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Biomedical subjects

L Levrini

Publications and source records attributed to L Levrini.

7 recordsLinked to original sources
PubMed2006

Nickel ions release in patients with fixed orthodontic appliances.

AIM: The extent to which orthodontic appliances can cause contact allergies due to nickel release is a controversial matter. Since the data provided by literature are contrasting, the Authors think that it is important to analyse nickel ions released in organic tissues by means of a plasma spectrometer. METHODS: About 100 intact hairs were taken from 15 patients wearing fixed orthodontic appliances. The hairs had been washed 12 to 24 h before, in order to limit environmental contamination. The same procedure was carried out on a control group corresponding in sex, age and abode. The samples of hair were taken from at least 3 different scalp sites: frontal, vertex and occipital areas. RESULTS: According to the spectrophotometric analysis of the hair, there were no differences in nickel concentrations between the test group (0.50 mg/g on average) and control group (0.64 mg/g) (*P<0.005). The mean value was reduced even further if minimum and maximum values were excluded (test group 0.46 mg/g, control group 0.52 mg/g). Even though there was a slight difference (0.14 mg/g), it showed that more nickel concentration was found in the control sample (without orthodontic appliances) to a maximum of 2.20 mg/g. This suggests that environmental contamination, in particular diet, has an influence on ion concentration. Other studies also confirm that gut absorption of nickel released in the mouth by orthodontic appliances is much lower than the absorption of nickel release through diet. CONCLUSIONS: It can be assumed that orthodontic appliances do not release significant values of nickel to be a risk factor to the patient's health.

Adolescent↗
PubMed2003

Scanning electron microscopy evaluation of the link between a new dentinal desensitizer and dentine.

AIM: The purpose of this study was to evaluate the interaction of a novel dentinal desensitizer Twin Pro with enamel-dentinal adhesive preparations or filling materials and dentine using scanning electron microscopy (SEM) technology. METHODS: Black's I class cavities were drilled extracted molar teeth free of caries or fissures, and the cavities disinfected. The specimens were divided into 4 groups of 2 teeth each treated as follows: Group A: Twin Pro, fluid (Tetric-Flow Vivadent) and micro-hybrid (Tetric-Ceram Vivadent) composites placed on the etched (Liner Bond 2V Clearfil) cavities. Group B: Twin Pro, PQ1-Ultradent loaded Primer-Bonding plus fluid and micro-hybrid composites applied to the acid-etched (37% orthophosphoric acid) cavities. Group C: Twin Pro plus Silver amalgam alloy (Phasealloy- Sybram Kerr). Group D (control group): self-etching primer plus fluid and micro-hybrid composite. Specimens were investigated by SEM. RESULTS: The results obtained in all groups show that the application of Twin Pro does not alter the adhesiveness of the restorative composite materials to the dental wall. In fact the desensitizer and the adhesive layers are indistinguishable at SEM observation, and well adherent to the dentinal surface of the cavities. CONCLUSION: The results of SEM investigations show that Twin Pro does not decrease the adhesion of restorative materials to the tooth surface, as it establishes an efficient interconnection with the different materials used, and it forms a uniform layer covering and occluding dentine tubules, and this might constitute an efficacious sealing of dentinal tubules which possibly contribute to decrease dentinal sensitivity to environmental nociceptive stimuli.

Acrylic Resins↗
PubMed1999

Active mandibular protrusion in the rational treatment of skeletal Class II malocclusions.

BACKGROUND: Aim of the present study is to assess the ideal mandibular protrusion exercises, which should always be associated with functional treatment of skeletal Class II malocclusions, characterized by mandibular hypoplasia. METHODS: The study was carried out on a sample including 8 growing subjects (mean age 10.6 years +/- 0.6), similar in age and biotypology (mandibular hypoplasia; normodivergent growth pattern). The electromyography (EMG) activity of the superficial bundle of the masseter (considered as an accessory protrusive muscle) was bilaterally recorded at rest and, during voluntary contraction, at different degrees of protrusion (minimum, medium, maximum), condition dynamically analyzed at various times of contraction (initial, 5, 10, 30 seconds). The mean values of the recruitment pattern during the whole contraction, the number of turns/sec and the ratio turns/mean amplitude were evaluated. RESULTS: The data obtained by means of a precise electromyographic analysis suggest that the ideal exercise for an active mandibular protrusion should be a medium degree contraction lasting 10 seconds. These results are consistent with the linear relationship between muscle force and EMG amplitude, correlation effective only up to 60% of the exerted force, because of the muscular fatigue appearing beyond this threshold. During such a muscular fatigue, due to maximum contraction, it is possible to observe a progressive decrease in the EMG activity, owing in particular to the motor-neuron reduced discharge-frequency. CONCLUSIONS: This result suggests a small benefit of long-lasting muscular contractions, both in maximum and in medium protrusion movements, for re-educational purposes. Only during the medium-degree, 10 sec-lasting contraction it's possible to point out a turns-number variation significant of an active and constant contraction, which decreases if long-lasting (30 sec).

Child↗
PubMed1999

[Rehabilitation, using prosthetic implants, in patients with cancer of the oral cavity].

BACKGROUND: The number of patients treated for neoplasms of the oral cavity (by surgery and/or radiotherapy) requiring prosthesis rehabilitation using osteointegrated implants is increasing greatly. The objective of this research is to examine the correlation between prosthesis rehabilitation using osteointegrated implants, radiotherapy and the use of hyperbaric oxygen treatment in order to reduce the risk of osteoradionecrosis. METHODS: Research was carried out on 13 patients with 58 implants. The patients were divided into three sample groups: group A patients underwent radiotherapy (10 implants), group B patients did not undergo radiotherapy (29 implants) and group C patients first underwent radiotherapy and then hyperbaric oxygen treatment (19 implants). The group C patients first underwent hyperbaric oxygen treatment at 2.5 atmospheres. The osteointegrated implants were then applied and hyperbaric oxygen treatment was carried out again over 20-30 postoperative sittings without any other treatment between the sittings. The whole test period lasted 24 months. RESULTS: Only two implants were lost out of the 58 implants and they were in the group that had undergone radiotherapy. CONCLUSIONS: The results show how pre and postoperative hyperbaric oxygen treatment improves the success rate of osteointegrated implants in mandibular areas that had previously undergone radiotherapy. Moreover, the stability of the prostheses that are fixed to the implants is greatly improved compared to conventional methods.

Dental Prosthesis, Implant-Supported↗
PubMed1998

Skeletal and dental modifications produced by the Bionator III appliance.

The therapeutic results of a functional orthopedic treatment with a Balters' Bionator III appliance were evaluated. The sample group included 39 white growing subjects with a dentoskeletal Class III malocclusion. A 2-year study compared results with a control group. The results showed that the Bionator III is effective, especially when the malocclusion is mainly the result of a midfacial deficiency and when there is a hypodivergent growth pattern.

Activator Appliances↗