RO131187B1 - Process for making the metal structure of mobile component in skeletal prosthetic works by direct mock-up - Google Patents

Description

The present invention refers to a process for making the metal structures of the mobile, maxillary component, within the skeleton prosthetic works.

It is known that removable dental prostheses look and behave similar to natural teeth, being an effective alternative in case of their absence.

Artificial teeth can be mounted in a completely acrylic structure under the name of acrylic prosthesis or on a mobile metal structure under the name of skeletal prosthesis, a work that fits inside the oral cavity and works according to all the morphological, aesthetic and functional criteria and needs of each individual patient.

Lately, the interest of patients has increased for the rehabilitation and maintenance of the morpho-functional and aesthetic of the dento-maxillary apparatus, through the most comfortable, stable and aesthetic prosthetic works that are made with the latest techniques and materials.

Regardless of the causes of tooth loss (periodontal diseases, caries, accidents, etc.), their absence can have long-term consequences on the physical and mental health of patients.

Currently, prosthetic rehabilitation by skeletal prosthesis as a treatment method for terminal edentulous teeth is topical, even if the tendency to wear such rehabilitations can be replaced by fixed works made by the method of dental implants.

What benefits this prosthetic solution is both the not very high cost of these works and the comfort and masticatory efficiency in use.

Also, the therapeutic indication of these types of works is made, especially for cases in which, and for various health reasons, dental implants cannot be recommended, and there are enough pillar teeth on the arches that would support their loading with this type of prosthetic works.

Currently, from a technical point of view, in the case of prosthetic restorations with works such as skeletal prostheses, the metal structure of the mobile component is made through multiple and laborious technological steps.

In the classic or traditional method, the stage of making the model of the future movable structure involves duplicating the functional model and modeling a wax model on it, respecting the anatomical and morphological details of the prosthetic field to be rehabilitated.

From the state of the art, the book "Techniques for manufacturing dental prostheses", authors Gheorghe Bârsa and Ilarion Postolachi, Chisinau, 1994, is known, which refers to different types of dental prostheses and their manufacturing techniques, including skeletonized removable partial prostheses, which involves stages such as outlining the shape of the elements of the skeletonized prosthesis with the help of the parallelograph, deretentiveness of the retentive areas, foiling the mucosal surfaces with 0.5-1 mm wax foils, making the matrices, making the main connector, making models of the casting channels for casting the alloy after modeling and solidarization of the preformed models of all the component elements of the prosthesis skeleton, making the casting channels that solidarize to the thicker parts of the connecting elements, packing in known conformers, as well as processing and finishing the metal skeleton (see pg. 349, 354-357, 160 -163).

The document "Practice guide in dental prosthetics" by Norina Consuela Forna, UMF Iași, 2010, is also known, which presents various options of prosthetic therapy, including, among others, the skeletal prosthesis and the stages of its realization (see page 399445).

Duplication of the model is made with high-precision silicone materials to faithfully reproduce the prosthetic field and the anchoring elements present on the fixed part of the previously made primary structure. Following this procedure, we move on to the stage of actual creation of the duplicate model by pouring a specific packaging mass into this impression. The obtained model, after the setting time, goes through a hardening process so that it can then be ready for the modeling stage of the model of the future movable prosthetic structure. 3

This procedure is taught in specialized schools and used by dental technicians in laboratories as an indispensable step in obtaining these parts. However, the method presents certain disadvantages with repercussions on the precision and the allocated working time. As disadvantages we mention: 7

- the classic technique requires an increased development of skills, being more difficult to access for a novice technician or one with less experience in the field; 9

- through the duplication technique, the information is, to a certain extent, lost. During the stage of making the adaptation of the mobile structure to the fixed component, namely the rigid arms, 11 inner slides, the anchoring system and the main connector, a certain lack of precision is observed, which the technician has to correct by milling and close-up 13 close, to arrive at the precise and without tipping connection of the two metal structures;

- the time allocated to the whole process and the required experience is quite high. Often, 15 given the errors resulting from duplicating (the presence of gaps in the impression or in the duplicated model from the packaging mass, of porosities or simply, of the fracturing of some elements 17 in the step of detaching the model from the impression) the process must be repeated. This implies loss of both material and time; 19

- the amount of materials used is greater. Starting with the duplicate conformer, the silicone impression mass, the materials used to harden the duplicate model 21, and other adjacent technologies required to mount the duplicate model in the articulator, lead to increased production operational costs. 2. 3

