estimated value. Increasing the inter-electrode distance resulted in a significant reduction of the estimation variability because of electrode displacement. A criterion for electrode placement selection is suggested, with which the sensitivity of EMG variables to small electrode displacements was of the order of 2% for spectral and 6% for amplitude variables. Finally, spectral and, in particular, amplitude EMG variables were very sensitive to inter-electrode distance, which thus should be fixed when subjects or muscles are compared in the same or different experimental conditions.

Adult↗

PubMed2005

Non-invasive assessment of motor unit anatomy in jaw-elevator muscles.

The estimation of fibre length in jaw-elevator muscles is important for modelling studies and clinical applications. The objective of this study was to identify, from multi-channel surface EMG recordings, the main innervation zone(s) of the superficial masseter and anterior temporalis muscles, and to estimate the fibre length of these muscles. Surface EMG signals were collected from 13 subjects with a 16-electrode linear array. The innervation zones of the masseter and anterior temporalis were identified and their variability intra- and inter-subject outlined. More than one main innervation zone location was identified in the masseter of all subjects and in the temporalis anterior of 12 subjects. Average estimated fibre lengths, for the right (left) side, were (mean+/-SD) 27.3+/-2.4 mm (27.0+/-1.7 mm) and 25.9+/-2.3 mm (26.6+/-1.6 mm), for the superficial masseter and temporalis anterior muscle, respectively. The range of innervation zone locations was up to approximately 50% of the fibre length, both within and between subjects. Fibre length estimates well matched with published data on cadavers. It was concluded that multi-channel surface EMG provides important and reliable information on the anatomy of single motor units in jaw-elevator muscles.

Adult↗

PubMed2005

Surface EMG of jaw-elevator muscles and chewing pattern in complete denture wearers.

The aim of this study was to investigate the adaptation process of masticatory patterns to a new complete denture in edentulous subjects. For this purpose, muscle activity and kinematic parameters of the chewing pattern were simultaneously assessed in seven patients with complete maxillary and mandibular denture. The patients were analysed (i) with the old denture, (ii) with the new denture at the delivery, (iii) after 1 month and (iv) after 3 months from the delivery of the new denture. Surface electromyographic (EMG) signals were recorded from the masseter and temporalis anterior muscles of both sides and jaw movements were tracked measuring the motion of a tiny magnet attached at the lower inter-incisor point. The subjects were asked to chew a bolus on the right and left side. At the delivery of the new denture, peak EMG amplitude of the masseter of the side of the bolus was lower than with the old denture and the masseters of the two sides showed the same intensity of EMG activity, contrary to the case with the old denture. EMG amplitude and asymmetry of the two masseter activities returned as with the old denture in 3 months. The EMG activity in the temporalis anterior was larger with the old denture than in the other conditions. The chewing cycle width and lateral excursion decreased at the delivery of the new denture and recovered after 3 months.

Adaptation, Physiological↗

PubMed2005

Electromyographic evaluation of neuromuscular co-ordination during chewing in a subject with organic occlusion.

The neuromuscular co-ordination of the anterior masseter and temporal muscles during chewing has been studied. The subject analysed was 24 years old female with organic occlusion, molar and canine class 1, with 2 mm overbite and overjet, frontal disocclusion and canine protection, with no cranio-mandibular disorders. Masticatory cycles and electromyographic activity were recorded with a K6 I kinesiograph (Myotronics Inc., Seattle, WA, USA). The chewing cycles were recorded with a soft bolus and a hard bolus, on 3 consecutive days. Electromyographic analysis during masticatory cycles showed that electromyographic activity was higher in the masseter muscle homolateral to the chewing side than in the contralateral muscle, whereas the anterior temporal muscles achieved similar voltages. When chewing the hard bolus, versus the soft bolus, activity in the contralateral masseter muscle increased to a greater extent than in the homolateral masseter muscle. The results were analogous at all 3 recordings. When chewing, the subject showed good muscle co-ordination, which was constant over the 3 recordings made on 3 consecutive days. Increased activity of the contralateral masseter muscle when chewing the hard versus the soft bolus indicates the stomatognathic system's capability to adapt to load and its neuromuscular equilibrium.

Adult↗

PubMed2004

Comparison of polypropylene and polyethylene terephthalate (Dacron) meshes for abdominal wall hernia repair: a chemical and morphological study.

