Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C8/00—Means to be fixed to the jaw-bone for consolidating natural teeth or for fixing dental prostheses thereon; Dental implants; Implanting tools
  • A61C8/0018—Means to be fixed to the jaw-bone for consolidating natural teeth or for fixing dental prostheses thereon; Dental implants; Implanting tools characterised by the shape
  • A61C8/0031—Juxtaosseous implants, i.e. implants lying over the outer surface of the jaw bone

Definitions

• This invention is concerned with an implant device which is applicable to the maxillary bone for supporting a dental prosthesis.
• the main object of the invention is therefore to provide an implant device which solves the above critical cases in a single surgical step, at a limited cost, by allowing a suitable fixed prosthesis to be installed without having recourse to complex surgical maneuvers of osteoregeneration.
• this invention aims to provide an implant device that can be implanted even in situations where, due to insufficiency of bone tissue or to proximity of vulnerable organs or to other reasons, it is not possible to incise the patient's bone to the depth required for conventional implants, such as Linkow blades or titanium screws.
• a further aim of the invention is to provide an implant device that can be implanted by surgical procedures less critical than conventional procedures and that, for equal ability of the surgeon, are less liable to error or flawed surgical performance.
• Still another object is to provide an implant device which can be implanted more rapidly than conventional devices, and which more specifically allows the surgeon to carry out, in a single stage, the entire operative procedure including opening the mucoperiosteal flap, baring the bone, incising the bone, inserting the device, suturing the flap, and possibly setting up a temporary prosthesis.
• a further object of the invention is to provide an implant device allowing implantation to be performed at a lower cost than prior devices. .
• Fig. 1 is a side view, to an enlarged scale, of an implant device according to a preferred embodiment of the invention
• Fig. 2 is a front view of the implant device of Fig. 1;
• Fig. 3 is a lateral view taken obliquely from beneath, of the implant device of Fig. 1;
• Fig. 4 is a perspective view of a bite-mapping jig, used during the procedure for implanting the implant device of the invention
• Fig. 5 is a diagrammatical view of a radiographic mapping performed on a patient by means of the jig of Fig. 4;
• Fig. 6 is a perspective view of a surgical jig used during the procedure for implanting the implant device of the invention.
• Fig. 7 is a perspective view of a jawbone on which the surgical jig of Fig. 6 has been applied;
• Fig. 8 is a view in transverse cross-section of the jawbone of Fig. 7 during the step of incision of a sulcus for the application of the implant device according to the invention
• Fig. 9 is a view in transverse cross-section of the jawbone of Fig. 7, on which the implant device of Figs. 1 to 3 has been applied in the final position;
• Fig. 10 is a view in transverse cross-section of a jawbone with implant device and prosthesis.
• the invention consists in using a titanium implant device, shown on Figs. 1 to 3, and comprising a saddle-shaped laminar mantle 10, a laminar rib 12 which is integral with the underside of mantle 10, perpendicularly along its ridge, and a couple of cylindrical stumps 14 rising from the topside of mantle 10, in alignment with rib 12.
• Both mantle 10 and rib 12 are thickly perforated with a honeycomb arrangement of small, round holes such as 16.
• the average thickness of both mantle 10 and rib 12 is preferably 0.6 mm, and holes 16 have a preferred diameter of 2 mm.
• Rib 12 preferably extends for the entire length of mantle 10, with a preferred average height of 4 mm, although its height is not necessarily uniform, but rather is liable to variations, possibly vanishing locally, as will be explained in more detail below.
• the above described device is custom-designed for the specific patient and for the specific area of maxillary bone requiring a prosthesis, to have a shape and size such that the underside of mantle 10 perfectly matches the bone surface and that rib 12 is tailored to be inserted with a precise coupling in a groove or sulcus carved in the bone by the dentist.
• the best procedure found by the inventor for building the device of Figs. 1 to 3, as well as for using it, is described below.
• the patient is first submitted to a dental panoramic radiograph and to a TAC by a spiral TC apparatus, in order to obtain geometric data on the patient's maxilla, from which, by appropriate digital data processing, a stereolithographic model of the maxillary bone is made in transparent resin.
• the model shall be an exact tridimen- sional replica of the patient's upper and/or lower maxillary bone, on which tests and measures can be carried out which are equivalent to tests and measures made directly on the patient's maxillary bone.
• a stereolithographic model can be built from the initial geometric data in a largely automated process by selective sintering of a thermoplastic powder, as known, for instance, from EP 0 287 657.
• the stereolithographic model gives a complete representation only of the geometry of the maxillary bone. Therefore, in order to have adequate geometric data also for the mucous membrane and for the patient's occlusal registration, prior to the surgical operation, the patient should perform, according to the invention, a test on a wax registration bite, in which suitable radio-opaque profiles are incorporated.
• a transparent measurement jig of an acrilic resin is prepared on a conventional chalk cast (not shown) of the patient's maxilla.
• the jig should be adapted to rest in a predetermined position on the maxilla, and should comprise a bridge 20 crossing the lingual area behind the incisors and integrally connecting two saddles 22, 24, resting on the edentulous areas, the saddles supporting respective, conventional wax bites 26 and 28.
• Jig 20-22-24 is inserted in place in the patient's mouth. The patient then closes his/her mouth to effect the occlusal registration. Once the registration is completed, a small intra-o al radiograph is taken, the film being mounted on a holder (not shown) so that an image similar to Fig. 5 is obtained, where wires 30 and 32 represent the profile and the uniform mapping of the soft tissues with respect to bone 34 and to the antagonistic occlusal surface, respectively. Consequently, the vertical dimension of stumps 14 can be determined in advance, and, by means of the bite impression, also their optimal placement and lie in view of setting up a prosthesis, as will be apparent to persons skilled in the art.
