Claudio Chimenti

Friction of Orthodontic Elastomeric Ligatures with Different Dimensions

The aim of this study was to evaluate in vitro the effect of variations in the size of elastomeric ligatures on the static frictional resistance generated by orthodontic sliding mechanics under dry condition. Frictional forces generated by elastomeric ligatures treated with a lubricating material (silicone) were analyzed as well. An Instron testing machine was used to assess the static frictional forces of a 0.019 x 0.025-inch stainless steel rectangular wire that was ligated to a molar convertible tube and to three stainless steel 0.022-inch pre-adjusted brackets with elastomeric ligatures with different dimensions: small, medium, and large. The static friction produced by two prototypes of silicone-lubricated elastomeric ligatures was also measured. The small and medium elastomeric ligatures produced significantly less friction than the large ligatures. No statistically significant difference was found between small and medium ligatures. The decrease in frictional forces of small and medium modules had to be ascribed mainly to the smaller thickness of both ligatures with respect to large ligatures. The lubricated elastomeric ligatures generated significantly smaller frictional forces than nonlubricated elastomeric ligatures with different dimensions. The variation in the dimensions of the elastomeric ligatures is able to influence the static frictional resistance generated by orthodontic sliding mechanics in the buccal segments. The use of small and medium elastomeric ligatures determines a 13-17% decrease in static friction compared with large ligatures. Silicone-lubricated modules can reduce static friction by 23-34% with respect to the small and medium nonlubricated elastomeric ligatures and by 36-43% compared with nonlubricated large ligatures.

Activities of masticatory muscles in patients after orthognathic surgery

AIM To evaluate left and right masseter and anterior temporalis muscle activity in patients before and after orthognathic surgery. PATIENTS Nineteen patients were enrolled, 9 males and 10 females, aged 17-34 years. Four patients were suffering from a prognathic syndrome (skeletal class II with mandibular retrusion) and were candidates for surgical correction involving a mandibular Bilateral Sagittal Split Osteotomy (BSSO), whereas the other 15 patients showed a progenic syndrome (skeletal class III with mandibular protrusion) and were selected for bimaxillary surgery with maxillary advancement and mandibular retrusion. METHODS Electromyographic examinations were carried out on all subjects presurgically and 6-8 months postoperatively. To verify the neuromuscular equilibrium, the electromyographic activities of both the right and left masseter and anterior temporalis muscles were registered and analysed calculating: percentage overlapping coefficient (POC, index of the symmetric distribution of the muscular activity determined by the occlusion) and torque coefficient (TC, index of presence of mandibular torque). RESULTS After surgery, a trend in the improvement of POC and TC indices was found, with a reduced intragroup variability. CONCLUSION The electromyographic evaluation allowed the impact of occlusion on neuromuscular equilibrium to be quantified, and showed that improvements gained by surgical intervention are primarily due to better occlusal stability and not to biomechanical advantages.

Five-year follow-up of Le Fort I osteotomies*

The outcome of a five-year radiographic follow-up study of 150 patients with maxillo-mandibular malformations who had undergone Le Fort I osteotomy of the maxilla is reported. A superimposition technique made possible an exact evaluation of the adjustments effected. The results confirm the validity of a study conducted in 1977 and the five-year stability of the maxilla. The importance of the relationship between the Frankfort plane, occlusal plane and the osteotomy line is emphasized. In operations in which Le Fort I osteotomy of the maxilla is combined with a sagittal osteotomy of the mandible the maxilla undergoes minute displacements in the weeks following surgery, which can easily be predicted and allowed for at the planning stage. The long-term stability of the maxilla is assured.

Condylar Position Indicator and T-Scan system II in clinical evaluation of temporomandibular intracapsular disease

INTRODUCTION The pathogenesis of temporomandibular joint intracapsular disease (TMJI) is multifactorial and its diagnosis is not easy. In this work authors show two types of clinical analysis: the Condylar Position Indicator (CPI) and T-Scan 2 system. MATERIAL AND METHODS Twenty patients (mean age of 24.5 years) with TMJI problem and 10 healthy matched subjects (mean age: 25.4 years) were selected. Analysis of TMJI was performed on each patient by means of Condylar Position Indicator (CPI) and T-Scan System II tests. RESULTS Eight patients presented vertical symmetrical condylar distraction greater than healthy subjects (P-value<0.001). T-Scan showed a difference of Percentage of Force (POF) not greater than 5%. Seven patients showed sagittal shift greater than healthy subject (P-value<0.001). T-Scan records showed a difference of POF greater than 5%. Five non-healthy subjects presented sagittal, vertical, transverse shift greater than healthy subjects (P-value<0.001). T-Scan records show a difference of POF greater than 5%. CONCLUSION In this work authors present a new method of analysis. CPI indicates discrepancy of the condyle position in CO from CR and T-Scan allows the operator to study all teeth contacts and occlusal forces taking place during dynamic jaw movement.

Effects of 1,4-butanediol dimethacrylate and urethane dimethacrylate on HL-60 cell metabolism.

The polymerization of methacrylic monomers present in dental composite resins never reaches completion and therefore the leakage of residual monomers into the oral cavity and into biological fluids can cause local and systemic adverse effects. This work was carried out to study the in vitro biochemical interactions of urethane dimethacrylate and 1,4-butanediol dimethacrylate monomers with HL-60 cells, a cell line assumed as an experimental model for simulating granulocyte behaviour. Our main finding was that both monomers induce cell differentiation at toxic concentrations and that cytotoxicity seems to be caused by alterations of glucose metabolism arising from mitochondrial dysfunction rather than from oxidative stress, which could not be altogether verified under our experimental conditions. Our study could be considered as a useful approach to investigate the biochemical mechanisms that contribute to the cytotoxicity of methacrylate compounds and it underlines the importance of assessing such parameters for testing biocompatibility in order to promote the development of better and safer dental materials.