For the first time, by scanning electron microscopy (SEM), polypropylene (PP) excised meshes (ethylene oxide sterilized) for abdominal wall hernia repair have been shown to be greatly damaged physically, independently of the implantation time, while the polyethylene terephthalate (PET), or Dacron, ones (gamma radiation sterilized), did not undergo alterations due to the sterilization process and were not damaged, even after long implantation periods. Fourier-Transform Infrared Spectroscopy (FTIR) study of PP and PET excised meshes, as well as of their extracts with cyclohexane, has shown the presence of species, such as squalene, palmitic and stearic acid, in some cases, cholesterol, transferred from the surrounding tissues to the polymer during the implantation period. In the case of PP meshes, these small organic molecules would reduce physical and mechanical properties of the material. A hypothesis is presented to account for the better behavior (not in the clinical sense) of PET meshes.

Adult↗

PubMed2004

Effects of different jaw relations on postural stability in human subjects.

Authors investigated the effects of different jaws relations on body posture in a sample of 95 subjects. All subjects underwent a posturometric and stabilometric analysis using a computerized footboard. Tests were performed in three mandibular positions: centric occlusion, rest position and myocentric position, respectively determined by teeth engagement, joints position, and muscles contraction. All subjects showed variations of body posture in the different mandibular positions. Statistical analysis (analysis of variance for repeated measures) confirmed that postural variations in different jaws relations were significant: in particular, the SKN multiple comparison test showed that myocentric position improved postural balance on frontal plane with respect to the other jaw positions considered.

Analysis of Variance↗

PubMed2004

The induction of MMP-9 release from granulocytes by vitamin E in UHMWPE.

Ultra-high molecular weight polyethylene (UHMWPE) is a biopolymer widely used in orthopaedic implants and its oxidation is considered as major responsible for inflammation and the prosthesis failure. We have studied the effect on the activation of resting human granulocytes of the addition of Vitamin E (Vit.E, alpha-tocopherol), a natural biological antioxidant and antiinflammatory agent, to UHMWPE. We have measured changes in granulocytes morphology and respiratory burst by flow cytometry using Dihydrorhodamine 123 and matrix metalloproteinase 9 (MMP-9, gelatinase B) release and activity in the growth medium using substrate zymography following contact (60 min at 37 degrees C) with cell grade polystyrene (PS), normal UHMWPE (PE) and Vit.E added UHMWPE (PE Vit.E). FTIR analyses showed that the surfaces of PE and PE-Vit.E were not significantly different. PS, PE and PE Vit.E did not alter granulocytes morphology and respiratory burst as showed by the mean fluorescence emitted (PS=12.0+/-0.1, PE=13.0+/-0.4, PE Vit.E=14.5+/-0.1). PE Vit.E was able to increase MMP-9 release compared to PS and normal PE (215+/-16% of the control, p<0.001). The PE Vit.E-induced MMP-9 release was abolished by okadaic acid (0.5 nM), suggesting a direct role of Vit.E in the phenomenon.

Adult↗

PubMed2004

Effects of a functional appliance on masticatory muscles of young adults suffering from muscle-related temporomandibular disorders.

The aim of this study was to investigate the effects of an original orthodontic functional appliance [function generating bite for deep bite correction (FGB-D)] on masticatory muscle activity in subjects suffering from muscle-related temporomandibular disorders (TMD). Electromyographic (EMG) analysis was performed on 33 young adults (nine men, 24 women) to evaluate the contractile symmetry of the right and left masseter and anterior temporalis muscles. The subjects were divided into three groups: a muscle-related TMD group requiring orthodontic treatment for deep bite correction (three men, eight women) and treated with FGB-D; a muscle-related TMD group not requiring orthodontic treatment (three men, eight women) and treated with a Michigan occlusal splint; and a TMD-free group (three men, eight women) as a control group. Records were made by surface EMG of maximum voluntary teeth clenching, with and without the functional appliance or occlusal splint in place, before and after 12 months of therapy. A torque index was derived from the surface EMG recordings to estimate lateral displacement of the mandible. The results show that the FGB-D corrects the torque index and thus the lateral displacement of the mandible.

Adult↗

PubMed2003

Ultra-high molecular weight polyethylene oxidation reduces metalloproteinase 2 secretion in human osteoblast-like cells in vitro: a mechanism of modulation of extracellular matrix.

