Veneering with ceramic masses of single tooth prosthetic restorations in lateral areas (Part II)

Introduction

As mentioned in the first part of this material, single tooth prosthetic restorations are small-sized restorations with high accuracy, made with the help of the dental laboratory, in order to restore the morphology, physiognomy and functionality of a tooth or a por­tion of a tooth, as well as to restore its position on the dental arch. These prosthetic parts are made of metal alloys, polymers or ceramic masses^(1-3). By choosing the best therapeutic option, but also taking into account the level of implantation and the integrity of the dental abutment, the duration and existence of single tooth prosthetic restorations are conditioned by the previously mentioned aspects^(1-5). Once a tooth suffers from a structural defect, oral health is threatened because the defect cannot regenerate automatically. Therefore, fixed prosthetic restorations are necessary to restore a tooth, or to replace one or more missing natural teeth^(1-5).

General data

Returning to metal-ceramic full coverage crowns, these are completely esthetic single tooth prosthetic restorations, which are mainly used due to both the physiognomic component that offers a special esthetic as close to natural as possible, and the metal component responsible for resistance and hardness, which serves as ceramic mass support. The two main components make metal-ceramic prosthetic restorations quite widely used and popular among both dental practitioners (dentists and dental technicians) and patients^(1-3).

Next, a series of extremely interesting technological aspects will be presented, regarding the manufacturing of metal-ceramic prosthetic restorations in the lateral areas (maxillary and mandibular), by veneering them with Ivoclar Vivadent ceramic masses.

Case presentations

Case 1

A 37-year-old male patient presented to the dental office due to a coronal fracture at the level of the maxillary first premolar in first quadrant (1.4). After the clinical examination, it was found that a large-scale coronal obturation had been performed, in the past, at the premolar level, due to a penetrating caries that also required an endodontic treatment, which resulted in the fracture of the tooth at the occlusal level. Thus, the dentist, in agreement with the patient, opted for the prosthetic rehabilitation of 1.4 with the help of a full coverage metal-ceramic crown, due to its very good esthetic properties. Being a visible tooth in the smile, the patient accepted the treatment option, given that he already had another tooth restored by the same procedure, of which he was very satisfied with its resistance and color.

The dental abutment was prepared by grinding in the dental office. The functional impression, as well as that of the antagonistic arch, was made using condensation silicone materials in a double consistency: putty and light body. Occlusal record was performed with a bite registration material. The two impressions were washed under running tap water for 15 seconds, after which they were decontaminated by immersion in chemicals with antimicrobial potential, following the manufacturers’ recommended instructions.
 

After washing, disinfecting and drying the prints, the functional sectional model was created, using the Pinax Pro system (Roko Dental Systems). The functional model was cast from type IV dental stone, trimmed and prepared for technical stages of obtaining metal-ceramic restorations. The antagonist model was cast using also type IV dental stone.

The resulting dental abutment had slight irregularities, which were covered with a superficial layer of wax to cancel the retentive effect, after which the spacer was applied to ensure the stability and space required for the luting cement. After applying the spacer, the dental abutment was isolated and the wax pattern was made, which represented the future metal structure of the metal-ceramic crown.

After the wax pattern has been created, using a spruing wax, it was attached to crucible former. A surface tension reducer substance was applied on the wax, and the investment material was applied gradually inside de casting ring to avoid the appearance of voids. The investment material setting took place in about 35 minutes, after which the mould was heated in a special oven at a temperature of 950ºC for 40-45 minutes for melting and eliminating the wax. Using an automatic casting machine, the dental alloy was poured into the heated mould. After cooling, the casted piece was de-vested, sand blasted. The metallic structure was removed from the metal sprue and processed. The metal coping was adapted on the functional model using diamond burs. To avoid cracks in the future ceramic veneer, the metal structure was polished in the first phase. After the metal coping was processed and adapted both on the maxillary functional model and in the patient’s oral cavity, it was sandblasted and finally introduced into the special oven for the oxidation stage.
 

Before starting the layering process of IPS InLine Ivoclar Vivadent ceramic masses, the opaque layers were applied so that the color of the metal does not show through. Afterwards, the ceramic masses that will be layered in this case were prepared. For a better highlighting of the deposited layers, pigments specific to ceramic masses were used:

• green – deep dentin;
• red – dentine;
• pink – transparent incisal;
• yellow – opal effect 3;
• purple – purple opal effect;
• orange – transparent brown-grey.

The next stage was represented by layering the ceramic masses. Over the opaque layer, deep dentin was applied by brushing. The dentin was deposited later, then the enamel was layered very carefully, without a sharp demarcation between the dentin and the enamel, smoothly disappearing on the vestibular face. Modeling was done in excess, due to the contraction of the ceramic mass after firing. Afterwards, the color effects were applied. Opal effect violet was applied occlusally to re­duce brightness, and transparent brown-grey was applied in the occlusal third to determine good transparency of the area. Once the modeling has been done by layering the ceramic masses respecting the morphological criteria, the crown was removed from the functional model, and on the proximal faces where there was no accessibility, dentine was applied for completion. The prosthetic restoration was then positioned on the pin and placed in the furnace for the first firing.
 

After the first firing, small imperfections and irregularities could be observed at the level of the metal-ceramic prosthetic restoration, due to the contraction of the ceramic mass. Thus, the prosthetic piece was retouched, making the second burn, the correction burn.
 