Saliva analysis by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) in orthodontic treatment: first pilot study.

OBJECTIVE SELDI-TOF-MS (Surface-Enhanced Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry) allows the generation of an accurate protein profile from minimal amounts of biological samples and may executes proteomic profile of saliva. The aim of this work is to compare the proteomic profile of saliva of patients in orthodontic treatment to the beginning of treatment and after three months by using the surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) technology. MATERIALS AND METHODS Saliva was collected from 14 patients, between the 11 and 17 years, to the beginning of the orthodontic treatment and after three months. Specimens were centrifuged (10 min, 13000 x g); the Q10 ProteinChips were prepared according to the manufacturers instructions and were loaded with the supernatants. A saturated solution of sinapinic acid was used as energy-absorbing matrix. The analysis was performed in a m/z range from 2500 to 25000 Da, and the proteomic profiles were compared by a specific data analysis software. Saliva (5 mL) was collected by spitting directly into a clean 15 mL conical tube. The samples were then aliquotted and stored at -80°C until use. RESULTS Profile of saliva of patients before orthodontic treatment present a number of peaks different respect profile of saliva after three months of treatment. The average intensities of peaks at m/z 3372, 5232, 4045 and 10128 were significantly higher after three months then at beginning of treatment in the same patients and among these one. The Roc Plot has demonstrated high sensitivity and specificity. CONCLUSIONS Many differences were noted in salivary proteomic profile obtained using the SELDI-TOF-MS technology in patients in orthodontic treatment to beginning and after three months. These data suggest that the proteomic analysis of saliva is a promising new tool for a non-invasive study of oral mucosa and bone changes.

Catecholaminergic System of Invertebrates: Comparative and Evolutionary Aspects in Comparison With the Octopaminergic System.

In this review we examined the catecholaminergic system of invertebrates, starting from protists and getting to chordates. Different techniques used by numerous researchers revealed, in most examined phyla, the presence of catecholamines dopamine, noradrenaline, and adrenaline or of the enzymes involved in their synthesis. The catecholamines are generally linked to the nervous system and they can act as neurotransmitters, neuromodulators, and hormones; moreover they play a very important role as regards the response to a large number of stress situations. Nevertheless, in some invertebrate phyla belonging to Protostoma, the monoamine octopamine is the main biogenic amine. The presence of catecholamines in some protists suggests a role as intracellular or interorganismal signaling molecules and an ancient origin of their synthetic pathways. The catecholamines appear also involved in the regulation of bioluminescence and in the control of larval development and metamorphosis in some marine invertebrate phyla.

Arsenic-contaminated freshwater: assessing arsenate and arsenite toxicity and low-dose genotoxicity in Gammarus elvirae (Crustacea; Amphipoda)

Arsenic (As) contamination of freshwater is largely due to geogenic processes, but As is also released into the environment because of improper anthropic activities. The European regulatory limits in drinking water are of 10 μg L−1 As. However, knowledge of the genotoxic effects induced by low doses of As in freshwater environments is still scanty. This study was designed to investigate arsenate (As(V)) and arsenite (As(III)) toxicity and low-dose genotoxicity in Gammarus elvirae, which has proved to be a useful organism for genotoxicity assays in freshwater. As(V) and As(III) toxicity was assessed on the basis of the median lethal concentration, LC(50), while estimates of DNA damage were based on the Comet assay. The G. elvirae LC (50–240 h) value we calculated was 1.55 mg L−1 for As(V) and 1.72 mg L−1 for As(III). Arsenic exposure (240 h) at 5, 10, and 50 µg L−1 of As in assays with either arsenate or arsenite-induced DNA damage in hemocytes of G. elvirae in a concentration-dependent manner. Our study provides a basis for future genotoxic research on exposure to freshwater that contains low levels of arsenic.

Effect of methacrylic monomers on phagocytes reactive oxygen species: a possible BDDMA modulating action

In the last years the studies regarding the biocompatibility of dental materials investigate, in addition to the classic cytotoxic tests, the interactions between the materials and the host cells to better explain the causes of the adverse effects observed sometimes in the clinical practice. In the present study the ability of diurethane dimethacrylate (DUDMA) and 1,4-butanediol dimethacrylate (BDDMA) methacrylic monomers present in dental composite resins to alter the functionality of peripheral blood monocytes (PBMs) and polymorphonucleate cells (PMNs) was examined. These cells are involve in the biological response to materials and in the host ability to respond to bacteria. The results obtained suggest that the examined methacrylates induce a relevant decrease of PBMs oxidative burst whereas the basal ROS production is only slightly decreased. In PMNs DUDMA induces a decrease of both basal and stimulated ROS production. BDDMA, on the contrary, it does not alter total oxidative burst in presence of stimulus while induces a statistically significant decrease of basal ROS production. Moreover this monomer alters the reaction kinetics of stimulated ROS production. The reported finding seems to indicate that this molecule could be able to stabilize PMNs in resting state and maximize their stimulated activity.

Maxillary canine–first premolar bilateral transposition in a Class III patient: A case report

Tooth transposition is a rare dental anomaly that often represents a challenge for the clinician. The case of a girl with skeletal Class III malocclusion and concomitant maxillary canine-first premolar bilateral transposition, followed from 7 to 17 years of age, is presented. After a first phase of treatment aimed at resolving the Class III malocclusion, the transposition was maintained and the case finalized with a multibracket appliance.