• a wax model of the implant structure is now built.
• the trace of the surgical sulcus which shall accommodate the vertical rib is marked on the stereolithographic model by an indelible marker, such as a pen.
• a crestal incision is made in the resin, under water cooling, by a suitable circular, saw of a 10 mm diameter, 0.5 mm thickness, and a cutting depth of 4 mm, the saw being mounted on a drill.
• a gauged, honeycomb wax strip (as commonly used in odontotechnics and commercially available) of 0.6 mm thickness is inserted in the cut, and the strip is then delicately carved with a thin blade along its crestal outcrop.
• peripheral outline of the saddle is now drawn with a pen or other marker: its extension should be as large as possible, though limited by the anatomical constraints imposed by the extension of the flap and by possible obstacles such as the emergence of the lower maxillary alveolar nerve.
• a rectangular piece of gauged honeycomb wax of 0.6 mm thickness, is laid and shaped on the area and is welded with the underlying rib, whereby the holes near the rib are plugged, for reasons explained below.
• peripheral outline is then cut off with a thin blade.
• vertical wax stumps are then placed at the predefined sites and axes and are then welded to the saddle.
• a wax model of the inventive implant device is thereby obtained, which is ready for making a titanium single casting corresponding to the implant device as shown on Figs. 1 to 3, and accurately matching the geometry and the specific conditions of the edentulous area of the patient's maxillary bone.
• the inven- tion provides that a titanium template is used, allowing the crestal cut made on the resin model to be exactly replicated in the patient's mouth.
• a wax model of the template is made by laying and shaping a sheet of 0.6 mm gauged, solid wax onto the model which has been previously marked with a pen.
• the function of the template is to accurately steer the cutting tool, so that its overall surface in breadth can be obtaining by cutting its edges well within the area bounded by the pen for the implant device: on the other hand, it is necessary to hot-carve the template model with a wax knife along the crestal cut, and fully clear the sulcus of any wax.
• a laminar, saddle-shaped titanium template 36 is cast from the wax model so molded, which template will perfectly match the stereolithographic model (not shown) in the edentulous area (and therefore, later, the maxillary bone itself) and having a slot 38 corresponding to the sawed cut described above.
• both a temporary fixed, titanium-reinforced resin bridge, and a final prosthesis, say of porcelain, are produced by techniques well known and therefore not described here.
• the surgical stage is initiated.
• an implant is to be performed on a lower maxillary bone 40, shown schematically, in which the associated alveolar nerve 42, as well as its emergence point 44, are shown in dotted lines.
• the dentist performs the operation under local anesthesia and, as shown on Fig. 7, begins by opening the mucoperiosteal flap 45 in the edentulous area.
• the flap should be full-thickness and as large as possible, so as to free an area allowing template 36 to be properly and easily adjusted on the edentulous area of the maxillary bone.
• the stability of the template is insured by fastening it to the cortical bone by means of one or two screws of appropriate length for osteo- synthesis.
• a circular saw 46 of 0.5 mm thickness and as used for the stereolithographic model, is applied to maxillary bone 40 through slot 38 in template 36, at a speed of about 1000 RPM and under constant physiological cooling.
• the bone is incised delicately without strain, with slow to-and-fro movements along the template slot, allowing the saw to cut both downwards and length- wise.
• the above described manoeuver is then repeated with a 0.6 mm saw, in order to finish the sulcus.
• Fig. 9 is a perspective view of the maxillary bone equipped with an implant device according to the invention, and Fig. 10 shows the same bone in a transverse cross-section, with a prosthesis 48 mounted on the stump.
• the surgical flap is sutured, while taking care to make suitable relief dents at the emergence sites of the vertical stumps, in order to allow the mucosa to properly wrap around the stumps without stresses.
• a temporary fixed bridge may be mounted in situ immediately after completing the suture, provided there are no evident contrary indications such as oedema, bleeding, gross occlusal interferences that cannot be corrected at once, or poor initial stability of the implant.
• the final fixed prosthesis can be mounted on the stumps. Plugging the holes above the ribs prevents the connective tissue from growing into the holes and hinder ossification.
• the waiting period may vary from one case to the other, depending on the operator's assessment.
• the rib of the above described implant is progressively integrated and anchored in the bone, but the forces acting on the implant during mastication are transferred to the maxilla mainly through the saddle-shaped mantle: for this reason, a small penetration of the rib into the bone is sufficient, in contrast to a penetration of over 1 cm as required with conventional implants.
• the periosteum will satisfactorily seal after surgery.
• the procedural modes described above for the installation of the device could be changed, both in respect of the manufacture of the stereolithographic model, which might be obtained by other techniques, and in respect of the use of accessory tools such as the template or the wax bite, which could be made differently or replaced by other techniques.
• the implant device, as well as the template may be built by the sinterizing techniques described above or by other technologies, directly starting from the geometrical data delivered by the tomographical survey, without having to actually build an intermediate stereolithographic model.

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• Health & Medical Sciences (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Orthopedic Medicine & Surgery (AREA)
• Dentistry (AREA)
• Epidemiology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Dental Prosthetics (AREA)
• Dental Preparations (AREA)

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• 2000
  • 2000-11-14 IT IT2000TO001056A patent/IT1320834B1/it active
• 2001
  • 2001-11-02 AU AU2002210843A patent/AU2002210843A1/en not_active Abandoned
  • 2001-11-02 WO PCT/IB2001/002056 patent/WO2002039921A1/en not_active Application Discontinuation
  • 2001-11-02 EP EP01978752A patent/EP1333770A1/en not_active Withdrawn

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