Field of the invention

The present invention finds application in the medical field, in particular in the odontostomatological surgery, and concerns the procedures for bone tissue regeneration.

Background

When it is not treated, alveolar bone loss may ultimately result in loosing teeth.

Alveolar bone loss may be involved with pathologies such as periodontal disease, acute infections or trauma; more than 50% of dental implant treatments require some intervention for bone regeneration.

Depending on the clinical condition of the area to treat, many techniques have been proposed, as well as different grafting materials.

As for the techniques, they can be briefly divided into: block grafting, wherein bone blocks are used as a regeneration material, or guided bone regeneration, wherein particles of grafting material are packed to fill a bone defect and covered by a membrane, resorbable or unresorbable.

Based on their nature, grafting materials are classified into: autogeous, heterologous, xenogenic or alloplastic. Guided bone regeneration was developed upon the concept of compartimentalization.

Therefore, in order to regenerate bone, a space is created and shall be maintained during healing, and undesired cells are prevented from migrating into the graft.

In case the defect is severe, it is more complex for a barrier to maintain its shape and avoiding collapse.

In order to solve said issue, membranes reinforced with bendable metal plates have been developed.

Titanium meshes are an alternative solution because they are suitable to create a stable scaffold that protects a particled graft.

The use of metal devices is associated with some drawbacks, including metal hypersensitivity and more frequently the risk of immediate or delayed infection; such circumstances may seriously impair the outcome of the therapy and cause patient morbidity.

Zirconia is a polycrystalline ceramic.

At ambient pressure, unalloyed zirconia may assume three crystallographic forms depending on the temperature: monoclinic up to 1170°C, tetragonal between 1170-2370°C and cubic above 2370°C.

Since tetragonal is the toughest one, Zirconia can maintain the tetragonal phase at room temperature when stabilizers such as ceria, magnesia, or yttria are added. Zirconia is the toughest ceramic available for dental application, with a flexural strength up to 1200 Mpa: crack propagation is blocked by a volume expansion at the crack tip.

As all ceramic materials, it shows a brittle behaviour.

Zirconia finds use in dentistry as a restoration material and to manufacture metal-free dental implants, metal-free crowns and bridges (commercially available from Zirkonzhan, Noritake, 3M, Wieland).

Summary of the invention

The inventor of the present patent application has surprisingly found that zirconia can be used for the preparation of an insert to be used in dentistry in a method for the treatment of bone regeneration.

Object of the invention

In a first object, the present invention discloses a dental insert made in a bioinert material.

In a second object, the present invention discloses a method for the preparation of a dental insert made in biocompatible material.

In a third object, it is disclosed a method for the treatment of alveolar bone defect comprising the use of the dental insert of the invention.

As a further object, it is disclosed a bioinert material for medical use. In one embodiment, it is disclosed a bioinert material for medical use in the medical treatment of alveolar bone defect.

In another embodiment, it is disclosed a bioinert material for medical use for promoting the blood circulation at the application site.

Detailed description of the invention

According to a first object of the invention, it is disclosed a dental insert in bioinert material.

For the purposes of the present invention, a "dental" insert is to be intended as an insert conceived to be used in the oral cavity.

Though the above, it cannot be excluded that an insert according to the invention might find application to other sites, such as for instance, the cheekbone.

For the purposes of the present invention, the term "insert" shall be intended as an object that should be placed in contact with the bone.

In the present description, "insert" and "plate" shall be intended as synonims.

As per "bioinert" material it is intended as a material, which does not elicit an immunological or inflammatory response.

As per "ceramic material" it is intended as a material, which is a solid material comprising an inorganic compound: metal or metalloid or non-metal with ionic or covalent bonds. In particular, advanced ceramics are not generally clay- based; instead, they are either based on oxides or non-oxides or combinations of the two.

According to preferred embodiment of the invention, it is disclosed a bioinert ceramic material selected from the group comprising: zirconia, and zirconia-reinforced materials.

According to alternative embodiment of the invention, the insert is in a material represented by polyaryletherketone (PEAKs) polymers.

A preferred PEAKS polymer is represented by polyaryletheretherketone (PEEK).

For the purposes of the present invention, the "bioinert" material is not a metal.

In a preferred embodiment of the invention, the bioinert ceramic material is represented by zirconia.

According to a second object of the invention, it is disclosed a method for the preparation of a dental insert in bioinert ceramic material.

In a first embodiment, said method comprises the steps of preparing said insert having suitable dimensions (standard insert).

More in particular, with "suitable dimensions" it is intended dimensions, which are compatible with a possible bone defect to be treated.

In particular, said dimension may be: and preferably, said dimensions may be:

As per the first embodiment, a set of inserts with different dimensions may be provided regardless a specific need of a patient.

Once it is required for the intervention, the surgeon may select from said set the insert having the dimensions, which best fit the patient bone defect.

A plurality of inserts comprising a set of inserts with different dimensions represents a further object of the present invention.

According to a second embodiment, the method for the preparation of a dental insert in bioinert ceramic material is carried out on a target patient and the insert is characterized by dimensions tailored on the patient's bone defect (custom o customized insert).