The technical problem that the present invention solves consists in making a metallic structure of the mobile component intended for skeleton works through a technique that allows the elimination of errors resulting from duplication, the model being made directly on the working model. 27

The process of making mobile metal structures within the framework of skeletal prosthetic works, which involves the stage of making the functional working model from extrahard plaster 29 and attaching the Teflon matrices to the metal patrices, followed by a first stage of preparing the model for layout, a deretentivization of the surfaces in the area of the matrices, 31 of the gingival areas of the opposing arms and intraculis, followed by the application of a layer of foiling wax as a support for the resin and finally the planing operation of the sensitive surfaces 33 of the prosthetic field; a step of making the main connector; a stage of preparation for packaging which involves the attachment of a number of 4 to 6 main molding channels 35 of profiled wax, the application of a solidifying rod of the main channels, which joins with four, five or six rods of radial shape, which will represent the channels of 37 secondary casting, positioning the model at approximately equal distances from the walls of the metal ring, detaching the part, solidifying the casting channels on the cone of the 39 casting conformer, inserting the metal ring on the sleeve of the conformer at the optimal height; the inclined packaging technique stage, namely after gluing the model on the casting cone, 41 casting the packaging mass through the inclined technique, and after the pattern has been left for an hour to set, it is inserted for 60 to 90 minutes in the preheating furnace, 43 the temperature rising to about 950 degrees, for the operation of casting the Cr-Co alloy; the last stage consisting in adapting the structures by finishing and settling the metals, 45 respectively polishing and removing burrs from the internal surfaces followed by a light hitting of the structures, in the insertion axis, with a 100 gram hammer, after adaptation 47 the metal structure being brought at the limits of the drawing, after which it is processed and finished with milling cutters, polybands and specific discs, based on classic operations, known in themselves, it eliminates the mentioned disadvantages and solves the mentioned technical problem in that, after preparing the model for layout, the casings are made acrylic resin matrices by brushing and modeling them within the existing spaces and highlighted in the articulator, direct layout with acrylic resin, being followed by the stage of making the main connector, which is done in several steps, i.e. insulating with paraffin oil, applying of acrylic resin by brushing to create the rigid support of the model, the realization of an additional reinforcement with wax, the application of the profiled wax over the rigid resin support, the modeling of the borders between the application areas of physiognomic materials and the metallic structure of the connector, and finally step of the modeling, the wax grid is attached.

This procedure automatically generates several advantages for both the dental technician and the patient:

- the method simplifies the work procedure;

- it is much more efficient than the classic method, because by eliminating some stages, the time allocated to the execution is reduced by up to 40%;

- operational production costs are reduced by saving up to 30% of materials normally consumed by the classic method;

- the precision is greatly increased by the fact that the information is not lost in the duplication process and the resin used is of high precision;

- it is easily approachable, without the need for extensive experience in the field.

Other advantages brought by the present method according to the invention are:

- the layout is made directly on the functional model with acrylic resin, which reduces the execution time of the work and ensures increased precision given the direct copying of the prosthetic information;

- the possibility of mounting the functional model in the articulator gives the possibility of modeling the metal structure according to the antagonists - respectively of the teeth in the area of the anchoring systems, to the size and existing occlusal and vestibulo-oral space;

- the siliconized duplicating mass, the duplicating conformer and the duplicating model hardening materials are eliminated from the technological process, which generates a reduction in the costs of the work;

- the direct layout technique, on the other hand, offers the possibility of correcting any error on the fly, during the modeling stage, which gives great comfort to the technician and eliminates the "stress of failure" for less experienced practitioners;

- the shrinkage of the resin is very small, the tightness of the joints and the precision of the adaptation is much increased;

- the space of foiling and controlled spacing that is achieved in the manufacturing stage of the main connector can be compensated in a relatively short time. After the application of the work in the oral cavity, this space has the role of compensating for clogging and eliminates the possible injuries of the oral tissues that occur in the ordodontic readjustment process of the permanent teeth over time.

