Dentistry – Prosthodontics – Holding or positioning denture in mouth
Patent
1998-05-21
2000-08-29
Lucchesi, Nicholas D.
Dentistry
Prosthodontics
Holding or positioning denture in mouth
433172, A61C 800
Patent
active
061099198
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an implant system, specifically a dental implant system for a partially or fully edentulous patient which comprises a fixture for implantation into the bone tissue of the maxilla or mandible of the patient for supporting a superstructure which in turn supports or presents a dental restoration comprising one or more artificial replacement teeth. As an example, the superstructure may be an abutment which is adapted in use to be connected to the implanted fixture to bridge the soft tissue layer (gingiva) overlying the maxilla or mandible for a restoration structure such as a crown or bridge to be secured thereto.
In a typical dental implant system the superstructure is screw retained to the fixture. To this end, the fixture has an internally threaded socket which opens in a rear end of the fixture. The internal threads may be present throughout the socket or alternatively just in a section of the socket. The superstructure is then either (i) integrally formed with an externally threaded projection for screwing into the internally threaded socket to secure the superstructure to the fixture, or (ii) comprises a sleeve part having a lumen in which a transverse bearing surface is provided, and a screw part for passage through the lumen of the sleeve into the internally threaded socket, the screw having an enlarged head which is adapted in use to bear against the transverse bearing surface in the lumen of the sleeve thereby ensuring that the superstructure is secured to the fixture on screwing of the screw into the internally threaded socket.
In other dental implant systems the superstructure is secured to the fixture through non-screw thread connections, e.g. by cementing.
Whatever the form of securement of the superstructure to the fixture, the superstructure transmits a load to the fixture in the implantation direction through mutually interfacing surfaces.
Fixation of a fixture of a dental implant system in the bone tissue of the maxilla or mandible primarily relies upon mechanical interlocking of bone tissue to the outer surface of the fixture. Substantial interlocking between the outer surface of a fixture and the bone tissue of the maxilla or mandible occurs when the outer surface is roughened, for example by providing the fixture outer surface with screw threads, recesses, holes etc. (macroroughening), forming pits in the fixture outer surface by blasting, plasma spraying, etching, hydroxyapatite coating, the provision of beads on the outer surface etc. (microroughening) or machining the fixture outer surface. Interlocking between the outer surface of a fixture and bone tissue of the maxilla or mandible into which the fixture is implanted enables the fixture to greater withstand shear stresses. One can consider this to be due to bone tissue growing into the cavities in the fixture outer surface created by the roughening.
A macroroughened fixture outer surface produces more effective interlocking than a microroughened fixture outer surface which in turn produces more effective interlocking than a machined fixture outer surface. All, however, produce more effective interlocking than fixtures having an outer surface which is smooth, e.g. a polished outer surface. More than one form of surface roughening can be applied to a fixture to promote interlocking. For example, it is known to provide a fixture with both a macro- and a microroughened outer surface.
In 1892 it was suggested by J. Wolff (Das Gesetz der Transformation der Knochen. Berlin: A. Hirschald, 1892) that bone tissue remodels itself in response to the mechanical loading history of the bone and in accordance with mathematical laws. This has since proved to be correct and is therefore now known as Wolff's law. Some consequences of Wolff's law are that: net loss of bone tissue (bone resorption) will result until a new steady state is obtained where the stresses or strains are normal. then no net change to the bone tissue will result. within physiological limits bone tissue build up will result until a new steady state
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Astra Aktiebolag
Lucchesi Nicholas D.
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