In particular, said method comprises the steps of: a) acquiring, by means of a scanning device, a digital representation of a bone atrophy of the portion of the dental arch of a patient to be treated; in particular, bone morphology. b) determining, by an electronic computer, on the basis of said acquired digital representation, a set of points representative of said portion of the dental arch; c) determining, by the electronic computer, on the basis of said set of representative points, a three- dimensional model of said dental insert to be inserted in the portion of the dental arch to be treated and for which a digital representation has been acquired; d) manufacturing, by means of a dedicated electronic device, on the basis of said determined three-dimensional model, the dental insert corresponding to the model determined as per step c).

In a particular embodiment of the present invention, step a) for the acquisition of the digital representation is performed with 3D X-ray.

For instance, 3D X-rays may be carried out with computer tomography.

As per step a), it is intended that the portion of the bone, such as the dental arch portion bearing the bone defect, is scanned for acquiring a digital representation thereof.

According to a preferred embodiment, step d) of manufacturing is performed by additive or subtractive manufacturing.

In particular, additive manufacturing includes techniques like 3D-printing. Subtractive manufacturing may be performed with suitable milling machines.

According to a third object of the invention, it is disclosed a method for the treatment of alveolar bone defect comprising the use of a dental insert as above reported.

For the purposes of the present invention, alveolar bone defect shall be intended as a portion of the dental arch missing a part of the bone, said loss preventing the insertion of a dental implant.

Alveolar bone defect shall be intended as including alveolar bone loss.

In particular, said method for the treatment of alveolar bone loss comprises the steps of:

- acceding the site with an alveolar bone defect,

- filling the site with a grafting material,

- covering the grafting material with the insert in the bioinert ceramic material of the invention.

According to the present invention, said grafting material may be autologous, heterologous, xenogenic or alloplastic.

In particular, the above referred alveolar bone defect may be involved with pathologies selected in the group comprising: periodontal diseases, acute infections or trauma.

For the method for the treatment of alveolar bone loss according to the present disclosure, the invention insert in a bioinert ceramic material may have an occlusive or a not- occlusive surface.

The use of an occlusive with respect to a not-occlusive surface depends upon the clinician's preference regarding the bone regeneration protocol.

More in general, an occlusive surface offers a maximized barrier effect.

In case of a premature re-opening of the wound, an occlusive surface helps reducing the bacterial contamination.

A not-occlusive surface comprises several apertures, letting the periosteum and vascular supply of the flap to speed-up the healing process; however, in case of premature wound healing, a not-occlusive surface is more prone to lead to an infection of the bone graft.

For the method for the treatment of alveolar bone loss according to the present disclosure, the invention insert in a bioinert ceramic material may have a polished or a roughened surface.

A polished surface more easily prevents bacterial adhesion both during surgery and in case of premature wound re-opening.

A rough surface promotes the adhesion of the fibroblast of the flap to the surface of the insert, with the inconvenient of a higher probability of a bacterial adhesion. According to a fourth embodiment, the present invention discloses a dental insert in a ceramic bioinert material for medical use.

In particular, said insert in a ceramic bioinert material is disclosed for medical use in the treatment of alveolar bone loss.

More in particular, said dental insert is applied to a site (portion) of the dental arch to be treated and promotes the blood circulation at the application site.

Figure 1 shows an example of a clinical application of a custom insert with occlusive and highly polished surface according to the invention. After anesthesia (A), an incision is made and a flap is elevated in order to access the bone defect (B). The clinician can choose a grafting material suitable to treat the defect. If a standard insert in used, its shape is selected to obtain a best fit with the surrounding bone, then it is fixed with screws (C,D) or other fixation means and the box created is filled with grafting material. Surgeon should pack grafting material into the defect and/or into the insert and fix it to the adjacent bone by means of screws or other fixation device. Before suturing (E), releasing incisions are made to obtain a passive closure of the flaps.After healing (F), usually three to nine months, depending on the size of the defect and on the grafting material, a second surgery is performed to remove the insert. Figure 2 shows an intervention for bone loss regeneration with the use of a custom insert according to the invention fitting the defect thanks to a proper CAD design of the bone defect. After anaesthesia, an incision is made and a flap is elevated in order to access the bone defect (A). The clinician can choose a grafting material suitable to treat the defect. Surgeon should pack grafting material into the defect and/or into the insert (B) and fix it to the adjacent bone by means of screws or other fixation device(C-D). Before suturing, releasing incisions are made to obtain a passive closure of the flaps (E)(F).After healing, usually three to nine months, depending on the size of the defect and on the grafting material, a second surgery is performed to remove the insert.

From the above description, the advantages of the present invention will be clear to the person skilled in the art.

In particular, the insert of the present invention, compared to metal insert, significantly reduces the formation of the bacterial biofilm; that represents an important aspect in case of a premature wound opening, because it permits to maintain the insert in place for longer time before removing it.

The longer the insert stays in place, the better the chances are to obtain bone regeneration. When a metal insert or a not resorbable membrane is exposed, there are likely to occur infections that could impair bone regeneration.

In addition, the insert of the invention has surprisingly shown to trigger less inflammation.

As a further advantage, thanks to the surprising effect of significantly increasing the microcirculation at the soft tissue interface at the site of treatment, it promotes healing reducing the time to proceed with the completion of the treatment.

The insert according to the invention can be manufactured in a wide range of suitable dimensions so as to provide a set of inserts for many interventions.

In those cases wherein the insert is prepared making use of the 3D technology, then the insert can be realized with size and dimensions tailored to the actual needs of a patient; the performance of the insert, the patient acceptability and compliance will be therefore increased.

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