In the following is presented, for example, a mobile metal structure of the maxillary arch, in several stages of realization specific to the process according to the invention, in connection with fig. 1...23, which represent:

- fig. 1, view of the functional model;

- fig. 2, representation of the stage of deretentivization and foiling of the surfaces of interest for the design and modeling of the resin structure;

- fig. 3, representation of the way in which the preparation of the model is carried out before 1 the application of the acrylic resin;

- fig. 4, the modeling stage of the resin model, respectively the beginning of the manufacture3 of the matrix casings which is composed of the inner slides, the opposing arms and the Teflon-coated matrix casing pre-modelled in the shape of the corresponding tooth;5

- fig. 5, exposure of the raw resin modeling of the die cases, side view;

- fig. 6, exposure of the raw resin modeling of the matrix housings, front view; 7

- fig. 7, modeling the rigid resin support of the main connector;

- fig. 8, complete modeling of the rigid resin support;9

- fig. 9, application of profiled wax for a striated appearance;

- fig. 10, gluing the profiled wax to the resin support with a hot spatula; 11

- fig. 11, the modeling of the boundaries between the main connector and the acrylic masses that will be applied later; 13

- fig. 12, application of the profiled wax grill for retaining the acrylic mass;

- fig. 13, the wax application of the delimiting border of the main connector and the acrylic mass 15 applied in the area of the retentive grid;

- fig. 14, mock-up modeled and detached from the model; 17

- fig. 15, application of casting rods;

- fig. 16, application of the shrinkage compensating rod; 19

- fig. 17, the appearance of the casting channels seen from above;

- fig. 18, attaching the model to the casting conformer; 21

- fig. 19, view of the model glued to the casting cone in optimal position;

- fig. 20, cast part view; 23

- fig. 21, piece adapted by finishing and metal pressing technique;

- fig. 22, the work in the pre-final stage with a finished appearance of the metal; 25

- fig. 23, additional vein-like reinforcement of the connector.

The procedure for making mobile metal structures in the case of skeletal prosthetic works 27 assumes that after making the functional working model from extrahard plaster and attaching the teflon matrices to the metal parts, the preparation procedures 29 for direct layout should be started.

Thus, in a first stage of the process, the model is prepared for 31 layout. As can be seen from fig.1, on the functional model, there are present the metallic skeletons of the fixed component on which the teflon matrices are attached. At this stage, the design of the future mobile component is made, which is outlined with a pencil.

After drawing the outline of the future main connector, deretentivization of the 35 surfaces in the area of the matrices, the gingival areas of the opposing arms and intraculis is done and a layer of foiling wax is applied as a support for the resin, followed by the planing of the 37 sensitive surfaces of the prosthetic field. The wax will exceed the outline of the drawing by 2.5-3 mm to prevent the acrylic resin from sticking to the plaster during its application phase. 39

A few notes about the foiling procedure: due to the fact that wearers of skeletal prostheses, over time, endure a process of orthodontic readjustment of the remaining teeth, with 41 consequences on the supporting tissues and bone structures, they will be painfully pressed or damaged of the metallic structure of the connector, in the contact areas. In order to avoid these events, in this stage preparatory to modeling the model, preventive measures are taken, by foiling the areas of the hard palate or the palatine ridges, by thickening the wax layer in those areas. This will allow, in the future, to compensate for the clogging of the mobile skeleton in the prosthetic field over time and to avoid possible 47 decubitus injuries.

When this wrapping is not done, often the consequences over time are painful for the patient, and a subsequent intervention on the metal structures, in the painful areas, will be at the expense of the mechanical strength of the main connector and, respectively, of the entire work.

The second stage consists in making the resin matrix casings by brushing and modeling them within the limits of the existing spaces highlighted in the articulator. These will later be machined and adjusted with laboratory cutters to achieve the desired shape and thickness.

The third stage of the process consists of making the main connector, which is done in several steps:

a. A first step is to apply the acrylic resin by brushing, after insulating the surfaces with paraffin oil. This work is the rigid support of the layout. The modeling must exceed the contour of the drawing by 1-1.5 mm, but not pass the previously applied wax surface.

b. The next step consists in applying the 0.4 mm profiled wax, with specific striations, over the rigid resin support, which will be solidified at the borders of the drawing, with the help of the hot spatula directly on the resin structure.

Before applying the profiled wax, an additional wax reinforcement can be made to increase the mechanical strength of the connector.

The reinforcement will have a venous aspect, exemplified in fig. 2. 3.

c. Afterwards, the boundaries between the application areas of the physiognomic materials and the metallic structure of the connector are modeled to avoid the "lost passage" between the two materials and to clearly highlight the expansion limits between them.

d. In the last step of modeling, the wax grid is attached which will represent the future support and retention structure of the acrylic masses.

