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Biomedical subjects

Antonio Costa

Publications and source records attributed to Antonio Costa.

4 recordsLinked to original sources
PubMed2006

Comparison between two orthodontic skeletal anchorage devices: osseointegrated implants and miniscrews - Medical-Legal Considerations.

The object of this article is to describe potential medical-legal problems concerning the use of miniscrews as orthodontic skeletal anchorage. The miniscrews, which are already used in rigid fixation, do not need either a healing period before loading, or complete osseo-integration as do implants. Their particular shape allows high primary stability and they can be placed in the sub-periosteal region. The dimensions of these miniscrews are minute, with dimensions of only 4-5 mm in length. They penetrate only slightly deeper than the cortical layer and therefore notably reduce the risk of lesions to roots, nerves, or maxillary sinus, when compared to other skeletal anchorage systems such as implants. The use of the miniscrew in oral surgery or periodontology does not need specific insurance coverage in contrast to the insertion of implants. Accordingly, orthodontic therapy completed by the dentist with orthopaedic microscrews as anchorage could also be included in a general civil insurance policy for orthodontics.

Bone Screws↗
PubMed2002

Predicting experimental complexation-induced changes in (1)H NMR chemical shift for complexes between zinc-porphyrins and amines using the ab initio/GIAO-HF methodology.

Ab initio calculations were carried out on zinc-porphyrins complexed to several amines: N-(3,5-dimethyl-pyridin-4-yl)-formamide, 1,4-diazabiciclo[2.2.2]octane (DABCO), and 1-azabiciclo[2.2.2]octane (quinuclidine). The proton chemical shifts of these complexes were calculated ab initio at the GIAO-HF/6-311G//HF/3-21G level of theory, and the obtained values agree satisfactorily with experimental results. The complexation-induced changes in (1)H NMR chemical shifts correlate well with differences in association constants of several host-guest complexes.

Journal Article↗
PubMed2002

Quantification of aromaticity in oxocarbons: the problem of the fictitious "nonaromatic" reference system.

Despite the extensive research reported in the literature, the concept of aromaticity has eluded rigorous quantification. The main reason for this undesirable reality is the fact that aromaticity is a differential property. While bond orders, atomic charges and electronegativity differences are properties of the molecule under analysis, the aromaticity concept often refers to the difference between some property of the molecule and that of an artificial "nonaromatic" reference system. A rigorous definition of such a reference system is non-existing and therefore constituting the main barrier to obtain a satisfactory quantification of the aromatic concept. Oxocarbon acids and their anions are examples where the criteria of aromaticity that use reference systems are unsuccessful, only NICS criterion gives satisfactory results. Wiberg bond indexes and 17O NMR chemical shifts are also useful to study such compounds.

Journal Article↗