With the prosthetic restoration on the functional model, the proximal contacts were checked, and in the areas where the prosthetic part did not adapt, it was polished with the help of diamond burs. After checking the occlusal relationship and the crown try-in, the restoration was prepared for the application of the glaze layer and the ceramic masses make-up. The tooth crown was individualized with a brown color, as were the occlusal grooves. Thus, the appearance of the crown was achieved as close to natural as possible. The prosthetic piece was then positioned on the pin and placed in the furnace for the final firing, namely the glaze firing, resulting in the final metal-ceramic prosthetic restoration.

Case 2

A 65-year-old male patient presented to the dental office due to an old prosthetic restoration at the level of the lower first premolar in quadrant 4 (4.4), which no longer presented a good esthetics and functionality. The patient suffered from bruxism, this can also be seen very well on the study models. Thus, the dentist, together with the patient, decided to replace the old prosthetic restoration with a metal-ceramic crown. The functional impression as well as the impression of the antagonistic arch were made in standard impression trays with dual mixture condensation silicone materials: putty and light body. Occlusal record was performed with a bite registration material. The impressions were washed under running tap water for 15 seconds, after which they were decontaminated by immersion in chemicals with antimicrobial potential, following the manufacturers’ recommended instructions. As in the previous case, the washing, disinfection and drying of the impressions were followed by obtaining the sectional functional model, using the Pinax Pro system (Roko Dental Systems). The functional model was cast using type IV dental stone. For the antagonist model, type III dental stone was used.
 

The die was removed from the model and ditched, to highlight the margin of the preparation. Subsequently, a layer of spacer was applied on the surface of the die to create a space for the luting material. The wax pattern of the coping was manufactured and prepared for investing.
 

The metal component was cast using the Ni-Cr dental alloy, which is a specific alloy for metal-ceramic restorations. After cooling, the casting was de-vested, the sprue was removed, the coping was processed with diamond burs and oxidized before applying the layers of opaque. The two layers of opaque were applied with a maximum thickness of 0.1 mm to block the color of dental alloy.
 

After all the opaque layers have been applied and fired, the layering of IPS InLine Ivoclar Vivadent ceramic masses followed. The application of the deep dentine layer was the first step and was done by brushing, later the other ceramic masses and the effects were also applied by brushing, in order to achieve the desired result. Next, several grooves were made with the help of a dry brush, so that the interpenetration of the dentin-enamel layers was uniform. The final modeling in the ceramic paste aimed at achieving the details of shape and volume, the appearance of the relief being slightly abraded, according to the remaining natural teeth present on the arch.
 

Finally, the glaze layer and that of the ceramic make-up masses were applied to the surface of the prosthetic restoration. Afterwards, the mixed metal-ceramic crown was sent to the dental office, to be cemented in the patient’s oral cavity.
 

Discussion

Metal-ceramic restorations restore both the resistance structure of the affected teeth through the metal component and the physiognomic one through the ceramic masses. The widespread use of these materials has led to lower production costs and, at the same time, to a reduction in the use of other esthetic materials such as acrylate or composite resins^(4,5). In addition to the volumetric changes that occur with the start of use, composite resins, but especially acrylic resins, undergo important color changes, their surface being slightly porous regardless of the finishing process used^(6-9).

At the same time, completely covering the crowns with ceramic masses reduces the working time in the technical stages, and facilitates the work of the dental technicians^(10,11). Partially physiognomic crowns, where only the vestibular face is covered with ceramic masses, require an additional effort for the dental technician, as it is necessary to process the metal component after the firing stages of a small prosthetic piece^(12-14).

The combination of the sectional model, ceramic masses on metal structure and the wide palette of colors available for the esthetic component are to the advantage of the doctor, the dental technician, but especially of the final beneficiary, namely the patient. It thus benefits from a high-quality prosthetic treatment with a predictable result that can be applied in different clinical situations^(15,16).

The emergence of new technologies, the digital flows of making prosthetic restorations, will at some point replace the current technologies, considered classic, but that moment is not so close. The reluctance to new technologies, partially justified, will make the modeling of ceramic masses continue to be used, turning this job into an art^(17,18).

Conclusions

As we have already mentioned in the first part of this material, metal-ceramic prosthetic restorations are frequently used as a method of prosthetic rehabilitation, treatment in the case of teeth with dental defects, fractures, situations of exaggerated abrasion or color defects. Concretely, the role of these metal-ceramic prosthetic restorations is to improve the physiognomic appearance and restore the functional relationships.

The purpose of the presented material was to expose the fact that, by using IPS InLine Ivoclar Vivadent ceramic masses, special results are obtained in the manufacturing of the physiognomic component of metal-ceramic crowns, the working technique presenting numerous advantages. These ceramic masses are high-quality materials, the expectations of patients, dentists and dental technicians being met from all points of view.

Acknowledgement: Viorel Ştefan Perieanu and Oana- Elena Amza are corresponding authors (Viorel Ştefan Perieanu: viorelperieanu@yahoo.com; Oana-Elena Amza: oana.amza@umfcd.ro); Valentin-Dănuţ Albu and Mihai Burlibaşa have equally contribution with the first author.

Autori pentru corespondenţă: Viorel Ştefan Perieanu E-mail: viorelperieanu@yahoo.com; Oana-Elena Amza E-mail: oana.amza@umfcd.ro

CONFLICT OF INTEREST: none declared.

FINANCIAL SUPPORT: none declared.

This work is permanently accessible online free of charge and published under the CC-BY.