The fourth stage consists of preparation for packaging. This is done in three steps:

a. Attach the main molding channels of profiled wax with a diameter of 3 mm, the number of which varies according to the size of the structure. They can be 4 to 6 in number. Their application is done on the matrix housings and on the delimiting edges between the connector and the artificial teeth area, in the case of maxillary work and on the matrix housings, on the wax grids and on the main connector in the case of maxillary work mandibular.

b. Then a solidifying rod of the main channels is applied, made of profiled wax with a diameter of 3 mm that joins four, five or six rods in a radial shape, rods that will represent the secondary casting channels.

c. The part is detached and the casting channels will be solidified on the cone of the casting conformer. The positioning of the model will be chosen so that it is at approximately equal distances from the walls of the metal ring. After that, the metal ring lined with special wrapping paper is inserted on the conformer sleeve at the optimal height from the highest surface of the model.

The fifth stage is the tilting packaging technique. After gluing the mock-up to the casting cone, a thin start of de-stressed liquid is sprayed and the kneaded packing mass is poured into the vacuum, positioning the conformer on the vibrating table.

The molding of the packaging mass is done by the inclined technique. This procedure involves tilting the conformer when pouring the packing mass to avoid trapping air under the dome of the mold, given the position of the main domed connector relative to the mold filling direction.

After the packaging process is finished, the pattern is left for one hour for 1 socket and then it will be inserted for 60 to 90 minutes in the preheating furnace, and heated to the temperature of about 950 degrees, for the operation of casting 3 Cr-Co alloy.

The sixth stage describes the adaptation procedure by finishing and settling the metals. 5 Direct layout has the advantage of copying fidelity and precision. Thus, the casting result must be very precise. If the packaging has been done correctly and if the preheating times and temperature of the mold have been respected, the cast does not need a thorough adjustment. Simple finishing, which is nothing more than polishing and removing 9 burrs from the internal surfaces, makes the skeleton almost completely inserted, the rest of the fitting being done by lightly tapping the structures into the insertion shaft with a 11 100-gauge hammer grams. This ultimate adaptation produces a settling of metals with outstanding results on retention, closures and stability of the joined parts. This retention, 13 obtained by settling, will slightly diminish its action in the ceramic firing process, respectively by removing oxides and polishing the metallic components of the fixed part, the final result being 15 an optimal retention.

After adaptation, the metal structure is brought to the limits of the drawing, after which it is processed and finished with milling cutters, polypans and specific discs, based on classic operations, known in themselves. 19

The process of creating skeletal works, by direct modeling with acrylic resin, is applicable for the creation of mobile metal structures, both maxillary and mandibular.

Claims (1)

Procedure for making mobile metal structures, within the framework of skeletal prosthetic works, which involves the stage of making the functional working model from extra-hard plaster and attaching the Teflon matrices to the metal patrices, followed by a first stage of preparing the model for layout, a deretentivization of the surfaces in the area of the matrices, the gingival areas of the opposing arms and intraculis, followed by the application of a layer of foiling wax as a support for the resin and finally the planing operation of the sensitive surfaces of the prosthetic field; a step of making the main connector; a stage of preparation for packaging which involves attaching a number of 4 to 6 main molding channels from the profiled wax, applying a rod to solidify the main channels, which joins with four, five or six rods in radial shape, which will represent the secondary casting channels, positioning the model at approximately equal distances from the walls of the metal ring, detaching the part, solidifying the casting channels on the cone of the casting conformer, inserting the metal ring on the sleeve of the conformer at the optimal height; the inclined packaging technique stage, i.e. after gluing the model to the casting cone, pouring the packaging mass through the inclined technique, and after the pattern has been left for an hour to set, it is inserted for 60 to 90 minutes in the oven of preheating, the temperature rising up to about 950 degrees, for the operation of casting the Cr-Co alloy; the last stage consisting in adapting the structures by finishing and settling the metals, respectively polishing and removing burrs from the internal surfaces followed by a light hitting of the structures, in the insertion axis, with a 100 gram hammer, after adaptation the metal structure being brought to the limits of the drawing, after which it is processed and finished with milling cutters, polypants and specific discs, based on classic operations, known in themselves, characterized by the fact that, after preparing the model for layout, the acrylic resin matrix casings are made by brushing and modeling them within the limits of the existing spaces and highlighted in the articulator, the direct layout with acrylic resin, being followed by the stage of making the main connector, which is done in several steps, namely the insulation with paraffin oil, the application of acrylic resin by brushing to make the rigid support of the model, making an additional reinforcement with wax, applying the profiled wax over the rigid resin support, modeling the borders between the application areas of physiognomic materials and the metal structure of the connector, and as the last step of the modeling, the wax grid is attached.