Ultra-high molecular weight polyethylene (UHMWPE) sterilization with gamma rays induced high oxidation levels both on the surface and in the bulk that alter its structure and mechanical properties. The oxidation process of gamma-radiated UHMWPE induces a reduction of molecular weight and, consequently, a less abrasive resistance that has been related, among others, to the failure of UHMWPE in vivo. To explain the role of cells in such events, human osteoblast-like cells were seeded onto UHMWPE and oxidized UHMWPE discs. Cellular viability and morphology were evaluated along with matrix metalloproteinases (MMPs) production and activity. Oxidized UHMWPE did not induce any significant cytotoxic effects as observed by lactate dehydrogenase activity compared to the nonoxidized form; no changes in the cell morphology after 4 and 8 days proliferation were observed. In growth medium metalloproteinase 2 (gelatinase-A, MMP-2) was produced and released by osteoblast-like cells. We observed that cells grown onto oxidized UHMWPE discs decreased the release and activity of MMP-2 after 4 and 8 days culture compared to cells grown on control and non-oxidized UHMWPE discs; metalloproteinase 9 (gelatinase-B, MMP-9) release was not significantly influenced. The absence of cytotoxic and morphological effects in the presence of a down-regulation of MMP-2 release and activity suggest that oxidized polyethylene surfaces may modulate matrix remodeling and, consequently, bone formation.

Biocompatible Materials↗

PubMed2003

In vitro evaluation of the inflammatory activity of ultra-high molecular weight polyethylene.

To understand the inflammatory potential of oxidised ultra high molecular weight polyethylene (ox-UHMWPE) compared with the virgin one (UHMWPE), we analysed in vitro the predisposition of their interaction with plasma proteins and cells involved in the inflammatory response. The adsorption on the surface of the two materials of adhesion proteins (Fibronectin and Albumin), and pro-inflammatory proteins (IgG and IgA) have been studied. Moreover, we have evaluated the materials effect on complement activation and on macrophages and monocytes-neutrophils behaviour. The two UHMWPE chemical forms adsorbed all the proteins studied; the only difference was in complement activation. Enzyme immunoassay results evidenced higher levels of factor Bb and iC3b in plasma after the contact with the oxidised form. Physico-chemical properties of the oxidised UHMWPE affected the attachment of the cells as demonstrated by macrophages adhesion experiments. UHMWPE favoured only a limited peritoneal macrophages (PMs) spreading (round-shaped cells); the cell spreading and presence of microvilli on the cell membranes was evident in the case of the oxidised form, suggesting the activation of these cells on this chemical form. Ox-UHMWPE evidenced a statistically significative increase in chemiluminescence values respect to human unstimulated peripheral blood mononuclear cells, an index of increased cell release of reactive oxygen metabolites. In conclusion, UHMWPE oxidative degradation with its chemical modification induces monocytes-neutrophils chemiluminescence activation and PMs morphology changes correlated with macrophage activation, data consistent with the complement activation results obtained in this study; such modifications, along with changes in mechanical properties, are related to implant failure.

Adsorption↗

PubMed2002

Oxidation of orthopaedic UHMWPE.

Retrieved EtO sterilised acetabular cups usually show much less degradation than gamma-ray sterilised cups. Some of our retrieved EtO sterilised cups did, however, reveal unexpected bulk oxidation. It was observed that this oxidation was always accompanied by whitening of the material. This whitening was found to be due to a break-up of the compression moulded material into its original particles. It was noticed that there was no oxidation in all parts, where the break-up and whitening appeared. The oxidation did, however, occur exclusively in the parts where there was a badly consolidated material. Upon examining shelf aged, unsterilised samples, it was found that the degradation was also present here. This shows that the observed phenomenon is not due to the service in vivo and that it must originate from the processing step. Just as for the retrieved samples, the shelf aged cups only showed oxidation in the bulk and not at the surface. It was concluded that the material used for the cups had been badly fused together during the compression moulding and that the machining had created a bad stress situation in the cups leading to a break-up of the particles. The mechanism that initiates the oxidation is not known, but it is believed that the distribution depends on how the internal stresses have acted to break up the structure. In the areas where the particles have been separated, there is probably a higher availability of oxygen than what is normally observed in UHMWPE.

Biocompatible Materials↗

PubMed2002

Cytotoxicity and MMP-9 activation induced in human mononuclear cells by UHMWPE oxidation.

