Biomedical subjects
Publications and source records attributed to G Sfondrini.
Traditional upper molar distalization techniques require patient co-operation with the headgear or elastics. Recently, several different intraoral procedures have been introduced to minimize the need for patient co-operation. This article reviews the appliances currently available for maxillary molar distalization and critically analyses their dentoalveolar and skeletal effects.
The purpose of this study was to evaluate the shear bond strengths of a composite resin (Transbond XT; 3M/Unitek, Monrovia, Calif) and a resin-modified glass ionomer (Fuji Ortho LC; GC America Inc, Alsip, Ill) cured with 2 different light-curing units: a conventional visible light unit (Ortholux XT; 3M Dental Products, St Paul, Minn) and a xenon arc light unit (Plasma Arc Curing [PAC] System; American Dental Technologies, Corpus Christi, Texas). One hundred twenty freshly extracted bovine permanent mandibular incisors were randomly divided into 1 of 8 groups; each group consisted of 15 specimens. Two groups (1 group for each type of adhesive) were exposed to the visible light for 20 seconds (Transbond XT) and 40 seconds (Fuji Ortho LC), respectively, and used as control groups. The remaining 6 groups (3 for each adhesive) were cured with the xenon arc light for 2, 5, and 10 seconds. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested in a shear mode on an Instron universal testing machine (Instron Corp, Canton, Mass). For the groups bonded with Transbond XT, no statistically significant differences (P =.868) were found between the shear bond strength of the control group cured with Ortholux XT and those of the groups cured with the PAC System for 2, 5, or 10 seconds. When the shear bond strengths of the groups bonded with Fuji Ortho LC were evaluated, no statistically significant differences (P =.087) were found between the control group that was cured with Ortholux XT and those cured with the PAC System. The bond strength of the composite resin was significantly higher than that of the resin-modified glass ionomer in all the groups tested (P <.0001). The present findings indicate that, compared with visible light-curing, the xenon arc light enables the clinician to significantly reduce the curing time of both bonding agents, without affecting their shear bond strengths. Therefore, xenon arc light sources can be recommended as an advantageous alternative for curing both composite resins and resin-modified glass ionomers.
Explore the source record for details and available documents.
In the last few years, orthodontic literature has shown particular interest in the interproximal enamel reduction technique described as stripping or slenderizing. Most researchers have shown, by scanning electron microscopy (SEM) studies, the difficulties encountered while attempting to remove coarse abrasions left after stripping with the first instrument. The objective of this SEM study was to compare the different polishing methods proposed in the literature and to assess the efficiency of our own procedure. For this purpose, 48 healthy human teeth (premolars and molars) were used after removal for orthodontic or periodontal reasons. The teeth were divided into eight groups of six teeth each (two molars and four premolars), and mounted on a typodont to simulate a clinical situation. Each group underwent stripping according to one of the following techniques: 16-blade tungsten carbide bur and fine and ultrafine diamond burs; coarse diamond bur and fine and ultrafine diamond burs; coarse diamond disk and Sof-Lex disks (Dental products/3M, St. Paul, Minn.); 16-blade tungsten carbide bur and phosphoric acid on finishing strip; and 8-straight blade tungsten carbide diamond bur and Sof-Lex disks. The SEM investigations demonstrated that it is not possible to eliminate, with normal polishing and cleaning methods, the furrows left on the enamel both by the diamond burs and the diamond disks and the 16-blade tungsten carbide burs. Mechanical and chemical stripping as well did not prove to be effective. By contrast, with the use of a 8-straight blade tungsten carbide bur followed by Sof-Lex disks for polishing the enamel, it is possible to obtain well-polished surfaces that many times appear smoother than the intact or untreated enamel.
The plasticity of masticatory muscles was studied by comparing rats that were wearing a protrusive appliance and were kept on a liquid diet with two control groups: (1) pair-fed rats and (2) rats that had free access to ordinary pelleted food. The animals were 45 days old at the beginning of the experiment and were studied for a period of 20 days. Three jaw muscles with different functions were examined: masseter, temporalis, and digastric. Muscle fiber composition was determined (1) by fiber counting after staining with four monoclonal antibodies, which were able to recognize the four major myosin heavy chain (MHC) isoforms and therefore four fiber types (I, IIA, IIX, IIB) and (2) by electrophoresis on 6% polyacrylamide gels. The comparison between free-diet rats and pair-fed rats showed that the change from a hard pelleted diet to a liquid diet caused a shift in fiber type and MHC distribution, characterized by an increase of IIB MHC in temporalis and digastric muscles but not in the masseter muscle. The comparison between pair-fed rats and rats wearing appliances showed on the contrary a decrease in IIB MHC and an increase in IIA and IIX MHC. The results support the conclusions that (1) rat jaw muscles can quickly adapt to functional demand changing their fiber type composition, (2) the changes appear restricted inside the fast fiber population, and (3) fiber-type changes caused by dietary variation are not less than those caused by orthodontic intervention and must be taken into account to assess the effect of the appliance correctly.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A deep examination of the literature till now available as well as personal experience, shows the advantages and the simple use of the fine needle aspiration method both for the diagnosis of tumours and other not neoplastic lesions. This method can be easily executed, it is painless, a high accuracy can be achieved also in clinically doubt cases and in early tumours. The authors think that the use of this method will spread rapidly because of its effectiveness and convenience.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.