Ultra high molecular weight polyethylene (UHMWPE) used in orthopedic prosthesis can be oxidized during sterilization processes such as gamma-ray irradiation. Oxidation alters UHMWPE structure and mechanical properties and it has been suggested that this alteration is the first step in the loosening process. Direct effects of UHMWPE oxidation on the cellular and tissue response to the implant have not been previously investigated. We used heat-oxidized UHMWPE, whose oxidative state is comparable to the one induced in gamma-ray irradiated polymer. in order to observe the peripheral blood mononuclear cells (PBMCs) behavior after 24 and 48 h exposure to the oxidized and non-oxidized polymers. Flow cytometric analysis showed a cytotoxic effect of oxidized UHMWPE after 48 h compared with the control samples. Moreover, gelatin zymography of PBMCs conditioned media showed a strong increase in MMP-9 (gelatinase B) release and activation in oxidized UHMWPE samples. This first evidence of a direct effect of the UHMWPE oxidative status on the cellular behavior suggests that oxidation alters not only the UHMWPE physical-mechanical properties. but it can also be responsible for altered tissue response.

Adult↗

PubMed2001

Analysis of products diffused into UHMWPE prosthetic components in vivo.

Ten UHMWPE hip inserts, five ethylene oxide and five gamma-ray sterilised in air, were retrieved during surgical revision after aseptic failure. Time in situ varied from 6 to 23 years. First implant was carried out for degenerative arthritis in all cases. The retrieved inserts were cut into two parts perpendicular to the articulate surface and a series of 150 microm thick slices were obtained from the cross-section. These were studied by FTIR microscopy and the absorbed products were extracted with cyclohexane for identification by GC/MS and Py/GC/MS. All retrieved UHMWPE components, independent of the sterilisation method, showed species adsorbed on the surface, which were mainly synovial liquid protein components. In addition, species such as cholesterol, fatty esters of cholesterol and squalene, also originating from synovial liquid, were found in the bulk. The concentration of the different species varies depending on the individual patient.

Diffusion↗

PubMed2001

A chemical analysis of the clogging process of polymeric biliary endoprostheses.

Insertion of polymeric biliary endoprostheses is widely used as a method of palliation of malignant strictures of the biliary tree. Despite the success of this technique, clogging of the stent in a few months is still an existing problem. The aim of the present study has been to investigate the causes of the obstruction, considering both the stent material and the composition of the obstructing deposit. 16 ready-to-implant and 33 occluded retrieved prostheses were analysed by ATR-FTIR spectroscopy. The clogging sludge was recovered and studied by FTIR spectroscopy and pyrolysis derivatisation/gas chromatography/mass spectrometry (Py/GC/MS). The results of the analyses showed that the deposit was mainly formed by proteins, bilirubin, calcium palmitate and bilirubinate, cholesterol and its fatty acids salts. It was found that approximately 50% of the examined ready-to-implant samples were made of ethylene-vinylacetate copolymer (EVA) instead of polyethylene (PE), as was stated in the producer declaration. Moreover, 94% of the retrieved samples were found to be made of EVA indicating that this material is less suitable than PE for this application. All retrieved PE and EVA stents showed a protein-like black layer strongly absorbed on the surface.

Biliary Tract↗

PubMed2001

Evaluation of the utility of cephalometric parameters in constructing complete denture. Part I: placement of posterior teeth.

Various types of parameters, including cephalometric ones, have been used in the construction of complete denture. This study aimed to evaluate the utility of cephalometric parameters for this purpose. The position of the posterior teeth in a group of 42 edentulous patients, successfully rehabilitated with complete denture according to clinical parameters, was evaluated by cephalometrics. The following were determined: vertical dimension of occlusion (VDO); orientation of the occlusal plane; and subdivision of the denture space. The cephalometric parameters do not correspond to the clinical positioning of the posterior teeth in successful rehabilitation with complete denture.

Aged↗

PubMed1998

Observations on the correlation between posture and jaw position: a pilot study.

The aim of this pilot study was twofold. The first was to show a method for having an objective and dynamic analysis of body posture, evaluating weight distribution and its connections with different mandibular positions. The second was to verify if a neuromuscularly stimulated occlusal position, called myocentric occlusal position, is associated with a positive or negative postural charge. For the second aim a group of 20 subjects (including both males and females), was chosen. Posture of each subject was analyzed in three different conditions: centric occlusion, rest position and myocentric position. To evaluate the dynamic of posture a platform capable of measuring the weight on the feet supporting points and the related variations during time of observation and the swinging of body barycenter was used. The data showed that there is an improvement in the position of the barycenter from the centric occlusion to the myocentric position. Such an improvement can't be observed from the intercuspal position to the rest position. The results of this pilot study are discussed.

Adult↗